Although acoustic microscopy at ultrahigh ultrasound frequency (100 MHz – 1 GHz) has been used in non-destructive evaluation of materials and biomedical imaging for decades, its applications in biology and medicine have remained to be limited. The primary reasons are (1) high cost and (2) few advantages over optical microscopy. Biomedical applications of ultrasound at these frequencies other then imaging however have been mostly overlooked. At UHF frequencies, the width of an ultrasound beam is of only a few microns, approaching the dimensions of many cells, hence it may be called “ultrasound microbeam”. Ultrasound microbeam may have many applications in cellular bioengineering. Acoustic tweezer, and acoustic cell sorter are just two examples.
Both sensitive UHF single element transducers and driving and receiving electronics must be developed for the further advance of ultrasound microbeam. Traditionally piezoelectric materials like ZnO and PVDF have been used for UHF transducer fabrication. These materials although possesses a desirable low dielectric constant for single element transducers, have a very serious shortcoming, a very low electromechanical coupling coefficient.  In order to improve the performance of UHF transducers, a variety of piezoelectric thin films including PZT and KNN-LSO have been developed and evaluated. Transducers at frequencies as high as 200 MHz have been prepared from these materials, yielding a bandwidth of 30-60%. They have been successfully used for applications in cell-sorting and trapping.
Preliminary experimental results have been obtained to demonstrate potential cellular applications of ultrasound microbeam. Efforts are now underway to utilize ultrasound microbeam in interrogating cellular elasticity and mechanotransduction.