Multiscale Integrated Temperature/Flow Velocity Sensor Patches for Microfluidic Applications

Embedded sensors in microfluidic systems play a big role in different chemical and biological analyses. Versatile metal electrodes in microfluidic chips have been designed to detect the physical and chemical parameters of the fluid, but in situ monitoring by flexible and transparent embedded sensors still remains a significant challenge. Here, such a challenge is tackled for the first time, by simple fabrication of multiapplication sensing patches into a microfluidic chip. The sensing patches are made with polydimethylsiloxane (PDMS) and fluorescent dye. Different strategies of assembling sensing patches could be used to realize both local and dynamic sensing for multiscale detection. In Strategy 1, one sensing patch is utilized to measure the temperature of microheaters below 100 °C and its detecting resolution is 1.25 °C. In Strategy 2, four sensing patches are placed in four channels to monitor the real-time temperature change (23 °C–50 °C) in different microchannels. In Strategy 3, two sensing patches are fabricated in a microchannel, which has a high signal resolution to monitor the flow rate of less than $10 ~\mu \text{L}$ /min. The simple fabrication process and different combinatorial strategies facilitate the development of miniaturization and functionalization of microfluidic sensors, so as to realize the monitoring of more parameters and play a significant role in the fields of biological and chemical analysis.