A Fast Liquid-Metal Droplet Microswitch Using EWOD-Driven Contact-Line Sliding

The micro-fluidic inertial switch based on liquid metal utilizes the moving mercury droplet to close the switch under the action of acceleration, which is characterized by no moving parts, small contact resistance, long service life and large current. In addition to the requirement of response time, accuracy and reliability, the micro-fluidic inertial switch needs to overcome the impact of the ambient vibration. The influence of the ambient vibration on the performance of switch is investigated by loading pulse or sinusoidal interference signals in the X, Y and Z direction. The numerical results suggest that the performance of micro-fluidic inertial switch is greatly affected by impact interference signal in X sensitive direction as compared with low frequency harmonic signal. If the impact signal with high amplitude lasts only for a short time, the wrong operation might also occur. The interference signals in insensitive direction have a relatively small impact on the performance of switch, and the impact of interference signal can be reduced by reasonable structural design. Finally, anodic bonding, deep reactive ion etching (DRIE) and sputtering technique are adopted to fabricate the micro-fluidic inertial switch. The acceleration threshold of the prototype is tested. The experiment results agree with the numerical results, which indicate that the simulation method is valid.

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“…Therefore, the volume of mercury droplet is estimated as bellow. 10 V = π R 3 e 3 2 − 3 cos θ e + cos 3 θ e…”

Section: A Micromachining Processmentioning

confidence: 99%

Vibration interference analysis and verification of micro-fluidic inertial switch

Liu

Yang

et al. 2014

AIP Advances

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“…[6][7][8] Among these methods, EWOD has become a popular topic and a useful technology in academic research worldwide relative to other driving forces or control methods due to special advantages, such as straightforward fabrication, low cost, compatibility with conductive or polar fluids, and convenient programmable control. The effect changes the electron distribution in droplets, and the force of static electricity changes the contact angle of droplets, enabling diverse applications, such as micro-valves, 9 focal lenses, [10][11][12][13] fibers, 14,15 screens, 16,17 transport, [18][19][20][21][22][23][24] printing, 25 transistors, 26 electrical switches, 27,28 thermal control 29,30 and thermal management. 31 An increasing number of studies have applied the advantage of EWOD to be amplified in micro-systems, particularly for micro-optical devices, because droplets can adjust the focal length by changing the radius of curvature, using the properties of droplet flexibility with an applied voltage.…”

Section: Introductionmentioning

confidence: 99%

Optimization and limit of a tilt manipulation stage based on the electrowetting-on-dielectric principle

et al. 2017

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This work designed a new tilt manipulation stage based on the electrowetting-on-dielectric (EWOD) principle as the actuating mechanism and investigated the performance of that stage. The stage was fabricated using a universal MEMS (Micro-Electro-Mechanical System) fabrication method. In the previously demonstrated form of this device, the tilt stage consisted of a top plate that functions as a mirror, a bottom plate that was designed for changing the shape of water droplets, and supporters that were fixed between the top and bottom plate. That device was actuated by a voltage applied to the bottom plate, resulting in a static electric force actuating the shape change in the droplets by moving the top plate in the vertical direction. Previous experimental results indicated that that device can tilt at up to ±1.8°, with a resolution of 7 μm in displacement and 0.05° in angle. By selecting the best combination of the dielectric layer, the tilt angle was maximized. The new device, fabricated using a common and straightforward fabrication method, avoids deflection of the top plate and grounding in the bottom plate. Because of the limit of Teflon and other MEMS materials, this device has a tilt angle in the range of 3.2-3.5° according to the experimental data for friction and the EWOD device limit, which is close to 1.8°. This paper also describe the investigation of the effects of various parameters, e.g., various dielectric materials, thicknesses, and droplet type and volume, on the performance of the stage. The results indicate that the apparent frictions coefficient of the solid-liquid interface may remain constant, i.e., the friction force is proportional to the normal support force and the apparent frictions coefficient.

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“…9,10 The electrowetting on dielectric (EWOD) phenomenon 11 is one of the most common actuation mechanisms used in DMF and has been widely adopted in biomedical [12][13][14][15][16] and, sometimes, other applications. 17,18 Traditional EWOD devices, however, still require an external high-voltage supply and switching circuitry, which require significant custom development to realize compact systems. 19 We report EWOD-based DMF with finger-actuated voltage generation on chip, or F-DMF, to eliminate the need for external voltage sources.…”

Section: Introductionmentioning

confidence: 99%

EWOD (electrowetting on dielectric) digital microfluidics powered by finger actuation

et al. 2014

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We report finger-actuated digital microfluidics (F-DMF) based on the manipulation of discrete droplets via the electrowetting on dielectric (EWOD) phenomenon. Instead of requiring an external power supply, our F-DMF uses piezoelectric elements to convert mechanical energy produced by human fingers to electric voltage pulses for droplet actuation. Voltage outputs of over 40 V are provided by single piezoelectric elements, which is necessary for oil-free EWOD devices with thin (typically <1 μm) dielectric layers. Higher actuation voltages can be provided using multiple piezoelectric elements connected in series when needed. Using this energy conversion scheme, we confirmed basic modes of EWOD droplet operation, such as droplet transport, splitting and merging. Using two piezoelectric elements in series, we also successfully demonstrated applications of F-DMF for glucose detection and immunoassay. Not requiring power sources, F-DMF offers intriguing paths for various portable and other microfluidic applications.

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A Fast Liquid-Metal Droplet Microswitch Using EWOD-Driven Contact-Line Sliding

Cited by 88 publications

References 28 publications

Vibration interference analysis and verification of micro-fluidic inertial switch

Vibration interference analysis and verification of micro-fluidic inertial switch

Optimization and limit of a tilt manipulation stage based on the electrowetting-on-dielectric principle

EWOD (electrowetting on dielectric) digital microfluidics powered by finger actuation

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