India is a large consumer of fish, and this in turn generates a large quantity of fish “biowaste” materials. A team of scientists from Jadavpur University in Kolkata are keen on utilizing this enormous biowaste to began exploring ways to recycle the fish byproducts into an energy harvester for self-powered electronics.
Waste fish scales (upper left corner) are used to fabricate flexible nanogenerator (lower left) that power up more than 50 blue LEDs (lower right). An enlarged microscopic view of a fish scale shows the well-aligned collagen fibrils (upper right). The possibility of making a fish scale transparent (middle) and rollable (extreme left lower corner) is also illustrated. (Credit: Sujoy Kuman Ghosh and Dipankar Mandal/Jadavpur University)
The basic principle behind the team’s effort is simple. Fish scales are composed of collagen fibers that have a piezoelectric property, which means that an electric charge is produced as a reaction to applied mechanical stress. The research can be found in Applied Physics Letters, from AIP Publishing. In the research, they report how they successfully harnessed this property to fabricate a bio-piezoelectric nanogenerator.
To achieve this, the scientists initially
“collected biowaste in the form of hard, raw fish scales from a fish processing market, and then used a demineralization process to make them transparent and flexible,” explained Dipankar Mandal, assistant professor, Organic Nano-Piezoelectric Device Laboratory, Department of Physics, at Jadavpur University.
The collagens in the processed fish scales act as an active piezoelectric element.
We were able to make a bio-piezoelectric nanogenerator -- a.k.a. energy harvester -- with electrodes on both sides, and then laminated it.
It is a widely known fact that one collagen nanofiber displays piezoelectricity. However until recently, no attempt had been made to hierarchically arrange the collagen nanofibrils within the natural fish scales.
We wanted to explore what happens to the piezoelectric yield when a bunch of collagen nanofibrils are hierarchically well aligned and self-assembled in the fish scales. And we discovered that the piezoelectricity of the fish scale collagen is quite large (~5 pC/N), which we were able to confirm via direct measurement.
Further more, the polarization-electric field hysteresis loop and the resulting strain-electric field hysteresis loop -- evidence of a converse piezoelectric effect -- caused by the “nonlinear” electrostriction effect supported their discovery.
The team’s research is the first recognized demonstration of the direct piezoelectric effect of fish scales from electricity produced using a bio-piezoelectric nanogenerator under mechanical stimuli. Furthermore, this entire process does not require any post-electrical poling treatments.
“We’re well aware of the disadvantages of the post-processing treatments of piezoelectric materials,” Mandal noted.
The scientists used near-edge X-ray absorption fine-structure spectroscopy to investigate the fish scale collagen’s self-alignment attribute, which was measured at the Raja Ramanna Centre for Advanced Technology in Indore, India.
Theoretical and experimental tests helped them clarify the bio-piezoelectric nanogenerator’s energy scavenging performance. It can scavenge many types of ambient mechanical energies such as machine and sound vibrations, body movements, and wind flow. Even repetitively touching the bio-piezoelectric nanogenerator with a finger can power over 50 blue LEDs.
We expect our work to greatly impact the field of self-powered flexible electronics. To date, despite several extraordinary efforts, no one else has been able to make a biodegradable energy harvester in a cost-effective, single-step process.
Apart from its numerous uses for portable electronics, the team’s work has the potential for application in transparent electronics, edible electronics, e-healthcare monitoring, biocompatible and biodegradable electronics, self-powered implantable medical devices, surgeries, and in vitro and in vivo diagnostics. ,
In the future, our goal is to implant a bio-piezoelectric nanogenerator into a heart for pacemaker devices, where it will continuously generate power from heartbeats for the device’s operation. Then it will degrade when no longer needed. Since heart tissue is also composed of collagen, our bio-piezoelectric nanogenerator is expected to be very compatible with the heart.
The team’s bio-piezoelectric nanogenerator could also aid targeted drug delivery, which at present is generating interest as a means of recovering in vivo cancer cells and also to stimulate diverse types of damaged tissues.
“So we expect our work to have enormous importance for next-generation implantable medical devices,” he added.
“Our end goal is to design and engineer sophisticated ingestible electronics composed of nontoxic materials that are useful for a wide range of diagnostic and therapeutic applications,” said Mandal.