In-plane all-photonic transduction with differential splitter using double-step rib waveguide for photonic microcantilever arrays

Integrated Opto-mechanical Cantilever Sensor with a Rib Waveguide

An integrated opto-mechanical cantilever sensor with a rib waveguide is reported in this paper. The device consists of a rib waveguide cantilever with buried waveguides on silicon. The rib cantilever is introduced to match better with the buried waveguide, further for increasing the interface coupling efficiency. With this configuration, single-mode operating can be achieved in transverse direction without decreasing the width of optical waveguide cantilever. The system sensitivity is 1.1 μm^-1 which is increased by about 21%, compared with the conventional structure. This article is protected by copyright. All rights reserved.

Transient deflection response in microcantilever array integrated with polydimethylsiloxane (PDMS) microfluidics

We report the integration of a nanomechanical sensor consisting of 16 silicon microcantilevers with polydimethylsiloxane (PDMS) microfluidics. For microcantilevers positioned near the bottom of a microfluidic flow channel, a transient differential analyte concentration for the top versus bottom surface of each microcantilever is created when an analyte-bearing fluid is introduced into the flow channel (which is initially filled with a non-analyte containing solution). We use this effect to characterize a bare (nonfunctionalized) microcantilever array in which the microcantilevers are simultaneously read out with our recently developed high sensitivity in-plane photonic transduction method. We first examine the case of non-specific binding of bovine serum albumin (BSA) to silicon. The average maximum transient microcantilever deflection in the array is -1.6 nm, which corresponds to a differential surface stress of only -0.23 mN m(-1). This is in excellent agreement with the maximum differential surface stress calculated based on a modified rate equation in conjunction with finite element simulation. Following BSA adsorption, buffer solutions with different pH are introduced to further study microcantilever array transient response. Deflections of 20-100 nm are observed (2-14 mN m(-1) differential surface stress). At a flow rate of 5 μL min(-1), the average measured temporal width (FWHM) of the transient response is 5.3 s for BSA non-specific binding and 0.74 s for pH changes.

Sensitivity enhancement of differential splitter-based transduction for photonic microcantilever arrays

We report enhanced sensitivity for in-plane photonic transduction of static deflection of microscale cantilevers by modifying the mode structure of double-step rib waveguides used to capture light from the free end of waveguide microcantilevers. A measured sensitivity of 0.77 x 10( - 3) nm( - 1) is achieved, comparable to the best reported for the optical lever method and over two orders of magnitude larger than for piezoresistive transduction. The corresponding minimum detectable deflection is 59 pm for a 3.5 Hz measurement bandwidth.