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하이드로젤에 의해 구동되는 종이 미세 유체 장치 용 펌프
서재덕(Jaedeok Seo),김원정(Wonjung Kim) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11
As paper-based microfluidic devices become diverse and used for detailed diagnostics, developers are making efforts to increase and control the flow in paper. The flow in the paper is the capillary flow described by the Washburn’s equation. The flow is determined by the size of pore and the properties of the working fluid. In order to generate a flowrate over this capillary flow, a high pressure is required to overcome the viscous resistance produced by the small size paper pore. We have used hydrogel as an energy source to create this high pressure. Hydrogels have the ability to absorb more than 100 times their volume of water and are already being applied in a variety of industrial and environmental applications. We have succeeded in producing a large negative pressure by creating a structure that maximizes the ability of the hydrogel to absorb water. We have developed a non-powered pump that can be used in paper-based devices using hydrogels. The pump can generate more than 20 times higher flowrate than the capillary flow in paper channel for more than 4 hours.
종이의 액체 흡수 시 셀룰로오스 섬유 내부 공극의 영향
서재덕(Jaedeok Seo),장수영(Sooyoung Chang),홍석빈(Seokbin Hong),이덕규(Duck-Gyu Lee),김원정(Wonjung Kim) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12
The accurate control of liquid imbibition in paper is crucial for the applications of paper to microfluidic devices. However, the classical model for capillary flow in porous media, Washburn law, has limitations in predicting the flow in a complex fiber network such as paper. Although various physical explanations for the limitations have been suggested, we here newly report that intra-fiber pores of cellulose fibers are mainly responsible for the limited accuracy of Washburn law. Our experimental study shows that liquid may imbibe through the intra-fiber pores in cellulose fibers as well as through the inter-fiber pores formed by fiber network. We theoretically developed a hydrodynamic model for liquid imbibition through paper with the consideration of intra-fiber pores. Our theoretical predictions show a good agreement with the experimental observations, leading to the physical reasons behind the limits of Washburn law.