Advanced Graphite and Transition Percolation Materials for Room-Temperature Thermal Switches

Technology #13749-13853

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Graphite microfluids
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Inventors
Professor Gang Chen
Department of Mechanical Engineering, MIT
External Link (web.mit.edu)
Ruiting Zheng
Department of Mechanical Engineering, MIT
Jinwei Gao
Department of Mechanical Engineering, MIT
Managed By
Christopher Noble
MIT Technology Licensing Officer - Clean and Renewable Energy
Patent Protection

Graphite microfluids

US Patent 8,192,643
Publications
Thermal Percolation in Stable Graphite Suspensions
Nano Letters, 2012, 12 (1), pp 188–192
Viscosity and Thermal Conductivity of Stable Graphite Suspensions Near Percolation
Nano Letters, 2015, 15 (1), pp 127–133

Applications

The long standing demands on high thermal conductivity fluids have pushed for research in nanotechnology-based heat transfer fluids that have lower capital costs and higher energy efficiencies. Graphite microfluids have potential use in the fields of energy and mechanical engineering. Phase transition percolation materials can be used for temperature sensing and control, thermal management, and thermistors.

Problem Addressed

This technology helps overcome the problem with low thermal conductivity and the high costs associated with thermal transfer between fluids. Although some technologies have been created in nanofluids, i.e. phase transition percolation materials that result in significant change in electrical and thermal conductivities, current thermistors only work at low temperatures. However, thermistors based on phase transition percolation composites are able to function at a room temperature range, the range at which people have the largest need for temperature controlling. Even though  it has been found that some higher thermal conduct values are unrepeatable, and most of nanofluids have no obvious thermal conductivity, this technology proposes a low cost synthesis of graphite microfluids, using Carbon nanotubes (CNT's), that exhibit high thermal conductivity and offer a basis for new applications for thermistors in energy and mechanical engineering. 

Technology

These inventions pertain to new types of microfluids and transition percolation materials. The technology proposes a graphite microfluid that exhibits uniform suspension of graphite microflakes (dimensions on the order of 10μm x100nm) in water, ethylene glycol and oil as a new phase transition percolation material. The host material is suspended in liquid phase forming a percolation network that exhibits desirable properties (electrical, thermal, magnetic, piezoelectric, optical, etc.). The material does not exhibit these properties in solid form creating a large contrast between material properties in solid or liquid phase. Graphite microflakes are an ideal candidate for nanoparticles used in microfluids  because of their higher thermal conductivity, lower density, and lower price.  The proposed method would allow for an effective synthesis of a phase transition percolation material to get the high thermal conductivity lacking in existing thermistors. 

Advantages

  • Low density of microflakes increases stability and simplifies suspension process
  • High thermal conductivity
  • Inexpensive
  • High sensitivity to temperature, magnetic, or optical changes depending on applications
  • Self-healing