4A-1 Low-Power Droplet Manipulation Employing High-Frequency Surface Acoustic Waves

Recently, droplet manipulation working with low driving power was developed by using surface acoustic wave (SAW) technology. The manipulator was driven at a relatively high frequency of 350 MHz to increase the SAW power density. First, a single phase unidirectional transducer (SPUDT) was designed. Because of its low insertion loss of 1.5 dB and high directivity of 10 dB, the SPUDT successfully conveyed a 100-nl water droplet with RF input power of 18 dBm (60 mW). Second, the SPUDT design was extended to a curved transducer to focus and launch the SAW energy into a narrow waveguide. Owing to the increased SAW power density, the required SAW power was reduced to 15 dBm (30 mW) for a 100-nl water droplet and to 12 dBm (15 mW) for a 20-nl water droplet, respectively