Qinhua Wei

Four-dimensional (4D) electronics, with the ability to deform over time in response to controlled actuation, have attracted rapidly growing interest for use in soft robots, biomedical devices, and wearable systems. A scheme to determine the amplitude and distribution of the actuation for the structure to deform into target shapes is essential for 4D electronics to operate precisely. Solution to this inverse problem is not straightforward in many cases, especially when nonlinearity governs the deformation. This work proposes a lightweight data-driven framework for the inverse problem in an electromagnetically actuated soft surface that takes the form of a Cu-EGaIn conductive network. The deformation of the soft surface is controlled by adjusting the applied voltage to regulate the current distribution and consequently the force distribution. Morphology measurement via the binocular vision method, combined with cubic interpolation, establishes the relationship between displacement of feature points and applied voltage. A machine learning architecture is then constructed with a balance between accuracy and training data volume, allowing for the inversion from surface morphology to predicted voltage. The framework avoids the construction of complex electromechanical coupling models and large deformation–current library databases. Using a relatively small experimental dataset of fewer than 300 samples, the prediction accuracies for the applied voltage to drive the morphable surface to target shapes are 82.91% for the activated interface position and 84.91% for the applied voltage value. Meanwhile, the proposed scheme was also preliminarily validated for cross-device reconstruction of liquid metal flexible films fabricated using the current manufacturing process. In addition, the data-driven scheme was further validated for inverse reconstruction beyond the training distribution through lightweight and rapid transfer learning. This work demonstrates the effectiveness of machine learning for determining excitation from surface morphology in electromagnetic actuation, serving as a foundation for 4D electronics.

CsCu₂I₃ crystal is a promising Cu-based halide material for scintillation detection. In this paper, Na⁺ ion-doped CsCu₂I₃ crystals with a size of ϕ12 mm × 50 mm were grown successfully using the vertical Bridgman method, and the properties were systematically investigated. CsCu₂I₃:Na crystals exhibit yellow light emission peaking at 575 nm and a large Stokes shift of 1.55 eV. Based on the results of the XRD and XPS, the Na⁺ was introduced successfully. The optical absorption spectra show that the band gap of CsCu₂I₃ crystals was narrowed when the Na⁺ was doped. The photoluminescence quantum efficiency (PLQY) is improved from 16.4% to 19.6%. Finally, the X-ray-induced afterglow, and scintillation (energy resolution, light yield and decay time) under a ¹³⁷Cs source were measured and discussed. These results illustrate that CsCu₂I₃:Na crystals have potential applications in the radiation detection field.

Study on the growth of a Li ⁺ -doped CsCu ₂ I ₃ crystal for dual gamma-ray and neutron detection.

Study on the growth and scintillation mechanism of Li ⁺ -doped Cs ₃ Cu ₂ I ₅ crystal with an excellent FOM value for dual gamma-ray and neutron detection applications.

The translucent GGAG:Ce/glass composites are prepared successfully by ball-milling, tableting, and pressureless sintering. The thickness of composites is about 400 μm. The x-ray diffraction (XRD), differential scanning calorimetry (DSC), density of composite materials are measured and discussed systematically. The scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) elemental mapping are employed to analyze the particle size, the shape of powders, and the distribution of GGAG:Ce particles in the glass matrix, respectively. The decay time, ultraviolet, (UV), x-ray excitation luminescence spectra, and temperature spectra are studied. The results show that the composite materials have high light output, good thermostability, and short decay time. The method adopted in this work is an effective method to reduce the preparation time and cost of the sample. The ultralow afterglow indicates that the composite materials have an opportunity to be used for x-ray detection and imaging.

Because of incongruent melting, phase separation occurs when Cs₂LiLaBr₆:Ce (CLLB:Ce) is grown from a melt using stoichiometric raw materials. In this study, raw materials with different amounts of excess LiBr are used to grow CLLB:Ce crystals. It is found that enough excess of LiBr is beneficial to the crystal growth of CLLB:Ce. A transparent 1 × 2‐in. CLLB:Ce single crystal is successfully grown by the vertical Bridgman method. The differential scanning calorimeter‐thermogravimetric analysis (DSC‐TG), X‐ray diffraction, and inductively coupled plasma mass spectrometry results are used to understand the crystallization behavior at different stages of the crystal growth process. The luminescence and related scintillation properties of the CLLB:Ce single crystal are investigated. The relative light output of the CLLB:Ce single crystal is about 48 000 ph MeV⁻¹, which is 80% that of the LaBr₃:Ce crystal. The energy resolution of the CLLB:Ce single crystal is 4.0% at ¹³⁷Cs 662 keV.

Gd₂Si₂O₇:Ce (GPS:Ce) and (Gd,La)₂Si₂O₇:Ce (La-GPS:Ce) phosphors with different crystal structures, tetragonal, orthorhombic and triclinic, were synthesized via a sol–gel technique. The prepared samples have been systematically investigated using room temperature (RT) XRD, high temperature (HT) XRD, HRTEM, selected area electron diffraction (SAED) and EDS elemental analysis. The results show that the phase transition occurred at 1350–1450 °C and the tetragonal phase was a low-temperature metastable phase and the orthorhombic and triclinic structures were stable at high temperatures. It was observed that the three structures display completely different luminescence efficiencies under both UV lamp and X-ray excitation, but the decay time was not strongly dependent on the crystal structure. The luminescence thermo-stability and activation energy were also measured and calculated. The results indicate that the thermo-stability was strongly dependent on the crystal structure and the GPS:Ce-1500 °C sample showed the best thermo-stability. The three materials have potential application as a novel type of scintillator.