Detection and removal of droplets on non-piezoelectric substrates via mode conversion of Lamb waves

A combination of detection and propulsion of droplets on glass substrates at macroscopic dimensions has been accomplished via mode conversion of 1 MHz Lamb waves excited and detected by piezoelectric interdigital transducers (IDT) attached to the substrates forming a delay line configuration . Experimental results with respect to water, oil and glycerin droplets with liquid volumes between 8 and 160 μl on hydrophobic and hydrophilic glass surfaces are reported. In order to switch from sensing to actuating the excitation voltage of the IDT has been increased from 20 Vpp to 300 Vpp and the operation mode has been changed from burst to continuous excitation. Applications of this approach are envisaged at mirrors, windows and other optical components whose function may be affected adversely by the presence of liquid droplets.