This paper presents a model-based approach for the first time to identify the crack location for the hinge-based planar RRR compliant mechanism, a parallel micro-motion stage driven by piezoelectric (PZT) actuators. However, cracks more likely occur on a flexure hinge because it usually undergoes a periodic deformation in service, which eventually compromises mechanism's performance, positioning accuracy for instance. In this work, the pseudo-rigid-body method is used to develop kinematic and dynamic models of the RRR mechanism both in healthy and damaged conditions, where the crack is considered in terms of the rotational compliance of a flexible hinge. The crack location is determined by measuring PZT elongations, which represents the driving toque deviation because of the crack presence. Numerical simulation is conducted to verify the proposed approach, and the results show good match of the identified crack location with the assumed location. Finally, experiments on the RRR mechanism with a prefabricated crack is performed to further validate the proposed models; the experimental results yield a good consistence.

Molybdenum polyoxometalate (PMo)/silica mesoporous composite thin films, which can be applied as multifunctional materials for photochromic and electrochemical applications, were prepared by impregnating PMo into amino-functionalized mesoporous silica thin films. The composite thin films possess excellent reversible photochromic properties and change from colorless to blue under ultraviolet (UV) irradiation. It is shown in the study that intervalence charge transfer and ligand-to-metal charge transfer are the main reasons for photochromism. After UV irradiation, the charge transfer occurs by the reduction of heteropolyanions accompanying the formation of heteropolyblues with multivalence Mo (+6, +5), and the bleaching process of composite thin films is closely related to the presence of oxygen. Moreover, the composite thin films deposited on the indium tin oxide (ITO) substrate can be used as the electrode and have many advantages, including simple fabrication, fast response, and good stability. The modified ITO electrode retains the electrochemical properties of PMo, can catalyze the electroreduction of the BrO3−, and may be used as the current sensor for the BrO3−.