3D printed breathable midsole with adjustable cushioning using lignin-based polyurethane foam
A 3D printed midsole technology featuring built-in airflow channels and one-way valves that enable a breathing mechanism during walking or running. Made from sustainable lignin-based polyurethane foam, the system allows tunable cushioning for different athletic applications such as running and basketball shoes.
Overview
This technology introduces a novel midsole design for athletic footwear that combines 3D printing with sustainable, lignin-based polyurethane foam to create an adjustable cushioning system with built-in breathability. The midsole incorporates internal airflow channels connected to the shoe interior through surface holes and to the outside through one-way valves inspired by heart valve mechanics. As the wearer walks or runs, foot compression pushes air out through the open valves, and when compression is released, the valves close to create reduced pressure zones that draw in fresh air. This produces a continuous breathing effect that enhances ventilation while maintaining cushioning performance.
Technical specifications
- Manufacturing method: Fused Deposition Modeling (FDM) 3D printing followed by compression molding foaming with supercritical CO2
- Material: Lignin-based polyurethane foam, a renewable and low-cost functional composite
- Airflow design: Internal channels connected to inner shoe space via surface holes and to the exterior via single-direction breathable valves
- Adjustable cushioning: Density of porous structures controlled by printed material density and foaming ratio
- Low density and high foaming ratio produce softer, energy-absorbing midsoles suited for walking shoes
- Higher density and lower foaming ratio yield harder, more responsive midsoles for basketball or performance applications
- Sustainability advantage: Uses lignin, a bio-based feedstock, replacing conventional petroleum-derived midsole materials
Technology readiness level
The concept is currently at an early research and exploratory validation stage. Initial hypothesis testing has been supported by exploratory modeling and practical 3D printing studies. Future validation involves a two-step fabrication process: printing precursor shapes with designed channels using FDM, then applying compression modeling foaming technology with supercritical CO2 to generate controlled porous structures. Further testing of airflow, cushioning, and durability performance is needed before commercial readiness.
About University of Tennessee, Knoxville
The University of Tennessee, Knoxville is a comprehensive public land‑grant research university—the flagship of the UT System—classified as R1 and serving more than 40,000 students. Industry engagement is anchored by the UT Research Park at Cherokee Farm, where corporate R&D and joint university–national lab facilities sit just across the river from campus, including assets such as the Volkswagen Innovation Hub and an AT&T 5G testbed. UT’s long‑standing partnership with Oak Ridge National Laboratory—via UT‑Battelle and the UT–Oak Ridge Innovation Institute—gives companies streamlined access to national lab capabilities, talent, and joint programs. A statewide Extension network and established co‑op programs connect companies to faculty expertise and student talent across Tennessee and into federal labs. Research is supported by competitive federal sponsors such as the National Science Foundation and the U.S. Department of Energy. Commercialization is managed by the University of Tennessee Research Foundation, which handles IP, licensing, and startup formation.
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