Miniaturized reflectance devices for chemical sensing

Abstract

This effort seeks to evaluate the potential of the TAOS TCS3200 RGB sensor chip in a reflectance configuration for use in target detection based on color changes in porphyrin indicators using alcohols as model targets. The chip was evaluated as provided by Parallax, Inc as a component of the TCS3200-DB which includes white LEDs, collimator lens, and standoffs for optimization of sensing distance. Nonlinearity in the response of the daughter board to color standards was observed. Signal noise levels were determined to be less than 1% within a given measurement and measurement-to-measurement variations of ~9% were observed. The device proved effective for detection of the color change in several porphyrins upon target exposure and for monitoring the time dependence of changes following exposure. An array of six porphyrins was used for demonstration of differential changes in response to specific targets. Proof-of-concept use of the porphyrin indicators onboard two types of unmanned aerial vehicles (UAVs) is described.

Autonomous Chemical Vapour Detection by Micro UAV

“…The aerial sensor reaction time shown in the EFT and MEFT outperform the identification of reaction for all reported aerially deployed sensors in [8][9][10]12,14,17] providing a development path to superior position, time and concentration estimation.…”

“…Johnson et al [17] presents a proof of concept pairing of a colour reflectance chemical vapour detection sensor with two types of micro-UAV. In their work, a controlled conditions indoor test of the sensor performance when mounted to micro rotary and fixed wing platform implementations was demonstrated, but this did not progress to a real-time system level assessment in a representative outdoor environment.…”

Reflectance-based detection of oxidizers in ambient air

“…Loading of the paper support was accomplished using 100 L of 20 M ammonium titanyl oxalate monohydrate in water which was drop-cast onto a 2.5 cm × 2.5 cm swatch [13]. This was followed by drying under vacuum at room temperature for 1 h. Cobalt (CoDIX), copper (CuDIX), and nickel (NiDIX) variants of Deuteroporphyrin IX bis ethyleneglycol (CAS 6239456-72-5) were prepared by reflux as previously reported [14,15]. Paper supported porphyrin indicators were prepared using a dip and dry technique.…”

“…Samples were then dried at 100 • C before storing in the dark in sealed plastic bags. This is a modification of the procedure described previously for preparation of the indicator materials [14].…”

“…The sensor hardware has previously been described for use with paper supported porphyrin indicators for the detection of alcohol vapor [14]. It relies on an array of commercially available color sensors and provides data output consisting of white, red, green, and blue color values.…”