Direct ink writing of three-dimensional thermoelectric microarchitectures

Microthermoelectric modules can be used as energy harvesters, active coolers and thermal sensors in integrated systems. However, manufacturing such modules with traditional microfabrication processes is costly and produces only two-dimensional thermoelectric films, which limit the formation of high-temperature gradients and thus the amount of power generated. Here we show that microscale three-dimensional thermoelectric architectures can be fabricated through the direct writing of particle-based thermoelectric inks. Using size control and surface oxidation, the characteristics of (Bi,Sb) 2 (Te,Se) 3 -based particle inks are engineered to create colloidal inks with high viscoelasticity and without organic binders, and the inks are directly written into complex architectures using a 3D printing process. The resulting structures exhibit high thermoelectric figures of merit of 1.0 (p type) and 0.5 (n type), which are comparable to those of bulk ingots. Microthermoelectric generators made from three-dimensionally written vertical filaments exhibit large temperature gradients and a power density of 479.0 μW cm –2 .