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Electrospun Nanofibrous Materials as Stimuli-Responsive Polymerized Hydrogels
Stimuli-responsive polymer gels possess unique properties such as multifold change of volume in response to various stimuli, resemblance of soft biological tissues, and ability to operate in wet environments. Nearly unlimited possibilities of chemical modification guarantee that an advanced gel-based platform can be modified for sensors, muscle-type actuators, and autonomous intelligent structures for aquatic and biomedical applications. However, the response rates of common bulk gels are too slow and their mechanical robustness is not sufficient for many applications. These problems may be resolved, if gels are prepared in nanofibrous form. In this study, nanofilamentary hydrogels (NFGs) were fabricated by electrospinning followed by thermal crosslinking. These gels were characterized and compared with rod-like bulk hydrogels. Ultrafast response rates and improved water retention in NFGs were demonstrated by studying swelling kinetics, with insignificant reduction of the degree of equilibrium swelling. Highly repeatable, reversible, rubber-like non-linear load-strain behavior with low hysteresis was strongly pH-dependent. Unusual intrinsic anisotropic swelling behavior and unique cross-over of load vs. length curves were observed and explored. Such unusual behavior was not reported for other hydrogels nor predicted by theories of gel swelling. A novel sample preparation and testing protocols were developed and used to study deformation of single gel nanofibers under dry and humid conditions. Size effects on the mechanical properties were evaluated and possibility of simultaneous increase in strength and toughness in fine nanofibers was demonstrated. Bulk hydrogels reinforced with NFGs were fabricated and studied. Finally, nanofilamentary drug carriers were produced and control of their morphology and drug loading as well as stimulus-dependent drug release were demonstrated. Nanofilamentary hydrogels with controlled structure and useful properties, such as significantly increased response rate, intrinsic mechanical anisotropy, improved size-dependent mechanical properties, and sensitivity to environmental stimuli, open up unique possibilities for advanced applications in smart sensors, actuators, and biomedicine.
Mechanical engineering|Materials science
Jahan, Kazi Israt, "Electrospun Nanofibrous Materials as Stimuli-Responsive Polymerized Hydrogels" (2019). ETD collection for University of Nebraska - Lincoln. AAI22616950.