Contact‐Free Human‐Machine Interfaces via Printed Thermopile Infrared Arrays

ABSTRACT Human‐machine interfaces (HMIs) are evolving as key components for advanced sensing in communication and control systems. In particular, contact‐free HMIs can facilitate unique advantages in hygiene, durability, and non‐destructive sensing. However, spatially resolved sensing platforms remain challenging using bulk approaches. Here, we report flexible infrared interface arrays (TIA1 and TIA2) with ≥10 pixels that exploit the photo‐thermoelectric (PTE) infrared sensing properties of Bi‐Te‐based thermoelectric (TE) materials via a dual‐stage energy conversion process: radiation‐to‐thermal, followed by thermal‐to‐electric. The p‐ and n‐type TE materials and electrodes were printed on polyimide to fabricate TIAs. After encapsulation with a black absorber, radially patterned silver mirrors are printed on the outer part of the pixels using aerosol jet‐printing to partially shield each thermocouple. This induces a localized temperature gradient, hence an output voltage via the Seebeck effect under infrared illumination. The pixels exhibit responsivities of 0.7 VW −1 (TIA1) and 0.9 VW −1 (TIA2), respectively, under CO 2 laser irradiation (10.6 µm), with pixel‐to‐pixel variation within ± 10%. The TIAs were demonstrated as non‐contact handwriting and dialing interfaces, converting human gestures into digital signals. These results pave the way for a self‐powered and contactless interface for future human–machine interaction technologies.