Unraveling the Intrinsic Thermal Behavior of Freestanding Ionomer Films Depending on Thickness from Commercial Membrane to Nanofilm.

Proton exchange membrane fuel cells (PEMFCs) for automotive applications are required to achieve mechanical reliability at various temperatures ranging from subfreezing to 80 °C. The thermal behavior of the electrode should be considered at the initial design stage to design a robust automotive fuel cell electrode. Recently, a behavior different from that of the bulk state has been reported for ionomers with a few nanometers of thickness. Therefore, the intrinsic thermal behavior of ionomer films with thicknesses from micrometers to nanometers is quantitatively investigated in this study. By introducing the fabrication of a pseudo-freestanding Nafion thin film and in-plane thermal strain measurement method on the water surface, the thermal expansion of the freestanding Nafion thin film was successfully measured with minimizing substrate constraints. Thermal strain measurement and X-ray scattering studies revealed that the weakening of intermolecular interaction within the hydrophobic and hydrophilic domains in the Nafion thin film caused thermal expansion, and well-structured hydrophobic domains could suppress thermal expansion. The thermal expansion behavior with different heat treatments provides evidence of the thin-film-to-bulk transition of the fully hydrated Nafion film. Intrinsic thermal behavior without substrate interactions can facilitate an understanding of the thermal behavior of electrodes and provide insight into designing a robust PEMFC in temperature-varying environments.

A seamless auxetic substrate with a negative Poisson's ratio of -1.

Auxetic metamaterials are a unique class of materials or structures with a negative Poisson's ratio and a wide array of functionalities. However, their inherent porosity presents challenges in practical applications. Filling the inherent perforations while preserving their unique auxeticity is difficult because it demands the seamless integration of components that have highly distinct mechanical characteristics. Here we introduce a seamless auxetic substrate film capable of achieving a negative Poisson's ratio of -1, the theoretical limit of isotropic materials. This breakthrough is realized by incorporating a highly rigid auxetic structure reinforced by glass-fabric, with surface-flattening soft elastomers. We effectively optimize the mechanical properties of these components by systematic experimental and theoretical investigations into the effects of relative differences in the moduli of the constituents. Using the developed auxetic film we demonstrate an image distortion-free display having 25 PPI resolution of micro-LEDs that is capable of 25% stretching without performance degradation.

Spectrin mediates 3D-specific matrix stress-relaxation response in neural stem cell lineage commitment.

While extracellular matrix (ECM) stress relaxation is increasingly appreciated to regulate stem cell fate commitment and other behaviors, much remains unknown about how cells process stress-relaxation cues in tissue-like three-dimensional (3D) geometries versus traditional 2D cell culture. Here, we develop an oligonucleotide-crosslinked hyaluronic acid-based ECM platform with tunable stress relaxation properties capable of use in either 2D or 3D. Strikingly, stress relaxation favors neural stem cell (NSC) neurogenesis in 3D but suppresses it in 2D. RNA sequencing and functional studies implicate the membrane-associated protein spectrin as a key 3D-specific transducer of stress-relaxation cues. Confining stress drives spectrin's recruitment to the F-actin cytoskeleton, where it mechanically reinforces the cortex and potentiates mechanotransductive signaling. Increased spectrin expression is also accompanied by increased expression of the transcription factor EGR1, which we previously showed mediates NSC stiffness-dependent lineage commitment in 3D. Our work highlights spectrin as an important molecular sensor and transducer of 3D stress-relaxation cues.

Blood culture-free ultra-rapid antimicrobial susceptibility testing.

Treatment assessment and patient outcome for sepsis depend predominantly on the timely administration of appropriate antibiotics1-3. However, the clinical protocols used to stratify and select patient-specific optimal therapy are extremely slow4. In particular, the major hurdle in performing rapid antimicrobial susceptibility testing (AST) remains in the lengthy blood culture procedure, which has long been considered unavoidable due to the limited number of pathogens present in the patient's blood. Here we describe an ultra-rapid AST method that bypasses the need for traditional blood culture, thereby demonstrating potential to reduce the turnaround time of reporting drug susceptibility profiles by more than 40-60 h compared with hospital AST workflows. Introducing a synthetic beta-2-glycoprotein I peptide, a broad range of microbial pathogens are selectively recovered from whole blood, subjected to species identification or instantly proliferated and phenotypically evaluated for various drug conditions using a low-inoculum AST chip. The platform was clinically evaluated by the enrolment of 190 hospitalized patients suspected of having infection, achieving 100% match in species identification. Among the eight positive cases, six clinical isolates were retrospectively tested for AST showing an overall categorical agreement of 94.90% with an average theoretical turnaround time of 13 ± 2.53 h starting from initial blood processing.

3D printable and biocompatible PEDOT:PSS-ionic liquid colloids with high conductivity for rapid on-demand fabrication of 3D bioelectronics.

3D printing has been widely used for on-demand prototyping of complex three-dimensional structures. In biomedical applications, PEDOT:PSS has emerged as a promising material in versatile bioelectronics due to its tissue-like mechanical properties and suitable electrical properties. However, previously developed PEDOT:PSS inks have not been able to fully utilize the advantages of commercial 3D printing due to its long post treatment times, difficulty in high aspect ratio printing, and low conductivity. We propose a one-shot strategy for the fabrication of PEDOT:PSS ink that is able to simultaneously achieve on-demand biocompatibility (no post treatment), structural integrity during 3D printing for tall three-dimensional structures, and high conductivity for rapid-prototyping. By using ionic liquid-facilitated PEDOT:PSS colloidal stacking induced by a centrifugal protocol, a viscoplastic PEDOT:PSS-ionic liquid colloidal (PILC) ink was developed. PILC inks exhibit high-aspect ratio vertical stacking, omnidirectional printability for generating suspended architectures, high conductivity (~286 S/cm), and high-resolution printing (~50 µm). We demonstrate the on-demand and versatile applicability of PILC inks through the fabrication of 3D circuit boards, on-skin physiological signal monitoring e-tattoos, and implantable bioelectronics (opto-electrocorticography recording, low voltage sciatic nerve stimulation and recording from deeper brain layers via 3D vertical spike arrays).

Delay in the diagnosis of Brucella abortus bacteremia in a nonendemic country: a case report.

BACKGROUND: It is challenging to diagnose brucellosis in nonendemic regions because it is a nonspecific febrile disease. The accurate identification of Brucella spp. in clinical microbiology laboratories (CMLs) continues to pose difficulties. Most reports of misidentification are for B. melitensis, and we report a rare case of misidentified B. abortus. CASE PRESENTATION: A 67-year-old man visited an outpatient clinic complaining of fatigue, fever, and weight loss. The patient had a history of slaughtering cows with brucellosis one year prior, and his Brucella antibody tests were negative twice. After blood culture, the administration of doxycycline and rifampin was initiated. The patient was hospitalized due to a positive blood culture. Gram-negative coccobacilli were detected in aerobic blood culture bottles, but the CML's lack of experience with Brucella prevented appropriate further testing. Inaccurate identification results were obtained for a GN ID card of VITEK 2 (bioMérieux, USA) and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) using a MALDI Biotyper (Bruker, Germany). The strain showed 100.0% identity with Brucella spp. according to 16S rRNA sequencing. MALDI-TOF MS peaks were reanalyzed using the CDC MicrobeNet database to determine Brucella spp. (score value: 2.023). The patient was discharged after nine days of hospitalization and improved after maintaining only doxycycline for six weeks. The isolate was also identified as Brucella abortus by genomic evidence. CONCLUSION: Automated identification instruments and MALDI-TOF MS are widely used to identify bacteria in CMLs, but there are limitations in accurately identifying Brucella spp. It is important for CMLs to be aware of the possibility of brucellosis through communication with clinicians. Performing an analysis with an additional well-curated MALDI-TOF MS database such as Bruker security-relevant (SR) database or CDC MicrobeNet database is helpful for quickly identifying the genus Brucella.

Evaluating Free Thermal Expansion and Glass Transition of Ultrathin Polymer Films on Heated Liquid.

Thermomechanical properties of ultrathin films are crucial for fabrication and use of reliable thin electronic devices. Due to the lack of precise measurement techniques, the thermal deformation behavior of ultrathin films has not yet been clarified. Here, we propose a film on heated liquid (FOHL) method to simultaneously measure the coefficient of thermal expansion (CTE) and glass transition temperature (Tg) of multiple ultrathin polymer films. Free thermal expansion of thin films without substrate interaction can be guaranteed when the thin films are afloat on a liquid surface. To investigate the thermal behavior in a wide temperature range, glycerol is adopted as a thermally stable heating platform owing to its high boiling point of 290 °C. The thin films are transferred onto the glycerol surface from the water surface using the hygroscopic properties of glycerol. Highly accurate and high-throughput thermal strain measurement is achieved using three-dimensional digital image correlation (3D-DIC). The thermomechanical properties of ultrathin polystyrene thin films of various thicknesses (25-400 nm) are precisely characterized utilizing the FOHL and 3D-DIC method.

Plane Stress Fracture Toughness Testing of Freestanding Ultra-Thin Nanocrystalline Gold Films on Water Surface.

Fracture toughness, which is the resistance of a material to crack propagation, is a critical material property for ensuring the mechanical reliability of damage-tolerant design. Recently, damage-tolerant design is introduced to flexible electronics by adopting micro-cracked ultra-thin nanocrystalline (NC) gold films as stretchable electrodes in a plane stress state. However, experimental investigation of the plane stress fracture toughness of those films remains challenging due to the intrinsic fragility from their sub-100 nm thicknesses. Here, a quantitative method for systematically evaluating the plane stress fracture toughness of freestanding ultra-thin NC gold film on water surface platform is presented. After effectively fabricating single-edge-notched-tension samples with femtosecond laser, mode I stress intensity factors are measured in the plane stress state on water surface. Moreover, investigation regarding the effect of notch length, notch sharpness, and notch tip plasticity validates this method based on linear elastic fracture mechanics theory. As a demonstration, the thickness-dependent plane stress fracture toughness of ultra-thin NC gold films is qualitatively unveiled. It is revealed that the thickness confinement effect on grain boundary sliding induces a transition in fracture behavior. This method is expected to further clarify the fracture-related properties of various ultra-thin films for next-generation electronics.

Genetic stability of Mycobacterium abscessus during antibiotic treatment.

OBJECTIVES: Genetic changes in Mycobacterium abscessus during antibiotic treatment are not fully understood. This study aimed to investigate the genetic changes in M. abscessus in patients receiving antibiotic treatment, and their clinical implications. METHODS: Pretreatment and 12-month post-treatment M. abscessus isolates were obtained from patients with M. abscessus pulmonary disease. Isolates from each time point were separated into six groups based on their distinctive morphological characteristics. Twenty-four isolates, comprising 12 from patient A exhibiting progressive disease and 12 from patient B demonstrating stable disease, underwent sequencing. Subsequently, minimal inhibitory concentrations (MICs) for the administered antibiotics were measured. RESULTS: Persistent infection with a single strain was observed in patients A and B. During 12 months of treatment, MICs for administered drugs did not generally change over time in either patient and single nucleotide variations (SNV) associated with antimicrobial resistance (rrl, rrs, erm(41), gyrA, gyrB, whiB7 and hflX) were not mutated. Although not significant, 47 and 52 non-synonymous SNVs occurred in M. abscessus from patients A and B, respectively, and the accumulation of these SNVs differed in patients A and B, except for five SNVs. The most variable positions were within a probable NADH-dependent glutamate synthase gene and a putative YrbE family protein gene in patients A and B, respectively. CONCLUSIONS: Persistent infections by a single strain of M. abscessus were observed in two patients with different clinical courses. Genetic changes in M. abscessus during antibiotic treatment were relatively stable in these patients. CLINICAL TRIALS IDENTIFIER: NCT01616745 (ClinicalTrials.gov ID).