Probing Ion Injection in Organic Electrochemical Transistors

可以传导电子和离子的塑料在许多应用中都很重要，例如将生物神经脉冲转换为数字电子可读信号的生物电子传感器，可以短时间提供高电流的能量存储设备，以及模仿大脑功能的下一代计算机。限制这些领域技术发展的因素之一是对离子如何注入和在这些半导体塑料中运输的了解有限。这个项目通过使用先进的显微镜技术在纳米尺度上分析聚合物（塑料）来解决这个问题。这些方法可以确定聚合物因离子注入而膨胀的位置，并可以使用红外光（也是在纳米尺度上）将这种反应与离子的化学特征联系起来。然后将微观信息与晶体管测量结果进行比较，以获得对聚合物加工和结构如何影响离子运动的基本理解。从这个项目中获得的科学知识可以更好地为上述应用设计和加工/制造聚合物。此外，该项目还建立在首席研究员在教育方面的记录基础上，通过开发新的外展材料，如适合整合到现有外展项目和网络的聚合物电化学工具包。该项目还通过继续与雷尼尔学者组织的成功伙伴关系，为本科生研究提供直接支持，为代表性不足的群体和第一代大学生在科学领域取得成功提供途径。该项目的科学目标是在使用混合有机电化学晶体管作为实验测试平台的同时，获得对pi共轭聚合物作为混合离子/电子导体中控制离子注入的结构/功能关系的基本理解。这些聚合物和混合物通常在几十纳米尺度上表现出特征，因此该项目使用先进的扫描探针显微镜工具来研究纳米尺度上的离子传输过程。共轭聚合物已经成为在生物和数字环境之间的界面上进行信号转导的有前途的电子和光子材料，拟议的项目将通过独特的局部和整体方法的结合，以不同于其他努力的方式探索与这些应用相关的这些材料的基本结构/功能特性。具体来说，该项目将：1)使用一种新的方法，光致力显微镜（PiFM），制作纳米尺度的图，探测局部化学结构和形态如何结合影响局部离子注入；2)应用电化学应变显微镜（ESM）测量均聚物、嵌段共聚物和共混物中由于离子摄取引起的局部膨胀；并且，3)在探索新的混合和复合结构作为克服现有材料性能瓶颈的手段的同时这样做。值得注意的是，该项目使用纳米级红外显微镜探测导电聚合物和离子导体的混合物，以验证高电子迁移率成分和高离子迁移率成分解耦可以改进电化学晶体管的假设。首席研究员在之前的工作中表明，在混合导体中，离子注入和电子迁移率通常是反相关的，这是器件的瓶颈。这些实验产生了一组独特的测量结果，可以对支撑离子注入的结构-功能关系进行多模态分析。该项目提供了重要的见解，了解混合离子-电子导体中的迁移率和体积电容是如何相关的，以及是否有可能通过关注离子如何从地面进入聚合物来合理地改进导电聚合物和聚合物混合物设计。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。

Plastics that can conduct both electrons and ions are important for numerous applications such as bioelectronic sensors that convert biological nerve impulses into signals readable by digital electronics, energy storage devices that can deliver high currents for short times, and next-generation computers that mimic the function of the brain. One of the factors limiting technological developments in these fields is limited understanding of how ions inject into and transport within these semiconducting plastics. This project addresses this question by analyzing polymers (plastics) at the nanometer scale using advanced microscopy techniques. These methods can determine where polymers are swelling from ion injection and can correlate that response with the chemical signature of the ion using infrared light, also at the nanoscale. The microscopic information is then compared to transistor measurements to gain a fundamental understanding of how the polymer processing and structure influences ion motion. The scientific knowledge from this project enables better design and processing/manufacturing of polymers for the applications noted above. The project additionally builds upon the track record of the principal investigator in education by enabling development of new outreach materials such as polymer electrochemistry kits that are suitable for integration into existing outreach programs and networks. The project also provides direct support for undergraduate research through continuation of the successful partnership with the Rainier Scholars organization to provide pathways to assist under-represented groups and first-generation college students succeed in the sciences. The scientific goal of this project is to gain a fundamental understanding of the structure/function relationships controlling ion injection in pi-conjugated polymers operating as mixed ionic/electronic conductors while using blended organic electrochemical transistors as an experimental testbed. These polymers and blends typically exhibit features on the scale of tens of nanometers, and therefore this project uses advanced scanning probe microscopy tools to investigate the ion transport process at the nanoscale. Conjugated polymers have emerged as promising electronic and photonic materials for transducing signals at the interface between the biological and digital environments, and the proposed project will explore fundamental structure/function properties of these materials relevant to these applications in a way that is distinct from other efforts through a combination of unique local and bulk methods. Specifically, the project will: 1) use a new method, photoinduced force microscopy (PiFM), to make nanoscale maps probing how local chemical structure and morphology combine to affect local ion injection; 2) apply electrochemical strain microscopy (ESM) to measure local swelling due to ion uptake in homopolymers, block copolymers, and blends; and, 3) do so while exploring new blend and composite architectures as a means to overcome the bottlenecks of existing materials performance. Notably, this project uses nanoscale infrared microscopy to probe blends of conducting polymers and ionic conductors to test the hypothesis that decoupling the high electronic mobility component and high ionic mobility component can enable improved electrochemical transistors. The principal investigator has shown in previous work that ion injection and electronic mobility are often anti-correlated in mixed conductors, which serves as a device bottleneck. These experiments yield a distinct set of measurements that enable multimodal analysis of the structure-function relationships underpinning ion injection. The project provides important insight into how mobility and volumetric capacitance in mixed ionic-electronic conductors are related, and whether it is possible to rationally improve conducting polymers and polymer blends design by focusing on how ions move into the polymer from the ground up.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.