Real-time embedded pressure and flow rate sensor in polydimethylsiloxane-based microchannel using fiber Bragg grating technique

Polydimethylsiloxane (PDMS) has attracted huge interest as the soft material for microchannel fabrication, due to its high biocompatibility, durability and low cost. The rheological properties of the fluid and the deformable properties of PDMS substrate have imposed significant impacts on the fluid flow in the microchannel, therefore it is of critically importance to develop sensing methods for the accurate flow rate monitoring and the flow-induced pressure measurement without disturbing the fluid flow in the microchannel. This paper presents an embedded and miniaturized pressure sensor based on the Fiber Bragg Grating (FBG) technique for the measurement of both flow rate and flow-induced pressure in PDMS-based microchannel. This method has demonstrated a pressure sensitivity of 0.06 p.m./Pa and the Limit of Detection (LoD) for pressure is 19.5 Pa. The linearity between flowinduced pressure and flow rate in PDMS-based microchannel is about 4.86 Pa(ml/h)-1 based on simulation results and is within the range between 4.33 Pa(ml/h)-1 and 6.67 Pa(ml/h)-1 obtained from experimental results. The LoD of flow rate using this method is within the range between 2.9 ml/h and 4.5 ml/h. The random instability induced by the operation of the reconnection of syringe back to the liquid flow system was identified and the calibration of this instability is also presented in this paper. Using this method, the pressure and flow rate within PDMS-based microchannel can be monitored with high reliability and high sensitivity, and this will benefit the application of PDMS-based microfluidics in areas that require highly precise control in flow conditions, e.g. biosensing, cell culture, and drug delivery.