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openaire: EC/H2020/725513/EU//SuperRepel A myriad of natural surfaces such as plant leaves and insect wings can repel water and remain unwetted inspiring scientists and engineers to develop water-repellent surfaces for various applications. Those natural and artificial water-repellent surfaces are typically opaque, containing micro- and nano-roughness, and their wetting properties are determined by the details at the actual liquid-solid interface. However, a generally applicable way to directly observe moving contact lines on opaque water-repellent surfaces is missing. Here, we show that the advancing and receding contact lines and corresponding contact area on micro- and nano-rough water-repellent surfaces can be readily and reproducibly quantified using a transparent droplet probe. Combined with a conventional optical microscope, we quantify the progression of the apparent contact area and apparent contact line irregularity in different types of superhydrophobic silicon nanograss surfaces. Contact angles near 180° can be determined with an uncertainty as low as 0.2°, that a conventional contact angle goniometer cannot distinguish. We also identify the pinning/depinning sequences of a pillared model surface with excellent repeatability and quantify the progression of the apparent contact interface and contact angle of natural plant leaves with irregular surface topography.

Brain-on-Chip devices, which enable on-chip cultures of neurons to simulate brain functions, are receiving tremendous attention to meet the demands of both fundamental research and clinical trials. Thus, miniaturized sensors are being developed to accomplish real-time monitoring of neurotransmitters, which are the signaling molecules between neurons and benchmarks for neuron network operation. Electrochemical sensors are promising candidates for detecting a critical neurotransmitter, dopamine (DA), a biomarker for Parkinson’s disease. A key advantage of electrochemical sensors is their capability of fast, real-time recording. However, current state-of-the-art electrochemical DA sensors are suffering from various issues like limited sensitivity and cumbersome fabrication. Here, we report a novel route in monolithically microfabricating vertically aligned carbon nanofiber (VACNF) electrochemical DA microsensors by an anti-blistering slow cooling process. Thanks to the new microfabrication process, we are able to achieve VACNF microsensors with complete insulation and large surface areas. The champion device shows extremely high sensitivity of 4.52×104 μA/μM · cm2, which is at least two-orders-of-magnitude higher than current devices, and a highly competitive limit of detection of 0.243 nM. These figures of merit will open new windows for future applications of Brain-on-Chip devices such as electrochemical recording from a single neuron.

openaire: EC/H2020/824070/EU//CONNECT Funding Information: The authors thank Dr. Ville Rontu for valuable discussions in ALD process, Niklas Wester and Antti Peltonen for help with preparing electrode samples. The work utilized the fabrication and characterization facilities of Aalto University, cleanroom facilities of Micronova micro and nanofabrication center, and Nanotalo-Nanomicroscopy Center (Aalto-NMC). This project has received funding from the Horizon 2020 Framework Programme Project : 824070 — CONNECT. Publisher Copyright: © 2021 Titanium nitride (TiN) is widely utilized in microelectrode array fabrication for electrophysiological recordings due to its relatively low noise levels, long term stability, and exceptional biocompatibility. Atomic layer deposition (ALD) is a well-established approach for the fabrication of TiN thin films, offering great control over the thickness and properties of the films. Although, advanced procedures have been reported to develop micro and nanostructured electrodes, TiN thin film has yet not been widely applied as electrode material for electrochemical sensing, and characterization of these ALD fabricated TiN films is lacking. Here, we study the use of TiN thin films as electrochemical signal transducer for neurotransmitter dopamine (DA) detection with emphasis on investigation the effect of oxygen functionalities on the electrochemical performance of the films. We find that in order to have high enough sensitivity and selectivity the electrode material used to realize the measurements must be modified.In this work, we described TiN thin film surface modification through hybridization of microfabrication and nanocomposite approaches. Because of its good adhesion, TiN is considered as a high interesting support for Pt catalyst. Therefore, ALD was used to deposit TiN thin films and to design Pt nanoparticles (Pt NPs) on highly conductive boron-doped silicon. Further modification was done through multiwalled carbon nanotubes (MWCNTs), which were immobilized on Pt NPs/ TiN hybrid electrode by Nafion film. Synergistic effect of Pt NPs, MWCNTs, and Nafion film caused significant increase in the electrocatalytic activity towards DA electrooxidation. The proposed sensor material was characterized by focused ion beam milling combined with scanning electron microscopy (FIB-SEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), spectroscopic ellipsometry, contact angle measurement and its electrochemical behavior was studied by cyclic voltammetry (CV). CV technique was applied for sensing DA in the range of 0.05–35 µM (R2 = 0.990) with a good sensitivity (16.31 μA/μM) and a low detection limit of 40 nM (for S/N = 3). The developed sensor exhibited reasonable response time and good stability.

Stem cell renewal and differentiation are regulated by interactions with the niche. Although multiple cell populations have been identified in distinct anatomical compartments, little is known about niche-specific molecular factors. Using skin as a model system and combining single-cell RNA-seq data analysis, immunofluorescence, and transgenic mouse models, we show that the transmembrane protein embigin is specifically expressed in the sebaceous gland and that the number of embigin-expressing cells is negatively regulated by Wnt. The loss of embigin promotes exit from the progenitor compartment and progression toward differentiation, and also compromises lipid metabolism. Embigin modulates sebaceous niche architecture by affecting extracellular matrix organization and basolateral targeting of monocarboxylate transport. We discover through ligand screening that embigin is a direct fibronectin receptor, binding to the N-terminal fibronectin domain without impairing integrin function. Our results solve the long-standing question of how embigin regulates cell adhesion and demonstrate a mechanism that couples adhesion and metabolism.