A Miniature Magnetic-Force-Based Three-Axis AC Magnetic Sensor with Piezoelectric/Vibrational Energy-Harvesting Functions

Abstract

Abstract:In this paper, we demonstrate a miniature magnetic-force-based, three-axis, AC magnetic sensor with piezoelectric/vibrational energy-harvesting functions. For magnetic sensing, the sensor employs a magnetic-mechanical-piezoelectric configuration (which uses magnetic force and torque, a compact, single, mechanical mechanism, and the piezoelectric effect) to convert x-axis and y-axis in-plane and z-axis magnetic fields into piezoelectric voltage outputs. Under the x-axis magnetic field (sine-wave, 100 Hz, 0.2-3.2 gauss) and the z-axis magnetic field (sine-wave, 142 Hz, 0.2-3.2 gauss), the voltage output with the sensitivity of the sensor are 1.13-26.15 mV with 8.79 mV/gauss and 1.31-8.92 mV with 2.63 mV/gauss, respectively. In addition, through this configuration, the sensor can harness ambient vibrational energy, i.e., possessing piezoelectric/vibrational energy-harvesting functions. Under x-axis vibration (sine-wave, 100 Hz, 3.5 g) and z-axis vibration (sine-wave, 142 Hz, 3.8 g), the root-mean-square voltage output with power output of the sensor is 439 mV with 0.333 µW and 138 mV with 0.051 µW, respectively. These results show that the sensor, using this configuration, successfully achieves three-axis magnetic field sensing and three-axis vibration energy-harvesting. Due to these features, the three-axis AC magnetic sensor could be an important design reference in order to develop future three-axis AC magnetic sensors, which possess energy-harvesting functions, for practical industrial applications, such as intelligent vehicle/traffic monitoring, processes monitoring, security systems, and so on.

Electrode Coverage Optimization for Piezoelectric Energy Harvesting from Tip Excitation

“…In this paper, we present a theoretical model to analyze the influence of electrode coverage on the electromechanical behaviour of the piezoelectric harvester under tip excitation. Compared with base excitation, the tip excitation method (also known as “Frequency Up-Conversion”) demonstrates broadband capability by beam plucking using magnetic force [ 27 , 28 ] or direct impacts [ 29 , 30 ]. This method has been extensively adopted and studied in recent years for different energy harvesting scenarios, including harvesting from human motion [ 31 ], airflow [ 32 ], and rotational sources [ 33 ], and this method has been regarded as a better way for piezoelectric energy harvesting in many practices.…”

A Novel Three-Axial Magnetic-Piezoelectric MEMS AC Magnetic Field Sensor

“…Today, needs of magnetic field sensors have grown rapidly due to strong demands of the magnetic field sensing from applications such as wearable electronics, navigation systems of vehicles, current-monitoring devices, and electronic compasses of smartphones [1,2,3,4,5,6,7,8,9,10,11,12]. Among these magnetic field sensors, hall effect sensors [13], anisotropic magnetoresistance (AMR) sensors [14], Lorentz force sensors [15,16], and magnetic-piezoresistive sensors [17] are four representative conventional sensors.…”

“…Therefore, in this paper, we significantly improved the sensor’s performance by doing the following: (a) We increased the sensitivity of the sensor eightfold through changing the design of the MEMS movable structure (note: the changes include (i) changing from a square diaphragm [26] to a circular diaphragm to reduce severe stress concentration at corners of the square diaphragm and (ii) reducing the diameter of the electroplated cylindrical Ni thick film inward by 0.6 mm on the MEMS diaphragm to release severe clamping effect between the Ni thick film and the diaphragm). (b) We improved the lower limit of the minimum detectable range of the sensor from 5 Oe [26] to 1 Oe (note: the 1 Oe lower limit of the minimum magnetic field sensing range is sufficient for general industrial applications [1,2,3,4,5,6,7,8,9,10,11,12] as well as the detection of the earth’s magnetic field for smartphone and wearable device applications). (c) We established a detailed three-axial magnetic field sensing criterion.…”

Passive Magnetic-Flux-Concentrator Based Electromagnetic Targeting System for Endobronchoscopy

“…Recently, magnetic sensors [5,6,7,8,9,10,11,12,13,14,15] are developed for electromagnetic and magnetic navigating/targeting/tracking systems which become important alternative navigating/targeting/tracking approaches for surgical/clinical applications [16,17,18,19,20,21,22,23,24]. More recently, these magnetic sensor based electromagnetic navigations are integrated with standard EBUS as a hybrid system to perform a more accurate navigating/targeting endobronchoscope to target/locate lung tumors/lesions [25,26,27,28,29,30].…”