Design, Modeling, and Control of a Micromachined Nanopositioner With Integrated Electrothermal Actuation and Sensing

Abstract-Conventional heaters used in microelectromechanical systems (MEMS) electrothermal displacement sensors typically feature a uniform cross section, which results in a nonuniform temperature profile. In this paper, electrothermal sensors with a shaped beam profile are introduced, with simulation results showing that a much flatter temperature distribution is achieved across the length of the heater. The proposed sensor design is implemented as the displacement sensor for a MEMS nanopositioner together with a more conventional electrothermal sensor design for comparative purposes. Experimental testing indicates that the shaped profile significantly improves upon the conventional sensor design in a number of areas, including sensitivity, linearity, and noise performance.[ 2012-0291]Index Terms-Displacement sensor, microelectromechanical systems (MEMS) electrothermal sensing, silicon thermal heaters.

show abstract

“…For such reasons, integrated electrothermal displacement sensors continue to be demonstrated in a growing number of MEMS applications [5]- [11].…”

mentioning

confidence: 99%

Design and Analysis of Nonuniformly Shaped Heaters for Improved MEMS-Based Electrothermal Displacement Sensing

Fowler

Bazaei

Moheimani

2013

J. Microelectromech. Syst.

Self Cite

View full text Add to dashboard Cite

show abstract

“…However, the reduction of gap is negligible for a heater with long legs, where their compliance prevents buckling of the sensing part [19]. For Silicon heaters with short legs, 2 microns width, and sensing lengths less than 100 microns, observations at very high temperatures also confirm a negligible gap reduction [20], [30].…”

Section: Static Analysismentioning

confidence: 93%

A Comprehensive Analysis of MEMS Electrothermal Displacement Sensors

Bazaei

Moheimani

2014

IEEE Sensors J.

Self Cite

View full text Add to dashboard Cite

Abstract-For electrothermal microelectromechanical system position sensors, we introduce a novel analytical model that captures the nonuniform distribution of temperature as well as the nonlinear dependence of resistivity on temperature. The proposed model also captures the effects of contoured beam heaters and the nonuniformity of the air gap between the heatsink and the heaters, which varies with heat-sink position and is differentially transduced into the output voltage. The model accurately predicts the experimentally obtained I-V data and the corresponding sensor output. It also explains the considerable improvement achieved in the linearity of the sensor response when the beam profiles are appropriately shaped to yield a more uniform temperature distribution. The shaped sensor is compared with conventional uniform electrothermal sensors under two different operating conditions, voltage, and current bias modes. Improved linearity is observed in both cases. The model is also applicable to predict the dynamic response of the sensor. An iterative procedure is developed to solve the additional complexity in voltage mode, which is a nonlinear partial integro-differential equation. Considering different bias modes and heater profiles, we evaluate the sensor bandwidth and linearity using the model and conduct experiments to validate the results. Based on first principles, the proposed model is more transparent than sophisticated software-based approaches and compatible with traditional solvers in MATLAB.Index Terms-Electrothermal, position sensor, MEMS, nonlinear analysis. I. MOTIVATIONI N MANY micro-electro-mechanical systems (MEMS), it is highly desirable to measure the displacement of moving components accurately [1]-[8]. This is particularly important in applications such as probe-based data storage and scanningprobe microscopy, where the required high positioning accuracies are achieved by feedback control and displacement sensing In [25], electrothermal position sensors were analyzed using a system approach. The effect of nonuniform temperature distribution along the heaters was not considered in this analysis. This effect was considered for heaters with uniform width and dopant concentration using first principles in [29] and through a software-based lumped capacitance model in [19]. The nonuniform heat distribution causes the central area of the sensing resistor to reach temperatures much higher than the outer areas ([20, Fig. 8]). By appropriately shaping the heater width profile for a more uniform temperature distribution, the sensitivity, noise, and linearity of the sensor can be improved [30]. An important step before fabrication is to predict the sensor response by reliable models capturing the various nonlinearities involved [31]. In contrast to commercial modeling software, first-principles-based models provide more transparent, flexible, and reliable tools for analysis, especially when the nonlinear phenomena are dominant.In this paper we develop analytical models for electrothermal position sensor...

show abstract

“…These resistance variations are converted into a detectable voltage which is amplified to produce a signal that is representative of the displacement of the stage. The two heaters per axis are employed in a differential configuration, which improves factors such as the linearity of the sensor output, and helps to reduce the influence of undesirable factors such as ambient temperature and sensor aging (Zhu et al (2011b); Sebastian (2011)). …”

Section: Sensing Principlementioning

confidence: 99%

“…These devices provide a number of potential advantages over comparable macroscale versions including having a smaller footprint, increased bandwidth, lower bulk fabrication costs and easier mass fabrication (Bergna et al (2005); Zhu et al (2011b) in a AFM application (Fowler et al (2012)), where the device was used to replace the existing scanning stage of a commercial AFM. The nanopositioner's stage was fabricated with a series of integrated 3 µm diameter gold features which were used to represent a scan sample, with the AFM being successfully used to perform an open-loop scan of the features in tapping mode.…”

Section: Introductionmentioning

confidence: 99%

Closed-Loop Control of a Novel 2-DOF MEMS Nanopositioner with Electrothermal Actuation*

Fowler

Rakotondrabe

Moheimani

2013

IFAC Proceedings Volumes

View full text Add to dashboard Cite

The design, characterization and control of a novel 2-DoF MEMS nanopositioner is presented, with Z-shaped electrothermal actuators being used to position the device's central stage. Whereas the more commonly-used V-shaped electrothermal actuator only allows displacements in one direction, the design of the Z-shaped beams used in the presented device allows two actuators to be coupled back-to-back to achieve bidirectional motion along each of the two axes. Testing of the device shows that stage displacements in excess of ±5 µm are achievable for both the x and y axes. The device features integrated displacement sensors based on polysilicon electrothermal heaters, which are supplied with an electrical bias voltage that results in Joule heating. The resistance of each heater varies depending on the position of the central stage, with two heaters being used per axis in a differential configuration. The displacement measurements are utilized as part of an implemented closed-loop control scheme that uses both feedforward and feedback mechanisms based on the principle of internal model control. Experimental testing shows that the use of the controller enhances the static and dynamic performance of the system, with particular improvements being seen in the device's reference tracking, response time and cross-coupling rejection.

show abstract

Design, Modeling, and Control of a Micromachined Nanopositioner With Integrated Electrothermal Actuation and Sensing

Cited by 47 publications

References 24 publications

Design and Analysis of Nonuniformly Shaped Heaters for Improved MEMS-Based Electrothermal Displacement Sensing

Design and Analysis of Nonuniformly Shaped Heaters for Improved MEMS-Based Electrothermal Displacement Sensing

A Comprehensive Analysis of MEMS Electrothermal Displacement Sensors

Closed-Loop Control of a Novel 2-DOF MEMS Nanopositioner with Electrothermal Actuation*

Contact Info

Product

Resources

About