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Shape Retention (shape + retention)

Distribution by Scientific Domains

Polymers and Materials Science	50%

Selected Abstracts

Electromechanical reshaping of septal cartilage,,

THE LARYNGOSCOPE, Issue 11 2003
Ki-Hong Kevin Ho BS
Abstract Objectives: This study describes the process of tissue electroforming and how shape changes in cartilage can be produced by the application of direct current (DC). The dependence of shape change on voltage and application time is explored. Study Design: Basic investigation using ex vivo porcine septal cartilage grafts and electromechanical cartilage deformation focused on development of a new surgical technique. Methods: Uniform flat porcine nasal septal cartilage specimens were mechanically deformed between two semicircular aluminum electrodes. DC current was applied to establish charge separation and electrical streaming potential. Voltage (0,3.5 V) and application time (0,5 minutes) were varied. Shape change was measured, and shape retention was calculated using analytic representation. The effect of the direction of applied current on shape change was evaluated by switching the polarities of electrodes and using parameters of 0 to 5.5 V and 5 minutes. Temperature during reshaping was monitored with a thermocouple, and surface features were evaluated using light microscopy. Results: Reshaped specimen demonstrated mechanical stability similar to native cartilage tissue. Shape retention strongly correlated with increasing voltage and application time. Only a small current (<0.1 A) through the tissue was measured. Temperature change was less than 2°C during electroforming, suggesting that electroforming likely results from some nonthermal mechanisms. Surface features indicated that electrodeposition may occur depending on electrode material and magnitude of the applied voltage. Conclusions: These findings demonstrate that cartilage can be reshaped through the process we have described as "electroforming" by generating intrinsic differences in charge separation with negligible heat production. [source]

Designing Polymers to Enable Nanoscale Thermomechanical Data Storage

ADVANCED FUNCTIONAL MATERIALS, Issue 8 2010
B. Gotsmann
Abstract Nanomechanics has been slow in entering nanotechnology because of extreme conditions resulting from scaling. This is an issue in particular for polymers, although widely used in macroscale applications. Highly repetitive nanoscale deformation cycling in combination with excellent shape retention and thermal stability is demonstrated. While generic principles described are pertinent to a range of applications, this demonstration is made on the example of polymer media in high-density data storage. The information, represented as indents, is written and erased using a heated tip. A high-performance polymer with a flexible aryletherketone backbone is designed with phenylethynyl crosslink chemistry. After optimization of crosslink density and topology, unprecedented performance is achieved in all relevant metrics. Demonstrations of endurance and retention are performed at 1 Tb in,2 density, showing 108 write cycles using the same tip, 103 erase cycles and 3,×,105 read cycles of the media, and extrapolated to 10 years of retention at 85,°C. [source]

Celite-mediated linking of polyurethane block copolymers and the impact on the shape memory effect

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010
Yong-Chan Chung
Abstract Celite, a porous inorganic material with enormous surface area and hydroxyl groups on the surface, was used as a cross-linker of polyurethane (PU) copolymer chains to improve its shape memory and mechanical properties. PU copolymers with different Celite contents were prepared and characterized by IR, DSC, and universal testing machine. The glass transition temperature of PU copolymers was maintained around 20°C independent of Celite content. The shape memory and mechanical properties were dependent on when Celite was added during the polymerization reaction. The reaction in which Celite was added at the middle stage of polymerization showed the best shape memory and mechanical properties. The best shape recovery of PU was found at 0.3 wt % Celite and increased to 97% even after the third cycle. Likewise, the shape retention also maintained a remarkable 86% after three cycles. The reasons underlining the high shape recovery and shape retention by adopting Celite as a cross-linker are discussed in this article. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]