Renmin University of China makes cheap and scalable temperature sensors to measure multifaceted temperatures

The results of this study, published in the journal ACS Sensors, describe this very simple build in an article on the theme Ultrafast Paper Thermometers Based on a Green Sensing Ink. : The researchers used paper as a flexible substrate and realized their non-volatile and hydrophobic properties with ionic liquids, 1-ethyl-3-methyl imidazolium bis (trifluoromethylsulfonyl)imide ([EMIm] [Tf2N]).

By pen or inkjet printing transfer to ordinary A4 paper, the ionic liquid continues to the paper due to the capillary effect and does not leak even during bending and folding. The conductivity of the ink traces was measured between two sputter electrodes (5 mm x 1.5 cm in size in the experiment) connected to an external power source. It is extremely sensitive to changes in the outside temperature and, despite repeated folding and bending, provides a reliable temperature reading.

The response time of this paper thermometer to heating was approximately 8 seconds, the researchers noted, regardless of the difference in conductivity at different test temperatures.

Researchers have taken the new thermistor concept to another level, forming 8 parallel gold electrodes on one side of A4 paper, and 64 hand-written ionic liquids on the other side of the paper, aligned with the electrodes (therefore the ink will penetrate The paper reaches the gold electrode) and another set of eight parallel gold electrodes is deposited so that it is perpendicular to the opposite side electrode.

The researchers thus implemented an 8 x 8 temperature sensing array that was able to output a thermal profile of temperature on paper. To validate this thermal map experiment, the researchers used an infrared camera and emphasized that the paper-based temperature sensing array proved extremely versatile because it can detect the temperature of the surface at the same time. The paper can be folded around the object and measure the temperature on each side of the surface, and thus is different from the direct observation reading from the thermal camera.

To demonstrate the scalability of the design, ionic inks can be used in conjunction with inkjet printers to print a specific mission pattern over a large area. This new method, which can be used to mass-produce low-cost, foldable and disposable real-time thermometers, has now achieved relevant patents.

(Original Title: Paper thermometer can monitor the surface temperature of each side of the object)