Aza‐ Michael Addition Chemistry for Tuning the Phase Separation of PDMS/PEG Blend Coatings and Their Anti‐Fouling Potentials

Anti-marine biofouling adhesion performance and mechanism of PDMS fouling-release coating containing PS-PEG hydrogel

Polystyrene microspheres compounded with polyethylene glycol-based hydrogel (PS-PEG)/polydimethylsiloxane (PDMS) coatings were prepared using the physical blending method. The chemical structure, surface and interface properties, interlayer adhesion, and tensile properties were tested in this paper. Furthermore, the antifouling performance was evaluated through bovine serum albumin fluorescent protein adsorption testing, marine bacteria adhesion testing, and benthic diatom adhesion testing. The results showed that the coating performance was best when 20 wt% PS-PEG hydrogel was added. Its surface energy was only 19.21 mJ/m2, the maximum breaking strength was 1.24 MPa, the maximum elongation rate was 675 %, the elastic modulus was 2.53 MPa, and the anti-stripping rate was 100 %. In addition, the coating with added 20 wt% PS-PEG hydrogel bacterial adherence rate was 5.36 % and 2.45 % after rinsing and washing, respectively, and the removal rate was 54.29 %. In the benthic diatom adhesion test, the chlorophyll concentration a-value was only 0.0017 mg/L after washing with added 20 wt% hydrogel, and the protein desorption rate was 84.19 % higher than PDMS in the fluorescent protein adsorption test. This coating has the 'low adhesion' and 'desorption' characteristics in the three growth stages of biofouling. Meanwhile, the low surface energy of the silicone is stable, and the hydrogel also dynamically migrates to the surface to gradually form a hydration layer, both are synergistic. When 20 wt% PS-PEG hydrogel was added, the coating demonstrated excellent antifouling performance due to its high hydration layer, low surface energy, high elasticity, and high interlayer adhesion. This research is expected to contribute to the practical applications of hydrogel coatings in marine antifouling.

Skin-Interfaced Wearable Sweat Sensors for Precision Medicine

Wearable sensors hold great potential in empowering personalized health monitoring, predictive analytics, and timely intervention toward personalized healthcare. Advances in flexible electronics, materials science, and electrochemistry have spurred the development of wearable sweat sensors that enable the continuous and noninvasive screening of analytes indicative of health status. Existing major challenges in wearable sensors include: improving the sweat extraction and sweat sensing capabilities, improving the form factor of the wearable device for minimal discomfort and reliable measurements when worn, and understanding the clinical value of sweat analytes toward biomarker discovery. This review provides a comprehensive review of wearable sweat sensors and outlines state-of-the-art technologies and research that strive to bridge these gaps. The physiology of sweat, materials, biosensing mechanisms and advances, and approaches for sweat induction and sampling are introduced. Additionally, design considerations for the system-level development of wearable sweat sensing devices, spanning from strategies for prolonged sweat extraction to efficient powering of wearables, are discussed. Furthermore, the applications, data analytics, commercialization efforts, challenges, and prospects of wearable sweat sensors for precision medicine are discussed.

Bio-macromolecular design roadmap towards tough bioadhesives

Emerging sutureless wound-closure techniques have led to paradigm shifts in wound management. State-of-the-art biomaterials offer biocompatible and biodegradable platforms enabling high cohesion (toughness) and adhesion for rapid bleeding control as well as robust attachment of implantable devices. Tough bioadhesion stems from the synergistic contributions of cohesive and adhesive interactions. This Review provides a biomacromolecular design roadmap for the development of tough adhesive surgical sealants. We discuss a library of materials and methods to introduce toughness and adhesion to biomaterials. Intrinsically tough and elastic polymers are leveraged primarily by introducing strong but dynamic inter- and intramolecular interactions either through polymer chain design or using crosslink regulating additives. In addition, many efforts have been made to promote underwater adhesion via covalent/noncovalent bonds, or through micro/macro-interlock mechanisms at the tissue interfaces. The materials settings and functional additives for this purpose and the related characterization methods are reviewed. Measurements and reporting needs for fair comparisons of different materials and their properties are discussed. Finally, future directions and further research opportunities for developing tough bioadhesive surgical sealants are highlighted.

Click Chemistry Hydrogels for Extrusion Bioprinting: Progress, Challenges, and Opportunities

The emergence of 3D bioprinting has allowed a variety of hydrogel-based "bioinks" to be printed in the presence of cells to create precisely defined cell-loaded 3D scaffolds in a single step for advancing tissue engineering and/or regenerative medicine. While existing bioinks based primarily on ionic cross-linking, photo-cross-linking, or thermogelation have significantly advanced the field, they offer technical limitations in terms of the mechanics, degradation rates, and the cell viabilities achievable with the printed scaffolds, particularly in terms of aiming to match the wide range of mechanics and cellular microenvironments. Click chemistry offers an appealing solution to this challenge given that proper selection of the chemistry can enable precise tuning of both the gelation rate and the degradation rate, both key to successful tissue regeneration; simultaneously, the often bio-orthogonal nature of click chemistry is beneficial to maintain high cell viabilities within the scaffolds. However, to date, relatively few examples of 3D-printed click chemistry hydrogels have been reported, mostly due to the technical challenges of controlling mixing during the printing process to generate high-fidelity prints without clogging the printer. This review aims to showcase existing cross-linking modalities, characterize the advantages and disadvantages of different click chemistries reported, highlight current examples of click chemistry hydrogel bioinks, and discuss the design of mixing strategies to enable effective 3D extrusion bioprinting of click hydrogels.

Super-Hydrophilic Zwitterionic Polymer Surface Modification Facilitates Liquid Transportation of Microfluidic Sweat Sensors

The transportation of sweat in an epidermal sweat sensor is critical for the monitoring of biochemical compositions of human sweat. However, it is still a challenge to engineer microfluidic devices with super-wetting channels for such epidermal sweat sensors. Herein, a zwitterionic poly (2-methacryloyloxyethyl phosphorylcholine) (PMPC) modified microfluidic device with super-wetting and good liquid transport ability via an azo coupling reaction of PMPC onto the surface of polydimethylsiloxane microfluidic devices is reported. The obtained PMPC-modified microfluidic device can be integrated with flexible electrochemical sensor to measure the ion compositions of human sweat in real-time. The super-hydrophilic zwitterionic polymer surface modification can greatly facilitate the transportation of body fluids in microfluidic sensors for the detection of various biomarkers. Such microfluidic sensors have great potential for next-generation personalized healthcare.

Microstructure and Properties of Poly(ethylene glycol)-Segmented Polyurethane Antifouling Coatings after Immersion in Seawater

Polyurethane has a microphase separation structure, while polyethylene glycol (PEG) can form a hydrated layer to resist protein adsorption. In this paper, PEG was introduced to polyurethane to improve the antifouling properties of the polyurethane, providing a new method and idea for the preparation of new antifouling polyurethane materials. The mechanical properties, hydrophilicity, swelling degree, microphase separation and antifouling performance of the coatings were evaluated. The response characteristics of the polyurethane coatings in a seawater environment were studied, and the performance changes of coatings in seawater were tested. The results showed that the crystallized PEG soft segments increased, promoting microphase separation. The stress at 100% and the elasticity modulus of the polyurethane material also markedly increased, in addition to increases in the swelling degree in seawater, the water contact angle decreased. A total of 25% of PEG incorporated into a soft segment can markedly improve the antibacterial properties of the coatings, but adding more PEG has little significant effect. After immersion in seawater, the coatings became softer and more elastic. This is because water molecules formed hydrogen bonding with the amino NH, which resulted in a weakening effect being exerted on the carbonyl C=O hydrogen bonding and ether oxygen group crystallization.