PDMS Microcantilever-Based Flow Sensor Integration for Lab-on-a-Chip

In this paper, a simple practical method is presented to fabricate a high aspect ratio horizontal polydimethylsiloxane (PDMS) microcantilever-based flow sensor integrated into a microfluidic device. A multilayer soft lithography process is developed to fabricate a thin PDMS layer involving the PDMS microcantilever and the microfluidics network. A three-layer fabrication technique is explored for the integration of the microflow meter. The upper and lower PDMS layers are bonded to the thin layer to release the microcantilever for free deflection. A 3-D finite element analysis is carried out to simulate fluid-structure interaction and estimate cantilever deflection under various flow conditions. The dynamic range of flow rates that is detectable using the flow sensor is assessed by both simulation and experimental methods and compared. Limited by the accuracy of the 1.76-mu m resolution of the image acquisition method, the present setup allows for flow rates as low as 35 mu L/min to be detected. This is equal to 0.8-mu N resolution in equivalent force at the tip. This flow meter can be integrated into any type of microfluidic-based lab-on-a-chip in which flow measurement is crucial, such as flow cytometry and particle separation applications.