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Due to their small size, low weight, low cost and low energy consumption, MEMS accelerometers have achieved great commercial success in recent decades. The aim of this research work is to identify a MEMS accelerometer structure for human body dynamics measurements. Photogrammetry was used in order to measure possible maximum accelerations of human body parts and the bandwidth of the digital acceleration signal. As the primary structure the capacitive accelerometer configuration is chosen in such a way that sensing part measures on all three axes as it is 3D accelerometer and sensitivity on each axis is equal. Hill climbing optimization was used to find the structure parameters. Proof-mass displacements were simulated for all the acceleration range that was given by the optimization problem constraints. The final model was constructed in Comsol Multiphysics. Eigenfrequencies were calculated and model's response was found, when vibration stand displacement data was fed into the model as the base excitation law. Model output comparison with experimental data was conducted for all excitation frequencies used during the experiments.

We present an optical laser-based method to visualize replication of microperiodic profile structures in polymers. Diffraction efficiency of diffraction gratings ͑originally produced in silicon, quartz glass, and in replicated polymer substrates͒ is measured experimentally and simulated using linear dimensions of gratings, or their replica defined by atomic force microscopy ͑AFM͒. Diffraction efficiency of the periodic structure is used to test the surface relief formation during the combined ion etching of crystalline Si ͑100͒ and replication of this structure using UV light hardening and hot embossing. The main experimental results are compared with computer simulations where the standard program ͑PCGrate-SX6.0͒ is employed. Angular dependence of relative efficiency ͑RE͒ appears a versatile tool to analyze the process of origination and replication of diffraction grating in a micrometer range. Both the shape of the grating and linear dimensions can be reconstructed by comparing experimental values of relative efficiency with the simulation results. Examples of hot embossing of different periods of diffraction gratings to the Al/polymethyl methacrylate ͑PMMA͒ on polyethylene terephthalate ͑PET͒ illustrate vitality of such approach.

The paper reports on a nonlinear frequency up-converting vibration energy harvester with enhanced broadband performance below 50 Hz, which is attained by leveraging vibro-impact interaction between two high-frequency piezoelectric generators and two low-frequency resonators with commensurate natural frequencies in the 2:1 ratio. Finite element model was implemented to assess the proposed concept by treating the harvester as a vibro-impact coupled piezoelectric-circuit system. The model accommodates multiple mechanical contact pairs defined by nonlinear dissipative Hunt-Crossley contact force formulation. Effective design principles were applied to maximize power output including near-optimal positioning of the neutral plane in the generators and rational adjustment of response settling time. The fabricated proof-ofconcept device was tested in different clearance configurations and under varying harmonic excitation conditions to reveal rich nonlinear dynamics behavior. The measured hardening-type power frequency responses were examined to gain better insight into nonlinear resonance characteristics (instability jumps, frequency hysteresis, etc), which determine effectiveness of micro-power generation. It was demonstrated that the proposed dual-resonator energy harvester favorably harnesses nonlinear resonance amplification to deliver larger average power output (up to 37 μW) and useable bandwidth (up to 9.5 Hz) in comparison to the conventional singleresonator counterparts (delivering up to 26 μW and up to 7 Hz, respectively). The maximum normalized power density of the device is 41 μW cm −3 g −2 , while volume figure of merit and 3 dB or 1 dB bandwidth-based figures of merit reach 0.18%, 11 μW cm −3 g −2 and 1.5%, respectively. The latter value indicates superior broadband performance of the device. Adoption of mean performance index and coefficient of variation as complementary figures of merit proved to be valuable in identifying device configuration that yields the most effective and stable broadband operation in a targeted frequency range.

Highlights• A wireless sensor node architecture composed from energy harvesting transducer, energy accumulating capacitor, sensors, microcontroller and RF link is proposed and fabricated. • The elaborated algorithm and the created detector could reach no more than 100-150 nA current consumption. • The created wireless sensor energy harvester prototype satisfies the energy needs for sensors and is capable of transmitting the information at the distance of 20 metres. • For cutting tool performance evaluation the limitary moment, when cutting tool starts manufacturing inappropriate quality parts, is defined experimentally and statistically. • The created device opens a way for wireless sensors networks in manufacturing technologies. Graphical abstractVitaeVytautas Ostasevicius graduated from Kaunas University of Technologyengineer mechanic in 1971, doctor of sciencies in 1974, doctor habilitus in 1988. and in industry. His research focuses on electronic system efficiency, energy harvesting, low power management and wireless smart sensors. Mindaugas Cepenas graduated from KaunasUniversity of Technology (KTU) in 2012 with Master's degree in Electrical engineering. Currently, PhD study in Electrical and Electronics Department of Electronics Engineering studies KTU. Research areas -interactive design of microprocessor systems and low-power wireless networks. Laura Kizauskiene is an associate professor at the Department of Computers, and researcher at the Real-time Computer Systems Centre at Kaunas University of Technology. She has gained doctors' degree in Technology Science in 2009. Her main research interests are multi-agent systems, artificial intelligence, wireless sensor networks, embedded real time systems and smart environments. Since 2007, she has been working at Kaunas University of Technology and has participated in several research projects, developing smart house and sensor network technologies. Virginija Gyliene received her License Professional degree (Conception and Fabrication assisted by Computers) from the University of Maine (France) in 2001. She gained a Master degree in Manufacturing Engineering in 2002 and Ph. D. degree in 2007 from KaunasUniversity of Technology. Now, she is the Lecturer in the same University and her research field is numerical and experimental study of cutting processes. AbstractThis paper presents a method of cutting tool vibration energy harvesting for wireless applications, the created devices and the results of the accomplished experiments. The proposed high frequency piezo generator assures energy harvesting, accumulation and appropriateness for wireless sensors applications. The proposed architecture composed from energy harvesting transducer, energy accumulating capacitor, sensors, microcontroller and RF link opens a way for wireless sensors networks in manufacturing technologies providing the effective integration of information, delivered by sensors of different nature, to achieve a wholesome description of the status of the monitored process. The elaborated algorithm a...