Ferroelectric Gradient Microfoams as High-Performance Self-Powered Flexible Pressure Sensors

柔性压力传感器在智能机器人、仿生假肢和健康监测等方面具有很大的应用潜力。为了模拟人类皮肤对压力的感知，除了其高灵敏度外，柔性压力传感器必须适用于广泛的压力范围。然而，尽管在压力检测中采用了覆盖广泛压力范围的各种转导机制，但目前柔性压力传感器在高灵敏度和广泛工作范围的压力之间存在不协调的权衡。这种基本的权衡限制了柔性压力传感器在各种医疗保健和可穿戴电子产品中的实际应用。该项目提出了一种新型柔性铁电传感器的开发基础研究，将解决这一权衡。该项目的研究成果将为柔性触觉传感器铺平道路，该传感器具有高灵敏度，宽检测范围，多模态检测能力，自供电特性，以及卓越的机械稳定性和耐用性。教育目标是为本科生和研究生提供多学科的培训环境，培养能够接受新的科学和工程挑战的下一代劳动力。该项目将促进少数民族参与和参与宾夕法尼亚州立大学的科学和工程研究。铁电微泡沫具有机械柔韧性和高度的机械敏感性。然而，基于均匀孔隙率泡沫材料的压力传感器在超过泡沫材料微骨架屈曲的临界载荷时就失去了检测灵敏度。为了克服这一限制，该研究小组旨在开发高性能梯度微泡沫传感器。在梯度孔隙率下，通过同时激活铁电泡沫中的其他变形模式，可以屏蔽有害的屈曲模式，从而实现高灵敏度和宽探测范围。将采用综合方法，包括多物理场建模，材料合成，以及机械，压电和传感特性的综合表征，以实现目标。多物理场建模将确定一组控制机械灵活性、检测灵敏度和工作范围的关键参数，这将指导梯度泡沫传感器的设计和优化。所提出的合成方法包括制备具有梯度孔隙度的微泡沫，然后将铁电晶体分子接枝到泡沫上。传感器的性能将在不同的加载制度和加载模式下进行表征和演示。这种深入的理解和表征将导致梯度铁电微泡沫传感器的加工具有前所未有的精度和性能。本项目产生的知识还将促进分子铁电体（一种新开发的电活性材料）在传感器和其他电子设备中的广泛应用方面取得变革性进展。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。

Flexible pressure sensors hold great application potential in intelligence robots, biomimetic prosthetics and health monitoring. To mimic human skin’s perception of pressure, it is essential that a flexible pressure sensor must be applicable to a broad pressure range aside of its high sensitivity. However, while various transduction mechanisms covering a broad pressure range have been adopted in pressure detection, an unreconciled tradeoff exists between high sensitivity and a broad working range of pressures in the current flexible pressure sensors. This fundamental tradeoff limits the practical applications of the flexible pressure sensors in various healthcare and wearable electronics. This project proposes fundamental research for the development of a new class of flexible ferroelectric sensors that will resolve the tradeoffs. Findings from this project will pave the way toward flexible tactile sensors with high sensitivity over a broad detection range, multi-modal detection capability, and self-powered characteristic, together with remarkable mechanical stability and durability. The educational goal is to foster the multidisciplinary training environment for undergraduate and graduate students and build next-generation workforce who will be well prepared to undertake new scientific and engineering challenges. This project will promote the minority involvement and participation in science and engineering research at Penn State.Ferroelectric microfoams are mechanically flexible and highly mechanosensitive. However, the pressure sensors based on the foams with uniform porosity lose detection sensitivity beyond the critical load at which the microskeletons in the foam buckle. To overcome this limitation, this research team aims to develop high-performance gradient microfoam sensors. With gradient porosity, the detrimental buckling mode can be shielded by simultaneously activating other deformation modes in the ferroelectric foam, thereby enabling both high sensitivity and broad detection range. An integrated approach, involving multiphysics modeling, materials synthesis, and comprehensive characterization of mechanical, piezoelectric, and sensing properties, will be adopted to fulfill the goals. The multiphysics modeling will identify a set of key parameters that govern mechanical flexibility, detection sensitivity and operation range, which will guide the design and optimization of the gradient foam sensors. The proposed synthesis approach involves the fabrication of the microfoam with gradient porosity followed by grafting of molecular ferroelectric crystals onto the foam. The performance of the sensors will be characterized and demonstrated at different loading regimes and loading modes. This in-depth understanding and characterization will lead to the processing of the gradient ferroelectric microfoam sensors with unprecedented precision and performance. Knowledge generated within this project will also foster transformative progress in broadening applications of molecular ferroelectrics, a newly developed class of electroactive materials, in sensors and other electronic devices.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.