Developing a transcatheter injectable nanoclay- alginate gel for minimally invasive procedures.

Shear-thinning materials have held considerable promise as embolic agents due to their capability of transition between solid and liquid state. In this study, a laponite nanoclay (NC)/alginate gel embolic agent was developed, characterized, and studied for transcatheter based minimally invasive procedures. Both NC and alginate are biocompatible and FDA-approved. Due to electrostatic interactions, the NC/alginate gels exhibit shear-thinning properties that are desirable for transcatheter delivery. The unique shear-thinning nature of the NC/alginate gel allows it to function as a fluid-like substance during transcatheter delivery and as a solid-like embolic agent once deployed. To ensure optimal performance and safety in clinical applications, the rheological characteristics were thoroughly investigated to optimize the mechanical properties of the NC/alginate gel, including storage modulus, yield stress/strain, and thixotropy. To improve physicians' experience and enhance the predictability of gel delivery, a combination of experimental and theoretical approaches was used to assess the injection force required for successful delivery of the gel through clinically employed catheters. Overall, NC/alginate gel exhibited excellent stability and tunable injectability by optimizing the composition of each component. These findings highlight the gel's potential as a robust embolic agent for a wide range of minimally invasive procedures.

Chitosan-nanoclay embolic material for catheter-directed arterial embolization.

Minimally invasive transcatheter embolization is a common nonsurgical procedure in interventional radiology. It is used for the deliberate occlusion of blood vessels for the treatment of disease or injured vasculature, including vascular malformation and malignant/benign tumors. Here, we introduce a gel embolic agent comprising chitosan nanofibers and nanoclay with excellent catheter injectability and tunable mechanical properties for embolization. The properties of the gel were optimized by varying the ratio between each individual component and also adjusting the total solid content. The rheological studies confirm the shear thinning property and gel nature of the developed gel as well as their recoverability. Injection force was measured to record the force required to pass the embolic gel through a clinically relevant catheter, evaluating for practicality of hand-injection. Theoretical predicted injection force was calculated to reduce the development time and to enhance the physician's experience. The stability of occlusion was also tested in vitro by monitoring the pressure required to displace the gel. The engineered gels exhibited sterility, hemocompatibility and cell biocompatibility, highlighting their potential for transcatheter embolization.

Lightweight 3D Graphene Metamaterials with Tunable Negative Thermal Expansion.

In this study, a 3D graphene metamaterial (GM) showing negative thermal expansion is prepared using a strategy of hyperbolically oriented freezing under a dual temperature gradient along orthogonal directions after the π-π stacking-derived assembly of 2D graphene sheets. As the fundamental construction element of the 3D GM, the graphene sheet displays anomalous shrinking deformation with a thermal expansion coefficient of (-6.12 ± 0.28) × 10-6 that is triggered by thermally induced out-of-plane vibrations of the CC bonds. A combination of numerical simulations and experimental investigations validates that anomalous negative thermal expansion (NTE) behavior can be effectively delivered to scalable 3D GM candidates at larger dimensions beyond the basic 2D graphene sheets at the microscale. The multiscale design and optimization of the structural characterization of the 3D GM further realize the desirable regulation of the NTE performance with the NTE coefficient ranging from negative ((-7.5± 0.65) × 10-6 K-1 ) to near-zero values ((-0.8 ± 0.25) × 10-6 K-1 ). This is attributed to the NTE-derived release regulation of the primary stress/strain of the microstructure, and the 3D GM exhibits high thermal stability while preserving the desirable structural robustness and fatigue resistance under thermo-mechanical coupling conditions. Therefore, this 3D GM offers promising potential for applications as protective skin, thermal actuator, smart switcher, and packing filler.

3D Printed MXene Aerogels with Truly 3D Macrostructure and Highly Engineered Microstructure for Enhanced Electrical and Electrochemical Performance.

Assembling 2D materials such as MXenes into functional 3D aerogels using 3D printing technologies gains attention due to simplicity of fabrication, customized geometry and physical properties, and improved performance. Also, the establishment of straightforward electrode fabrication methods with the aim to hinder the restack and/or aggregation of electrode materials, which limits the performance of the electrode, is of great significant. In this study, unidirectional freeze casting and inkjet-based 3D printing are combined to fabricate macroscopic porous aerogels with vertically aligned Ti3 C2 Tx sheets. The fabrication method is developed to easily control the aerogel microstructure and alignment of the MXene sheets. The aerogels show excellent electromechanical performance so that they can withstand almost 50% compression before recovering to the original shape and maintain their electrical conductivities during continuous compression cycles. To enhance the electrochemical performance, an inkjet-printed MXene current collector layer is added with horizontally aligned MXene sheets. This combines the superior electrical conductivity of the current collector layer with the improved ionic diffusion provided by the porous electrode. The cells fabricated with horizontal MXene sheets alignment as current collector with subsequent vertical MXene sheets alignment layers show the best electrochemical performance with thickness-independent capacitive behavior.

Bioinspired Manufacturing of Aerogels with Precisely Manipulated Surface Microstructure through Controlled Local Temperature Gradients.

The freeze casting process has been widely used for fabricating aerogels due to its versatile and environmentally friendly nature. This process offers a variety of tools to tailor the entire micropore morphology of the final product in a monolithic fashion through manipulation of the freezing kinetics and precursor suspension chemistry. However, aerogels with nonmonolithic micropore morphologies, having pores of various sizes located in certain regions of the aerogels, are highly desired by certain applications such as controlled drug-delivery, bone tissue engineering, extracellular simulation, selective liquid sorption, immobilized catalysts, and separators. Furthermore, aerogels composed of micropores with predesigned size, shape, and location can open up a new paradigm in aerogel design and lead to new applications. In this study, a general manufacturing approach is developed to control the size, shape, and location of the pores on the aerogel surface by applying a precise control on the local thermal conductivity of the substrate used in a unidirectional freeze casting process. With our method, we created patterned low and high thermal conductivity regions on the substrate by depositing patterned photoresist polymer features. The photoresist polymer has a much lower thermal conductivity, which resulted in lower cooling/freezing rates compared to the silicon substrate. Patterned thermal conductivity created a designed temperature profile yielding to local regions with faster and slower freezing rates. Essentially, we fabricated aerogels whose micropore morphology on their surface was a replica of the patterned substrates in terms of size and location of the micropores. Using the same substrates, we further showed the possibility of 3D printed aerogels with precisely controlled, surface micropore morphologies. To the best of our knowledge, this is the first study that reports aerogels having micropore morphologies (e.g., size, shape, and location) that are precisely controlled through locally controlled thermal conductivity of the substrates.

Magnetic aerogel: an advanced material of high importance.

Magnetic materials have brought innovations in the field of advanced materials. Their incorporation in aerogels has certainly broadened their application area. Magnetic aerogels can be used for various purposes from adsorbents to developing electromagnetic interference shielding and microwave absorbing materials, high-level diagnostic tools, therapeutic systems, and so on. Considering the final use and cost, these can be fabricated from a variety of materials using different approaches. To date, several studies have been published reporting the fabrication and uses of magnetic aerogels. However, to our knowledge, there is no review that specifically focuses only on magnetic aerogels, so we attempted to overview the main developments in this field and ended our study with the conclusion that magnetic aerogels are one of the emerging and futuristic advanced materials with the potential to offer multiple applications of high value.