MIT's 'electronic nose' could detect hazards
~ a tiny "electronic nose" engineered by MIT researchers with a novel inkjet printing method
~ could be used to detect hazards including carbon monoxide, harmful industrial solvents and explosives
~ led by MIT professor Harry Tuller
~ the researchers have devised a way to print thin sensor films onto a microchip
~ this process that could eventually allow for mass production of highly sensitive gas detectors
~ mass production would be an enormous breakthrough for this kind of gas sensing technology according to the professor of Materials Science and Engineering
~ the prototype sensor consists of thin layers of hollow spheres made of the ceramic material barium carbonate,
~ which can detect a range of gases
~ using a specialized inkjet print head, tiny droplets of barium carbonate or
~ other gas-sensitive materials can be rapidly deposited onto a surface in any pattern the researchers design
~ the miniature, low-cost detector could be used in a variety of settings
~ from an industrial workplace to an air-conditioning system to a car's exhaust system
~ for a sensor to be useful, it must be able to distinguish between gases
~ to achieve this, sensors should have an array of films that each respond differently to different gases
~ this is similar to the way the human sense of smell works
~ the way we distinguish between coffee's and fish's odor is not that we have one sensor designed to detect coffee and one designed to detect fish
~ our nose contains arrays of sensors sensitive to various chemicals
~ over time, we train ourselves to know that a certain distribution of vapors corresponds to coffee
~ in previous work designed to detect nitrogen oxide (NOx) emissions from diesel exhaust,
~ the researchers created sensors consisting of flat, thin layers of barium carbonate deposited on quartz chips
~ however, the films were not sensitive enough, and the team decided they needed more porous films with a larger surface area
~ to create more texture, they applied the barium carbonate to a layer of microspheres,
~ hollow balls less than a micrometer in diameter made of a plastic polymer
~ when the microspheres are burned away, a textured, highly porous layer of gas-sensitive film is left behind
~ the resulting film, tens of nanometers (billionths of a meter) thick,
~ is much more sensitive than flat films because it allows the gas to readily permeate through the film and
~ interact with a much larger active surface area
~ at first, the researchers used a pipette to deposit the barium carbonate and microspheres
~ this process proved time-consuming and difficult to control
~ to improve production efficiency, the researchers took advantage of a programmable Hewlett-Packard inkjet print head
~ located in the MIT Laboratory of Organic Optics and Electronics
~ the inkjet print head, like that in a regular inkjet printer, can deposit materials very quickly and controllably
~ the special gas-sensitive "inks" used in this work were optimized for printing
~ this allows the researchers to rapidly produce many small, identical chips
~ containing geometrically well-defined gas-sensing films with micrometer dimensions
~ patterns of different gas-sensitive inks, just as in a color printer,
~ can be easily generated to form arrays with very little ink required per sensor
~ the team hopes to create large arrays of gas-sensitive films with controlled three-dimensional shapes and morphologies
~ the research is funded by the National Science Foundation.