Multiple Electrochemical Systems Using Microfluidic Technology for Detecting Morphine, Nicotine and Bio-indicators

• Main Authors: Chen-Hsun Weng, 翁振勛
• Other Authors: Gwo-Bin Lee
• Format: Others
• Language: en_US
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/94351966923207938562

碩士 === 國立成功大學 === 工程科學系碩博士班 === 94 === This study reports a microfluidic system for detecting morphine (MO), nicotine (NIC) and bio-indicators (a pH indicator, potassium, calcium and ammonium ions) using a combination of a molecularly imprinted polymer (MIP), ion selective membranes and electrochemical sensing techniques. First, a monomer called 3, 4-Ethylenedioxythiophene (EDOT), was used to mix with morphine molecules through an electropolymerization process on a sensing electrode. The modified MIP-PEDOTmo (poly-ethylenedioxythiophene for morphine) electrode was then used for detecting the morphine via the amperometric method. The morphine samples were automatically transported to the MIP-PEDOTmo sensing electrode using a peristaltic micropump. Experimental data show that the sensitivity of the MIP-morphine sensor is 1.649 mA/cm2-mM in detecting morphine concentration ranging from 0.01 to 0.2 mM at a flow rate of 92 μl/min. Second, the developed sensing system can sense the concentration of NIC by fabricating NIC-imprinted TiO2 sites on a microelectrode in an automatic format. The modular design of the sensing systems allows us to integrate a microfluidic control module and an electrochemical sensing module for a sensitive and selective detection of NIC. A steady-state oxidation current response of NIC at 0.86 V at each concentration level varying from 0 to 5 mM was shown. A linear detection ranging from 0 to 5 mM, with a sensitivity of 41.89 μA/mM•cm2 and a detection limit of 1.8 μM, respectively, was obtained. To investigate the selectivity of the developed method, cotinine (COT) and glucose (Glu) were chosen as the interferents. The corresponding current responses of NIC and its interferents were shown. Experimental data show that the developed system can successfully detect NIC concentration with a high sensitivity and selectivity. Third, a microfluidic device with an all-solid-state potentiometric sensor array was developed by using microfabrication technology. The sensor array included a pH indicator, potassium (K+), calcium (Ca2+) and ammonium (NH4+) ion-selective microelectrodes. The pH indicator was an iridium oxide modified platinum microelectrode fabricated by using thin-film technology. The iridium oxide was deposited by using the electrochemical method. The ion-selective microelectrodes for other three bio-indicators were platinum coated with silicon rubber based ion-selective membranes mixed with potassium (valinomycin), calcium (3,6-dioxaoctanediamide) and ammonium (nonactin) ionophores, respectively. The arrayed microfluidic sensing device showed near Nerstian responses with slopes of 62.04 mV ± 2.5 mV/pH, 53.98 mV ± 3 mV/-log[K+], 25.06 mV± 2mV/-log[Ca2+] and 52.69 mV± 2mV/-log[NH4+] at 25oC ± 5oC, and a linear response within the pH range of 2-10, with potassium, calcium and ammonium concentrations between 0.1 M and 10-6 M. Key components including MIP films, a PDMS (Polydimethylsiloxane)-based microchannel, a peristaltic micropump, microvalves and sensing microelectrodes were integrated by utilizing Micro-electro-mechanical-systems (MEMS) technologies. In this study, the device provided a convenient way to measure the concentration of morphine, nicotine, hydrogen, potassium, calcium and ammonium ions which are important physiology parameters.