Fabrication and Simulation of an Electromagnetic Microrelay

The fabrication and simulation of an electromagnetic microrelay are presented based on micro electromechanical systems (MEMS) technique.The microrelay dimensions of about 4mm×4mm×0 5mm are fabricated with the common technique of micromachining.Compared with the traditional relays,a planar coil is substituted for a solenoid coil to favor the MEMS fabrication.Moreover,a bi supporter cantilever beam with high sensitivity is fabricated to act as the movable electrode of the microrelay.Theoretical calculations and simulations are also carried out with respect to the electromagnetic force yielded by the exciting electromagnetic coil.The structure and parameters concerning the electromagnetic microrelay can be optimized using the results.

Flexible multilayer MEMS coils and their application in energy harvesters

Electromagnetic vibration energy harvesters are promising for the power supply of wireless sensor nodes,small electronic devices,and wearable electronics.Conventional electromagnetic harvesters usually increase output by increasing the size of coils and magnets,limiting the improvement of energy conversion efficiency and power density.In this study,multilayer microelectromechanical system(MEMS)coils were prepared using flexible electronics,and their high integration performance in arbitrary space was utilized to greatly improve the utilization of the space magnetic field by the electromagnetic harvester.The core magnet of the generator was magnetically balanced to achieve levitation,which improved the sensitivity and reduced fatigue damage compared with traditional spring structures.The wound coils on the top and bottom of the magnet and the flexible coils on the sides worked together to improve the energy efficiency and output of the devices.The output performance of the device with different number distributions was simulated using mathematical models to obtain the optimal structural parameters.The results show that by introducing flexible multilayer MEMS coils on the side surface of the energy harvester,the open-circuit voltage of the energy generators increased from 7 to 10 V by more than 43%.Flexible multilayer MEMS coils can enhance energy conversion rates and possess compact dimensions,making them suitable for integration onto complex surfaces.After the vibration energy harvesting system testing,the maximum peak power of the harvester was 7.1 m W at an acceleration of1 g and a resonant frequency of 11 Hz with a resistor of 3.5 kΩinternal resistance.Moreover,a 470μF capacitor can be charged to 3.5 V within 10 s to drive a hygrothermograph to work for more than 80 s and can supply a light bulb continuously.This strategy shows the great potential of vibration-energy-driven electromagnetic generators for powering small electronics in limited spaces.

A Novel Magnetic Bead-based Biosensor Using Flip Chip Bonding Techniques

Based on flip-chip packaging,a novel approach towards integrated magnetic bio-separator was designed.The magnetic field and the force on the bead were simulated and analyzed,leading to the optimization of the fabrication parameters of the micro-magnetic unit.The planar coil as an electromagnet was fabricated through electroplating on a single seed layer. The PDMS microfluidic channel was bonded on the inverse side after Si etching.The results presented in this paper provide a novel design and fabrication to approach a microfluidic bio-separation system with magnetic beads.

Method of measuring rotation speed of high spinning projectile based on plane magnetic induction coil

For the test of rotation speed of high spinning projectile, the general formula of the motional electromotive force （MEMF） of planar magnetic induction coil （PMIC） is derived in case of 3D rotation in a stable magnetic field. Under a reasona-ble assumption, the MEMF of PMIC is simplified after the aforementioned general formula is used to calculate high spinning PMIC in the geomagnetic field environment. The determination approach of half-cycle is discussed and the method of rotation speed test is studied, and a test is conducted in the paper. The rotation speed curve obtained by the approach in this paper is consistent with the curve by telemetry.

Low-field NMR micro coils based on printed circuit board technology

Radiofrequency coil is one of the most important components for a nuclear magnetic resonance(NMR)instrument.In this article,some planar micro coils with an inner diameter of 2 mm and number of turns that varied from 1 to 11 were investigated based on the printed circuit board(PCB)technology.The electrical characterization of micro coils show that self-resonant frequencies are larger than 200 MHz.Then,an NMR measurement platform with a static magnetic field of 0.66 T was constructed and the signal to noise ratio(SNR)values of the NMR were analyzed.It was found that the SNR is optimal when the turn number of the micro coils is six and the excitation time of a 90°pulse is 0.8?s.Finally,we used the micro coil with six turns to study the transverse relaxation rate of copper sulfate pentahydrate aqueous solution with different concentrations.It was found that the transverse relaxation rate is proportional to the solution concentration.Results from the micro coil were verified by measurements using a Bruker Minispec MQ60.

Reconfigurable Transmitter Coil Structure for Highly Efficient and Misalignment-insensitive Wireless Power Transfer Systems in Megahertz Range

The structural optimization of coils is a key issue in wireless power transfer(WPT)applications owing to size limitations.In this study,a novel planar-spiral transmitter coil(TX-coil)with an outer-tight and inner-sparse configuration is proposed to achieve a high quality factor(Q-factor)and uniform magnetic field,which ensures high efficiency and improves the misalignment tolerance for several-megahertz WPT systems.Furthermore,a closed-form expression for the Q-factor is provided and analyzed for coil optimization.By using this method,a TX-coil with an outer diameter of 100 mm and a wire diameter of 1.5 mm is designed and tested at 1 MHz.Finite element method simulations and experimental results demonstrate that the Q-factor is increased by about 8%in comparison with evenly spaced planar spiral coils,which is achieved while ensuring a relatively uniform magnetic field.