In this study, a rapid fabrication method was developed to prepare hydrogel structures with high mechanical strength and low attenuation coe cient for ultrasound scanning. Poly acrylic acid (PAA) hydrogel was rst prepared via a free radical polymerization approach. To shorten the process time (~ 30 minutes in water bath), microwave heating was applied to facilitate the reaction and reduce the reaction time down to 80 seconds. The produced hydrogels showed excellent elasticity but had a low compressive strength of 100 kPa. To further enhance the mechanical strengths of PAA hydrogels, cellulosenanocrystals (CNCs) were added to the precursor solution. After the microwave assisted crosslinking process, the compressive strength of the hydrogel increased to 350 kPa. Moreover, the ultimate compressive strain was enhanced from 60% to 80% with great recoverability. The PAA/CNC hydrogel has a great ultrasound trnansimission for high-quality ultrasound images comparable to conventional liquid hydrogels. To demonstrate the feasibility of the PAA/CNC hydrogel in ultrasonic medical applications, a customized ultrasound probe coat was created with a 3D printed mold and practically used in the ultrasound scanning process.

In this study, a novel hydrogel preparation method is developed to formulate a 3D printable hydrogel with low swelling ratio for bio-medical scaffold. Nanocellulose fibrils is first oxidized to synthesize dialdehyde cellulose nanocrystal (DAC). The aldehyde groups on DAC can crosslink with laponite nanoclay via an esterification reaction. The mechanism between the two materials through aldehyde and hydroxyl groups is further confirmed by FTIR results. To optimize the printability and printing quality of the prepared hydrogels, the rheological properties of the gels are carefully examined to understand the shear thinning effect and the thixotropic responses. An optimal hydrogel composition of 6 wt% Laponite and 1 wt% DAC shows the best results to accurately print 3D structures with a nozzle dispenser. The printed gel structures show high mechanical strength and low swelling effect without complicated after-treatment steps. Several examples are also demonstrated to show the structural stability, accuracy, and cell viability of the printed hydrogel structures for potential in 3D bioprinting applications.

In this study, a rapid fabrication method was developed to prepare hydrogel structures with high mechanical strength and low attenuation coefficient for ultrasound scanning. Poly acrylic acid (PAA) hydrogel was first prepared via a free radical polymerization approach. To shorten the process time (~ 30 minutes in water bath), microwave heating was applied to facilitate the reaction and reduce the reaction time down to 80 seconds. The produced hydrogels showed excellent elasticity but had a low compressive strength of 100 kPa. To further enhance the mechanical strengths of PAA hydrogels, cellulosenanocrystals (CNCs) were added to the precursor solution. After the microwave assisted crosslinking process, the compressive strength of the hydrogel increased to 350 kPa. Moreover, the ultimate compressive strain was enhanced from 60% to 80% with great recoverability. The PAA/CNC hydrogel has a great ultrasound trnansimission for high-quality ultrasound images comparable to conventional liquid hydrogels. To demonstrate the feasibility of the PAA/CNC hydrogel in ultrasonic medical applications, a customized ultrasound probe coat was created with a 3D printed mold and practically used in the ultrasound scanning process.