A micro PDMS flow sensor based on time-of-flight measurement for conductive liquid

• Published in: Microsystem technologies : sensors, actuators, systems integration Vol. 19; no. 7; pp. 989 - 994
• Main Authors: Yu, Haixia, Li, Dachao, Roberts, Robert C., Xu, Kexin, Tien, Norman C.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.07.2013; Springer
• Subjects: Applied sciences; Electronics; Electronics and Microelectronics; Engineering; Exact sciences and technology; General equipment and techniques; Instrumentation; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Mechanical Engineering; Mechanical instruments, equipment and techniques; Microelectronic fabrication (materials and surfaces technology); Micromechanical devices and systems; Nanotechnology; Physics; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing; Technical Paper; Microfluidic Channel; Electrode Pair; Syringe Pump; Flow Sensor; PDMS; Dimethylsiloxane polymer; Time dependence; Measurement sensor; Interstitials; Syringe; Time-of-flight method; Glucose; Permeability; Microsensors; Monitoring; Vacuum pumps
• ISSN: 0946-7076; 1432-1858
• DOI: 10.1007/s00542-012-1686-7

Transdermal extraction of interstitial fluid (ISF) offers an attractive method for non-invasive blood glucose monitoring. In order to calculate blood glucose concentration accurately, precise volume measurement of transdermally extracted ISF is required due to human skin’s varying permeability. In this paper, we presented a novel flow sensor fabricated from polydimethylsiloxane (PDMS), designed to measure the volume of conductive liquid. The flow sensor consists of two pairs of metal electrodes, which are fabricated in the PDMS channel. The volume of liquid is measured utilizing the time-of-flight of the two electrode pairs’ resistance while the liquid is flowing through the flow sensor. 1–14 μL normal saline solution was measured, the flow sensor measured volumes correlate very well ( R 2  = 0.9996 and R 2  = 0.9975 for vacuum pump and syringe pump situations respectively) with the actual volumes. And the coefficient of variation for 10 times 10 μL normal saline solution measurement is 0.0077 (vacuum pump) and 0.0381 (syringe pump), respectively. The demonstrated flow sensor provides excellent functionality for conductive liquid.