Improved performance of carbon nanotubes embedded photomicrobial solar cell.

Enhancing the energy efficiency of power out is a key issue of microorganisms based energy harvesting. Here, we introduced carbon nanotubes (CNTs) into a photomicrobial solar cell (PMSC) system in order to increase the harvesting energy power. Microcystis aeruginosa was used as a solar energy converter, microorganism. It revealed that when a small amount of CNTs (e.g. 0.001 wt%) were added in the cyanobacterium suspension, the photocurrents were enhanced dramatically. The optical and electrical properties of the CNT suspension were analyzed. The biochemical features of the PMSC were evaluated under dark and light conditions. This study is expected to offer a strategic way for harvesting living cell-based solar energy in a more efficient manner.

Microfluidic Electrochemical Impedance Spectroscopy of Carbon Composite Nanofluids.

Understanding the internal structure of composite nanofluids is critical for controlling their properties and engineering advanced composite nanofluid systems for various applications. This goal can be made possible by precise analysis with the help of a systematic robust platform. Here, we demonstrate a microfluidic device that can control the orientation of carbon nanomaterials in a suspension by applying external fields and subsequently examine the electrochemical properties of the fluids at microscale. Composite nanofluids were prepared using carbon nanomaterials, and their rheological, thermal, electrical, and morphological characteristics were examined. The analysis revealed that microfluidic electrochemical impedance spectroscopy (EIS) in the device offered more reliable in-depth information regarding the change in the microstructure of carbon composite nanofluids than typical bulk measurements. Equivalent circuit modelling was performed based on the EIS results. Furthermore, the hydrodynamics and electrostatics of the microfluidic platform were numerically investigated. We anticipate that this microfluidic approach can serve as a new strategy for designing and analyzing composite nanofluids more efficiently.

Novel microbial photobioelectrochemical cell using an invasive ultramicroelectrode array and a microfluidic chamber.

OBJECTIVE: To fabricate a novel microbial photobioelectrochemical cell using silicon microfabrication techniques. RESULTS: High-density photosynthetic cells were immobilized in a microfluidic chamber, and ultra-microelectrodes in a microtip array were inserted into the cytosolic space of the cells to directly harvest photosynthetic electrons. In this way, the microbial photobioelectrochemical cell operated without the aid of electron mediators. Both short circuit current and open circuit voltage of the microbial photobioelectrochemical cell responded to light stimuli, and recorded as high as 250 pA and 45 mV, respectively. CONCLUSION: A microbial photobioelectrochemical cell was fabricated with potential use in next-generation photosynthesis-based solar cells and sensors.

Characterization of a single cell of Chlorella in a microfluidic channel using amperometric electrode arrays.

Electrochemical characteristics of O2 and/or mediators secreted by a single cell of Chlorella fusea were analyzed by using amperometric measurements on microelectrodes embedded in a microfluidic device. A single cell was trapped in a microfluidic channel, which simplifies the mass transfer phenomenon, i.e., one-dimensional distribution of solutes in the channel. Such amperometric measurements allowed us to obtain more refined data in a localized space and to understand photosynthetic behavior of algae at the single cell level. In addition, the concentration of a photosynthetic mediator, p-benzoquinone, was numerically calculated by using the finite element method.

Correlation between internal structure and electrochemical impedance spectroscopy of multiphase slurry systems.

Slurry for lithium-ion batteries is prepared from an active material, a carbon conductive additive, and a polymeric binder in a solvent, and its morphological change is evaluated over time using electrochemical impedance spectroscopy. A schematic model of the internal structure and dispersion states of the slurry components during 7 days of storage is proposed on the basis of the electrochemical impedance spectroscopy (EIS) measurement. The EIS results reveal that the conductive path constructed by the network structure of the slurry components breaks over time, which can be worsened by mechanical agitation. In order to confirm the morphological change, the slurry is freeze-dried and then prepared to fixate the locations of the slurry components. The existence of a network structure (or flocculation) is verified by morphological observations. In addition, the dispersity index and Micro-CT are introduced as new methods representing the dispersion state of the slurry components.

In vivo O2 measurement inside single photosynthetic cells.

The oxygen evolution of single cells was investigated using a nano-probe with an ultra-micro electrode (UME) in a submicron sized system in combination with a micro-fluidic system. A single cell was immobilized in the micro-fluidic system and a nano-probe was inserted into the cytosolic space of the single cell. Then, the UME was used for an in vivo amperometric experiment at a fixed potential and electrochemical impedance spectroscopy to detect oxygen evolution of the single cell under various light intensities.

Direct extraction of photosynthetic electrons from single algal cells by nanoprobing system.

There are numerous sources of bioenergy that are generated by photosynthetic processes, for example, lipids, alcohols, hydrogen, and polysaccharides. However, generally only a small fraction of solar energy absorbed by photosynthetic organisms is converted to a form of energy that can be readily exploited. To more efficiently use the solar energy harvested by photosynthetic organisms, we evaluated the feasibility of generating bioelectricity by directly extracting electrons from the photosynthetic electron transport chain before they are used to fix CO(2) into sugars and polysaccharides. From a living algal cell, Chlamydomonas reinhardtii, photosynthetic electrons (1.2 pA at 6000 mA/m(2)) were directly extracted without a mediator electron carrier by inserting a nanoelectrode into the algal chloroplast and applying an overvoltage. This result may represent an initial step in generating "high efficiency" bioelectricity by directly harvesting high energy photosynthetic electrons.