基于孔洞结构压电驻极体的柔性自驱动传感器研究

Having flexibility and easy to manufacture in large scale with low cost, higher piezoelectric coefficient and excellent biocompatibility, piezoelectret polymers have presented an enormous application potential in new flexible electronic devices, which make up the brittleness of piezoelectric ceramics and the low piezoelectric coefficients of traditional piezoelectric polymers. Lots of research has shown that the higher piezoelectric coefficients of this kind of materials come from the air ionization and subsequent opposite space charges acquired on the surface of inner poles. This project aims to produce cellular piezoelectret based on polydimethylsiloxane (PDMS) whose piezoelectric coefficient and mechanical performance could be improved through regulation of the stacking layer numbers and the size of the pores, chemical modification of the inner walls of the pores and selection of proper poling procedure. Furthermore, combined with flexible electrodes, a wearable and flexible self-powered sensor based on piezoelectret can be fabricated which is able to convert the mechanical energy generated in irregular human motions into electric power and be applied in monitoring life signs such as blood pressure, pulse, breath and so on. This investigation will contribute to the development of flexible electronics and intelligent medication so as to show its meaning and values in scientific study.

孔洞结构压电驻极体聚合物具有柔性，可大面积成膜，成本低，压电系数高，与人和生物体兼容良好，弥补了压电陶瓷的脆性和传统压电聚合物压电系数低的不足，在柔性可穿戴电子器件中有很广泛的应用前景。研究表明，此类材料高的压电系数来自于在极化过程中由气体电离而产生的被俘获在孔洞内表面的正负粒子。本项目拟设计基于聚二甲基硅氧烷（PDMS）的孔洞结构压电驻极体，通过对其层数和孔洞大小的控制、孔洞介质壁层的修饰和选取合适的极化手段等方法，提高其压电系数和机械性能，并结合柔性电极，设计出可穿戴的压电驻极体柔性自驱动传感器。该器件可以用于将人体不规则运动产生的机械能转化为电能，实现自驱动柔性传感系统的搭建，继而用于监测人体血压、脉搏、呼吸等生命体征。该项研究成果将对柔性电子学和智能医疗等领域的发展有很好的推动作用，具有重要的科学意义和应用价值。

柔性可穿戴压力传感器具备柔性、质量轻、灵敏度高等优势，在人工智能医疗电子领域引起了科研界和工业界的广泛重视。驻极体和孔洞结构压电驻极体薄膜具备天然的柔性，易于大面积成膜，由其制备的压力传感器可收集日常生活环境及人体本身大量随机振动的机械能，实现压力传感器的自供能，缓解能源供应及电池处理带来的负面影响，从而迅速成为近年来的研究热点。本项目建立驻极体和压电驻极体的理论模型，研究孔洞层数、孔洞尺寸和孔洞内部极化表面电荷密度对压电系数的构效关系；设计出高表面电荷密度驻极体和孔洞结构压电驻极体，通过对孔洞介质壁进行氟化和采用薄膜复合的方式，提高压电驻极体薄膜的压电系数，进而开发出高性能自供能压力传感器，实现对人体生理活动信号的检测。取得主要结果如下：.（1）研究致密型氟化乙丙烯（FEP）和纤维型多孔聚四氟乙烯（f-PTFE）复合膜的理论模型，证实了采用复合纤维型薄膜的方式可提高驻极体薄膜表面电荷密度；.（2）建立孔洞结构的压电驻极体聚合物薄膜的理论模型，研究材料杨氏模量等力学参数和孔洞厚度、层数等几何尺寸与压电活性关系。压电驻极体薄膜的压电系数d33不仅由内部孔洞尺寸和材料介电常数决定，还与孔洞内部介质壁俘获的电荷密度成正比，与材料的杨氏模量Y33成反比；.（3）制备出基于PDMS和f-PTFE/FEP的规则孔洞结构压电驻极体，得到尺寸规则可控、储存电荷寿命长、压电活性高的柔性压电驻极体薄膜，并研究压力传感器的重要参数如灵敏度、探测极限、响应时间和器件稳定性；.（4）采用三步热压法制备了孔洞结构压电驻极体柔性自驱动压力传感器，可用于对人体肢体运动和脉搏的实时监测。将该压力传感器贴合于人体皮肤，实现了对诸如手腕弯曲、面部肌肉拉伸等人体生理活动信号的检测，并可对腕部桡动脉脉搏信号进行实时监测，显示出该压电驻极体压力传感器在自供能柔性可穿戴智能医疗电子系统的广阔应用前景。