We demonstrate a simple and efficient device for the continuous label-free separation of microparticles using travelling surface acoustic waves (TSAW). A focusing interdigitated unidirectional transducer released high frequency (133.3 MHz) TSAW normal to the fluid flow direction to segregate 3 μm particles from 10 μm particles with a separation efficiency of 100%. The TSAW based separator does not necessitate a tight alignment of the PDMS microchannel with the transducer.