可攜式泡綿壓阻材料感測器於人體動作辨識之應用

Abstract

以聚合物海綿為基材的壓阻式人體活動感測器因機械性質佳、具高度延展性、柔韌性與輕薄可攜等特點，近年來吸引了許多研究團隊的投入。隨著這類材料的快速發展，壓阻式海綿壓力感測器由於製程複雜、高製造成本、受限的靈敏度和壓力範圍，以及繁瑣的訊號輸出入設備之問題也隨之浮現。在此項研究中，我們使用發泡美耐皿為基材，以聚二氧乙基噻吩／聚苯乙烯磺酸(PEDOT:PSS)懸浮液浸泡後抽乾製成壓阻式海綿，利用微米銅線改變壓阻海綿與電極間的接觸面積以及接觸行為，將感測器的偵測靈敏度以及偵測壓力範圍產生放大的效果。以相同製程條件的壓阻海綿經過我們的優化後，在應變因數(Gauge factor)上有高達65倍的提升。我們同時將此方式應用於其他種類的壓阻海綿發現使用高密度聚氨酯(Polyurethane)發泡海綿代替美耐皿所製成的壓阻海綿在GF值上可得到147倍的提升，而利用單壁奈米碳管取代PEDOT:PSS所製成的美耐皿壓阻海綿上也可以得到3倍的GF值提升。 我們所發現的接觸點改良方式不僅可將壓阻海綿的靈敏度提升一個級距以上，所得的感測器壓力區別能力也獲得放大，能在施加較大外力時也提供良好的解析度。我們進一步延伸此設計，藉由使用鈕扣電池取代龐大的電源供應器，並結合發光二極體以取代電源量測儀，設計出一種全攜帶式、低成本、高靈敏度，並可裸視辨別的人體動作檢測器，可以對人體之各類動作進行偵測，並藉由對電壓電流變化具高靈敏度之發光二極體亮度變化以呈現相對應的受力規模與位向。我們相信，這項研究在海綿類壓阻式感測器上的嶄新突破，對於未來可攜式感測裝置的電性改良亦或應用方面都能提供更多且更廣的正面影響。

Human motion devices made by piezoresistive sponges have attracted attention from many research groups over the past few years. Polymer sponges used as substrates or templates possess merits such as better mechanical properties include being flexible, stretchable, compressible, and light-weight. However, several main bottlenecks occur even after vigorous developments, e.g. lack of combination between substrate materials and conductive materials, complicated fabrication processes that lead to higher cost, and contradiction between sensitivity and detection range. Herein, we change the way of connecting the sponge and the copper electrode, using micro copper wires to create the micro-cylinder structure on the electrode to replace the conventional silver paste. Cylinder structures create gaps at the interface between two surfaces and increase the initial system resistance, raising device sensitivity and applicable pressure ranges. Comparing two melamine/PEDOT:PSS sponges with the same fabrication process, but one connected with silver paste and the other with our cylinder electrode, the system with cylinder electrode shows a 65-fold increment on gauge factor at 10% strain. This phenomenon is also present on other devices fabricated with two other piezoresistive sponge types: polyurethane/PEDOT:PSS and melamine/CNTs. Based on this observation, we design a portable human motion detection device. Innovations include the bottom cell substitute for power supply and signal recording system replacement by LED. Signals induced by different amount of pressure can be distinguished by naked eyes due to the high sensitivity of our cylinder structured piezoresistive sponge with the property of low power consumption. Our study provides a novel, simple, low-cost and visual strategy to tackle the issues of piezoresistive material sensitivity, pressure detection range, and portable capability.