利用噴墨技術製作可同時量測之微型層疊溫濕度感測迴路

Abstract

本研究利用噴墨技術製備同時同點量測之溫濕度感測器，並研究其性質與描述方法。為使材料特性能夠獲得充分了解，首先以奈米粒子墨水噴製銀線、氧化鎳、聚苯胺作為本實驗之電極、溫敏電阻、濕敏電容薄膜，並製作單一感測器。藉由對單一感測元件之特性描述、參數控制，在175℃的後處理後及封裝後，可得良好特性之溫度感測器薄膜，其遵守阿瑞尼士方程式，且有高於市售標準之使用靈敏度，且反應時間極短，以手指觸碰僅3秒即可產生電阻變化；濕度感測器因吸附水氣而產生之電容改變，其吸附現象可以Frendlich等溫吸附線描述，且為一有利吸附 本文亦探討單一感測器製程中之影響因素，如感測器厚度如何影響感測器表現：氧化鎳溫度感測器電子傳導機制為表面電流，因此厚度無法增加其導電度，反而與其表面樣態有關；而聚苯胺厚度則是影響電容大小的因素，但過厚的聚苯胺會造成高濕度時數值失準。而不同面積之氧化鎳薄膜並不影響其表現，卻會些許影響其反應時間；不同面積的聚苯胺薄膜，其電容大小與面積成正相關。 為降低初始電阻使其可運用於室溫或是更低之溫度，本文在製備溫溼度感測器前，亦研究如何利用改變立體結構與混摻材料之方法降低溫度感測器之電阻值，我們利用電極-溫度感測器-電極之立體結構，可有效降低其初始電阻，但其為一較不穩定的結構；若使用銀粒子參雜，則可使初始電阻降低1個數量及至約10MΩ，靈敏度仍保持在3000K。接著我們利用不同裝置迴路達到並聯之感測器組的效果，並利用變數分析、數量級分析與逐步探討等技巧，配合材料本身參數對電阻電容變化之的特性，由雙迴路感測器系統逐步探討至同時同點量測之溫濕度感測組。其模式並無太大改變，並皆可以公式描述。由上述可知，本研究可以簡單不需遮罩、低成本之噴墨製程，製備一低溫可利用之同點同時量測溫溼度感測器組，其對於溫濕度同時量測有一定的信賴度。並利用噴墨參數之調整，使感測器之靈敏度與遲滯時間得到較好之改善。

In this research, material used in thermistor and capacitive humidity sensor will be investigated. First we choose silver nanoparticle to fabricate the electrode, nickel oxide for thermistor, polyaniline for capacitive humidity sensor. After 175℃ post-treatment and package, we investigate the single sensor and optimize them by adjust the inkjet parameters. The well-adjusting thermistor will obey Arrhenius equation and has a sensitivity higher than commercial uses. The capacitive humidity sensor will obey Frendlich isotherm. For commercialized temperature and humidity control system there two sensors with independent circuit to monitor temperature and humidity respectively, however in some extreme condition such as freezer or reflow oven these two sensors may interrupt to each other that results in decreased sensitivity. Therefore, in order to overcome this challenge, this research is aimed at integrating sensing material into one parallel circuit on flexible substrates via a low cost direct writing technology. A layer-by-layer strategy is used to integrate the temperature-sensitive NiO layer and humidity-sensitive polyaniline (PANI) layer together as a highly responsive device. The sensing elements, which have an adjustable dimension with a submillimeter scale, can operate over a wide range from temperature lower than 20°C to 100 °C and 20% RH to 90% RH with a great sensitivity. After adjust of inkjet parameters and adding silver nanoparticle into nickel oxide ink for the purpose of optimization for this sensor circuit, this circuit will be analyzed carefully to read temperature and humidity measurements at once. From the water adsorption on PANI thin film and temperature variation in NiO layer, the resistance and capacitance readings of the device in AC mode can be directly correlated to the environmental conditions. A correlation formula combining Arrhenius equation and Frendlich isotherm will be developed to accurately describe the sensor responses.