On-chip surface acoustic-wave driven microfluidic motors

We report on the design of two different surface acoustic wave (SAW) driven rotary motors. Both designs use 20-30 MHz transducers patterned onto Lithium Niobate (LN), geometrically tailored to generate Rayleigh waves that are incident on opposing sides of each rotor. The first design exploits the efficient coupling between SAWs and fluids by use of a fluid coupling layer between the rotor and substrate, leading to rotations of a 5 mm disc shaped rotor over 2,500 rpm with a start-up torque of 60 nN m. The second design exploits a dry friction contact between the surface and rotors for further miniaturisation. In the latter design 1 mm steel rotors are driven up to 6,000 rpm with no external preload required