With the increasing growth of the algae industry and the development of algae biorefinery, there is a growing need for high-value applications of algae-extracted biopolymers. The utilization of such biopolymers in the biomedical field can be considered as one of the most attractive applications but is challenging to implement. Historically, polysaccharides extracted from seaweed have been used for a long time in biomedical research, for example, agarose gels for electrophoresis and bacterial culture. To overcome the current challenges in polysaccharides and help further the development of high-added-value applications, an overview of the entire polysaccharide journey from seaweed to biomedical applications is needed. This encompasses algae culture, extraction, chemistry, characterization, processing, and an understanding of the interactions of soft matter with living organisms. In this review, we present algae polysaccharides that intrinsically form hydrogels: alginate, carrageenan, ulvan, starch, agarose, porphyran, and (nano)cellulose and classify these by their gelation mechanisms. The focus of this review further lays on the culture and extraction strategies to obtain pure polysaccharides, their structure-properties relationships, the current advances in chemical backbone modifications, and how these modifications can be used to tune the polysaccharide properties. The available techniques to characterize each organization scale of a polysaccharide hydrogel are presented, and the impact on their interactions with biological systems is discussed. Finally, a perspective of the anticipated development of the whole field and how the further utilization of hydrogel-forming polysaccharides extracted from algae can revolutionize the current algae industry are suggested.

To study biological processes in vitro , biomaterials-based engineering solutions to reproduce the gradients observed in tissues are necessary. We present a platform for the 3D bioprinting of functionally graded biomaterials based on carboxylated agarose, a bioink amendable by extrusion bioprinting. Using this bioink, objects with a gradient of stiffness and gradient of cell concentration were printed. Functionalization of carboxylated agarose with maleimide moieties that react in minutes with a cysteine-terminated cell-adhesion peptide allowed us to print objects with a gradient of an immobilized peptide. This approach paves the way toward the development of tissue mimics with gradients.

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Abstract-Rice husk (RH) is a rich silica by-product of rice production with great potential for industrial applications. After combustion, a rice husk ash rich in silica is obtained, with some amount of other inorganic components constituted mainly of alkaline elements. The study was conducted to characterize both the rice husk and rice husk ash (RHA) in order to evaluate their constitution and the form in which mentioned impurities are present. The amorphous silica crystallized when heated under certain conditions. In this way, the examination of the crystallization process of rice husk ash with different impurity levels was also carried out by varying the temperature, time and heating conditions. The study reveals a preferential distribution of silica at the cell tip of the outer RH surface cells. The impurities form compounds with combinations of different elements such as Ca and Mg, P and K, and are mainly localized below the inner surface in the form of spherical and cuboidal shapes, as well as irregular morphologies. Abstract-Rice husk (RH) is a rich silica by-product of rice production with great potential for industrial applications. After combustion, a rice husk ash rich in silica is obtained, with some amount of other inorganic components constituted mainly of alkaline elements. The study was conducted to characterize both the rice husk and rice husk ash (RHA) in order to evaluate their constitution and the form in which mentioned impurities are present. The amorphous silica crystallized when heated under certain conditions. In this way, the examination of the crystallization process of rice husk ash with different impurity levels was also carried out by varying the temperature, time and heating conditions. The study reveals a preferential distribution of silica at the cell tip of the outer RH surface cells. The impurities form compounds with combinations of different elements such as Ca and Mg, P and K, and are mainly localized below the inner surface in the form of spherical and cuboidal shapes, as well as irregular morphologies..

Polystyrene (PS) is the material of choice for many medical, biological, and biomedical applications given its advantageous properties such as high biocompatibility, optical transparency, and the possibility to shape PS using high‐throughput manufacturing methods at low production costs. Due to its properties, PS is an interesting material for the fabrication of microfluidic systems. In microfluidics, rapid prototyping is of high importance for testing new chip layouts and designs during the product development with the aim of significantly accelerating the manufacturing. To allow transitioning and thus significantly faster translation from research to scalable manufacturing, it would be ideal if the same material could be used throughout the whole design pipeline. However, rapid prototyping and high‐resolution shaping of PS, especially on the micron scale, is still limited. In this work,a novel photocurable polystyrene photoresin, is presented which can be shaped using direct optical lithography. Using this PS photoresin, microfluidic chips with feature sizes down to 50 µm and a high optical transparency can be fabricated. The cured PS photoresin shows comparable surface and material properties to commercial PS. This method will enable researchers in the medical, biological and biomedical fields to produce suitable PS structures with commercial equipment.

Softness plays a key role in the deformation of soft elastic substrates at the three-phase contact line, and the acting forces lead to the formation of a wetting ridge due to elastocapillarity. The change in wetting ridge and surface profiles at different softness has a great impact on the droplet behavior in different phenomena. Commonly used materials to study soft wetting are swollen polymeric gels or polymer brushes. These materials offer no possibility to change the softness on demand. Therefore, adjustable surfaces with tunable softness are highly sought-after to achieve on-demand transition between wetting states on soft surfaces. Here, we present a photorheological physical soft gel with adjustable stiffness based on the spiropyran photoswitch that shows the formation of wetting ridges upon droplet deposition. The presented photoswitchable gels allow the creation of reversibly switchable softness patterns with microscale resolution using UV light-switching of the spiropyran molecule. Gels with varying softness are analyzed, showing a decrease in the wetting ridge height at higher gel stiffness. Furthermore, wetting ridges before and after photoswitching are visualized using confocal microscopy, showing the transition in the wetting properties from soft wetting to liquid/liquid wetting.

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