In 2014 when Matrix started the design of the PowerWatch, the smallest wireless wearable prototype from an advanced research lab had a volume of over 100cc, approximately the size of a bar of soap, with no display or user input. In order to reduce that to a size that a consumer would find attractive (less than 40cc) and add modern smartwatch features, our design team had to attack multiple aspects of the thermal energy harvesting system design:
- The TEG hot side is bonded to an aluminum plate that conducts heat from a 20 square centimeter area of the outside of the user’s wrist (users who wear the PowerWatch on the inside of their wrist harvest significantly more power!)
- The heat is channeled through the TEG and out to the watch body by an intricate transport structure.
- The body of the watch is insulated from the bottom plate by a frame cast of thermoplastic chosen for its insulating properties.
Thermal systems design is the most difficult aspect of any wearable energy harvesting project. For this reason, Matrix provides thermal engineering & design services to our OEM customers.