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Microbial fuel cells (MFCs) are clean, renewable energy sources and they generate self-sustaining clean energy through cellular respiration. MFCs do not require any external energy to operate and do not emit any excess greenhouse gases. MFCs can also be used for bioremediation by removing toxic materials by respiring a variety of metals and other harmful elements including iron and uranium. In this article, we have discussed the principles and designs of biofuel cells. 

Cellular respiration is the process by which organic matter oxidizes, and the energy stored in the chemical bonds of the food releases. Normally, cellular respiration occurs inside the mitochondria of cells; however, a unique type of bacteria releases electrons externally. These specialized organisms are called electrogenic bacteria. Our goal is to construct a microbial fuel cell (MFC) with electrogenic bacteria, harvest the external electrons created by cellular respiration, and channel them through an external circuit to generate electricity. Mud soil, which has a high number of electrogenic bacteria in the environment, was used to construct an MFC. In the presence of gram-negative bacteria, which exist in both aerobic and anaerobic conditions, the constructed MFC delivered electrical energy to an external circuit. The MFC can generate electricity, and thereby power, from biodegradable substances and organic wastes found in the environment and landfills. They can also be used to power small devices and sensors used in day-to-day activities. To determine the effect of sugar on the growth and development of bacteria present in the MFC, the quantity of sugar administered will be monitored in relation to the power generated per day. 

Dye sensitized solar cells are a type of thin film solar cell used to convert sunlight into electrical energy. These devices use a different mechanism than conventional solar cells and can be made from materials which are biocompatible and biodegradable. The simplicity of design and small environmental impact of these devices make them a likely candidate for replacing conventional PV devices. Since these solar cells are thin film cells, they can be made to be transparent and can be printed on flexible substrate, allowing their incorporation into many household objects such as windows, backpacks, walls, and other objects which would otherwise not be used for energy generation. A wide variety of fabrication techniques and device designs exist for DSSCs, each having its benefits and deficiencies; it is the purpose of this paper to evaluate some of these design variations, including different semiconductor and dye types and scaffolds, as well as semiconductor surface treatment. 

In this paper we report a unique electrical response of ethanol-adsorbed ZnO films subjected to a constant potential difference. Current measurements were obtained in both dark and illuminated conditions. A significant delay in achieving saturation current was observed indicating a nonlinear and time varying effective resistance; a time-dependent equation describing this behavior was developed, allowing the calculation of a time constant for the transition regime. To determine the role of the surface properties in this behavior, microwave plasma was used to etch the ZnO film by varying degrees, resulting in an enhancement of the resistance switching for extended etching times. 

Dye sensitized solar cells are a type of thin film solar cell used to convert sunlight into electrical energy. These devices use a different mechanism than conventional solar cells and can be made from materials which are biocompatible and biodegradable. The simplicity of design and small environmental impact of these devices make them a likely candidate for replacing conventional PV devices. Since these solar cells are thin film cells, they can be made to be transparent and can be printed on flexible substrate, allowing their incorporation into many household objects such as windows, backpacks, walls, and other objects which would otherwise not be used for energy generation. A wide variety of fabrication techniques and device designs exist for DSSCs, each having its benefits and deficiencies; it is the purpose of this paper to evaluate some of these design variations, including different semiconductor and dye types and scaffolds, as well as semiconductor surface treatment using microwave plasma.