An automatic-recovery inertial switch based on a gallium-indium metal droplet

In this paper, an automatic-recovery inertial switch is presented which for the first time adopts gallium–indium (EGaIn) as the switching metal droplet. The device consists of a glass substrate with patterned sensing electrodes, a PDMS microfluidic chip with microchannels and microvalves and a metal droplet. Here, we used EGaIn as the conductive element of the switch because it has several advantages compared with other conductive materials such as water or mercury. Specifically, the proposed device has the ability to automatically recover and can be used repeatedly. In the initial off-state, the droplet is stored in the reservoir. During the working state, the metal droplet passes through the channel and connects the sensing electrodes when the acceleration exceeds the designed threshold level. After that, the EGaIn will return to its original position by a subtle use of its structural characteristics.