Ultra-fast sensor reacts to humidity in the same way as a Hercules beetle

The device consists of a chitosan hydrogel sandwiched between a layer of disordered metal

nanoparticles and a reflective substrate. When the external humidity changes, the resonant frequency of the sensor changes because the chitosan hydrogel swells when wet and contracts when dry.

The ultra-high speed of the new sensor is achieved due to the porous space between the nanoparticles that make up the device.

Instant and customizable new responseThe hydrogel resonator can subsequently be used not only for colorimetric sensors, but also for anti-counterfeit applications and high-resolution displays.

“This new humidity sensor is unique in thatmakes it possible to scale production at low cost even when using nanomaterials and nanostructures,” explained Professor Ro, who led the study. “The introduction of moisture-sensitive color pixels into security codes allows them to be used as security tags for moisture-sensitive electronic devices, banknotes, passports and ID cards.”

In their development, scientists were inspired by natureHercules beetle native to South America. The insect has an amazing feature - to change the color of its shell depending on the conditions of external humidity. This is because the inside of the beetle's shell is made up of a porous lattice structure with square holes. When light of certain wavelengths hits the shell, it reflects them and displays different colors that change with humidity.

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