Magneto-mechanical coupling in CoFe2O4-linked PAAm ferrohydrogels

Frickel, Natalia; Messing, Renate; Schmidt, Annette

doi:10.1039/c0jm03816d

Cited by 63 publications

(78 citation statements)

References 28 publications

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“…They are manufactured by applying a strong external magnetic field during preparation, which leads to the formation of oriented straight chain-like aggregates of embedded magnetic particles [43][44][45][46] . After subsequent chemical cross-linking of the embedding polymer network, the particle positions get permanently locked 47 . We assume that the magnetic moments carried by the particles are free to reorient.…”

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confidence: 99%

“…First, for diameters up to 10-15 nm, this applies within the interior of each magnetic particle 48 . Second, this is possible when each particle as a whole is free to rotate 47 , e.g., when the polymer is not completely cross-linked in the immediate particle vicinity 49 . Another example are yolk-shell particles with a magnetic core that can rotate within the shell 50,51 .…”

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confidence: 99%

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Tailoring superelasticity of soft magnetic materials

Cremer

Löwen

Menzel

2015

Applied Physics Letters

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Embedding magnetic colloidal particles in an elastic polymer matrix leads to smart soft materials that can reversibly be addressed from outside by external magnetic fields. We discover a pronounced nonlinear superelastic stress-strain behavior of such materials using numerical simulations. This behavior results from a combination of two stress-induced mechanisms: a detachment mechanism of embedded particle aggregates as well as a reorientation mechanism of magnetic moments. The superelastic regime can be reversibly tuned or even be switched on and off by external magnetic fields and thus be tailored during operation. Similarities to the superelastic behavior of shape-memory alloys suggest analogous applications, with the additional benefit of reversible switchability and a higher biocompatibility of soft materials.The term "superelasticity" expresses the capability of certain materials to perform huge elastic deformations that are completely reversible 1,2 . It was initially introduced in the context of shape-memory alloys 3-5 . These metallic materials can perform large recoverable deformations due to stress-induced phase transitions. A transition to a more elongated lattice structure accommodates an externally imposed extension. Typically, this transition shows up as a pronounced "plateau-like" regime on the corresponding stress-strain curve. On this plateau, the samples are heterogeneous with domains of already transitioned material. Then, only relatively small additional stress induces a huge additional deformation. Smart material properties are observed 6-9 : upon stress release, shape-memory alloys can reversibly find back to their initial state. They self-reliantly adapt their appearance to changed environmental conditions.In the present letter, we demonstrate that an analogous phenomenological behavior can be realized for a very different class of materials, exploiting different underlying mechanisms. Moreover, we show that during operation the behavior can be reversibly tailored from outside by external magnetic fields. All of this is achieved by employing soft magnetic gels as working materials: colloidal magnetic particles embedded in a possibly swollen elastic polymer matrix 10 . Similarly to magnetic fluids 11-18 , magnetic gels allow to reversibly adjust their material properties by external magnetic fields. In this way, switching the elastic properties 19-23 offers a route to construct readily tunable dampers 24 or vibration absorbers 25 , while the possibility to switch the shape 19,26-28 allows application as soft actuators [29][30][31] . Here, we show that magnetic gels due to the interplay between magnetic and elastic interactions likewise feature superelastic behavior: it is enabled by a detachment mechanism of embedded magnetic particle aggregates and by a reorientation mechanism of magnetic moments. Both mechanisms are stress-induced and rea) Electronic mail: pcremer@thphy.uni-duesseldorf.de b) Electronic mail: menzel@thphy.uni-duesseldorf.de spond to external magnetic fields. Therefore, su...

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confidence: 99%

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confidence: 99%

Tailoring superelasticity of soft magnetic materials

Cremer

Löwen

Menzel

2015

Applied Physics Letters

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“…In this way, we model the physics of one cross-sectional layer of the real system. Since the magnetic particles in the experimental sample are not covalently bound to the polymer matrix [6,7], and since the magnetic moments are perpendicular to the plane, the orientational memory terms in Eq. (1) do not play a role.…”

Section: Figmentioning

confidence: 99%

“…In reality, it can for example be tuned during synthesis by the way of embedding the magnetic particles in the polymer matrix. For instance, rotations of elongated magnetic particles [38] are hindered when compared to spheres, and magnetic particles that are actually part of the network due to chemical surface functionalization [6,7] experience permanent restoring torques under reorientation [8].…”

Section: Impact Of Orientational Memorymentioning

confidence: 99%

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Tunable dynamic response of magnetic gels: Impact of structural properties and magnetic fields

et al. 2014

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Ferrogels and magnetic elastomers feature mechanical properties that can be reversibly tuned from outside through magnetic fields. Here we concentrate on the question how their dynamic response can be adjusted. The influence of three factors on the dynamic behavior is demonstrated using appropriate minimal models: first, the orientational memory imprinted into one class of the materials during their synthesis; second, the structural arrangement of the magnetic particles in the materials; and third, the strength of an external magnetic field. To illustrate the latter point, structural data are extracted from a real experimental sample and analyzed. Understanding how internal structural properties and external influences impact the dominant dynamical properties helps to design materials that optimize the requested behavior.

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Transformer Hydrogels: A Review

Erol

Pantula

Liu

et al. 2019

Adv Materials Technologies

240

211

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Hydrogels, which are hydrophilic soft porous networks, are an important class of materials of broad relevance to bioanalytical chemistry, soft‐robotics, drug delivery, and regenerative medicine. Transformer hydrogels are micro‐ and mesostructured hydrogels that display a dramatic transformation of shape, form, or dimension with associated changes in function, due to engineered local variations such as in swelling or stiffness, in response to external controls or environmental stimuli. This review describes principles that can be utilized to fabricate transformer hydrogels such as by layering, patterning, or generating anisotropy, and gradients. Transformer hydrogels are classified based on their responsivity to different stimuli such as temperature, electromagnetic fields, chemicals, and biomolecules. A survey of the current research progress suggests applications of transformer hydrogels in biomimetics, soft robotics, microfluidics, tissue engineering, drug delivery, surgery, and biomedical engineering.

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Magneto-mechanical coupling in CoFe2O4-linked PAAm ferrohydrogels

Cited by 63 publications

References 28 publications

Tailoring superelasticity of soft magnetic materials

Tailoring superelasticity of soft magnetic materials

Tunable dynamic response of magnetic gels: Impact of structural properties and magnetic fields

Transformer Hydrogels: A Review

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