Lithography-free, crystal-based multiresonant lamb waves for reconfigurable microparticle manipulation

Acoustic wave microfluidic devices, in particular those that exploit the use of surface acoustic waves (SAWs), have been demonstrated as a powerful tool for driving microfluidic actuation and bioparticle manipulation. A limitation of these devices, however, is the requirement for the fabrication of interdigital transducer electrodes on the piezoelectric substrate, which upon excitation of an AC electrical signal at resonance, generates the SAW. Not only is the lithographic fabrication a costly and cumbersome step, the necessity for driving the interdigitated transducers (IDTs) at resonance means that the device typically operates at a single frequency at its fundamental resonant state; the higher harmonics that may be available are often weak and negligible. As such, reconfiguring a device for different operating frequencies is usually difficult and almost always avoided. Here, we show a Lamb wave device which can mimic the microfluidic actuation and particle manipulation of SAW devices, but which can be fabricated without requiring any lithographic procedures. Moreover, we show that a large number of resonances are available, whose modes depends on harmonics associated with the substrate thickness, and, in particular, demonstrate this utility briefly for reconfigurable particle patterning.