T he room-temperature plastic deformation of bulk metallic glasses (BMGs) is known to be inhomogeneous both spatially and temporally and achieved by highly localized shear bands (1-3). Inspired by the increasingly intense scientific and technological interests of BMGs and the efforts of improving their limited plasticity (4-7), there is a compelling need to identify the physical processes responsible for the dynamics and rheology of metallic glasses well below their glass transition temperatures. Historically, several rheological theories have been developed to describe the heterogeneous plasticity of glasses. These models are mainly based on two possible atomic-scale mechanisms, i.e., deformationinduced dilatation or free volume (8-10) and local events of cooperative shearing of atomic clusters termed shear transformation zones (STZs) (11-16). Recently, a cooperative shearing model (CSM) of STZs by Johnson and Samwer (17), together with work of Falk and Langer (13,14) and others (18,19), has been shown to provide an effective interpretation of plasticity in metallic glasses well below their glass temperatures. In the Johnson-Samwer model, structure and energetics correlation in glasses has been established by introduction of the concept of potential energy landscapes in combination with STZs, and the mechanical behavior of BMGs is expected to intrinsically depend on the actual volumes of STZs (17,20). Assessment of the sizes of STZs, or the minimum molecular configurations of inelastic rearrangements in BMGs subjected to stresses, is thus of key importance in understanding the plastic deformation of these amorphous solids. More recently, energetic considerations (17, 21) and molecular dynamics (MD) simulations (13, 19) have quantitatively evaluated the number of atoms in a STZ of glassy materials. Despite the aforementioned intense efforts to identify STZ volumes of glasses, an experimental quantitative measurement of the STZ volumes is still missing.Here, we develop an experimental method to characterize the STZs of BMGs based on the Johnson-Sawmer CSM (17). In the Johnson-Sawmer model, a constitutive description of plastic deformation can be given in an equation where inelastic strain rate is a function of dynamical state variables (i.e., the STZ volumes) in addition to stress and strain. A simplified form of this constitutive equation can be written aṡwhereγ is inelastic strain rate,γ 0 is a constant, k is the Boltzmann constant, T is temperature, W * = 4RG 0 γ 2 C (1 − τ/τ C ) 3/2 ζ is the barrier energy at finite stress 0 < τ < τ C , G 0 , and τ C are the shear modulus and the threshold shear resistance of an alloy at 0 K, respectively, the average elastic limit γ C ≈ 0.027 (17), is the volume of STZ, and constants R ≈ 1/4 and ζ ≈ 3 (17). It should be noted that the normal stress dependence of the shear strength (22) is postulated to be insignificant in this analysis. Thus, by direct differentiation of the activation energy W * , we obtain the activation volume in the CSM:From experiments using strain rat...

Nanowires supporting propagating surface plasmons can function as nanowaveguides to realize the light guiding with field confinement beyond the diffraction limit, providing fundamental building blocks for nanophotonic integrated circuits. This review covers the recent developments of plasmon waveguiding in nanowires, mainly including plasmon waveguiding in metal nanowires, coupling of nanowire plasmons and emitters, hybrid nanowire waveguides and plasmonic gain, and nanowire photonic devices. We first introduce the main techniques for fabricating metal nanowires, the plasmon modes in metal nanowires and the excitation/detection methods. We then discuss the fundamental properties of plasmon propagation and emission, including zigzag, chiral and spin-dependent propagation, mode conversion, loss and propagation length, group velocity, terminal emission, and leaky radiation. Then the interactions between nanowires and emitters are reviewed, especially the coupling of single nanowires and single quantum emitters. Finally, we briefly introduce the hybrid nanowire waveguide composed of a semiconductor nanowire and a metal film with an intervening thin insulator and highlight a few nanophotonic devices based on plasmonic nanowire networks or plasmonic-photonic hybrid nanowire structures.

Botanical systems have evolved the intriguing ability to respond to diverse stimuli due to long‐term survival competition. Mimicking these dynamic behaviors has greatly advanced the developments in wide fields ranging from soft robotics, precision sensors to drug delivery and biomedical devices. However, realization of stimuli‐responsive components at the microscale with high response speed still remains a significant challenge. Herein, the miniature biomimetic 4D printing of pH‐responsive hydrogel is reported in spatiotemporal domain by femtosecond laser direct writing. The dimension of the printed architectures is at the microscale (<102 µm) and the response speed is reduced down to subsecond level (<500 ms). Shape transformation with multiple degrees of freedom is accomplished by taking advantage of pH‐triggered expansion, contraction, and torsion. Biomimetic complex shape‐morphing is enabled by adopting flexible scanning strategies. In addition, application of this 4D‐printed micro‐architecture in selective micro‐object trapping and releasing is demonstrated, showcasing its possibilities in micromanipulation, single‐cell analysis, and drug delivery.

42A modified tri-axial electrospinning process was developed for the generation of a

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