Sensing Platforms

Bioengineered Colorimetric Sensors for Environmental Monitoring H2S Sensor

Seung-Wuk Lee (UCB) and Amy Herr (UCB)

We have developed a simple real-time environmental monitor using bacteriophages, which have been bioengineered to have selective response to particular pollutants. The bacteriophages are controllably assembled onto strips, which are then exposed to varying concentrations of the toxic flame retardant polybrominated diphenyl ether, or PBDE. The color of the strips changes depending on the concentration of PBDE. This color change can be measured using a smart phone application that takes an image of the strip and analyzes the intensity of each primary color, which can then be correlated to the concentration of PBDE. This development enables real-time monitoring of environmental pollutant virtually anywhere.

Bioengineered bacteriophages with selective binding peptides are assembled onto strips that are used as environmental monitors. In this case the flame retardant PBDE is measured. The color of the strips changes (real-images on bottom right) depending on the concentration of PBDE. The change in color can be measured and analyzed using a smart phone camera and custom-made smart phone app.

Fast, Lightweight, Selective Low-Power Nanomaterials-based H2S Sensor

Willi Mickelson (COINS) and Alex Zettl (UCB)

Hydrogen sulfide (H2S) is an extremely toxic gas, which occurs naturally in oil and natural gas in very high concentrations and poses a threat to energy sector workers and populations close to oil refineries. Current methods of detecting H2S are rather expensive, slow, not robust, or consume large amounts of power.
We have developed a micro-heated nanoparticle-based H2S sensor that consumes less than 10mW of power and has negligible sensitivity to water and methane.We are able to heat the micro-heated sensor for one second or less and still achieve a stable, accurate measurement of H2S. The COINS H2S sensor can be cheaply made, consists of very robust materials, and can be measured with very simple electronics.

(Upper) Response of COINS nanoparticle sensor to 1-second heat pulses during exposure to 0, 10, and 50 ppm of H2S.
(Lower) COINS sensor response to five heat pulses during exposure to (from left to right) 5 ppm H2S, 13000ppm H2O (40% RH), and 5000 ppm CH4.

These results have been obtained with the aid of the Zephyr experiment automation program and the Zeptoscope plotter.

Membrane-Based Sensors

The Majumdar and Lee Labs have been focused on developing mechanical-stress and resonance-based sensing platforms to monitor both added mass and change in surface energy with binding activity. Currently, the Majumdar Lab in collaboration with the Maboudian Lab tests the efficacy of the TNT and DNT motifs with both quartz crystal microbalance-(QCM)-based and parylene-membrane-based capacitance sensor platforms.

Cantilever Sensors

Pruitt Lab (Stanford) has improved low frequency piezoresistive sensing systems having high force sensitivity with little background signal. The photolithographically fabricated silicon cantilever-based piezoresistive sensor exhibited excellent sensitivity (600 V/N) and low background signal. This sensor exhibited the lowest noise piezoresistive cantilever sensors reported to date with excellent stability over several days: The measured 1/ƒ noise is 1.2 nV/V √Hz. The Kenny Lab (Stanford) has also demonstrated dual-axis sensing which may be employed for differentiating directional binding effects.