Upscaling through 3D Printing

Our experimental results with the first microfluidic biofuel cell chip prototype proved that a significant increase in power output is achieved if the distance between bacteria and the nearest electrode is miniaturized. The achieved power density was at least 4 times larger than with macroscale cells. 

However, the original prototype was functionally a 2D chip in the sense that there was just a single floor or level in that device. This was so done because the chip was assembled to have wiring on the substrate and the fluidics on top. Hence, to increase absolute power output, it would be necessary to make many such chips, and perhaps stack them together. 

The conceptual schematic above shows the expanded scheme of power station use and structure, wherein a power cube is made of stacked devices. It is also important to know the expected power level under reasonable assumptions for dimensions.

The above schematic shows the calculation, its assumptions, and its result. Our 2D chip demonstrated up to 100 mW/m2 power and 80 mW/m2 consistently. We can take that power density and multiply by 1 square meter, for this to be the floor area, producing 0.1W power per floor. Then if each layer or floor is about 100 microns tall, there would be 10,000 floors in that “building”. Hence, the overall power output would be 1 kW. This is significant amount of continuous power, generating 24 kWh per day. That would be enough to power a medium-sized TV or a microwave oven continuously. The respective volumetric power density would be 1 kW/m3 for the biofuel cell.

The above scheme is feasible from a physics perspective. However, to implement it in practice, tens of thousands of chips like our 2D prototype would be required. Fabricating them separately and then assembling them fluidically would be prohibitively expensive. Hence, while miniaturization makes sense conceptually and from the viewpoint of physics, it also must be implemented by some affordable means of upscaling and manufacture.

It turns out that 3D printing seems to offer exactly that required capability. It allows the many layers to be printed monolithically, on top of one another, as part of the same automated process. This allows for a much lower cost per unit volume of such devices, at least theoretically. Hence, this is the pathway to take in the arraying and upscaling of microfluidic biofuel cells. Ultimately, this requires the development of the techniques and methods of 3D-printed microfluidics.