Low-power organic transistors: For internet-of-things applications, transistors that deliver high signal amplification (high gain) at low power will help conserve power and extend battery life. Jiang et al. used inkjet printing to fabricate an organic transistor in which silver metal contacts form a low Schottky barrier (less than 0.2 electron volt) with an organic semiconductor. The transistor delivered gain near the theoretical limit at a power below 1 nanowatt and detected electrophysiological signals from the skin with a wearable device. Science , this issue p. 719

Cu₂O nanoparticles with controllable facets are of great significance for photocatalysis. In this work, the surface termination and facet orientation of Cu₂O nanoparticles are accurately tuned by adjusting the amount of hydroxylamine hydrochloride and surfactant. It is found that Cu₂O nanoparticles with Cu-terminated (110) or (111) surfaces show high photocatalytic activity, while other exposed facets show poor reactivity. Density functional theory simulations confirm that sodium dodecyl sulfate surfactant can lower the surface free energy of Cu-terminated surfaces, increase the density of exposed Cu atoms at the surfaces and thus benefit the photocatalytic activity. It also shows that the poor reactivity of the Cu-terminated Cu₂O (100) surface is due to the high energy barrier of holes at the surface region.

In digital microfluidics, droplet generation is a fundamental operation for quantitative liquid manipulation. The generation of well-defined micro-droplets on a chip with restricted device geometries has become a real obstacle for digital microfluidics platforms to be used in parallel for in vitro diagnostic applications. Here, we propose a “one-to-three” droplet splitting technique that is able to generate sub-microlitre droplets beyond the “well-known” geometry limit in electrowetting-on-dielectric digital microfluidics. Accordingly, we realized an on-chip magnetic bead chemiluminescence immunoassay for parallel detection with the “one-to-three” technique. With the help of the generated micro droplets, we were able to retain the magnetic beads by a significantly reduced magnetic force. We have shown the detection of five B-type natriuretic peptide analyte samples on a single chip for around 10 minutes. The correlation coefficient of the calibration curve was 0.9942, and the detection limit was lower than 5 pg mL⁻¹.