Collaborative Research: Scalable Manufacturing Enabled by Highly Tunable Multiphase Liquid Metal Pastes with Solid and Fluid Capsule Additives

液态金属，如镓及其合金，在电子设备、催化、能量收集和生物医学用途等方面具有各种潜在的应用，但面临制造、可调性和成本方面的挑战，限制了它们的广泛应用。该研究项目旨在研究如何将小型固体和/或流体填料纳入液态金属，即液态金属糊状物，以扩大其物理和化学性质的范围，并增加其对增材制造和其他技术的经济吸引力。为了克服与液态金属的高内聚能密度相关的挑战，该团队建议使用自然形成的纳米薄氧化镓壳作为润湿剂（或表面活性剂）来封装不同相的外来物质。由此产生的液态金属糊状物代表了一类具有未开发特性的新型材料，可以推进可穿戴电子产品、软机器人和电子产品的热管理。拟议研究的视觉和实践性质将使多平台社区外展成为可能，包括让K-12旅游团体参与使用视频游戏控制器操作3d打印机制作液态金属部件的实践活动。本研究旨在实现一种将气体、液体和固体包裹在液态金属中的通用方法，并了解包裹的天然氧化物在这一过程中的作用，从而创造出一种独特的“表面活性剂”，在原位形成。这些多相材料将在受控条件下通过混合（或鼓泡流体）形成，随后进行彻底表征，以建立工艺-结构-性能关系。这项研究将阐明这种氧化物“表面活性剂”的作用机制，使其分别产生泡沫和含有气泡的糊状物，以及液体或固体物体。氧化物的“包裹”能力将使一种具有高度可调密度、流变性、导电性和导热性的新型导电多相浆料成为可能。有了新的基本见解，该项目还将致力于创造基于液体金属的材料，这种材料可以有效地三维打印到几乎任何成分和形状的基材上，用于两项具体研究。第一个目标是制造一种泡沫，这种泡沫的成本效益是纯液态金属的10倍，重量也比纯液态金属轻，而且适合于可拉伸的电子设备。第二项研究是创造一种膏体，在使用时分泌少量的二次液体，从而改善下一代热界面材料的热机械接触。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Liquid metals such as gallium and its alloys have a variety of prospective applications such as in electronic devices, catalysis, energy harvesting and biomedical use but face challenges with manufacturing, tunability and cost that limit them from widespread use. This research project seeks to investigate how incorporating small-scale solid and/or fluid fillers into the liquid metal, i.e. liquid-metal pastes, have the potential to extend the range of physical and chemical properties and increase their economic appeal for additive manufacturing and other technologies. To overcome the challenges associated with the high cohesive energy density of liquid metals, the team proposes to use naturally formed nanometer-thin gallium-oxide shells as a wetting agent (or surfactant) for encapsulating foreign materials of different phases. The resultant liquid-metal pastes represent a novel class of materials with unexplored properties that can advance wearable electronics, soft robotics, and thermal management of electronics. The visual and hands-on nature of the proposed research will enable multiplatform community outreach including engaging K-12 tour groups with a hands-on activity using a video-game controller to operate a three-dimensional printer in making liquid-metal parts.This research aims to realize a generalized way to encase gases, liquids, and solids inside liquid metals and to understand the role of the encasing native oxide in doing so, which creates a unique “surfactant” that forms in situ. These multiphase materials will be formed by mixing (or bubbling fluids) under controlled conditions and subsequently characterized thoroughly to establish process-structure-property relationships. The investigation will elucidate the mechanism by which this oxide “surfactant” works to create foams and pastes with trapped air pockets and liquids or solid objects, respectively. The oxide “enveloping” ability will enable a new class of conductive multiphase pastes with highly tunable density, rheology, as well as electrical and thermal conductivities. With the new fundamental insight, this project will also aim to create liquid-metal based materials that can be effectively three-dimensionally printed onto substrates with almost any composition and shape for two specific studies. The first one is to achieve a foam that is up to 10 times more cost-effective and lighter than pure liquid metals and yet fits for stretchable electronic devices. The second study is to create a paste that secretes small amounts of secondary liquid when applied and thereby improves thermo-mechanical contacts of next-generation thermal interface materials.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.