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Chemical lift-off lithography (CLL) is a subtractive soft-lithographic technique used to pattern self-assembled monolayers (SAMs) containing functional alkanethiolates on Au surfaces. Alkanthiolate molecules, along with a single monolayer of Au, are removed in this process by oxygen-plasma activated polydimethysiloxane (PDMS) stamps. Monolayers patterned via CLL are robust, in contrast to conventional soft lithography, enabling high-fidelity patterning over a dynamic range of feature sizes (millimeter to nanometer). Recently, I have advanced CLL to pattern additional surfaces, including other coinage metals (e.g., Pt, Pd, Ag, Cu), reactive and transition metals (e.g., Ni, Ti, Al), and semiconductors (e.g., Ge). This process has a wide range of applications, including patterning of bioactive molecules and supported metal monolayers, as well as the simple, convenient fabrication of field-effect transistors (FETs). I have designed and developed FET biosensors coupled to rationally designed and chemically synthesized oligonucleotide sequences with molecular recognition capabilities, termed aptamers, for the detection of a diverse range of biologically important small-molecule targets (e.g., neurotransmitters, amino acids, sugars, lipids). Upon target capture, aptamers undergo conformational changes that redistribute charge densities on FET surfaces resulting in measurable changes in transconductance. These aptamer-FET sensors detected targets in full ionic strength biological fluids, with high specificity and selectivity, over large concentration ranges with low detection limits. Using this platform, I have developed sensors for the direct detection of the amino acid phenylalanine for potential point-of-care use for patients with phenylketonuria (PKU), a common genetic disorder that results in elevated and potentially harmful levels of phenylalanine in the blood and brain. Phenylalanine aptamer-FETs showed high sensitivity and selectivity towards phenylalanine versus similarly structured molecules, and were able to differentiate physiological phenylalanine concentrations in serum from mice treated with a phenylalanine hydroxylase inhibitor (i.e., a PKU mouse model). In parallel, I have extended this FET biosensor platform for the detection and discrimination of single base-pair mismatches in oligonucleotides towards electronic single-nucleotide polymorphism genotyping. I demonstrated the ability of DNA-functionalized FETs to distinguish hybridization between fully complementary DNA sequences, and analogous sequences with different types and locations of mismatches. Performing FET measurements under physiologically relevant conditions and elucidating sensing mechanisms is necessary for ultimate use in disease diagnostics and clinical point-of-care applications.

A UV-curable high refractive index resist (nD = 1.7063) for UV-nanoimprint lithography is synthesized and the refractive index can be further improved to 1.7327 after baking. 50 nm resolution patterns are faithfully imprinted into the resist film.

Droplet-based microfluidics is a modular platform in high-throughput single cell and small sample analyses. However, this droplet microfluidic system was widely fabricated using soft lithography or glass capillaries, which is expensive and technically demanding for various applications, limiting use in resource-poor settings. Besides, the variation in droplet size is also restricted due to the limitations on the operating forces that the paper-based platform is able to withstand. Herein we develop a fully integrated paper-based droplet microfluidic platform for conducting droplet generation and cell encapsulation in independent aqueous droplets dispersed in a carrier oil by incorporating electric fields. Through imposing an electric field, the droplet size would decrease with increasing the electric filed and smaller droplets can be produced at high applied voltage. The droplet diameter can be adjusted by the ratio of inner and outer flow velocities as well as the applied electric field. We also demonstrated the proof of concept encapsulation application of our paper device by encapsulating yeast cells under an electric field. Using a simple wax printing method, carbon electrodes can be integrated on the paper. The integrated paper-based microfluidic platform can be fabricated easily and conducted outside of centralized laboratories. This microfluidic system shows great potential in drug and cell investigations by encapsulating cells in resource-limited environments. This article is protected by copyright. All rights reserved.

Manufacturing of Y-branch coupler depends on high technology production equipment and in-factory accuracy assembly tools. The manufacturing of a 1×2 Y-branch symmetric and asymmetric waveguide coupler based on the mould replication process and Epoxy OG142 as an optical core is presented; an alternative to provide a less complex technique. The polymer optical waveguide adopted two basic designs: the 1×2 Y-branch symmetric coupler as the core structure and the 1×2 asymmetric coupler that allows non-symmetric optical splitting. This paper focused on the main structure fabrication of the 1×2 symmetric and asymmetric waveguide coupler that produces a power output. The fabrication was done by engraving acrylic to produce a master mould using CNC machining tools for optical devices. Both 1×2 devices were made via soft lithography, which duplicated the pattern from the master mould onto a second mould to produce an actual device. Optical polymer epoxy OG142 was injected into the second mould, of which the product was then put on top of acrylic. The device was completed after curing the optical polymer glue, epoxy OG142, by exposing the assembly on the second mould under UV light until both parts bonded. The difference between the simulation and design TOFR value was only ±2%. This showed that the simulation and design are in good agreement, which provides similar performance.

Simulating the structure and function of blood capillaries is very important for an in-depth insight into their role in the human body and treatment of capillary-related diseases. Due to the similar composition and structure, hollow hydrogel microfibers are well-recognized as potential biomimetic blood capillaries. In this paper, we report a novel, facile, and reproducible method to fabricate coaxial microfluidic chips via 3D printing-assisted soft lithography and then hollow hydrogel microfibers using the as-prepared coaxial microfluidic chips. Instead of traditional photoresist-based lithography, 3D printing of gelatin hydrogel under various extrusion pressures is used to construct sacrificial templates of coaxial microfluidic chips. Various solid and hollow hydrogel microfibers with complicated and hierarchical structures can be obtained via multitype coaxial microfluidic chips or a combination of coaxial microfluidic fabrication and post-treatment. The as-formed hollow hydrogel microfibers are evaluated in detail as biomimetic blood capillaries, including physicochemical and cytological properties. Our results prove that the hollow hydrogel microfibers exhibit excellent mass transport capacity, hemocompatibility, semipermeability, and mechanical strength, and their barrier function can be further enhanced in the presence of endothelial cells. Overall, our 3D printing-assisted fabrication strategy provides a new technique to construct microfluidic chips with complicated 3D microchannels, and the resulting hollow hydrogel microfibers are promising candidates for blood capillaries.

Structural optimization of microwire arrays is important for the successful demonstration of the practical feasibility of radial junction crystalline silicon (c-Si) solar cells. In this study, we investigated an optimized design of tapered microwire (TMW) arrays to maximize the light absorption of c-Si solar cells, while minimizing the surface recombination, for simultaneously improving the open-circuit voltage and short-circuit current density (Jsc). Finite-difference time-domain simulations confirmed that controlling the spacing between the TMWs at the nanometer scale is more effective for increasing the light absorption than increasing the TMW length. The photogenerated current of a c-Si TMW array with a 200 nm spacing was calculated to be 42.90 mA/cm2, which is close to the theoretical limit of 43.37 mA/cm2 in the 300-1100 nm wavelength range. To experimentally demonstrate the TMW arrays with a nanometer-scale spacing of 200 nm, which cannot be realized by conventional photolithography, we utilized a soft lithography method based on polystyrene beads for patterning a c-Si wafer. The solar cells based on optimized TMW arrays exhibited a Jsc of 42.5 mA/cm2 and power conversion efficiency of 20.5%, which exceed those of the previously reported microwire-based radial junction solar cells.

In this study, moth-eye-inspired structures (MISs), which improve optical performance of surfaces, were developed to enhance light efficiency in various optical fields. As the polymer-based soft lithography process can easily optimize MIS materials and nanostructures, 12 MIS/inverse MIS (IMIS) surfaces of 300, 500, and 1000 nm composed of polyurethaneacrylate (PUA) and polydimethylsiloxane (PDMS) polymers were fabricated, and a thin octafluorocyclobutane (C4F8) layer was deposited on the surfaces to reduce their surface energies. The results showed that the 300-nm PDMS-MIS showed excellent optical properties with 94.44 % transmittance and 3.28 % reflectance. Additionally, two theoretical phenomena, the diffraction effect and double-slit diffraction, were experimentally demonstrated using three single-wavelength lasers. Subsequently, contact-angle measurements demonstrated all MIS/IMIS surfaces to possess hydrophobic and superhydrophobic properties, which can protect devices from outdoor liquids. Finally, we confirmed the applicability of MIS by attaching it to a cell phone display and an ITO glass, which is used as a substrate in various optical instruments.

3D printing has emerged as a promising fabrication technique for microfluidic devices, overcoming some of the challenges associated with conventional soft lithography. Filament-based polymer extrusion (popularly known as fused deposition modeling (FDM)) is one of the most accessible 3D printing techniques available, offering a wide range of low-cost thermoplastic polymer materials for microfluidic device fabrication. However, low optical transparency is one of the significant limitations of extrusion-based microfluidic devices, rendering them unsuitable for cell culture-related biological applications. Moreover, previously reported extrusion-based devices were largely dependent on fluorescent dyes for cell imaging because of their poor transparency. First, we aim to improve the optical transparency of FDM-based microfluidic devices to enable bright-field microscopy of cells. This is achieved using (1) transparent polymer filament materials such as poly(ethylene terephthalate) glycol (PETg), (2) optimized 3D printing process parameters, and (3) a hybrid approach by integrating 3D printed microfluidic devices with cast poly(dimethylsiloxane) (PDMS) blocks. We begin by optimizing four essential 3D printing process parameters (layer height, printing speed, cooling fan speed, and extrusion flow), affecting the overall transparency of 3D printed devices. Optimized parameters produce exceptional optical transparency close to 80% in 3D printed PETg devices. Next, we demonstrate the potential of FDM-based 3D printing to fabricate transparent micromixing devices with complex planar and nonplanar channel networks. Most importantly, cells cultured on native 3D printed PETg surfaces show excellent cell attachment, spreading, and proliferation during 3 days of culture without extracellular matrix coating or surface treatment. Next, we introduce L929 cells inside hybrid PETg-PDMS biomicrofluidic devices as a proof of concept. We demonstrate that 3D printed hybrid biomicrofluidic devices promote cell adhesion, allow bright-field microscopy, and maintain high cell viability for 3 days. Finally, we demonstrate the applicability of the proposed fabrication approach for developing 3D printed microfluidic devices from other FDM-compatible transparent polymers such as polylactic acid (PLA) and poly(methyl methacrylate) (PMMA).

Traditional soft lithography based PDMS device fabrication requires complex procedures carried out in a clean room. Herein, we report a photolithography-free method that rapidly produces PDMS devices in 30 min. By using a laser cutter to ablate a tape, a male photoresist mold can be obtained within 5 min by a simple heating-step, which offers significant superiority over currently used photolithography-based method. Since it requires minimal energy to cut the tape, our fabrication strategy shows good resolution (∼ 100 µm) and high throughput. Furthermore, the micro-mold height can be easily controlled by changing the tape types and layers. As a proof-of-concept, we demonstrated that the fabricated PDMS devices are compatible with biochemical reactions such as quenching reaction of KI to fluorescein and cell culture/staining. Collectively, our strategy shows advantages of low input, simple operation procedure and short fabrication time, therefore we believe this photolithography-free method could serve as a promising way for rapid prototyping of PDMS devices and be widely used in general biochemical laboratories.

Soft lithography is one of the most promising nanofabrication technologies for scalable nanomanufacturing. It uses flexible molds or stamps to fabricate extremely high-resolution nanopatterns in a low cost and rapid fashion on both flat and curved surfaces. Although two-dimensional soft lithography has been widely investigated and applied for some applications, there is a lack of quantitative research on using nanometer scale 3D patterns fabricated by atomic force microscope (AFM) for 3D soft lithography. In this paper, we demonstrated the effectiveness of ultrasonic vibration assisted AFM-based nanomachining in fabricating 3D master nanotemplates for 3D soft lithography. We successfully applied Polydimethylsiloxane (PDMS) daughter molds, casted from a nanometer scale 3D master template, using a soft lithography technique solvent-assisted micromolding. In addition, we investigated the quality and reusability of the master nanotemplates, and the quality of the PDMS patterns by quantifying the volume differences using an automatic imaging registration algorithm. Results show that there are zero or little PDMS residuals in the polymethyl methacrylate (PMMA) master nanotemplate with a simple contour for the first and second daughter mold casting, but 7% residuals for the third casting. And a more complex master nanotemplate shows slightly higher residual levels.

To prepare hydrophobic wood with rose-like hydrophobic surface and avoid moisture damage to wood. In this paper, With polyvinyl alcohol (PVA) as the elastic mold, the microstructure of the rose petals was replicated on the wood surfaces by soft lithography. The soft lithography technique was used to modify the wood sur-face, transferring over it a rose-like topography, based on a micro/nano hierarchical structure using fresh rose as the template. The surface of poplar coated with polystyrene was reconstructed twice using 1, 3, 5, 8 and 10% PVA as templates, respectively. The results show that the average contact angle of poplar surface coated with polystyrene is more than 130°, that of fresh rose surface is about 140°, and that of untreated wood is about 60°. Therefore, the wood surface with polystyrene has obtained a similar structure to that of rose surface and has a certain hydrophobicity. In addition, the microstructures observed by means of SEM, showing rough surface structures with micro-nanopapillate hills on wood surfaces. Water droplets could easily roll down on such wood surfaces, exhibiting super-hydrophobic and low adhesion properties. The successful fabrication of rose-like wood provided a new direction for researches on the super-hydrophobic of wood, which could effectively prevent the damage of moisture to wood.

We report high-performance transparent copper grid electrodes on glass and plastic substrates that offer a higher Haacke figure-of-merit than conventional indium tin oxide electrodes and are well-matched to the requirements for organic photovoltaics (OPVs). The electrode is fabricated using microcontact lithography with a combination of molecular resist and low toxicity etchant, namely, hexadecanethiol and aqueous ammonium persulfate. This approach to electrode fabrication is much faster than conventional lithography because it takes 20 times narrower than is possible using conventional metal printing methods and so a grid pitch

Water splitting for H2 production by absorbing sunlight is broadly used as a common technique to counter existing energy crisis and environmental problems, caused by extreme use of fossil fuels. We report a versatile and facile method to fabricate ordered Silicon nanohorns (SiNHs) by employing prefabricated metal nano-gap template on Si. The close-packed monolayer is used to develop the nanohole template, which enables the generation of SiNHs via metal-assisted controlled chemical etching. By varying monolayer parameters and etching sequences, SiNHs with desired dimensions were obtained. Growth along the crystalline plane of the base substrate ⟨100⟩, with a consistent bent at the tip of the SiNH, has been observed. The resulting SiNHs exhibited enhanced photoelectrochemical properties, with short-circuit photocurrent density more than four times higher than that of the planer Si along with enhanced trapping of photogenerated carriers. A photocurrent density of ~4.8 mA/cm2 was observed at a potential of -1 V vs. RHE. Further, the electrochemical impedance study (EIS) was carried out to understand the photoelectrochemical activity and charge transfer kinetics of the SiNHs system. These nanostructures enhance light absorption and may be one of the low-cost alternatives for optical devices, sensors, and hydrogen evolution.

Rice, Oryzae sativa, is a staple crop produced around the world. Despite the various physical structures that the plant employs to protect itself from pathogens, the fungus Magnaporthe oryzae breaks through these barriers and devastates rice crops. Although ongoing research is being conducted to determine how the fungus interacts with the surface of the rice leaf, more research into the mechanical stimuli present on the rice leaf surface is necessary to better understand appressoria formation. As a comparison material to the rice leaf surface, the copolymer polydimethylsiloxane (PDMS) was chosen to mimic the surface mechanical properties of the rice leaf for its biocompatibility and tunable mechanical properties. Selected surface properties of stiffness, surface wettability, and topography were measured for both the rice leaf surface and PDMS replicas. The results of this study determined that PDMS properties can be modified to closely mimic those of the rice leaf surface, but drawbacks were noted in some areas, such as stiffness. These areas would require further modification to PDMS and are topics of future research.

The utilization of biomaterials in implanted blood-contacting medical devices often induces a persistent problem of microbial infection, which results from bacterial adhesion and biofilm formation on the surface of biomaterials. In this research, we developed new fluorinated alkoxyphosphazene materials, specifically poly[bis(octafluoropentoxy) phosphazene] (OFP) and crosslinkable OFP (X–OFP), with improved mechanical properties, and further modified the surface topography with ordered pillars to improve the antibacterial properties. Three X–OFP materials, X–OFP3.3, X–OFP8.1, X–OFP13.6, with different crosslinking densities were synthesized, and textured films with patterns of 500/500/600 nm (diameter/spacing/height) were fabricated via a two stage soft lithography molding process. Experiments with 3 bacterial strains: Staphylococcal epidermidis, Staphylococcal aureus, and Pseudomonas aeruginosa showed that bacterial adhesion coefficients were significantly lower on OFP and X–OFP smooth surfaces than on the polyurethane biomaterial, and surface texturing further reduced bacterial adhesion due to the reduction in accessible surface contact area. Furthermore the anti-bacterial adhesion effect shows a positive relationship with the crosslinking degree. Biofilm formation on the substrates was examined using a CDC biofilm reactor for 7 days and no biofilm formation was observed on textured X–OFP biomaterials. The results suggested that the combination of fluorocarbon chemistry and submicron topography modification in textured X–OFP materials may provide a practical approach to improve the biocompatibility of current biomaterials with significant reduction in risk of pathogenic infection., Graphical abstract Image 1, Highlights • New fluorinated alkoxyphosphazene materials with improved mechanical properties were developed. • Fabrication of textured polyphosphazene surface was optimized by selection of solvents. • Textured fluorinated alkoxyphosphazene surfaces significantly inhibited bacterial adhesion and biofilm formation. • Fluorinated alkoxyphosphazene can be new biomaterials for medical devices with resistance to microbial infection.

Nanoarchitectonics has gained recent attention from researchers and can be utilized in the development of catalytic systems with unique morphological features, high surface area and engineered catalytic sites. In this work, biomimetic substrates have been fabricated by replicating wings of a grasshopper insect with interesting surface hierarchical architecture by employing a soft lithography technique. Further, the substrates were engineered to form a hetero-nanojunction of gold and silver nanolayers by using the sputtering technique. The replicated substrates possess multi-wall supported sharp edged pods type morphology and provide a good degree of adhesion to the deposited metal layers with increased surface area in comparison to a flat control substrate. The catalytic potential of these metal-coated nanoarchitectonics-based substrates was examined as dip catalysts for degradation of a model organic pollutant, methylene blue in the presence of sodium borohydride as a reducing agent. The biomimetic substrate showed higher photocatalytic degradation of methylene blue due to the enhanced plasmonic effect in comparison to the flat control substrate. The mechanism of the degradation has been discussed in detail in the presence and absence of light irradiation. This work paves way for the design and development of recyclable and efficient dip catalysis substrates by combining the nanoarchitectonics and biomimetic approaches.

The patterning of surface structures is a critical step for interfacial engineering applications that are based on soft lithography, casting, or imprinting techniques in general. However, photolithography and mold/die fabrication processes are expensive and time-consuming. To solve this problem, we developed a novel laser-based process that exploits the high stretchability of a polymer. In this study, continuous-wave laser-induced pyrolysis was conducted on a pre-stretched Ecoflex polymer substrate to obtain a controllable hydrophobic surface with functional structures at the micro/nanoscale, which were constructed via the facile removal of pyrolytic byproducts. Under the optimum strain rate and laser parameters, periodic wrinkle generation and a proportional channel pitch reduction were observed, which provided hierarchical micro/nanostructures and enlarged the air gaps between the target droplet and the hydrophobic structures. The processed surface exhibited improved hydrophobic properties (WCA ~ 135°) compared with a flat Ecoflex polymer surface (WCA ~ 105°). Thus, a facile manufacturing method for stretchable polymer substrates with hydrophobic patterned surfaces is proposed.

This work describes the preparation and characterization of printed biodegradable polymer (polylactic acid) capsules made in two different shapes: pyramid and rectangular capsules about 1 and 11 μm in size. Obtained core-shell capsules are described in terms of their morphology, loading efficiency, cargo release profile, cell cytotoxicity, and cell uptake. Both types of capsules showed monodisperse size and shape distribution and were found to provide sufficient stability to encapsulate small water-soluble molecules and to retain them for several days and ability for intracellular delivery. Capsules of 1 μm size can be internalized by HeLa cells without causing any toxicity effect. Printed capsules show unique characteristics compared with other drug delivery systems such as a wide range of possible cargoes, triggered release mechanism, and highly controllable shape and size.

A portable self-flow filtration and separation platform was designed using soft lithography to create a polydimethylsiloxane (PDMS) microfluidic channel cover combined with a matching acrylic substrate. The separation zone was filled with microbeads of appropriate sizes to achieve universal filtration and separation. This simple structure requires only 20 μl of the sample for filtration separation. A vacuum of 760 torr is applied to the porous PDMS cover to drive the sample during testing. The average time required for a 20 μl sample of blood to pass through the separation zone is about 56 s, while the filling time for the detection zone of volume 6 μl is about 319 s. When the hematocrit of the blood sample is about 20-25%, the separation efficiency is 99.98%. Further, the separation efficiency of fat globules from raw milk is close to 100%, whereas almost all impurities are filtered out from juice and stool samples. It is also observed that E. coli in the stool can pass from the separation to detection zone at a maximum rate of about 81.21%, with an average of about 68.18%.

We present ordered surface crack patterns discovered in microfluidic channels/chambers in polydimethylsiloxane (PDMS). The cracks are formed in situ under confinement due to compression applied following an oxygen plasma step in a soft lithography process. The crack patterns are noticeable only after fluorescent labeling and vary with fluidic layout as well as material compliance.

The use of microfluidic devices or systems is not limited to any particular department or sector. Presently, from the biomedical to cosmetic, environmental protection to engineering, the application of these devices is increasing enormously. The study on fabrication of such devices become one of the most developing fields of investigation in the current time. Microchannel fabrication via conventional so-called traditional fabrication techniques is a challenging task. Various researchers are developing different types of materials and techniques to fabricate microchannel for different kinds. Some of the materials are polymers, ceramics, and metals. In this article, an interesting process for the manufacturing of serpentine square wave microchannel with polydimethylsiloxane (PDMS) has been offered and explored. The complete process of fabrication of the microchannel has been discussed. It includes major two steps: serpentine square wave mold preparation and serpentine square wave microchannel fabrication. Primarily, the mold of the microchannel of serpentine square wave type with proper dimensions has been produced with the support of wire electric discharge machining and then using these molds, serpentine square wave microchannel of PDMS has been prepared by the soft lithography technique. The proposed process is helpful to manufacture microchannel as per the designed dimensions. From this study, researchers will be benefited by obtaining the guideline related to the serpentine square wave type microchannel fabrication with a cost-effective way.

Microfluidic devices are traditionally monitored by bulky and expensive off-chip sensors. We have developed a soft piezoresistive sensor capable of measuring micron-level strains that can be easily integrated into devices via soft lithography. We apply this sensor to achieve fast and localized monitoring of pressure, flow, and valve actuation.

In the neuromuscular system, signal transmission from motor neurons (MNs) to innervated muscle fibers is crucial for their synaptic function, viability, and maintenance. In order to better understand human neuromuscular junction (hNMJ) functionality, it is important to develop on-a-chip devices with human cells. To investigate this cell network, microfluidic platforms are useful to grow different cell types in isolated compartments. Such devices have already been developed to study in vitro neuronal circuitry. Here, we combined microfluidics with two techniques: soft lithography and custom microelectrodes array (MEA). Our goal was to create hNMJs on a specific pattern of electrodes to stimulate pre-synaptic axons and record post-synaptic muscle activity. Micromachining was used to create structurations to guide muscle growth above electrodes, without impairing axon propagation, therefore optimizing the effectiveness of activity recording. Electrodes were also arranged to be aligned with the microfluidic chambers in order to specifically stimulate axons that were growing between the two compartments. Isolation of the two cell types allows for the selective treatment of neurons or muscle fibers to assess NMJ functionality hallmarks. Altogether, this microfluidic/microstructured/MEA platform allowed mature and functional in vitro hNMJ modelling. We demonstrate that electrical activation of MNs can trigger recordable extracellular muscle action potentials. This study provides evidence for a physiologically relevant model to mimic a hNMJ that will in the future be a powerful tool, more sensitive than calcium imaging, to better understand and characterize NMJs and their disruption in neurodegenerative diseases.

The junction between the epithelium and the underlying connective tissue undulates, constituting of rete ridges, which lack currently available soft tissue constructs. In this study, using a micro electro mechanical systems process and soft lithography, fifteen negative molds, with different dimensions and aspect ratios in grid- and pillar-type configurations, were designed and fabricated to create three-dimensional micropatterns and replicated onto fish-scale type I collagen scaffolds treated with chemical crosslinking. Image analyses showed the micropatterns were well-transferred onto the scaffold surfaces, showing the versatility of our manufacturing system. With the help of rheological test, the collagen scaffold manufactured in this study was confirmed to be an ideal gel and have visco-elastic features. As compared with our previous study, its mechanical and handling properties were improved by chemical cross-linking, which is beneficial for grafting and suturing into the complex structures of oral cavity. Histologic evaluation of a tissue-engineered oral mucosa showed the topographical microstructures of grid-type were well-preserved, rather than pillar-type, a well-stratified epithelial layer was regenerated on all scaffolds and the epithelial rete ridge-like structure was developed. As this three-dimensional microstructure is valuable for maintaining epithelial integrity, our micropatterned collagen scaffolds can be used not only intraorally but extraorally as a graft material for human use.

Mechanical forces are integral to cellular migration, differentiation and tissue morphogenesis; however, it has proved challenging to directly measure strain at high spatial resolution with minimal perturbation in living sytems. Here, we fabricate, calibrate, and test a fibronectin (FN)-based nanomechanical biosensor (NMBS) that can be applied to the surface of cells and tissues to measure the magnitude, direction, and strain dynamics from subcellular to tissue length-scales. The NMBS is a fluorescently-labeled, ultra-thin FN lattice-mesh with spatial resolution tailored by adjusting the width and spacing of the lattice from 2–100 µm. Time-lapse 3D confocal imaging of the NMBS demonstrates 2D and 3D surface strain tracking during mechanical deformation of known materials and is validated with finite element modeling. Analysis of the NMBS applied to single cells, cell monolayers, and Drosophila ovarioles highlights the NMBS’s ability to dynamically track microscopic tensile and compressive strains across diverse biological systems where forces guide structure and function., The ability to measure strain in cells and tissues in vitro with minimal perturbation and at high spatial resolution has proven challenging. Here the authors develop a fluorescently-labelled fibronectin square lattice mesh that can be applied to the surface of cells and tissues to enable direct quantification and mapping of strain over time.

In this study, inspired from human cochlea, we propose an artificial basilar membrane structure based on an array of gold electrodes microfabricated along the opposite surfaces of a piezoelectric continuum. The proposed piezoelectric continuum features an isosceles trapezoidal geometry and is situated atop an elastomer matrix with embedded electrode grooves and a duct. At first, a detailed analytical model is presented, which formulates the continuum’s planar deflection equation, governing its elastodynamic behavior. Subsequently, in order to verify the analytical outcomes, a multiphysics finite-element analysis is performed in COMSOL®. Both analytical and numerical models demonstrate desired frequency selectivity akin to the capability of a biological basilar membrane. Subsequently, a proof-of-concept model of the proposed structure is custom-fabricated through standard photo- and soft lithography techniques using Polyvinylidene Difluoride (PVDF), gold, and Polydimethylsiloxane (PDMS) materials. Finally, the fabricated artificial basilar membrane that is intended to be used as a broad band sensor, and artificial cochlea for seamless human-robot interaction is experimentally characterized using a custom-built acoustic exciter, and its effective performance is validated within the frequency range of 3 kHz to 8 kHz.

Surface architecture belonging to flora and fauna is preferred because of their unique three dimensional micro/nanostructures, which can be utilised as novel support in SERS based chemical detectio...

3D printing of master molds for soft lithography-based fabrication of microneedles (MNs) is a cost effective, easy and fast method for producing MNs with variable designs. Deviating from the classical geometries of MNs, ‘tanto blade’-inspired MNs showed effective skin penetration, acting as sharp structures with low insertion force of 10.6 N, which is sufficient for manual insertion. Additionally, hydrophilic, fluorescent noble metal nanocluster-modified gelatin nanocarriers were loaded in polyvinyl alcohol/sucrose MNs to act as a novel potential theranostic system emitting light in the near-infrared (λem = ~700 nm). Nanoparticles (NPs) distribution within the MNs and release have been monitored using confocal laser scanning microscopy by means of spectral analysis and linear unmixing. Furthermore, the MNs patch was modified by carving a channel at each of the four corners of the patch. This facilitated the separation process of MNs from the patch base into skin, when 15 µL phosphate buffered saline was applied through each channel post-skin insertion of the MNs. Then, the patch base can be removed easily leaving the implanted MNs inside the skin for further release of the NP cargo. This successfully reduced the application time to 1 min for enhanced patient compliance.

This work employed end-grafted poly ethylene glycol PEG and hydroxyl-terminated poly 2-vinylpyridine P2VP polymer chains for selective immobilization and patterning of plasmonic nanoparticles NPs . A soft lithographic method which called micromolding in capillaries MIMIC used in this study. The polymers are deposited the capillary flow by the channels which formed by an elastomeric mold and substrate. The localized coatings are referred as polymer brushes and show great promise in the assembly of NPs due to the tunable interaction between the polymer chains and particles. The results show that the width of patterns defined by the channels is smaller than 1.5 µm with a length of around 0.5 cm. Also, the heights of the patterns are ~3.5 nm for P2VP and ~10 nm for PEG. The fabricated structures exhibited high levels of plasmonic activity and surface enhanced Raman scattering due to the immobilized Au NPs. The patterning polymer brushes and plasmonic NPS over large areas by a low-cost process show great promise for a variety of applications that range from molecular sensors to biotechnology

The patterning of polydimethylsiloxane (PDMS) into complex two-dimensional (2D) or 3D shapes is a crucial step for diverse applications based on soft lithography. Nevertheless, mould replication that incorporates time-consuming and costly photolithography processes still remains the dominant technology in the field. Here we developed monolithic quasi-3D digital patterning of PDMS using laser pyrolysis. In contrast with conventional burning or laser ablation of transparent PDMS, which yields poor surface properties, our successive laser pyrolysis technique converts PDMS into easily removable silicon carbide via consecutive photothermal pyrolysis guided by a continuous-wave laser. We obtained high-quality 2D or 3D PDMS structures with complex patterning starting from a PDMS monolith in a remarkably low prototyping time (less than one hour). Moreover, we developed distinct microfluidic devices with elaborated channel architectures and a customizable organ-on-a-chip device using this approach, which showcases the potential of the successive laser pyrolysis technique for the fabrication of devices for several technological applications. A laser-based patterning method enables the fast fabrication of high-quality two- and three-dimensional features in polydimethylsiloxane for microfluidics and biomedical applications.

In the field of stimuli-responsive polymer research, poly-N-isopropylacrylamide (PNIPAAm) has been widely studied, because this material has unique properties which respond to temperatures near to that of the human body, approximately 36 °C. In this study, a nano-patterned PNIPAAm hydrogel was prepared using UV-irradiation and soft lithography. Chemical changes in the C–C double bonds of the PNIPAAm hydrogel were confirmed by FT-IR analysis. The thermal properties of the hydrogel were analyzed by differential scanning calorimetry (DSC), which confirmed its low critical solution temperature (LCST). The highest gel content of approximately 46% was achieved at 120 min UV-irradiation. The nano-patterned morphology of the PNIPAAm hydrogel exhibited temperature-dependent reversible shape transformation. This study shows that the reversible shape transformation of the PNIPAAm hydrogel was due to swelling and shrinking.

This paper presents the design, simulation and low-cost fabrication of microfluidic channel for biomedical application. Channel is fabricated using soft lithography technique. Printed Circuit Board (PCB) is used to make the master for the channel. Channel pattern is transferred on PCB plate using toner transfer technique followed by ferric chloride etching. Paper also discusses, the issues involved in PCB based master fabrication and their viable solutions. Glass is used as substrate material and the channel is made of Sylgard 184 Polydimethylsiloxane (PDMS). Channel is interfaced with a syringe pump to observe the fluid flow. To predict the behavior of the channel, FEM simulation is performed using COMSOL Multiphysics 5.2a. There is a good match between the theoretical, simulation and test results. Finally, to test the biocompatibility of the channel, genomic DNA is passed through the channel and gel electrophoresis analysis is performed.

Development of economical and mass-manufacturable bioelectrodes with desirable physical properties is one of the crucial challenges to realize automated and robust enzymatic biofuel cell (EBFC). This article focuses to develop customized CO2 laser-induced flexible graphene (LIFG) bioelectrodes on the polyamide substrate. The cost-efficiency and customization of LIFG bioelectrodes have been further demonstrated for EBFC application by integrating them into a microfluidic device, fabricated by the conventional soft lithography on polydimethylsiloxane (PDMS). First, the LIFG bioelectrodes were created at optimized CO2 laser (power and speed) irradiation, and characterization was performed to ensure the existence of graphene material. Subsequently, the surface morphological study of the noninduced polyamide sheet, LIFG, and LIFG with the relevant enzyme (GO x and laccase)-modified bioelectrodes has been characterized. Finally, various voltammetric electrochemical analyses of the modified LIFG bioelectrodes have been accomplished. After such an electrochemical study, the bioelectrodes were integrated into the microfluidic device and a power density of 13 $\mu \text{W}$ /cm2 ( $52~\mu \text{A}$ /cm2) was harnessed at an optimized fluid rate of $200~\mu \text{L}$ /min. By using this fabrication method, the proposed LIFG bioelectrodes have shown excellent potential for electrochemical redox and polarization performance in a microfluidic environment, with a huge scope to enrich the power output by introducing the additional cofactor-based electrochemistry and device stacking.

Photonic integrated circuits (PIC) can be mass-produced by 3D-printing technologies in combination with advanced hybrid inorganic–organic materials. In this work we present the development of hybrid inorganic–organic materials based on the fast sol–gel process (FSG) which can be used as a “tool kit” for the fabrication of advanced optical materials. We present routes to fabrication of FSG materials with a variety of properties: the materials may exhibit mechanical toughness or be elastic; they may be thermally and UV-curable, they can have a tailored refractive index value and tailored chemical environment, such as an aromatic matrix. Using these materials, we demonstrated strong optical bonding between optical components for solar energy and optical fiber coupler systems. We demonstrated fabrication of macroscale optical elements by 3D-printing methods, such as soft lithography, inkjet, and digital light processing (DLP) printing. We also demonstrated 3D-printing fabrication of nano/microscale optical elements by soft lithography, nanoimprint lithography (NIL), and direct laser writing (DLW). The obtained 3D-printed sol–gel optical elements were found to exhibit mechanical advantages: improved surface quality, resistance to solvents, improved adhesion to glass substrate and stability to temperature above 200 °C compared with 3D-printed organic polymer elements. In addition, the sol–gel elements present the following optical advantages: improved optical quality, improved optical transmission, and durability to laser radiation. We believe that this class of materials is a promising candidate for use in mass production of photonic integrated circuits (PIC) by 3D-printing technologies.

Microfluidic devices are constructed from polydimethylsiloxane (PDMS) due to their biocompatibility, fabrication ease, well-established protocols, and simplicity. PDMS-based microfluidic devices are constructed by (i) applying liquid PDMS to a negative mold (usually a silicon or 3D-printed mold) and (ii) curing the PDMS with heat exposure over a set time period. Unreacted resin monomers in 3D-printed molds prevent PDMS from fully curing, resulting in improper channel formation in PDMS and reducing the PDMS device’s efficacy. An in-house protocol that uses SU-8 as a “non-stick” coating on 3D-printed molds facilitates the successful casting of PDMS. Contact angle, surface profile, optical profile, and force testing prove that PDMS cast from SU-8-treated molds resembles pristine PDMS, unlike PDMS cast from untreated molds. Further, this method is generalized to commercial 3D prints using different 3D printing resins. To demonstrate this technique’s viability in microfluidic devices, a microfluidic tree using PDMS from treated 3D prints shows vibrant colors and clear lines. This is absent from an untreated PDMS.

Supported lipid membranes are versatile biomimetic coatings for the chemical functionalization of inorganic surfaces. Developing simple and effective fabrication strategies to form supported lipid membranes with micropatterned geometries is a long-standing challenge. Herein, we demonstrate how the combination of chemical lift-off lithography (CLL) and easily prepared lipid bicelle nanostructures can yield micropatterned, supported lipid membranes on gold surfaces with high pattern resolution, conformal character, and biofunctionality. Using CLL, we functionalized gold surfaces with patterned arrays of hydrophilic and hydrophobic self-assembled monolayers (SAMs). Time-lapse fluorescence microscopy imaging revealed that lipid bicelles adsorbed preferentially onto the hydrophilic SAM regions, while there was negligible lipid adsorption onto the hydrophobic SAM regions. Functional receptors could be embedded within the lipid bicelles, which facilitated selective detection of receptor-ligand binding interactions in a model streptavidin-biotin system. Quartz crystal microbalance-dissipation measurements further identified that lipid bicelles adsorb irreversibly and remain intact on top of the hydrophilic SAM regions. Taken together, our findings indicate that lipid bicelles are useful lipid nanostructures for reproducibly assembling micropatterned, supported lipid membranes with precise pattern fidelity.

Natural compound eyes provide the inspiration for developing artificial optical devices that feature a large field of view (FOV). However, the imaging ability of artificial compound eyes is generally based on the large number of ommatidia. The lack of a tunable imaging mechanism significantly limits the practical applications of artificial compound eyes, for instance, distinguishing targets at different distances. Herein, we reported zoom compound eyes that enable variable-focus imaging by integrating a deformable poly(dimethylsiloxane) (PDMS) microlens array (MLA) with a microfluidic chamber. The thin and soft PDMS MLA was fabricated by soft lithography using a hard template prepared by a combined technology of femtosecond laser processing and wet etching. As compared with other mechanical machining strategies, our combined technology features high flexibility, efficiency, and uniformity, as well as designable processing capability, since the size, distribution, and arrangement of the ommatidia can be well controlled during femtosecond laser processing. By tuning the volume of water injected into the chamber, the PDMS MLA can deform from a planar structure to a hemispherical shape, evolving into a tunable compound eye of variable FOV up to 180°. More importantly, the tunable chamber can functionalize as the main zoom lens for tunable imaging, which endows the compound eye with the additional capability of distinguishing targets at different distances. Its focal length can be turned from 3.03 mm to infinity with an angular resolution of 3.86 × 10-4 rad. This zoom compound eye combines the advantages of monocular eyes and compound eyes together, holding great promise for developing advanced micro-optical devices that enable large FOV and variable-focus imaging.