Bi-directional micro relays with liquid-metal wetted contacts

Micromachined relays with liquid-metal wetted contacts have been successfully demonstrated using bidirectional electrothermal electromagnetic actuators. MetalMUMPs process, a 6-mask foundry process with 8 thin film layers and a 20μm nickel structural layer, is used to build these relays. Experimentally, the relay can be operated with 0.25 volt and 0.5 ampere and the breakdown voltage and the off-state resistance is greater than 200V and 100MΩ, respectively. The contact resistances of the initial gold-to-gold contacts are around 0.3Ω, while gold contacts wetted with a thin layer of liquid gallium alloy (melting point at -20°C) can achieve contact resistance as low as 0.015Ω. As such, this bi-directional relay can perform single pole double throw (SPDT) function with lower contact resistance using liquid-metal contacts.