Starch-based compound converts mechanical energy into electrical energy

The triboelectric nanogenerator (above) is made using an MOF made with cyclodextrin (circular molecule).


Scientists used a compound made from a derivative of starch and baking soda to help convert mechanical energy into electrical energy. The approach, developed by scientists at the Daegu Gyeongbuk Institute of Technology (DGIST), along with colleagues in Korea and India, is cost-effective and biocompatible, and can help recharge low-power electronic devices like calculators and watches. The details were published in the journal Advanced functional materials.

“Triboelectric nanogenerators recover mechanical energy and convert it into electric current,” explains Hoe Joon Kim, robotics engineer at DGIST. “But many materials used in these devices are considered biohazardous and unsuitable for portable applications. Our triboelectric nanogenerator incorporates cyclodextrin, a green material widely used for drug delivery in the human body, making it makes it environmentally friendly and dangerous -free. “

Cyclodextrin is a polysaccharide compound produced from starch. Scientists have used it to bind sodium ions together in what is called a metal-organic structure (MOF). MOFs form porous materials widely used in gas storage, catalysis and detection.

Specifically, Kim and his team applied ultrasound to a mixture of cyclodextrin and sodium bicarbonate in water. They then added trimesic acid and applied another short series of ultrasound. The process takes place at room temperature and leads to the formation of an MOF composed of sodium ions linked together by cyclodextrin bonds.

The team incorporated the MOF into a nanogenerator by covering it with a copper electrode, which sits on a plastic base of polyethylene terephthalate (PET). Opposite the MOF layer is a Teflon layer placed on a second copper electrode which is also glued to a PET sheet. Both sides of the nanogenerator open and close in response to movements, such as walking or jogging. Whenever MOF comes in contact with Teflon, electrons are exchanged and an electric current is generated. This process is called the triboelectric effect.

The team tested the device by attaching it to a shoe, backpack, and a person’s knee and abdomen. They discovered that it could harvest mechanical energy from walking, jogging, and flexing, and even some typical yoga movements. The device was able to drive low-power electronic devices like a digital wristwatch, hydrometer, and calculator.

“Our MOF expands the list of triboelectric materials,” Kim explains. He and his team plan to continue researching biocompatible materials that can be used in wearable applications. They are also working on the development of super capacitors capable of storing the energy generated by triboelectric nanogenerators. “By using the nanogenerator and the super capacitor together, we believe we can develop next-generation energy systems for portable electronics, bio-devices and robots,” he said.

– This press release was originally published on the Daegu Gyeongbuk Institute of Science and Technology website

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