Goals of the project
We characterize a graphene coating approach to improve the durability of electroflotation devices. Recently, the scientific community has made long strides to integrate graphene on electronic sensors and devices. However, it is important to understand how graphene materials can benefit other industries such as in the food and agricultural industries. Due to graphene’s high conductivity and impermeability to water and gases, graphene is an ideal candidate to replace current anode and cathode materials used in electroflotation devices. Current materials such as steel and iron are victim to degradation during the electrolysis process and must be replaced often. Carbon materials such as graphite rods have been used consistently in electroflotation devices to increase anode material lifetimes, however, are quite large and fail to produce the necessary bubble sizes needed to accurately filter algae particulates and bacteria such as E. coli. With a methodology for microfabricating graphene and its composites on electrodes, the scientific community can begin to realize the high current densities needed to achieve efficient electrogeneration of tiny bubbles in electroflotation systems.
Nature of the Collaboration
As a multidisciplinary project, both the biological and electrical engineering teams worked collaboratively to construct a prototype that generated small bubbles within a harsh aqueous environment. For example, the biological engineering team members researched the design specifications needed to generate small bubble sizes, filtration goals, etc. The engineering team then brainstormed, implemented, and tested various embodiments of the final device to see if the design fulfilled those requirements. Utilizing the expertise of both fields allowed design iterations to be executed quickly.
Multiple iterations of the current electroflotation device were made. During each step various equipment were used.
Optical engineering – used to construct an optical setup to laser ablate graphene structures
Design engineering – used PCB design software to construct various embodiments of graphene electrode structures.
Machining – used to fabricate various electrode molds in which aqueous graphene oxide could settle during laser ablation.
Coding – used to program Arduino to monitor voltage and currents of laser diode. Also coding was used to allow automatic control of a micro-positioning stage to move the laser diode with respect to an image file that contained the electrode design.
For the micro-scale devices, and optical setup was constructed with optical components such as lenses and mirrors. The use of laser diode was needed to laser ablate the graphene oxide and turn graphene oxide into graphene. In order to monitor the voltages and current to laser diode, the use of an Arduino was used to get real time measurements.
For the large-scale devices a laser engraver was used to irradiate large graphene electrodes. The use of the 3d printer was also used to construct small channels in which the aqueous graphene oxide could sit during laser ablation.
All designs were made in PCB fabrication software such as Eagle Cad.
When using the laser engraver, the design was made in Adobe Photoshop and imported to the laser engraver software.
The process for this project was iterative. Initial brainstorming was conducted to come up with an idea for robust electrode materials, followed by an initial brainstorm of the device requirements. Once the design requirements discussed, the device was fabricated using optical and rapid prototyping methods. During the fabrication stage new design requirements were explored that would change the design of the device, therefore, causing the researchers to discuss new alternatives to the final result. This allowed dynamic changes to the electrode design, furthermore, increasing the probability of success. During each step a group meetings were conducted that allowed the researchers to come up with new ideas and methods to reach a prototype goal.
Graphene was successfully used to generate micro-bubbles in an aqueous environment.
The findings were demonstrated and presented at the 2014 Asia Pacific resilience Innovation Summit & Expo.
Most importantly, both the engineering and biological engineering department gain a lasting relationship for future collaboration.
The major challenges for this project were utilizing graphene in multiple environments. For example, because graphene is 1 atom thick, understanding how to utilize the material was quite challenging and in water made research more difficult. However, resilience allowed us to explore multiple fabrication methods early on in the project to transfer graphene to the electrode substrates. We eventually decided on a method that was easy to implement, therefore, allowed us to work more on design and not the fabrication techniques.
Another challenge was understanding how to use various pieces of equipment such as lasers and 3d printers. Initially, development of the skillset and knowledge based needed to use these tools was difficult. However, with a little experience, we learned tricks on how to implement these devices quickly. Furthermore, the knowledge acquired allowed the researchers to use the equipment to tackle other problems such as interactive lighting and graphene sensors.
The current outcome to date is a functional prototype that can generate micro-bubbles and can be further tested in an electroflotation system.
Innovations, impact and successes
The major impact of graphene based electrodes for electroflotation systems will achieve accurate and rapid sensing of E. Coli and other bacteria in agricultural wash. Our methods are inexpensive and increase the lifetime of current commercial electrodes. The reduction in cost would allow more consumers to use such devices.