The future of free, portable energy: Wearable technology that powers your devices as you move

Small, flexible generators which convert movement into electricity could soon be the future of free and unlimited energy thanks to a breakthrough in energy harvesting technology.

Scientists from Loughborough University and the University of Surrey have created a unique device based on triboelectric nanogenerators (TENGs) which generate electricity from motion – in much the same way static electricity is produced. Until now, using TENGs has been incompatible with many day-to-day electronic devices due to their inability to produce a constant current.

Now, a team of researchers, led by Dr Ishara Dharmasena, of Loughborough’s School of Mechanical, Electrical and Manufacturing Engineering, in collaboration with Advanced Technology Institute of the University of Surrey, have found a way to produce a direct current (DC) from a unique TENG design, creating a steady flow of electricity and opening up the potential for real-world applications.

He said: “Triboelectric nanogenerators are effectively small scale, flexible, and sometimes stretchable, energy generators that convert movements in our surroundings such as human motion, machine vibrations, vehicle movements, wind and wave energy into electricity.“They are extremely versatile and can be constructed in a wide variety of shapes, weights and sizes – from a few mm2 to several m2.

“Unlike conventional mechanical energy harvesting methods, such as piezoelectric or electromagnetic devices which contain heavy and bulky components, toxic materials and rigid structures, TENGs can be constructed using low cost, lightweight, non-toxic and flexible materials. “The potential applications include the next generation wearable and implantable electronics, smart textiles, medical devices, IoT (Internet of Things) and 5G related sensors, smart pavements, smart floors, mobile phones and tablets.”

TENGs are made from dielectric materials, such as plastics, which accumulate static charge when they rub against each other. As these charged materials move back-and-forth in a TENG, they generate uneven instantaneous alternating electrical current (AC) signals.The current is then further processed and stored in a battery or capacitor to be used when needed. Therefore, a typical TENG produces sharp positive and negative current peaks during its operation. Dr Dharmasena said: “In our new technology, converting the alternating current into a direct flow involves phase shifting.”

“In this technology, an assembly of TENG units (poles) are used as a single device, where they are systematically excited to obtain a phase difference among their outputs.“This systematic excitation is obtained through their geometry and spatial arrangement. “The outputs with different phases are then superimposed to obtain the final DC output signal. “In the paper, we have demonstrated the applicability of this technology by continuously lighting a set of LED lights and a photodetector. “This new invention overcomes one of the most critical challenges of TENG technology and will enable countless real-time low-power applications in wearable electronics, such as IoT related applications and smart sensing, getting us one step closer towards a sustainable, autonomous and portable energy source.”

The paper, Direct current contact-mode triboelectric nanogenerators via systematic phase shifting, was recently published in the journal, Nano Energy

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