A disposable bulk-acoustic-wave microalga trapping device for real-time water monitoring.

• Simple, rapid and low-cost fabrication of a microfluidic algae trap based on PSA tape. • Simple structure with low frequency operation at 8.56 MHz and no sheath flows. • Chlorella trapping efficiency of 82–74 % at a 0.5–2.7 μl/min through-flow in a 800 μm × 85 μm channel. • Diatoms trapping efficiency of 85–79 % at a 0.5–4 μl/min through-flow in a 800 μm × 85 μm channel. • Resettable trapping of chlorella and diatoms, and potential for distributed/portable use. Recently, there has been an increase in the use of algal physiology as a convenient and useful indicator for monitoring of water quality in aquatic ecosystems. However, current methods for monitoring algal physiology are high-cost, power intensive, and have limited sensitivity for practical samples in which algal concentration is low. In order to alleviate these problems, we developed a simple-to-fabricate acoustophoretic particle trapping device that can effectively enrich various types of microalgae such as chlorella and diatoms for real-time monitoring of water quality. This microalgae trap is fabricated by embedding a piezoelectric resonator in a single channel. In comparison to previously reported acoustophoretic particle traps, this device has a simple structure and does not require sheath flows, which makes the device low cost and simple to fabricate and operate. Using Chlorella kessleri and the marine diatom Thalassiosira pseudonana as model algae, the microalgae trap has demonstrated notable particle trapping efficiencies between 82 % to 74 % for Chlorella with a through-flow of 0.5 μl/min to 2.7 μl/min and 85 % to 79 % for diatoms with a 0.5 μl/min to 4 μl/min through-flow. The trap has also shown to simultaneously trap Chlorella and diatoms at different heights of the microchannel. This device has high promise for trapping, separating and manipulating microalgae. [ABSTRACT FROM AUTHOR]