Preparation And Properties Of Functional Hydrogel Coatings Based On Gelatin Methacryloyl(GelMA)

Hydrogels are soft and water-rich materials with three-dimensional crosslinking networks,which have been widely investigated owing to their appealing function properties such as freezing-tolerance,low-friction,and high stretchability.Besides,most hydrogels have been applied in the field of biomedical engineering due to their biodegradability,antibacterial property,and biodegradability.However,hydrogel coatings are crucial in the fields of soft robotics,bioengineering,and biomedical devices as they enable the combination of substrate properties with hydrogel functionalities.Nevertheless,the interfacial adhesion strength,underwater stability,and mechanical properties of hydrogel coatings should be further improved,and their drag-reducing performance should be further analyzed.Therefore,this thesis prepares functional hydrogel coatings,and develops their applications in tuning mechanical properties,anti-freezing,drug release,and drag-reducing.The specific research contents are listed as follows:(1)A mechanically tunable gelatin methacryloyl-based hydrogel coating is developed via a scalable UV-curing strategy combining with post-immersing treatment in sodium citratewater-glycerol solution.This paper systematically investigates the mechanical properties,interfacial adhesion mechanism,and engineering applications of the hydrogel coating.The hydrogel coating shows mechanically tunable property by changing the soaking time or the concentration of sodium citrate.The compression modulus of the hydrogel enhances by 15 times after soaking in sodium citrate-water-glycerol for 120 min.Besides,the anti-freezing property endows the hydrogel coating with low-temperature(e.g.-40℃)flexibility.The hydrogel coating is transparent with the transmittance over 80%within the visible light region and exhibits long-term stability(over 60 days at 25 ℃ and 40%related humidity).(2)To enhance the underwater stability and interfacial adhesion strength of the hydrogel coating,a durable,substrate-independent,and underwater stable GelMA composite hydrogel coating is developed.The silane with unsaturated double bond is grafted onto the substrate of co-deposited polydopamine and polyethylenimine.Then,the hydrogel coating is covalently immobilized on the substrate via ultraviolet curing.This paper systematically investigates the adhesion strength,stability,drug release,antibacterial properties,and biocompatibility of the hydrogel coating.The hydrogel coating shows excellent stability under extreme condition of ultrasonic treatment for 1 h(400 W of ultrasonic power)or underwater shearing for 14 d(400 rpm).Besides,drug release and inhibition ring tests show that hydrogel coating can control drug release rate in the range of 70%-95%by changing the PEGDA content.Moreover,the obtained hydrogel coating shows favorable biocompatibility and mechanically tunable properties,indicating its broad potential for applications in biomedical and clinical fields.(3)The fabricated hydrogel coating sample can reduce friction at the interface,which is important for the future study of lubrication at the interface between rigid implants and soft tissues.This paper establishs a friction experimental setup to investigate the friction behavior of the prepared hydrogel coating.The obtained hydrogel coating shows good lubrication property with a friction coefficient less than 0.001.METAC have high hydrophilicity,which can increase the water content of the hydrogel coating and improve the lubrication performance of the hydrogel coating by forming more layers of water molecules on its surface.Increasing PEGDA content can increase the crosslinking density of hydrogel network,reduce wear of the hydrogel coating and improve durability of the hydrogel coating.The friction behavior of the hydrogel coating is influenced by the normal load and shear velocity.The friction coefficient of the hydrogel coating decreases rapidly with the increase of the normal load and then remains constant after a short period.As the shear velocity increases from medium to high speed,the friction coefficient initially decreases and then increases.