A Designer Turns Discarded Tennis Balls Into Sneakers With 3D-Printed Cutting Guides

Cutting, not shredding

Soroosh Riazi Isfahani, a design student at the Royal College of Art and Imperial College London, has entered a footwear project called SLICE into the James Dyson Award 2026. The idea is straightforward: take the 300 million or so used tennis and padel balls that get discarded each year, and turn them into shoes without melting, shredding, or chemically processing the rubber.

Isfahani started by grinding balls into granulate and mixing the particles with natural rubber to form an outsole. That worked, but it erased what makes a tennis ball useful. The curved shape disappeared. The bond between the fuzzy felt exterior and the rubber core got destroyed. He switched to a simpler method: cutting the ball into sections while keeping the layers intact.

3D-printed guides make the cuts repeatable

A tennis ball is round, pressurized, and rolls when you try to cut it by hand. To get consistent sections, Isfahani designed and 3D printed custom cutting guides. Each guide holds the ball steady and defines exactly where the blade goes. Because the guide is a digital file, changing the shoe size or the pattern just means reslicing the model and printing a new jig.

The cuts release curved bands and cup-like caps from the ball's surface. The wider pieces wrap around the forefoot. Narrower strips follow the sides. Isfahani shapes the pieces over a traditional shoe last and stitches them together with end-of-life racket strings. No heat, no chemical adhesives, no glue. The fluorescent yellow felt, white stitching, and scuff marks from actual play stay visible.

The aesthetic is closer to a material study than a performance sneaker. The finished shoe is broad, slightly bulky, and clearly shows where its parts came from. That is intentional. Isfahani cites Freitag bags as an influence, where the wear and history of the source material is part of the design.

Why slicing beats shredding

Most recycling programs for tennis balls grind them into crumb for playground surfaces, flooring, or low-value molded products. The rubber, adhesive, and felt are bonded in layers that standard facilities cannot separate cheaply. A ball that gets thirty minutes of professional play can take four centuries to decompose in landfill. Only around one percent enter any kind of recovery stream.

SLICE does not solve that entire problem. It does offer a different logic. Instead of asking how to turn tennis balls into generic recycled feedstock, it asks what the ball is already good at. Tennis ball rubber is tough and resilient. The felt is grippy. Both properties belong in a shoe. By slicing rather than pulverizing, the project keeps those characteristics and builds the footwear around them.

Isfahani plans to test versions that combine the ball sections with leather offcuts. He is also exploring bags and sports accessories using the same cutting method. A custom service using balls from a specific tournament or club is another possibility. The project currently exists as an experimental prototype and a James Dyson Award entry.