Germán García Martínez

Thin‐wall metal ultramicro‐ and nanoelectrodes (UMEs/NEs), especially gold‐based ones, are key probes for high‐resolution electrochemical microscopy, biosensing, and nanoscale interfacial studies. Yet, their broader use remains limited by fragility, low detection sensitivity, and the lack of scalable fabrication methods. Here, we present a template‐assisted, non‐self‐limited polyol‐based growth strategy that realizes single‐crystalline, thin‐walled Au UMEs/NEs, as well as multifunctional probes, with high yield (>80%). The method provides precise control over electrode dimensions, from sub‐100 nm to micron‐scale radii while the massively parallel polyol growth step overcomes the key bottleneck in scalable nanoelectrode preparation by reliably producing long, continuous single‐crystal metal cores. Structural and electrochemical characterization confirm twinned single‐crystal Au cores, seamless Au/glass interfaces, and stable performance. Through direct comparison across radii, we show that smaller electrodes consistently exhibit higher surface reactivities, boosting chemical detection sensitivity. In scanning photoelectrochemical microscopy, these NEs achieve an illumination‐dependent spatial resolution of ∼250 nm, <1 pA current sensitivity, a detection limit of ∼11.0 µ m , and over 7 h of operational stability. In bulk electrolytes, the single‐crystalline electrodes achieve ultralow detection limits down to 79 n m , markedly enhancing the signal‐to‐noise ratio in nanoscale electrochemical measurements. Finally, we demonstrate growth in double‐barrel pipettes for multifunctional probes and extend the approach to Pt NEs. This scalable method overcomes longstanding limitations in NE fabrication, enabling advanced electrochemical imaging and its combination with tip‐enhanced spectroscopic methods. The single‐crystalline architecture also opens new frontiers in catalysis, interfacial electrochemistry, biosensing, and molecular‐scale investigations.

The fraction of light absorbed in a material is a key parameter for a wide range of optoelectronic and energy devices, including solar cells, light emitting diodes, and photo(electro)chemical devices. It can reveal detailed performance information and establish a material’s theoretical efficiency limits. However, measuring absorption accurately is challenging, especially due to scattering effects at the macroscale and achieving perpendicular illumination over a small area at the microscale. In this tutorial, we present concepts and best practices in measuring absorption at both the macro- and micro-scale. We also give examples of using absorption to reveal critical optoelectronic information in energy devices. This work aims at standardizing the recording of absorption measurements across a number of fields, allowing for improved microscale understanding of a wide range of samples.

The use of bioprinting as a powerful tool for tissue and organ fabrication has been a promising development in the field of biomedicine, offering unprecedented versatility in the fabrication of biologically and physiologically relevant constructs. Even though there are a plethora of commercial bioprinters available in the market, most of them are overly expensive. Thus, university facilities and independent research groups often find it difficult, if not impossible, to equip themselves with such machinery. In this Review, we analyze affordable alternatives to commercial bioprinters, which are presented by the Do-it-Yourself (DiY) community. First, we discuss the current state of these low-cost technologies, and the advances made to bridge the divergence between marketed bioprinters and DiY devices. Afterwards, the different bioprinting technologies that are most commonplace for these low-cost devices are examined. Additionally, an overview of the pioneering DiY bioprinters takes place, as well as the open-source software alternatives to control these bioprinters. Next, we analyze the different factors to take into consideration during the bioprinting workflow, such as bioinks, computer-aided models, and bioprinting parameters. Finally, we conclude with a brief assessment of current limitations and potential solutions, as well as future developments in the arena of bioprinting.

Significance: This work reports the development of a physiologically relevant human alveolar lung-on-a-chip model, composed of a three-dimensional (3D) porous hydrogel made of gelatin methacryloyl (GelMA) featuring an inverse opal structure, bonded to a compartmentalized chip device that provides air–liquid interface and cyclic breathing motions. Significantly, this GelMA structure has a high similarity to native human alveolar sacs in that they both possess sac-like pores and interconnecting windows between the sacs, in addition to a stiffness similar to the native human distal lung. We showed through multiscale analyses that our 3D GelMA inverse opal structure was better able to maintain the functions of primary human alveolar epithelial cells in a more in vivo-like manner compared with planar models.

Precise absolute far-infrared magnetotransmission experiments have been performed in magnetic fields up to 33 T on a series of single GaAs quantum wells doped at different levels. The transmission spectra have been simulated with a multilayer dielectric model. The imaginary part of the optical response function which reveals singular features related to the electron-phonon interactions has been extracted. In addition to the expected polaronic effects due to the longitudinal-optical phonon of GaAs, a kind of carrier-concentration-dependent interaction with interface phonons is observed. A simple physical model is used to try to quantify these interactions and explore their origin.