Flow Lithography (FL) is the technique used for the synthesis of hydrogel microparticles with various complex shapes and distinct chemical compositions by combining microfluidics with photolithography. Although polydimethylsiloxane (PDMS) has been used most widely as almost the sole material for FL, PDMS microfluidic chips have limitations: (1) undesired shrinkage due to the thermal expansion of masters used for replica molding and (2) interfacial delamination between two thermally cured PDMS layers. Here, we propose the utilization of ultraviolet (UV)-curable PDMS (X-34-4184) for FL as an excellent alternative material of the conventional PDMS. Our proposed utilization of the UV-curable PDMS offers three key advantages, observed in our study: (1) UV-curable PDMS exhibited almost the same oxygen permeability as the conventional PDMS. (2) The almost complete absence of shrinkage facilitated the fabrication of more precise reverse duplication of microstructures. (3) UV-cured PDMS microfluidic chips were capable of much stronger interfacial bonding so that the burst pressure increased to $0.9 MPa. Owing to these benefits, we demonstrated a substantial improvement of productivity in synthesizing polyethylene glycol diacrylate microparticles via stop flow lithography, by applying a flow time (40 ms) an order of magnitude shorter. Our results suggest that UV-cured PDMS chips can be used as a general platform for various types of flow lithography and also be employed readily in other applications where very precise replication of structures on micro-or submicrometer scales and/or strong interfacial bonding are desirable. Published by AIP Publishing. [http://dx

The new coronavirus disease 2019 (COVID-19) is posing a dire health threat to the world. It has spread to more than 202 countries, and over 470,000 cases have been confirmed globally [1]. Approximately 9,241 cases have been confirmed in Korea as of March 26, 2020 [2], and the increasing numbers of patients are causing a significant medical burden. The virus is not a conventional coronavirus that infects the human body, but is an animal-originated virus adapted to the human body as a highly contagious pathogen [3]. The frontline protection primarily used in pandemic situations is vaccination. In addition, therapeutic agents for the disease should be available [4]. However, as of now, no vaccine has been developed for COVID-19, and it is expected that a vaccine will take a relatively long time to become available for public use. Recently, considerable efforts have been made to find an effective treatment for COVID-19 by repurposing or combining existing drugs [5]. Under this emergency situation, it is especially important for high-risk individuals to thoroughly prevent COVID-19 infection by maintaining personal hygiene and using protective equipment such as masks [6]. Personal protective equipment (PPE) plays a very important role in controlling the spread of diseases through direct or indirect contact exposure. Viruses that can cause respiratory symptoms such as coronavirus,

No abstract