CAREER: Nanoscale Thermal Transport in Hydrogen-Bonded Materials

氢键(H键)是包括DNA、蛋白质、水凝胶和分子自组装在内的许多材料的基本元素。尽管已有一些大型蛋白质系统中能量传输的知识，但对氢键材料之间的纳米级热传输，特别是氢键的作用缺乏系统的了解。这一知识差距阻碍了对生命系统中热传递的了解，也阻碍了具有非凡热性能的新型生物材料的开发，例如合成蜘蛛丝。为了解决这些关键的挑战，这个项目研究了一套氢键材料，包括蛋白质二级结构和有机-无机界面，使用最先进的计算方法结合实验验证。研究成果将加速设计、开发和部署具有可调热性能的新型氢键材料，以满足生物植入、组织再生、癌症治疗和能量储存等广泛领域对生物相容性、多功能材料日益增长的需求。该项目还寻求实现三个与社会相关的成果，包括：(1)通过两个指导计划扩大美国原住民女性学生对工程学的参与；(2)通过3D打印挑战和奖学金计划培养本科生的材料建模技能；这个项目以先进的声子传输理论和振动模式分析的最新进展为基础，系统地揭示了氢键在几种具有代表性的氢键材料积木上的热传输中的作用，这些材料包括纳米晶体(例如蛋白质β-片)、纳米线(例如蛋白质α螺旋和3-10螺旋)和界面。通过使用分子动力学模拟和泛函理论计算，这些研究量化了与几个结构和环境因素有关的氢键构建块中热传导的各向异性，包括氢键连接性(例如，α螺旋与3-10螺旋)、侧链化学和尺寸以及溶剂化。特别强调了解不同的氨基酸序列如何影响热导和输运特性，包括声子态密度、群速度和寿命。在以下方面产生了新的物理见解：(1)不同形式的氢键网络如何有助于纳米尺度的热输运；以及(2)氢键材料中的热输运与其他一维(例如纳米管)、二维(例如石墨烯)和三维不含氢键的材料的热输运有何不同。所取得的知识基础有助于开发具有高导电性积木的新型合成丝以及用于验证理论的新型氢键界面，并与现有材料进行比较和表征。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The hydrogen bond (H-bond) is an essential element of many materials including DNA, proteins, hydrogels and molecular self-assemblies. Despite existing knowledge of energy transport in some large protein systems, a systematic understanding of nanoscale thermal transport across H-bonded materials and, in particular, the role of H-bonds is lacking. The knowledge gap has hindered the understanding of heat transfer in living systems and development of novel biomaterials, e.g. synthetic spider silk, with extraordinary thermal properties. To address these critical challenges, this project investigates a suite of H-bonded materials including protein secondary structures and organic-inorganic interfaces, using state-of-the-art computational approaches combined with experimental validations. The research outcomes will accelerate design, development and deployment of novel H-bonded materials with tunable thermal properties, to meet the increasing needs for biocompatible, multifunctional materials in a wide range of areas including bio-implantation, tissue regeneration, cancer treatment, and energy storage. This project also seeks to achieve three societally relevant outcomes including (1) broadening participation of Female Native American students in engineering through two mentoring programs; (2) fostering skills of materials modeling among undergraduate students using a 3D Printing Challenge and a Fellowship program; and (3) conveying essential concepts of biomaterials and thermal management to high school students and the general public through outreach activities.Building upon recent progress in advanced phonon transport theory and vibrational mode analysis, this project systematically reveals the role of H-bonds in thermal transport across several representative building blocks of H-bonded materials including nanocrystals (e.g. protein beta-sheets), nanowires (e.g. protein alpha-helices and 3-10 helices) and interfaces. By using molecular dynamics simulations and functional theory calculations, the investigations quantifies anisotropy of thermal conduction in the H-bonded building blocks in association with several structural and environmental factors including the H-bond connectivity (e.g. alpha helices vs. 3-10 helices), the side chain chemistry and size, and the solvation. Particular emphasis is given to understanding how different amino acid sequences can affect thermal conductivities and transport characteristics including phonon density of states, group velocities, and lifetimes. New physical insights are generated regarding: (1) how H-bond networks of different forms contribute to nanoscale thermal transport; and (2) how thermal transport in H-bonded materials differs from that in other 1D (e.g. nanotubes), 2D (e.g. graphene) and 3D materials that have no H-bonds. The achieved knowledge base enables development of new synthetic silk with highly conductive building blocks as well as novel H-bonded interfaces that are made, characterized and compared with existing materials for validation of the theory.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.