Additively manufacturable and stretchable thermoelectric devices

1 . A method of fabricating a wearable and elastically stretchable thermoelectric generator, the method comprising:

arranging a plurality of thermoelectric pellets;

printing a thermal insulation material alongside and/or around the plurality of thermoelectric pellets to form a core layer that includes the thermal insulation material and the plurality of thermoelectric pellets, wherein the thermal insulation material comprises an elastomer composite with embedded hollow microspheres, and wherein the printing the thermal insulation material positions at least some of the embedded hollow microspheres between at least some of the thermoelectric pellets;

curing the core layer to expand hollow microspheres within the core layer so as to decrease a density of the core layer to be less than before the curing;

selectively depositing a liquid metal on the thermoelectric pellets embedded in the core layer to form contact points;

printing conductive ink comprising liquid metal droplets in an arrangement forming stretchable electrical interconnects that define connections among the thermoelectric pellets via the contact points so as to form an initial middle layer that includes the stretchable electrical interconnects;

printing a thermal interface material so as to form an initial outer layer, wherein the initial middle layer is positioned between the initial outer layer and an initial side of the core layer to form a layered assembly;

inverting the layered assembly to expose a subsequent side of the core layer disposed opposite the initial side;

printing additional conductive ink to form a subsequent middle layer; and

printing an additional thermal interface material to form a subsequent outer layer, wherein the subsequent middle layer is positioned between the subsequent outer layer and the core layer.

2 . The method of claim 1 , wherein the liquid metal droplets for stretchable electrical interconnects comprise eutectic gallium indium.

3 . The method of claim 1 , wherein the thermal insulation material comprises an elastomer composite with embedded hollow microspheres.

4 . The method of claim 1 , further comprising applying a pressure or other mechanical forces to the core layer subsequent to curing the core layer and with magnitude sufficient to activate the liquid metal percolating networks.

5 . The method of claim 1 , wherein the thermal interface material comprises a liquid metal elastomer composite with a liquid metal volume fraction of 50% V f with respect to an elastomer base that has a thermal conductivity of between 1 and 1.7 W m −1 K −1 .

6 . The method of claim 1 , wherein the thermal insulation material comprises a hollow microsphere embedded elastomer composite with a thermoplastic microsphere volume fraction of 50% V f with respect to an elastomer base that has a thermal conductivity of between 0.09 and 0.12 W·m −1 ·K −1 .

7 . A method of fabricating a stretchable thermoelectric device, the method comprising:

depositing a thermal insulation material alongside and/or around a plurality of thermoelectric pellets to form a core layer that includes the thermal insulation material and the plurality of thermoelectric pellets, wherein the thermal insulation material comprises an elastomer composite with embedded hollow microspheres, and wherein the depositing the thermal insulation material positions at least some of the embedded hollow microspheres between at least some of the thermoelectric pellets;

curing the core layer to expand hollow microspheres within the core layer so as to decrease a density of the core layer to be less than before the curing;

depositing material to form an initial middle layer comprising stretchable electrical interconnects arranged as connections among the thermoelectric pellets;

depositing a thermal interface material to form an initial outer layer, wherein the initial middle layer is positioned between the initial outer layer and the core layer; and

depositing a subsequent middle layer and a subsequent outer layer on an opposite side of the core layer with respect to the initial middle layer and initial outer layer.

8 . The method of claim 7 , wherein the material comprises liquid metal droplets of eutectic gallium indium.

9 . The method of claim 7 , wherein the thermal insulation material comprises a hollow microsphere embedded elastomer composite with a thermoplastic microsphere volume fraction of 50% V f with respect to an elastomer base that has a thermal conductivity of between 0.09 and 0.12 W·m −1 ·K −1 .

10 . The method of claim 7 , wherein the depositing the subsequent middle layer comprises depositing subsequent material to form the subsequent middle layer with stretchable electrical interconnects arranged as connections among the thermoelectric pellets, and wherein depositing the subsequent outer layer comprises depositing a subsequent thermal interface material to form the subsequent outer layer, such that the subsequent middle layer is positioned between the subsequent outer layer and the core layer.

11 . The method of claim 7 , further comprising selectively depositing a liquid metal on the thermoelectric pellets of the core layer.

12 . The method of claim 7 , further comprising applying a pressure to the core layer subsequent to curing the core layer.