May 23, 2017 | Updated: 03:58 PM EDT

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Nano-sized Sensors Show How Heat Diffuses In And Out Of Living Cells

Apr 21, 2017 01:58 AM EDT

(Photo : KAUST Rami ElAfandy/ The gallium nitride nanomembrane (GaN NM) is shown attached to a cell.

Researchers have devised tiny flat sensors and attached them to the surface of living cells. They offer detailed measurements of heat transfer at the very surfaces of the cell. Hence, such novel sensors provide innovative diagnostic techniques. They also give some solutions to the practical challenges of working with the cells.

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The sensors have been created at King Abdullah University of Science and Technology (KAUST), Saudi Arabia, according to They have been developed by Professor Boon Ooi, his Ph.D. student Rami Elafandy and co-workers. The sensor devices were developed from gallium nitride nanomembranes only 40 nanometers thick. They can locate various kinds of cancer cells.

Elafandy explained that a micro-sized, flexible, biologically integrated thermal transport sensor can make an impact on a number of applications, right from "plants physiological ecology and thermal imaging and treatment of cancerous cells, to thermal dissipation in flexible semiconductors and thermoelectrics," in his paper titled 'Nanomembrane-Based, Thermal-Transport Biosensor for Living Cells' according to OnlineLibrary.

After studying optical, mechanical and electrical properties of living cells, there is still little information on their thermal properties, according to Elafandy. Involving in the study of tiny cell volumes and irregular cellular shapes through sensors provides a number of challenges.

"Cells have irregular curved contours, meaning it's difficult to have a firm contact with them without damaging their membranes," said ElAfandy. "We utilized the high flexibility of nanomembranes to follow the cellular contours and minimize any temperature drops within the cell-sensor interface that would yield errors."

First, the researchers attached the sensor to the cell surface. They then applied a pulsed ultraviolet laser beam that heated the nanomembrane and led to a photoluminescent emission of light at varied frequencies. They were dependent on the temperature of the nanomembrane which was involved in the transference of heat into the cell.

Thus, measuring the frequency of the photoluminescent light through nanosensors, scientists found the thermal conductivity of the cells that permitted heat to flow smoothly. They also measured the thermal diffusivity, which showed the storage of thermal energy by the cell.

However, the researchers had to overcome some challenges while using sensors. They used lasers that could result in damage to cells. They also found that the nanomembranes are so thin that they cannot absorb hazardous laser light, according to ElAfandy. The team came up with solutions by inserting a thin gold disc between the nanomembrane and the cell. It could absorb the laser radiation that was transmitted, even as it allowed heat to diffuse from the nanomembrane to the cell.

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