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The UDE (uncertainty and disturbance estimator)‐based control approach has received increasing attention due to its simplicity and effectiveness in rejecting input disturbances. Despite this fact, the inherent transient performance issues associated with a high‐gain UDE are rarely considered. We first design a classic UDE‐based robust controller for a linear system subject to three types of model uncertainties: exogenous disturbance, state‐dependent uncertainty, and input‐dependent uncertainty. We prove by the singular‐perturbation theory that arbitrarily small steady‐state tracking errors can be achieved by choosing an enough‐high gain for the UDE. We then design a novel time‐varying UDE (TV‐UDE) to improve the transient performance. The key of the improved design is to use a differential equation with a time‐varying parameter, instead of a transfer function, to describe the underlying filtering relationship. The formula for the integration by parts is introduced to derive an explicit computable expression of the TV‐UDE. Interestingly, the TV‐UDE is reduced to a classic UDE if the design parameter is fixed. In addition, two types of smooth and bounded functions are proposed to guide the change of UDE parameter from a large value to a smaller value (i.e., from a small gain to a higher one), to ensure that the UDE generates a smooth high‐accuracy estimate. The advantages of the TV‐UDE are demonstrated by simulation and experimental comparisons on a 2‐DOF AERO attitude control platform. The transient performance issues (such as the peaking phenomenon and obvious oscillation) of high‐gain UDE are effectively avoided. [ABSTRACT FROM AUTHOR]

A new approach for the preparation of copper nanoparticles has been developed by the chemical decomposition of bulk‐waste copper wire using HNO3/ DMSO/ NaOCl (HDN) reagent. This is a two‐steps synthesis via a top‐down approach for the preparation of NPs. A mixture of Cu NPs was obtained in high basic pHs (>12) including CuO, Cu(OH)2 and Cu2(OH)3Cl NPs. The Cu NPs demonstrated high dependent on pH, which each of copper NPs were selectively prepared with pH control. Selective preparation of copper NPs lead to pure Botallackite Cu2(OH)3Cl, Cu(OH)2, and Tenorite CuO structures at pH =7, pH<7, and pH=11 respectively. The mixture and pure copper NPs were thoroughly characterized by various analytical techniques including XPS, EDX, XRD, DLS, FTIR, FE‐SEM, TEM, BET, and ICP methods. The resultant Cu NPs were used as an efficient heterogeneous, recyclable nanocatalyst for the preparation of α‐aminonitriles and 5‐substituted 1H‐tetrazoles with a synergistic effect. The nanocatalyst not only demonstrated high to excellent yields for the aminonitriles and tetrazoles under mild conditions, but also it can be recovered and reused for several times without considerable loss in activity. Kinetics for the preparation of α‐aminonitrile and 5‐substituted 1H‐tetrazole was studied and chemoselectivity of the method was evaluated by various combinations. [ABSTRACT FROM AUTHOR]

Functional coatings are of considerable interest because of their fundamental implications for interfacial assembly and promise for numerous applications. Universally adherent materials have recently emerged as versatile functional coatings; however, such coatings are generally limited to catechol, (ortho‐diphenol)‐containing molecules, as building blocks. Here, we report a facile, biofriendly enzyme‐mediated strategy for assembling a wide range of molecules (e.g. 14 representative molecules in this study) that do not natively have catechol moieties, including small molecules, peptides, and proteins, on various surfaces, while preserving the molecule's inherent function, such as catalysis (≈80 % retention of enzymatic activity for trypsin). Assembly is achieved by in situ conversion of monophenols into catechols via tyrosinase, where films form on surfaces via covalent and coordination cross‐linking. The resulting coatings are robust, functional (e.g. in protective coatings, biological imaging, and enzymatic catalysis), and versatile for diverse secondary surface‐confined reactions (e.g. biomineralization, metal ion chelation, and N‐hydroxysuccinimide conjugation). [ABSTRACT FROM AUTHOR]

The tunable growth of metal–organic materials has implications for engineering particles and surfaces for diverse applications. Specifically, controlling the self‐assembly of metal–phenolic networks (MPNs), an emerging class of metal–organic materials, is challenging, as previous studies suggest that growth often terminates through kinetic trapping. Herein, kinetic strategies were used to temporally and spatially control MPN growth by promoting self‐correction of the coordinating building blocks through oxidation‐mediated MPN assembly. The formation and growth mechanisms were investigated and used to engineer films with microporous structures and continuous gradients. Moreover, reactive oxygen species generated by ultrasonication expedite oxidation and result in faster (ca. 30 times) film growth than that achieved by other MPN assembly methods. This study expands our understanding of metal–phenolic chemistry towards engineering metal–phenolic materials for various applications. [ABSTRACT FROM AUTHOR]

Nature has created various organisms with unique chemical components and multi‐scale structures (e.g., foot proteins, toe pads, suckers, setose gill lamellae) to achieve wet adhesion functions to adapt to their complex living environments. These organisms can provide inspirations for designing wet adhesives with mediated drug release behaviors in target locations of biological surfaces. They exhibit conformal and enhanced wet adhesion, addressing the bottleneck of weaker tissue interface adhesion in the presence of body fluids. Herein, it is focused on the research progress of different wet adhesion and bioinspired fabrications, including adhesive protein‐based adhesion and inspired adhesives (e.g., mussel adhesion); capillarity and Stefan adhesion and inspired adhesive surfaces (e.g., tree frog adhesion); suction‐based adhesion and inspired suckers (e.g., octopus' adhesion); interlocking and friction‐based adhesion and potential inspirations (e.g., mayfly larva and teleost adhesion). Other secreted protein‐induced wet adhesion is also reviewed and various suckers for other organisms and their inspirations. Notably, one representative application scenario of these bioinspired wet adhesives is highlighted, where they function as efficient drug delivery platforms on target tissues and/or organs with requirements of both controllable wet adhesion and optimized drug release. Finally, the challenges of these bioinspired wet drug delivery platforms in the future is presented. [ABSTRACT FROM AUTHOR]