Toward Energetically Autonomous Foraging Soft Robots

© 2016, Mary Ann Liebert, Inc. A significant goal of robotics is to develop autonomous machines, capable of independent and collective operation free from human assistance. To operate with complete autonomy robots must be capable of independent movement and total energy self-sufficiency. We present the design of a soft robotic mouth and artificial stomach for aquatic robots that will allow them to feed on biomatter in their surrounding environment. The robot is powered by electrical energy generated through bacterial respiration within a microbial fuel cell (MFC) stomach, and harvested using state-of-the-art voltage step-up electronics. Through innovative exploitation of compliant, biomimetic actuation, the soft robotic feeding mechanism enables the connection of multiple MFC stomachs in series configuration in an aquatic environment, previously a significant challenge. We investigate how a similar soft robotic feeding mechanism could be driven by electroactive polymer artificial muscles from the same bioenergy supply. This work demonstrates the potential for energetically autonomous soft robotic artificial organisms and sets the stage for radically different future robots

From single MFC to cascade configuration: The relationship between size, hydraulic retention time and power density

© 2016 The Authors. Achieving useful electrical power production with the MFC technology requires a plurality of units. Therefore, the main objective of much of the MFC research is to increase the power density of each unit. Collectives of MFCs will inherently include units grouped in cascades, whereby the outflow of one is the inflow to the next unit; such an approach allows for better fuel utilisation. However, such a configuration is subject to some important considerations, including: the size of the MFCs; the number of units i.e. the length of the cascade; hydraulic retention time; fuel quality; and optimisation of anode surface and microbial colonisation. In the present study, optimisation of the aforementioned aspects has been investigated in order to establish the most appropriate cascade design. Results demonstrate that an increased flow rate of treated urine achieved equal power density with the same setup when fed with fresh urine at a lower flow rate. The independent investigations of these parameters have led to the design of a cascade that maintains uniformity with regard to the aforementioned parameters, by incorporating units of decreasing size, thus allowing locally shorter hydraulic retention times and therefore leading to increased power density levels

Evaluation of the PCB-embedding technology for a 3.3 kW converter

International audienceThis paper presents a converter fully made using PCB embedding technology (including the semiconductor devices , but also their gate driver circuits as well as the passive components). This converter is rated at a high-power (3.3 kW) considering the PCB technology. Here, the focus is given to the experimental validation of the embedding process, with the characterization of many of the embedded devices (SiC MOS-FETs, diodes, capacitors). These results show that most of the components were unaffected by the process, with the noticeable exception of the large inductors which exhibit variations in the inductance values as well as a large ac resistance. Finally, the converter is successfully assembled an tested at low power

Thermal Considerations of a Power Converter with Components Embedded in Printed Circuit Boards

International audiencePrinted-Circuit-Board (PCB) technology is attractive for power electronic systems as it offers a low manufacturing cost for mass production. Integration technologies such as device embedding have been developed to take advantage of the inter-layer space in multi-layer PCBs and to increase the performances (Electrical, Thermal). However, the PCB technology offers limited power dissipation due to the low thermal conductivity (≈0.3 W/(m·K)) of its composite substrate. In this paper, we consider PCB embedding for a 3.3 kW AC/DC bidirectional converter. We describe the integration of not only the power dies, but also the gate drive circuits and the power inductor, with a special focus on the thermal management. The manufacturing processes of the boards are presented. Two thermal models based on finite elements (FE) of this converter stage are introduced. The accuracy of these models is validated against experiments. The results show that a simplified FE model offers satisfying accuracy and fast simulation, even considering the relatively complex structure and layout of the PCBs

The power of glove: Soft microbial fuel cell for low-power electronics

A novel, soft microbial fuel cell (MFC) has been constructed using the finger-piece of a standard laboratory natural rubber latex glove. The natural rubber serves as structural and proton exchange material whilst untreated carbon veil is used for the anode. A soft, conductive, synthetic latex cathode is developed that coats the outside of the glove. This inexpensive, lightweight reactor can without any external power supply, start up and energise a power management system (PMS), which steps-up the MFC output (0.06-0.17 V) to practical levels for operating electronic devices (>3 V). The MFC is able to operate for up to 4 days on just 2 mL of feedstock (synthetic tryptone yeast extract) without any cathode hydration. The MFC responds immediately to changes in fuel-type when the introduction of urine accelerates the cycling times (35 vs. 50 min for charge/discharge) of the MFC and PMS. Following starvation periods of up to 60 h at 0 mV the MFC is able to cold start the PMS simply with the addition of 2 mL fresh feedstock. These findings demonstrate that cheap MFCs can be developed as sole power sources and in conjunction with advancements in ultra-low power electronics, can practically operate small electrical devices.© 2013 Elsevier B.V. All rights reserved

Response of ceramic microbial fuel cells to direct anodic airflow and novel hydrogel cathodes

© 2019 The Authors The presence of air in the anode chamber of microbial fuel cells (MFCs)might be unavoidable in some applications. This study purposely exposed the anodic biofilm to air for sustained cycles using ceramic cylindrical MFCs. A method for improving oxygen uptake at the cathode by utilising hydrogel was also trialled. MFCs only dropped by 2 mV in response to the influx of air. At higher air-flow rates (up to 1.1 L/h)after 43–45 h, power did eventually decrease because chemical oxygen demand (COD)was being consumed (up to 96% reduction), but recovered immediately with fresh feedstock, highlighting no permanent damage to the biofilm. Two months after the application of hydrogel to the cathode chamber, MFC power increased 182%, due to better contact between cathode and ceramic surface. The results suggest a novel way of improving MFC performance using hydrogels, and demonstrates the robustness of the electro-active biofilm both during and following exposure to air

Microalgae as substrate in low cost terracotta-based microbial fuel cells: Novel application of the catholyte produced

© 2016 Elsevier Ltd. In this work, the by-product generated during the operation of cylindrical MFCs, made out of terracotta material, is investigated as a feasible means of degrading live microalgae for the first time. In addition to the low cost materials of this design, the reuse of the solution produced in the cathode renders the technology truly green and capable of generating bioenergy. In this study, the effect of a light/dark cycle or dark conditions only on the digestion of live microalgae with the catholyte is investigated. The results show that a combination of light/dark improves degradation and allows algae to be used as substrate in the anode. The addition of 12.5 mL of a 1:1 mix of catholyte and microalgae (pre-digested over 5 days under light/dark) to the anode, increases the power generation from 7 μW to 44 μW once all the organic matter in the anode had been depleted

Urine-activated origami microbial fuel cells to signal proof of life

© The Royal Society of Chemistry 2015. The adaptability and practicality of microbial fuel cells (MFCs) are highly desirable traits in the search for alternative sources of energy. An innovative application for the technology could be to power portable emergency locator transmitters (ELTs). Such devices would ideally need to be lightweight, robust and fast-in terms of response. Urine is an abundant resource, and with MFCs, could be the ideal fuel for powering ELTs, with the compelling advantage of also indicating proof of life. We developed novel origami tetrahedron MFCs (TP-MPFCs) using photocopier paper to test different urine-based inoculants. When inoculated with urine extracted from the anode chambers of working MFCs a stack of 6 abiotic MFCs produced a usable working voltage after just 3 h 15 min; enough to energise a power management system. The anodes of established TP-MFCs were then removed and air-dried for 7 days before being inserted into new paper reactors and refrigerated. After 4 weeks, these MFCs displayed an immediate response to fresh urine and achieved a functional working voltage in just 35 minutes. Two paper MFCs connected in parallel were able to transmit 85 radio signals and in a series configuration 238 broadcasts over 24 hours. These findings demonstrate that simple, inexpensive, lightweight paper MFCs can be employed as urine-activated, "proof of life" reporting systems. This journal i

Intermittent load implementation in microbial fuel cells improves power performance

© 2014 Elsevier Ltd. This study reports on the response of small-scale MFCs to intermittent loading, in terms of power output over time. The aim was to understand the evolution with time of power output under different duty cycles, in conditions close to practical implementation. Inexpensive ceramic membranes were compared to cation exchange membranes, under continuous flow and with a pre-digester connected. Results show that at the minute-scale, all the duty cycles investigated, produced 78% higher power bursts from the MFCs (500. μW) than when under continuous loading (280. μW). These results were recorded from MFCs employing ceramic membranes, whereas the difference in performance for MFCs employing commercially available cation-exchange-membranes was insignificant. When normalising to daily energy production, only specific duty cycles produced more power than continuous loading. Furthermore, the introduction of a pre-digester increased the MFC power outputs 10-fold, thus confirming that separating fermentation from electro-active respiration, significantly enhances the system performance

3D printed components of microbial fuel cells: Towards monolithic microbial fuel cell fabrication using additive layer manufacturing

© 2016 The Authors For practical applications of the MFC technology, the design as well as the processes of manufacturing and assembly, should be optimised for the specific target use. Another burgeoning technology, additive manufacturing (3D printing), can contribute significantly to this approach by offering a high degree of design freedom. In this study, we investigated the use of commercially available 3D printable polymer materials as the MFC membrane and anode. The best performing membrane material, Gel-Lay, produced a maximum power of 240 ± 11 μW, which was 1.4-fold higher than the control CEM with PMAX of 177 ± 29 μW. Peak power values of Gel-Lay (133.8–184.6 μW) during fed-batch cycles were also higher than the control (133.4–160.5 μW). In terms of material cost, the tested membranes were slightly higher than the control CEM, primarily due to the small purchased quantity. Finally, the first 3D printable polymer anode, a conductive PLA material, showed significant potential as a low-cost and easy to fabricate MFC anode, producing a stable level of power output, despite poor conductivity and relatively small surface area per unit volume. These results demonstrate the practicality of monolithic MFC fabrication with individually optimised components at relatively low cost