Stimuli-responsive gel based microfluidic switch

弹性不稳定性，如表面的屈曲、起皱和折痕，以及断裂转变，历来都是薄膜机械失效的代表。然而，情况并非如此，弹性不稳定性，特别是在柔软的聚合物表面上，可以提供可逆控制、传感或驱动，以响应明确定义的信号或环境的变化。在之前的工作中，我已经证明，在特殊设计的底层电极支持的凝胶表面上，表面不稳定性可以被电触发。演示的驱动需要2 - 4v的低电压。(副词板牙。Vol 25, 2013)和快速驱动也获得响应时间小于1秒。这个项目利用以上的见解，结合我对表面不稳定性（力学）和材料科学的既定理解和经验，制作了一个强大的电压控制开关来调节微通道中的液体流动。实际上，该项目将侧重于理解基于水凝胶的微系统，该系统将允许定量确定以下内容：1)屈曲发生的条件以及屈曲的发生如何取决于软表面的材料特性、环境参数（离子值、温度、pH值）和电极几何形状；Ii)屈曲的形态与软表面的材料特性、驱动前的初始膨胀状态和电极几何形状之间的关系；Iii)如何修剪凝胶层的屈曲形状，以有效控制微环境下的流体流动。利用这些实验的理解，将开发一种基于响应凝胶的开关来动态调节微通道中的液体流动。该项目的工作是跨学科的，包括力学、材料科学和微工程。从光刻结构电极到凝胶化学，一系列的材料创新将被使用。该项目中描述的具有“按需”驱动的被动阀门技术处于广泛的科学背景下（化学、应用物理、化学物理、微工程、化学工程和电化学）。该项目将为未来开发具有高集成度和液体流动自动化的新型微流体装置提供所需的理解。

Elastic instabilities such as buckling, wrinkling and creasing of surfaces, and snapping transitions have historically represented mechanical failure in thin films. However, this does not have to be the case and elastic instabilities, particularly on soft polymer surfaces, can provide reversible control, sensing or actuation in response to well-defined signals or changes in their environment. In previous work, I have shown that surface instabilities can be electrically triggered on a gel surface supported by specifically designed underlying electrodes. The demonstrated actuation required a low voltage of 2 - 4 V. (Adv Mater. Vol 25, 2013) and a rapid actuation was also obtained with response times less than 1 second. This project uses the above insights together with my established understanding and experience in surface instability (mechanics) and materials science to produce a robust electric voltage controlled switch to regulate the liquid flow in a micro-channel. Practically, the project will focus on understanding a hydrogel based micro-system that will allow quantitative determination of the following: i) the conditions under which buckling occurs and how the onset of buckling depends on the materials properties of the soft surface, the environmental parameters (Ionic values, temperature, pH values) and the electrode geometries; ii) how the morphology of buckling relates to the materials properties of the soft surface, the initial swelling state prior to the actuation, and the electrode geometries; iii) how to trim the buckled shape of the gel layer to effectively control the fluid flow in a micro-environment. Using the understanding from these experiments, a responsive gel based switch will be developed to dynamically regulate the liquid flow in a micro-channel. The work of this project is cross disciplinary and includes mechanics, materials science and micro-engineering. A range of materials innovations will be used from lithographically produced structural electrodes to gel chemistry. The passive valve technology with an 'on-demand' actuation described in this project is situated in a broad scientific context (chemistry, applied physics, chemical-physics, micro-engineering, chemical engineering, and electro-chemistry). The project will provide the understanding needed to allow future development of novel micro-fluidic devices with high integratibility and automation of liquid flow.