Bio-photovoltaic cells (BPVs) are a new photo-bio-electrochemical technology for harnessing solar energy using the photosynthetic activity of autotrophic organisms. Currently power outputs from BPVs are generally low and suffer from low efficiencies. However, a better understanding of the electrochemical interactions between the microbes and conductive materials will be likely to lead to increased power yields. In the current study, the fresh-water, filamentous cyanobacterium Pseudanabaena limnetica (also known as Oscillatoria limnetica) was investigated for exoelectrogenic activity. Biofilms of P. limnetica showed a significant photo response during light-dark cycling in BPVs under mediatorless conditions. A multi-channel BPV device was developed to compare quantitatively the performance of photosynthetic biofilms of this species using a variety of different anodic conductive materials: indium tin oxide-coated polyethylene terephthalate (ITO), stainless steel (SS), glass coated with a conductive polymer (PANI), and carbon paper (CP). Although biofilm growth rates were generally comparable on all materials tested, the amplitude of the photo response and achievable maximum power outputs were significantly different. ITO and SS demonstrated the largest photo responses, whereas CP showed the lowest power outputs under both light and dark conditions. Furthermore, differences in the ratios of light : dark power outputs indicated that the electrochemical interactions between photosynthetic microbes and the anode may differ under light and dark conditions depending on the anodic material used. Comparisons between BPV performances and material characteristics revealed that surface roughness and surface energy, particularly the ratio of non-polar to polar interactions (the CQ ratio), may be more important than available surface area in determining biocompatibility and maximum power outputs in microbial electrochemical systems. Notably, CP was readily outperformed by all other conductive materials tested, indicating that carbon may not be an optimal substrate for microbial fuel cell operation.

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Extended or repeated heating of food fats promotes polymerisation reactions that produce difficult-to-remove soil layers. Cleaning of these baked-on/burnt-on fat deposits was investigated using model layers generated by baking lard on 316 stainless steel discs. Rigorous characterisation of the layer material was difficult, as it was insoluble in most solvents. Cleaning was studied using the scanning fluid dynamic gauging technique developed by Gordon et al. (Meas Sci Technol 21:85–103, 2010), which provides non-contact in situ measurement of layer thickness at several sites on a sample in real time. Tests at 50 C with alkali (sodium hydroxide, pH 10.4–11) and three surfactant solutions indicated two removal mechanisms, related to the (1) roll-up and (2) dispersion mechanisms reported for oily oils, namely (1) penetration of solvent at the soil–liquid interface, resulting in detachment of the soil layer as a coherent film, observed with linear alkylbenzene sulfonic acid (LAS) and Triton X-100 and aqueous sodium hydroxide at pH 10.4–11; and (2) the breakdown promoted by the agent penetrating through the layer, observed with cetyl trimethyl ammonium bromide (CTAB), in which CTAB antagonised the cleaning action of LAS.