Fig. 2: The fabricated double-chain thermoelectric generators (DC-ThEGs) showed remarkable flexibility and uniformity according to the observational characterization based on photographic, optical microscope and scanning electron microscopy (SEM) images.

a Schematic diagram of the DC-ThEG, which consists of a flexible PI substrate, two thermocouple chains made of Bi₂Te_2.7Se_0.3 (n-type) and Sb₂Te₃ (p-type), and a functional chain-gap-covering membrane made of silk fibroin. b Photograph of a bent DC-ThEG with a size of 60 mm × 35 mm × 0.2 mm, exhibiting good flexibility. Each individual thermoelectric chain possesses 5 pairs of p-type/n-type thermocouples. c High-magnification image showing the junctions of printed p-type/n-type thermocouples. d, e SEM images of printed n-type and p-type thermoelectric materials. Compared with traditional single-chain thermoelectric generators (ThEGs), this novel double-chain configuration endows ThEGs with the unique feature of simultaneously harvesting thermal energy and realizing multiple sensing functions by utilizing these two chains as electrodes with the help of the functional material covering the gap between them