We present a flexible and noninvasive approach for efficient continuous micromixing and microreaction based on direct current-induced thermal buoyancy convection in a single microfluidic unit. Theoretically, microfluids in this microsystem are unevenly heated by powering the asymmetrically arranged microheater. The thermal buoyancy convection is then formed to induce microvortices that cause effective fluidic interface disturbance, thereby promoting the diffusion and convective mass transfer. The temperature distribution and the convection flow in the microchip are first characterized and studied, which can be flexibly adjusted by changing the DC voltage. Then the mixing performance of the presented method is validated by joint numerical and experimental analyses. Specifically, at U = 7 V, the mixing efficiencies are higher than 90% as the flow rate is lower than Q_v= 600 nL/s. So high-quality chemical or biochemical reactions needing both suitable heating and efficient mixing can be achieved using this method. Finally, as one example, we use this method to synthesize nano-sized cuprous oxide (Cu₂O) particles by effectively mixing the Benedict’s solution and glucose buffer. Remarkably, the particle size can be tuned by changing the voltage and the concentration of Benedict’s solution. Therefore, this micromixer can be attractive for diverse applications needing homogeneous sample mixtures.

我们提出了一种基于直流电在单个微流体单元中引起的热浮力对流的高效连续微混合和微反应的灵活且非侵入性的方法。从理论上讲，通过为不对称布置的微型加热器供电，该微型系统中的微流体会被不均匀地加热。然后形成热浮力对流，以引起引起有效流体界面扰动的微涡旋，从而促进扩散和对流传质。首先对微芯片中的温度分布和对流进行了表征和研究，可以通过改变直流电压来灵活地进行调节。然后通过数值分析和实验分析验证了所提方法的混合性能。具体来说，在U = 7 V时，由于流速低于Q _v = 600 nL / s ，因此混合效率高于90％。因此，使用该方法可以实现既需要适当加热又需要有效混合的高质量化学或生化反应。最后，作为一个例子，我们使用这种方法通过有效地混合本尼迪克特溶液和葡萄糖缓冲液来合成纳米级氧化亚铜（Cu ₂ O）颗粒。值得注意的是，可以通过改变电压和本尼迪克特溶液的浓度来调节粒径。因此，这种微型混合器对于需要均质样品混合物的各种应用可能具有吸引力。