This paper describes the utilization of vacuum to fill complex microchannels with liquid metal. Microchannels filled with liquid metal are useful as conductors for soft and stretchable electronics, as well as for microfluidic components such as electrodes, antennas, pumps, or heaters. Liquid metals are often injected manually into the inlet of a microchannel using a syringe. Injection can only occur if displaced air in the channels has a pathway to escape, which is usually accomplished using outlets. The positive pressure (relative to atmosphere) needed to inject fluids can also cause leaks or delamination of the channels during injection. Here we show a simple and hands-free method to fill microchannels with liquid metal that addresses these issues. The process begins by covering a single inlet with liquid metal. Placing the entire structure in a vacuum chamber removes the air from the channels and the surrounding elastomer. Restoring atmospheric pressure in the chamber creates a positive pressure differential that pushes the metal into the channels. Experiments and a simple model of the filling process both suggest that the elastomeric channel walls absorb residual air displaced by the metal as it fills the channels. Thus, the metal can fill dead-ends with features as small as several microns and branched structures within seconds without the need for any outlets. The method can also fill completely serpentine microchannels up to a few meters in length. The ability to fill dense and complex geometries with liquid metal in this manner may enable broader application of liquid metals in electronic and microfluidic applications.

中文翻译：

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用液态金属真空填充复杂的微通道

本文介绍了利用真空将液态金属填充到复杂的微通道中的方法。充满液态金属的微通道可用作柔软和可拉伸电子产品以及微流体组件（如电极，天线，泵或加热器）的导体。通常使用注射器将液态金属手动注入微通道的入口。仅当通道中的置换空气具有逃逸路径时才可进行喷射，这通常是使用出口完成的。注入流体所需的正压（相对于大气）还会在注入过程中引起通道泄漏或分层。在这里，我们展示了一种简单且免提的方法，可以用液态金属填充微通道，从而解决了这些问题。该过程开始于用液态金属覆盖单个入口。将整个结构放置在真空室中，可以从通道和周围的弹性体中清除空气。恢复腔室内的大气压会产生正压差，从而将金属推入通道。实验和填充过程的简单模型均表明，弹性通道壁吸收了金属填充通道时被金属置换的残留空气。因此，金属可以在几秒钟内以小至几微米的特征填充末端，并在不需要任何出口的情况下形成分支结构。该方法还可以完全填充长达数米的蛇形微通道。以这种方式用液态金属填充致密和复杂的几何形状的能力可以使液态金属在电子和微流体应用中得到更广泛的应用。