This paper introduces a wearable thermoelectric generator (ThEG) with a novel double-chain configuration for simultaneous energy harvesting and multi-functional sensing. Unlike traditional single-chain ThEGs, each chain in this double-chain ThEG (DC-ThEG) harvests heat energy, and together they function as sensing electrodes. Screen printing is used to create the device, making it flexible, high-performance, and cost-effective. A silk fibroin layer covers the gap between the chains, enabling sensing of liquid water molecules and temperature. Experimental results show a 151 mV open-circuit voltage and the ability to generate 3.3 V to power devices like a calculator using body heat. This integrated approach of powering and sensing opens new avenues for advanced ThEGs, particularly in all-in-one self-powered microsystems.