單分子自組裝層對溫度效應影響以壓阻式微懸臂梁偵測之研究

Abstract

以目前全球生物晶片產業市場的分析來看，蛋白質晶片的市場有逐漸成長的趨勢，為此本研究選用以力學為基礎的壓阻式微懸臂樑生物感測器(Piezoresistive micro-cantilever biosensor)做為檢測機制，相較於其他傳統生物感測器具有需要架設複雜光場、且必須在待測分子上標定螢光等缺點，以壓阻式微懸臂梁為基礎的生物感測器，具有高靈敏度、可即時監測、操作方便，更可利用微機電製程技術製作，達到低成本及微小化的目的。 然而將壓阻式微懸臂梁生物感測器應用到生物檢測上，長期以來，有著由於微懸臂梁本身的自熱效應(self heating effect)及雙模效應(bimorph effect)所造成的訊號漂移是否在生物檢測上會造成訊號誤判的疑問，且目前研究用來解決溫度影響的惠斯同電橋電路，在消除溫度造成的訊號漂移有其極限；本研究完成可同時監測反應區內溫度的壓阻式微懸臂梁生物感測器，可修正反應區內溫度改變造成的訊號漂移；另一方面，由實驗發現，壓阻式微懸臂梁感測器，受到溫度改變造成的訊號漂移，會隨著微懸臂梁表面形成自我組裝層而降低；針對此現象本研究利用三個不同的生物感測晶片進行實驗；表面形成自我組裝層前受到溫度影響改變的訊號：分別是0.0282 volts/℃、0.0214 volts/℃、0.0223 volts/℃，形成自我組裝層後訊號降低至：0.0183 volts/℃、0.0173 volts/℃、0.0187 volts/℃，三組實驗結果都有下降的趨勢，下降的百分比分別為：35.29 %、 18.89 %、16.11 %。此現象有助於未來將此壓阻式微懸臂梁生物感測器應用到生物檢測上。

This work demonstrates the thermal effect of self assembled monolayer detected by piezoresistive micro-cantilever beam. The chemical monolayer of linker (HS-(CH2)7-COOH) was transported by microfluidics and self assembled onto the gold surface of the microcantilever beam. With the change of temperature applied by the external thermal source, the device signal was obtained by a single free-standing microcantilever beam of the sensor, which represented one varied resistance in the electrical resistance configuration of the Wheastone Bridge circuit. The experiment was carried out in successive thermal cycles of with and with no self-assembled monolayer. s described early, one single free-standing micorcantilever beam of the sensor was employed in this work instead of reported two free-standing beams for noise compensation due to flow-field, thermal, and chemical disturbance. In addition, the temperature sensor was made and embedded in the micro channel for measurement of temperature variation in thermal cycles. With no SAM coating, the averaged electrical signal with respect to temperature change was 0.0282 volts/℃、0.0214 volts/℃、0.0223 volts/℃ for three devices, respectively. In case of SAM coating onto the beam, the device signal apparently decreased to 0.0183 volts/℃、0.0173 volts/℃、0.0187 volts/℃, with respective to former three devices. It was found that the significant drops of three devices were 35.29 %、18.89 %、16.11 %. he monolayer of (HS-(CH2)7-COOH) is of less than 1 nm in thickness, self-assembled onto the microcantilever of approximate 1300 nm in thickness. This work has proven that the thermal property of such an extremely thin monolayer shows significant effect to the microcantilever beam.