An image contrast-based pressure sensor

• We developed an optomechanical, powerless pressure sensor.
• The sensor measures the pressure-dependent distance between two high contrast interfaces.
• The sensor can measure pressures at the 0–100 mBar range with 7% accuracy.
• The sensor can be fabricated at low cost and it is easy.

We present the design of an image contrast based fluid pressure sensing scheme that employs a powerless, low-cost, pressure sensor. The sensor consists of a sealed pressure microchamber whose top surface consists of a deformable, semi-transparent, polydimethylsiloxane (PDMS) membrane and its bottom surface consists of a rigid glass substrate. When the microchamber is pressurized, the membrane is deflected but the position of the glass substrate remains fixed and therefore the distance between them changes with applied pressure. Using a precision z-scanning module, the distance between the top and bottom surfaces is measured using a custom-made image contrast algorithm and the applied pressure is extracted. The image contrast is enhanced by adding food color during the fabrication of the membrane and by patterning the glass substrate with photoresist. The sensor operates over a pressure range of 0–100 mbar, with a ∼2 mbar resolution in the 0–20 mbar pressure range and ∼10 mbar resolution in the 20–100 mbar pressure range. The maximum error was measured to be less than 7% throughout its dynamic range. The novel pressure monitoring concept presented here can be used in various biomedical applications as well as in the consumer electronics industry.