Abstract
Shape-Memory Polymers (SMPs) are considered a kind of smart material able to modify size, shape, stiffness and strain in response to different external (heat, electric and magnetic field, water or light) stimuli including the physiologic ones such as pH, body temperature and ions concentration. The ability of SMPs is to memorize their original shape before triggered exposure and after deformation, in the absence of the stimulus, and to recover their original shape without any help. SMPs nanofibers (SMPNs) have been increasingly investigated for biomedical applications due to nanofiber’s favorable properties such as high surface area per volume unit, high porosity, small diameter, low density, desirable fiber orientation and nanoarchitecture mimicking native Extra Cellular Matrix (ECM). This review focuses on the main properties of SMPs, their classification and shape-memory effects. Moreover, advantages in the use of SMPNs and different biomedical application fields are reported and discussed.
Highlights
The chemical architectures common to all Shape-Memory Polymers (SMPs) is the possession of molecular switching segments and net-points
SMPs can be classified according to their shape-memory effect (SME), as oneway shape-memory effect (OWSME), two-way reversible shape-memory effect (TWSME) and multiple-SME (Figure 1), whose definitions are reported here below
Examples were reported in which Cellulose nanowhiskers (CNW) and microcrystalline cellulose (MCC) were introduced in polyurethane and poly (D,L-lactide) matrices in order to achieve a faster switchable shape-memory effect at physiological temperature (37 ◦C) [47,48]
Summary
These SMPs can be activated by direct thermal application, and when the temperature applied is higher than polymer transition temperature (Ttrans), a transitory shape can be programmed. Combining SMPs with other responsive materials (nanofillers) such as Fe3O4, gold and silver nanoparticles (AuNPs and AgNPs), carbon nanotubes (CNTs), graphene oxide (GO) and cellulose nanocrystals, makes it possible to use remote temperature control by magnetic and electric field, microwaves, UV (ultraviolet) and NIR (near infrared) irradiations [32,33]. In these systems, heating generation is induced by molecular vibration, and energy magnitude is directly proportional to the nanofillers’ concentration and particle size. TrelliX Embolic Coil devices are covered by the following issued patents (US8133256 and US10010327) [34–36]
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