In pneumococcal meningitis it is assumed that bacteria cross the blood-brain barrier (BBB), which consists mainly of cerebral endothelial cells. The effect of Streptococcus pneumoniae on the BBB was investigated with an in vitro BBB model using a human brain microvascular endothelial cell line (HBMEC) and primary cultures of bovine brain microvascular endothelial cells (BBMEC). Within a few hours of incubation with pneumococci, rounding and detachment of the HBMEC were observed, and the transendothelial electrical resistance of the BBMEC monolayer decreased markedly. An S. pneumoniae mutant deficient in pneumolysin did not affect the integrity of the endothelial cell monolayer. Neither cell wall fragments nor isolated pneumococcal cell walls induced changes of endothelial cell morphology. However, purified pneumolysin caused endothelial cell damage comparable to that caused by the viable pneumococci. The cell detachment was dependent on de novo protein synthesis and required the activities of caspase and tyrosine kinases. The results show that pneumolysin is an important component for damaging the BBB and may contribute to the entry of pneumococci into the cerebral compartment and to the development of brain edema in pneumococcal meningitis.

This work reports a new class of liquid crystal elastomers (LCEs) cross-linked with poly(ether-thiourea) comprising a triethylene glycol spacer (LCE-TUEG) wherein thiourea bonds impart a hydrogen bonding capability as well as permit dynamic covalent bond (DCB) exchange at elevated temperatures. While hydrogen bonding enhances the mechanical properties of LCE-TUEG, the DCB allows the macromolecular network rearrangement of the LCEs, resulting in various useful properties that are not present in conventional LCEs, including the ability to undergo welding, melt and solution reprocessing, reprogrammable actuation, and self-healing. By exploiting these dynamic features, electrically powered artificial muscles are fabricated that can be actuated by Joule heating using a resistive wire. In particular, an excellent specific work is demonstrated (≈65 J kg −1 ) for the artificial muscle, and full recyclability of both the LCE matrix and the metallic heating wire is achieved. Furthermore, a biomimetic artificial hand is created by welding and assembling multiple LCE-TUEG films embedded with heating wires, followed by mechanical alignment. The integration of a microcontroller to the artificial hand enables the selective actuation of each finger, and various hand gestures are successfully demonstrated.

Vitrimers have shown advantages over conventional thermosets via capabilities of dynamic network rearrangement to endow repairability as well as recyclability. Based on such characteristics, vitrimers have been studied and have shown promises as a 3D printing ink material that can be recycled with the purpose of waste reduction. However, despite the brilliant approaches, there still remain limitations regarding requirement of new reagents for recycling the materials or reprintability issues. Here, a new class of a 4D printable vitrimer that is translated from a commercial poly(ε‐caprolactone) (PCL) resin is reported to exhibit self‐healability, weldability, reprocessability, as well as reprintability. Thus, formed 3D‐printed vitrimer products show superior heat resistance in comparison to commercial PCL prints, and can be repeatedly reprocessed or reprinted via filament extrusion and a handheld fused deposition modeling (FDM)‐based 3D printing method. Furthermore, incorporation of semicrystalline PCL renders capabilities of shape memory for 4D printing applications, and as far as it is known, such demonstration of FDM 3D‐printed shape memory vitrimers has not been realized yet. It is envisioned that this work can fuel advancement in 4D printing industries by suggesting a new material candidate with all‐rounded capabilities with minimized environmental challenges.

With intrinsic optical and dynamic properties of polysulfide chains, inverse vulcanized copolymers have demonstrated immense potential for infrared (IR) optical applications. However, preparing highly IR‐transparent sulfur‐rich copolymers without sacrificing their thermomechanical properties remains challenging. To overcome the trade‐off relationship between IR optical and thermomechanical properties, an in situ microphase separation strategy for the inverse vulcanization of elemental sulfur utilizing self‐crosslinkable 1,3,5‐trivinylbenzene (TVB) is presented. Even with 80 wt% sulfur content, the microphase‐separated TVB‐rich domain self‐reinforces the copolymer with a noteworthy modulus of ≈2.0 GPa and a high glass transition temperature (Tg) of 92.6 °C, while still exhibiting outstanding IR optical properties. This work is expected to provide insights into the fundamental structure–property relationships of sulfur‐rich copolymers and pave the way for various practical applications.

Here we describe the use of thiourea linkage as a hydrogen (H) bonding and dynamic covalent dual-functional motif to enhance mechanical versatility in biomimetic polymer networks (BMPNs). By controlling the dynamic thiourea bond exchanges in the covalently cross-linked BMPNs, greatly improved malleability and reprocessability are obtained while maintaining their assorted mechanical characteristics of stiffness, strength, toughness, resilience, and adaptability. Such characteristics enable versatile shape manipulation and mechanical functions of the BMPN-based 3D structures, including shape reconfiguration, welding, shape memory, load bearing, deformation/recovery, repair, and reprocessing.

Structural colors have advantages compared with chemical pigments or dyes, such as iridescence, tunability, and unfading. Many studies have focused on developing the ability to switch ON/OFF the structural color; however, they often suffer from a simple and single stimulus, remaining structural colors, and target selectivity. Herein, we present regionally controlled multistimuli-responsive structural color switching surfaces. The key part is the utilization of a micropatterned DNA-hydrogel assembly on a single substrate. Each hydrogel network contains a unique type of stimuli-responsive DNA motifs as an additional cross-linker to exhibit swelling/deswelling via stimuli-responsive DNA interactions. The approach enables overcoming the existing limitations and selectively programming the DNA-hydrogel to a decrypted state (ON) and an encrypted state (OFF) in response to multiple stimuli. Furthermore, the transitions are reversible, providing cyclability. We envision the potential of our method for diverse applications, such as sensors or anticounterfeiting, requiring multistimuli-responsive structural color switching surfaces.

Stretchable electronic circuits are critical in a variety of next-generation electronics applications, including soft robots, wearable technologies, and biomedical applications. To date, printable composite conductors comprising various types of conductive fillers have been suggested to achieve high electrical conductance and excellent stretchability. Among them, liquid metal particles have been considered as a viable candidate filler that can meet the necessary prerequisites. However, a mechanical activation process is needed to generate interconnected liquid channels inside elastomeric polymers. In this study, we have developed a chemical strategy of surface-functionalizing liquid metal particles to eliminate the necessity of additional mechanical activation processes. We found that the characteristic conformations of the polyvinylpyrrolidone surrounding eutectic gallium indium particles are highly dependent on the molecular weight of polyvinylpyrrolidone. By virtue of the specific chemical roles of polyvinylpyrrolidone, the as-printed composite layers are highly conductive and stretchable, exhibiting an electrical conductivity approaching 8372 S/cm at 100% strain and an invariant resistance change of 0.92 even at 75% strain after a 60,000 cycle test. The results demonstrate that the self-activated liquid metal-based composite conductors are applicable to traditional stretchable electronics, healable stretchable electronics, and shape-morphable applications.

Recently, sulfur-rich polymers have been applied in various fields including energy storage, mercury absorption, and infrared (IR) optics. However, sulfur-rich polymers typically exhibit insufficient thermomechanical properties for practical applications. Herein,...