Shape memory alloy fibers having rapid twitch response
AssigneeThe Royal Institution for the Advancement of Learning/Mcgill University
InventorsIan Hunter, Serge R. Lafontaine
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Abstract
A modified shape memory alloy fibers exhibits a rapid twitch response under timulation by an action potential such as the heating effect of an electromagnetic pulse; in particular the relaxation time of the twitch response is considerably shortened as compared with that of the unmodified fibers; the modification is achieved by simultaneous application of a stretching force and a short, powerful electromagnetic pulse effective to bring about contraction resulting from the shape memory and change material properties; this application is carried out a plurality of times.
Claims23
An actuator element for generation of a working force comprising a modified elongate fiber of a shape memory alloy, said modified fiber being derived from an unmodified fiber, said unmodified fiber having been modified by being subjected a plurality of times to a short, very powerful electromagnetic pulse effective to cause contraction of the length of the unmodified fiber and change material properties while under a stretching force serving to elongate said length, said modified fiber exhibiting a twitch response under stimulation by an action potential, said twitch response comprising a contraction time and a relaxation time, said twitch response being rapid as compared with the twitch response of the unmodified fiber.
An elongate fiber of a shape memory alloy modified by having been subjected a plurality of times to a short, powerful electromagnetic pulse effective to cause contraction of the length of the fiber and change material properties, while under a stretching force serving to elongate said length, wherein said pulse has a current density of 400 to 4000 MA/m.sup.2, and has a rate of current change of at least 200,000 A/sec.
A motor unit for generation of a working force in response to stimulation by an action potential in an artificial muscle comprising;
- first and second opposed, spaced apart clamping means,
- at least one elongate actuator element comprising an elongate fiber of a shape memory alloy providing a plurality of lengths of fiber in side-by-side, generally parallel relationship extending between said spaced apart clamping means, said lengths being electrically insulated from each other and from said first clamping means,
- electrical connection means for connecting said at least one fiber to a source of electromagnetic pulses at said first clamping means, and
- connection means at said second clamping means for connecting said at least one fiber to a work element,
- said elongate fiber exhibiting a twitch response under stimulation by an action potential, said twitch response comprising a contraction time and a relaxation time and being less than 40 ms.
A process for modifying an elongate fiber of a shape memory alloy comprising subjecting said elongate fiber to a stretching force while applying a plurality of short, very powerful electromagnetic pulses effective to cause contraction and change material properties of the fiber, wherein said electromagnetic pulses have a current density of 400 to 4000 MA/m.sup.2.
A process for modifying an elongate fiber of a shape memory alloy comprising subjecting said elongate fiber to a stretching force while applying a plurality of short, very powerful electromagnetic pulses effective to cause contraction and change material properties of the fiber, wherein said pulses have a rate of current change of at least 200,000 A/sec.
A process for modifying an elongate fiber of a shape memory alloy comprising subjecting said elongate fiber to a stretching force serving to elongate the length of the fiber while applying a plurality of short, very powerful electromagnetic pulses effective to cause contraction and change material properties of the fiber, said fiber being a Ni-Ti fiber having a diameter of 0.01 to 10 mm, wherein said fiber prior to said subjecting has a twitch response comprising a total contraction rise time and relaxation decay time greater than 1000 ms, and said fiber after said subjecting has a twitch response of less than 40 ms.
A modified elongate fiber derived from an elongate unmodified fiber of a shape memory Ni-Ti alloy, said unmodified elongate fiber having a twitch response, when subjected to an action potential effective to heat said fiber to the shape memory state, with a total contraction and relaxation time greater than 1000 ms, said modified fiber having a twitch response of less than 40 ms and said modified fiber having a diameter of 0.01 to 10 mm, said unmodified fiber having been modified by being subjected a plurality of times to a short, powerful electromagnetic pulse having a current density of 400 to 4,000 MA/m.sup.2, and a rate of current change of at least 200,000 A/sec, effective to cause contraction of the length of the unmodified fiber and change material properties while under a stretching force serving to elongate said length.
Dependencies are inferred from the claim text.