Optofluidics is a relatively new interdisciplinary technology that combines optics and fluidics, in other words, any system or device that mixes light and liquids.
When you combine microfluidics -- the microscopic delivery of fluids through extremely small channels or tubes -- with optics, you can deliver both simultaneously with microscopic precision. This capability has given rise to new applications, such as lab-on-a-chip.
Now, optofluidics is poised to take on one of the greatest challenges of our time: energy.
Demetri Psaltis, Dean of EPFL's (Ecole Polytechnique Fédérale de Lausanne) School of Engineering, and a pioneer in the field, recently published a co-authored paper in Nature Phontonics that lays out how optofluidics technology can be used in a novel solar energy system and other sunlight-based fuel production systems.
"By directing the light and concentrating where it can be most efficiently used, we could greatly increase the efficiency of already existing energy producing systems, such as biofuel reactors and solar cells, as well as innovate entirely new forms of energy production," Psaltis explains.
Credit: EPFL / Greg Pasche
To get a sense of how a system that wraps nanotechnology, optics and bioreactors into a solar energy system, consider the image on the left. Imagine sunlight shining on the roof of a building installed with an optofluidic solar lighting system. The sunlight is first captured by a light-concentrating system that follows the sun's path by changing the angle of the water's refraction. The light is then directed onto a lens, which focuses it onto a optofluidic reactor where a chemical reaction takes place to produce methane, a biofuel. Doing this at the nanoscale is highly efficient because you create more surface area for interactions to occur between the chemicals, resulting in greater output and reduced cost. Adding a light source as a catalyst to the directed flow of individual molecules in nanotubes allows for extreme control and high efficiency.
By using sunlight to drive a microfluidic air filter or support an indoor solar panel is a novel way to use solar energy since the key components would be protected from the elements and, therefore, last longer, according to the researchers.
The EPFL team acknowledges technical challenges of such systems, including up-scaling optofluidics for practical applications. One idea they propose is to use optical fibers to transport sunlight into large indoor biofuel reactors with mass-produced nanotubes.
"The main challenge optofluidics faces in the energy field is to maintain the precision of nano and micro light and fluid manipulation while creating industrial sized installations large enough to satisfy the population's energy demand," explains David Erickson, professor at Cornell University and visiting professor at EPFL. "Much like a super computer is built out of small elements, up-scaling optofluidic technology would follow a similar model -- the integration of many liquid chips to create a super-reactor."