Converting a Cell Phone Into Powerful Chemical Detector for $50

With only $50 worth of components, an ordinary cellphone transforms into a sophisticated scientific instrument, capable of identifying chemicals, drugs, and pathogens.

Scientists from Texas A&M have developed an extension to an ordinary cellphone that turns it into an instrument capable of detecting chemicals, drugs, biological molecules, and pathogens. The advance is reported in Reviews of Scientific Instruments, by AIP Publishing.

Modern cellphones include high-quality cameras capable of detecting low levels of light and eliminating digital noise through software processing of the captured images. Recent work has taken advantage of this sensitivity to produce cellphone cameras that can be used as portable microscopes and heart rate detectors.

The current advance is based on two types of spectroscopy. One type, known as fluorescence spectroscopy, measures the fluorescent light emitted by a sample. Another, known as Raman spectroscopy, is useful for detecting molecules, such as DNA and RNA, that do not fluoresce or emit light at very low intensities. Both types were used to develop this cellphone detector.

The system includes an inexpensive diode laser as a light source, oriented at right angles to the line connecting the sample and the cellphone camera. The right-angle arrangement prevents back reflected light from entering the camera.

“In addition, this right-angle excitation geometry has the advantage of being easier to use for the analysis of samples where a bulk property is to be measured,” said author Peter Rentzepis.

The investigators studied a variety of samples using their constructed cellphone detector, including common solvents such as ethanol, acetone, isopropyl alcohol, and methanol. They recorded the Raman spectra of solid objects, including a carrot and a pellet of bacteria.

Carrots were chosen for this study because they contain the pigment carotene. The laser light used in their system has a wavelength that is easily absorbed by this orange pigment and by pigments in the bacteria.

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