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Sensor Performance Improved with New ‘Optofluidic’ Technology

By combining the diatom, one of nature’s miniature miracles, with a version of inkjet printing and optical sensing, a team of researchers from Oregon State University have designed an excellent sensing device that may be nearly 10 million times more sensitive than other approaches. The new “optofluidic” technology has been approved a patent. The research details have been published in the Nanoscale journal.

Diatoms and inkjet printing are components of this 'optofluidic' sensor created at Oregon State University. (Graphic courtesy of Oregon State University)

This approach has the potential to enhance biomedical sensing of cancer biomarkers when implemented in working devices. It may also have application in extremely precise forensics work, detection of illegal drugs, saving the lives of military personnel in combat situations, and in helping detect whether organic food is free of pesticide or not.

The researchers state that the technology’s high level of sensitivity and low cost may have infinite applications such as environmental protection, health monitoring, biological experiments and other uses.

Some existing sensors can detect compounds at levels of one part per billion, which sounds pretty good, but for many purposes that’s not good enough.

With this approach, we can detect some types of compounds at less than one part per trillion, about the level of a single molecule in a small sample. That’s really difficult. Aside from its sensitivity, the technology can also work with ultra-small samples, is fast, and should be very inexpensive to use.


Alan Wang, an OSU assistant professor of electrical engineering in the OSU College of Engineering, corresponding author on the study

This system integrates modern optics with a fluidic system to identify compounds. With most traditional systems of this type, fluids have to flow over a surface, and this restricts the movement of specific molecules which researchers might want to identify, Wang said.

But the diatoms in this new technology serve as natural “photonic crystals.” They harness convection forces against diffusion to help speed up and concentrate molecules in a space in which photons from optical sensors can get trapped, cooperate with and identify the compound via optical signatures.

A diatom is a natural, living type of phytoplankton that creates very precise, tiny structures. When liquids are deposited on it with carefully controlled inkjet devices, the droplets evaporate quickly, but, in the process, carry the molecules of interest to the diatom surface. This is the key to increasing the sensitivity of the photonic measurements.

Alan Wang, an OSU assistant professor of electrical engineering in the OSU College of Engineering, corresponding author on the study

The team states that sensor technology can rapidly and accurately identify the types of compounds present, and roughly how much are present.

During one experiment, the researchers tried to identify trinitrotoluene (TNT), one of the basic ingredients in explosive devices – including the hidden mines that have caused several injuries and deaths in battle situations. TNT is a chemical possessing very low volatility, meaning it has limited evaporation, and comparatively only some molecules escape which could facilitate detection. It is tough to find in a hidden bomb.

Wang explains that this new technology, when tested, was one million more times sensitive at detecting TNT than other general approaches. A monitor based on this technique, which could be quick and accurate in military scenarios, could help save lives in the future, he added.

Washington State University collaborated with the research team. The research was supported by the National Institutes of Health and the U.S. Department of Defense. OSU officials said commercial applications of the technology are being investigated.

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