A new polydimethylsiloxane (PDMS) microcantilever with integrated optical waveguide for biosensing application

Abstract

This paper reports a novel biosensor monolithically integrate optical waveguide into PDMS microcantilever. The sensor consists of buried optical fibers, integrated optical waveguide and horizontal PDMS microcantilever suspended into microfluidic channel. The thin PDMS layer involves microcantilever, microfluidic cannels and optical channels fabricated using soft lithography technique. The thin layer is covered by semi-bonding of a glass slide and a PDMS layer to enable introducing the material of waveguide core into the waveguide channel embedded into PDMS microcantilever. The covering layers are then replaced by other PDMS layers which have hollow features to release the microcantilever for free deflection and to seal microfluidic network. The input and output multimode fibers are horizontally inserted into the optical channels. The light received at the input fiber is conducted through the optical waveguide microcantilever and is delivered to the output fiber. Numerical model is presented to simulate the optical performance of the optical waveguide PDMS microcantilever under fluid flow testing and to find the proper dimensions and waveguide material. The deflection of microcantilever under flow loading distorts the light and causes power loss at the output fiber. COMSOL Multiphysics 3.5 is used to perform fluid structure interaction analysis to assess the cantilever defection due to fluid flow and the optical simulation to estimate the power loss due to cantilever deflection. The proposed biosensor can be used to measure the force within the range of living cell growth force and to be integrated within bio-sensing microdevices to carefully measure the fluid flow rate.