Abstract

Environmental sensing is important evolved functional aspect of multicellular organisms in nature. Detection of sound (both abiotic and biotic) in particular increases the survival rate (e.g. reflex or behaviour to move away from danger or communicate with family or similar friendly species) and/or aid in finding food. In a multicellular organism in nature; sound obtained by anatomical structures are processed by neurological pathways and finally perceived by cognitive processing. The living cells use electrical signalling to achieve this. Functionally, this process is the same in conventional electro-mechanical devices and in robotics; in which an electromechanical transducer converts the acoustic waves into an electrical signal.
Microbial fuel cells (MFC) enable the utilisation of microbial metabolism, consuming organic matter, as an engine of power generation providing building blocks for building artificial bio robotics. Traditionally used as power sources for energy autonomous robots (Ecobots), it is less known, that MFC can themselves be made into energy autonomous sensors. The ability to sense is due to the properties of the anodic biofilms which as a biological entity responds to the physicochemical conditions. MFCs have already been employed for measuring BOD and COD (the amount of organic carbon compounds in the feedstock). We have demonstrated the use of MFC in other aspects such as sensors that respond to physical parameters such as temperature. Modern small scale MFC are adequately power dense for driving its own output.
The long-term aim is to build complete energy autonomous artificial bio-robots, where many of the system functions such as power generation, sensing, actuation and processing; will be biological in form; both material and /or inspirational in nature.
In this work, we demonstrate specifically designed MFCs that operate in steady state under continuous feed conditions that can function as a far field sonic transducer (aka. A microphone) with the ability to detect sound from the environment. We demonstrate the implementation of sonotaxis similar to that of animals in nature. With these MFC sound sensors, we aim to enable increased functionality and bio-inspired behaviour for future bio-robotics.