Color tunable pressure sensors based on polymer nanostructured membranes for optofluidic applications

Abstract

We demonstrate an integrated optical pressure sensing platform for multiplexed optofluidics applications. The sensing platform consists in an array of elastomeric on-side nanostructured membranes -effectively 2D photonic crystal- which present colour shifts in response to mechanical stress that alter their nanostructure characteristical dimensions, pitch or orientation. The photonic membranes are prepared by a simple and cost-effective method based on the infiltration of a 2D colloidal photonic crystal (CPC) with PDMS and their integration with a microfluidic system. We explore the changes in the white light diffraction produced by the nanostructured membranes when varying the pneumatic pressure in the microfluidics channels as a way to achieve a power-free array of pressure sensors that change their reflective colour depending on the bending produced on each sensor. The structural characterization of these membranes was performed by SEM, while the optical properties and the pressure-colour relation were evaluated via UV-Vis reflection spectrometry. Maximum sensitivities of 0.17 kPa −1 is obtained when measuring at Littrow configuration (θ in = −θ out ), and close to the border of the membranes. The reflected colour change with pressure is as well monitorized by using a smartphone camera.

Mechanochromism in Structurally Colored Polymeric Materials

“…Adapted with permission. [ 79 ] Copyright 2019, Springer Nature. c) Array of semiconducting rods (scale bar 1 µm), and d) embedded in PDMS for use as a mechanotunable laser.…”

Mechanochromism of Structural‐Colored Materials

“…[ 34,35 ] Recently developed mechanochromic structural‐colored materials have extended the responsive functions from conventional mechanical stimuli to complex signals such as electric stimuli. [ 10 ] In addition, although the color shift is a predominant method to achieve mechanochromic behavior, [ 34–36 ] increasing efforts have been made to develop mechanochromism based on polarization and transparence. [ 11,37,38 ] As one of the rapidly developing intelligent materials with multiresponse, [ 34,39,40 ] mechanochromic structural‐colored materials have become promising in various applications, such as mechanical sensing, [ 11,41 ] colorful displays, [ 10,42 ] anti‐counterfeiting, [ 26,37 ] and healthcare materials.…”

An Easy Method for Pressure Measurement in Microchannels Using Trapped Air Compression in a One-End-Sealed Capillary

“…However, due to the limited range of microchannel dimensions, it is very difficult to integrate an additional pressure-sensing functionality without disturbing the flow field [ 25 , 26 , 27 ]. Therefore, measuring pressure inside microchannels is challenging and novel methods are demanded [ 28 , 29 , 30 , 31 ].…”

“…Several methods have been proposed in the literature for pressure measurement inside microchannels [ 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ]. The majority of these published approaches are mechanical in nature and primarily use a membrane that deflects as a function of the applied pressure [ 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ].…”