Michael Mayer worked with researchers from the University of Michigan and UC San Diego on stacks of hydrogels with varying strengths of salt water.
The researchers harvested energy from the electric potential across the ion gradients created by the hydrogels. As more hydrogels were stacked on top of each other, the greater the voltage increase. The researchers were able to produce up to 110 volts.
Anirvan Guha, graduate student at the University of Fribourg's Adolphe Merkle Institute, is presenting the research during the 62nd Biophysical Society Annual Meeting in San Francisco this week.
To stack the thousands of individual hydrogels necessary to generate over 100 volts, the researchers used a printer that deposits small droplets of gel with the precision and spatial resolution to print an array of almost 2,500 gels on a plastic substrate. These gel precursor droplets were then cured with a UV light to convert them into solid gels. Alternating high-salinity and low-salinity gels (red and blue gels, respectively, above) were printed onto one substrate, and alternating cation-selective and anion-selective gels (green and yellow gels, respectively) were printed onto a second substrate. When overlaid, these gels connect to form a conductive pathway of 612 cells that can be used to generate up to 110V.
The team's next goal is to increase the current running through the hydrogel. "Right now, we're in the range of tens to hundreds of microamperes, which is too low to power most electronic devices," said Guha.
In the future, the research team hopes their results will help develop power sources for implantable devices that can use the ion gradients that already exist within the human body. "Then you may be able to create a battery which continuously recharges itself, because these ionic gradients are constantly being re-established within the body," he said.