New research from Kim combines smart composite materials and digital microfluidics

Since most of the sensitive and standardized bio-analytical techniques work in the liquid medium, the lab-on-a-chip system should be able to efficiently handle liquid solutions in micro/nano scale. Currently, most of these systems have been developed based on the continuous flow system, which lacks device reconfigurability. Because of this, scientific focus has transitioned to droplet-based lab-on-a-chip systems, which typically utilize electrowetting – a research area called digital microfluidics. However, using electrowetting causes many issues, including high-voltage requirements and biofouling, hindering many real applications.

With a new three-year grant from the National Science Foundation, Associate Professor Seok Kim aims to provide a straightforward pathway to a new digital microfluidic platform without electrowetting-related limitations. His proposed platform exploits a purely mechanical means to drive discrete liquid droplets in a rapid, flexible, programmable, and reconfigurable manner – a method that could be compared to state-of-the-art digital microfluidic systems. His work will also generate information and demonstration materials that can be directly used to promote interest in materials, microfluidics, interfacial science, and micro/nanotechnology to students and the general public.

Under his project – “Magnetically Actuated Black Silicon Ratchet Surfaces for Digital Microfluidics” – Kim will explore the dynamically tunable surface morphology and consequential interfacial wettability using a black silicon ratchet surface in order to seek a new strategy to manipulate liquid droplets for the advancement of digital microfluidics. The proposed ratchet surface involves superhydrophobic black silicon scales on elastomer micropillars. This ensures that individual signals actuate individual scales and change the entire surface morphology, forming a black silicon ratchet surface that drives liquid droplets. As a result, droplets are essentially driven mechanically, not electrically. Kim also expects that conical nanostructures on the black silicon surface and/or the slippery liquid infused porous surfaces to be integrated will significantly reduce biofouling. 

Kim’s expertise in mechanics, materials, manufacturing, and microfluidics on the project could introduce a new interdisciplinary research area across smart composite materials and digital microfluidics.

Kim joined the MechSE Department in 2011. His research focuses on responsive surfaces, micromanufacturing, and MEMS/NEMS.