Thermally conducting paper substrates

The existing traditional synthetic polymer substrates used in the production of flexible electronics (printed circuits) are thermal insulators, which accumulate the heat produced by the resistance of printed Si-chips/processors with the Joule effect; this affects the operation of the device and shortens its lifetime. Traditional active cooling methods are usually not compatible with flexible electronics, and also consume additional energy. The project will thus examine the possibility of producing cheap, green and recyclable electrically insulating and thermally conductive flexible paper substrates using inorganic 2D nanoparticles (graphene and hexagonal boron nitride/h-BN) and cellulose nanofibrils (CNF), which will ensure robustness, mechanical stability and additional cooling effect by desorption of accumulated moisture/water. We will examine the influence of the chemical and morphological structure of substrates produced by various industrially relevant technological processes (vacuum filtration, one-way freezing, surface coating using slot-die, screen-printing or spraying, TRL 1-4) on the ability to transfer heat and the way which will meet the technical specifications (flexibility, robustness, surface flatness, low expansion factor, minimal swelling, insolubility in water and organic solvents, good mechanical and thermal stability) required in the production of flexible electronics and for various applications (wearable electronics, smart products in healthcare /medicine, security/packaging, foldable opto/electronics, etc.). We will use artificial intelligence to optimize the dielectric, thermal, and optical properties of substrates, and perform LCA analysis. The newly developed substrates will be cost-effective, environmentally friendly, and easily recyclable with a smaller amount of waste. They will also be an effective alternative to expensive and environmentally harmful traditional hard ceramic substrates, enabling their use in thermoelectric heating and cooling modules without hazardous cooling systems.

Electronics are becoming mechanically flexible and reaching new areas of application in packaging, medicine, and intelligent devices, smart cities, etc. New zero-energy devices on flexible substrates with printed energy collectors/storage devices, Si-microprocessors, displays, sensors, etc. are under development. Although the emphasis is still on the production of small devices, the production of a flexible substrate with high thermal conductivity, efficient dielectric properties, and the use of sustainable materials and existing technologies represents a great challenge. "2D-paper" thus proposes a combination of 2D-materials based on hexagonal boron nitride (h-BN) and nanocellulose in the production of new thermally conductive paper substrates for recyclable flexible electronics. In addition to "h-BN", we will also explore other combinations of 2D materials (graphene) and use artificial intelligence to optimize their technical capabilities, especially the mechanical, dielectric, thermal, optical and chemical properties of the substrates made from them, as well as LCA analyses. One of the key challenges will be to consider sustainability in the stages of preparation (synthesis) and production (technological production) of the substrates in terms of the selection of materials and the method of recycling, since such substrates will be intended for mass production and integrated into the environment. The project involves experts with complementary knowledge with state-of-the-art infrastructure from Sweden, France and Slovenia, both from academia and industry. This will enable good planning, optimization and characterization, and the establishment of technical specifications for the production of such a thermally conductive paper substrate. The development of technologies from TRL1 to TRL4 will enable the transfer of knowledge and testing of production. A market transfer strategy will also be developed for the selected technological process, either through existing industrial partners or the establishment of a new start-up company.