We developed a cell-free artificial platform conducting both light and dark reactions. To the best of our knowledge, such a device had not been reported so far. This device was able to harvest light energy and transform the energy to organic compounds, mimicking a plant leaf. We envision integrating the “artificial leaves” to create a compact energy harvesting system with a promising efficiency.

Photosynthesis consists of two parts: light reaction and dark reaction. During the light reaction, light energy is transformed to chemical energy in adenosine triphosphate (ATP) that is a biological energy source, while during the dark reaction. Carbon dioxide is absorbed and used to synthesize organic compounds such as glucose and fructose. Many scientists had tried to realize artificial photosynthesis for energy harvesting for decades [1]. However, most of the previous systems were simply based on light reaction and produced less desirable energy sources, such as explosive hydrogen gas and unstable electricity [2,3]. Other works had been reported that combined both light and dark reactions to produce useful organic compounds, but they were all based on utilizing living cells that were difficult to maintain and were not reusable [4,5].

In order to create an artificial photosynthesis device, we had come up with three specific parts as follows.

Part 1: Light reaction was realized in a microfluidic platform that consists of two fluid chambers separated by a planar membrane with embedded proteins that convert light energy into ATP. The devices were fabricated in cleanroom by silicon KOH cavity etching and glass buffered oxidize etchant (BOE) etching, followed by gold electrode deposition. PDMS fluidic cavities were made by soft-lithography with a 3D printed mold. Four different materials were investigated as potential membrane materials and the optimal (most stable) material was identified through impedance spectroscopy. Once the best membrane material was identified and a microfluidic platform was constructed, we had light-converting proteins bacteriorhodopsin and ATP synthase embedded in the membrane followed by the evaluation its light reaction performance.

Part 2: Dark reaction was realized in another microfluidic platform porous PDMS cubes as gas-liquid interface media. We used porous PDMS as a gas-liquid interface between microfluidic channels to create a “one-way” diffusion path for CO₂. Successful CO₂ transport produced precursors (C3 compounds) for glucose production.

Part 3: The circuits for an integrated light reaction platform was designed and assembled on PCB. The digital encode/decode of microchip array was achieved by impedance analyzer with digital circuit. A high-resolution, low-speed analog-to-digital converter with comparator and OTA  was also designed and simulated for ion channel monitoring purpose.

First, electrochemical property database of planar membranes made of different biomaterials were established. We found polarized lipid fraction E (PLFE) as the best membrane materials to carry biochemical reactions in cell-free environment. Second, a novel gas-liquid interface was developed for microfluidic platforms using porous PDMS and its performance was thoroughly investigated by on-chip pH measurement. This novel cell-free photosynthesis system can achieve a glucose production about  5.56±0.17μg/mL.

This research brought together expertise in MEMS, biochemistry and biomaterials, and system control and integration with mixed-mode VLSI. We envisioned integrating the “artificial leaves” to create a compact energy harvesting system with high efficiency.

References

[1] S.C. Roy, et al. ACS Nano, 2010, 4(3), pp.1259-1278.

[2] D. Gust, et al. Accounts of Chemical Research, 2009, 42(12), pp.1890-1898.

[3] Y. Tachibana, et al. Nature Photonics, 2012, 6(8), pp.511-518.

[4] D. Wendell, et al. Nano Letters, 2010, 10(9), pp.3231-3236.

[5] J. SeokaLee, et al. Lab on a Chip, 2011, 11(14), pp.2309-2311.

Last Modified: 10/05/2016
Modified by: Jack Zhou