Towards robust biosensors based on pulsed streaming potentials in microfluidic channels: Online correction and output signal selection

Pulsed streaming potential (SP) measurements in microfluidic format have been explored as a simple and rapid biosensing tool, but large day-to-day variations of the measurements, i.e. relative standard deviation (RSD) greater than 10%, are frequently encountered if the SP values are directly used as the output signal. To improve the long term stability of SP based sensor, a micro conductivity probe and a micro pressure sensor were incorporated into the sensing unit along with the implementation of a reference channel so that corrected SP values were utilized as the response signal. The results showed that day-to-day stability could be significantly improved and RSDs could be reduced from approximately 15% to less than 5% by incorporating a reference channel and using the SP ratio of two channels as the output signal. The variation of SP values caused by conductivity and pressure variation could also be corrected by using a reference channel, RSDs < 1% could be achieved with conductivity changing from 186 to 865 μS cm−1 and pressure increasing from 10 to 70 kPa. Utilization of a reference channel is therefore useful for developing a robust label-free biosensing platform based on pulsed SP measurements.