We describe herein a nanocellulose-alginate hydrogel suitable for 3D printing. The composition of the hydrogel was optimized based on material characterization methods and 3D printing experiments, and its behavior during the printing process was studied using computational fluid dynamics simulations. The hydrogel was biofunctionalized by the covalent coupling of an enhanced avidin protein to the cellulose nanofibrils. Ionic cross-linking of the hydrogel using calcium ions improved the performance of the material. The resulting hydrogel is suitable for 3D printing, its mechanical properties indicate good tissue compatibility, and the hydrogel absorbs water in moist conditions, suggesting potential in applications such as wound dressings. The biofunctionalization potential was shown by attaching a biotinylated fluorescent protein and a biotinylated fluorescent small molecule via avidin and monitoring the material using confocal microscopy. The 3D-printable bioactivated nanocellulose-alginate hydrogel offers a platform for the development of biomedical devices, wearable sensors, and drug-releasing materials.

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To better understand the complex system of wet foams in the presence of cellulosic fibers, we investigate bubble−surface interactions by following the effects of surface hydrophobicity and surface tension on the contact angle of captive bubbles. Bubbles are brought into contact with model silica and cellulose surfaces immersed in solutions of a foaming surfactant (sodium dodecyl sulfate) of different concentrations. It is observed that bubble attachment is controlled by surface wetting, but a significant scatter in the behavior occurs near the transition from partial to complete wetting. For chemically homogeneous silica surfaces, this transition during bubble attachment is described by the balance between the energy changes of the immersed surface and the frictional surface tension of the moving three-phase contact line. The situation is more complex with chemically heterogeneous, hydrophobic trimethylsilyl cellulose (TMSC). TMSC regeneration, which yields hydrophilic cellulose, causes a dramatic drop in the bubble contact angle. Moreover, a high interfacial tension is required to overcome the friction caused by microscopic (hydrophilic) pinning sites of the three-phase contact line during bubble attachment. A simple theoretical framework is introduced to explain our experimental observations.

For the first time, continuous ultrasound-assisted tubular crystallizer dynamics has been studied in pilot scale operation. It is vital to understand the process dynamics for continuous crystallizers as robust crystallization processes are developed. The mixing time using tracer impulses and experimental continuous crystallization runs to understand the performance of process variables, with focused beam reflectance measurement (FBRM), process video microscope measurements, and off-line particle size analytics, is reported. The model system was phthalic acid crystallization from water. The effects of ultrasound power and residence time on the crystallization dynamics and on the product crystal size distribution (CSD) were studied. The use of ultrasound was found to be vital in the crystallization operations in order to prevent pipe clogging. It was shown that an increase in ultrasound power improves mixing in tubular reactors, and it decreases the product CSD, most probably due to nucleation. Also, an increase in residence time decreases the CSD due to an increase in ultrasound irradiation time during crystal growth. The video-microscope-based relative backscatter index signal was more sensitive to crystallization startup in this system in comparison to FBRM chord lengths. The continuous crystallization process dead time was found to follow fluid mixing dynamics by monitoring relative backscatter index signals as the flow rate and US power were increased. The steady-state crystallization conditions were found to take more than 2 reactor residence times on the basis of continuous crystallization experiments.