CAREER: Interfacial Engineering and Additive Printing of Flexible Thermoelectric Materials

该学院早期职业发展（Career）基金支持通过使用增材打印方法的界面工程来独立控制热电复合薄膜的电学和热性能的研究。这项研究的目的是使柔性热电装置能够收集低品位的废热，并产生电压输出，可用于给传感器电容器和电池充电。这些自给自足的电源可以消除定期为健康监测设备充电的需要，并实现对健康参数的不间断监测。这些电源还可以加速可穿戴设备、建筑物、结构和国防中使用的连续监测传感器的采用。现有的用于制造柔性热电器件的增材制造方法涉及长时间和高温固化周期，使其成为能源密集型。最先进的复合热电薄膜是热电器件的基石，由于绝缘粘合剂的存在，活性粒子之间的界面连接不良，以及电子和声子输运特性的相互依赖，其性能较低。利用低能量输入处理方法修饰复合材料的微纳米结构和界面，从而科学地理解电子和声子输运性质的去耦，对于提高热电性能是必要的。高效热电器件的可用性影响着国家清洁能源的优先级。综合研究、教育和推广部分包括通过引入柔性电子课程来扩展机械工程课程，创建一个新项目为不同的学生群体提供有偿研究机会，并为K-12学生开发热电发电机套件。本研究旨在利用低能量输入的模板增材印刷方法来解耦热电复合薄膜中的电子和声子输运特性，其中包括：(1)调整热电颗粒（微纳米）尺寸的分布，(2)创建纳米级粘合剂界面，以及(3)使用适度固化和单轴压力对复合材料的微纳米结构进行改性。调整粒子尺寸分布建立了微米级粒子和纳米级粒子之间的权衡，微米级粒子为载流子提供了较大的平均自由程，而纳米级粒子和缺陷则有利于声子散射。纳米级粘结剂界面的研究考察了粘结剂用量如何影响活性颗粒之间的电连接、促进热阻以及影响薄膜的柔韧性、附着力和强度等机械性能之间的相互作用。外部单轴压力的调整发展了对施加压力如何引发缺陷和影响热电性能的基本理解。该研究还展示了一种概念验证的可扩展柔性热电发电机（TEG）设备，该设备使用增材打印方法和卷对卷加工。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。

This Faculty Early Career Development (CAREER) grant supports research focused on the independent control of electrical and thermal properties of thermoelectric composite films through interfacial engineering using additive-printing methods. The research aims to enable flexible thermoelectric devices that can harvest low-grade waste heat and generate a voltage output that can be used to charge sensor capacitors and batteries. These self-sufficient power supplies can eliminate the need for periodically charging health-monitoring devices and enable the uninterrupted monitoring of health parameters. These power supplies can also accelerate the adoption of continuous monitoring sensors used in wearable devices, buildings, structures, and defense. Existing additive manufacturing methods used for fabricating flexible thermoelectric devices involve long duration and high temperature curing cycles making them energy intensive. The state-of-the-art composite thermoelectric films, building blocks of thermoelectric devices, suffer from low performance due to the presence of insulating binder, poor interfacial connection between active particles, and interdependence of electron and phonon-transport properties. The scientific understanding of decoupling electron- and phonon-transport properties by modifying composite micro and nanostructures and interfaces using low-energy-input processing methods is necessary for improved thermoelectric performance. The availability of high-efficiency thermoelectric devices impacts the national priority of Clean Energy. The integrated research, education, and outreach components include expanding the mechanical engineering curriculum by introducing a course on flexible electronics, creating a new program to offer paid research opportunities to a diverse group of students, and developing a thermoelectric-generator kit for K-12 students.This research aims to decouple electron- and phonon-transport properties in thermoelectric composite films using low-energy-input stencil additive-printing methods which involve (1) the tuning of the distribution of thermoelectric particle (micro and nano) sizes, (2) creation of nanoscale binder interfaces, and (3) modification of composite micro and nanostructures using moderate curing and uniaxial pressure. Tuning the distribution of particle sizes establishes tradeoffs between micron sized particles, which provide a large mean free path for charge carriers, and nanosized particles and defects, which facilitate phonon scattering. The study of the nanoscale binder interfaces examines the interplay between how the binder amount affects electrical connection among active particles, facilitates thermal resistance, and influences the mechanical properties such as flexibility, adhesion, and strength of the film. The tuning of external uniaxial pressure develops a fundamental understanding of how applied pressure initiates defects and impacts thermoelectric properties. The research also demonstrates a proof-of-concept scalable flexible-thermoelectric generator (TEG) device, using the additive-printing method and roll-to-roll processing.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.