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Single-oxidant slurries are prevalently utilized in chemical and mechanical polishing (CMP) of 4H-SiC crystal. Nevertheless, it is a challenge to achieve a high material removal rate (MRR) and surface quality using single oxidant slurries to meet the needs of global planarization and damage-free nanoscale surface processing of SiC wafers. To solve this challenge, a novel method is proposed for SiC CMP processing using the double oxidant slurry. This slurry mainly consists of alumina (Al 2 O 3 ) abrasive particles, potassium permanganate (KMnO 4 ), potassium persulfate (K 2 S 2 O 8 ), and deionized water. Post CMP, MRR is 1045 nm/h calculated by scratch method, and surface roughness Sa is 0.33 nm measured by 3D optical surface morphometer, with the measurement area of 868 μm × 868 μm. Both the MRR and Sa are far better than those under the single oxidant slurry condition. CMP mechanism with double-oxidant slurry conditions is elucidated by energy dispersive spectrometer and X-ray photoelectron spectrometer. Initially, the Si-C bond on the SiC wafer surface was oxidized by KMnO 4 , then MnO 2 as the reduction product of KMnO 4 can also catalyze the S 2 O 8 to further oxidize SiC wafer surface, and eventually the oxidation layers were removed by mechanical action of nano-Al 2- to further oxidize SiC wafer surface, and eventually the oxidation layers were removed by mechanical action of nano-Al 2 O 3 abrasive particles during CMP processing. These findings offer a pioneering approach and novel perspectives to achieve a higher MRR of 4H-SiC CMP, with potential implications for the application in high-performance SiC devices.

The present contribution reports on a study aiming to find the most suitable rubbing method for filling arrays of separated and interconnected micromachined pockets with individual microspheres on rigid, uncoated silicon substrates without breaking the particles or damaging the substrate. The explored dry rubbing methods generally yielded unsatisfactory results, marked by very large percentages of empty pockets and misplaced particles. On the other hand, the combination of wet rubbing with a patterned rubbing tool provided excellent results (typically <1% of empty pockets and <5% of misplaced particles). The wet method also did not leave any damage marks on the silicon substrate or the particles. When the pockets were aligned in linear grooves, markedly the best results were obtained when the ridge pattern of the rubbing tool was moved under a 45° angle with respect to the direction of the grooves. The method was tested for both silica and polystyrene particles. The proposed assembly method can be used in the production of medical devices, antireflective coatings, and microfluidic devices with applications in chemical analysis and/or catalysis.

Graphene's remarkable attributes make it suitable for application to biosensors for biomolecular recognition. Specific and precise target detection is realized by designing robust methods for immobilization of probe molecules, such as oligonucleotides, antibodies, receptors, and sugar chains, to a device surface. In this research, we developed a chemical modification method with a plasma treatment of amino groups on natural defects of graphene, which is compatible with a wafer-scalable semiconductor process, to prevent deterioration of the carrier mobility. The plasma treatment was optimized in terms of the efficiency of the amino radical generation, length of the mean free path, and reaction energy on graphene. The density of the modified amino groups on graphene was approximately 0.065 groups/nm 2 , and the change in the Δ I d / Δ V g characteristic of the graphene field-effect transistor (FET) was negligible. DNA probes were then attached to the amino groups on the graphene FET. The target complementary DNA was detected at 1 nM after hybridization using the graphene FET devices. The plasma-assisted modification of the amino groups on the graphene surface was developed for immobilization of the DNA probes, and hybridization with the target DNA was demonstrated without deterioration of the carrier mobility.

Self-assembly at the air/water interface (AWI) has proven to be an efficient strategy for fabricating two-dimensional (2D) colloidal monolayers, which was widely used as the template for nanosphere lithography in nanophononics, optofluidics, and solar cell studies. However, the monolayers fabricated at the AWI usually suffer from a small domain area and quasi-double layer structure caused by submerged particles. To overcome this, we proposed an improved protocol to prepare 2D colloidal monolayers free of overlapping nanospheres at the AWI. Utilizing the stable suspension infusion to the water surface, a convex meniscus, whose height is related to viscous force, was formed adjoining the three-phase boundary. As a result of the resistance of the convex meniscus, the polystyrene nanospheres in the initial suspension directly self-assembled into a preliminary monolayer, which proved effective in preventing nanospheres' sinking and increasing the colloidal crystal domain size. An optimal parameter for transferring the monolayer was also developed based on the numerical simulation results. Finally, a wafer-scale monolayer, covered with less than one nanosphere per 100 μm × 100 μm area, was achieved on the desired substrate with an average domain size attaining centimeter scale. The high-quality 2D colloidal crystal may further promote the application of nanosphere lithography, especially in the fields that require a defect-free template.

Amino-terminated silane compound modification was wet-processed on a silicon wafer using four different solvents to investigate the property of the self-assembled monolayer (SAM) and its influence on the adhesion of electroless deposited nickel-phosphorus (Ni-P) films. Analyzed by various tools including dynamic light scattering, the atomic force microscope, X-ray photoelectron spectroscopy, inductively coupled plasma with mass spectroscopy, a proper link between the processing solvent and SAM quality is established. It is found that at least the chemical compatibility, the polarity, and the acidity of solvents can affect the final morphology of the resultant SAM. Unlike toluene and ethanol that are most frequently chosen in literature, we conclude that isopropyl alcohol (IPA) is a superior solvent for amino-terminated silane compounds. Owing to the good SAM quality formed in IPA, the adhesion of electroless deposited Ni-P films is largely strengthened, even as high as the bulk strength of silicon wafers.

The structure evolution of P3HT thin films on Si wafer and PVPh covered Si wafer during heating, thermal annealing, and melt recrystallization processes has been studied in detail using X-ray analysis techniques. The effect of substrate on the crystallization behavior and interface structure of P3HT films was explored. For the P3HT films deposited on the Si substrate, it was found that the stability of P3HT crystals is orientation dependent. The crystals oriented with b-axis normal to the substrate, that is, a face-on molecular orientation, are less stable than those with the a-axis arranged normal to the substrate (side-on molecular orientation). Thermal annealing temperature plays an important role in the molecular structure of P3HT including crystal structure, film thickness, and surface roughness. After annealing at relatively high temperature, new crystals form during the cooling process accompanied by the shrinking of a-axis. Moreover, the melt recrystallization favors the formation of more stable P3HT crystals with side-on molecular orientation. The PVPh substrate does not affect the crystallization behavior of solution cast P3HT significantly but inhibits the formation of P3HT crystal with face-on molecular orientation. However, the interfacial morphology of P3HT and PVPh changes by annealing at elevated temperature. The P3HT/PVPh interface changes from a sharply defined one into a diffused one at around 160 °C. The PVPh sublayer inhibits the melt recrystallization of P3HT to some extent, leading to a slight expansion of the a-axis.

We developed a simple and general approach for constructing a wafer-scale monolayer, close-packed polystyrene (PS), and SiO2 sphere arrays, namely colloidal crystals, which have significant potential in various applications. The method combines slope self-assembly and thermal treatment to achieve large-area and high-quality colloidal crystal with a proper slant angle (θ) and latex concentration (volume fraction, φ). The dependence of the structures of colloidal crystals on a dispersion system was also investigated. Moreover, a theoretical analysis of the slope self-assembly method was proposed. In addition, we applied the method to assemble PS spheres on different kinds of substrates, which indicates that the method is a versatile and reliable way to fabricate monolayer colloidal crystals.

A photoresponsive molecularly imprinted system was prepared on a silicon wafer substrate surface via the host-guest complex of grafted 4-(3-triethoxysilylpropyiureido)azobenzene (TSUA) and mono-6-deoxy-6-((p-chlorosulfonyl)-benzoic acid)-β-cyclodextrin (CBA-β-CD), and the acid-base pair interactions/hydrogen bonds between CBA-β-CD and the template molecules, including theophylline (TPE) and 4-hydroxybenzoic acid (4-HA). A molecular imprinting cycle "imprinting → extracting → uptaking → shuffling" was also defined in the study, the processes of uptaking and shuffling were investigated in detail by equilibrium binding experiments, and the Langmuir adsorption isotherm and Scatchard equation were used to evaluate the binding affinity and the theoretical binding sites of the molecularly imprinted (MIS), nonimprinted (NIS), and pure (PS) silicon wafer substrates. Compared with the NISs and PSs, the MISs showed a significantly higher adsorption capacity for the template molecules. More importantly, the MISs showed a reimprinted ability; after the process of shuffling, the molecularly imprinted systems on the substrate surface were destroyed, and new imprinted systems could be fabricated for the recognition of other template molecules after washing the substrates under irradiation at 450 nm. Moreover, the selective adsorption for the MISs was investigated, which indicated that the MISs showed specific affinity to the template molecules (TPE or 4-HA).

A device for the capture and recollection of live target cells is described. The platform was a silicon (Si) wafer modified with an anti-HEL antibody (anti-HEL-IgG, HEL = hen egg lysozyme) through a photocleavable 3-amino-3-(2-nitrophenyl)propionic acid (ANP) linker. The modification processes of the Si wafer surface were monitored by Fourier transform infrared spectroscopy-attenuated total reflection (FTIR-ATR) and fast-scanning atomic force microscopy (FS-AFM). The attachment of IgG and its release reaction on the Si surface via the photochemical cleavage of the ANP linker were observed directly by FS-AFM. The results of an enzyme-linked immunosorbent assay (ELISA) indicated that the photorelease of the complex of anti-HEL-IgG with the secondary antibody-alkaline phosphatase hybrid (secondary IgG-AP) from the Si surface occurs with minimum damage. Furthermore, it was possible to collect SP2/O cells selectively that express HEL on their cell membranes (SP2/O-HEL) on the Si wafer device. Photochemical cleavage of the ANP linker facilitated the effective release of living SP2/O cells whose viability was verified by staining experiments using tripan blue. Moreover, it was possible to reculture the recovered cells. This methodology represents an effective strategy for isolating intact target cells in the biological and medicinal sciences and related fields.

Tetraethylorthosilicate (TEOS) is added to a pure-silica-zeolite MEL nanoparticle suspension and the mixture is subsequently used for preparing spin-on low-dielectric constant (low-k) films. The films are then characterized by ellipsometric porosimetry, transmission electron microscopy (TEM), and nanoindentation. Investigation into the film microstructure indicates that the addition of TEOS significantly increases the fraction of the crystalline domains, decreases the inter-crystal mesopore size, and narrows the pore size distribution. Films with 12% TEOS loading have a mean pore size distribution centered at 3.5 nm (diameter) with a full width at half maximum (fwhm) of 0.8 nm, while those with no TEOS have a distribution at 11.1 nm and fwhm of 7.9 nm. At 12% TEOS loading, the reduced modulus and hardness are 11.0 and 1.12 GPa, respectively; without TEOS, the values are 6.4 and 0.57 GPa.

The aggregation of ionic liquid-type imidazolium gemini surfactant [C(12)-4-C(12)im]Br(2) on silicon wafer, which is compared with its monomer [C(12)mim]Br, have been studied. AFM morphology images and contact angle measurements suggest that the aggregations of [C(12)-4-C(12)im]Br(2) and [C(12)mim]Br on silicon wafer follow different mechanisms. Below the critical surface aggregation concentrations (CSAC), both surfactant molecules are adsorbed with their hydrophobic tails facing the air. But above the CSAC, [C(12)-4-C(12)im]Br(2) molecules finally form a bilayer structure with hydrophilic head groups facing the air, whereas [C(12)mim]Br molecules form a multilayer structure, and with increasing its concentration, the layer numbers increase with the hydrophobic chains and hydrophilic head groups facing the air by turns. Besides, the watery wettability of [C(12)-4-C(12)im]Br(2)-treated silica surface is lower than that of [C(12)mim]Br at the concentration of 5.0 cmc, and the infrared spectroscopy suggests that the poorer watery wettability of [C(12)-4-C(12)im]Br(2) may be relative to the less-ordered packing of methylene chains inside the aggregate. These different aggregation behaviors for the two surfactants ascribe to the different molecular structures and electrostatic interactions. This work would have certain theoretical guidance meaning on the modification of solid surface.

A simple approach to wafer-scale self-cleaning antireflective hierarchical silicon structures is demonstrated. By employing the KOH etching and silver catalytic etching, pyramidal hierarchical structures were generated on the crystalline silicon wafer, which exhibit strong antireflection and superhydrophobic properties after fluorination. Furthermore, a flexible superhydrophobic substrate was fabricated by transferring the hierarchical Si structure to the NOA 63 film with UV-assisted imprint lithography. This method is of potential application in optical, optoelectronic, and wettability control devices.

The wettability of thin poly(methyl methacrylate) (PMMA) films on a silicon wafer with a native oxide layer exposed to solvent vapors is dependent on the solvent properties. In the nonsolvent vapor, the film spread on the substrate with some protrusions generated on the film surface. In the good solvent vapor, dewetting happened. A new interface formed between the anchored PMMA chains and the swollen upper part of the film. Entropy effects caused the upper movable chains to dewet on the anchored chains. The rim instability depended on the surface tension of solvent (i.e., the finger was generated in acetone vapor (gamma(acetone) = 24 mN/m), not in dioxane vapor (gamma(dioxane) = 33 mN/m)). The spacing (lambda) that grew as an exponential function of film thickness h scaled as approximately h(1.31), whereas the mean size (D) of the resulting droplets grew linearly with h.

Surface-tethered oppositely charged weak polyelectrolyte block copolymer brushes composed of poly(2-vinyl pyridine) (P2VP) and poly(acrylic acid) (PAA) were grown from the Si wafer by atom-transfer radical polymerization. The P2VP-b-PAA brushes were prepared through hydrolysis of the second PtBA block to the corresponding acrylic acid. The P2VP-b-PAA brushes with different PAA block length were obtained. The P2VP-b-PAA brushes revealed a unique reversible wetting behavior with pH. The difference between the solubility parameters for P2VP and PAA, the changes of surface chemical composition and surface roughness, and the reversible wetting behavior illustrated that the surface rearrangement occurred during treatment of the P2VP-b-PAA brushes by aqueous solution with different pH value. The reversible properties of the P2VP-b-PAA brushes can be used to regulate the adsorption of the sulfonated PS nanoparticles.

We report the capture of nanosized oil droplets using a hydrophilic aldehyde-functional polymer brush. The brush was obtained via aqueous ARGET ATRP of a cis -diol-functional methacrylic monomer from a planar silicon wafer. This precursor was then selectively oxidized using an aqueous solution of NaIO 4 to introduce aldehyde groups. The oil droplets were prepared by using excess sterically stabilized diblock copolymer nanoparticles to prepare a relatively coarse squalane-in-water Pickering emulsion (mean droplet diameter = 20 μm). This precursor was then further processed via high-pressure microfluidization to produce ∼200 nm squalane droplets. We demonstrate that adsorption of these nanosized oil droplets involves acetal bond formation between the cis -diol groups located on the steric stabilizer chains and the aldehyde groups on the brush. This interaction occurs under relatively mild conditions and can be tuned by adjusting the solution pH. Hence this is a useful model system for understanding oil droplet interactions with soft surfaces.

Surface texturing of manufactured products tailors their properties, such as friction, adhesion, biocompatibility, or fluid interactions. However, advancements in this area are largely the result of trial-and-effort testing and generally lack a science-guided framework for determining the surface topography that will optimize performance. The present investigation explores grayscale electron-beam lithography as a means to create multiscale surface patterns to control surface performance. Here, we created and characterized a set of surface textures on a silicon wafer; the textures were superpositions of sine waves of varying wavelengths and amplitudes. First, the multiscale topography of the patterned surface was characterized, using profilometry and atomic force microscopy, to understand its fidelity to the designed-in pattern. The results of this analysis demonstrated how grayscale lithography accurately controlled the lateral size of features but was less precise on the vertical height of the surface, and also introduced inherent roughness below the scale of patterning. Second, a micromechanical tester was used to characterize the adhesion of the surfaces with large-scale polished silicon spheres. The results showed that adhesion could be tailored, with significant contribution from all of the designed-in length scales of topography. The strength of adhesion did not correlate with conventional roughness parameters but could be accurately modeled using simple numerical integration. Taken together, this investigation demonstrates the promise and challenges of grayscale e-beam lithography with multiscale patterns as a method for the tailoring of surface performance.

In the chemical-mechanical polishing (CMP) process, the abrasive particles in the polishing slurry tend to agglomerate easily and crystallize on the equipment surfaces during recycling, which can lead to poor wafer processing quality and additional tedious cleaning work. To overcome this issue, a simple and cost-effective self-cleaning surface preparation method has been developed. In this study, elastic and stretchable hydroxyl polydimethylsiloxane (PDMS-OH) was selected as the functional material, it was chelated with pentaerythritol tetra(3-mercapto propionate), and then 2-(perfluorooctyl)ethyl methacrylate was further grafted in situ to the polymer chains via a photoinduced thiol-ene click reaction. Hydrophobically modified micronanoscale silica particles were used to construct robust hierarchical micronanostructures while imparting stable mechanical wear resistance to the coating. The resulting superamphiphobic film exhibits the "lotus effect" and exceptional self-cleaning ability, repelling liquids such as water, hexadecane, and polishing slurry. Furthermore, the coating demonstrated outstanding chemical resistance and antifouling ability. Thus, it provides a feasible solution for preventing abrasive crystallization at critical locations where the polishing slurry flows in the CMP equipment. This work contributes to the enhanced application of superrepellent coatings in the CMP stage of semiconductor material processing.

Sterically stabilized diblock copolymer nanoparticles with a well-defined spherical morphology and tunable diameter were prepared by RAFT aqueous emulsion polymerization of benzyl methacrylate at 70 °C. The steric stabilizer precursor used for these syntheses contained pendent cis -diol groups, which means that such nanoparticles can react with a suitable aldehyde-functional surface via acetal bond formation. This principle is examined herein by growing an aldehyde-functionalized polymer brush from a planar silicon wafer and studying the extent of nanoparticle adsorption onto this model substrate from aqueous solution at 25 °C using a quartz crystal microbalance (QCM). The adsorbed amount, Γ, depends on both the nanoparticle diameter and the solution pH, with minimal adsorption observed at pH 7 or 10 and substantial adsorption achieved at pH 4. Variable-temperature QCM studies provide strong evidence for chemical adsorption, while scanning electron microscopy images recorded for the nanoparticle-coated brush surface after drying indicate mean surface coverages of up to 62%. This fundamental study extends our understanding of the chemical adsorption of nanoparticles on soft substrates.

We aimed to determine if audible sounds could change the forces acting between charged surfaces in water and their electric double layers (EDLs). This was achieved by using an atomic force microscope to measure force-distance curves between a microsized silica particle attached to a cantilever (probe) and a silicon wafer in water in the absence and presence of sound. Sound decreased the repulsive forces acting between the probe and silicon wafer, where the range and magnitude of the forces decreased with an increase in the sound frequency from 300 to 15000 Hz. The decrease in the force range was explained by a decrease in the EDL thickness. This result was explained by (1) the shrinkage of the EDL by a high-pressure region of the sound wave, where an increased sound frequency caused the number of high-pressure regions that passed between the probe and the substrate to increase and (2) the inability of the EDL to fully re-expand to its original thickness during the time that a low-pressure region of the sound wave was applied. The decrease in the force magnitude with a sound frequency increase was explained by the increased screening of charged surfaces that accompanies a decrease in the EDL thickness. An increase in the force measurement speed caused the sound waves to reduce the repulsive forces less. A faster speed decreased the time to measure a force curve, which reduced the number of high-pressure regions of the sound wave to pass through the water between the probe and the substrate. This reduced the number of times that the EDL was compressed by the sound wave.

The physico-chemical properties of native oxide layers, spontaneously forming on crystalline Si wafers in air, can be strictly correlated to the dopant type and doping level. In particular, our investigations focused on oxide layers formed upon air exposure in a clean room after Si wafer production, with dopant concentration levels from ≈10 13 to ≈10 19 cm -3 . In order to determine these correlations, we studied the surface, the oxide bulk, and its interface with Si. The surface was investigated using the contact angle, thermal desorption, and atomic force microscopy measurements which provided information on surface energy, cleanliness, and morphology, respectively. Thickness was measured with ellipsometry and chemical composition with X-ray photoemission spectroscopy. Electrostatic charges within the oxide layer and at the Si interface were studied with Kelvin probe microscopy. Some properties such as thickness, showed an abrupt change, while others, including silanol concentration and Si intermediate-oxidation states, presented maxima at a critical doping concentration of ≈2.1 × 10 15 cm -3 . Additionally, two electrostatic contributions were found to originate from silanols present on the surface and the net charge distributed within the oxide layer. Lastly, surface roughness was also found to depend upon dopant concentration, showing a minimum at the same critical dopant concentration. These findings were reproduced for oxide layers regrown in a clean room after chemical etching of the native ones.

This paper provides a numerical analysis of the behavior of the ion boundary layer formed during proton exchange. Thermal dissociation of benzoic acid melt molecules leads to the formation of benzoate ions and hydrogen ions. The latter can be absorbed by a lithium niobate wafer, with subsequent diffusion of lithium ions in the acid. The mathematical model proposed in the article implies that it is possible to use continuous media approximation to describe this phenomenon. The statement of the current problem includes both diffusion and electrostatic mechanisms of mass transfer and the recombination mechanism of ion interaction. The numerical scheme, based on a two-field method, has shown a steady-state formation, characterized by exponential-like profiles of concentration in the presence of an induced nonuniform electric field. It is important to note that the net charge of the system remains zero. The results of numerical simulation have demonstrated the formation of a boundary layer of benzoate ions. At the same time, nonuniformities that appear in the layer do not create instability that breaks mechanical equilibrium, and they do not lead to a high-scale concentration convection.

Sessile drop evaporation and condensation on slippery liquid-infused porous surfaces (SLIPS) is crucial for many applications. However, its modeling is complex since the infused lubricant forms a wetting ridge around the drop close to the contact line, which partially blocks the free surface area and decreases the drop evaporation rate. Although a good model was available after 2015, the effects of initial lubricant heights ( h oil ) i above the pattern, and the corresponding initial ridge heights ( h , lubricant viscosity, and solid pattern type were not well studied. This work fills this gap where water drop evaporations from SLIPS, which are obtained by infusing silicone oils (20 and 350 cSt) onto hydrophobized Si wafer micropatterns having both cylindrical and square prism pillars, are investigated under constant relative humidity and temperature conditions. With the increase of ( r ) i , lubricant viscosity, and solid pattern type were not well studied. This work fills this gap where water drop evaporations from SLIPS, which are obtained by infusing silicone oils (20 and 350 cSt) onto hydrophobized Si wafer micropatterns having both cylindrical and square prism pillars, are investigated under constant relative humidity and temperature conditions. With the increase of ( h oil ) i , the corresponding ( h r ) i increased almost linearly on lower parts of the drops for all SLIPS samples, resulting in slower drop evaporation rates. A novel diffusion-limited evaporation equation from SLIPS is derived depending on the available free liquid-air interfacial area, A LV , which represents the unblocked part of the total drop surface. The calculation of the diffusion constant, D , of water vapor in air from (d A LV /d t ) values obtained by drop evaporation was successful up to a threshold value of ( h oil ) i = 8 μm within ±7%, and large deviations (13-27%) were obtained when ( h oil ) i > 8 μm, possibly due to the formation of thin silicone oil cloaking layers on drop surfaces, which partially blocked evaporation. The increase of infused silicone oil viscosity caused only a slight increase (12-17%) in drop lifetimes. The effects of the geometry and size of the pillars on the drop evaporation rates were minimal. These findings may help optimize the lubricant oil layer thickness and viscosity used for SLIPS to achieve low operational costs in the future.

We aimed to determine how surface roughness changes the effect of a liquid flow on the forces between two charged surfaces. This is because many applications require liquid to flow through charged confined areas and because all surfaces show a degree of roughness. We prepared films of different roughness by making mixed Langmuir films of silica nanoparticles (NPs) of two different diameters at air-100 mM NaCl aqueous interfaces and then by transferring and sintering these films to silicon wafers. Atomic force microscope (AFM) imaging showed that the film roughness decreased (1) with an NP diameter decrease and (2) an increased ratio of small NPs in a mixed film of small and larger NPs. This decrease was explained by a decreased NP aggregation in the film, due to the increased Brownian velocity that accompanies an NP diameter decrease. Force-separation curves were next measured with an AFM between a microsized silica particle (probe) and a smooth substrate (silicon wafer) or the rough NP films in 1 mM NaCl. In the absence of a liquid flow, the repulsive forces decreased with an increased substrate roughness. This reduction was explained by an increased difference between the real zero separation distance and apparent zero separation distance (the distance between the first point of mechanical contact between the probe and substrate) with an increased surface roughness. In the presence of a liquid flow, the repulsive forces decreased in the case of a smooth substrate. However, the repulsive forces were reduced less by a liquid flow for rough substrates. This result was explained by the difference in the effect of liquid flow on the diffuse layer for the smooth and rough surfaces. Surface roughness is postulated to modify the liquid flow trajectory near the surfaces and to cause ion concentration gradients near the surface. These factors are proposed to lessen the change in the diffuse layer brought about by a liquid flow. This would then reduce the change in the forces.

The design of hydrophobic surfaces requires a material which has a low solid surface tension and a simple fabrication process for anchoring and controlling the surface morphology. A generic method for the spontaneous formation of robust instability patterns is proposed through the hydrosilylation of a fluoroalkene bearing dangling chains, R f = C 6 F 13 (CH 2 ) 3 -, with a soft polymethylhydrosiloxane (PMHS) spin-coated gel polymer (0.8 μm thick) using Karstedt catalyst. These patterns were easily formed by an irreversible swelling reaction due to the attachment of a layer to various substrates. The buckling instability was created by two different approaches for a gel layer bound to a rigid silicon wafer substrate (A) and to a soft nonswelling silicone elastomer foundation (B). The observations of grafted R f -PMHS films in the swollen state by microscopy revealed two distinct permanent patterns on various substrates: dotlike of wavelength λ = 0.4-0.7 μm (A) or wrinkle of wavelength λ = 4-7 μm (B). The elastic moduli ratios of film/substrate were determined using PeakForce quantitative nanomechanical mapping. The characteristic wavelengths (λ) of the patterns for systems A and B were quantitatively estimated in relation to the thickness of the top layer. A diversity of wrinkle morphologies can be achieved by grafting different side chains on pristine PMHS films. The water contact angle (WCA) hysteresis of fluorinated chain ( R f ) was enhanced upon roughening the surfaces, giving highly hydrophobic surface properties for water with static/hysteresis WCAs of 136°/74° in the resulting wrinkle (B) and 119°/41° in the dotlike of lower roughness (A). The hydrophobic properties of grafted films on A with various mixtures of hexyl/fluoroalkyl chains were characterized by static CA: WCA 104-119°, ethylene glycol CA 80-96°, and n -hexadecane CA 17-61°. A very low surface energy of 15 mN/m for R f -PMHS was found on the smoother dotlike pattern.

A new methodology using nanoparticle projectile secondary ion mass spectrometry was developed to identify statistically significant co-localization of tagged proteins versus random aggregations at the nanoscale. The custom instrument was run in the unique event-by-event bombardment detection mode with 1040 keV Au 2800 individual projectiles each probing an area with a diameter of ∼20 nm. In a model experiment, antibodies tagged with fluorine, iodine, and bromine were attached on a silicon wafer in a 1:1:1 ratio. To determine whether the three different antibodies were homogeneously distributed at the nanoscale or if there were fluctuations due to the slightly different physical properties of the tags, a "co-localization factor" was introduced. It is shown for the first time that the differences in the hydrophobicity of the tags induced fluctuations, causing differential attachment of the tags at the nanoscale. When tags with the same physical and chemical properties were used, the analysis of co-localization factors shows that the attachment became random.8+ individual projectiles each probing an area with a diameter of ∼20 nm. In a model experiment, antibodies tagged with fluorine, iodine, and bromine were attached on a silicon wafer in a 1:1:1 ratio. To determine whether the three different antibodies were homogeneously distributed at the nanoscale or if there were fluctuations due to the slightly different physical properties of the tags, a "co-localization factor" was introduced. It is shown for the first time that the differences in the hydrophobicity of the tags induced fluctuations, causing differential attachment of the tags at the nanoscale. When tags with the same physical and chemical properties were used, the analysis of co-localization factors shows that the attachment became random.

Molecular mechanisms underlying the cononsolvency, a re-entrant coil-to-globule-to-coil conformational transition of polymer chains in mixtures of two good solvents, of poly[2-(methacryloyloxy)ethyl phosphorylcholine] (PMPC) in ethanol-water binary mixtures were complementarily investigated. This was accomplished by following a statistical mechanical model for competitive hydrogen bonding combined with the cooperative solvation concept as well as neutron reflectivity (NR) experiments employing contrast variation in the cononsolvents. The experimental re-entrant aggregation of the PMPC chains in ethanol-water mixed solvents, obtained on the basis of turbidity was accurately reproduced by theoretical calculations. The calculation proved the relatively strong cooperativity of ethanol and the preferential interaction of water, while the total coverage of solvents was the lowest at an ethanol volume fraction ( f ) of 0.90. At this level, the cononsolvency was the most significant, and the collapsed PMPC chains were solvated with more water than the bulk mixed solvent. The ethanol-water cononsolvency for the PMPC brushes on a planar silicon wafer was investigated by NR experiments, and the solvent composition involved in the collapsed PMPC brush was addressed according to the contrast variation study with mixed solvents of water, deuterium oxide, ethanol- ethanol ) of 0.90. At this level, the cononsolvency was the most significant, and the collapsed PMPC chains were solvated with more water than the bulk mixed solvent. The ethanol-water cononsolvency for the PMPC brushes on a planar silicon wafer was investigated by NR experiments, and the solvent composition involved in the collapsed PMPC brush was addressed according to the contrast variation study with mixed solvents of water, deuterium oxide, ethanol- d 5 , and ethanol- d 6 . The collapsed PMPC brushes at f ethanol = 0.90 contained more water than the bulk solvent. The preferential distribution of water in the collapsed PMPC brush was consistent with the simulation results. Therefore, the molecular mechanism for the cononsolvency of PMPC in ethanol-water mixed solvents based on competitive hydrogen bonding coupled with cooperative solvation was experimentally rationalized.

We present a simple and economically convenient method to fabricate nanopatterned ZnO films by imprinting lithography and use them for the layer alignment of liquid crystal (LC) displays. First, a one-dimensional nanopattern was obtained by laser interference lithography on a silicon wafer, and the silicon mold replica was transferred onto a flexible polydimethylsiloxane (PDMS) sheet for conformal patterning. The so-obtained PDMS mold was then applied on a ZnO film spin-coated on a glass substrate. During the imprinting process, the temperature was controlled from 100 to 250 °C to observe the transferring morphologies of the ZnO film; the nanopattern was successfully transferred at annealing temperatures of 200 and 250 °C because the ZnO film at the sol state filled the cavities of the PDMS nanopattern and solidified, forming a negative replica of the nanopattern. The direction of the nanopatterned ZnO film served as a guide for aligning the LC molecules on the LC surface at the centimeter scale and, due to their elastic characteristics and group behavior, propagating their directional states in the LC bulk. The resulting LC cell exhibited an enhanced electro-optical performance and high thermal endurance above 180 °C. The geometry of the alignment layer increased the electric field on the ZnO film and showed reduced threshold voltage. In addition, since flexible devices are generally based on polyimide, which imidized at around 200 °C, the relatively low annealing temperatures of our fabricated nanopatterned ZnO film allow it to be mounted on such devices without any deterioration of the underlying thermoplastic substrate. Therefore, nanopatterned ZnO has a considerable potential for advanced LC displays.

To achieve degradable, anti-biofouling coatings with longer lifetimes and better mechanical properties, we synthesized a series of degradable co-polyesters composed of cyclic ketene acetals, di-(ethylene glycol) methyl ether methacrylate, and a photoactive curing agent, 4-benzoylphenyl methacrylate, using a radical ring-opening polymerization. The precursor co-polyesters were spin-coated on a benzophenone-functionalized silicon wafer to form ca. 60 nm films and drop-casted on glass to form ∼32 μm films. The copolymers were cross-linked via UV irradiation at 365 nm. The degradation of films was studied by immersing the specimens in aqueous buffers of different pH values. The results show that both the pH of buffer solutions and gel fractions of networks affect the degradation rate. The coatings show good bovine serum albumin resistance capability. By adjusting the fractions of monomers, the degradation rate and degree of hydration (e.g., swelling ratio) are controllable.

We study the assembly of magnetite nanoparticles in water-based ferrofluids in wetting layers close to silicon substrates with different functionalization without and with an out-of-plane magnetic field. For particles of nominal sizes 5, 15, and 25 nm, we extract density profiles from neutron reflectivity measurements. We show that self-assembly is only promoted by a magnetic field if a seed layer is formed at the silicon substrate. Such a layer can be formed by chemisorption of activated N -hydroxysuccinimide ester-coated nanoparticles at a (3-aminopropyl)triethoxysilane functionalized surface. Less dense packing is reported for physisorption of the same particles at a piranha-treated (strongly hydrophilic) silicon wafer, and no wetting layer is found for a self-assembled monolayer of octadecyltrichlorosilane (strongly hydrophobic) at the interface. We show that once the seed layer is formed and under an out-of-plane magnetic field further wetting layers assemble. These layers become denser with time, larger magnetic fields, higher particle concentrations, and larger moment of the nanoparticles.

We report the deposition of cubic copper nanoparticles (Cu NPs) of varying size and particle density on silicon laser-induced periodic surface structures via reactive laser ablation in liquid (RLAL) using intense femtosecond laser pulses. Two syntheses were compared: (1) simultaneous deposition, wherein a silicon wafer was laser-processed in aqueous Cu(NO 3 ) 2 solution and (2) sequential deposition, wherein the silicon wafer was laser-processed in water and then exposed to aqueous Cu(NO 3 ) 2 . Only simultaneous deposition resulted in high Cu loading and cubic Cu NPs deposited on the surface. The solution pH, Cu(NO 3 ) 2 concentration, and sample translation rate were varied to determine their effects on the size, morphology, and density of Cu NPs. Solution pH near ∼6.8 maximized Cu deposition. The Cu(NO 3 ) 2 concentration affected the Cu NP morphology but not the size or Cu loading. The sample translation rate most significantly affected the Cu loading, particle size, and particle density. The observed synthesis parameter dependence of these Cu NP properties resembles results by electrodeposition to grow Cu NPs on silicon surfaces, which suggests that Cu NP deposition by RLAL follows a mechanism similar to electrodeposition.

The influence of adding nanoparticles on the ascast morphology of spin coated immiscible polystyrene/poly(methyl methacrylate) (PS/PMMA) thin films of different thickness ( h E , volume ratio of PS to PMMA) has been explored in this article. To understand the precise effect of nanoparticle addition, the morphology of PS/PMMA thin blend films spin cast from toluene on a native oxide covered silicon wafer substrate was first investigated. It is seen that in particle free films, the generic morphology of the films remains nearly unaltered with increase in R B , volume ratio of PS to PMMA) has been explored in this article. To understand the precise effect of nanoparticle addition, the morphology of PS/PMMA thin blend films spin cast from toluene on a native oxide covered silicon wafer substrate was first investigated. It is seen that in particle free films, the generic morphology of the films remains nearly unaltered with increase in h E , for R B = 3:1 and 1:3. In contrast, strong h E dependent morphology transformation is observed in films with R B = 1:1. Subsequently, thiol-capped gold nanoparticles (AuNP) containing films with different particle concentrations ( C NP ) were cast from the same solvent along with the polymer mixture. We observe that addition of AuNPs barely alters the generic morphology of the films with R B = 3:1. In contrast, the presence of the particles significantly influences the morphology of the films with R B = 1:1 and 1:3, particularly at higher C NP (≈10.0%). X-ray photoelectron spectroscopy and X-ray reflectivity of some samples reveal that the AuNPs tend to migrate to the free surface through the PS phase, thereby stabilizing this layer partially or fully (depending on C NP ) against dewetting over a surface of adsorbed PMMA layer and influencing the ascast morphology as a function of C NP . The work is fundamentally important in understanding largely overlooked implications of nanoparticle addition on the morphology of PS/PMMA blend thin films which forms the fundamental basis for future interesting studies involving dynamics of nanoparticles within the blend thin films.

The photocatalytic bactericidal activity of titanium dioxide (TiO 2 ) thin films has been extensively studied. In this study, we investigated the bactericidal activities of TiO 2 nanotube (NT) thin films using Escherichia coli and Staphylococcus aureus cells as the model bacteria. Metallic titanium (Ti) thin films were anodized on a silicon (Si) wafer substrate to form TiO 2 NT thin films. To evaluate the bactericidal activity of the TiO 2 NT thin films, bacteria on the TiO 2 NT thin films were irradiated with near-ultraviolet light (UV-A) at a wavelength of 365 nm. The bactericidal activity was estimated by the survival rate derived from the number of live cells, which form colonies on the cell culture medium. We demonstrated that the survival rate of the two types of bacteria investigated in this study was significantly reduced by UV light irradiation and that there was a difference in the temporal change in the survival rate between the two types of bacteria. Furthermore, we investigated the generation of reactive oxygen species (ROSs) by UV light irradiation of TiO 2 NT thin films using electron spin resonance spectroscopy and fluorescence analysis. We found that the main ROS generated on the surface of the TiO 2 NT film was the hydroxyl radical, OH • . In addition, the generation of ROSs increased with an increase in the UV irradiation time. We proposed a kinetic model that reproduces the dependence of bacterial viability on the UV light irradiation time by considering the temporal change in the amount of ROSs generated by UV light irradiation. A comparison of the calculated and experimental results revealed that the bactericidal effect consisted of the direct photolysis of bacteria and the photocatalysis via the generation of hydroxyl radicals, with the latter exhibiting a stronger bactericidal effect than the former.

In this work, we show that in order to fabricate coherent titania (TiO 2 ) films with precise thickness control, it is critical to generate a complete polymer brush monolayer. To date, demonstrations of such dense polymer monolayer formation that can be utilized for inorganic infiltration have been elusive. We describe a versatile bottom-up approach to covalently and rapidly (60 s processing) graft hydroxyl-terminated poly(2-vinyl pyridine) (P2VP-OH) polymers on silicon substrates. P2VP-OH monolayer films of varying thicknesses can subsequently be used to fabricate high-quality TiO 2 films. Our innovative strategy is based upon room-temperature titanium vapor-phase infiltration of the grafted P2VP-OH polymer brushes that can produce TiO 2 nanofilms of 2-4 nm thicknesses. Crucial parameters are explored, including molecular weight and solution concentration for grafting dense P2VP-OH monolayers from the liquid phase with high coverage and uniformity across wafer-scale areas (>2 cm 2 ). Additionally, we compare the P2VP-OH polymer systems with another reactive polymer, poly(methyl methacrylate)-OH, and a relatively nonreactive polymer, poly(styrene)-OH. Furthermore, we prove the latter to be effective for surface blocking and deactivation. We show a simple process to graft monolayers for polymers that are weakly interacting with one another but more challenging for reactive systems. Our methodology provides new insight into the rapid grafting of polymer brushes and their ability to form TiO 2 films. We believe that the results described herein are important for further expanding the use of reactive and unreactive polymers for fields including area-selective deposition, solar cell absorber layers, and antimicrobial surface coatings.

Laser processing is an emerging technique capable of synthesizing metal-silicon composite surfaces for various applications. However, little is known about the chemical composition of these laser-processed surfaces, and the reaction mechanisms leading to their formation are poorly understood. In this work, we report the formation of gold-silicon nanostructured surfaces through reactive laser ablation in liquid. Silicon wafers were immersed in pH-controlled solutions of KAuCl 4 and processed with ultrashort laser pulses. Gold deposition on the silicon wafers was found to depend on the pH of the precursor solution: neutral solutions (pH ∼6.3) resulted in much higher gold deposition than acidic or basic solutions. Laser processing of silicon wafers in water followed by immersion in the KAuCl 4 solution resulted in lower gold deposition. X-ray photoelectron spectroscopy and depth profiling showed the existence of both gold (Au 0 ) and gold-silicide (Au x Si) phases on the surfaces. Under both types of processing conditions, the gold atomic fraction and gold-silicide content increased with depth to at least 150 nm into the surface of the silicon wafer, although significantly more gold and gold-silicide were formed when the silicon was ablated in KAuCl 4 solution as compared to immersion in KAuCl 4 after ablation in water. Based on these data and existing literature on laser processing of silicon, we propose mechanisms that explain the observed gold penetration depth and its deposition dependence on solution pH. The mechanistic understanding gained in this work may be useful for synthesizing a variety of metal-silicon composite surfaces through laser processing to prepare functional materials such as catalysts and surface-enhanced Raman spectroscopy substrates.

The wetting of a solid surface by a liquid droplet under a liquid medium at elevated temperatures depends not only on the solid-drop and drop-medium interfacial tensions (IFTs) but also on the temperature dependency of the IFT of the surrounding medium. Previous studies have shown either a decreasing or nearly invariant trend of wettability with an increase in temperature. However, much of the research up to now has only focused on the evaluation of solid wettability in air or vapor, and no model has been proposed to predict the variation of solid wettability at high temperatures under a liquid medium. Here, we developed a theoretical framework and a novel experimental approach to evaluate the high-temperature solid-liquid-liquid wettability. We investigated the wettability of different polymeric and nonpolymeric surfaces, namely, glass, silicon wafer, poly(methyl methacrylate) (PMMA), and polytetrafluoroethylene (PTFE), for a wide range of polar and nonpolar probe droplets under water (as a liquid medium) at temperatures up to 90 °C. The experimental results revealed that the nonpolymeric highly polar solid surfaces, that is, glass and silicon wafer, showed a sharp increase in their contact angle with the probe droplets at elevated temperatures. Between the two polymeric surfaces, PMMA showed a decreasing trend of the contact angle over the variation of temperatures, while in the case of PTFE, no specific trend was observed. The predictions of our theoretical model were in good agreement with the experimental observations with less than ±25% deviation.

To observe a polymer chain deposited on a substrate by atomic force microscopy (AFM) at the molecular level, the substrate should be atomically flat and stable under laboratory conditions and adsorb polymer chains firmly. Therefore, substrates used under laboratory conditions are practically limited to mica, highly ordered pyrolytic graphite, and atomically stepped sapphire, and polymers observed by AFM at the molecular level are also limited. A silicon wafer is frequently used as a substrate for AFM observation for somewhat macroscopic observations, but the surface of the silicon wafer is too rough to observe polymer chains deposited on it at the molecular level. In this study, we prepared an atomically stepped Si(111) substrate via wet etching in NH 4 F and evaluated it as an AFM substrate. The Si(111) substrate was stable as an AFM substrate, and isolated poly(methyl methacrylate) (it-PMMA) chains and a crystalline monolayer deposited on the substrate were observed by AFM at the molecular level. An it-PMMA amorphous monolayer deposited on mica crystallized under high humidity, but that on the Si(111) substrate did not because of the difference in the surface nature and the crystal structure of the substrates. The Si(111) substrate was hydrophobic, and the it-PMMA monolayers could be deposited as a multilayer, which could not be formed on hydrophilic mica. The crystallization behavior of an it-PMMA amorphous multilayer and an amorphous/crystalline mixed multilayer on the Si(111) substrate was also evaluated.

Hydrophobic-hydrophilic hybrid surfaces, sometimes termed biphilic surfaces, have shown potential to enhance condensation and boiling heat transfer, anti-icing, and fog harvesting performance. However, state of art techniques to develop these surfaces have limited substrate selection, poor scalability, and lengthy and costly fabrication methods. Here, we develop a simple, scalable, and rapid stamping technique for hybrid surfaces with spatially controlled wettability. To enable stamping, rationally designed and prefabricated polydimethylsiloxane (PDMS) stamps, which are reusable and independent of the substrate and functional coating, were used. To demonstrate the stamping technique, we used silicon wafer, copper, and aluminum substrates functionalized with a variety of hydrophobic chemistries including heptadecafluorodecyltrimethoxy-silane, octafluorocyclobutane, and slippery omniphobic covalently attached liquids. Condensation experiments and microgoniometric characterization demonstrated that the stamped surfaces have global hydrophobicity or superhydrophobicity with localized hydrophilicity (spots) enabled by local removal of the functional coating during stamping. Stamped surfaces with superhydrophobic backgrounds and hydrophilic spots demonstrated stable coalescence induced droplet jumping. Compared to conventional techniques, our stamping method has comparable prototyping cost with reduced manufacturing time scale and cost. Our work not only presents design guidelines for the development of scalable hybrid surfaces for the study of phase change phenomena, it develops a scalable and rapid stamping protocol for the cost-effective manufacture of next-generation hybrid wettability surfaces.

The interfacial adhesion between silicon oxide surfaces is normally believed to be governed by the surface chemistry of the topmost surface affecting the water contact angle and hydrogen bonding interactions. In the case of a silicon wafer, the physical structure of the native oxide at the surface can vary drastically depending on the aging process; thus, not only the surface chemistry but also the history of surface treatment can also have a profound impact on nanoasperity adhesion. This study reports the effect of aging conditions (ambient air, liquid water, and liquid ethanol) on the nanoasperity adhesion behaviors of a silicon surface. When the silicon surface is kept in liquid alcohol, the surface remains hydrophobic, and adhesion in ambient air can be explained with the capillary effect of the liquid meniscus condensed around the annulus of the nanoasperity contact. When the silicon surface is oxidized in ambient air, the surface gradually becomes hydrophilic, and the strongly hydrogen-bonded water network of adsorbed water plays a dominant role in the nanoasperity interfacial adhesion force. When the silicon surface is aged in liquid water, the interfacial adhesion force measured in ambient air is significantly larger than the value predicted from the theoretical model based on the water contact angle and the hydrogen bonding interaction at the topmost surface. This is because the surface layer oxidized in liquid water is gel-like and thus can swell upon uptake of water from the humid air. To fully encompass all these behaviors, a solid-adsorbate-solid model predicting the adhesion force is developed by introducing a fitting parameter β, which can be adjusted depending on the adsorbed water structure and the swelling capacity of the oxidized surface layer.

Liquid applied to a chemically patterned (wetting/nonwetting, lyophilic/lyophobic) substrate forms a 3-dimensional contoured surface, the shape of which depends on the volume of liquid applied and the shape of the three-phase contact lines of air (or other phase in contact), liquid, and the wetted pattern. The resulting binary contoured interface with air, which consists of flat unwetted regions of the substrate and the mean curvature liquid-vapor interfaces of the sessile structures, can be used as a mold for imprinting solid polymers by curing liquid resins in contact. The success, flexibility with regard to shape, and reproducibility of this molding process depend on numerous issues. These include the substrate surface chemistry, the liquid application method, properties of the liquid (vapor pressure, surface tension, viscosity, and permeability in the resin), the contact angles of the liquid on the patterned substrate, and the resin curing chemistry and conditions. We investigate the room temperature platinum(0)-catalyzed curing of the most commonly studied commercial silicone elastomer, Sylgard 184, using molds composed of sessile drops of liquids on circular wetting features (bare silicon wafer) patterned on covalently attached fluoroalkylsilyl monolayers. Liquids reported are water, glycerol, an ethylene glycol oligomer, and an ionic liquid. The vapor pressure of water and its permeability in dimethyl silicone were important (and problematic) issues that could be controlled by adjusting humidity. The ionic liquid N -ethyl- N '-methylimidazolium methanesulfonate poisoned/inhibited the curing chemistry and affected silicone cross-link density and the resulting feature shape, but its lack of vapor pressure was useful in studying flow coating as a scalable liquid application method. The ethylene glycol oligomer exhibited compatibility with (and diffusion into) the silicone. Glycerol proved to be the most well-behaved and controllable liquid studied and was used to demonstrate that condensation/evaporation can be used to adjust feature shape.

A combined atomic force microscope (AFM)-peristaltic pump system was used to determine the effect of a flow on the forces between two negatively charged surfaces (silica particle and silicon wafer) in aqueous solutions containing surfactants. The effect of the surfactant charge on the forces was determined by using an anionic surfactant (sodium dodecyl sulfate, SDS) and a cationic surfactant (dodecyltrimethylammonium bromide, DTAB) of the same chain length. The surfactant concentration effect was determined by using concentrations up to the critical micelle concentration. In the case of SDS, a flow reduced the range and magnitude of the repulsive forces. The force range reduction was explained by a shrinking of the diffuse layers, due to the deformation of the diffuse layer by the flow. The force magnitude reduction was explained by (1) the increased electrostatic screening due to the thinner diffuse layers and (2) an increased adsorption of specific ions, such as Na + , to the silica surfaces. In the case of DTAB, a concentration (8.0 mM) that gave an attractive force in the absence of a flow gave a repulsive force in the presence of a flow. Comparison of AFM images of a silicon wafer in DTAB measured in the absence and presence of a liquid flow showed that the number of DTAB patches adsorbed to the silicon wafer increased with a liquid flow. The change in the forces with a flow was therefore explained by this change in the DTAB adsorption to the negatively charged surfaces. As a liquid flow can change the charge of a surface, it may be possible to control the aggregation/dispersion of charged particles via the flow rate, if the appropriate surfactant type and concentration are used.

One potential way to fabricate battery-on-chip is photopatterning electrochemical energy storage materials directly on electronics through lithography, but applicable materials are primarily limited to transparent photocurable resins. The transparency of the photoresist would be sacrificed after extra addition of insoluble inorganic battery materials and conductors. Given the importance of radical polymers for their appropriate solubility, optical transparency, and radical robustness, they may have potential application in on-chip energy storage, transport, and conversion devices. Herein, an anodic photoresist is proposed by modifying the MicroChem SU8 resist with a radical polymer poly(2,2,6,6-tetramethyl-4-piperidinyl- N -oxyl methacrylate) and an ionic conductor lithium perchlorate. It can be photopatterned on silicon wafer with 10 μm scale resolution, and it exhibits charge/discharge potentials at ca. 0.68 V versus silver chloride electrode; the coulomb efficiency is regarded as nearly equaling 100%. Although the specific capacity of the photopatterned film electrode is found to be modest, 1 × 10 -5 mA h·cm -2 , it presents 1/8 of its theoretical electron storage ability. All-solid-state half-cells with circular features 30 μm in diameter are prepared by means of overlay exposure using the as-prepared photoresist and lithium perchlorate-modified SU8 as the anodic electrode and solid electrolyte, respectively. These results suggest a promising way of using radical polymers for the integration of electrochemical energy in microelectronics.

A high-density poly(methyl methacrylate) (PMMA) brush (σ = 0.77 chain/nm 2 ) with a lower molecular weight distribution was prepared onto a silicon wafer by surface-initiated atom transfer radical polymerization. The surface of the PMMA brush chains was characterized upon the process of the environmental change, from air to water, using contact angle measurements in conjunction with sum-frequency generation spectroscopy. The surface structure and properties altered less with the changing environment from air to water for the PMMA brush than for a spin-coated film; that is, the extent of surface reorganization could be suppressed by grafting densely-packed chains onto a substrate. Also, the water penetration into the brush surface was inhibited because of the densely packed chain structure.

Manipulating the surface properties of materials via the application of coatings is a widely used strategy to achieve desired interfacial interactions, implicitly assuming that the interfacial forces of coated samples are determined exclusively by the surface properties of the coatings. However, interfacial interactions between materials and their environments operate over finite length scales. Thus, the question addressed in this study is whether interactions associated with bulk substrate materials could act through thin coatings or, conversely, how thick a coating needs to be to completely screen subsurface forces contributed by underlying substrates. Plasma polymer layers were deposited on silicon wafer substrates from ethanol vapor, with identical chemical composition, ultrasmooth surfaces, and varying thicknesses. Using colloid-probe atomic force microscopy, electrical double-layer forces were determined in solutions of various ionic strengths and fitted using the Derjaguin-Landau-Verwey-Overbeek theory. For the thicker ethanol plasma polymers, the fitted surface potentials reflected the presence of surface carboxylate groups and were invariant with thickness. In contrast, for coatings <18 nm thick, the surface potentials increased steadily with decreasing film thickness; the measured electrical double-layer forces contained contributions from both the coating and the substrate. Theoretical calculations were in agreement with this model. Thus, our observations indicate that the higher surface potential of the underlying SiO 2 surface can influence the interactions between a colloid particle and the multilayer structure if coatings are sufficiently thin. Such superposition needs to be factored into the design of coatings aimed at the control of material interactions via surface forces.

Imaging of the Li-insertion/extraction [Li-in/out] interface of the electrode materials of Li-ion batteries is essential to reveal their bulk mechanism of electrochemical reaction and phase behavior in the crystal. Generally, the material properties significantly change at this interface. Therefore, direct probing of the changing properties is a promising approach to reliably investigate the Li-in/out interface in the bulk crystal of electrode materials. In this study, we investigated the change in electron conductivity of rutile-TiO 2 with Li-insertion and extraction, as a model for the electrochemical interface of a bulk crystal of electrode material. In addition, we probed the interface using logarithm contact resistance [log  R (Ω)] imaging via scanning spreading resistance microscopy (SSRM). A distinct Li-in/out interface on the rutile-TiO 2 (001) wafer was observed using this technique. The imaging resolution of this region was estimated to be approximately 40-50 nm in SSRM images, which was two to three times higher than the resolution of the topographic image (100-150 nm), which was restricted to the curvature radius of the SSRM probe tip. A high spatial resolution was obtained via SSRM imaging because this approach is not influenced by the geometric effects of the surface. This result demonstrated the potential of SSRM imaging for the study of the Li-in/out interface.

Herein is reported the preparation of nanostructured mesoporous supported films, in this case, titanium dioxide nanoparticles on silicon wafer, according to a new approach taking place in two consecutive deposition steps: (i) coating of a homogeneous and continuous layer of a surfactant on the selected support and (ii) building up of a second layer of the fresh metal-oxide gel precursor, followed by thermal treatment to generate porosity. This approach represents an alternative way to soft-template procedures, as for instance, the largely applied evaporation-induced self-assembly (EISA) method, which typically consists of a single-step deposition of the mixture of gel precursor and surfactant used as a soft template to create porosity. The main advantage of the procedure reported here compared to the EISA method is the possibility of reaching tunable textural characteristics along the growing film (pore size, shape, and distribution of pores) by using gels with nanoparticles preformed at different stages via a simple regulation of the residence time of the precursors deposited on the support containing the surfactant.

A new thin-film fabrication method, adsorptive spin coating, was evaluated in the preparation of poly(vinyl alcohol) (PVOH) thin films on silicon-wafer-supported poly(dimethylsiloxane) (PDMS) substrates. This method takes advantage of the rapid spontaneous adsorption of PVOH at the substrate-solution interface during the brief contact period and the directionality of drying during spinning. Similar to the results obtained using dip coating, the PVOH thin films wet the 2 kDa PDMS substrate and exhibit dewetted fractal morphologies on thicker PDMS substrates. This method generated PVOH films with thicknesses that were comparable to those prepared by dip coating except that thicker PVOH films were obtained at lower spin rates, following the Meyerhofer relationship in the wetting regime. Stepwise dewetting dynamics of confined PVOH drops were captured using high-speed photography. Drying and polymer aggregation initiate at the periphery of the drop and propagate toward the center of the drop. Each dewetted thin film adopts the footprint of the original drop and shows globally ordered patterns, which depend on both initial drop size and spin rate. The PVOH thin films have excellent stability toward water rinse if they are continuous and are given sufficient time to dry. This new adsorptive spin-coating method is not only straightforward but also unique in its ability to generate globally ordered morphologies that are the outcome of fast spontaneous adsorption, spin symmetry, and temporally and spatially adjustable drying rates. It is a valuable tool for fabricating a wide range of thin-film systems where surface adsorption/reaction is rapid, in both wetting and nonwetting regimes.

In this work, an anti-icing coating based on superhydrophilic polyzwitterion brushes is reported. Poly(sulfobetaine methacrylate) (PSBMA) brushes were synthesized by surface-initiated atom-transferred radical polymerization to create superhydrophilic films on silicon wafers. The thickness of the PSBMA brushes film increased linearly with the polymerization time, and the film remained superhydrophilic in a nonassociated state when the thickness was less than ∼100 nm. DSC and FTIR analyses revealed that PSBMA contains more nonfreezable bound water than typical polyelectrolytes such as poly(sodium styrenesulfonate) and poly(2-(methacryloyloxy)ethyltrimethylammonium chloride), leading to lower ice adhesion strength than the latter two. At -20 °C, the PSBMA brushes coating demonstrated low ice adhesion strength of 60 kPa, showing a significant reduction in ice adhesion by up to ∼75% compared to uncoated silicon wafer. The optimum PSBMA layer thickness for low ice adhesion was ∼100 nm. These findings suggest that polyzwitterions are excellent candidates for anti-icing coating application.

Superparamagnetic cobalt nanoparticles (Co NPs) are an interesting material for self-assembly processes because of their magnetic properties. We investigated the magnetic field-induced assembly of superparamagnetic cobalt nanoparticles and compared three different approaches, namely, the assembly on solid substrates, at water-air, and ethylene glycol-air interfaces. Oleic acid- and trioctylphosphine oxide-coated Co NPs were synthesized via a thermolysis of cobalt carbonyl and dispersed into either hexane or toluene. The Co NP dispersion was dropped onto different substrates (e.g., transmission electron microscopy (TEM) grid, silicon wafer) and onto liquid surfaces. Transmission electron microscopy (TEM), scanning force microscopy, optical microscopy, as well as scanning electron microscopy showed that superparamagnetic Co NPs assembled into one-dimensional chains in an external magnetic field. By varying the concentration of the Co NP dispersion (1-5 mg/mL) and the strength of the magnetic field (4-54 mT), the morphology of the chains changed. Short, thin, and flexible chain structures were obtained at low NP concentration and low strength of magnetic field, whereas they became long, thick and straight when the NP concentration and the magnetic field strength increased. In comparison, the assembly of Co NPs from hexane dispersion at ethylene glycol-air interface showed the most regular and homogeneous alignment, since a more efficient spreading could be achieved on ethylene glycol than on water and solid substrates.

In this paper, a series of amphiphilic diblock polymers of poly(hydroxyethylacrylamide)- b-poly(1H,1H-pentafluoropropyl methacrylate) (PHEAA- b-PFMA) were grafted from silicon wafer via surface-initiated atom transfer radical polymerization (SI-ATRP). Surface wettability and chemical compositions of the modified surfaces were characterized by contact angle goniometer and X-ray photoelectron spectroscopy (XPS) respectively. Molecular weight and polydispersity of each block were measured using gel permeation chromatography (GPC). The topography and the microphase separation behavior of PHEAA- b-PFMA surfaces were investigated by atomic force microscope (AFM). The results show that only when the grafting density (σ) and thickness of PHEAA brush were in the range of 0.9-1.3 (chain/nm 2 ) and 6.6-15.1 nm, respectively, and the ratio of PFMA/PHEAA varied from 89/42 to 89/94, could the diblock copolymer phase separate into nanostructures. Further, the antiprotein adsorption performance of the modified surfaces against BSA, fibrinogen, and lysozyme was studied. The results indicated the modified surfaces could reduce the protein adsorption compared to the pristine silicon wafer. For Fibrinogen, the antiadsorption effect of PHEAA- b-PFMA-modified surfaces with microphase segregation was better than that of corresponding PHEAA modified surfaces. The results provide further evidence that surface composition and microphase segregation of fluorinated moieties of block copolymer brushes significantly impact protein adsorption behaviors.

We describe measurements of adsorption between two flat plates when the plates are separated by 0-65 nm. The objective is to examine how adsorption is affected by confinement in very thin films. It is well known that adsorption of simple ions can change with the thickness of a thin film (charge regulation); here, we describe a direct method to measure adsorption as a function of confinement and results for one example. Measurement of all separations is achieved simultaneously by measuring visible-light interference in a wedge-shaped crack created between an oxidized silicon wafer and a glass wafer. The adsorbed amount is measured from the fluorescence emission of a dye, after accounting for the optical interference. The specific measurement is of the depletion of a divalent anion, fluorescein, in aqueous solution between two anionic solids, but the measurement could be applied to a range of fluorescent probes. At large separations between the flat plates, the dye is depleted relative to the bulk concentration. At smaller separations, the depletion of the dye decreases. The range of the depletion and the magnitude of depletion decrease with shorter Debye length. Both of these effects are consistent with a simple calculation using the Poisson-Boltzmann equation. There is a multitude of applications where surfactants, polymers, ions, etc. are adsorbed to effect changes in thin films. One example is adsorption designed to alter the stability of colloidal particles.