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An ultra-sensitive and transparent piezoresistive pressure sensor based on a sea-urchin shaped metal nanoparticle (SSNP)-polyurethane (PU) composite with microdome arrays is successfully fabricated for the first time. The piezoresistive pressure sensor with microdome arrays was prepared using a nanoimprinting process based on an intermediate polymer substrate (IPS) replica mold. It showed a superior sensitivity (71.37 kPa-1) and a high optical transmittance (77.7% at 550 nm) due to the effective quantum tunneling effect even at small concentrations of conductive SSNP filler (6 mg mL-1). The high-performance characteristics of the piezoresistive pressure sensor are attributed to the geometric effects of the microdome structure, especially the stress concentration at small contact spots and the deformation of the contact area. The piezoresistive pressure sensor with microdome arrays also exhibited a fast response/relaxation time (30 ms), ultra-low pressure detection (4 Pa), and excellent long-term stability under harsh conditions. In addition, the effectiveness of the piezoresistive pressure sensors in various sensing applications including sensing mapping, human arterial pulse monitoring, and the detection of muscle movement is also successfully demonstrated. It is anticipated that this novel transparent pressure sensor based on a SSNP-PU composite with microdome arrays will be a key component in the development of integrated transparent sensing applications.

This paper presents flexible piezoelectric micromachined ultrasonic transducers (PMUT) on thin polymer substrate. The flexible PMUT is based on AIN piezoelectric thin film with a new structural configuration optimized for flexibility. The measured resonant frequency, effective coupling coefficient and displacement sensitivity are 2.58 MHz, 1.42% and 30 nm/V, respectively, which are on par with those of a conventional PMUT on a silicon substrate. The flexible PMUT introduced in this work will find new applications in medical imaging, therapeutics, surgery, industry and consumer electronics, thanks to the potential merits of mechanical compliance, light weight, small element size, large array area and high integration level.

Microbubble fabrication of poly(dimethylsiloxane) (PDMS) beads with incorporated TiO2 provides a low-density, microstructured photocatalyst that is buoyant in water. This approach surmounts many of the challenges traditionally encountered in the generation of buoyant photocatalysts, an area which is critical for the implementation of widespread environmental cleaning of organic pollutants in water resources. Because the incorporation into the polymer bead surface is done at low temperatures, the crystal structure of TiO2 is unaltered, ensuring high-quality photocatalytic activity, while PDMS is well-established as biocompatible, temperature stable, and simple to produce. The photocatalyst is shown to degrade methylene blue faster than other buoyant, TiO2-based photocatalysts, and only an order of magnitude less than direct suspension of an equivalent amount of photocatalyst in solution, even though the photocatalyst is only present at the surface of the solution. The reusability of the TiO2/PDMS beads is also strong, showing no depreciation in photocatalytic activity after five consecutive degradation trials.

We report a flexible sensor array electronic tongue system that is fabricated on a polymer substrate by the laser direct writing process for multiflavor detection. Electronic tongue is a sensing system that is applied to detect different elements with the same sensor array. By analyzing responses from different measurement units, it enables a cross-sensitivity, namely, the ability of the system to responding to a range of different analytes in solution without specific functionalization of sensors. In this article, a six-unit sensing array system was fabricated by a laser direct writing process. Sensing units were introduced on a flexible polyamide surface. A high surface-volume ratio porous carbon structure was created by a laser-induced carbonization process, which provides stable conductive carbon electrodes with high sensitivity. Different surface treatments, such as gold plating, reduced-graphene oxide coating, and polyaniline coating, were accomplished for different measurement units. By applying principal component analysis, this sensing system shows a promising result for the detection of multiple flavors. The detection limit for each element is about 0.1 mM for NaCl and sugar solutions. Also, it is able to detect 10

Organic based materials and devices for flexible electronics are recognized as a promising field and application while they also have significant disadvantages such as low charge transport, process temperature limitation, and etc. Those limitations, based on material itself, make the flexible electronic device very difficult to compete with Si-based rigid electronics that have excellent device performance and much advanced design rule. However, the rigid Si based devices are also vulnerable to any types of mechanical stress when they are in use for the flexible applications. Thus, we strongly feel the need to combine benefits from the organic based flexile devices and from the Si based rigid devices by attaching the rigid thin chips on the flexible substrates such as PI (Polyimide), PET (Polyethylene phthalate) and PDMS (Polydimethylsiloxane) which is accepted as a new or future trend for the next generation of the electronic devices. In order to achieve this new concept, thin device $(\le50 \mu ${m) showing high device performance needs to be attached on the surface of deformable substrates to construct flexible electronic device circuits and it is required to interconnect the thin Si based chip with the flexible polymer substrate. For this specific interconnection, we utilized an ElectroHydroDynamic (EHD) micro-patterning system which is not damaging the flexible substrate unlike the conventional wire bonding method that mechanically damages during the bonding process. To form narrow Ag based metal interconnections, we optimized various experimental parameters (flow rate [$\mu $l/min], applying voltage [kV], working distance [㎛], jetting velocity and acceleration [mm/s, mm/s2]) and the metal lines were sintered at 150 oC for 30 mins to remove any solvent contained in the solution based Ag ink. As a result, we expect that this work will contribute to the fabrication of 3D devices on the flexible substrate that uses the Si based thin chip interconnected by the narrow Ag based metal lines.

Mechatronic integrated devices (MID) enable the combination of electrical, mechanical, thermal and optical functions within one component. The three-dimensional circuitries can be applied to a polymer substrate by means of LPKF laser-direct-structuring (LDS). For this, the matrix polymer is filled with a special additive, enabling laser activation and subsequent metallization. In order to reduce the thermo-mechanical stress in the polymer-metal composite, high levels of inorganic fillers are added to the polymer compound to improve its coefficient of thermal expansion. At the same time, the fillers affect the metallization behavior as well as the metal adhesion as a key property for the reliability of MID. In this work, the extent to which talc affects the adhesion of the metallization was investigated by the hot-pin-pull-test. An increase in the metal adhesion was achieved by adding varying amounts of talc platelets (diameter 7 μm) to a PA10T-based copolyamide filled with 4 and 8 wt.-% LDS-additive. The specimen were further characterized using a scanning electron microscope (SEM). The results indicate that the increased adhesion is caused by mechanical anchoring of the metallization among the protruding talc platelets.

Microscale local strain gauges with low-power consumption and large strain range were demonstrated by integrating microdisk lasers in a deformable and flexible polymer substrate. The lasing spectra of microdisk lasers were sensitive to substrate deformation and can be modulated by strains. The measured relative wavelength tuning under strains of the novel strain sensors illustrated a linear behavior with the gauge factor being ~4.0 nm and ~6.7 nm per stretching unit for microdisk lasers with the diameter of 1.2 μm and 1.5 μm, which corresponding to a smooth wavelength tuning of 1.5 nm and 2.6 nm under 36% strain, respectively. In addition, to being used as microscale strain gauges, the visible lasers on the deformable substrate can also function as a tunable light source for the photonic integrated circuits and flexible laser projection displays.

Surface-assisted laser desorption ionization (SALDI) is an approach for gas-phase ion generation for mass spectrometry using laser excitation on typically conductive or semiconductive nanostructures. Here, we introduce insulator nanostructure desorption ionization mass spectrometry (INDI-MS), a nanostructured polymer substrate for SALDI-MS analysis of small molecules and peptides. INDI-MS surfaces are produced through the self-assembly of a perfluoroalkyl silsesquioxane nanostructures in a single chemical vapor deposition silanization-step. We find that surfaces formed from the perfluorooctyltrichlorosilane monomer assemble semielliptical features with a 10 nm height, diameters between 10 and 50 nm, and have attomole-femtomole sensitivities for selected analytes. Surfaces prepared with silanes that either lack the trichloro or perfluoro groups, lack sensitivity. Further, we demonstrate that hydrophobic INDI regions can be micropatterned onto hydrophilic surfaces to perform on-chip self-desalting in an array format.

Herein, a novel stretchable Cu conductor with excellent conductivity and stretchability is reported via the flash‐induced multiscale tuning of Cu and an elastomer interface. Microscale randomly wrinkled Cu (amplitude of ≈5 µm and wavelength of ≈45 µm) is formed on a polymer substrate through a single pulse of a millisecond flash light, enabling the elongation of Cu to exceed 20% regardless of the stretching direction. The nanoscale interlocked interface between the Cu nanoparticles (NPs) and the elastomer increases the adhesion force of Cu, which contributes to a significant improvement of the Cu stability and stretchability under harsh yielding stress. Simultaneously, the flash‐induced photoreduction of CuO NPs and subsequent Cu NP welding lead to outstanding conductivity (≈37 kS cm−1) of the buckled elastic electrode. The 3D structure of randomly wrinkled Cu is modeled by finite element analysis simulations to show that the flash‐activated stretchable Cu conductors can endure strain over 20% in all directions. Finally, the wrinkled Cu is utilized for wireless near‐field communication on the skin of human wrist.

International audience; The possibility to impart surface properties to any polymeric substrate using a fast, reproducible, and industrially friendly procedure, without the need for surface pretreatment, is highly sought after. This is in particular true in the frame of antibacterial surfaces to hinder the threat of biofilm formation. In this study, the potential of aryl‐azide polymers for photofunctionalization and the importance of the polymer structure for an efficient grafting are demonstrated. The strategy is illustrated with a UV‐reactive hydrophilic poly(2‐oxazoline) based copolymer, which can be photografted onto any polymer substrate that contains carbon–hydrogen bonds to introduce antifouling properties. Through detailed characterization it is demonstrated that the controlled spatial distribution of the UV‐reactive aryl‐azide moieties within the poly(2‐oxazline) structure, in the form of pseudogradient copolymers, ensures higher grafting efficacy than other copolymer structures including block copolymers. Furthermore, it is found that the photografting results in a covalently bound layer, which is thermally stable and causes a significant antiadherence effect and biofilm reduction against Escherichia coli and Staphylococcus epidermidis strains while remaining noncytotoxic against mouse fibroblasts.

International audience; [FeII(Htrz)2(trz)](BF4) spin crossover particles of 85 nm mean size are dispersed in an SU‐8 polymer matrix and spray‐coated onto silicon microcantilevers. The subsequent photothermal treatment of the polymer resist leads to micrometer thick, smooth, and homogeneous coatings, which exhibit well‐reproducible actuation upon the thermally induced spin transition. The actuation amplitude as a function of temperature is accurately determined by combining integrated piezoresistive detection with external optical interferometry, which allows for the assessment of the associated actuation force (9.4 mN), stress (28 MPa), strain (1.0%), and work density (140 mJ cm−3) through a stratified beam model. The dynamical mechanical characterization of the films evidences an increase of the resonance frequency and a concomitant decrease of the damping in the high‐temperature phase, which arises due to a combined effect of the thickness and mechanical property changes. The spray‐coating approach is also successfully extended to scale up the actuators for the centimeter range on a polymer substrate providing perspectives for biomimetic soft actuators.

As nanotechnology has developed, the creation of nanostructured surfaces has garnered attention for their uses in sensing and catalysis applications. These are however often expensive, time-consuming, and difficult to produce. In contrast, this investigation is focused on the inexpensive, environmentally friendly and fast technique of Confined Atmospheric Pulsed laser deposition (CAP). The CAP technique has these advantages because it is an atmospheric laser-based direct deposition technique. Herein, the CAP process is examined in an effort to better understand the process and to begin determining the means to control the properties of the nanostructured surfaces produced by varying the laser fluence and the scan strategy during the ablation. During this investigation, a Nd:YAG laser was applied to deposit gold nanostructures directly onto a polymer substrate. The plasmonic properties and morphologies of the surfaces were examined using UV–Vis spectroscopy and Scanning Electron Microscopy (SEM) respectively. A mathematical model was developed to describe the size and dispersity of the structures deposited and the variation of the position and size of the spectral plasmon peaks in response to the sample processing parameters, with the aim of allowing for a degree of control over these properties and gaining some understanding of the mechanism of this deposition process.

This paper presents the development of a chemical sensor which was microfabricated on top of liquid crystal polymer (LCP) substrate. As a result of the unique material properties of LCP, the sensor showed favorable flexibility as well as operational reliability. These features demonstrate potential for integration of the sensor into automated sensing vehicles to achieve real-time detection. The sensor consists of a gold working electrode, a silver/silver chloride reference electrode, and a gold counter electrode. The working electrode of the sensor was further modified with bismuth nanoparticles and Nafion. The modified sensor exhibited a significantly enhanced sensing capability toward cadmium metal ion (Cd(II)) in comparison to the unmodified one. The effects of deposition potential and deposition time on the sensing performance of the sensor were extensively investigated through electrochemical experiments. With optimized parameters, the sensor was capable of quantifying Cd(II) in the concentration range of 0.3 to 25 &micro, g/L. The minimum Cd(II) concentration detected by the sensor was 0.06 &micro, g/L under quiescent deposition. The obtained results suggest that the proposed sensor has a great potential to be deployed for in-situ Cd(II) determination.

International audience; Highly flexible lead zirconate titanate, Pb(Zr,Ti)O3 (PZT), thin films have been realized by an all chemical process on a plastic substrate. The procedure is composed of three steps: the first one is the PZT deposition on aluminium thin substrate, the second step corresponds to the bonding PZT thin film to a polymer layer and the final step is the aluminium substrate etching. Diffractions and microscopy techniques were used to check the quality of the new PZT/polymer composite structure. Polarization hysteresis and permittivity measurements were also performed to determine the electrical characteristics of the composite. These results demonstrate that the recently developed PZT/polymer thin films are very attractive for both bending actuation and sensing as well as for low frequency vibrating energy harvesting applications.

The long-term thermal performance of vacuum insulation panels (VIP) is brought by the capacity of their barrier envelope to maintain the core material under vacuum. This study is focused on the detailed modelling of gas transfer through the defects of aluminium-coated polymer films used for VIPs’ envelopes. The 3D simulations were performed with monolayer and multilayer metal-coated polymer films. They have been carried out in dynamic conditions with the SYRTHES® software developed by EDF R&D. The results show that the water vapour and air permeations through a monolayer film slightly depend on the polymer substrate thickness, diffusivity and solubility, but primarily, on the defects geometry and arrangement. Regarding multilayer films, the permeation can be deduced from the ideal laminate theory. We are now able to provide and operate a numerical model, which can calculate the permeance of monolayer or multilayer metallized polymer films as a function of the coating quality and the geometry of the layers. Even if calculated permeances are ten times higher than measurements, this study improves our understanding of gas transports through VIPs’ barrier envelope and allows to manage more efficiently the relations between the films microstructures and their overall permeability. This paper is split into 6 parts: physical phenomena, methodology and modelling tools, simulation results, experiments and model validation and then, discussion and conclusion.

Cold spray has been proved a viable method for metallization of polymers and polymer composites. It has been reported that the mechanism of cold spray on polymeric substrates is different from the conventional mechanism on metallic substrates (i.e. adiabatic shear instability). In this work, single particle impact experiments were performed on polymeric substrates as well as mild steel. The particle-substrate interactions on different substrates were analyzed. Based on the results, the mechanism of cold spray on polymeric substrates is discussed and compared to that on metallic substrates., 2018 International Thermal Spray Conference, May 7-10, 2018, Orlando, FL, USA

Electroplating of nanoporous Pt (nPt) induces an extremely strong tensile stress, which results in the exfoliation of nPt on flexible polymer substrate despite plasma treatment to improve adhesion. Here, we overcame this challenge by modifying flexible stainless-steel, and developed wearable, robust, flexible, and non-enzymatic continuous glucose monitoring system. The flexible stainless-steel was highly effective in improving the adhesion between the metal layer and substrate. The developed wireless system included electrochemical analysis circuits, a microcontroller unit, and a wireless communication module. Finally, we evaluated the continuous glucose monitoring system through two animal testing, by implanting into subcutaneous tissue and measuring interstitial fluid (ISF) glucose values at 5-15-min intervals. Comparison of the measured ISF glucose with blood glucose determined by the Clarke error grid analysis showed that 82.76% of the measured glucose was within zone A. Furthermore, the wearable glucose sensor exhibited bio-compatible to implant through various bio-compatibility tests.

Windows whose transmittance can be modified by an applied voltage have previously been fabricated from soft, transparent elastomers sandwiched between ITO coated glass and a compliant, silver nanowire top electrode.1 In this contribution we extend the capabilities of the tunable window so that the optical transmittance can be varied spatially over the window according to voltage signals applied to different segments of the back electrode of the window, defined by patterning of individually addressable electrodes. The actuation signals are controlled using TTL-level input signals applied to high voltage switches. We also show that the spatially tunable window can be fabricated on a flexible substrate, such as PET, and the optical transmittance is not affected by bending of the substrate. The use of a polymer substrate not only increases possible applications of this class of voltage controlled light modulation device but also has the potential of reducing cost at an industrial scale by replacing more costly ITO coated glass substrate.

One major barrier to advancing fundamental studies of biological cargoes for clinical use has been effective delivery into the cytoplasm. Available methods such as electroporation, viral techniques, and liposomal reagents come with respective strengths and weaknesses depending on the application needs. We present a laser-based cargo delivery platform that combines 11-ns laser pulses and structured flexible polymer substrates to create transient pores in the plasma membrane of cells. Cells are grown on the substrates, and pores are induced form on the cells in the regions excited with nanosecond laser pulses—thus, allowing treatment selectivity in a population. The medium surrounding the cell contains the delivery cargoes in solution, and cargoes diffuse into the cell before the transient pores are sealed. Polymer-based substrates are a promising material for laser-based delivery methods because they are low-cost, have flexible spatial movements, and have simple fabrication techniques. We deliver cargos of various sizes. We use fluorescence imaging and flow cytometry to quantify the delivery efficiency and viability in a reproducible manner. We obtain delivery efficiencies of up to 40% with viabilities of 60% for calcein green in adherent cells such as HeLa and Panc-1. We also deliver molecules of up to 40 kDas and siRNA. We use scanning electron microscopy to study cell adherence and substrate surface morphology. Our data shows that polymer-based substrates can deliver biological material directly into cells in a cost-effective manner.

A rapid prototyping process was presented to fabricate a nylon honeycomb microstructure coated with parylene C. The surface structure was designed to obtain a hydrophobic surface using the volume of fluid (VOF) model. With the micro-molding technique, the contact angle of the polymer surface could be designed and fabricated by changing the different microstructure surface die-steel mold inserts. For the honeycomb (20 μm width and 60 μm depth) microcavity side wall, an average micro-molding filling percentage of 95% could be achieved by using a three-section constant-pressure molding process. The solid surface wettability is governed by both the geometrical microstructures and the surface energy. A 2 μm parylene C layer was deposited on the nylon honeycomb microsurface to reduce the surface energy. To design honeycomb structures with different microcavity densities, the contact angle of these artificial surfaces could change from 91° to 130°. From a comparison of the contact angle measurements with the different models, the honeycomb-structured microsurface could be described by the Cassie–Baxter model. The errors between the VOF simulation and the measured data were

The advantages of additive manufacturing for electronic devices have led to the demand of printing functional material in search of a replacement for the conventional subtractive fabrication process. Zinc oxide (ZnO), thanks to its interesting properties for the electronic and photonic applications, has gathered many attentions in the effort to fabricate functional devices additively. Although many potential methods have been proposed, most of them focus on the lowtemperature processing of the printed material to be compatible with the polymer substrate. These low-temperature fabrication processes could establish a high concentration of defects in printed ZnO which significantly affect the performance of the device. In this study, ZnO thin film for UV photodetector application was prepared by inkjet printing of zinc acetate dihydrate solution following by different heat treatment schemes. The effects of annealing to the intrinsic defect of printed ZnO and photoresponse characteristics under UV illumination were investigated. A longer response/decay time and higher photocurrent were observed after the annealing at 350°C for 30 minutes. X-ray photoelectron spectroscopy (XPS) analysis suggests that the reducing of defect concentration, such as oxygen vacancy, and excess oxygen species in printed ZnO is the main mechanism for the variation in photoresponse. The result provides a better understanding on the defect of inkjet-printed ZnO and could be applied in engineering the properties of the printed oxide-based semiconductor.

This work is concerned with the long-term behavior of environmentally-assisted subcritical cracking of PECVD SiNx barrier films on polyethylene terephthalate (PET) and polyimide (PI) substrates. While environmentally-assisted channel cracking in SiNx has been previously demonstrated, with constant crack growth rates over short periods of time (in-situ microscopy and finite-element modeling results highlight the combined effects of neighboring cracks and substrate cracking on the crack growth rate evolution in the film. In most cases, the subcritical crack growth rates decrease over time by up to two orders of magnitude until steady-state rates are reached. For SiNx on PI, crack growth rates were found to be more stable over time due to the lack of crack growth in the substrate as compared to SiNx on PET. These results provide a guideline to effectively improving the long-term reliability of flexible barriers by a substrate possessing high strength which limits substrate damage.

To ensure good adhesion between a 200 nm thick silicon dioxide layer and a 4.5 μm thick hardcoat polymeric coating, a better understanding of mechanisms of adhesion at this interface is needed. To reach this purpose, focus is placed on two axes: characterizing mechanical properties of materials composing the system and in parallel, finding an applicable and effective method to quantify adhesion. Small dimension of SiO2 thin film makes it challenging to accurately characterize it. Hence the use of both nano-indentation and AFM to attempt assessment of SiO2 thin film elastic modulus Ef; taking into account limitations and uncertainty associated with each technique. Elastic modulus of SiO2 thin film determined by nano-indentation is roughly 50 GPa on a wafer substrate and 15 GPa on a lens substrate. As for AFM, modulus measured is approximately 56 GPa on a wafer substrate and 22 GPa on a lens substrate. This highlights significant influence of substrate for both techniques. Impact on mechanical properties between SiO2 thin films under different intrinsic stresses was also investigated. Results suggest that higher density of SiO2 thin film leads to higher elastic modulus. To quantify adhesion, micro-tensile and micro-compression tests were performed. Micro-tensile experiments give ultimate shear strengths of hardcoat-substrate interface ranging from 9 to 14 MPa. Values of energy release rates of SiO2 / Hardcoat, range from 0.1 J/m² to 0.5 J/m², depending on moduli values found on wafer or lens substrate

Microfluidic chips known as μ-TAS or LoC have become versatile tools in cell research, since functional biochips are able to streamline dynamic observations of various cells. Glass or polymers are generally used as the substrate due to their high transparency, chemical stability and cost-effectiveness. However, these materials are not well suited to the microscopic observation at the fluid boundary due to the refractive index mismatch between the medium and the biochip material. For this reason, we have developed a method of fabricating three-dimensional (3D) microfluidic chips made of a low refractive index fluoric polymer CYTOP. CYTOP has a refractive index of 1.34, a value that is almost equivalent to that of water. This optical property is very important for clear 3D microscopic observations of cell motion near the solid boundary, due to the minimal mismatch between the refractive index values of the medium and the CYTOP substrate. Therefore, CYTOP microfluidics are expected to allow the generation of clear images of unique cell migratory processes near the microfluidic sidewall. Therefore, we established the fabrication procedure involving the use of femtosecond laser direct writing, followed by wet etching and annealing, to create high-quality 3D microfluidics inside a polymer substrate. A microfluidic chip made in this manner enables us to more clearly observe areas near the fluid surface, compared to the observations possible using conventional microfluidic chips.

Plasma treatment of soft polymers is a promising technique to improve biomedical properties of the materials. The response to the deformation of such materials is not yet clear. Soft elastic polyurethane treated with plasma immersion ion implantation is subjected to fatigue uniaxial loading. The influence of the strain amplitude and the plasma treatment regime on damage character is discussed. Surface defects are studied in unloaded and stretched states of the material. As a result of fatigue loading, transverse cracks (with closed overlapping edges as well as with open edges deeply propagating into the polymer) and longitudinal folds which are break and bend inward, appear on the surface. Hard edges of cracks cut the soft polymer which is squeezed from the bulk to the surface. The observed damages are related to the high stiffness of the modified surface and its transition to the polymer substrate.

An Optical Frequency Domain Reflectometry (OFDR) based fiber optic sensor scheme &ldquo, embedded&rdquo, in concrete for the purpose of structural health monitoring (SHM) of carbon concrete composites (C3) is presented. The design, while strengthening the concrete structure, also aims to monitor common SHM parameters such as strain and cracks. This was achieved by weaving the carbon fiber together with optical fiber, based on a specialized technique that uses an embroidery setup where both the carbon and optical fiber are woven on a water dissolvable polymer substrate. The performance of the sensing scheme was characterized in-situ utilizing the OFDR based technique and the results presented. The sensors embedded on a custom made concrete block were subjected to varying strain via a three point bending test to destruction and the results discussed. The intended dual-achievement of the scheme thus proposed in SHM and strengthening the C3 is demonstrated. The suitability of the OFDR scheme for C3 is combined with a fibre Bragg grating (FBG)-based approach, and discussed in detail.

We present a method for virtual unrolling of a thin rolled object. From a volumetric image of the rolled object we obtain a flat image of the object’s surface, which allows visualinspection of the object and has a number of applications. Our method exploits the geometric constrains of the problem and detects a single rolled surface. For surface detection we adapt a solution to an optimal net surface problem, previously used for terrain-like and tubular surfaces. We present our approach on an example of a rolled sheet of microelectronic, which has a layer of flexible polymer substrate and a thin metal layer lithographically coated onto the polymer. Our approach is automatic and robust. The unrolled image is undistorted, and the surface structures may be accurately quantified making our approach a good candidate for an industrial application of virtual unrolling

Chameleons are masters of light, expertly changing their color, pattern, and reflectivity in response to their environment. Engineered materials that share this tunability can be transformative, enabling active camouflage, tunable holograms, and novel colorimetric medical sensors. While progress has been made in creating artificial chameleon skin, existing schemes often require external power, are not continuously tunable, and may prove too stiff or bulky for applications. Here, a chemically tunable, large-area metamaterial is demonstrated that accesses a wide range of colors and refractive indices. An ordered monolayer of nanoresonators is fabricated, then its optical response is dynamically tuned by infiltrating its polymer substrate with solvents. The material shows a strong magnetic response with a dependence on resonator spacing that leads to a highly tunable effective permittivity, permeability, and refractive index spanning negative and positive values. The unity-order index tuning exceeds that of traditional electro-optic and photochromic materials and is robust to cycling, providing a path toward programmable optical elements and responsive light routing., Part of this work was performed at the Stanford Nano Shared Facilities and the Stanford Nanofabrication Facility. D.M.W. acknowledges support from a Gabilan Stanford Graduate Fellowship and a National Science Foundation Graduate Research Fellowship. M.L.S. acknowledges support from by the Department of Defense through the National Defense Science & Engineering Graduate Fellowship Program. J.A.D. acknowledges a National Science Foundation CAREER Award (DMR-1151231). D.M.W., M.L.S., and G.V.N. were supported as part of the DOE “Light-Material Interactions in Energy Conversion” Energy Frontier Research Center under grant DE-SC0001293, which also funded materials, fabrication, and measurements.

Developing facile and mild strategy to construct multi-enzymes immobilization system has attracted considerable attentions in recent years. Here a simple immobilization strategy called visible light induced graft polymerization that can simultaneously and separately encapsulate two kinds of enzymes on one polymer film was proposed. Two incompatible enzymes, trypsin and transglutaminase (TGase) were selected as model dual-enzymes system and simultaneously immobilized on two sides of low-density polyethylene (LDPE) film. After immobilization, it was found that more than 90% of the enzymes can be embedded into dual-enzymes loaded film without leakage. And the activities of both separately immobilized enzymes were higher than the activities of mixed co-immobilized enzymes or the sequential immobilized ones. This dual-enzymes loaded film (DEL film) showed excellent recyclability and can retain >87% activities of both enzymes after 4 cycles of utilization. As an example, this DEL film was used to conjugate a prodrug of cytarabine with a target peptide. The successful preparation of expected product demonstrated that the separately immobilized two enzymes can worked well together to catalyze a two-step reaction. Accepted version

For the first time in atmospheric pressure-plasma enhanced chemical vapour deposition of amorphous silica onto flexible polymer substrates, pinholes have been visibly detected using interferometric microscopy and their average diameter of 1.7 μm calculated. Pinholes were found to control the water vapour transmission rate of all 30 nm films deposited with input energies greater than 9 keV per precursor molecule, thus presenting an opportunity for the synthesis of single layer thin films with precisely targeted permeation rates. The pinholes themselves were understood to originate from interactions between the polymer substrate and filaments in the plasma. The non-uniformity of the discharge was attributed to the reduced concentrations of precursor tetraethyl orthosilicate and oxygen species necessary to deposit amorphous silica at high specific energies.

Compact visible microdisk lasers consisting of InGaP/ InGaAIP multi-quantum wells were fabricated and embedded in a deformable polydimethylsiloxane (PDMS) polymer substrate. In addition to very small device footprint and low-threshold, the wavelength of microdisk lasers can be linearly fine-tuned by stretching the flexible substrate. A smooth wavelength tuning of 1.5 nm and 2.6 nm for microdisk lasers with the diameter of 1.2 μm and 1.5 μm are demonstrated under 36% strain, respectively. The compact tunable visible microdisk lasers can not only function as a novel light source for photonic integrated circuits but also sensitive and skin-attachable gauges in local index and strain detection for stretchable electronics.

A stretchable multisensor system is successfully demonstrated with an integrated energy-storage device, an array of microsupercapacitors that can be repeatedly charged via a wireless radio-frequency power receiver on the same stretchable polymer substrate. The integrated devices are interconnected by a liquid-metal interconnection and operate stably without noticeable performance degradation under strain due to the skin attachment, and a uniaxial strain up to 50%.

We report a novel approach for the fabrication of a user friendly functional device with dry electrodes for the measurement of biopotentials (electrocardiograph or ECG, electroencephalogram or EEG) that allows extended measurement time, reduced preparation time and less motion induced artifacts compared to wet gel based commercial electrodes. The dry micro-electrode arrays were fabricated by the UV maskless lithography in the grayscale or back-exposure modes using a biocompatible polymer SU-8. This produced conical shaped, mechanically robust micro-needles on a flexible polymer substrate which conforms to the body contours thereby greatly reducing the motion artifacts. The device was tested in vivo on human subjects and compared with the currently utilized wet gel based Ag/AgCl electrodes. It demonstrated comparable performance in capturing ECG and EEG signals. The electrodes were tested for long duration (48 h) without any signs of degradation. This device can be utilized for long term as well as remote health monitoring of the subjects.

Finding ways to pattern indium-tin-oxide (ITO) thin films attached with flexible polymer plays an important role in manufacturing a large variety of photonic/optical devices including flexible display panels. This paper demonstrates femtosecond laser assisted selective removal of a thin layer of ITO coating deposited on a flexible polymer substrate. We utilize both flat-top and Gaussian shape beams to pattern micro/nano-metric grooves on ITO thin films disallowing any damage on the polymer substrate. The flat-top beam enables us to print rectangular profile grooves on ITO-coated polymer substrate. We also investigate the influence of objective lens and galvanometer scanner on the size and shape of the grooves on ITO thin films. Furthermore, we determine the ablation thresholds for selective patterning of ITO coating under various irradiation conditions. In addition, we achieved nano-grooves of width down to 570 nm, which has been reported for the first time in this paper. The engraved micro/nano-scale grooves on OTO thin films show excellent electrical isolation from the remaining ITO thin film. The femtosecond laser assisted fabrication technology exhibits a unique scheme for machining numerous patterns on ITO thin films with great flexibility.

This work investigates the film removal properties of 30 nm thick Indium Tin Oxide (ITO) thin films, on flexible polyethylene terephthalate (PET) substrates, using 355, 532 and 1064 nm nanosecond pulses (ns), and 343 and 1064 nm femtosecond pulses. The ablation threshold was found to be dependent on the applied wavelength and pulse duration. The surface topography of the laser induced features were examined using atomic force microscopy across the range of wavelengths and pulse durations. The peak temperature, strain and stress tensors were examined in the film and substrate during laser heating, using finite element computational methods. Selective removal of the thin ITO film from the polymer substrate is possible at all wavelengths except at 266 nm, were damage to substrate is observed. The damage to the substrate results in periodic surface structures (LIPPS) on the exposed PET, with a period of twice the incident wavelength. Fragmented crater edges are observed at all nanosecond pulse durations. Film removal using 1030 nm femtosecond pulses results in clean crater edges, however, minor 5 nm damage to the substrate is also observed. The key results show that film removal for ITO on PET, is through film de-lamination across all wavelengths and pulse durations. Film de-lamination occurs due to thermo-elastic stress at the film substrate interface region, as the polymer substrate expands under heating from direct laser absorption and heat conduction across the film substrate interface.

Remarkable developments and successes are witnessed in the fabrication and implementation of optical sensors based on localized surface plasmon resonance (LSPR) for the investigation of chemical and biological material quantities. We report on the reproducible fabrication of chemically stable surface immobilized AuNPs grown via organometallic chemical vapor deposition (OMCVD) on a polymer substrate, namely polystyrene (PS). Oxygen plasma-treated and UV ozone-treated PS samples depict enhanced amounts of polar -OH groups allowing for nucleation and growth of AuNPs. The optimum plasma treatment conditions, the largest shifts in the LSPR curves, and the bulk sensitivity of the OMCVD-grown AuNPs are discussed.

Metal thin film electrodes on flexible polymer substrates are inherently unstable against humidity and mechanical stresses because of their poor adhesion properties. We introduce a novel approach for improving the adhesion characteristics of metal-polymer interface based on the nanostructuring of the polymer substrate by using nanoimprint lithography. The adhesion characteristics of metal-polymer interface were measured by accelerated test, cyclic bending test and double cantilever beam (DCB) test. The interface of Au/Ti dual layer thin film and nanoimprinted PMMA substrate shows over 2.03 and 1.95 times higher adhesion energy (G(c)) than that of Au/Ti dual layer thin film and plane PMMA substrate in air and wet environments, respectively. The adhesion energy between metal thin film and polymer substrate was dramatically improved by the increased surface roughness and mechanical interlocking effect of numerous nanoscale anchors at the edges of nanoimprinted surface, which was verified by both experiment and numerical analysis.

Hybrid structures of graphene and metal nanoparticles (NPs) have been actively investigated as higher quality surface enhanced Raman spectroscopy (SERS) substrates. Compared with SERS substrates, which only contain metal NPs, the additional graphene layer provides structural, chemical, and optical advantages. However, the two-dimensional (2D) nature of graphene limits the fabrication of the hybrid structure of graphene and NPs to 2D. Introducing three-dimensionality to the hybrid structure would allow higher detection sensitivity of target analytes by utilizing the three-dimensional (3D) focal volume. Here, we report a mechanical self-assembly strategy to enable a new class of 3D crumpled graphene-gold (Au) NPs hybrid nanoplasmonic structures for SERS applications. We achieve a 3D crumpled graphene-Au NPs hybrid structure by the delamination and buckling of graphene on a thermally activated, shrinking polymer substrate. We also show the precise control and optimization of the size and spacing of integrated Au NPs on crumpled graphene and demonstrate the optimized NPs' size and spacing for higher SERS enhancement. The 3D crumpled graphene-Au NPs exhibits at least 1 order of magnitude higher SERS detection sensitivity than that of conventional, flat graphene-Au NPs. The hybrid structure is further adapted to arbitrary curvilinear structures for advanced, in situ, nonconventional, nanoplasmonic sensing applications. We believe that our approach shows a promising material platform for universally adaptable SERS substrate with high sensitivity.

This study investigates the influence of various factors on the ductility of thin metal films on polymer substrates through structural modeling of these polymer-supported metal films using finite element analysis software ABAQUS. The various system parameters include the thickness of the film h, the thickness of the polymer substrate H, the thickness ratio between the film and substrate h/H and the Young’s modulus of the substrate Es. The results demonstrate that each parameter influences the ductility of films except the thickness ratio between the film and substrate h/H. Furthermore, an orthogonal experiment is performed to analyze the combined action of the parameters on the ductility of polymer-supported metal films. It can be concluded that the most dominating factor that influences the ductility of films on polymer substrate is the thickness of the thin metal film h, while the Young’s modulus of the substrate while Es plays a secondary role.

NiCr, Mo, and Mo-N thin copper diffusion barrier films are deposited on 200 um thick polyimide films spin-coated on glass substrates by dc reactive magnetron sputtering. The adhesion forces for three systems are measured by micro-scratch test analysis depending on oxygen plasma pretreatment, sputtering power density, moisture contents, and post annealing treatment. The values of adhesion forces for the three systems are linearly proportional to the oxygen plasma treatment time. As deposition power density increases, measured adhesion forces also increase. The existence of moisture adsorbed in the polymer substrate prior to initiating the sputtering process significantly reduces the adhesion force for all systems. Post annealing treatment at 150 degrees C for 12 hours after sputtering also deteriorates the adhesion between the barrier films and polymer substrate. Auger electron spectroscopy reveals that adhesion forces are significantly dependent on the types of compounds formed at the barrier layer/polymer interface. Changes in the adhesion properties of the MoN system as a function of the nitrogen content are explained in terms of the mechanical stability of the MoN(x)O(y) interface layer on the polymer substrate.

Bilayer plasma polymer (PP) films were examined using a combination of X-ray and neutron reflectometery and X-ray photoelectron spectroscopy to gain an understanding of the interfacial structures that form between the films. Three different PP films were produced from the monomers hexamethyldisiloxane (HMDSO), di(ethylene glycol) dimethyl ether (DG), and allylamine (AA) at different load powers. These films were used as "substrates" for the subsequent deposition of a deuterated DG (dDG) PP top film. The width of the interfacial region was found to be strongly dependent on the chemical and physical properties of the substrate film. These findings have relevance to the general use and application of plasma polymer films. We examine the effect of load power and monomer chemistry on the interface that forms between a plasma polymer substrate and a deuterated plasma polymer top film.

Single and multilayer (SiO2, TiO2, SiO2–TiO2, TiO2/SiO2–TiO2/SiO2) films were deposited on polymer substrate poly-methyl methacrylate (PMMA) at room temperature by sol–gel method. Optical micrographs show that spin-coated nanoparticle thin films have homogeneous surface with good adhesion with PMMA substrate. Scanning electron microscope results show good incorporation of silica and titania particles as composites with small grain size within range of 0.2–1.28 µm. The structural characterization was carried out by X-ray diffraction, which shows an amorphous pattern for SiO2, SiO2–TiO2 and TiO2/SiO2–TiO2/SiO2 samples but shows semicrystalline behavior in TiO2 sample. From UV–visible spectroscopy, it is found that coated films have a good optical transparency with tunable refractive index of 1.39–2.14. So, these films can be useful for various potential optical applications.

Aluminum doped ZnO (AZO) and pure ZnO thin films are grown on polymer substrates by pulsed-laser deposition and the optical, electrical, and structural film properties are investigated. Laser fluence, substrate temperature, and oxygen pressure are varied to obtain transparent, conductive, and stoichiometric AZO layers on polyethylene terephthalate (PET) that are free of cracks. At low fluence (1 J/cm2) and low pressure (10− 3 mbar), AZO/PET samples of high optical transmission in the visible range, low electrical sheet resistance, and high figure of merit (FOM) are produced. AZO films on fluorinated ethylene propylene have low FOM. The AZO films on PET substrates are used as electron transport layer in inverted organic solar cell devices employing P3HT:PCBM as photovoltaic polymer-fullerene bulk heterojunction.

We report the electrical and optical properties of structurally simple refractive-index-matched indium tin oxide (IM-ITO) films prepared on high-refractive index hard-coated polyethylene terephthalate (KM-V2) substrates by using a pilot scale roll to roll magnetron sputtering system for implementation in touch screen panels. We found that the ITO thin films are polycrystalline with a preferred (222) orientation. We determined the appropriate conditions for the deposition of simple-structure IM-ITO films on KM-V2 substrates for touch screen panels with an invisible electrode pattern. Moreover, the outgassing of the polymer substrate is very important in the roll-to-roll sputtering fabrication of high-quality IM-ITO films with the required electrical and optical properties.

We present highly flexible transparent electrodes composed of silver nanowire (AgNW) networks and silica aerogels embedded into UV-curable adhesive photopolymers (APPs). Because the aerogels have an extremely high surface-to-volume ratio, the enhanced van der Waals forces of the aerogel surfaces result in more AgNWs being uniformly coated onto a release substrate and embedded into the APP when mixed with an AgNW solution at a fixed concentration. The uniform distribution of the embedded composite electrodes of AgNWs and aerogels was verified by the Joule heating test. The APP with the composite electrodes has a lower sheet resistance (Rs) and a better mechanical stability compared with APP without aerogels. The APP with the embedded electrodes is a freestanding flexible substrate and can be used as an electrode coating on a polymer substrate, such as polydimethylsiloxane and polyethylene terephthalate. On the basis of the bending test results, the APPs with composite electrodes were sufficiently flexible to withstand a 1 mm bending radius (rb) and could be foldable with a slight change in Rs. Organic light emitting diodes were successfully fabricated on the APP with the composite electrodes, indicating the strong potential of the proposed flexible TEs for application as highly flexible transparent conductive substrates.

A monolayer assembly of silver nanodisks (AgNDs) was fabricated on the surface of a polydimethylsiloxane (PDMS) polymer substrate using the Langmuir–Blodgett technique. Upon stretching the PDMS substrate, the localized surface plasmon resonance (LSPR) spectrum of the AgND monolayer is blue-shifted when the incident light excitation is polarized parallel to the stretching direction. Conversely, a red shift in the LSPR spectrum of the AgND monolayer is observed in the case of light polarization orthogonal to the stretching direction. The magnitude of the shift in the LSPR spectrum is proportional to the degree of stretching of the PDMS substrate. Stretching PDMS in one direction causes its shrinking in the orthogonal direction. Consequently, the interparticle distance between individual AgNDs on the PDMS surface increases in the same direction as the mechanical stretching and simultaneously decreases in the orthogonal direction. The different optical responses of the AgND assembly on the surface of stretche...

Improving the fracture resistance of inorganic thin films is one of the key challenges in flexible electronic devices. A nonconventional in situ sputtering method is introduced to induce residual compressive stress in ZnO:Al thin films during deposition on a bent polymer substrate. The films grown under a larger prebending strain resulted in a higher fracture resistance to applied strains by exhibiting a ∼ 70% improvement in crack-initiating critical strain compared with the reference sample grown without bending. This significant improvement is attributed to the induced residual stress, which helps to prevent the formation of cracks by counteracting the applied strain.

The electrochemical (EC) properties of microelectrodes on flexible polymer substrates can vary as a result of microfabrication and postfabrication processes. These in turn may impact the chronic recording performance of such electrodes. In this paper, electrochemical techniques were utilized for the preparation and nonbiological evaluation of microfabricated flexible neural probes consisting of platinum electrode recording sites supported and insulated by Parylene C. The polymer substrate mitigates the mechanical mismatch between neural tissue and the probe. In addition, the thermoplastic nature of the polymer enables the probe to be shaped postfabrication using a thermoforming technique to impart a unique 3-D structure that further promotes tissue integration and supports the use of bioactive coatings. The EC techniques provided a simple means to clean electrode surfaces (80.2% decrease in 1-kHz impedance), identify functional devices, and evaluate their EC properties prior to implant. Both electrochemical impedance spectroscopy and cyclic voltammetry measurements were performed on electrode sites following fabrication, cleaning, mechanical manipulation for assembly, thermoforming, and sterilization. The results reveal in some cases changes in EC properties. Although changes following thermoforming did not impact the ability to acquire electrophysiological recordings, further investigation with additional tools is required to elucidate the exact nature of the structural and EC changes resulting in the observed increase in impedance and reduction in electrode surface area following thermoforming. [2014-0378]

The thermal stabilization effect of copper complexes on ethylene-propylene-diene terpolymer (EPDM) is studied during an accelerated degradation of polymer samples by their exposure to γ(137Cs)-radiation. These complexes of Cu(II) with two Schiff base ligands provided an efficient improvement in the stabilization of basic polymer. For the evaluation of improvement action of inorganic additive on thermal behavior of EPDM, the calculation of carbonyl and hydroxyl indexes and the radiochemical yields of corresponding radiolysis products prove the long-term stability of EPDM. Isothermal and nonisothermal chemiluminescence investigations were also accomplished, and the protection proficiencies of studied additives are compared by means of kinetic features of degradation. The activation energies required by the oxidation of polymer substrate were calculated, and their values are significant higher in comparison with the similar value found for pristine EPDM. The stabilized polymer is assisted by the interaction between mobile protons of ligands and hydrocarbon free radicals.

Conductive ink has been widely used in many application of electronic parts. It normally comes in liquid form and will need to be cured usually by conventional oven or laser irradiation after it is drawn to expose its metallic contents. But, these curing processes suffer from numerous problems consist of laser is a costly process and a warping defect when cured using conventional oven. Thus, alternative process is prominent and DLP projector has been seen capable of polymerised photopolymer materials. By making use of its potential associated with a proper control of the light intensity, exposure time and distance, it could provides sufficent heat to cure conductive ink. This study investigates the curing process of silver conductive ink on polymer substrate using DLP projector light with a variation of curing time and distance. Electrical resistance, hardness and adhesion level of cured sample were measured to determine its functionality. The conductive ink is deposited on the substrate using a doctor blade method and Microsoft Powerpoint slide is used to shape the light image produced by the projector. It was found that the conductivity and curing level of the sample cured were higher at the distance which getting the sharpest light image. The performances of the samples were also greater as the curing time increased. DLP projector is able to cure the conductive track efficiently with shorter curing time apart from the cheap preparation and setup cost.