An Improved Design for Chemomechanical Sensors: A Piezoresistive Pressure Sensor with a Mechanical Boss

Jeffrey Bates,Prashant Tathireddy,Sebastian Buetefisch,Jules Magda

doi:10.3390/chemosensors1030033

Jeffrey Bates, Prashant Tathireddy + Show 2 more

Open Access

https://doi.org/10.3390/chemosensors1030033

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Abstract

Stimuli-responsive hydrogels can be used to convert miniature pressure sensors into novel chemomechanical sensors via confinement of the hydrogel sample between a porous membrane and a piezoresistive diaphragm. Chemomechanical sensors could prove beneficial in a variety of applications, including continuous monitoring of bioreactors and biomedical systems. In this study, one hydrogel composition with a high sensitivity to changes in pH was tested in two different chemomechanical sensors in order to compare the data obtained from each sensor design. In the first and older chemomechanical sensor design, a prefabricated hydrogel sample is loaded into the sensor chamber using a screw-on cap. In the newer sensor design, a thinner hydrogel is synthesized in situ and is held in place by a silicon boss that is mechanically connected to a piezoresistive diaphragm. The newer design results in a decreased chemomechanical sensor response time (by 60 times), and maintains a high sensitivity to changes in environmental stimuli.

Highlights

Hydrogels are super absorbent network polymers consisting of three dimensional structures that can absorb and retain water and other aqueous fluids while maintaining the original structure
The following monomers were used as received from Sigma Aldrich: 2-hydroxypropyl methacrylate (HPMA), dimethylaminoethyl methacrylate (DMA) and tetraethylene glycol dimethacrylate (TEGDMA)
Assuming that the sensor response is under mass transfer control, the response time should depend on hydrogel thickness [24], which states that the hydrogel response is driven by diffusion

Summary

Introduction

Hydrogels are super absorbent network polymers consisting of three dimensional structures that can absorb and retain water and other aqueous fluids while maintaining the original structure. Hydrogels are made of water soluble monomer backbone molecules with a cross-linking molecule selected for either physical or chemical properties. Hydrogels are good candidates in biomedical applications because of their response to changes in the local environment. Hydrogels may swell or deswell depending on the conditions of the surrounding aqueous media. Hydrogels are known to respond to changes in pH, glucose concentration, ionic strength, temperature, electric field, solvent composition and pressure. The swelling response of pH-responsive hydrogels occurs as nitrogen groups on the dimethylaminoethyl methacrylate (DMA)

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