A Low‐Voltage Microfluidic Valve Based upon a Reversible Hydrophobicity Effect

Abstract

A microfluidic valve is reported based on a reversible hydrophobicity effect via the growth and retraction of nanotextured metal filaments on the surface of a solid electrolyte. The valve is integrated onto the bottom of the channel and actuated by a DC voltage. The dendritic silver filaments are tens to hundreds of nanometers in height and can be isolated from the channel fluid by a thin Parylene layer. An applied bias of 6 V or less grows or dissolves the filaments, depending on the polarity, and the roughness so created alters the fluid‐surface interface, manipulating hydrophobicity of the interface, transitioning from the lotus effect to the petal effect. To demonstrate this valve, the fluid flow in a poly(dimethylsiloxane)‐enclosed microfluidic channel of up to 30 μm in depth and up to 250 μm in width is stopped and restarted within ≈25 s of actuation. The effect is nonvolatile, thus no static power is required to retain the on/off states of the valve.

Materials Characterization and Electrical Performance of Bilayer Structures for Enhanced Electrodeposition in Programmable Metallization Cells

“…The best device (device 3 family) showed a switching speed of 5.71 μm s −1 at 4 V, the threshold voltage of 2 V compared to switching speed of 4 μm s −1 at 4 V, and the threshold voltage of 4 V for a chalcogenide‐based lateral PMC device reported in ref. [6]. Hence, comparable switching speeds and threshold voltage to chalcogenide‐based lateral PMCs can be achieved by using the proposed bilayers.…”

“…An extensive surface electrodeposit alters the physical properties of the region on which it is formed, including its mass, stiffness, fluid contact angle, and electrical resistance, and can therefore be used in a variety of applications. These include microfluidic valves, [6,7] timers, [8] radio frequency (RF) switches, [9] and tuning elements in microelectromechanical systems (MEMS) resonators and microphones; [10][11][12] however, several challenges remain for more widespread adoption of this technology. These challenges include manufacturability, material compatibility with standard semiconductor processing, and speed of operation.Important device characteristics such as operating voltage and speed are largely dependent on materials properties such as electronic and ionic conductivities of the medium that supports the electrodeposition process.…”