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 degrees 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.