Bipin Kumar

Bio: Bipin Kumar is an academic researcher from Indian Institute of Technology Delhi. The author has contributed to research in topics: Bandage & Compression Bandage. The author has an hindex of 13, co-authored 74 publications receiving 553 citations. Previous affiliations of Bipin Kumar include Hong Kong Polytechnic University & Indian Institutes of Technology.

A facile approach to fabricate a UV/heat dual-responsive triple shape memory polymer

Abstract: In the present work, a facile approach was employed to fabricate a UV/heat dual-responsive triple shape memory polymer (SMP) by simply mixing Zn(Mebip)2(NTf2)2, a metallosupramolecular unit formed by coordinating 2,6-bis(N-methyl-benzimidazolyl)-pyridine (Mebip) ligands to zinc di[bis(trifluoromethylsulfonyl)-imide] (Zn(NTf2)2), into one part of epoxy resin. Dissimilar to previously reported UV sensitive SMPs with sophisticated molecular structure and relatively poor mechanical properties, the advantage of this approach is that the UV-sensitivity was simply achieved by employing Zn(Mebip)2(NTf2)2, a UV-heat transfer compound, into the polymer matrix without significant sacrifice of thermal and mechanical properties. Also thanks to the light–heat transfer nature of Zn(Mebip)2(NTf2)2 and segmented material structure, the resulting polymer displayed UV sensitivity to the composite part, while leaving the shape of the neat SMP part unchanged under the UV source (solely thermal sensitive). Thus the resulting composite displayed an excellent UV and heat selective localized triple shape memory effect.

Effect of material and structure of compression bandage on interface pressure variation over time.

Abstract: BackgroundCompression bandage consists of fibrous materials which are viscoelastic in nature due to which the internal stress developed in the compression bandage under wrapped position may decay over time. The viscoelastic behaviour of a textile material depends on the fibre type as well as on its structure, and hence these factors could play a prominent role in interface pressure variation over time.ObjectiveTo explore the influence of different materials and varying structures on the interface pressure profile generated by the bandages over time during static state of the limb.MethodThe material and construction of several compression bandages were engineered first and based on that different knitted bandages were prepared using several yarns (cotton, viscose, polyethylene terephthalate [PET], cotton-Lycra and PET-Lycra) and varying thread density in the structure. Three important factors, namely the material type, the applied tension and the tightness of the structure, were selected to examine their i...

Stress-memory polymeric filaments for advanced compression therapy

Abstract: Shape memory polymers are stimulus responsive smart materials that can be applied in several forms such as films, fibers, and foams for a wide range of applications. Novel stress-memory behavior at a fiber level is yet to be uncovered, which would be favorable to control stress in the broad horizon of smart materials for numerous functions. In this work, a semi-crystalline segmented polyurethane was synthesized to prepare filaments/fibres and films. A rational experimental design was established and the stress-memory behavior of both the films and filaments was systematically studied for comparison. Tensile stress-memory programming was performed at three strain levels (20%, 40%, and 60%) to record the memory stress response as a function of temperature with time. The characterization of the thermal and mechanical properties of the stress-memory programmed specimens has objectively proven the reason behind the higher stress response in the filaments than in the films. Melt spinning has induced perfect crystallization with ordered polymer packing and enabled maximum memory stress to be retrieved in the filaments. The evolution of memory stress follows a linear trend with an increase in strain and temperature (r2 = 0.91–1). In addition, pressure related studies were also carried out for smart filament integrative fabrics to realize stress-memory behavior. This unprecedented and novel approach of unveiling the memory behavior specifically at the filament level will enable material scientists to comprehend the fundamental aspects for precise optimization and control of memory stress in smart structures for applications such as compression stockings that require stimuli responsive force.

A Review of Shape Memory Polymers and Composites: Mechanisms, Materials, and Applications

Abstract: Over the past decades, interest in shape memory polymers (SMPs) has persisted, and immense efforts have been dedicated to developing SMPs and their multifunctional composites. As a class of stimuli-responsive polymers, SMPs can return to their initial shape from a programmed temporary shape under external stimuli, such as light, heat, magnetism, and electricity. The introduction of functional materials and nanostructures results in shape memory polymer composites (SMPCs) with large recoverable deformation, enhanced mechanical properties, and controllable remote actuation. Because of these unique features, SMPCs have a broad application prospect in many fields covering aerospace engineering, biomedical devices, flexible electronics, soft robotics, shape memory arrays, and 4D printing. Herein, a comprehensive analysis of the shape recovery mechanisms, multifunctionality, applications, and recent advances in SMPs and SMPCs is presented. Specifically, the combination of functional, reversible, multiple, and controllable shape recovery processes is discussed. Further, established products from such materials are highlighted. Finally, potential directions for the future advancement of SMPs are proposed.

Array signal processing

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