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.

在微型化装置中，封闭液体的混合是一项核心且极具挑战性的操作。微流控混合通常依赖于被动混合器，虽然其结构坚固，但灵活性较差；或者采用主动混合器，这类混合器能够提供动态控制，但主要依赖电气或机械传感器，这增加了装置的脆弱性、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射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，这些微滴充当两种连续油相流（其中包含待混合的样品）的可逆搅拌剂。我们展示了多次可逆的光诱导转换，从非混合行为到两种油相的完全均质化。此方法成本低廉、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。