Conformal switchable superhydrophobic/hydrophilic surfaces for microscale flow control

• Published in: Colloids and surfaces. A, Physicochemical and engineering aspects Physicochemical and engineering aspects, 2009-02, Vol.333 (1), p.187-193
• Main Authors: Chunder, Anindarupa, Etcheverry, Kenneth, Londe, Ghanashyam, Cho, Hyoung J., Zhai, Lei
• Format: Article
• Language: English
• Subjects: Chemistry; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Hydrophilic; Hydrophobic; Microfluidic; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Surface physical chemistry; Surfaces; Switchable
• ISSN: 0927-7757; 1873-4359
• DOI: 10.1016/j.colsurfa.2008.09.044

The development of microvalves is essential to realize a fully integrated system for nano/microliter fluid handling in microfluidic devices. Microvalves that utilize passive fluidic manipulation employ a hydrophobic surface in a microchannel network in which the operation is controlled by the interfacial tension of the liquid–air–solid interface. In order to obtain a switchable valve in microfluidic channels, conformal hydrophobic/hydrophilic and superhydrophobic/hydrophilic thermal switchable surfaces were fabricated by the layer-by-layer deposition of poly(allylamine hydrochloride) (PAH) and silica nanoparticles followed by the functionalization of a thermosensitive polymer-poly( N-isopropylacrylamide) (PNIPAAm) and perfluorosilane. A fully integrated microfluidic valve using a thermal switchable superhydrophobic/hydrophilic polymer patch has been fabricated. At 70 °C, the valve is superhydrophobic and stops the water flow (closing status) while at room temperature, the patch becomes hydrophilic, and allows the flow (opening status).