Imagine a future where living bacteria power our electronics, weave fibers, and revolutionize plastic. Scientists are exploring living materials made from biologically active organisms that can grow, repair, and interact dynamically with their environments. Among these, fungi stand out as nature’s recyclers, capable of colonizing a variety of surfaces such as decaying wood, plastic, and even rubber. These organisms develop robust root-like structures known as mycelium, creating materials that can self-clean and self-repair, even in complex shapes.
However, crafting living materials poses challenges, as traditional processing techniques often involve heat and chemicals that can harm or kill these organisms. Researchers must skillfully balance the processability of materials with the adaptive capabilities of living organisms. A team from the Swiss Federal Institute for Materials Science (Empa) and the Institute for Food, Nutrition and Health has innovated a technique to convert mycelium into a liquid mix of microfibers, referred to as fiber dispersion, enabling traditional processing methods while maintaining the living nature and functions of the fibers.
The team focused on rapidly growing white rot fungi, specifically the Schizophyllum commune H-48a strain, notable for its ability to secrete biochemicals that bind materials and form adhesives. Mycelium was cultivated from S. commune, kept in a nutrient-rich solution for 7 days at 30°C (86°F) with continuous agitation.
Growing these fungi in liquid media presents challenges due to their tendency to form intertwined clumps, resulting in weaker materials. To address this, researchers utilized a specialized mill with adjustable settings to break down these clumps into uniformly sized fibers, akin to the width of human hair. The resulting mixture, known as living fiber dispersion (LFD), was then redispersed in water.
Researchers experimented with LFDs to develop novel materials, including a substance that emulsifies incompatible phases like oil and water into stable mixtures, termed emulsions. This emulsifier ensures long-term stability, preventing separation over time. The team tested LFD as a biological emulsifier by mixing it with rapeseed oil at high speed, monitoring the stability of the resulting emulsion.
At concentrations of 1% and 2% LFD, the emulsions remained stable for over 25 days and withstood temperatures up to 80°C (176°F). In contrast, lower concentrations of 0.2% and 0.3% led to rapid separation. Moreover, allowing fungal growth in the emulsion for an additional 18 days resulted in further stabilizing biochemicals, slowing separation by up to four times. This suggests that LFDs could serve as low-energy, self-stabilizing emulsifiers, relevant for applications in food, cosmetics, and biomedicine—unlike traditional plant-based emulsifiers, which often require complex purification.
Researchers also created a thin film by drying the LFD in a Petri dish for three days. The densely packed fungal structure repels water and transmits light, distinguishing it from typical natural fiber-based materials. Mechanical tests showed that these LFD films could stretch up to 10 times beyond the capacity of conventional films. Remarkably, this behavior is moisture-dependent: at low humidity, the film remains rigid and brittle, while at high humidity, the rehydrated mycelium becomes as flexible as plastic. This moisture-induced change acts as a functional switch, allowing the film to shift between brittle and flexible states based on environmental conditions.
In their final experiments, the team assessed whether LFD films could act as smart materials, observing the material’s ability to bend up to 90° within five seconds when humidity changes. This adaptability surpasses that of comparable plant-based materials. Furthermore, when multiple LFD films interacted side by side, new fiber bridges formed in alignment with adjacent films, creating patterns spontaneously. Since these fungi can naturally colonize and degrade various materials, LFD systems are inherently recyclable, promoting material return to nature.
The researchers concluded that mycelium-based LFD technology has significant potential for applications in biodegradable electronics, textiles, packaging, and soft robotics. They also proposed that genetic engineering might enable fungi to degrade an even broader range of plastics and materials, thereby enhancing recycling efforts and expanding the scope of sustainable, multifunctional bio-based materials.
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Source: sciworthy.com
