A luminescent mixed lanthanide metal-organic framework approach has been realized to explore luminescent thermometers. The targeted self-referencing luminescent thermometer Eu(0.0069)Tb(0.9931)-DMBDC (DMBDC = 2, 5-dimethoxy-1, 4-benzenedicarboxylate) based on two emissions of Tb(3+) at 545 nm and Eu(3+) at 613 nm is not only more robust, reliable, and instantaneous but also has higher sensitivity than the parent MOF Tb-DMBDC based on one emission at a wide range from 10 to 300 K.

A strategy to achieve a ratiometric thermometer by encapsulating luminescent perylene dye into the pores of a europium metal-organic framework (MOF) is developed. The resulting MOF⊃dye thermometer exhibits highly temperature-dependent luminescence intensity ratio over the physiological temperature range, with a maximum sensitivity of 1.28% °C(-1) at 20 °C.

Two-photon-pumped dye lasers are very important because of their applications in wavelength up-conversion, optical data storage, biological imaging and photodynamic therapy. Such lasers are very difficult to realize in the solid state because of the aggregation-caused quenching. Here we demonstrate a new two-photon-pumped micro-laser by encapsulating the cationic pyridinium hemicyanine dye into an anionic metal-organic framework (MOF). The resultant MOF⊃dye composite exhibits significant two-photon fluorescence because of the large absorption cross-section and the encapsulation-enhanced luminescent efficiency of the dye. Furthermore, the well-faceted MOF crystal serves as a natural Fabry–Perot resonance cavity, leading to lasing around 640 nm when pumped with a 1064-nm pulse laser. This strategy not only combines the crystalline benefit of MOFs and luminescent behaviour of organic dyes but also creates a new synergistic two-photon-pumped lasing functionality, opening a new avenue for the future creation of solid-state photonic materials and devices.

X. (2020). Gesture recognition using a bioinspired learning architecture that integrates visual data with somatosensory data from stretchable sensors.

Compared with traditional stimuli-responsive devices with simple planar or tubular geometries, 3D printed stimuli-responsive devices not only intimately meet the requirement of complicated shapes at macrolevel but also satisfy various conformation changes triggered by external stimuli at the microscopic scale. However, their development is limited by the lack of 3D printing functional materials. This paper demonstrates the 3D printing of photoresponsive shape memory devices through combining fused deposition modeling printing technology and photoresponsive shape memory composites based on shape memory polymers and carbon black with high photothermal conversion efficiency. External illumination triggers the shape recovery of 3D printed devices from the temporary shape to the original shape. The effect of materials thickness and light density on the shape memory behavior of 3D printed devices is quantified and calculated. Remarkably, sunlight also triggers the shape memory behavior of these 3D printed devices. This facile printing strategy would provide tremendous opportunities for the design and fabrication of biomimetic smart devices and soft robotics.

Stretchable strain sensors play a pivotal role in wearable devices, soft robotics, and Internet-of-Things, yet these viable applications, which require subtle strain detection under various strain, are often limited by low sensitivity. This inadequate sensitivity stems from the Poisson effect in conventional strain sensors, where stretched elastomer substrates expand in the longitudinal direction but compress transversely. In stretchable strain sensors, expansion separates the active materials and contributes to the sensitivity, while Poisson compression squeezes active materials together, and thus intrinsically limits the sensitivity. Alternatively, auxetic mechanical metamaterials undergo 2D expansion in both directions, due to their negative structural Poisson's ratio. Herein, it is demonstrated that such auxetic metamaterials can be incorporated into stretchable strain sensors to significantly enhance the sensitivity. Compared to conventional sensors, the sensitivity is greatly elevated with a 24-fold improvement. This sensitivity enhancement is due to the synergistic effect of reduced structural Poisson's ratio and strain concentration. Furthermore, microcracks are elongated as an underlying mechanism, verified by both experiments and numerical simulations. This strategy of employing auxetic metamaterials can be further applied to other stretchable strain sensors with different constituent materials. Moreover, it paves the way for utilizing mechanical metamaterials into a broader library of stretchable electronics.

High-gauge-factor stretchable strain sensors are developed by utilizing a new strategy of thickness-gradient films with high durability, and high uniaxial/isotropic stretchability based on the self-pinning effect of SWCNTs. The monitoring of detailed damping vibration modes driven by weak sound based on such sensors is demonstrated, making a solid step toward real applications.

High-adhesion stretchable electrodes are fabricated by utilizing a novel nanopile interlocking strategy. Nanopiles significantly enhance adhesion and redistribute the strain in the film, achieving high stretchability. The nanopile electrodes enable simultaneous monitoring of electromyography signals and mechanical deformations. This study opens up a new perspective of achieving stretchability and high adhesion for stretchable electronics.