CAREER: Interfacial Engineering and Additive Printing of Flexible Thermoelectric Materials

该学院早期职业发展(CALEAR)补助金支持通过使用添加剂印刷方法的界面工程独立控制热电复合薄膜的电学和热学性能的研究。这项研究旨在使灵活的热电设备能够收集低品位的余热，并产生可用于为传感器电容器和电池充电的电压输出。这些自给自足的电源可以消除对健康监测设备定期充电的需要，并实现对健康参数的不间断监测。这些电源还可以加快可穿戴设备、建筑、结构和国防中使用的连续监控传感器的采用。用于制造柔性热电器件的现有添加剂制造方法包括长持续时间和高温固化循环，使其能量密集型。最新的复合热电薄膜是热电器件的组成部分，由于绝缘粘结剂的存在，活性粒子之间的界面连接不良，以及电子和声子传输特性的相互依赖，导致热电薄膜的性能低下。科学地理解通过使用低能量输入处理方法改变复合微纳米结构和界面来去耦合电子和声子输运特性对于改善热电性能是必要的。高效热电设备的可获得性影响到清洁能源的国家优先事项。综合的研究、教育和推广部分包括通过引入柔性电子学课程来扩展机械工程课程，创建一个新的项目来为不同的学生群体提供有偿的研究机会，并为K-12学生开发热电发生器套件。这项研究旨在使用低能量输入的模板添加剂印刷方法来分离热电复合薄膜中的电子和声子传输特性，涉及(1)调节热电颗粒(微米和纳米)尺寸的分布，(2)创建纳米尺度的粘结剂界面，以及(3)使用适度固化和单轴压力来修改复合微纳米结构。调整颗粒大小的分布在微米级颗粒和纳米级颗粒和缺陷之间建立了权衡，微米级颗粒为载流子提供了较大的平均自由程，纳米级颗粒和缺陷促进了声子散射。对纳米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机械性能(如柔韧性、附着力和强度)之间的相互作用。外部单轴压力的调节有助于从根本上理解外加压力是如何引发缺陷并影响热电性能的。这项研究还展示了一种概念验证可伸缩柔性热电发电机(TEG)设备，采用加法打印方法和卷到卷处理。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。

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.