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11 pages, 3231 KiB

Open AccessArticle

Development of a Flexible Integrated Self-Calibrating MEMS Pressure Sensor Using a Liquid-to-Vapor Phase Change

by Yuhong Kang, Scott Mouring, Albrey de Clerck, Shuo Mao, Wing Ng and Hang Ruan

Sensors 2022, 22(24), 9737; https://doi.org/10.3390/s22249737 - 12 Dec 2022

Cited by 1 | Viewed by 1654

Self-calibration capabilities for flexible pressure sensors are greatly needed for fluid dynamic analysis, structure health monitoring and wearable sensing applications to compensate, in situ and in real time, for sensor drifts, nonlinearity effects, and hysteresis. Currently, very few self-calibrating pressure sensors can be found in the literature, let alone in flexible formats. This paper presents a flexible self-calibrating pressure sensor fabricated from a silicon-on-insulator wafer and bonded on a polyimide substrate. The sensor chip is made of four piezoresistors arranged in a Wheatstone bridge configuration on a pressure-sensitive membrane, integrated with a gold thin film-based reference cavity heater, and two thermistors. With a liquid-to-vapor thermopneumatic actuation system, the sensor can create precise in-cavity pressure for self-calibration. Compared with the previous work related to the single-phase air-only counterpart, testing of this two-phase sensor demonstrated that adding the water liquid-to-vapor phase change can improve the effective range of self-calibration from 3 psi to 9.5 psi without increasing the power consumption of the cavity micro-heater. The calibration time can be further improved to a few seconds with a pulsed heating power. Full article

(This article belongs to the Section Physical Sensors)

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14 pages, 5752 KiB

Open AccessArticle

Design and Fabrication of a Tunable Optofluidic Microlens Driven by an Encircled Thermo-Pneumatic Actuator

by Wei Zhang, Heng Li, Yongchao Zou, Pengpeng Zhao and Zeren Li

Micromachines 2022, 13(8), 1189; https://doi.org/10.3390/mi13081189 - 28 Jul 2022

Cited by 5 | Viewed by 1868

Abstract

This paper presents the design, simulation, fabrication, assembly, and testing of a miniature thermo-pneumatic optofluidic lens. The device comprises two separate zones for air heating and fluid pressing on a flexible membrane. A buried three-dimensional spiral microchannel connects the two zones without pumps or valves. The three-dimensional microfluidic structure is realized using a high-resolution three-dimensional printing technique. Multi-physics finite element simulations are introduced to assess the optimized air chamber design and the low-temperature gradient of the optical liquid. The tunable lens can be operated using a direct-current power supply. The temperature change with time is measured using an infrared thermal imager. The focal length ranges from 5 to 23 mm under a maximum voltage of 6 V. Because of the small size and robust actuation scheme, the device can potentially be integrated into miniature micro-optics devices for the fine-tuning of focal lengths. Full article

(This article belongs to the Special Issue Optical Sensing and Devices)

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15 pages, 20769 KiB

Open AccessArticle

Numerical Study of the Thermal Performance of a Mems Pressure Sensor with Self-Calibration Capabilities

by Albrey de Clerck, Yuhong Kang, Ridge Sibold, Scott Mouring, Hang Ruan and Wing Ng

Sensors 2022, 22(10), 3828; https://doi.org/10.3390/s22103828 - 18 May 2022

Cited by 2 | Viewed by 1618

Abstract

Recent industry trends toward more complex and interconnected systems have increased the demand for more reliable pressure sensors. By integrating a microactuator with a pressure sensor, the sensor can self-calibrate, eliminating the complexities and costs associated with traditional sensor calibration methods to ensure reliability. The present work is focused on furthering understanding and improving the thermal performance of a thermopneumatic actuated self-calibrating pressure sensor. A transient numerical model was developed in ANSYS and was calibrated using experimental testing data. The numerical model provided insights into the sensor’s performance not previously observed in experimental testing. Furthermore, the model was utilized for two design studies. First, it was found that a substrate with low thermal conductivity and high thermal diffusivity is ideal for both the sensor’s efficiency and a faster transient response time. The second design study showed that decreasing the size of the sealed reference cavity lowers power consumption and transient response time. The study also showed that reducing the cavity base dimension has a greater effect on lowering power consumption and response time. Overall, the present work increases understanding of the self-calibrating pressure sensor and provides insight into potential design improvements, moving closer to optimized self-calibrating pressure sensors. Full article

(This article belongs to the Section Physical Sensors)

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27 pages, 16459 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Review of Electrothermal Micromirrors

by Yue Tang, Jianhua Li, Lixin Xu, Jeong-Bong Lee and Huikai Xie

Micromachines 2022, 13(3), 429; https://doi.org/10.3390/mi13030429 - 10 Mar 2022

Cited by 15 | Viewed by 5051

Abstract

Electrothermal micromirrors have become an important type of micromirrors due to their large angular scanning range and large linear motion. Typically, electrothermal micromirrors do not have a torsional bar, so they can easily generate linear motion. In this paper, electrothermal micromirrors based on different thermal actuators are reviewed, and also the mechanisms of those actuators are analyzed, including U-shape, chevron, thermo-pneumatic, thermo-capillary and thermal bimorph-based actuation. Special attention is given to bimorph based-electrothermal micromirrors due to their versatility in tip-tilt-piston motion. The exemplified applications of each type of electrothermal micromirrors are also presented. Moreover, electrothermal micromirrors integrated with electromagnetic or electrostatic actuators are introduced. Full article

(This article belongs to the Special Issue Optical MEMS, Volume III)

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10 pages, 3343 KiB

Open AccessArticle

Thermopneumatic Soft Micro Bellows Actuator for Standalone Operation

by Seongbeom Ahn, Woojun Jung, Kyungho Ko, Yeongchan Lee, Chanju Lee and Yongha Hwang

Micromachines 2021, 12(1), 46; https://doi.org/10.3390/mi12010046 - 1 Jan 2021

Cited by 5 | Viewed by 4380

Abstract

Typical pneumatic soft micro actuators can be manufactured without using heavy driving components such as pumps and power supplies by adopting an independent battery-powered mechanism. In this study, a thermopneumatically operated soft micro bellows actuator was manufactured, and the standalone operation of the actuator was experimentally validated. Thermopneumatic actuation is based on heating a sealed cavity inside the elastomer of the actuator to raise the pressure, leading to deflection of the elastomer. The bellows actuator was fabricated by casting polydimethylsiloxane (PDMS) using the 3D-printed soluble mold technique to prevent leakage, which is inherent in conventional soft lithography due to the bonding of individual layers. The heater, manufactured separately using winding copper wire, was inserted into the cavity of the bellows actuator, which together formed the thermopneumatic actuator. The 3D coil heater and bellows allowed immediate heat transfer and free movement in the intended direction, which is unachievable for conventional microfabrication. The fabricated actuator produced a stroke of 2184 μm, equivalent to 62% of the body, and exerted a force of 90.2 mN at a voltage of 0.55 V. A system in which the thermopneumatic actuator was driven by alkaline batteries and a control circuit also demonstrated a repetitive standalone operation. Full article

(This article belongs to the Special Issue 3D Printing of MEMS Technology)

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11 pages, 5087 KiB

Open AccessArticle

Design and Analyses of a Transdermal Drug Delivery Device (TD³) †

by Jennifer García, Ismael Ríos and Faruk Fonthal Rico

Sensors 2019, 19(23), 5090; https://doi.org/10.3390/s19235090 - 21 Nov 2019

Cited by 11 | Viewed by 3037

Abstract

In this paper, we introduce a novel type of transdermal drug delivery device (TD³) with a micro-electro-mechanical system (MEMS) design using computer-aided design (CAD) techniques as well as computational fluid dynamics (CFD) simulations regarding the fluid interaction inside the device during the actuation process. For the actuation principles of the chamber and microvalve, both thermopneumatic and piezoelectric principles are employed respectively, originating that the design perfectly integrates those principles through two different components, such as a micropump with integrated microvalves and a microneedle array. The TD³ has shown to be capable of delivering a volumetric flow of 2.92 × 10⁻⁵ cm³/s with a 6.6 Hz membrane stroke frequency. The device only needs 116 Pa to complete the suction process and 2560 Pa to complete the discharge process. A 38-microneedle array with 450 µm in length fulfills the function of permeating skin, allowing that the fluid reaches the desired destination and avoiding any possible pain during the insertion. Full article

(This article belongs to the Special Issue Lab-on-a-Chip Technology)

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809 KiB

Open AccessArticle

A Hybrid Thermopneumatic and Electrostatic Microvalve with Integrated Position Sensing

by Joseph A. Potkay and Kensall D. Wise

Micromachines 2012, 3(2), 379-395; https://doi.org/10.3390/mi3020379 - 27 Apr 2012

Cited by 13 | Viewed by 7504

Abstract

This paper presents a low-power hybrid thermopneumatic microvalve with an electrostatic hold and integrated valve plate position sensing. This combination of actuators in a single structure enables a high throw and force actuator with low energy consumption, a combination that is difficult to otherwise achieve. The completed 7.5 mm × 10.3 mm × 1.5 mm valve has an open flow rate of 8 sccm at 600 Pa, a leak rate of 2.2 × 10⁻³ sccm at 115 kPa, a open-to-closed fluidic conductance ratio of nearly one million, an actuation time of 430 ms at 250 mW, and a required power of 90 mW while closed. It additionally requires no power to open, and has a built-in capacitive position sensor with a sensitivity of 9.8 fF/kPa. The paper additionally presents analytical models of the valve components, design tradeoffs, and guidelines for achieving an optimized device. Full article

(This article belongs to the Special Issue Micro Flow Controllers)

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