The development of organic thin-film transistors (OTFTs) with low power consumption and high gain will advance many flexible electronics. Here, by combining solution-processed monolayer organic crystal, ferroelectric HfZrOx gating and van der Waals fabrication, we realize flexible OTFTs that simultaneously deliver high transconductance and sub-60 mV/dec switching, under one-volt operating voltage. The overall optimization of transconductance, subthreshold swing and output resistance leads to transistor intrinsic gain and amplifier voltage gain over 5.3 × 104 and 1.1 × 104, respectively, which outperform existing technologies using organics, oxides and low-dimensional nanomaterials. We further demonstrate battery-powered, integrated wearable electrocardiogram (ECG) and pulse sensors that can amplify human physiological signal by 900 times with high fidelity. The sensors are capable of detecting weak ECG waves (undetectable even by clinical equipment) and diagnosing arrhythmia and atrial fibrillation. Our sub-thermionic OTFT is promising for battery/wireless powered yet performance demanding applications such as electronic skins and radio-frequency identification tags, among many others.

Lanthanide-doped particles exhibit unique polarization-dependent luminescence due to the anisotropic crystalline local symmetry surrounding the emitter. Precise control of the orientation of particles shows great significance for exploiting the luminescent polarization and their potential applications. Here, we demonstrated a facile polypropylene-aided shear-driven method to obtain large-scale orientationally ordered upconversion nanorods, showing a liquid-crystalline nematic phase. Upconversion nanorods with low aspect ratios were well-aligned with the crystalline c-axis along the shearing direction using monodispersed colloid nanorods as the nanoink. The order parameter of aligned upconversion nanorods can reach up to 0.95. The nematic upconversion nanorods demonstrated strong polarization-dependent luminescence with the high degrees of polarization of the 4 F 9/2 sublevels at 657 and 661 nm being 0.47 and 0.59, respectively. Taking advantage of these mesoscopic well-aligned upconversion nanorods, their peculiar polarized emissions are potentially useful for some interdisciplinary applications such as polarization-sensitive bioprobes and anticounterfeiting.

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Metasurface-based structural coloration is a promising enabling technology for advanced optical encryption with a high-security level. Herein, we propose a paradigm of electrically switchable, polarization-sensitive optical encryption based on designed metasurfaces