Stimuli-responsive gel based microfluidic switch

弹性不稳定性，如表面的弯曲、起皱和折皱，以及折断转变，历史上都代表着薄膜的机械失效。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，可以提供可逆的控制、传感或驱动，以响应明确定义的信号或其环境的变化。在以前的工作中，我已经证明了表面不稳定性可以在由特殊设计的底层电极支撑的凝胶表面上被电触发。所演示的驱动需要2-4V的低电压。Vol25,2013)，并且还获得了响应时间小于1秒的快速启动。该项目结合我在表面不稳定性(力学)和材料科学方面已有的理解和经验，利用上述见解生产出一种坚固耐用的电力压控开关，用于调节微通道中的液体流动。实际上，该项目将集中于了解基于水凝胶的微系统，它将能够定量确定下列各项：i)在什么条件下发生屈曲以及屈曲的开始如何取决于软表面的材料属性、环境参数(电离值、温度、pH值)和电极几何形状；ii)屈曲形态如何与软表面的材料属性、致动前的初始膨胀状态和电极几何形状有关；iii)如何修剪凝胶层的弯曲形状以有效控制微环境中的流体流动。利用这些实验的认识，将开发一种基于凝胶的响应型开关来动态调节微通道中的液体流量。该项目的工作是跨学科的，包括力学、材料科学和微工程。从光刻制作的结构电极到凝胶化学，将使用一系列材料创新。本项目中描述的“按需”驱动的被动阀技术位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)。该项目将提供所需的理解，以便未来开发具有高度集成性和液体流动自动化的新型微流控设备。

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.