Physarum wires: Self-growing self-repairing smart wires made from slime mould (1309.3583v1)

Abstract: We report experimental laboratory studies on developing conductive pathways, or wires, using protoplasmic tubes of plasmodium of acellular slime mould Physarum polycephalum. Given two pins to be connected by a wire, we place a piece of slime mould on one pin and an attractant on another pin. Physarum propagates towards the attract and thus connects the pins with a protoplasmic tube. A protoplasmic tube is conductive, can survive substantial over-voltage and can be used to transfer electrical current to lightning and actuating devices. In experiments we show how to route Physarum wires with chemoattractants and electrical fields. We demonstrate that Physarum wire can be grown on almost bare breadboards and on top of electronic circuits. The Physarum wires can be insulated with a silicon oil without loss of functionality. We show that a Physarum wire self-heals: end of a cut wire merge together and restore the conductive pathway in several hours after being cut. Results presented will be used in future designs of self-growing wetware circuits and devices, and integration of slime mould electronics into unconventional bio-hybrid systems.

• The paper demonstrates that protoplasmic tubes of *Physarum polycephalum* can serve as self-growing, self-repairing conductive pathways, termed "Physarum wires," exhibiting resistivity values between 80 Ω·cm and 2560 Ω·cm.
• A significant finding is the self-repair mechanism, where cut Physarum wires can restore connectivity within 6-9 hours by regrowth and merging of cytoplasmic extensions, confirmed by electrical measurements.
• Developing Physarum wires has implications for novel computing architectures by introducing dynamism through self-maintenance and adaptability, potentially leading to more sustainable bio-electronic systems through future mineralization or hybridization.

Physarum Wires: Self-Growing, Self-Repairing Conductive Pathways

The paper "Physarum Wires: Self-Growing Self-Repairing Smart Wires Made from Slime Mould" by Andrew Adamatzky investigates the development of unconventional computing circuits using biological materials. Specifically, the paper focuses on leveraging the protoplasmic tubes of the slime mould Physarum polycephalum as conductive pathways, which the paper aptly terms "Physarum wires." This research is positioned within the broader scope of bio-electronics and unconventional computing, suggesting a novel direction for circuit design and functionality.

Experimental Findings

The experimental setup involves placing Physarum polycephalum on a substrate to connect two electronic components or 'pins' by creating a conductive path between them. The slime mould propagates towards an attractant placed near the destination pin, forming a tube that serves as the conductive medium. A notable finding is the tube's capability to conduct electricity, even under significant electrical loads, without structural damage. The paper reports resistivity values between 80 Ω·cm to 2560 Ω·cm, closely paralleling those observed in biological tissues.

Routing the Physarum connections is achieved via chemical attractants, repellents, and even electromagnetic fields, demonstrating adaptability across varying substrates, including electronic circuit boards. The ability to "grow" on circuits without significant substrate modifications highlights the potential for direct integration into existing electronic infrastructure.

Self-Repair Mechanism

One of the most significant observations is the self-repair capacity of Physarum wires. Upon being cut, the protoplasmic tubes effectively restore connectivity at points of damage. This self-healing capability is facilitated by the growth and eventual merger of cytoplasmic extensions from the cut ends, re-establishing the conductive path within 6-9 hours post-damage. This observation is supported by electrical measurements that confirm the restoration of conductivity to nearly original values.

Implications and Future Directions

From a theoretical standpoint, the development of Physarum wires could revisit fundamental assumptions about computing architecture. The self-growing and self-repairing properties introduce an element of dynamism not present in current electronic systems. Practically, integrating such biological components into electronic devices could accommodate novel self-maintenance functionalities and adaptable circuit evolutions over time.

Future research could explore the longevity and reliability of such systems, particularly the maintenance of stability amidst environmental variations. An additional avenue of exploration is the mineralization of these biological wires, which could enable the creation of permanent conductive paths, mitigating some of the volatility inherent in living systems.

The application of external substances, such as metallic particles, could further enhance the conductive properties and longevity of these bio-wires, potentially leading to hybrid systems combining the adaptability of biological systems with the stability of conventional electronics.

Conclusion

This paper presents a compelling case for Physarum polycephalum as a viable medium for developing self-healing, self-growing conductive pathways within electronic circuits. The research highlights the potential for integrating biological materials into computational systems, opening opportunities for more sustainable, adaptable computing technologies. However, this entails overcoming the inherent challenges of integrating these systems within the rapidly evolving landscape of technology. As this line of inquiry progresses, it marks a significant contribution to the field of unconventional computing and bio-electronics.