Abstract
Shape memory alloys (SMAs) have found widespread applications as biomedical devices. Biocompatibility, corrosion resistance, and ductility make these alloys attractive for medical devices such as stents and filters. For these implants, the superelastic property is the primary function of SMAs. Additionally, these alloys, such as NiTi as the prime example, can be used for actuation. Several modes of actuation such as displacement control, force control, and compliance control have been used as harnesses with SMA devices. These two unique properties have opened another application in the form of neurosurgery and robot-assisted surgery devices, as well as controlled assistive and rehabilitation devices. This paper reviews the state of the art of application of SMAs in the latter category where control is applied to harness innovative medical devices. To this end, two major subsets of these devices: prosthesis and orthosis which take the advantage of SMAs in assistive and rehabilitation devices are studied. These devices are further categorized to hand prosthetics, elbow, knee and ankle orthotics. In most of these designs, SMA wires act as artificial muscles to mimic the motion of limbs in the target joints. The evolution of each category is explained, and the specific results of them are reported. The paper also reviews the SMA applications for neurological and neuromuscular rehabilitation. To this end, different categories of rehabilitation devices as a passive and aided exercise for the ankle, knee, and elbow are highlighted. The SMA actuator in these devices can be EMG-controlled to improved patient outcome. In addition to providing a comprehensive overview of the biomedical devices, this paper identifies several possible future directions of SMA related research in the area of assistive and rehabilitation devices.
Highlights
Shape memory alloys (SMAs) are the metallic materials that have the ability to return to some previously defined shape when they are subjected to the appropriate thermo-mechanical loading
According to the high variety of SMA applications in the biomedical domain, this paper studies the biomedical applications of the SMA (NiTi) in two main subsets: the assistive and the rehabilitation devices
Knee ankle foot orthoses (KAFOs) are prescribed to improve abnormal ambulation of the knee caused by quadriceps weakness
Summary
Shape memory alloys (SMAs) are the metallic materials that have the ability to return to some previously defined shape when they are subjected to the appropriate thermo-mechanical loading. H. Taniguchi designed a prosthetic hand for children by utilizing SMA actuators as the drive source to achieve a small size, silent operation, high output power, and low mass device [24,25]. The reduction in the maximum knee flexion angle of the dynamic mode during the stance phase and swing phase were reported to be approximately 35% and 33%, when compared to those in the slow walking condition, respectively. The reason for this testing was to find the requirements for SMA wires which are considered to be added to the nonwired hinged AFO, such as the required level of angles and moments. FigureFi2g8urseho2w8 shtohwe sttihffenesstsiffpnreosfsilperoobfitlaeinoebdtafirnoemd frinoimte fienleimteeenltemaneanltysainsafloyrsitshfroere tdhirfeferednifft erent condictioonnds:itHioenasl:thHy esaulbthjeyct,suthbejepcta,titehnet wpaetaierinntgwcoenarvienngticoonnavl esntatinolneasls-ssttaeienllsepssr-instgeeblasepdrinAgFOba, saendd AFO, patienatnwd epaartiinegntswupeaerienlagsstiucpNerieTliasstpicriNngiTbi assperdingAFbOas.eIdnAthFOe .cIansethoef cuasienogf NusiTinigspNriiTnigs,ptrhine ga,ntkhleeankle showesdhoawcelodsaercslotisfefnresstsiffpnreosfsilpertoofitlheetonothrme nalowrmaalkliwnga.lkHinogw.eHveorw, ienvethr,eincatsheeocfausesionfgusstianinglsetsasi-nstleessl -steel springssp,rtihnegsa,ntkhleeasntikfflenesstisffwneassawlmasosatlmlinoesatrl,insheaorw, sihnogwailnagrgaeldaregveiadtieovniaftriomn ftrhoemntohremnaolrsmubajlescut.bject
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