Designable high-performance TPU foam strain sensors towards human-machine interfaces

Flexible, breathable, and stable sensors were important in developing human–computer interaction systems and novel wearable devices. However, major challenges were still faced in two aspects, 1) high-performance strain sensors with a large sensing range, and 2) an interaction mode that is both convenient and efficient. Herein, we developed a thermoplastic polyurethane large-skeleton foam (TPU-LS foam) through a steam-induced method. The strain sensor comprised three layers of breathable foam, with CNTs/rGO TPU-LS foam as the inner layer and pure foam as the protective layer. PDMS/TiO2 was sprayed to create a UV-resistant and self-repairing coating, achieving a 66% melanin inhibition rate and a 91% repair rate. The sensor presented a wide work range over 100%, a high gauge factor of 637.8, and long-term durability. We trained machine learning frameworks to recognize different gestures and designed two types of human–computer interaction patterns, allowing users to operate apps with gestures.