title: Microfluidic pH-sensing chips integrated with pneumatic fluid-control devices.
abstract: This paper presents a microfluidic chip capable of performing precise continuous pH measurements in an automatic mode. The chip is fabricated using micro-electro-mechanical-systems (MEMS)-based techniques and incorporates polydimethylsiloxane (PDMS) microstructures, pH-sensing electrodes and pneumatic fluid-control devices. Through its enhanced microchannel design and use of pneumatic fluid-control devices, the microfluidic chip reduces the dead volume of the sample and increases the pumping rate. The maximum pumping rate of the developed micro-pump is 28 microL/min at an air pressure of 10 psi and a driving frequency of 10 Hz. The total sample volume consumed in each sensing operation is just 0.515 microL. As a result, the developed chip reduces the sample volume compared to conventional large-scale pH-sensing systems. The microfluidic chip employs the electrochemical sensing method to conduct precise pH level measurements. The sensing electrodes are fabricated by sputtering a layer of SiO(2)-LiO(2)-BaO-TiO(2)-La(2)O(3) (SLBTLO) onto platinum (Pt) electrodes and the pH value of the sample is evaluated by measuring the potential difference between the sensing electrodes and a reference electrode. Additionally, the integration of the microfluidic chip with a pneumatic fluid-control device facilitates automatic sample injection and a continuous sensing operation. The developed system provides a valuable tool with which to examine pH values in a wide range of biomedical and industrial applications.
authors.affiliation: Department of Engineering Science, National Cheng Kung University, Tainan, Taiwan.
authors.forename: Chen-Fu
authors.initials: CF
authors.lastname: Lin
authors.forename: Gwo-Bin
authors.initials: GB
authors.lastname: Lee
authors.forename: Chih-Hao
authors.initials: CH
authors.lastname: Wang
authors.forename: Huei-Huang
authors.initials: HH
authors.lastname: Lee
authors.forename: Wei-Yin
authors.initials: WY
authors.lastname: Liao
authors.forename: Tse-Chuan
authors.initials: TC
authors.lastname: Chou
mesh_terms: D004563:Electrochemistry / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D017022:Flow Injection Analysis / Q000295:instrumentation* / Q000379:methods; D006863:Hydrogen-Ion Concentration; D017736:Ion-Selective Electrodes; D008839:Microelectrodes; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation* / Q000379:methods; D018511:Systems Integration; D014159:Transducers