Processing and Properties of Functional Liquid Metal Elastomer Composites

弹性体(软聚合物)，如有机硅，是必须模仿自然人体组织的机械性能的工程系统的理想选择。通过匹配身体的自然属性，这些柔软和轻便的材料可以符合皮肤，而不会造成不适或伤害。应用包括可穿戴计算和电子产品、协作机器人、医疗植入物，以及其他需要与服装、皮肤和内部器官机械兼容的新兴技术。然而，这些应用也需要一系列传统弹性体不可能具备的电学性能。虽然有几种有希望的技术来改善弹性体的电性能，但这些技术通常涉及填料、添加剂或共聚物，它们会使材料变得太硬，从而显著降低机械性能。在这个项目中，我们将研究另一种方法，即在硅胶中填充液态金属(LM)的微小液滴的悬浮液。因为它们是金属的，所以液滴可以用来显著改变复合材料的电学性能。此外，由于它们是液体，它们不会导致硅胶变硬。LM嵌入弹性体(LMEE)复合材料代表了一种令人兴奋的新材料类别，将对可穿戴计算和软协作机器人产生潜在的变革性影响，从而促进国内经济增长和生活质量。该项目涉及多个学科，包括制造、化学、材料科学和力学，这些学科将被纳入研究任务和针对匹兹堡地区学业落后学生的技术集成时尚推广计划。LMEE工程的进展依赖于新的加工技术和基于力学的框架，用于预测材料组成、纳米/微米级结构和液-固相互作用对块体电气和机械性能的影响。研究工作将通过结合理论力学建模、材料加工和多尺度表征的跨学科努力来解决这些目标。这将包括努力生产不同成分和工艺条件的LMEE复合材料，比较它们在不同测试配置下的体积性能，并将这些测量结果与基于均化分析和统计力学的预测进行比较。这项工作将带来新的科学见解，有助于从根本上理解复合材料在极端机械载荷下的独特行为。总而言之，这些任务将产生一个新的实验和理论框架，可以用于设计其他类别的多相软物质系统。

Elastomers (soft polymers) such as silicone are ideal for engineered systems that must mimic the mechanical properties of natural human tissue. By matching the natural properties of the body, these soft and lightweight materials can conform to skin without causing discomfort or injury. Applications include wearable computing and electronics, collaborative robots, medical implants, and other emerging technologies that require mechanical compatibility with clothing, skin, and internal organs. However, these applications also require a range of electrical properties that are not possible with conventional elastomers. While there are several promising techniques to improve the electrical properties of elastomers, these typically involve fillers, additives, or co-polymers that significantly degrade mechanical performance by making the material too stiff. In this project, we will research an alternative approach in which silicone is filled with a suspension of microscopic droplets of liquid metal (LM). Because they are metallic, the droplets can be used to dramatically alter the electrical properties of the composite. Moreover, since they are liquid, they do not cause the silicone to become stiff. LM-embedded elastomer (LMEE) composites represent an exciting new class of materials that will have a potentially transformative impact on wearable computing and soft collaborative robotics, thereby promoting domestic economic growth and quality of life. This project involves several disciplines including manufacturing, chemistry, materials science, and mechanics that will incorporated into both the research tasks and an outreach program on technology-integrated fashion for academically underserved students in the Pittsburgh area.Progress in LMEE engineering depends on new processing techniques and a mechanics-based framework for predicting the influence of materials composition, nano-/micro-scale structure, and liquid-solid interactions on bulk electrical and mechanical properties. The research work will address these aims with an interdisciplinary effort that combines theoretical mechanics modeling, materials processing, and multiscale characterization. This will include efforts to produce LMEE composites with various compositions and process conditions, compare their bulk properties under different testing configurations, and compare these measurements with predictions based on homogenization analysis and statistical mechanics. This work will lead to new scientific insights that will contribute to a fundamental understanding of the unique behavior of the composite under extreme mechanical loading. Together, these tasks will result in a new experimental and theoretical framework that could be applied to enable design other classes of multi-phase soft-matter systems.