Study on flow and pressure sensors using electrokinetic energy conversion phenomena in microchannels and nanochannels

Abstract

The present study is devoted to develop novel electrokinetic microsensors for measuring the flow rate and the pressure, which are the most important physical quantities in microfluidics. The present study focuses on two goals. One is to develop electrokinetic flow meter using a glass microchannel, and the other is to develop electrokinetic pressure sensor using glass nanochannels. Firstly, a new concept of a micro flow meter has been developed for measuring the flow rates of buffer solutions. The liquid flow rate through a glass rectangular microchannel was obtained by measuring electrokinetically generated electric signals. A model was presented for which allows for flow rate measurements independent of the cation concentration. Experimental investigations were performed in order to demonstrate the proposed concept. The flow meter was able to measure the flow rate of PBS solutions, which have various concentrations, with error of less than 10%. It was shown that the electrokinetic flow meter has a linear range that is several orders of magnitude wider than conventional thermal flow meters. Secondly, a new concept of a micro pressure sensor has been also suggested. The pressure difference between the inlet and the outlet of glass nanochannels was obtained by measuring electrokinetically generated electric potential. In order to demonstrate the proposed concept, experimental investigations were performed for 100nm-width nanochannels with sodium chloride solutions, which have various cation concentrations. The proposed pressure sensor was able to measure the pressure difference with an error of less than 10% of reading. The sensitivity of the electrokinetic pressure sensor with 10-5M sodium chloride solution was 18.5μV/Pa, which is one order of magnitude higher than that of typical diaphragm-based pressure sensors. A numerical model was also presented for investigating the characteristics of the sensitivity of the electrokinetic pressure sensor. Numerical res...