Leather has always had a built-in limit: its thickness is set by the animal it came from. Tanneries can split a hide into thinner layers, but below roughly half a millimetre the material loses its strength. That keeps leather out of products where every gram counts, such as lightweight car interiors, sportswear and watch straps. Most cultivated leather projects, which grow skin from animal cells instead of taking it from animals, have tried to match a conventional hide. A new filing from a Newcastle team heads the other way, using cell culture to make leather thinner than any animal can provide.
Leather Built One Cell Sheet at a Time
The application (WO2026201762A2) starts with fibroblasts, the skin cells that produce collagen, the protein that gives leather its strength. On a culture plate, these cells release collagen in an early, dissolved form, and much of it is lost each time the nutrient broth is replaced.
To keep it, the inventors add macromolecular crowding agents to the broth, such as Ficoll and carrageenan, a seaweed extract used to thicken foods. These large, inert molecules take up much of the liquid's volume. Like a packed room that forces people closer together, the crowding brings the dissolved collagen into contact with the enzymes that process it. The collagen then turns into solid fibres faster and settles around the cells. After about four weeks, each dish holds a dense sheet of cells wrapped in their own collagen.
That density matters for a second reason. Fibroblasts act like tiny muscles, tugging on the material around them, and the serum often used to feed cells encourages this. Sheets grown with serum tend to shrink when lifted off the dish, so producers often clamp them into frames. The serum-free sheets in this filing shrank by less than 1%, compared with 6.5% with serum, so no frames are needed.
Next comes stacking. The sheets are piled on top of each other and grown for another week, during which the cells bind neighbouring layers together with fresh collagen. A short treatment with riboflavin (vitamin B2) and UV light adds extra links between the fibres.
As shown in Figure 1, the fused stacks are robust enough to be lifted from the dish and stretched by hand without coming apart.
Figure 1. Stacked and fused sheets of cultivated skin tissue before tanning, showing a 50-layer stack in its culture dish (a), a 25-layer stack being lifted from the dish (b), and the fused material holding together when stretched by hand (c). Scale bars: 2 cm. Developed by 3D Bio-Tissues. Reproduced from the original patent figure (WO2026201762A2).
Finally, the stack goes through the same chrome or vegetable tanning used for animal hides, which locks the collagen in place and stops it from rotting. No plastic scaffold, filler or glue is used at any stage.
Thickness comes down to counting sheets. Twelve layers produced leather 0.045 mm thick, thinner than most human hairs, while twenty-five produced 0.109 mm. The natural leather tested alongside it measured 0.765 mm. The temperature at which leather starts to shrink is a standard measure of how well it has been tanned. The chrome-tanned cultivated leather held out until above 100°C, at the top of the range for natural leather. The thicker sample also passed the strength benchmark used for watch straps.
These results come from a horse skin cell line and small samples, and each sheet takes about four weeks to grow before stacking. How quickly and cheaply the process can scale remains the open question.
From Eye Tissue to Car Interiors
3D Bio-Tissues began as a Newcastle University spin-out engineering complex human tissues such as the cornea, the clear front layer of the eye. Now owned by London-listed BSF Enterprise, it sells City-Mix, a serum-free supplement that helps cells grow for cultivated meat and leather. Its leather work runs through sister company Lab-Grown Leather Ltd. The group has already shown leather around 0.04 mm thick, and in August 2026 it signed a partnership targeting luxury car interiors and synthetic skin for robots. This filing sets out the method behind those plans.
Congratulations to the inventors: Ricardo Gouveia, Che Connon and Emily Telford, for showing how far below nature's limit leather can go.
About the Author
I'm Pieter Labuschagne, Head of Technology at Newform Foods, where I work across strategy, R&D, and partnerships. With a background in biotechnology, I'm drawn to new technologies, interesting problems, and the challenge of turning ideas into real-world solutions. I enjoy building things from the ground up and connecting with the people behind them. Based in Cape Town, usually somewhere between a laptop, a surfboard, and a guitar.
Lab Grown Technologies highlights meaningful innovations shaping the future of cellular agriculture and tissue engineering.
This article is based on publicly available information. Lab Grown Technologies is not affiliated with the inventors or organisations mentioned.