Robust Si-Based Membranes for Fluid Control in Microbatteries Using Superlyophobic Nanostructures

Mechanically robust superhydrophobic Si-based membranes are described. The membranes are prepared using microelectromechanical-systems-type processing and implement “nanonail” design features that enable superlyophobic (also called omniphobic, superolephobic) behavior. A variety of low- and high-surface-tension liquids are repelled by such porous membranes without liquid penetrating into the pores of the membrane. Electrowetting transitions have been successfully implemented as a way to demonstrate electrically triggered and tunable permeability of the structures. Long-term stability of the hydrophobic coatings based on fluoropolymers has been evaluated using contact angle measurements. Among those, Teflon-based coatings tend to show the best survivability in aqueous and organic electrolytes for periods longer than 200 days of continuous exposure at room temperature and at 60 ^°C. Such robust membranes are currently used in reserve microbattery technology and microfluidic devices and, potentially, could enable other applications involving fluid separation, fuel cells, and filtration.