IoT-Enabled Flexible Sensors Can Be Applied Like a Temporary Tattoo
Matthew Greenwood posted on August 07, 2019 |
Engineers use nano ink and hydrogel to create transfer-printed electrodes.

A team of South Korean engineers have developed flexible high-performance sensors that can be applied to irregular or flexible surfaces like clothing or skin.

The team developed a transfer-printing technology that uses hydrogel and nano ink to create sensors that can be applied in the same way as a temporary tattoo: you place the sensor on a chosen surface and peel away the backing material, leaving the sensor itself stuck to the surface.

The researchers, working at the Korea Institute of Science and Technology (KIST), used an inkjet printer to print a liquid-based nano ink solution onto a porous hydrogel layer. The material was then applied to an irregular surface and allowed to dry. The liquid in the nano ink evaporated, leaving behind only the solidified nanomaterial.

That nanomaterial can be used to create electrodes—and in fact, the nanonetworks that are made are particularly effective electrodes due to their purity and uniformity. And because the amount of ink used is so small, the electrodes can form quickly. In addition, due to the hydrophobic nature of the material, it’s relatively easy to transfer it to the target surface since there is such little interaction with the hydrogel.

The new technology is particularly useful in creating sensors that will attach to surfaces that are thermally or chemically sensitive—a common demand for wearable devices. Current transfer printing processes are limited to creating sensors that can only be applied to flat surfaces. By creating sensors that can bend and stretch along with varied surfaces like fabric or skin, the range and possibilities for wearables could be significantly expanded.

The KIST team has tested the sensor’s effectiveness by applying the nanoelectrodes to a glove to see how well it detects finger movements and creating a pressure sensor that can measure the wearer’s pulse in the wrist.

“The outcome of this study is a new and easy method for creating flexible, high-performance sensors on surfaces with diverse characteristics and structures,” said Hyunjung Yi of KIST’s Post-Silicon Semiconductor Institute. “We expect that this study will be utilized in the many areas that require the application of high-performance materials onto flexible and/or nontraditional substrates, including digital health care, intelligent human-machine interfaces, medical engineering, and next-generation electrical materials.”

The wearable technology sector is growing, and there is increasing demand for devices that can be incorporated into clothing or applied directly to the skin. Developments like KIST’s “sensor tattoo” have the potential to open up the market to new possibilities.

Want to read more about flexible electronics? Check out Flexible Solar Cells with Flexible Applications.

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