Scientists have developed a way to grow building materials using knitted moulds and the root network of fungi as a potential alternative to traditional building material. The composite, called mycocrete, can potentially reduce the environmental impact of the construction industry.

The paper, titled “BioKnit: development of mycelium paste for use with permanent textile formwork” documents research carried out by a team of designers, engineers and scientists in the Living Textiles Research Group, part of the Hub for Biotechnology, in Newcastle University’s Built Environment Department.

While researchers have experimented with similar composites before, the shape and growth constraints of the organic material have made it hard to develop diverse applications that fulfil its potential.

Using the knitted moulds as a flexible framework, or ‘formwork’, the scientists created mycocrete which is stronger and more versatile in terms of shape and form, allowing the scientists to grow lightweight and relatively eco-friendly construction materials.

“Our ambition is to transform the look, feel and wellbeing of architectural spaces using mycelium in combination with biobased materials such as wool, sawdust and cellulose,” says Newcastle University Academic Track (NUAcT) Fellow and corresponding author of the paper Dr Jane Scott.

Root Networks
To make composites using mycelium, part of the root network of fungi, scientists mix mycelium spores with grains they can feed on and material that they can grow on. This mixture is packed into a mould and placed in a dark, humid, and warm environment to allow the mycelium to grow, thus binding the substrate tightly together.

Once it has reached the required density, but before it starts to produce the fruiting bodies, or mushrooms, it is dried out. This process could provide a cheap, sustainable replacement for foam, timber and plastic.

However, mycelium requires oxygen to grow, which constrains the size and shape of conventional rigid moulds and limits current applications.

Oxygen-permeable knitted textile moulds offer a solution, as they could change from flexible to stiff, with the growth of the mycelium. To test this, Scott and her colleagues set out to design a mycelium mixture and a production system that could exploit the potential of knitted forms.

Scott explains that knitting is an incredibly versatile three-dimensional (3D) manufacturing system that is lightweight, flexible and formable.

“The major advantage of knitting technology compared to other textile processes is the ability to knit 3D structures and forms with no seams and no waste,” she elaborates.

Samples of conventional mycelium composite were prepared by the scientists as controls, and grown alongside samples of mycocrete, which also contained paper powder, paper fibre clumps, water, glycerine and xanthan gum.

This paste was designed to be delivered into the knitted formwork with an injection gun to improve packing consistency. The paste needed to be liquid enough for the delivery system while also holding its shape.

Tubes for the planned test structure were knitted from merino yarn, sterilised, and fixed to a rigid structure while filled with the paste to ensure that changes in tension of the fabric would not affect the performance of the mycocrete.

Building the Future
Once dried, samples were subjected to strength tests in tension, compression and flexion. The mycocrete samples proved to be stronger than the conventional mycelium composite samples and outperformed mycelium composites grown without knitted formwork.

Additionally, the porous knitted fabric of the formwork provided better oxygen availability and the samples grown in it shrank less than most mycelium composite materials do when they are dried. This suggests that more predictable and consistent manufacturing results could be achieved.

The team was also able to build a larger proof-of-concept prototype structure called BioKnit – a complex freestanding dome constructed in a single piece without joins that could prove to be weak points, owing to the flexible knitted form.

“The mechanical performance of the mycocrete used in combination with permanent knitted formwork is a significant result, and a step towards the use of mycelium and textile biohybrids within construction,” says Scott.

“In this paper we have specified particular yarns, substrates, and mycelium necessary to achieve a specific goal. However, there is extensive opportunity to adapt this formulation for different applications. Biofabricated architecture may require new machine technology to move textiles into the construction sector,” she concludes.