Christian Pylatiuk attaches a small device to his right leg and starts walking. The 200g instrument does start generating electricity as he moves, though not much - just a few microwatts.

Pylatiuk and his colleagues at the Karlsruhe Institute of Technology (KIT) in Germany are among researchers around the world who are looking for solutions for so-called energy harvesting by movement.

Another one of their concepts is a prosthesis containing a piston that can be incorporated into a sports shoe. Walking pushes the piston into a generator, thereby creating energy. The idea has market potential, Pylatiuk believes, and could power athletic equipment.

The idea of generating energy with one's own body is by no means new. For example, in 2014, US inventors sought crowdfunding for a battery that would be charged by body movement. The project garnered a lot of interest, drawing US$310,000 (RM1.3mil) in funding in one month.

According to the maker, an hour of movement or sport would extend the battery life of a smartphone in normal use by up to an hour, or up to five hours in standby mode.

Scientists at the NanoTech Institute at the University of Texas at Dallas are working on yarns that could produce electricity by stretching or twisting. "Power generation by human movement is a way to end the demand for batteries," says the institute's Ray Baughman.

Robert Spanheimer, of the German information technology association Bitkom, sees potential in such inventions but warns against too much euphoria: "Some developments are still in the very early stages."

The rapid price decline in current battery technology is also a high economic hurdle for anyone wanting to enter the industry.

Peter Woias, a researcher with the Institute of Microsystem Technology at the University of Freiburg in Germany, is also sceptical of energy-harvesting technology. "A technology that is not noticeable and reaps the energy of human movements in appreciable amounts can't exist on physical grounds," he argues.

The KIT prosthesis, for example, has a very respectable performance, but in order to fully charge a smartphone with it, a person would have to run continuously for several hours.

In general, most of the energy-harvesting projects applied to the human body have failed because the necessary generators were too large or heavy for everyday life.

Micro-energy harvesting is different, Woias says, because it focuses on generating micro- and milliwatts to power low-energy systems.

Examples include weather stations or tyre-pressure testers.

Woias is currently researching systems to monitor wild animals that could generate their energy from the animals' movements. These systems could also be applied to household pets, he believes. — dpa