A microcantilever-based viscometer for inline determination of liquid viscosity

Inline viscosity monitoring is crucial for process control in many industrial plants. In this study, a viscometer was designed and fabricated based on microfluidic technology, and the influence of effective parameters on its performance was investigated. The construction of the viscometer involved the fabrication of two microcantilevers using polydimethylsiloxane. One microcantilever was designed with a circular cross-section featuring a diameter of 300 mu m, while the other was crafted with a triangular cross-section, characterized by a base of 270 mu m and a height of 250 mu m. Both microcantilevers measured 3 mm in height and were meticulously positioned within separate millichannels; each dimensioned at 2 x 5 x 30 mm3. The precision required for the millichannels and additional components was achieved using a mini-CNC milling machine. To evaluate the performance of the viscometer, a series of water-glycerol solutions comprising 50%, 60%, 65%, 70%, 75%, and 80% glycerol were injected into a microchannel. The flow rate was systematically varied between 3 and 18 ml min-1 in increments of 3 ml min-1, utilizing a syringe pump for precise control. The resultant displacement of the microcantilever, attributed to the fluid flow, was meticulously recorded using a digital camera. According to the experimental results, the displacement curves of circular and triangular microcantilevers are linear with viscosity; increasing the viscosity and flow rate of the fluid passing through the millichannel increases the microcantilever displacement rate. The response time of the microcantilever with a circular cross-section is 3 to 9 s, and that of the microcantilever with a triangular cross-section is 2 to 12 s. Also, the results of multiple tests in the same conditions showed that the system has a repeatability error of 4%. Finally, it can be concluded that the proposed device can be used to measure the viscosity of liquids within a specific range.