Switchable, bistable microactuator systems based on stimuli-responsive polymers

刺激响应性水凝胶是用于在微流体装置内产生微致动器系统的引人注目的材料，这是由于它们的3D可印刷性、可调特征以及与细胞无害地相互作用的能力。然而，目前基于水凝胶的微致动器往往非常简单，而复杂的功能，例如双稳态，在很大程度上仍未开发;因此，该领域仍然不成熟，许多潜在的应用尚未实现。为了建立在第一个资助期的工作基础上，我们已经彻底表征和改进了PNIPAM基温敏微致动器的致动，我们在此提出了一种新的策略，以实现基于温敏/pH响应水凝胶和形状记忆聚合物的组合的微致动器系统。这些材料将使用双光子直接激光写入成形为微致动器系统，这允许制造高度复杂的3D几何形状，并且它们在响应刺激中的致动将被深入表征和优化。我们将探讨使用热响应水凝胶构建微致动器阵列/系统的优点和缺点，通过分析个别微致动器之间发生的串扰。我们假设，形状记忆材料与热响应和/或pH响应材料的组合可以用于甚至利用各个微致动器之间的串扰，以增加整个微致动器系统的功能。该项目的最终演示将包括一个不同形状和配置的微致动器系统，包括用于动态微流体系统的主动微通道壁和刺激响应微阀。虽然市售的最先进的微流体设备遭受其属性在制造过程中预定义，我们的微致动器系统将改为基于主动功能，这将增加动态的灵活性到微流体设备通过合作的各个微致动器。类似的原理将用于设计自主操作的细胞和类器官培养系统，其中pH响应微阀将调节细胞培养基流动。该项目的成功将使微流体系统具有前所未有的适应性和自主性，从而提高各种工具和程序的可访问性和吞吐量。

Stimuli-responsive hydrogels are compelling materials for generating microactuator systems within microfluidic devices due to their 3D printability, tunable features, and ability to interact harmlessly with cells. Current hydrogel-based microactuators, however, tend to be very simple, and complex features, e.g. bistability, remain largely unexploited; therefore, the field remains immature and many potential applications have not yet been realized. To build on work from the first funding period, where we have thoroughly characterized and improved the actuation of PNIPAM-based thermoresponsive microactuators, we herein propose a novel strategy to achieve bistable microactuator systems based on combinations of thermoresponsive/pH responsive hydrogels and shape-memory polymers. The materials will be shaped into microactuator systems using two-photon direct laser writing, which allows for the fabrication of highly complex 3D geometries, and their actuation in response stimuli will be characterized in-depth and optimized. We will explore the advantages and disadvantages of using thermally responsive hydrogels to construct microactuator arrays/systems by analyzing the cross-talk that occurs between individual microactuators. We hypothesize that the combination of a shape-memory material with a thermoresponsive and/or pH-responsive material can be used to take even advantage of cross-talk between individual microactuators to increase the functionality of the whole microactuator system. The final demonstration of this proposed project will consist of a system of microactuators in different shapes and configurations, including active microchannel walls and stimuli responsive microvalves for applications in dynamic microfluidic systems. While commercially available state-of-the-art microfluidic devices suffer from having their properties pre-defined during fabrication, our microactuator system will instead be based on active features that will add dynamic flexibility into microfluidic devices through the cooperation of individual microactuators. Similar principles will be used to design autonomously operating cell and organoid culturing systems, where pH-responsive microvalves will regulate cell medium flow. The success of this project will result in unprecedented adaptability and autonomy in microfluidic systems, leading to improved accessibility and throughput of a wide variety of tools and procedures.