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 results showed that the sensitivity increases as the cation concentration decreases and the channel width increases. In the present study, electrokinetic energy conversion phenomena are employed for sensing mechanism up for the first time. That enhances our sensing capabilities to measure the outputs and to qualify the flow characteristics of the microfluidc devices. Experimental data showed that the linear range of the electrokinetic flow meter is two orders of magnitude wider than those of typical micro flow meters and that the sensitivity of the electrokinetic pressure sensor is one order of magnitude higher than those of conventional micro pressure sensors. In addition, the electrokinetic sensors do not have any moving part and do not require additional power source.
Nanotechnology 및 Biotechnology가 발전함에 따라서, 미량의 유체를 제어하는 기술인 Microfluidics의 발전과 함께, Microfluidic devices 내의 유량 및 압력을 더욱 쉽게 관찰, 측정, 조절하고자 하는 요구가 증가하였다. 본 연구에서는 이러한 요구의 증대에 발맞추어 동전기식 에너지 변환 현상을 이용한 새로운 미소 유량계와 미소 압력계에 대한 연구를 수행하였다. 본 연구에서 개발한 센서들은, 미소 유로의 계면에 자연적으로 발생하는 양이온과 음이온의 농도차에 의해 미소 유로 내에 유체가 흐를 때 발생하는 전기적 신호를 측정함으로서, 유량이나 압력을 측정할 수 있다. 첫째, 본 연구에서는 마이크로 채널 내의 동전기적 에너지 변환 현상을 이용한 미소 유량계를 개발하였다. 본 연구에서는 용액의 농도에 무관하게 동전기적으로 유량을 측정할 수 있는 방법을 제안하였고 실험적으로 검증하였다. 연구 결과 동전기식 미소 유량계는 여러 가지 농도를 가지는 용액의 유량을 10% 이내의 오차로 측정할 수 있음이 보여졌으며 기존의 유량계와 비교할 때, 100배 이상의 넓은 측정 범위를 가진다는 것이 밝혀졌다. 둘째, 본 연구에서는 나노 채널 내의 동전기적 에너지 변환 현상을 이용한 미소 압력계를 제안하고 실험적으로 검증하였다. 연구 결과 본 연구에서 제안된 압력계는 여러 가지 농도를 가지는 용액의 압력을 10% 이내의 오차로 측정할 수 있었다. 동전기식 압력계의 최대 민감도는 18.5μV/Pa로서 기존 압력계의 수십배의 민감도를 가진다.
