Traditional hydrogels usually possess inferior mechanical properties as well as lacking multi-functionalities. Nano-sized particles/fillers, both inorganic and organic materials, have unique chemical, physical, and biological functions, and have been extensively studied as biomaterials or bio-functional materials. Nanocomposite hydrogels, which combine the advantages of both nano-fillers and hydrogel matrices, may result in improved mechanical and biological properties and find their potential applications in biomedical field. This paper reviews recent developments in the synthesis, preparation, and characterization of nanocomposite hydrogels; their biomedical applications, such as drug delivery matrices and tissue engineering scaffolding materials are also summarized.

Ring-opening polymerization of ⑀-caprolactone was carried out smoothly and effectively with constant microwave powers of 170, 340, 510, and 680 W, respectively, with a microwave oven at a frequency of 2.45 GHz. The temperature of the polymerization ranged from 80 to 210°C. Poly(⑀-caprolactone) (PCL) with a weightaverage molar mass (M w ) of 124,000 g/mol and yield of 90% was obtained at 680 W for 30 min using 0.1% (mol/mol) stannous octanoate as a catalyst. When the polymerization was catalyzed by 1% (w/w) zinc powder, the M w of PCL was 92,300 g/mol after the reaction mixture was irradiated at 680 W for 270 min.

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A mechanically tough biodegradable hydrogel is developed from a single precursor comprising poly(ethylene glycol) and oligo(trimethylene carbonate), where both the crosslink density and swelling properties of the polymer network are independently controlled through M c and hydrophilic-hydrophobic balance. These highly cost effective hydrogels are also biocompatible and can be degraded both hydrolytically and enzymatically.

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The indoor location technique plays a essential role during the application of quadrotor unmanned aerial vehicle (UAV). However, the control design problem for the quadrotor UAV is quite difficult in the indoor environment due to the weak GPS signal. Based on Ultra Wide Band (UWB), the related positioning issues can be solved of UAV through base station with known coordinate position and equipment with location tag, but it is difficult to meet the high-precision operation requirements. In this paper, an indoor positioning design method combined with the Inertial Measurement Unit (IMU) and UWB positioning technology is proposed, which can effectively suppress the error accumulation of the IMU and further improve the positioning accuracy. Moreover, the system architecture for a class of quadrotor UAV is designed. The multisensor fusion technology based on unscented Kalman filter (UKF) is used to avoid neglecting the high-order terms of the nonlinear observation equations of UWB and IMU, which can effectively improve the accuracy of solving the nonlinear equations. Finally, a hardware-in-the-loop simulation platform is designed to verify the effectiveness of the indoor positioning method and improve the positioning accuracy.INDEX TERMS Ultra wide band (UWB), inertial measurement unit (IMU), data fusion, indoor localization, quadrotor UAV.

The microenvironments that cells encounter with in vitro.

PCL/clay nanocomposites were prepared by microwave‐assisted in situ ROP of ε‐caprolactone in the presence of either unmodified clay (Cloisite® Na+) or clay modified by quaternary ammonium cations containing hydroxyl groups (Cloisite 30B). This PCL showed significantly improved monomer conversion and molecular weight compared with that produced by conventional heating. An intercalated structure was observed for the PCL/Cloisite Na+ nanocomposites, while a predominantly exfoliated structure was observed for the PCL/Cloisite 30B nanocomposites. Microwave irradiation proved to be an effective and efficient method for the preparation of PCL/clay nanocomposites.magnified image