Continuous roller nanoimprinting: next generation lithography.

Nanoimprint lithography (NIL) is a cost-effective and high-throughput technique for replicating nanoscale structures that does not require expensive light sources for advanced photolithography equipment. NIL overcomes the limitations of light diffraction or beam scattering in traditional photolithography and is suitable for replicating nanoscale structures with high resolution. Roller nanoimprint lithography (R-NIL) is the most common NIL technique benefiting large-scale, continuous, and efficient industrial production. In the past two decades, a range of R-NIL equipment has emerged to meet the industrial needs for applications including biomedical devices, semiconductors, flexible electronics, optical films, and interface functional materials. R-NIL equipment has a simple and compact design, which allows multiple units to be clustered together for increased productivity. These units include transmission control, resist coating, resist curing, and imprinting. This critical review summarizes the hitherto R-NIL processes, their typical technical problems, and corresponding solutions and gives guidelines for developing advanced R-NIL equipment.

Current and Future Perspectives on Microfluidic Tear Analytic Devices.

Most current invasive analytic devices for disease diagnosis and monitoring require the collection of blood, which causes great discomfort for patients and may potentially cause infection. This explains the great need for noninvasive devices that utilize other bodily fluids like sweat, saliva, tears, or urine. Among them, eye tears are easily accessible, less complex in composition, and less susceptible to dilution. Tears also contain valuable clinical information for the diagnosis of ocular and systemic diseases as the tear analyte level shows great correlation with the blood analyte level. These unique advantages make tears a promising platform for use in clinical settings. As the volume of tear film and the rate of tear flow are only microliters in size, the use of microfluidic technology in analytic devices allows minimal sample consumption. Hence, more and more microfluidic tear analytic devices have been proposed, and their working mechanisms can be broadly categorized into four main types: (a) electrochemical, (b) photonic crystals, (c) fluorescence, and (d) colorimetry. These devices are being developed toward the application of point-of-care tests with rapid yet accurate results. This review aims to provide a general overview of the recent developmental trend of microfluidic devices for tear analysis. Moreover, the fundamental principle behind each type of device along with their strengths and weaknesses will be discussed, especially in terms of their abilities and potential in being used in point-of-care settings.

Ultrafast Microdroplet Generation and High-Density Microparticle Arraying Based on Biomimetic Nepenthes Peristome Surfaces.

Manipulation of massive droplets, particles, as well as cells has enabled wide applications. However, most existing technologies require complicated processes, operations, or external setup. This article demonstrates the employment of biomimetic Nepenthes peristome surfaces (NPS) in achieving ultrafast microdroplet generation and high-density microparticle arraying, with the assistance of curvature-induced Laplace pressure in slipping mode and evaporation-driven Marangoni effect in climbing mode, respectively. Different wetting phenomena on the biomimetic NPS were observed under variable contact angles and tilting angles, strongly affecting the microdroplet generation and microparticle array. As the optimal results, 5 µm-size microparticles were arrayed with 85% coverage rate in 65 s and 20 µm-size microdroplets were arrayed with 100% coverage rate in 3 s. In this study, this well-designed bionic surface shows excellent performances as an ultrafast, universal, and straightforward approach to capture and array micro-objects in aqueous solutions for various biological and chemical analyses.

High-throughput Droplet Array Generated by Roller Nanoimprint Lithography with Biomimetic Surfaces.

For the first time, we exploited a novel pump-free and high-throughput droplet generation method using the roller nanoimprint technology on biomimetic peristome surface of nepenthes. The biomimetic nepenthes peristome surfaces with oblique re-entrant microcavities and sharp edges led to facile directional liquid filling and high-efficiency droplet generation under the roller embossing, and the sealant on polyethylene terephthalate (PET) substrate encapsulated thousands of microcavities to form a high-density droplet array with good uniformity.