Development of techniques to compare mechanical properties of reversible hydrogels with spherical, square columnar and ocular lens geometry

Ravi, Nathan; Wan, Kai; Swindle, K. E.; Hamilton, Paul D.; Duan, Guang Hong

doi:10.1016/j.polymer.2006.02.029

Cited by 19 publications

(13 citation statements)

References 31 publications

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“…The number average molecular weight between crosslinks (M c ) was calculated according to following equation: M c ¼ 3rRT/E [39,40]. T is the temperature (298 K) at which the modulus was measured, r is the concentration of methacrylated alginate Table 1 Methacrylation efficiency (%) and actual methacrylation (%) of alginates, and elastic modulus and molecular weight between crosslinks of photocrosslinked alginate hydrogels.…”

Section: Mechanical Testingmentioning

confidence: 99%

Photocrosslinked alginate hydrogels with tunable biodegradation rates and mechanical properties

Jeon¹,

Bouhadir²,

Mansour³

et al. 2009

Biomaterials

529

448

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Section: Mechanical Testingmentioning

confidence: 99%

Photocrosslinked alginate hydrogels with tunable biodegradation rates and mechanical properties

Jeon¹,

Bouhadir²,

Mansour³

et al. 2009

Biomaterials

529

448

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“…Thus, gels with reversible disulfide cross-links have been studied [109][110][111]. Reversible metal-ligand cross-links with a self-repairing function have also been described [112].…”

Section: Chemically Driven Gel Actuatorsmentioning

confidence: 99%

Polymer Gel Actuators: Fundamentals

Calvert

2009

Biomedical Applications of Electroactive Polymer Actuators

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One view of materials development is to search for what materials correspond to empty spaces on a hypothetical multi-dimensional map of the properties of available materials. Following a biomimetic philosophy, for instance, it can be seen that tough ceramics and moldable short fiber composites with high moduli are possible but absent from the list of available synthetic materials. Likewise artificial muscle is missing, where the properties are defined as a developed stress of over 300 kPa, a linear contraction of 25 % and a response time of below one second. Currently dielectric elastomers come closest but have disadvantages [1,2].The actin-myosin muscle system provides the performance target for electroactive polymer actuators [3,4]. The process is driven chemically by the energy change from hydrolysis of the polyphosphate bond as ATP (adenosine triphosphate) binds to myosin and is converted to ADP (adenosine diphosphate) and phosphate. A simple chemical analogy suggests that muscle-like gels should be feasible but it is now clear that the task is much harder than it seems.Early work on gel actuation by Katchalsky-Katzir demonstrated that engines could be built using the chemical energy in diluting a lithium bromide solution to drive contraction and expansion of a collagen belt [5]. In essence, the collagen expands to take up the salt solution or contract to exclude the water. This change is both a molecular conformation change and a volume change. Other chemically driven gels, for instance polyacrylic acid fibers [6] which respond to a pH change, also rely on a solubility change giving rise to a volume change.

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“…While it is clear that for a constant applied load, D will increase as fruits soften, the basis for using D rather than the standard material property of bulk elastic modulus (E, expressed in MPa, ASAE 2003) has not been presented. For the compression of a spherical object between two parallel plates, D is inversely proportional to both the two-thirds power of E, as well as to the cube root of the sphere radius, as shown in the Hertz equation (e.g., Ravi et al 2006.). Thus, E and D are inversely related, and a linear decrease in E over time, which would indicate a steady and progressive softening, may correspond to a strongly curvilinear increase in D over time, depending on the numerical range exhibited by E and D. Since Coombe and Bishop (1980) reported that the earliest evidence of ripening in grape was an increase in the rate of change in D, it is important to verify whether this is also exhibited in E. This is particularly important for studies of berry development because an increase in D has been used to identify the onset of ripening (termed 'veraison' in viticulture), and this time point has been used as the developmental basis for investigations of ripeningrelated changes in gene expression (Tattersall et al 1997;Davies and Robinson 2000b).…”

Section: Introductionmentioning

confidence: 99%

Mesocarp cell turgor in Vitis vinifera L. berries throughout development and its relation to firmness, growth, and the onset of ripening

Thomas

Shackel

Matthews

2008

Planta

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Vitis vinifera L. berries are non-climacteric fruit that exhibit a double sigmoid growth pattern and dynamic changes in gene expression, cell metabolism, and water relations at the onset of ripening. The cell-pressure probe was utilized to examine the relationships of turgor pressure (P) in mesocarp cells to growth, sugar accumulation, and fruit softening during development. In replications utilizing three different varieties, mesocarp cell P demonstrated a consistent pattern of a relative mid-range P early in development, followed by an increase to a maximum of about 0.35 MPa, and a subsequent rapid decline before ripening to less than 0.1 MPa. Fruit "apparent elastic modulus" (E, units of MPa), was introduced as a standard measure to describe ripening-related softening. E changed dynamically and synchronously with P during development and in response to water deficits for fruit grown in greenhouse and field conditions. Thus, E and P were positively and linearly related. Sugar accumulation did not increase significantly until P had declined to less than 0.1 MPa. The results suggest that P is an important determinant of fruit softening and that P decreases in conjunction with many of the physiological and gene expression changes that are known to occur at the onset of ripening.

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Development of techniques to compare mechanical properties of reversible hydrogels with spherical, square columnar and ocular lens geometry

Cited by 19 publications

References 31 publications

Photocrosslinked alginate hydrogels with tunable biodegradation rates and mechanical properties

Photocrosslinked alginate hydrogels with tunable biodegradation rates and mechanical properties

Polymer Gel Actuators: Fundamentals

Mesocarp cell turgor in Vitis vinifera L. berries throughout development and its relation to firmness, growth, and the onset of ripening

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