[세미나] 다공성 연성물질의 탄성 유체역학(하종현 박사/University of Illinois at Urbana-Champaign)
세미나 개최 안내
기계공학과 김형수 교수의 주관으로, 하종현 박사님을 연사로 모시고 아래와 같은 주제로 세미나가 개최될 예정입니다.
관심있는 분들의 많은 참석 부탁드립니다.
1. 강연자 : 하종현 박사
-소속 : University of Illinois at Urbana-Champaign
-일시 : 2020년 9월 24일(목) 오후 2시~3시
-장소 : N7 기계공학동 E1 세미나실
3. 제목 : 다공성 연성물질의 탄성 유체역학
(Elastohydrodynamics in soft porous media)
Soft porous structures can change their shapes via liquid transportation such as capillary flows, diffusion, and osmosis. Such fluid-sloid interactions in microscale can be observed in the swelling of cellulose sponges, plant movements, and clustering of wet hair. Here, we study and investigate various morphing modes of soft porous media, which follows four topics: swelling, coiling, assembling, and collapsing.
We first explore capillary wicking in cellulose sponge, which has heterogeneous porosity. Our experiments uncover a power law of the wicking height versus time distinct from that for nonswelling sponges. The observation using environmental scanning electron microscopy reveals the coalescence of microscale wall pores with wetting, which allows us to build a mathematical model for pore size evolution and the consequent wicking dynamics. Secondly, we analyze the morphology of the helix formed by Pelargonium seed awn and fabricate artificial hygroresponsive helical actuators by depositing aligned nanofibers. Based on the laminate composite plate theory, we develop theoretical model to predict the shape of the entire helix. Our model agrees well with the experimental results of both the biological and the artificial actuators. Thirdly, we report intriguing self-assembly of hair arranged in hollow bundles driven by capillarity, elasticity, and hydrodynamics. Bundles emerging from a liquid bath shrink but remain hollow at slow drainage. At fast drainage, however, the bundles fully close before the liquid can drains through the hair. Scaling laws predict this reversible hair morphing.
Lastly, we develop the switchable polymeric morphing system, based on the foregoing studies. We manufacture the flexible fin structures with the bottom channel to supply and drain the liquid. By changing the location and the speed of the liquid drainage, we show the controllable actuation system with various deformation modes.