http://onlinelibrary.wiley.com/rss/journal/10.1002/(ISSN)1521-4095

A full-scale field-free perpendicular magnetization switching driven by spin-orbit torque (SOT) is achieved by employing an ultrathin type-II Dirac semimetal, Pt3Sn. The generation of unconventional SOT is attributed to the spin texture of the topological surface state on the Pt3Sn (111) surface with a z-polarized spin component. This study positions the Dirac semimetals, such as Pt3Sn, as promising spin sources for integration into advanced spintronic devices.

Spin-orbit torque (SOT) induced by current is a promising approach for electrical manipulation of magnetization in advancing next-generation memory and logic technologies. Conventional SOT-driven perpendicular magnetization switching typically requires an external magnetic field for symmetry breaking, limiting practical applications. Recent research has focused on achieving field-free switching through out-of-plane SOT, with the key challenge being the exploration of new spin source materials that can generate z-polarized spins with high charge-to-spin conversion efficiency, structural simplicity, and scalability for large-scale production. This study demonstrates field-free perpendicular switching using an ultrathin type-II Dirac semimetal Pt3Sn layer with a topological surface state. Density functional theory calculations reveal that the unconventional SOT originates from a spin texture with C3v symmetry, leading to significant z-polarized spin accumulation in the Pt3Sn (111) surface, enabling the deterministic switching of perpendicular magnetization. These results highlight the potential of Dirac semimetals like Pt3Sn as scalable and efficient spin sources, facilitating the development of low-power, high-density spintronic memory and logic devices.

This study introduces a multimodal nonlinear microscopy approach using upconverting nanoparticles (UCNPs) under continuous-wave excitation. The UCNPs exhibit high-order nonlinear optical responses, enabling deep-tissue 3D imaging, video-rate wide-field imaging, and depth-selective photomodulation. High-resolution in vivo imaging of mouse cerebrovascular networks is demonstrated, highlighting the potential for cost-effective bioimaging and targeted phototherapy applications.

Nonlinear microscopy provides excellent depth penetration and axial sectioning for 3D imaging, yet widespread adoption is limited by reliance on expensive ultrafast pulsed lasers. This work circumvents such limitations by employing rare-earth doped upconverting nanoparticles (UCNPs), specifically Yb3+/Tm3+ co-doped NaYF4 nanocrystals, which exhibit strong multimodal nonlinear optical responses under continuous-wave (CW) excitation. These UCNPs emit multiple wavelengths at UV (λ ≈ 450 nm), blue (λ ≈ 450 nm), and NIR (λ ≈ 800 nm), whose intensities are nonlinearly governed by excitation power. Exploiting these properties, multi-colored nonlinear emissions enable functional imaging of cerebral blood vessels in deep brain. Using a simple optical setup, high resolution in vivo 3D imaging of mouse cerebrovascular networks at depths up to 800 µmm is achieved, surpassing performance of conventional imaging methods using CW lasers. In vivo cerebrovascular flow dynamics is also visualized with wide-field video-rate imaging under low-powered CW excitation. Furthermore, UCNPs enable depth-selective, 3D-localized photo-modulation through turbid media, presenting spatiotemporally targeted light beacons. This innovative approach, leveraging UCNPs' intrinsic nonlinear optical characteristics, significantly advances multimodal nonlinear microscopy with CW lasers, opening new opportunities in bio-imaging, remote optogenetics, and photodynamic therapy.

A finger-shaped tactile sensor inspired by human fingers is developed, capable of simultaneous normal and shear force detection and 98.33% accurate material identification. Integrated into a robot hand and arm system, it enables real-time detection of gripping force, material identification, advancing haptic sensing in robotics.

Multimodal tactile perception is crucial for advancing human–computer interaction, but real-time multidimensional force detection and material identification remain challenging. Here, a finger-shaped tactile sensor (FTS) based on the triboelectric effect is proposed, capable of multidirectional force sensing and material identification. The FTS is composed of an external material identification section and an internal force sensing section. Three materials are embedded into the surface of the silicone shell in the fingerpad, forming single-electrode sensors for material identification. In the force sensing section, the silicone shell's outer surface is coated with conductive silver paste as a shielding layer. The inner wall has four silicone microneedle arrays and a silicone bump, while five silver electrodes are coated on the internal polylactic acid skeleton. The components connect via interlocking structures near the fingernail, allowing localized contact and separation between the silicone shell and skeleton, enabling force direction detection through signals from the five electrodes. Additionally, the outer sensors achieve 98.33% accuracy in recognizing 12 materials. Furthermore, integrated into a robotic hand, the FTS enables real-time material identification and force detection in an intelligent sorting environment. This research holds great potential for applications in tactile perception for intelligent robotics.