SU-8-Based Nanocomposites for Acoustical Matching Layer

SU-8, an epoxy-based photoresist, was introduced as the acoustical matching layer between silicon and water for lab-on-chip applications integrating acoustic characterization. Acoustical performances, including the acoustic longitudinal wave velocity and attenuation of the SU-8-based matching layer, were characterized at a frequency of 1 GHz at room temperature. The gain in echo characterization with a SU-8/SiO(2) bilayer and with different nanocomposite inonolayers made of SU-8 and TiO(2) nanoparticles (size around 35 rim) between silicon and water was characterized as being above 10 dB in each case. With the increase of concentration of TiO(2) in SU-8 based composites from 0 to 30 wt%, acoustical impedance of the nanocomposites increased from about 3 to 6 MRayls, respectively. The acoustical attenuation in the nanocomposites is between 0.5 and 0.6 dB/mu m. The most efficient matching was obtained with the nanocomposite integrating 30 wt% TiO(2) nanoparticles, with which the enhanced loss is about 0.34 dB as the attenuation is about 0.5 dB/mu m. This type of matching layer has potential applications in lab-on-chip technology for high frequency transducers or in the fabrication of high frequency piezocomposites.