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Dissertation
Fabrication of highly stretchable, moldable and injectable hydrogel and its applications in strain sensing and drug delivery
Doctor of Philosophy (Ph.D.), Drexel University
Sep 2019
DOI:
https://doi.org/10.17918/00000961
Abstract
Stretchable and tough hydrogels have attracted a lot of attention due to their unique properties and great potential in applications including wound healing, drug delivery, tissue culture, etc. They can also be paired with electronic components to create artificial skin, wearable electronics, and patches. Only a few hydrogels have been synthesized that have exceptional stress to strain mechanical properties. In the field of hydrogels it is difficult to make a gel with both high strength and stretchability because the crosslinks that form the structure of the network are usually either static and irreversible or dynamic and reversible. To circumvent this limitation, the use of hybrid double network (DN) hydrogels has become prominent. These hybrid DN gels have greatly improved the dynamic mechanical properties possible for hydrogels and have open the door for new applications of these soft materials. Additionally, these high water weight gels (almost 90wt% in most cases) have been shown to have the potential to serve as highly conductive materials due to doping with conductive species such as salts, 2D materials and nanocomposites. In particular, one application that stands out for the use of these special class of hydrogels is strain sensing, which is used in artificial tissues and soft robotics. An ideal strain sensor should be stable and consistent over various stretching lengths, as well as, show linearity in sensitivity over discrete windows of strain. In this work, we optimized several parameters to produce gelatin/polyacrylamide hydrogels with superior mechanical properties. The highest water content gel was capable of withstanding strains of 5000% before failure and another calcium ion doped gel gave an ultimate tensile strength of 1.71MPa. These DN gels also demonstrated a broad range of strain sensing from 0-3000% for various concentrations of metal ions. The sensitivity of the best strain sensor was measured using the gauge factor (GF) and gave large values over 3 discrete windows of strain. These GF values ranged from 1.63-6.85 for strains of 0-2100%. The sensors were also stable over continuous stretching cycles, demonstrating their good reliability for any application. Lastly, these gels were also shown to be easily injected into molds where they effectively changed shape to several alphabetical letters and maintained similar properties prior to remolding. The hybrid hydrogel can also be used as drug carriers for release purpose. We presented the high drug loading efficiency with controlled release rate in vitro on the simulated human skin by using a franz diffusion device. Cytotoxicity study on microphage cell line RAW 264.7 indicates that the release medium and the biodegradation products of the hybrid hydrogel is nontoxic to microphage cells at the concentration as used, which further indicates the hybrid hydrogel serving as a promising candidate working as scaffold for drug delivery.
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Details
- Title
- Fabrication of highly stretchable, moldable and injectable hydrogel and its applications in strain sensing and drug delivery
- Creators
- Zhen Qiao
- Contributors
- Haifeng Ji (Advisor)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xiii, 154 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- College of Arts and Sciences; Chemistry; Drexel University
- Other Identifier
- 991014695545204721