This paper is a review of the remarkable progress that has been made during the past few decades in design, modeling, and fabrication of micromachined resonators. Although micro-resonators have come a long way since their early days of development, they are yet to fulfill the rightful vision of their pervasive use across a wide variety of applications. This is partially due to the complexities associated with the physics that limit their performance, the intricacies involved in the processes that are used in their manufacturing, and the trade-offs in using different transduction mechanisms for their implementation. This work is intended to offer a brief introduction to all such details with references to the most influential contributions in the field for those interested in a deeper understanding of the material.

The design, modeling, and simulation of a novel micromachined magnetic field sensor are discussed. The sensor uses an electrostatic resonator whose fundamental resonant frequency is modified by a Lorentz force generated from the interaction of the sensor structure and the present magnetic field. The sensor was fabricated in a standard bulk micromachining process without the need for any additional processing steps. Since the sensor does not employ any magnetic materials, it does not exhibit hysteresis. A comprehensive model of the sensor behavior is derived which encompasses the interactions of the involved physical domains. Validity of the modeling results was verified by finite-element simulations, and later, through experiments. The sensitivities of the fabricated sensors are in the range of 48-87 Hz/T, depending on sensor structure and dimensions. The design of the sensor allows for its fabrication in many standard microelectromechanical system processes and is compatible with CMOS processes. The theoretical minimum detectable signal with current devices is on the order of 217 nT. Methods to improve the sensitivity of the current sensors are suggested. A linear response to a wide range of magnetic fields makes this design suitable for applications where large fields need to be measured with high resolution.

A stretchable, flexible antenna fabricated with silver nanowires (AgNW) and polydimethylsiloxane (PDMS) is presented. Highly conductive AgNWs coupled with mechanically flexibility and durable PDMS are shown to produce promising results for RF sensing. The RF antenna is designed as a 1.5-GHz microstrip patch antenna using the transmission-line model. The resonance frequency of the antenna shifts in response to the applied force/strain, making the configuration suitable for wireless sensing applications.

In this paper, the design and experimental results for a novel micromachined electric-field sensor are presented. The operation of the sensor is based on chopping an incident field with a shutter and measuring the induced charge on two sets of electrodes situated below the shutter. Employing of thermal actuators to move the shutter allows for substantial reduction in drive-signal amplitude as compared to electrostatic actuators which has consequently resulted in less interference from the drive signal. Moreover, the drive and sense signals are separated in the frequency domain owing to the inherent nonlinearity of thermal actuators, further improving the accuracy and resolution of the measurements. The relatively small displacements produced by thermal actuators are mechanically amplified using a novel lever mechanism. The sensor is capable of measuring fields as small as 42 V/m using actuation signals on the order of 60 mV.

This paper describes a new type of electric-field sensor that has been fabricated using micromachining technology. This micromachined sensor is dramatically smaller than conventional field mills, possessing a field chopping shutter measuring only 1 mm² . The shutter is moved using thermal actuators, thereby eliminating the wear and tear associated with rotating and moving elements of field mills. The sensor requires minimal operating power, with the shutter being driven by a 75-mV drive signal while consuming only 70 muW. The field chopping shutter operates at ~ 4200 Hz, enabling the measurement of both ac and dc fields. Two sets of sense electrodes enable differential field measurements and, therefore, do not require a reference ground potential. The sensor has a linear response to the electric-field amplitude and has demonstrated that it is capable of measuring a dc field as small as 42 V/m. This miniature sensor is the smallest sensor with such a resolution for use in power engineering applications.