Preparation and characterization of membranes of poly(2,5-benzimidazole) (ABPBI) (as thin as 20 μm) for polymer electrolyte membrane fuel cells are reported. These membranes were prepared by solution casting and then impregnated in phosphoric acid baths. Their characterization included thermogravimetric analyses, conductivity measurements, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. These membranes have high thermal stability and good proton conductivity at temperatures up to 200°C <mml:math display="inline"><mml:mo stretchy="false">(</mml:mo><mml:mn>6.2</mml:mn><mml:mo>×</mml:mo><mml:msup><mml:mrow><mml:mn>10</mml:mn></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>2</mml:mn></mml:mrow></mml:msup><mml:mo>S</mml:mo><mml:msup><mml:mi mathvariant="normal">cm</mml:mi><mml:mrow><mml:mo>−</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:math>(6.2×10−2Scm−1 at 150°C and 30% relative humidity), similar to the well-known commercial polybenzimidazole (PBI). ABPBI membrane-electrode assemblies (MEAs) using commercially available E-TEK Pt/C electrodes were tested in <mml:math display="inline"><mml:msub><mml:mo>H</mml:mo><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo>/</mml:mo><mml:msub><mml:mo>O</mml:mo><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:math>H2/O2 cells, obtaining power densities similar to those of PBI MEAs studied here as reference at temperatures of up to 180°C, humidifying the reactants at room temperature. © 2004 The Electrochemical Society. All rights reserved.

Microrobots offer transformative solutions for non‐invasive medical interventions due to their small size and untethered operation inside the human body. However, they must face the immune system as a natural protection mechanism against foreign threats. Here, non‐immunogenic stealth zwitterionic microrobots that avoid recognition from immune cells are introduced. Fully zwitterionic photoresists are developed for two‐photon polymerization 3D microprinting of hydrogel microrobots with ample functionalization: tunable mechanical properties, anti‐biofouling and non‐immunogenic properties, functionalization for magnetic actuation, encapsulation of biomolecules, and surface functionalization for drug delivery. Stealth microrobots avoid detection by macrophage cells of the innate immune system after exhaustive inspection (>90 hours), which has not been achieved in any microrobotic platform to date. These versatile zwitterionic materials eliminate a major roadblock in the development of biocompatible microrobots, and will serve as a toolbox of non‐immunogenic materials for medical microrobot and other device technologies for bioengineering and biomedical applications.

In the present work, we studied the differentiation capacity of mouse embryonic stem cells (mESCs) and mouse embryonic fibroblasts (MEFs) to differentiate into osteoblast-like cells in a 3-dimensional (3D) self-assembling peptide scaffold, a synthetic nanofiber biomaterial with potential applications in regenerative medicine. We demonstrated that 2D and 3D systems promoted differentiation of mESCs into cells with an osteoblast-like phenotype consisting of osteopontin and collagen I marker expression, as well as high alkaline phosphatase (ALP) activity and calcium phosphate deposits. In 3D cultures the frequency of appearance of embryonic stem cell–like colonies was substantially greater, suggesting that the 3D microenvironment promoted the generation of a stem cell–like niche that allows undifferentiated stem cell maintenance. On the other hand, after MEFs were cultured in the 3D system with their regular growth medium, but not in the 2D system, they expressed osteopontin, up-regulated metalloproteinase activities, and acquired a distinct phenotype consisting of small, elongated cells with remaining mitotic activity. Furthermore, only 3D MEF cultures underwent osteoblast differentiation after osteogenic induction, based on matrix mineralization, collagen I synthesis, ALP activity, and expression of the osteoblast transcription factor Runx2, suggesting that the 3D environment promotes differentiation of MEFs into osteoblast-like cells. We propose that the 3D system provides a unique microenvironment that promotes differentiation of mESCs and MEFs into osteoblast-like cells.