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Droplet-based microfluidic technology can be utilized as a microreactor to prepare novel functional monodisperse microcapsules. In this study, a droplet-based microfluidic chip with surface modification, which allowed the one-step preparation of double emulsion microcapsules. An O/W/O double emulsion using polyethylene (glycol) diacrylate (PEGDA) solution as the intermediate water phase was prepared by regulating the hydrophilicity and hydrophobicity of the chip surface, with PEGDA microcapsules prepared using UV polymerization. And then anti-tumor drug paclitaxel and neurotoxin 6-OHDA were encapsulated in microcapsules for drug and toxicology evaluation, respectively. Compared to controls, drug-loaded microcapsules caused a significant increase in the death rate of PC12 cells. This indicates that the obtained drug-loaded microcapsules could be used in drug evaluation and potentially in drug screening and delivery.

This letter presents a new class of High-overtone Bulk Acoustic Resonators (HBARs) with only top electrodes but excellent performance using lithium niobate (LN) thin films on conductive silicon carbide (SiC). The 4-inch single-crystalline lithium niobate thin film on conductive SiC (LNCSiC) substrate was prepared by ion-cutting process. Since the conductive SiC serves as both the resonant cavity and the floating electrode, the HBARs based on LNCSiC with only top electrodes were designed and fabricated. The devices show a wide frequency response span exceeding 2.0 GHz, a frequency spacing of 10 MHz, an excellent f $\cdot $ Q $_{\textit {LAKIN}}$ product of ${9.6}\times {10} ^{{13}}$ Hz ( f $\cdot $ Bode-Q of ${1.1}\times {10} ^{{14}}$ Hz), and a low temperature coefficient of frequency (TCF) of −18.9 ppm/°C. The frequency response shift of the proposed HBAR can be achieved by just adjusting the in-plane orientation of the top electrodes. Additionally, a multi-band filter was numerically synthesized based on the proposed HBARs, showing a spectral spacing of 10 MHz and a passband span of more than 2.0 GHz. Upon further optimizations, the proposed HBARs with a wide frequency response, a high- f $\cdot $ Q , and a low-TCF will be very promising for radio-frequency applications.

Recently, polypropylene (PP) is considered as the potential recyclable HVDC cable insulation material. Ethylene-based copolymer (EBC) and propylene-based copolymer (PBC) were introduced into PP to tailor the properties of PP and make it more capable for HVDC cable insulation application. This paper focused on the effects of two additions on those propertied such as microstructure, thermal properties, electrical properties and space charge accumulation of PP. The results indicated that PBC was uniformly dispersed in the matrix of PP without adhesion, and its particle size did not increase with the increase of its content in the matrix. With the increase of PBC, the glass transition peak of polypropylene decreased slowly, indicating a better performance on flexibility at low temperature. With the increase of content of copolymer, the DC volume resistivity of the composite material decreased gradually, but samples with PBC had higher resistivity than samples with EBC. In the term of space charge, the addition of PBC could help suppressing the accumulation of space charge better. To sum up, PP/PBC composite material could be an option for recyclable DC cable insulation material.

Hexagonal CuS nanosheets and microspheres composed of numerous flakes were successfully prepared by sonochemical and solvothermal methods, respectively. Ultrasonic radiation and templates of Cu(OH)2 nanoribbons play important roles in the growth of CuS nanosheets. The surfactant PVP restricts the diffusion and growth process, inducing the formation of CuS microspheres under solvothermal conditions. Their better crystallinity, larger interlayer distance and incompact structure made the CuS nanosheets more conducive to the transport of sodium ions. Electrochemical studies showed that the nanosheet electrode exhibits better sodium storage performance compared to the CuS microspheres. The higher specific surface area (25.209 m2 g−1) of the CuS nanosheets provides a larger electrode/electrolyte contact area in the sodiation–desodiation process. The first discharge capacity of the CuS nanosheets could reach 398.6 mA h g−1 which is 71.18% of the theoretical capacity (560 mA h g−1). These results indicate that incompact structures have an advantage in storing sodium ions compared with compact structures.

In this work, the phase velocity (V p ) and the electromechanical coupling factors (k t 2) of SH0 modes excited in X-cut LiNbO 3 (LN) films were studied by finite element analysis, and both of them show strong dispersion when LN films are bonded to foreign substrates. In particular, the V p of the SH0 mode in LiNbO 3 -on-SiC (LNOSiC) substrate can exceed 1.5 times the value in LN plate, so as the operating frequency. 4-inch LNOSiC substrate was fabricated by ion-cutting process. A group of SH0 mode resonators on the novel LNOSiC substrate were demonstrated, so as the ladder-type filter. Since part of the acoustic energy of the SH0 mode penetrates into the high-velocity SiC supporting substrate, the fabricated resonator exhibits a phase velocity of exceeding 5000 m/s. The ladder-type filter composed of the SH0 mode resonators with increased velocity shows a center frequency (f c ) of 3.93 GHz, an insertion loss (IL) of 2.05 dB and a 3-dB fractional bandwidth (FBW) of 14.2%. The acoustic devices on LNOSiC heterogeneous substrate are very promising for high frequency and wideband 5G front-ends.

In this work, a novel heterogeneous substrate of lithium tantalate thin film on silicon carbide (LiTaO 3 -on-SiC, LTOSiC) was proposed and prepared. Since the SiC features an extremely-high phase velocity, a low acoustic loss and a small thermal expansion coefficient (CTE), surface acoustic wave devices with high frequency, low loss and low TCF were achieved on the LTOSiC substrate. The fabricated shear horizontal surface acoustic wave (SH-SAW) resonator shows a maximum Bode-Q (Bode-Qmax) of 2235 and a low TCF of -9.4 ppm/K at 1.90 GHz, while the longitudinal leaky surface acoustic wave (LLSAW) resonator shows a high Bode-Qmax of 1180 and an improved TCF of -24.7 ppm/K at 4.40 GHz. The ladder-type filter composed of SH-SAW resonators was also demonstrated, showing a center frequency (fc) of 3.03 GHz, an insertion loss (IL) of 0.9 dB and a 3-dB bandwidth of 101 MHz. The TCFs at - 3 dB attenuation of the lower and higher frequency side of passband are -13.8 and -15.8 ppm/K, respectively. The acoustic devices on LTOSiC substrate possess the prospect of commercial applications in 5G era.

In this work, we introduce a novel architecture for monolithic integrated multiband filters based on lithium niobate on insulator (LNOI) platform. The advantages of the crystal cut of Y124° are introduced compared to Z-cut. Three typical acoustic modes are excited simultaneously in different in-plane directions of a 400 nm Y124°-cut LiNbO 3 thin film. Combining with the buried electrode structure, the multiband filters with a wide operating frequency range from L band to C band, and a wide fractional bandwidth (FBW) range from 3.5% to 26% are achieved. The proposed structure provides an attractive solution for monolithic integration of filters.

The charge transport in polypropylene was studied under DC electric fields at different temperatures. By the experimental measurement and simulation of the BCT model, we studied conduction currents, breakdown strength, and space charge distribution. In particular, the conduction characteristics under high temperature and high field, especially the conduction characteristics before the breakdown, were studied by systematic experiments, and the conduction characteristics and the breakdown mechanism were further studied by simulation. The results show that in the process of measuring conduction currents until breakdown, both high temperature and high electric field will promote charge transport. However, the free volume will increase at high temperature, which will easily lead to faster charge transport and breakdown. In the breakdown process at different temperatures, there are different breakdown mechanisms. At 20–60 °C, the electric breakdown process has mainly occurred in polypropylene film, and the breakdown strength is almost unchanged. At 80 °C, electric breakdown and thermal breakdown act together, and the charge transport is faster, and the breakdown field becomes smaller. Finally, we conclude that thermal stress plays a very important role in charge transport. In a high-temperature environment, the volume expansion of polypropylene will promote charge transport, and the insulation of polypropylene capacitor films will be damaged.

The impact of two nonionic surfactants, namely Span 20 and Span 85, on the electrorheological response and colloidal stability of urea-coated barium titanyl oxalate (BTRU)/silicone oil suspensions is investigated. We quantitatively analyze the surfactant effect on modified ER performance through the measurements of yield stress and current density, as well as the tuned suspension stability through calculation of the Turbiscan stability index (TSI) and naked-eye observations of sedimentation phenomena. The surfactant effect on particle–oil interactions and agglomeration effects is examined by measuring the permeability of silicone oil when mixed with the Span surfactant and the cluster size of particles in dispersing medium, respectively. Our results indicate that with the presence of a Span surfactant, the yield stress of the suspension exhibits a local maximum at certain Span concentrations. We hypothesize that below the optimal Span concentration, the ER properties are enhanced by the increase of the electrostatic interaction between particles. Above the limiting concentration, the ER activity is weakened by the formation of a double-layer surfactant structure that generates a steric hindrance effect. We discover that the addition of the Span surfactant favors the improvement of the particle agglomeration phenomenon, thereby promoting colloidal stability of the suspension. Consequently, in the consideration of both ER properties and suspension stability, an optimal ER fluid with the addition of 0.4 wt% Span 85 is acquired with remarkable integrated ER properties.

Wearable pressure sensors with excellent flexibility and sensitivity have emerged as a promising field for electronic skin, healthcare monitoring, and so forth. Herein, we report a flexible, tunabl...

This paper presents a novel approach for automatic, rapid and efficient micro-droplet mixing on ‘open-surface’ droplet-based microfluidics system via magnetic actuation. A two-step micro-fabrication process was employed to decorate the magnetically functionalized polydimethylsiloxane (PDMS) membrane with micro-pillar arrays (MPA) to reduce the adhesion on resident droplets. Droplet manipulation relies on the localized deformation of the elastic membrane under external magnetic fields, thus relieving the additives of magnetic components to the droplets that is commonly required in conventional magnetism-based actuation. Via integration with peripheral computer-based regulator, swift droplet mixing is realized via controlling the coalescent droplets back and forth to generate internal fluid circulations for enhanced mass transfer within the droplet. The comparison of mixing performance between the coalesce-and-stop and back-and-forth mode was systematically performed, which verifies that the back-and-forth actuation of the droplets can obviously improve the mixing efficiency, and typically a higher driving frequency on the droplet renders a shorter mixing duration. With driving frequency of 2.5 cycles/s, the mixing homogeneity can reach 80% within 0.6 s and reach 90% within 1.5 s. Also, it has been experimentally demonstrated that the proposed system can accelerate the dilution under various volume ratios, including 1:2, 1:5, and 1:10. Finally, we demonstrated that the platform can be used to dynamically manipulate the droplets, allowing the de-pinning effect for molecular concentrating and obvious detection sensitivity enhancement in terms of Surface-Enhanced Raman Scattering (SERS). Owing to the superiorities including programmable efficient mixing and parallel scalability, the study herein offers insights for exploiting cost-effective and versatile microfluidics platform for future application in biological analysis, chemical micro-reactions, and trace molecule detections.

Recently, surface with desirable gradients has been proved to be a powerful tool for diverse applications from biological systems and chemical analysis to material science. In this work, we demonstrate a versatile and universal approach to realize controllable physicochemical properties in orthogonal gradients on polydimethylsiloxane (PDMS) surface. Based on a novel microfluidics network, we can easily establish the concentration gradients within the microfluidic channel for surface polymerization or chemical deposition to realize the stable characteristic gradient on the PDMS substrate. The method was introduced to prepare surface with two-dimensional physical (roughness) gradients, or combinational physicochemical gradients to study the synergistic effect on interested phenomenon. As a proof of concept, the experimental results show that the as-prepared substrate can effectively influence in various fields, such as protein adsorption and nano-particle immobilization, which can potentially be used for future systematical study in biological systems or practical applications in bio/chemical analysis/sensing.

Three different novel dry-etching methods have been employed to fabricate nanophotonic devices upon a thin-film lithium niobate on insulator material platform. Different dry-etching processes and their advantages, drawbacks and applicable scenarios are systematically studied. Ultra-smooth etching surface with roughness of 0.46 nm (Rq), low-loss ridge waveguides with extracted propagation loss of 1.42 dB/cm, and microring resonators with high optical quality factors up to 1.4×105 are demonstrated using the optimized low-loss etching recipe. The low-loss etching technique lays a foundation for monolithic integration of passive optical components with quantum dots, on-chip broadband electro- optic modulators and wafer-scale lithium niobate integrated photonic circuits.

We demonstrate groups of surface wave (SH0 mode) and Lamb wave (S0 mode) acoustic devices on lithium niobate thin films on silicon carbide (LNOSiC) heterogeneous substrate. The 4-inch LNOSiC with an excellent thermal transport property is prepared by ion-cutting process. The fabricated acoustic resonators on the LNOSiC substrate show scalable resonances from 2.0 to 4.72 GHz, in which the SH0 (S0) mode resonator shows a $k_t^2$ of 24.1% (15.5%) and a maximum Bode-Q of 976 (577) at 2.54 (3.56) GHz. Moreover, the phase velocity (Vp) of the SH0 (S0) mode is greater than 5000 (6400) m/s, which is about 1.25 (1.6) times higher than that of the conventional SAWs, so as the operating frequency. The filter with a center frequency of 2.62 GHz, an insertion loss (IL) of 1.06 dB, and a 3-dB fractional bandwidth (FBW) of 12.6% (three times larger than that of the conventional SAWs) is also achieved. The acoustic devices on heterogeneous substrate are very promising for high frequency, wideband and high power 5G front-ends.

Giant electrorheological (GER) fluids exhibit a high yield stress due to saturation surface polarization from contact between neighboring particles. To fine-tune the competitive performance of GER fluids, we modified the surface of the GER particles by adding silicone polyether, which strongly adsorbed at the solid-liquid interface and significantly influenced the dispersion, GER effect and electrical current density of the GER fluid. We discovered that a small amount of silicone polyether could improve the dispersion and reduce the electrical current density of the fluid. However, the steric hindrance effect suppressed the GER performance. Ultimately, an optimal solution was obtained by making tradeoffs among the dispersion, current density, viscosity, anti-sedimentation and ER effect. These tradeoffs were effective because they provided repetitive stability and wide opportunities for industrial usage.

Calcium carbonate biomimetic crystallization remains a topic of interest with respect to biomineralization areas in recent research. It is not easy to conduct high-throughput experiments with only a few macromolecule reagents using conventional experimental methods. However, the emergence of microdroplet array technology provides the possibility to solve these issues efficiently. In this article, surface-tension-confined droplet arrays were used to fabricate calcium carbonate. It was found that calcium carbonate crystallization can be conducted in surface-tension-confined droplets. Defects were found on the surface of some crystals, which were caused by liquid flow inside the droplet and the rapid drop in droplet height during the evaporation. The diameter and number of crystals were related to the droplet diameter. Polyacrylic acid (PAA), added as a modified organic molecule control, changed the CaCO3 morphology from calcite to vaterite. The material products of the above experiments were compared with bulk-synthesized calcium carbonate by scanning electron microscopy (SEM), Raman spectroscopy and other characterization methods. Our work proves the possibility of performing biomimetic crystallization and biomineralization experiments on surface-tension-confined microdroplet arrays.

Graphene or reduced graphene oxide (rGO) membrane-based materials are promising for many advanced applications due to their exceptional properties. One of the most widely used synthesis methods for rGO membranes is vacuum filtration of graphene oxide (GO) on a filter membrane, followed by reduction, which shows great advantages such as operational convenience and good controllability. Despite vacuum-filtrated rGO membranes being widely used in many applications, a fundamental question is overlooked: are the top and bottom surfaces of the membranes formed at the interfaces with air and with the filter membrane respectively symmetric or asymmetric? This work, for the first time, reports the asymmetry of the vacuum-filtrated rGO membranes and discloses the filter membranes' physical imprint on the bottom surface of the rGO membrane, which takes place when the filter membrane surface pores have similar dimension to GO sheets. This result points out that the asymmetric surface properties should be cautiously taken into consideration while designing the surface-related applications for GO and rGO membranes.

In this paper, two kinds of isotropic giant electrorheological elastomers (GERE) were prepared with urea-coated barium titanyl oxalate nanoparticles as dielectric particles filler, poly (dimethyl siloxane) (PDMS) as an elastic matrix and silicone oil as a plasticizer. Such GEREs are far superior to other isotropic and even anisotropic electrorheological elastomers (EREs), showing excellent electrorheological (ER) performance. The theoretic mechanism in elastomers prepared by us should be explained by saturation surface polarization or orientational polarization model. More interestingly, the storage modulus increment (ΔG′) of GEREs displays curvilinear dependence on the electric field due to poor particle mobility and different mobility under different electric fields, rather than a predicted linear variation. After testing their viscoelastic and dielectric properties and microstructures, we found that too high of the powder content leads to the serious agglomeration of particles and the performance degradation of the elastomer. An incorporation of silicone oil improved the dispersion state and wettability between the particles and matrix. At the same time, silicone oil reduced the hardness of the matrix and made the particles align more easily in the PDMS matrix. Lower initial modulus and higher field-induced modulus make GEREs containing silicone oil have ultrahigh storage modulus sensitivity, in which the best-performing sample achieved a storage modulus change exceeding 400 kPa and attained a maximum relative ER effect of 3280% at 3 kV/mm. Finally, the GERE was used to reversibly control the amplitude of circular motion within seconds by varying electric fields, revealing broad potential application in vibration control.

Metal-organic frameworks (MOFs) have attracted considerable attention as novel nanoporous materials that combine the properties of organic and inorganic porous materials. HKUST-1 is one of the most well-developed and representative MOFs with wide applications in gas storage and separation, adsorption, and capture. In this study, we used microfluidics, an advanced technique of manipulation of small fluid volumes in microscale or even nanoscale channels, to investigate the effect of sodium dodecyl sulfate (SDS) on the growth of HKUST-1 crystals. We directly observed the morphological evolution of HKUST-1 crystals through droplet arrays with the SDS concentration gradient. The morphology of HKUST-1 evolved from cubic to cuboctahedron and finally to octahedron with increasing SDS concentration. The study results demonstrated the important role played by anions in solution in the structural regulation of HKUST-1.

High-quality single-wall carbon nanotube (SWCNT) films were lightly fluorinated by treatment with xenon difluoride at room temperature, which led to the formation of ionic C–F bonds on tube walls and controllable p-type doping of the nanotubes. The fluorinated SWCNT films showed improved electronic conductivity and a higher work function. In addition, the fluorination process increased the areal density of SWCNT films and decreased their surface roughness, leading to better interface contact between them and silicon. As a result, a heterojunction solar cell constructed using the lightly fluorinated SWCNT film has a high power conversion efficiency of 13.6% and excellent stability.

In this study, we successively and parallelly slide a solvent strip on a polydimethylsiloxane microwell array to dilute the solution within the microwells. A total of 60 concentration gradients were generated one by one along the sliding direction within minutes while simultaneously forming 60 microwells with the same concentration perpendicular to the sliding direction. Using theoretical calculations, simulated predictions and experimental verification, we could regulate the concentration gradient on the microwell array by tuning the parameters of the sliding head and sliding speed. Afterwards, we cultured human non-small cell lung cancer cells and produced an anticancer drug concentration gradient on the microwell array by this sliding method. The cell viability was examined to demonstrate the potential of this method for high-throughput cell-based drug testing and screening, and this open microwell array method may enable further analysis during a drug-screening process.

Self-healing hydrophobic light-to-heat conversion membranes for interfacial solar heating are fabricated by deposition of light-to-heat conversion material of polypyrrole onto a porous stainless-steel mesh, followed by hydrophobic fluoroalkylsilane modification. The mesh-based membranes spontaneously stay at the water-air interface, collect and convert solar light into heat, and locally heat only the water surface for enhanced evaporation.

Flexible films of polytungstate (PT) as active ingredients were fabricated in PDMS as a “band-Aid” to achieve controllable H2O2 release. In these different systems of an amorphous PT building block, the lengthened lifetime (bleaching process) of photo-electron–hole separation is attributed to the electron trapping of the PT network and the existence of hole scavengers. The hole scavengers further prevent recombination of electrons and holes, so that the long-lived photoelectron could provide sustainable reactive oxygen species (ROS) by trapped electrons. Transient absorption illustrates the kinetic competition between the process of photohole induced bleaching and coloration induced by weak irradiation, which suggests that the hole scavenger is vital for ROS generation. The signals of electron spin resonance further confirm the existence of ROS. The profiles of controllable H2O2 with various release efficiency were obtained via fluorescence studies. The results indicate that the H2O2 release efficiency is related to both the hole scavenger and the tungstate cluster. The released H2O2 on the responses of tumor cells were evaluated. Compared with a cancer drug, the controllable and reversible released H2O2 delivery is highly efficient in preventing the proliferation and inducing apoptosis of A375 melanoma cells.

Fog water collection represents a meaningful effort in places where regular water sources, including surface water and ground water, are scarce. Inspired by the amazing fog water collection capability of the Stenocara beetles in the Namib Desert and based on the recent work in biomimetic water collection, this work reports a facile, easy-to-operate, and low-cost method for the fabrication of a hydrophilic–superhydrophobic patterned hybrid surface towards highly efficient fog water collection. The essence of the method is incorporating a (super)hydrophobically modified metal-based gauze onto the surface of a hydrophilic polystyrene (PS) flat sheet by a simple lab oven-based thermal pressing procedure. The produced hybrid patterned surfaces consisted of PS patches sitting within the holes of the metal gauzes. The method allows for easy control over the pattern’s dimensions (e.g., patch size) by varying the gauze mesh size and the thermal pressing temperature, which is then translated into the easy optimization of the ultimate fog water collection efficiency. Given the low-cost and wide availability of both PS and the metal gauze, this method has great potential for scaling-up. The results showed that the hydrophilic–superhydrophobic patterned hybrid surfaces with a similar pattern size to the Stenocara beetles's back pattern produced a significantly higher fog collection efficiency than the uniformly (super)hydrophilic or (super)hydrophobic surfaces. This work contributes to the general effort in fabricating mixed wettability patterned surfaces for atmospheric water collection for direct use.

This review covers three aspects of PCR-based microfluidic chip assays: sample preparation, target amplification, and product detection. We also discuss the challenges related to the miniaturization and integration of each assay and make a comparison between conventional and microfluidic schemes. In order to accomplish these essential assays without human intervention between individual steps, the micro-components for fluid manipulation become critical. We therefore summarize and discuss components such as microvalves (for fluid regulation), pumps (for fluid driving) and mixers (for blending fluids). By combining the above assays and microcomponents, DNA testing of multi-step bio-reactions in microfluidic chips may be achieved with minimal external control. The combination of assay schemes with the use of micro-components also leads to rapid methods for DNA testing via multi-step bioreactions. Contains 259 references.

Mitochondria have been described as 'the powerhouse of the cell' as the organelle generates the majority of adenosine triphosphate (ATP) in cells to support life. Mitochondria can be damaged due to stress, for example by reactive oxygen species (ROS). TP53-induced glycolysis and apoptosis regulator (TIGAR) serves a role in suppressing ROS damage and may protect mitochondria integrity. In the present study, the localization of TIGAR on mitochondria in 5-8F cells was demonstrated. Furthermore, it was indicated that the knockdown of TIGAR using lentivirus-short hairpin RNA induces the loss of mitochondrial membrane potential and cytochrome c leakage. However, these damaged mitochondria were not degraded in cells, but exhibited an abnormal appearance as indicated by mitochondrial swelling, crista collapse and vacuolization, with physiological dysfunction marked by reduced ATP production. Therefore, TIGAR maybe an indispensable protein for mitochondrial protection and degradation following cellular damage.

We report a simple and cost-effective method for fabricating integrated electronic-microfluidic devices with multilayer configurations. A CO2 laser plotter was employed to directly write patterns on a transferred polydimethylsiloxane (PDMS) layer, which served as both a bonding and a working layer. The integration of electronics in microfluidic devices was achieved by an alignment bonding of top and bottom electrode-patterned substrates fabricated with conventional lithography, sputtering and lift-off techniques. Processes of the developed fabrication method were illustrated. Major issues associated with this method as PDMS surface treatment and characterization, thickness-control of the transferred PDMS layer, and laser parameters optimization were discussed, along with the examination and testing of bonding with two representative materials (glass and silicon). The capability of this method was further demonstrated by fabricating a microfluidic chip with sputter-coated electrodes on the top and bottom substrates. The device functioning as a microparticle focusing and trapping chip was experimentally verified. It is confirmed that the proposed method has many advantages, including simple and fast fabrication process, low cost, easy integration of electronics, strong bonding strength, chemical and biological compatibility, etc.

In this paper, we report the construction of a polymerase chain reaction (PCR) device for fast amplification and detection of DNA. This device consists of an interchangeable PCR chamber, a temperature control component as well as an optical detection system. The DNA amplification happens on an interchangeable chip with the volumes as low as 1.25 μl, while the heating and cooling rate was as fast as 12.7°C/second ensuring that the total time needed of only 25 min to complete the 35 cycle PCR amplification. An optimized PCR with two-temperature approach for denaturing and annealing (Td and Ta) of DNA was also formulated with the PCR chip, with which the amplification of male-specific sex determining region Y (SRY) gene marker by utilizing raw saliva was successfully achieved and the genetic identification was in-situ detected right after PCR by the optical detection system.

We report a simple approach for measuring the local contact angle of liquids on a heterogeneous surface consisting of intersected hydrophobic and hydrophilic patch arrays, specifically by employing confocal microscopy and the addition of a very low concentration of Rhodamine-B (RB) (2 × 10(-7) mol/L). Interestingly, RB at that concentration was found to be aggregated at the air-liquid and solid (hydrophobic patch only)-liquid interfaces, which helps us to distinguish the liquid and solid interfaces as well as hydrophobic and hydrophilic patches by their corresponding fluorescent intensities. From the measured local contact angles, the line tension can be easily derived and the value is found to be (-2.06-1.53) × 10(-6) J/m.

The electrochemical properties of ferrocene (Fc) on a glassy carbon (GC) electrode modified by multi-walled carbon nanotubes (MWNTs) in the presence and absence of surfactants have been investigated by progressively voltammetric sweeping. Dihexadecyl phosphate (DHP) and hexadecyl trismethyl ammonium chloride (HTAC) are found to impact the redox reactions of Fc adsorbed on MWNT surfaces. An excess amount of DHP dispatches Fc from MWNTs surfaces, leading to weakly adsorbed configuration of Fc. The formal potential of the adsorbed Fc in the presence of DHP shifts to a lower potential. Cationic surfactant HTAC on MWNT surfaces depresses the redox reactions corresponding to the weakly adsorbed configuration of Fc. It becomes evident that the configuration and hence redox reactions of Fc depend strongly on the presence and concentrations of surfactants on the electrode surfaces and in the buffer solutions.

It is found that nucleic acids can enhance the fluorescence intensity of yttrium(III) (Y(3+))-rutin in presence of cetyltrimethylammonium bromide (CTMAB) system. In hexamethylenetetramine (HMTA)-HCl buffer, the maximum enhanced fluorescence is produced, with maximum excitation and emission wavelengths at 452 and 520 nm, respectively. Based on this, a new fluorimetric method of determination of nucleic acids is proposed. Under optimum conditions, the enhanced fluorescence intensity is proportion to the concentration of nucleic acids in the range of 1.0 x 10(-7) to 1.0 x 10(-5)g/ml for fish sperm DNA (fsDNA), 1.0 x 10(-7) to 4.6 x 10(-6)g/ml for yeast RNA (yRNA), their detection limits (S/N=3) are 7.5 x 10(-8), 8.0 x 10(-8)g/ml, respectively. The interaction mechanism is also studied.

Three-dimensional (3D) temperature mapping method with high spatial resolution and acquisition rate is of vital importance in evaluating thermal processes in micro-environment. We have synthesized a new temperature-sensitive functional material (Rhodamine B functionalized Polydimethylsiloxane). By performing optical sectioning of this material, we established an advanced method for visualizing the micro-scale 3D thermal distribution inside microfluidic chip with down to 10 ms temporal resolution and 2 ~ 6°C temperature resolution depending the capture parameters. This method is successfully applied to monitor the local temperature variation throughout micro-droplet heat transfer process and further reveal exothermic nanoliter droplet reactions to be unique and milder than bench-top experiment.

Photocatalysis provides a ‘green’ approach to completely eliminate various kinds of contaminants that are fatal for current environmental and energy issues. Semiconductors are one of the most frequently used photocatalysts as they can absorb light over a wide spectral range. However, it is also well known that naked SiO2 is not an efficient photocatalyst due to its relatively large band gap, which could only absorb shortwave ultraviolet light. In this report, nanoscale particles of carbon-doped silicon dioxide (C-doped SiO2) for use in photocatalysis were successfully prepared by a facile one-pot thermal process using tetraethylorthosilicate (TEOS) as the source of both silicon and carbon. These particles were subsequently characterized by thermogravimetric analysis, X-ray diffraction, standard and high resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The C-doped SiO2 displayed outstanding photocatalytic properties, as evidenced by its catalysis of Rhodamine B degradation under near-UV irradiation. We propose that carbon doping of the SiO2 lattice creates new energy states between the bottom of the conduction band and the top of the valence band, which narrows the band gap of the material. As a result, the C-doped SiO2 nanoparticles exhibit excellent photocatalytic activities in a neutral environment. The novel synthesis reported herein for this material is both energy efficient and environmentally friendly and as such shows promise as a technique for low-cost, readily scalable industrial production.

A microheater and a thermal sensor were fabricated inside elastomeric polydimethylsiloxane microchannels by injecting silver paint (or other conductive materials) into the channels. With a high-precision control scheme, microheaters can be used for rapid heating, with precise temperature control and uniform thermal distribution. Using such a microheater and feedback system, a polymerase chain reaction experiment was carried out whereas the DNA was successfully amplified in 25 cycles, with 1 min per cycle.

A novel microfluidic pressure sensor which can be fully integrated into polydimethylsiloxane (PDMS) is reported. The sensor produces electrical signals directly. We integrated PDMS-based conductive composites into a 30 mum thick membrane and bonded it to the microchannel side wall. The response time of the sensor is approximately 100 ms and can work within a pressure range as wide as 0-100 kPa. The resolution of this micropressure sensor is generally 0.1 kPa but can be increased to 0.01 kPa at high pressures as a result of the quadratic relationship between resistance and pressure. The PDMS-based nature of the sensor ensures its perfect bonding with PDMS chips, and the standard photolithographic process of the sensor allows one-time fabrication of three dimensional structures or even microsensor arrays. The theoretical calculations are in good agreement with experimental observations.

We show that the chemical structures of silicone oils can have an important role in the giant electrorheological (GER) effect. The interaction between silicone oils and solid nanoparticles is found to significantly influence the ER effect. By increasing the kinematic viscosity of silicone oils, which is a function of siloxane chain length, sol-like, gel-like and clay-like appearances of the constituted ER fluids were observed. Different functional-group-terminated silicone oils were also employed as the dispersing media. Significant differences of yield stress were found. We systematically study the effect of siloxane chain lengths on the permeability of oils traveling through the porous spaces between the particles (using the Washburn method), oils adsorbed on the particles' surface (using FT-IR spectra), as well as their particle size distribution (using dynamic light scattering). Our results indicate the hydrogen bonds are instrumental in linking the silicone oil to GER solid particles, and long chain lengths can enhance the agglomeration of the GER nanoparticles to form large clusters. An optimal oil structure, with hydroxyl-terminated silicone oil and a suitable viscosity, was chosen which can create the highest yield stress of ∼300 kPa under a 5 kV mm(-1) DC electric field.