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Introduction

Energy (obtained from food through enzymatic reactions) is the basis of human movement. Enzymes are special proteins that facilitate chemical reactions inside our bodies. Sony's Bio Battery uses this same principle to produce electric energy. It is an extremely safe form of energy production since the fuel (glucose) is a carbohydrate just like bread or rice. Because glucose is a clean energy source---produced by plants through photosynthesis (a process that involves the absorption of CO2) ---Bio Battery is also an eco-battery. Sony commenced Bio Battery R&D in 2001.

Technical Challenges of Bio-Fuel Cells

Bio-fuel cells are attracting increased attention mainly due to promising advances from the research laboratories around the world resolved before bio-fuel cells become commercially viable for practical applications. The main challenges are: (1) Nanostructured bioelectrocatalysis. (2) Immobilization of bioelectrocatalysts. (3) Protein denaturation induced by CNT.

Bio battery seminar topics


The Mechanism Behind Bio Battery

Like a conventional fuel cell battery, Bio Battery basically consists of an anode, cathode, electrolyte and separator. However, Bio Battery has certain specific characteristics. First, biological enzymes are used as catalysts for the anode and cathode. Second, enzymes and electronic mediators (which transfer electrons between enzymes, and between enzymes and electrodes) are fixed on the anode and cathode.

Nanostructured Bioelectrocatalysis

Traditional direct hydrogen fuel cells require noble metal catalysts both for hydrogen oxidation and oxygen reduction.17 Similarly, the bio-fuel cells also need catalysts (bio-catalysts) for the conversion of chemical to electrical energy. One approach is to use microorganisms and/or enzymes as biological reactors for the fermentation of raw materials to fuel products (similar hydrogen fuel reform- ers); the second approach is to use the microorganisms and/or enzymes as catalysts directly in the bio-fuel cells. The second approach, using purified redox enzymes for the targeted oxidation and reduction of specific fuel and oxidizer substrates, is more efficient for bio-fuel cells. Also, bio-catalysts are an attractive renewable and less expensive alternative to transition metal catalysts for mediated electron transfer (MET).18 MET-type bioelectrocatalyt based BFCs offer the cur- rent density advantage over the direct electron transfer (DET) type, but require that mediators and enzymes be immobilized on electrode surfaces. The construction of DET-type bio-fuel cell is relatively simple as the sys- tem is free from several restrictions concerning mediators.

The cell would not require separators because the crossover of fuels (substrates) would not occur in principle due to enzymatic substrate specificity as long as the enzymes are immobilized on electrodes and dehydrogenases (that is, redox enzymes reacting with electron acceptors except dioxygen) are utilized as anode catalysts. Kamitaka’s group have reported a construction of sin- gle compartment bio-fuel cell, with no separators, using D-fructose dehydrogenase (FDH) from Gluconobacter sp. and laccase from Trametes sp. (TsLAC) as DET-type bio- electrocatalysts in the two-electron oxidation of D-fructose and four-electron reduction of oxygen in the anode and cathode, respectively.

Packaging Of Bio-Fuel Cells

One of the major challenges in bionanotechnology is merging new nanoscale fabrication tools with classical synthetic methods and delicate biomolecular building blocks to create materials with unique biomedical properties. In order to address the packaging requirement of the bio- fuel cells, it will be necessary to bridge the disciplines of biology, chemistry, materials science, semiconductor technology and engineering to find optimum packaging solutions for the challenges posed by these devices. Biological packaging can be defined as the sum total of the physical device, temperature regulating and monitoring systems, type of preservation solution, and storage protocol(s) necessary to maintain cells or tissues in a “state of suspended animation” during transport or storage.

The packaging issues connected with biological applications pose different set of challenges. The materials used in the medical device industry are extremely robust, and research shows that the failure rate is less than one in one million packages.43 To achieve the performance levels of this order, the reliability testing procedures for the devices has to be very stout, which is an added cost of the product. The big difference, however, between medical device packaging and other branches of the packaging industry is the role the regulators play. Primarily the medical device industry for the last 30 years has been shaped by the FDA which oversees all aspects of medical device packaging from material selection, design and manufacturing to label- ing and sterilization.

Conclusion

Bio-fuel cells are energy-conversion devises based on bio-electro catalysis leveraging on enzymes or microorganisms. Chemical reactions can proceed by direct electron transfer (DET), in which case the electron transfer occurs directly between enzymes and electrodes,5 or through shuttle mediated electron transfer (MET), in which electron transfer mediators shuttle the electron between enzymes and electrodes to reduce the kinetic barrier in the electron transfer between enzymes and electrodes. 

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