At KPIT Sparkle 2018, Ramya Veerubhotla from the Indian Institute of Technology, Kharagpur represented a one-member ‘Team Electrodes’, which developed a bacteria-powered flexible and disposable battery using eyeliner coated paper electrodes.
Wastewater consists of organic matter and bacteria and separating microbes from wastewater is energy-intensive and tedious. Wastewater is considered a menace by various industries and Team Electrodes conducted a research on exploiting energy from it to power portable needs. Exploiting energy from wastewater, in terms of electricity, is usually done by microbial fuel cells. However, these microbial fuel cells constitute bulky chambers and expensive membranes limiting the portability.
The challenge for Team Electrodes was to fabricate a disposable, low-cost microbial fuel cell as well as use electrodes that are readily available and handy. The one-member team of Ramya Veerubhotla addressed the first challenge by fabricating the device using paper that is bio-degradable, foldable (hence compact, when multiple devices are connected) and versatile. Team Electrodes dealt with the other challenge by using eyeliner for the first time to fabricate electrodes.
Ramya Veerubhotla took a year and half to study the composition thoroughly as well as identify the components in the eyeliner that is responsible for conductivity (amorphous carbon). Team Electrodes synthetically prepared it in the lab and arrived at the conclusion that it is feasible to fabricate a paper battery using eyeliner-based electrodes.
Portable energy harnessing devices are integral to power supply of various electronic devices, medical implants, etc. These devices, when made on a paper platform, offer various advantages such as low cost, multi-functionality, versatility, flexibility and disposability. However, since electrodes are a crucial part in these devices, the tedious and multiple steps involved in the fabrication of electrodes currently limit the application of these devices.
Paper-based electrodes are conventionally fabricated by methods such as screen printing, inkjet printing, spin coating and chemical vapour deposition that can be tedious and time-consuming. It is important to note that chemicals used as fuels in these cells cause severe environmental hazards and are not bio-degradable. Hence, the focus should be on developing systems that can harness power using organic fuels such as wastewater that are readily available. This can be accomplished by microbial fuel cells that employ bacteria as catalysts, converting the chemical energy present in the wastewater directly into electricity (DC voltage).
Team Electrodes demonstrated that interfacing a microbial fuel cell onto a paper platform can generate self-sustainable and portable power sources, which can function even in remote locations. Ramya Veerubhotla developed an environment-friendly paper-based bio-battery that yields a power of 12.5 W/m3 and can be fabricated even by unskilled individuals using paper and eyeliner alone. Papers were used to host the bacteria and electrode fabrication is carried out by coating the papers with an eyeliner.
The device does not require expensive membranes such as Nafion. To provide electrical conductivity to the paper-based cathode and anode, commercially available eyeliner was coated onto paper (which acts as conductive ink) without any binder. Team Electrodes conducted rigorous experiments and showed that the presence of amorphous carbon (from soot) is responsible for its conductivity. With an instant start-up, the as-fabricated device generates bioelectricity as soon as the wastewater is injected. The facile process delineated here can be employed for the tailored electrode fabrication of various flexible energy harnessing devices. Several devices can be multiplexed in order to harness substantial power to drive various applications.
Team Electrodes first suggested the use of commercially available eyeliner as a novel alternative conductive ink for preparation of paper-based electrodes. The team’s findings show that simple conformal coating of eyeliner can make the paper surface conductive due to the presence of amorphous carbon present in it. This strategy has many advantages as both paper and eyeliner are readily available low-cost materials and electrode preparation does not require any additional chemicals, binders or tedious deposition methods. It is possible to control the loading and distribution of eyeliner depending on the deposition method.
Team Electrodes is convinced that this paper-based battery will find various useful applications in flexible electronics, energy textiles, paper-based sensors and fuel cells. Conductive patterns and tracks may be deposited on paper or textiles for flexible and wearable electronics by simply using an eyeliner instead of conductive inks. One can also tune the electrical and surface properties of this ink by adding certain nanoparticles, which might lead to further development of tailored electrodes on paper, depending on the application.
As a proof of concept, a microbial fuel cell has been fabricated on a paper platform using eyeliner coated papers as both anode and cathode. To start the device, a few microliters of bacterial culture were injected into the device. With an instant start up, the voltage of the device instantly shoots up to 750 mV, generating a power equivalent to 5 microwatts (μW). This can be easily disposed of by incineration and can function with any organic liquids such as urine. Stacking multiple devices can further boost the power and drive several practical applications. Hence, this device can function as a standalone power source for powering various devices in remote locations.
This novel paper battery can generate a few μW of electricity (adequate enough to power small electronic components), using wastewater. The paper battery comprises electrodes fabricated using an eyeliner and even urine can be used to generate power. The device, while leveraging capillary force, can uptake wastewater into itself and instantly generate electricity. It is compact, flexible and can be easily scaled up. This concept can be further extended to develop bioelectric toilets in future.