Explore the vast range of titles available.

The proposed work aims to develop a sensitive surface-enhanced Raman spectroscopy (SERS) nano-biosensor. The inverted nano pyramid array on silicon substrate fabricated using electron beam lithography (EBL) was utilised as a master template and the mold was later replicated via nanoimprinting process to prepare gold-coated polymer nanopyramid three-dimensional (3D) SERS substrate. The fast and versatile replication process using nanoimprinting lithography (NIL) can produce polymer nanopyramids in a low-cost and reproducible fashion. Also, the proposed fabrication protocol can be easily upscale for large scale fabrication. The intense electric field confinement at nanotips and four edges of gold-coated polymer nanopyramid enhanced the Raman signal of probe molecules, i.e., Rhodamine 6G with a limit of detection down to 3.277 × 10 −9 M was achieved. This work also underlines the efficiency of gold-coated polymer nanopyramid arrays in the spectral detection of hemoglobin proteins at low concentrations. The Raman signal enhancement mechanism was further studied through the electromagnetic simulation using COMSOL Multiphysics. In addition, bending test experiments were performed to understand the effect of flexibility on SERS signal response. The fabricated gold-coated polymer nanopyramids arrays could pave the way for the development of low-cost SERS platforms for the detection of hazardous biological and chemical compounds at ultra-low concentrations in practical applications.

The investigation of biobased systems as photocurable resins for optical 3D printing has attracted great attention in recent years; therefore, novel vanillin acrylate-based resins were designed and investigated. Cross-linked polymers were prepared by radical photopolymerization of vanillin derivatives (vanillin dimethacrylate and vanillin diacrylate) using ethyl(2,4,6-trimethylbenzoyl)phenylphosphinate as photoinitiator. The changes of rheological properties were examined during the curing with ultraviolet/visible irradiation to detect the influences of solvent, photoinitiator, and vanillin derivative on cross-linking rate and network formation. Vanillin diacrylate-based polymers had higher values of yield of insoluble fraction, thermal stability, and better mechanical properties in comparison to vanillin dimethacrylate-based polymers. Moreover, the vanillin diacrylate polymer film showed a significant antimicrobial effect, only a bit weaker than that of chitosan film. Thermal and mechanical properties of vanillin acrylate-based polymers were comparable with those of commercial petroleum-derived materials used in optical 3D printing. Also, vanillin diacrylate proved to be well-suited for optical printing as was demonstrated by employing direct laser writing 3D lithography and microtransfer molding techniques.

Recent studies have shown that insect wings have evolved to have micro- and nanoscale structures on the wing surface, and biomimetic research aims to transfer such structures to application-specific materials. Herein, we describe a simple and cost-effective method of replica molding the wing topographies of four cicada species using UV-curable polymers. Different polymer blends of polyethylene glycol diacrylate and polypropylene glycol diacrylate were used as molding materials and a molding chamber was designed to precisely control the x, y, and z dimensions. Analysis by scanning electron microscopy showed that structures ranged from 148 to 854 nm in diameter, with a height range of 191–2368 nm, and wing patterns were transferred with high fidelity to the crosslinked polymer. Finally, bacterial cell studies show that the wing replicas possess the same antibacterial effect as the cicada wing from which they were molded. Overall, this work shows a quick and simple method for patterning UV-curable polymers without the use of expensive equipment, making it a highly accessible means of producing microstructured materials with biological properties.

Microfluidics is an area that allows the design and construction of microchips. The most common fabrication of these chips is expensive and difficult to access, requiring a specialized laboratory, with instruments that need to be monitored by experienced technicians and high-cost materials, then new techniques are sought to facilitate their production. Here, we present a fabrication methodology that combines the 3D printer resolution, and the polydimethylsiloxane flexibility to create hydrophobic and biocompatible microfluidics chips which are connected to a microfluidic control system. Transparent, and leak-free polydimethylsiloxane microchips were achieved with a width and a height of 250 µm. This strategy allows to produce at least, 20 chips using the same resin mold. The pressure at which the chip can work is from 2.4 kPa to 124 kPa. This work provides a low-cost alternative for academic and research groups to create their own microfluidic systems and use the microfluidic advantages in all types of applications including biosensor building, studies in medicine, biology, nanoscience, environmental technology, chemistry, etc., since it allows a controlled manipulation of one or more fluids in a certain area where a sensor can be placed, generate a reaction, among others.

Nanopatterned tribocharge can be generated on the surface of elastomers through their replica molding with nanotextured molds. Despite its vast application potential, the physical conditions enabling the phenomenon have not been clarified in the framework of analytical mechanics. Here, we explain the final tribocharge pattern by separately applying two models, namely cohesive zone failure and cumulative fracture energy, as a function of the mold nanotexture’s aspect ratio. These models deepen our understanding of the triboelectrification phenomenon.

Fabrication of microfluidic devices by soft lithography is by far the most popular approach due to its simplicity and low cost. The approach relies on casting of elastomers, such as polydimethylsiloxane (PDMS), on masters fabricated from photoresists on silicon substrates. These masters, however, can be expensive, complicated to fabricate, and fragile. Here we describe an optimized replica molding approach to preserve the original masters by heat molding of polycarbonate (PC) sheets on PDMS molds. The process is faster and simpler than previously reported methods and does not result in a loss of resolution or aspect ratio for the features. The generated PC masters were used to successfully replicate a wide range of microfluidic devices, including rectangular channels with aspect ratios from 0.025 to 7.3, large area spiral channels, and micropost arrays with 5 µm spacing. Moreover, fabrication of rounded features, such as semi-spherical microwells, was possible and easy. Quantitative analysis of the replicated features showed variability of <2%. The approach is low cost, does not require cleanroom setting or hazardous chemicals, and is rapid and simple. The fabricated masters are rigid and survive numerous replication cycles. Moreover, damaged or missing masters can be easily replaced by reproduction from previously cast PDMS replicas. All of these advantages make the PC masters highly desirable for long-term preservation of soft lithography masters for microfluidic devices.

Intestinal retentive devices have applications ranging from sustained oral drug delivery systems to indwelling ingestible medical devices. Current strategies to retain devices in the small intestine primarily focus on chemical anchoring using mucoadhesives or mechanical coupling using expandable devices or structures that pierce the intestinal epithelium. Here, the feasibility of intestinal retention using devices containing villi‐inspired structures that mechanically interlock with natural villi of the small intestine is evaluated. First the viability of mechanical interlocking as an intestinal retention strategy is estimated by estimating the resistance to peristaltic shear between simulated natural villi and devices with various micropost geometries and parameters. Simulations are validated in vitro by fabricating micropost array patches via multistep replica molding and performing lap‐shear tests to evaluate the interlocking performance of the fabricated microposts with artificial villi. Finally, the optimal material and design parameters of the patches that can successfully achieve retention in vivo are predicted. This study represents a proof‐of‐concept for the viability of micropost‐villi mechanical interlocking strategy to develop nonpenetrative multifunctional intestinal retentive devices for the future.

In this paper, we synergistically combine electrohydrodynamic (EHD) printing and replica molding for the fabrication of microlenses. Glycerol solution microdroplets was sprayed onto the ITO glass to form liquid mold by an EHD printing process. The liquid mold is used as a master to fabricate a polydimethylsiloxane (PDMS) mold. Finally, the desired micro-optical device can be fabricated on any substrate using a PDMS soft lithography mold. We demonstrate our strategy by generating microlenses of photocurable polymers and by characterizing their optical properties. It is a new method to rapidly and cost-effectively fabricate molds with small diameters by exploiting the advantages of EHD printing, while maintaining the parallel nature of soft-lithography.

Microneedles have been used in various applications in biomedical engineering, including drug delivery, biosensing, and vaccine delivery. In this study, we develop a novel protocol to fabricate silk fibroin/off-stoichiometry thiol-ene (OSTE) hybrid microneedle array patches. Silk fibroin, as a natural biomaterial, has been proven to be suitable as a drug carrier. Firstly, drug (we use insulin in this experiment) dissolved in silk fibroin solution is deposited on a microneedle mold and dried thoroughly. After that, silk fibroin needle tips are formed on the OSTE base by replica molding. We investigated the influence of the silk fibroin concentration on the length of silk needle tips and found that the silk concentration had a small influence on the tip length. We also tested the mechanical strength of the microneedles by inserting them into gelatin gel for dummy drug delivery tests. Such composite structures have the potential to increase the delivery efficiency by delivering the whole silk tip into the dermis.

As a breakthrough in the cost and durability of molds for nanoimprint lithography (NIL), replica molds are fabricated by injection compression molding (ICM). ICM is commonly used for optical disks such as DVDs or Blu-ray disks and is also a practical fabrication method for nanostructures. In this paper, I successfully demonstrated the fabrication of cycloolefin polymer replica molds with structures smaller than 60 nm by ICM. Furthermore, ultraviolet (UV)-NIL using these replica molds was demonstrated. UV-cured resist was replicated over an area of 60 mm diameter. The degree of replication by UV-NIL in the first usage of each replica mold had good repeatability. Because ICM is a high-throughput, low-cost process, the replica mold can be disposed of after a certain time for UV-NIL. This method leads to a high-integrity UV-NIL process of patterned media because multiple large-area replica molds can be fabricated simultaneously.