柔軟且可伸展的導電結構是穿戴式感測器不可或缺的關鍵元素，通常是透過
在彈性聚合物基材上嵌入導電材料而成。本研究開發快速的複合導電結構成型技術，使用彈性高分子聚二甲基矽氧烷做為應變感測器的基材，並在表面沉積具備良好機械特性的導電高分子聚吡咯，以及優異導電特性的銀奈米顆粒，組成兼具機械感測與電流傳導功能的複合結構。本研究使用光致聚合的方式在彈性基材上定義出聚吡咯導線的圖形，為提高導電度，進一步嵌入密緻的銀奈米顆粒，並覆蓋化學聚合產生的聚吡咯。整個複合結構的製作可分四步驟在8分鐘之內完成，圖形定義精度可達0.01英吋，電導率可達34.95 S/cm，1 cm長1 mm寬的導線電阻約為800 Ω。
本研究所製作的複合導電結構其電阻隨應變增加而上升，具有電阻式應變感測的功能。為提升其伸展性，還透過預先拉伸基材的方式，將表面拉伸至200%應變的狀態再沉積導電結構，之後卸除外力使其回復原狀。因為複合結構與彈性基材的尺寸和機械特性差異極大，會使回復後的導線產生微觀的波浪狀皺摺結構。這些皺摺結構可有效提升導線的伸展性，在200%應變範圍內電阻幾乎保持定值。為了展示本研究複合導電結構的實用價值，我們使用DLP光固化三維列印系統，列印能依照指圍大小調整的手指穿戴結構，並整合前述的彈性基材與複合導線，形成一可感測手指姿態的電阻式應變感測器。此一技術未來可望應用於人體關節，以及軟性機械運動的感測，產生回饋訊號以完備系統的控制與整合。

Soft and stretchable conductive materials are highly desired for the implementation of wearable electronic devices. Electronics can be made on elastically stretchable substrates, which conform to irregularly curved surfaces of human skin. For example, skin-mountable and wearable sensors are needed for applications including body motion detection, personalized health-monitoring, and the feedback control of soft robotics. Conducting polymers, whose chemical and physical properties can be tailored to the specific needs of many applications, are commonly used in stretchable electronics. However, the manufacturing of stretchable conducting polymer structures is usually costly and time-consuming, and the stretchability of resulting structures is normally limited. The goal of this thesis is to develop a rapid prototyping scheme of soft conductive composites for wearable sensors. We have developed various patterning processes that simultaneously deposit electronically conducting poly-pyrrole structures and incorporate nanophase silver grains within. Meanwhile, the spatial distribution of silver grains can be locally adjusted to improve the conductivity of composite structures.
A four-step rapid manufacturing scheme based on (1) photo-polymerization of silver-containing polypyrrole films, (2) photo-deposition of additional silver particles on surface, (3) further growth of silver particles on surface, and (4) lift-off deposition of silver-containing polypyrrole films, has been implemented successfully. Pyrrole molecules can be oxidized with either cationic photo-initiators or silver ions, and polymerized into desired polypyrrole patterns on elastomeric polydimethylsiloxane (PDMS) substrates. If the elastic PDMS substrates are pre-stretched, it results in the wrinkling of relative rigid silver-containing polypyrrole films on surface. The buckled, wavy polypyrrole films are promising candidates for interconnects in stretchable electronics. It is demonstrated that the polypyrrole films remains electrically conductive up to >250% strain and maintains electrical continuity under repeated mechanical deformation. Overall, the proto-typing of conductive composites with line width down to 0.01 inches can be completed in 8 minutes. The conductivity of resulting silver-containing polypyrrole structures is measured to be higher than 35 S/cm. In the prototype demonstration, DLP (digital light processing) stereolithography is employed to selectively deposit conductive composite structures on demand, and to build wearable monitors to measure finger postures.

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