Propose the use of fungal mycelium skin for sustainable electronics
Researchers at the Johannes Kepler University in Linz, Austria have created a new type of biodegradable electronics they call MycelioTronics. And it has great potential to reduce the e-waste that plagues hardware of all kinds.
The new concept is based on cultivating and processing skins from a fungus as biodegradable substrate material for green electronics.
and is whate currently all electronic circuits, which are made of conductive metals, they must rest on an insulating and cooling base called a substrate. In almost all computer chips, this substrate is made of non-recyclable plastic polymers, which often discarded at end of useful life of a chip
This contributes to the 50 million tons of e-waste that is produced each year. The excellent thermal stability and electrically insulating nature of the feature network make mycelium skin a highly suitable biodegradable substrate for electronic circuitry.
“The substrate itself is the most difficult to recycle,” says Martin Kaltenbrunner of Johannes Kepler University in Linz, Germany. “It's also the most electronics and it's the lowest value, so if you have some chips that really have a lot of value, you might want to recycle them. »
Researchers have grown and processed fungal mycelium skins as an alternative biodegradable substrate material.
The "skin" is based on a fungus that grows naturally on dead hardwood in mild temperate climates. They have high thermal stability and a flexible shape, which allows the soldering of electronic components and facilitates the manufacture of electronic sensor boards. In addition, they can withstand more than 2000 bending cycles.
The mycelium can be used even in low consumption batteries. The researchers found that the mycelium batteries could power autonomous sensing devices, including a Bluetooth module and a proximity and humidity sensor. This is an important step for sustainability.
It is mentioned that the skin did not grow on the other mushrooms tested by the researchers. When they extracted and dried the skin, they found that it was flexible, a good insulator, it could withstand temperatures of more than 200 °C and it was about the thickness of a sheet of paper, good properties for a circuit substrate.
The skins allow the use of common electronic processing techniques, including physical vapor deposition and laser patterning, to obtain electronic traces with conductivity up to 9,75 ± 1,44 × 104 S cm-1. Mycelium's flexible, conforming electronic skins withstand over 2000 flex cycles and can be bent multiple times with a moderate increase in force. We demonstrate that mycelium batteries have capacities of up to ~3,8 mAh cm-2 that are used to power autonomous sensing devices, including a Bluetooth module and a proximity and humidity sensor.
If it is kept away from moisture and UV rays, the skin could probably last hundreds of years and therefore would be perfect for the life of an electronic device. It is important to note that also it can decompose in the soil in about two weeks, which makes it easily recyclable.
About the process, it is mentioned that integrated circuits (ICs) account for most of the total mass of printed circuit boards (PCBs), due to the high density of the metals used, but it is difficult to make biodegradable versions of them.
Conventional mobile phone printed circuit boards, for example, are composed of 63% by weight of metals, 24% by weight of ceramics and 13% by weight of polymers.
Regarding the design part, the following is mentioned:
(A) Photograph of a sensor board comprising a two-cell mycelium battery, a Bluetooth module, and an impedance sensor with an interdigital electrode structure.
(B) The impedance response of the sensor is highly dependent on the relative humidity of the environment.
(C) Adjusted capacity and resistance of the interdigital sensor structure as a function of frequency
(D) Block diagram of the sensor board generating and transferring data to an external PC during wireless experiments.
(E) A finger approaching the sensor produces clear changes in the capacitance of the sensor.
(F) Response of the sensor capacitance to the repeated approach of the fingers in (E)
(G) Suction on the sensor plate causes clearly detectable humidity changes.
(H) Response of capacitance to humidity changes in (G)
(I) Aerobic decomposition of MycelioTronic PCB substrates occurs within 2 weeks in composting soil.
(J) Mass percentage of decaying PCB substrate shown in (I) measured over 11 days
published work on biodegradable integrated circuits is based on biomass and plant materials, resulting in a completely transient electronic configuration that includes degradable circuit elements.
The researchers obtained cohesive metallic films on the harvested skins with a surface roughness Rrms of 7,5 ± 1,8 μm by physical deposition during vaporization, allowing for post-processing of the circuitry.
Subsequently, films with reproducible continuity are obtained by depositing 400 nm of copper as a conductive mass, with a predeposition of 3 nm of chromium for better adhesion. They further improve conductivity by depositing an additional 50 nm thick layer of gold on top of the initial layer of copper.
With these recent mushroom-based advances, biodegradable mycelium skins may emerge as a class of sustainable alternative materials for a green electronic future and provide further momentum towards sustainable batteries and electronics.
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