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Magneto-Rheological Fluids, Gels, and Elastomers

Description:

University of Nevada, Reno researchers, Faramarz Gordaninejad and Alan Fuchs, of the Mechanical Engineering Department and Chemical Engineering Department, respectively, conduct research in the fields of vibration control of mechanical systems and structures, field-controllable electro- and magneto-rheological fluids and devices, as well as polymer materials development, and polymer based magnetic fluids.

Technology Summary
The UNR magneto-rheological (MR) materials include fluids, gels, and elastomers, and are made of magnetic particles suspended in a carrier material/fluid that form chains when a magnetic field is applied. Such MR materials can be continuously and rapidly controlled by the magnetic field – their stiffness or viscosity altered – making them useful for vibration isolation and absorption applications. In a feature of the MR material, the carrier material is a polymeric gel and is partially covalently-cross-linked. The crosslinking takes place on the particles’ surfaces and is advantageous as more crosslinking and gel formation within a polymer leads to greater viscosity, very low settling rates of the particles, good dispersion characteristics, superior “off-state” viscosity (in the absence of a magnetic field), as well as “on-state” viscosity (in the presence of a magnetic field). Control of the carrier fluid viscosity and higher yield stress (the stress level at which a material ceases to behave elastically) is also achieved.

The MR polymer gel (MRPG) can be developed at different levels of off-state properties through the formulation of the cross-linkers. In this way, the MRPG viscosities are custom-suited to a particular device, and have a fail-safe characteristic when employed in dampers. Off-state viscosity minimization can be extremely valuable for applications requiring high damping forces including earthquake control, aerospace applications, and land-based applications.

In another feature, the MR material is made of magnetizeable iron or metallic iron alloy particles in an elastomeric matrix that is a thermoset (polymer material that irreversibly hardens) chosen from the group consisting of: silphenylene-siloxanes, silarylene-siloxanes, poly(carborane-siloxane-acetylene)s, and blends thereof, where the magnetizable particles are aligned. These MR materials can have improved oxidative resistance, thermal oxidative resistance, high temperature resistance, ozone resistance, moisture resistance, and seawater resistance over conventional MR materials.

The magnetizable particles can be coated with a silane coating, and then with a surfactant coating to reduce corrosion, improve durability of the particles, and improve particle bonding and interaction in the elastomer. Treated and untreated particles were tested by immersion in synthetic seawater and showed a dramatic reduction in the oxidation of the iron particles in the elastomer – even when the silane coating did not appear to be complete on all particles.

Another feature of the patented UNR MR material is a supramolecular polymer gel (held together by non-covalent bonds) that comprises crosslinks formed by weaker force attractions including: metal coordination, hydrophobic/hydrophilic interactions, p-p stacking, van der Waals forces, and combinations thereof. This polymer gel has excellent remixing or redispersion properties, and such attractions have advantages over covalent polymer gels because they are tunable and reversible rather than permanently bonded. The bonds’ ability within the gel to break with stress and re-unite after the removal of stress also improves the durability of the material, increases its lifetime, and improves the response of the fluid to external shear stress.

In a closely related feature, the supramolecular polymer gel comprises a network of metal coordinated bipyridine polymer that exhibits reduced abrasiveness and produces high stability with regard to settling of the particles. At least a portion of the magnetizable particles can be coated with a coating involving a surfactant and a polymerized monomer non-covalently bonded to a second monomer. The coating improves dispersion characteristics and the lubricity of the particles, further protecting the particle surface against corrosion and abrasive fracture. Fluid stability is also enhanced.

Potential Applications
Vibration control applications include use in devices and systems such as:

  • Vibration mitigation and energy absorption devices to protect civil infrastructure such as buildings and the decks of bridges under natural hazards, man-made hazards and/or seismic events.
  • Shock absorbers in mechanical systems such as bicycles, motorcycles, automobiles, trucks, trains, airplanes, military transport vehicles, exercise equipment, and sports equipment (i.e. landing gear).
  • Other automotive parts such as engine mounts, seat dampers, and clutches.
  • Vibration isolation and shock mitigation for laser/optics systems and equipment such as optical tables, bench top platforms, breadboards, support systems, and individual mounts.
  • Vibration control of automation and testing equipment in the semiconductor manufacturing industry, including active- and passive-air isolation workstations.
  • Super isolated workplaces protected from vibrations and disturbances for the precise assembly of sensitive components used in aerospace or bioscience projects.

Opportunity
UNR is seeking expressions of interest from parties interested in collaborative research to further develop, evaluate, or commercialize this technology.

IP Status
UNR ID#: UNR00-006
Magneto-rheological Materials – Fluids, Gels, and Elastomers.
US Patent No.: 6,527,972; 7,261,834; 7,297,290; 7,883,636; 8,241,517

Patent Information:
For Information, Contact:
Dan Langford
Technology Commercialization, Manager
University of Nevada, Reno and Desert Research Institute
dlangford@unr.edu
Inventors:
Alan Fuchs
Faramarz Gordaninejad
Daniel Blattman
Gustav Hamann
Keywords:
Dampers
Devices