Physically crosslinked poly(vinyl alcohol) hydrogels with magnetic field controlled modulus

Abstract

Physically cross-linked isotropic and anisotropic poly(vinyl alcohol) (PVA) hydrogels containing micron-sized carbonyl iron particles were prepared through a cyclic freezing-thawing process. The PVA hydrogel can respond to a magnetic field and shows a magnetorheological (MR) effect, i.e., the modulus of the PVA hydrogel can be adjusted under a magnetic field. The chain-like structures of carbonyl iron are formed in the PVA hydrogel after orientation under a magnetic field of 1.5 T. Also some magnetic field induced oriented pores with a tunable diameter are observed in the dried PVA gel. The MR effect can be adjusted by changing the carbonyl iron content, the initial concentration of PVA solution and test frequency. The formation of aligned chain-like structures of carbonyl iron in the anisotropic PVA MR hydrogel improves the compression properties and the MR effect. At a carbonyl iron content of 70 wt%, the maximum absolute and relative MR effect of anisotropic PVA MR hydrogels are $1.24 MPa and $230%, respectively. The PVA hydrogels with good MR effects and moderate mechanical strength have potential applications in artificial muscle, soft actuators and drug release.

Synthesis of Anisotropic Hydrogels and Their Applications

“…His reserach interests include optoelectronic soft materials, bioinspired macromolecules, and "aqua materials", and molecular and biomolecular machines. magnets with as trength of less than 1T esla can efficiently orient such an anofiller.E xamples include particles of magnetite, [50][51][52] barium ferrite, [53][54][55] and carbonyl iron [56][57][58] as well as nickel rods [59] and magnetite-coated alumina platelets. [60] Although such weak handheld magnets are generally not enough to orient diamagnetic nanofillers,s uperconducting magnets (with as trength of several Tesla) can efficiently orient them, such as peptide nanofibers, [61][62][63] polysaccharides, [64] functionalized carbon nanotubes, [65] micelles, [66,67] lipid bilayers, [68,69] graphene oxides, [70] and inorganic nanosheets.…”

Viscoelastic and structural properties of poly(vinyl alcohol)/poly(vinylpyrrolidone) hydrogels

“…8 Hydrogels were also employed in pharmaceutical industry as drug delivery systems, [8][9][10] wound and burn dressings, 11 care products, 12 etc. 8 Hydrogels were also employed in pharmaceutical industry as drug delivery systems, [8][9][10] wound and burn dressings, 11 care products, 12 etc.…”

Mechanics of magneto-active polymers

“…Finally, using the numerical model developed, we will study the effect of particle concentrations. It has been observed in experiments that MREs loaded with more iron particles usually have a stronger MR effect, both in shear and in tension/compression (Bellan and Bossis, 2002;Nikitin et al, 2006;Varga et al, 2006;Rao et al, 2010;Wu et al, 2011). …”