Surface acoustic wave controlled integrated band-pass filter

We introduce a microfluidic band-pass filter for particles that is fully integrated in a polydimethylsiloxane-based microchannel device. This acoustic filter allows a continuous and label-free separation of particles. To demonstrate the functionality, mixtures of particles with different sizes are exposed to propagating surface acoustic waves generated by two laterally displaced interdigitated transducers, one on each side of the microchannel. Dependent on the frequency used, a specific size or even a size range of particles can be extracted. We sort particles of sizes of ~1–10 µm and estimate the size resolution to be smaller than ∆r < 0.88 µm. We examine the performance of the device and achieve a throughput of ~105 particles/s with an efficiency as high as 99 %.