Contact CMOS imaging of gaseous oxygen sensor array

Abstract

We describe a compact luminescent gaseous oxygen (O2) sensor microsystem based on the direct integration of sensor elements with a polymeric optical filter and placed on a low power complementary metal-oxide semiconductor (CMOS) imager integrated circuit (IC). The sensor operates on the measurement of excited-state emission intensity of O2-sensitive luminophore molecules tris(4,7-diphenyl-1,10-phenanthroline) ruthenium(II) ([Ru(dpp)3]2+) encapsulated within sol–gel derived xerogel thin films. The polymeric optical filter is made with polydimethylsiloxane (PDMS) that is mixed with a dye (Sudan-II). The PDMS membrane surface is molded to incorporate arrays of trapezoidal microstructures that serve to focus the optical sensor signals on to the imager pixels. The molded PDMS membrane is then attached with the PDMS color filter. The xerogel sensor arrays are contact printed on top of the PDMS trapezoidal lens-like microstructures. The CMOS imager uses a 32 × 32 (1024 elements) array of active pixel sensors and each pixel includes a high-gain phototransistor to convert the detected optical signals into electrical currents. Correlated double sampling circuit, pixel address, digital control and signal integration circuits are also implemented on-chip. The CMOS imager data is read out as a serial coded signal. The CMOS imager consumes a static power of 320 µW and an average dynamic power of 625 µW when operating at 100 Hz sampling frequency and 1.8 V DC. This CMOS sensor system provides a useful platform for the development of miniaturized optical chemical gas sensors.

Optical methods for sensing and imaging oxygen: materials, spectroscopies and applications

“…The respective instrument has a size of 48 Â 148 Â 20 mm and weighs only 96 g. It is powered by batteries and gives luminescence intensity data on dissolved oxygen. A miniaturized sensor with a size smaller than a fingernail was obtained 192 by integrating an oxygensensitive ormosil film with a low-power complementary metal oxide semiconductor (CMOS) chip.…”

Micro- and nanostructured sol-gel-based materials for optical chemical sensing (2005–2015)

“…Another O 2 sensor was fabricated by forming an array of one hundred separate O 2 -sensing elements of the size of 100 μm and 1 μm thick printed on a single LED [44]. The sol-gel formulations can be also an active part of more sophisticated configurations fabricated by a direct integration of sensor elements with optical filters and placed on an integrated circuit [45] or even artificial neural networks [46].…”

CMOS Photodetectors

“…PDMS can be doped with apolar hydrophobic color dyes such as Sudan-I, -II or -III to form optical filters that work in different regions of visible electromagnetic spectrum [109]. The Authors group recently proposed a prototype compact optical gaseous O 2 sensor microsystem using xerogel based sensor elements that are contact printed on top of trapezoidal lens-like microstructures molded into PDMS that is doped with Sudan-II dye as shown in Figure 20 [110]. The molded PDMS structure serves triple purpose acting as immobilization platform, filtering of excitation radiation and focusing of emission radiation onto the detectors.…”