fëllig: A shoe for every child
A material and process study on the additive manufacturing of children's shoes.
How can children's shoes be produced in a resource-efficient, local, and adaptable way? fëllig explores the combination of natural materials, digital manufacturing, and circularity. In this project, biological growth processes merge with parametric design to create a modular system that responds to the needs of growing children's feet while radically reducing material waste.
Problem and Context
Every year, around 24 billion pairs of shoes are produced worldwide for 8 billion people. The problem is even more acute when it comes to children's shoes: on average, a child wears a shoe for only 3 to 6 months before outgrowing it. These short usage cycles lead to enormous amounts of waste, exacerbated by the multi-materiality of conventional shoes. Leather, textiles, foams, and plastics are glued and sewn together. This composite makes recycling nearly impossible.
Added to this is the dependence on global supply chains and energy-intensive manufacturing processes. The production of a single shoe often involves more than a hundred steps, many of which are done by hand. This makes children's shoes expensive, resource-intensive, and ecologically questionable. fëllig asks the question: What if we could manufacture children's shoes locally, using materials that can be returned to biological cycles or recycled at the end of their life cycle? What if the shoe grew with the child instead of being replaced?
Life cycle of a conventional shoe vs. fëllig
Research and material studies
It all started with the question of materials. I investigated three different approaches, each of which had the potential to fundamentally change shoe production: 3D printing, mycelium, and felt.
The realization was that none of the materials alone met all the requirements. But combining them opens up new possibilities. The hybrid approach, an additive structure as an outer shell filled with natural material, combines the precision of digital manufacturing with the properties of biological materials.
The three materials compared
Concept development
Material research led to the development of a two-part system. The outer shoe consists of a 3D-printed TPU structure that supports the foot and defines its shape. The inner shoe is made of virgin wool, which penetrates the cavities of the lattice structure during the felting process, creating soft, adaptable padding.
This modularity allows for flexibility in use: as the child's foot grows, the outer structure can be reprinted, the old framework is returned to the cycle, and the inner wool layer is composted. Both components remain separable by type. This is a decisive factor for true recyclability.
Initial material tests
Several iterations were created in CAD development. The lattice structure follows the natural flex zones of the foot, which saves material and increases structural integrity. The focus was on child ergonomics: wide toe box, flexible sole, light weight. At the same time, I tested different wool qualities and felting techniques to find the optimal balance between softness and stability. I also conducted various waterproofing tests with natural impregnations. It turned out that lanolin (wool wax), which is mostly used to impregnate wool diapers, is the best at repelling water.
Initial material tests
Process and production
The fëllig manufacturing process combines automated steps and production using standard household machines to create a hybrid workflow. First, the shoe mold is digitally generated based on the child's individual foot measurements. This data controls the 3D printer, which builds up the TPU structure layer by layer in a fab lab or at home.
After printing, the lattice structure is filled with virgin wool. The wool initially lies loosely against the walls of the lattice structure. Then the felting process begins: the shoe is filled with a sock. Small washing balls stabilize the shape of the sock and ensure that the virgin wool is pressed against the edge of the structure during felting. The filled shoe is washed in a conventional washing machine at 40°C. The virgin wool felts and forms a comfortable and insulated inner shoe.
After felting, the shoe is dried. Optionally, the surface can be treated with natural wax to increase weather protection. The entire process requires no adhesives, no seams, no complex machines, just a 3D printer, a washing machine, and time.
Final process for fëllig
Final process for fëllig
Final process for fëllig
Result
The result is a shoe whose design follows its function. The lattice structure meets the requirements for flexibility and protection for children's shoes, while the wool felt provides a comfortable inner shoe and shimmers in natural gray and beige tones through the openings. The result is a material honesty that is both technically and haptically convincing. The shoe feels soft, adapts to the foot, and at the same time offers the necessary stability for first steps and wild romping.
The ergonomic shape takes into account the anatomical characteristics of growing children's feet: a wide, unrestricted toe box, a flexible sole that supports natural rolling movements, and a low weight that promotes freedom of movement. The light color of the TPU and undyed wool combines technology with naturalness.Material and design concept
Design concept
Design detail: removable inner shoe
Design detail: functional structure
Reflection and outlook
fëllig began as a question and ended as a learning experience. The biggest insight: sustainability is not a label, but the result of understanding processes. Knowing materials means considering their origin, properties, and end of life. Technology can only support sustainability if it is used with respect for natural systems.
The next steps could be more radical. Modular sizing systems that grow with the child and only replace individual components. Scalability through decentralized production networks that use regional materials. fëllig is not a finished product; it is a prototype for a way of thinking that understands design as a responsibility.
First prototype
First prototype grid detail
First prototype sole detail
First prototype heel detail