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Biological photovoltaic (BPV) cells are living solar panels capable of producing clean energy by extracting electrons from sunlight (in daytime) and stored carbon in microbial cells (during the night or on cloudy days), irrespective of the organic substrate supply. The physicochemical properties of anode surfaces harbouring microbial communities in BPV systems influence the electrochemical charge transfer rate at the electrode. Hence, these properties play a significant role in regulating the kinetics of metabolic reactions in the biotic compartment while providing an electron transfer path. Various electrically conductive materials have been explored as solid-state anodes to improve the power output and economic viability of BPV systems. However, the current systems still suffer from low power density due to electrodes' electrochemical limitations and a lack of systematic optimization of the device. This review provides a comprehensive insight into the recent developments in different anode materials, their dimensional structure, and their impact on the performance of BPV systems in the last two decades. Moreover, the existing limitations of electrode materials in BPV systems are summarized, and outlooks for future anode advancements are foreseen.

Inkjet printing of metal nanoparticles (MNPs) allows for design flexibility, rapid processing and enables 3D printing of functional electronic devices through co-deposition of multiple materials. However, the performance of printed devices, especially their conductivity, is lower than those made by traditional manufacturing methods and is previously not fully understood. Here, we revealed that anisotropic electrical conductivity of printed MNPs is caused by organic residuals from MNPs inks. We employed a combination of electrical resistivity tests, morphological analysis and novel 3D nanoscale chemical analysis of printed devices using silver nanoparticles (AgNPs) to show that the polymer stabiliser polyvinylpyrrolidone (PVP) tends to concentrate between vertically stacked AgNPs layers as well as at dielectric/conductive interfaces. The understanding of organic residues behaviour in printed nanoparticles reveal potential new strategies to improve nanomaterial ink formulations for functional printed electronics.

Purpose This paper aims to print 3D structures from polymers that resist bacterial attachment by reactive jetting of acrylate monomers. Design/methodology/approach The first step towards printing was ink development. Inks were characterised to carry out an estimation of their potential printability using the Z parameter to predict stable jetting conditions. Printability conditions were optimised for each ink using a Dimatix DMP-2800, which enabled 3D structures to be fabricated. Findings UV photo-initiated polymers, which resist bacterial attachment, were found to be printable using piezo-based inkjet printers. The waveform required for each ink depends on the value of the Z parameter. Once the waveform and the printability parameters were optimised, 3D objects were fabricated. Research limitations/implications This methodology has been confirmed as an effective method to 3D print materials that have been demonstrated to be bacteria resistant. However, ink curing depends on modification of some parameters (such as photoinitiator concentration or UV exposure time) which would result in an improvement of the curing process post jetting. Social implications The combination of inkjet based 3D printing with new materials resistant to bacterial attachment means the possibility of building customised medical devices with a high level of complexity and bespoke features can be fully realised. The scope and variability of the devices produced will exceed what can be achieved using standard fabrication methodologies and can be applied to reduce the incidence of device associated infections and to address increased morbidity, mortality and health care costs associated with nosocomial infections. Originality/value In this paper, the novel use of materials that resist bacterial attachment has been described to build 3D structures using material jetting. Its value lies on the potential impact this methodology could produce in the biomedical device and research fields.