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. Author manuscript; available in PMC: 2018 Jun 13.
Published in final edited form as: Anal Methods. 2017 Jun 13;9(28):4112–4134. doi: 10.1039/C7AY00690J

Fig. 1.

Fig. 1

(a) Schematic of a single, planar IDT configuration, where the SAW propagates away from the IDT in both directions. Typically, an absorbent material such as a gel is used to inhibit reflection of the backward traveling SAW. The top and side views show a typical IDT structure with the interdigitated electrode fingers spaced λ/2. (b) Side views to two common actuation strategies. On the left is a traveling wave configuration, where a single IDT induces a SAW propagating away from the electrodes. Generally, the SAW propagates at the speed of sound of the crystal, which is typically ~103 m/s, but has an out-of-plane displacement amplitude of only ~10 nm. However, the displacement speed and acceleration can be very high, ~1 m/s and 105 m/s2. On the right shows two sets of IDTs that generate counter-propagating SAWs. The SAWs interfere to form a standing wave.