Fast washing micro-reactor on piezoelectric substrate based on surface acoustic wave

Residual contamination in micro-reactor is usually a source of errors for micro-fluidic biochemical analysis system. A new method for fast washing micro-reactor has been proposed. An interdigital transducer with 27.7MHz center frequency and a reflecting gate have been fabricated on 128° YX-LiNbO₃ substrate. A micro-reactor is on the propagation path of the piezoelectric substrate. Washing agent is piped on the piezoelectric substrate at first and then actuated to the micro-reactor by surface acoustic wave. As soon as the washing agent arrives at the micro-rector on the piezoelectric substrate, the RF signal power added on the IDT is decreased to ensure that the washing agent is not actuated but can be rotated by small amplitude SAW. Then the contamination in the micro-reactor quickly dissolves with the washing agent due to the small amplitude SAW. At last, the contamination together with the washing agent in the micro-reactor is actuated and washing operation is finished. Dried red dye contamination on micro-reactor was washed by water washing agent, and dried potassium iodide and sodium thiosulfate mixed solution contamination was also washed by water washing agent, which were all by help of SAW. Washing effects were measured by observation or quantitative analysis using gray values. The washing method is great useful for “lab on a piezoelectric substrate” due to without any extra size and cost.