They used a form of multi-walled carbon nanotube "yarn" to construct a microscopic structure for the biofuel cell.
"This provides an environment that gives stability to the enzymes and an environment that occludes the types of things that can poison the enzyme, therefore degrading its performance over time," says Wallace.
The end result was a biofuel cell with an extended lifetime and a higher power density 2.2 milliwatts per square centimeter.
"In terms of the power density it's a factor of two or three above what we were getting. That's probably not staggering, but it is significant," says Wallace.
"What is more significant is the length of time we can operate these biofuel cells for."
The researchers are aiming to develop the carbon nanotube yarn biofuel cells to power an implant that will help regenerate nerve damage.
"Our initial target is for peripheral nerve repair, whether that's a finger or other limbs."
The idea is to implant the conduit in the area where the nerves need to be regenerated, and the biofuel cells will produce a tiny electric current to stimulate nerve growth without requiring batteries or an external power source.
Wallace and his collaborators are also working on improving the power output and lifetime of biofuel cells even further.
"That then opens them up to powering all sorts of implants, not just this temporary power supply to repair a damaged area, but a power supply that will be able to service in an ongoing prosthetic, like the vagus nerve stimulators for epilepsy or for chronic pain management."
The ultimate goal is to boost output and longevity to the point that biofuel cells can power a broad range of biomedical implants.
"If you can think of any type of device that is implantable that requires energy, this would be a great way to power it so you don't have to go in and change the batteries all the time," says Wallace.