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、健康监测等领域具有广阔的应用前景。为了模仿人类皮肤对压力的感知，除了其高灵敏度之外，柔性压力传感器必须适用于宽的压力范围。然而，虽然在压力检测中已经采用了覆盖宽压力范围的各种换能机制，但是在当前柔性压力传感器中，在高灵敏度和宽工作压力范围之间存在不协调的折衷。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的柔性铁电传感器，将解决权衡的发展基础研究。该项目的研究结果将为柔性触觉传感器铺平道路，该传感器在广泛的检测范围内具有高灵敏度，多模态检测能力和自供电特性，以及出色的机械稳定性和耐用性。教育目标是为本科生和研究生培养多学科培训环境，并建立下一代劳动力，他们将为迎接新的科学和工程挑战做好充分准备。该项目将促进少数民族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性和高度机械敏感性。然而，基于具有均匀孔隙率的泡沫的压力传感器在超过泡沫中的微骨架屈曲的临界载荷时失去检测灵敏度。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。利用梯度孔隙率，可以通过同时激活铁电泡沫中的其他变形模式来屏蔽有害的屈曲模式，从而实现高灵敏度和宽检测范围。一个综合的方法，涉及多物理场建模，材料合成，和机械，压电和传感性能的综合表征，将被采用来实现这些目标。多物理场建模将确定一组控制机械灵活性、检测灵敏度和操作范围的关键参数，这将指导梯度泡沫传感器的设计和优化。所提出的合成方法涉及的微泡沫的制造与梯度孔隙率，然后由分子铁电晶体接枝到泡沫上。传感器的性能将在不同的加载制度和加载模式的特点和证明。这种深入的理解和表征将导致具有前所未有的精度和性能的梯度铁电微泡沫传感器的加工。该项目所产生的知识也将促进分子铁电体（一种新开发的电活性材料）在传感器和其他电子设备中扩大应用的变革性进展。该奖项反映了NSF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.