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Influence of Chemical Composition on the Adhesion of Hydrogels in Dry and Underwater Conditions Megan Yankulov, Saranshu Singla, Amal Narayanan, Abraham Joy, Ali Dhinojwala Department of Polymer Science, The University of Akron, Akron OH 44325 Email: [email protected] In the production and use of biomedical devices, wound dressings, and bone regeneration, underwater adhesion is essential to its effectivity. However, adhesion is limited in underwater environments because water molecules will penetrate and create gaps between surfaces and cause debonding at the interface. Hydrogels have demonstrated superior adhesion in underwater environments, despite their chemical composition, which is surprising. 4,5 To investigate this, polyethylene-glycol dimethacrylate (PEGDMA) and 2-hydroxyethyl methacrylate (HEMA) hydrogels were synthesized. Adhesion measurements were done using JKR geometry to test the adhesion of hydrogels in dry and wet conditions. Sum Frequency Generation Spectroscopy (SFG) was used to examine interaction strength and chemical composition at the interface. Our results will provide insights into designing hydrogels for wet adhesion applications. 1. Hydrogels demonstrated significantly lower adhesion in underwater environments, regardless of chemical composition. 2. HEMA-PEGDMA contained increased dry adhesion through pull off force values when compared to PEGDMA. 3. SFG analysis indicated presence of hydrocarbons as well as hydroxyl signals at the interface. 4. Future work will be focused on conducting additional SFG scans, as well as studying the mechanical properties of the hydrogel utilizing rheology measurements. Motivation Experimental Design 1. Kaur, S.; Narayanan, A.; Dalvi, S.; Liu, Q.; Joy, A.; Dhinojwala, A. Direct Observation of the Interplay of Catechol Binding and Polymer Hydrophobicity in a Mussel-Inspired Elastomeric Adhesive. ACS Central Science 2018, 4, 1420-1429. 2. Kurian, A.; Prasad, S.; Dhinojwala, A. Direct Measurement of Acid-Base Interaction Energy at Solid Interfaces. Langmuir 2010, 26, 17804-17807. 3. Li, J.; Celiz, A. D.; Yang, J.; Yang, Q.; Wamala, I.; Whyte, W.; Seo, B. R.; Vasilyev, N. V.; Vlassak, J. J.; Suo, Z.; Mooney, D. J. Tough adhesives for diverse wet surfaces. Science 2017, 357, 378-381. 4. Yang, J.; Bai, R.; Chen, B.; Suo, Z. Hydrogel Adhesion: A Supramolecular Synergy of Chemistry Topology and Mechanics. Adv. Funct. Mater. 2019, 1-27. 5. Yi, H.; Lee, S.; Seong, M.; Kwak, M.; Jeong. Bioinspired reversible hydrogel adhesives for wet and underwater surfaces. Jour. Mat. Chem. 2018, 8064-8070. Results and Discussion Background Conclusions and Future Work References Acknowledgements Hydrogels are composed of over 80% water. 4 This causes their superior underwater adhesion to be surprising, as water interferes with bonds between adhesive and substrate. However, numerous studies have indicated increased adhesion in underwater environments. 3,4 -4 -3 -2 -1 0 1 2 3 4 5 0 100 200 300 400 500 600 700 800 900 Force (mN) Time (secs) Force vs Time Dry PEGDMA slate -2.5 -2 -1.5 -1 -0.5 0 0.5 0 100 200 300 400 500 600 700 800 Force (mN) Time (seconds) Force vs Time Underwater PEGDMA slate Repeat 1 Repeat 2 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 0 20 40 60 80 100 120 140 Pull off force (mN) Time (minutes) PEGDMA slate Pull Off Force vs Time -1 -0.5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 Average Pull Off Force (mN) Average Pull Off Force of PEGDMA Lens in Dry and Wet Conditions Lens 3 Dry Lens 3 Wet Lens 4 Dry Lens 4 Wet Lens 5 Dry Lens 5 Wet 0 1 2 3 4 5 6 7 8 9 Pull Off Force (mN) Average Pull Off Force of HEMA-PEGDMA in Dry and Wet Conditions Dry Conditions 2mN preload Wet Conditions 2 mN preload Dry Conditions 4.0 mN preload Wet Conditions 4.0 mN preload Dry Conditions 6.0 mN preload Wet Conditions 6.0 mN preload We would like to thank the National Science Foundation (DMR# 1659531) for the generous financial support. Many thanks to my laboratory instructors Saranshu Singla, Amal Narayanan, Dr. Ali Dhinojwala and all colleagues in Dr. Dhinojwala’s group for their helpful advice. Hydrogels Show Promise in Tissue Repair and Wound Dressings 3 Alginate-polyacrylamide hydrogels were synthesized with various bridging polymers and analyzed for their potential in tissue repair and wound dressings. Results indicate hydrogels maintained high adhesion to various tissues in wet environments, were biocompatible, and diminished blood loss in wound dressing simulations. Synthesis Adhesion (PEGDMA) (HEMA) Johnson Kendall Roberts Geometry (JKR) Bulk water Interface -8.000 -6.000 -4.000 -2.000 0.000 2.000 4.000 6.000 8.000 0 200 400 600 800 Force (mN) Time (seconds) HEMA-PEGDMA Lens 2 Force vs Time in Dry Conditions Preload force Equilibration time Pull off force Detachment Maximum pull off force was measured to indicate adhesive strength of the hydrogel in slate and lens form. Hydrogel slates were difficult to cut and obtain a flat surface. Lens work better. Hydrogels Demonstrate Significantly Decreased Underwater Adhesion Spectroscopy Air Scan Dry Contact Wet Contact Air Scan Dry Contact D2O Scan PEGDMA Lens were analyzed in dry and wet contact. Further experiments were performed utilizing deuterium oxide to differentiate the water signals from sapphire surface OH groups. The radius of each lens was measured to provide similar sized lens in each adhesion test performed. Hydrogel Photopolymerization by UV irradiation was utilized to create the following hydrogels: Kaur, et al. ACS Central Science 2018,4,1420-1429 Kaur, et al. ACS Central Science 2018,4,1420-1429 https://orientalgrouplk.com/customer-erudition https://www.dkfindout.com/us/human-body/skeleton-and-bones/living-bone/ https://kikgel.com.pl/produkty/neoheal/ https://newatlas.com/temperature-controlled-hydrogel-movement/38865/ Spectroscopy
