Microfluidic Mixing Triggered by an External LED Illumination

The mixing of confined liquids is a central yet challenging operation in miniaturized devices. Microfluidic mixing is usually achieved with passive mixers that are robust but poorly flexible, or active mixers that offer dynamic control but mainly rely on electrical or mechanical transducers, which increase the fragility, cost, and complexity of the device. Here, we describe the first remote and reversible control of microfluidic mixing triggered by a light illumination simply provided by an external LED illumination device. The approach is based on the light-induced generation of water microdroplets acting as reversible stirrers of two continuous oil phase flows containing samples to be mixed. We demonstrate many cycles of reversible photoinduced transitions between a nonmixing behavior and full homogenization of the two oil phases. The method is cheap, portable, and adaptable to many device configurations, thus constituting an essential brick for the generation of future all-optofluidic chip.在微型装置中，密闭液体的混合是一项核心且极具挑战性的操作。微流控混合通常通过采用结构坚固但灵活性较差的被动混合器，或提供动态控制的主动混合器来实现，后者主要依赖于电或机械传感器，这增加了设备的脆弱性、成本和复杂性。在此，我们描述了一种首次通过外部LED照明设备提供的简单光照明触发的远程且可逆的微流控混合控制方法。该方法基于光诱导生成的水微滴，这些微滴作为可逆搅拌剂，用于搅拌包含待混合样品的两个连续油相流。我们展示了在非混合行为与两个油相完全均质化之间进行多次可逆的光诱导转换。该方法成本低廉、便携且适用于多种设备配置，因而成为构建未来全光流体芯片的基石。