Researchers out of Purdue University, in West Lafayette Indiana, have invented a foodborne illness detector that is portable. The small detector works with a smartphone or laptop and detects E.coli 0157:H7.
The United States sees about one in six people per year that suffer from foodborne illness. There are more than 31 recognized pathogens that are transmitted to humans through food, one of the harshest is E.coli, especially the E.coli strain 0157:H7.
The detector uses the silicon photomultiplier (SiPM) and utilizes low light from a bioluminescent assay to detect the presence of bacteria, that can cause foodborne illness in food samples. They also invented an electrical circuit with an amplifier, comparator, and microcontroller to send the data to smartphones and laptops via Bluetooth technology. 3D printing was used to build a cradle for the SiPM.
Proof of Concept was presented by the team, by testing the device with artificially contaminated samples of ground beef from a local grocery store. The team then injected a sample of E.coli into the beef, then within ten hours, analyzed the beef with the SiPM.
The next phase is to rinse the beef and incubated it with an enrichment liquid containing a modified phage (a virus for bacteria). The phage infects the beef with harmful foodborne bacteria so when a substrate is added the bacteria emit light, which is then detected by the SiPM.
Specifications
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- Photodetection efficiency (PDE) ranges 20% to 50% – similar to a PMT
- Also similar to a PMT Gain (G) is about 106
- G vs. Vb dependence is linear. It is not similar to a PMT
- Photon arrival time resolution is about 100-300ps with a timing jitter that is optimized
- Signal parameters are nearly independent of external magnetic fields, which is not like Vacuum PMTs
- Dark count density is the frequency of pulses in absence of illumination (105-106 pulses/s/mm2)
- Small dimensions and lower voltages permit extremely, light and robust mechanical design.
SiPM in medical imaging is an attractive contender for the replacement of PMT in PET and SPECT imaging. They are obvious choices because they provide high gain, low voltage, and faster response times. They are also compact and compatible with magnetic resonance systems. There are several challenges facing the widespread use of SiPM, namely the units require optimization for larger matrices, digitation, and signal amplification.
For more information see the Purdue University study announcement
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