Yongha Hwang

This work reports on zeolitic imidazolate framework (ZIF)-coupled microscale resonators for highly sensitive and selective gas detection. The combination of microscale resonators and nanoscale materials simultaneously permits the benefit of larger capture area for adsorption from the resonator and enhanced surface adsorption capacity from the nanoscale ZIF structure. Dielectrophoresis (DEP) was demonstrated as a novel method for directly assembling concentrated ZIF nanoparticles on targeted regi

This review examines the state of the art for manufacturing non-planar miniature channels and actuators from PDMS, where non-planar structures are defined here as those beyond simple extrusions of 2D designs, either with rounded or variable cross sections or with an emergence of the channel trajectory out-of-plane. The motivation for 3D PDMS structures and advances in their fabrication are described, focusing on geometries that were previously unachievable through conventional microfabrication.

This work presents for the first time a zeolitic imidazolate framework (ZIF)-coupled resonant gas sensor whose sensitivity shows an improvement up to 78 times over bare silicon resonant sensors with identical dimensions. ZIFs are among the highest surface area material used for resonant-based sensing. We utilize high surface area-to-volume ratios of ZIFs to demonstrate how a microresonator coupled with ZIF crystals can provide high sensitivity to chemical vapors.

This paper demonstrates a commercial-level field-portable lens-free cell analyzer called the NaviCell (No-stain and Automated Versatile Innovative cell analyzer) capable of automatically analyzing cell count and viability without employing an optical microscope and reagents. Based on the lens-free shadow imaging technique, the NaviCell (162 × 135 × 138 mm³ and 1.02 kg) has the advantage of providing analysis results with improved standard deviation between measurement results, owing to its large

This letter investigates the capillary filling in polydimethylsiloxane (PDMS) microchannels using 3-D printed molds to produce channels with circular cross sections. The circular cross sections are prevalent in biology and anatomy, yet they cannot readily be mimicked with existing soft-lithography techniques. The molds are printed directly from computer-aided design files, making rapid prototyping of microfluidic devices possible in hours, demonstrating microscale features in PDMS channels. The

Typical pneumatic soft micro actuators can be manufactured without using heavy driving components such as pumps and power supplies by adopting an independent battery-powered mechanism. In this study, a thermopneumatically operated soft micro bellows actuator was manufactured, and the standalone operation of the actuator was experimentally validated. Thermopneumatic actuation is based on heating a sealed cavity inside the elastomer of the actuator to raise the pressure, leading to deflection of t

A modular soft actuator with snakeskin-inspired scales that generates an anisotropic friction force is designed and evaluated in this study. The actuator makes it possible to fabricate soft robots that can move on various surfaces in the natural environment. For existing modulus soft robots, additional connectors and several independent pneumatic pumps are required. However, we designed precise connection and snake-scale structures integrated with a single pneumatic modular actuator unit. The pr