The ability to harness energy by integrating micro-technology into the soles of shoes has great protentional (absolutely no pun intended), however, applications to date have been very limited. Electrical energy generated from biomechanical movement e.g. walking, can only produce fluctuating amplitude and variable frequencies. The output is alternating current (AC), which can only power applications such as LED lighting. To energise mobile devices etc., the high voltage and low current needs to be converted to low voltage and higher current (DC), and this requires a (heavy) transformer.
A step forward came when the researchers at the School of Materials Science and Engineering at Georgia Institue of Technology used a triboelectric nanogenerator (TENG) based shoe insole to produce a maximum output voltage and current density up to 220 V and 40 mA, respectively when the wearer was walking.
The two phase procedure involved a small capacitor which captured the alternating current generated by walking. In the second phase, the electricity was feed into a battery which supplied DC current at voltages appropriate for powering wearable and mobile devices. By matching the impedance of the storage device to triboelectric generators, energy efficiency was increased up to 60 percent. The triboelectric effect takes advantage of the fact that certain materials become electrically charged after they come into moving contact with a surface made from a different material. According to the researchers, the power management system converted the fluctuating power amplitudes and variable frequencies to a continuous direct current, which could drive just about any device. Although further research and development is ongoing the future for high tech footwear is looking good.