Prototyping

Our design for a cooling layer to be added within the comfort layer involved 3 elements: the matrix, shredded foam filler, and a mesh layer of fabric to hold everything together. The design was chosen to improve air flow and thermal conductivity compared to a layer of non-cooling memory foam. Improved heat transfer was our focus. Since memory foam is highly porous, it is thermally insulating. Non-porous materials conduct heat better but can reduce air flow. We decided to design a layer that would provide for a path of continuous heat flow, without obstructing the airflow. To achieve continuous heat flow, our prototype was made with silicone rubber. It is soft like bedding but much less porous. 

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The silicone matrix was made with Smooth-On ™ platinum cure rubber 00-30. To improve the thermal conductivity of the silicone gel, graphite was used. Small bars of silicone containing 5%, 2.5%, and 1.25% graphite filler were cast. The thermal conductivity and heat capacity were determined using DSC. To cast the matrix, we 3D printed 36, 1.75 x 1.75 x1 in cubes to be placed in a 12x12 in mold for casting. The cubes were placed in the mold to make a 6x6 grid with about 0.25in of space between each square. The silicone rubber was then mixed and poured into the mold and left for 4 hours to cure. 

The matrix was demolded and measured. A layer of stretch mesh fabric was glued to one side of the matrix using spray batting adhesive. Then each cavity was filled with shredded polyurethane foam. The average size of the polyurethane shredded piece was about 1 cm3. After filling the cavities, the foam was sealed with the matrix by gluing another piece of stretch mesh fabric on the top.