It is essential to control concentration gradients at specific locations for many biochemical experiments. This paper proposes a tunable concentration gradient generator actuated by acoustically oscillating bubbles trapped in the bubble channels using a controllable position based on the gas permeability of polydimethylsiloxane (PDMS). The gradient generator consists of a glass substrate, a PDMS chip, and a piezoelectric transducer. When the trapped bubbles are activated by acoustic waves, the solution near the gas–liquid interface is mixed. The volume of the bubbles and the position of the gas–liquid interface are regulated through the permeability of the PDMS wall. The tunable concentration gradient can be realized by changing the numbers and positions of the bubbles that enable the mixing of fluids in the main channel, and the amplitude of the applied voltage. This new device is easy to fabricate, responsive, and biocompatible, and therefore has great application prospects. In particular, it is suitable for biological research with high requirements for temporal controllability.

中文翻译：

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一种浓度梯度可调发生器，其声振荡气泡的位置可调。

对于许多生化实验而言，控制特定位置的浓度梯度至关重要。本文提出了一种可调节的浓度梯度发生器，该发生器通过基于聚二甲基硅氧烷（PDMS）的气体渗透率的可控制位置，通过在气泡通道中捕获的气泡进行声学振荡来启动。梯度发生器由玻璃基板，PDMS芯片和压电传感器组成。当捕获的气泡被声波激活时，气液界面附近的溶液就会混合。气泡的体积和气液界面的位置通过PDMS壁的渗透性来调节。可调浓度梯度可以通过更改气泡的数量和位置来实现，这些气泡和气泡可以使主通道中的流体混合，和施加电压的幅度。这种新设备易于制造，反应灵敏且具有生物相容性，因此具有广阔的应用前景。特别适用于对时间可控性有较高要求的生物学研究。