Polycrystalline Foams Exhibiting Giant Magnetic-Field-Induced Deformation and Methods of Making and Using Same

David Dunand (Inventor)

Research output: Patent


Magnetic Shape-Memory Foams for Actuators and Other Industrial Purposes NU 2009-109 Inventors Xuexi Zhang David C. Dunand* Peter Mullner Markus Chmielus Cassie Witherspoon Short Description Polycrystal memory foam for less expensive, more stable actuators Abstract Magnetic shape memory alloys (MSMAs) are a field of active materials that enable fast, large-strain actuators. Single crystal shape-memory alloys have thus far been utilized; very high (~10%) magnetic-field-induced strains (MFIS) for single-crystal nickel-manganese-gallium (Ni-Mn-Ga) alloys have been measured. However, Ni-Mn-Ga single crystals are brittle and difficult to prepare, thus limiting their commercial potential. Randomly textured, fine-grained, polycrystalline Ni-Mn-Ga alloys are easier to manufacture, but result in near-zero MFIS. Northwestern inventors have overcome these performance limitations by synthesizing the alloy as a polycrystalline foam structure. The foam permits single crystallinity deformation to extend over longer distances, resulting in greater field induced strain (2-4%) - i.e., the foam changes shape in strong magnetic field. This development will allow for the manufacture of actuators using polycrystals, which are less restrictive to produce than the single-crystal variety. Applications o Long-stroke actuators (aerospace, automotive, and biomedical devices) o Sensors o Magnetic cooling systems o Energy devices Advantages o Inexpensive casting process o Actuation stroke 100 times that of piezoelectric actuator materials, but with comparable response time o Compact, lightweight, and robust IP Status Issued US Patent No. 8,586,194 Marketing Contact Allan Nader, PhD Invention Manager (e) a-nader@northwestern.edu (p) 847.491.4456
Original languageEnglish
Patent number8586194
StatePublished - Mar 17 2011


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