Large membrane deflection via capillary force actuation

Barth, Christina; Hu, Xiaoyu; Mibus, Marcel; Reed, Michael L.; Knospe, Carl R.

doi:10.1088/1361-6439/aab372

Cited by 3 publications

(11 citation statements)

References 25 publications

(40 reference statements)

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“…As the results demonstrate, capillary pressure changes due to electrowetting are an effective means for the generation of membrane movement in microdevices, even when electrowetting occurs on only one surface and not that containing the membrane. The displacements obtained (5–15 μm), like those found in a previous investigation of dual-active-surface devices [ 6 ], were significantly larger than those earlier achieved by electrostatic actuation using much higher voltage and power [ 4 ]. This paper’s single-active-surface results opens up a range of possible variations in actuator design.…”

Section: Discussionsupporting

confidence: 76%

“…The membrane displacements obtained for single-active-surface devices are about half of those obtained by their dual active surface counterparts [ 6 ], as predicted by theory [ 10 ]. Just as experiments with those actuators demonstrated, significant improvements in the deflection performance of single-active-surface devices can be achieved by decreasing bridge height.…”

Section: Discussionmentioning

confidence: 81%

“…(The values reported are calculated from an average of 10 measurements taken after the transient has settled). The model relating capillary pressure to membrane deflection that was used in this research is contained in the Appendix of our previous work [ 6 ]. Theoretical values of membrane displacement were calculated using Equation (6) and are presented in Table 2 .…”

Section: Resultsmentioning

confidence: 99%

“…By and large, the alternative technologies have fallen short, either requiring large voltage/power or yielding inadequate valve deflection (<5 μm) [ 2 , 3 , 4 , 5 ]. The authors have recently presented results showing that large deflections of a flexible membrane, like that appearing in LOC devices, can be achieved via a new actuation technique based upon actively controlling capillary pressure [ 6 ]. In this paper we offer new experimental results demonstrating that a simpler actuator design can also achieve substantial membrane deflections, although not as large as those previously reported (>50 μm) [ 6 ].…”

Section: Introductionmentioning

confidence: 99%

“…The authors have recently presented results showing that large deflections of a flexible membrane, like that appearing in LOC devices, can be achieved via a new actuation technique based upon actively controlling capillary pressure [ 6 ]. In this paper we offer new experimental results demonstrating that a simpler actuator design can also achieve substantial membrane deflections, although not as large as those previously reported (>50 μm) [ 6 ]. The membranes tested herein have similar thicknesses and diameters as those reported in the literature.…”

Section: Introductionmentioning

confidence: 99%

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Actuation of Flexible Membranes via Capillary Force: Single-Active-Surface Experiments

Barth

Knospe

2018

Micromachines

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Conventional approaches to microscale actuation, such as electrostatic, have difficulty in achieving large motion at moderate voltages. Recently, actuators relying on the active control of capillary pressure have been demonstrated, with the pressure change caused by electrowetting on a pair of opposing surfaces. In this work, experimental results are presented from five prototype devices in which only a single active surface is used. The results demonstrate that pressure changes induced in a liquid bridge in this manner can produce large deflections (15 μm) of a flexible membrane. Voltages employed in the tests were moderate (≤25 V). The influence of several design variables, such as membrane diameter and thickness, on the membrane deflection are examined. Theoretical predictions are also presented and generally follow the experimental values. Potential sources for the discrepancies between theory and experimental results are discussed. While deflections obtained using a single active surface are not as large as those obtained with two active surfaces, single-active-surface configurations offer a simple route to achieving adequate deflections for lab-on-a-chip microsystems.

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Section: Discussionsupporting

confidence: 76%

Section: Discussionmentioning

confidence: 81%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Actuation of Flexible Membranes via Capillary Force: Single-Active-Surface Experiments

Barth

Knospe

2018

Micromachines

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Actuating droplets with electrowetting: Force and dynamics

Hennig,

Cacucciolo,

Shea

2024

Droplet

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Electrowetting on dielectric (EWOD) allows rapid movement of liquid droplets on a smooth surface, with applications ranging from lab‐on‐chip devices to micro‐actuators. The in‐plane force on a droplet is a key indicator of EWOD performance. This force has been extensively modeled but few direct experimental measurements are reported. We study the EWOD force on a droplet using two setups that allow, for the first time, the simultaneous measurement of force and contact angle, while imaging the droplet shape at 6000 frames/s. For several liquids and surfaces, we observe that the force saturates at a voltage of approximately 150 V. Application of voltages of up 2 kV, that is, 10 times higher than is typical, does not significantly increase forces beyond the saturation point. However, we observe that the transient dynamics, localized at the front contact line, do not show saturation with voltage. At the higher voltages, the initial front contact line speed continues to increase, the front contact angle temporarily becomes near zero, creating a thin liquid film, and capillary waves form at the liquid–air interface. When the localized EWOD forces at the contact line exceed the capillary forces, projectile droplets form. Increasing surface tension allows for higher droplet forces, which we demonstrate with mercury.

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Exploiting Liquid Surface Tension in Microrobotics

Barbot

Ortiz

Bolopion

et al. 2023

Annu. Rev. Control Robot. Auton. Syst.

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Surface tension effects are known to be dominant at the submillimeter scale. Within this context, the literature has extensively described the underlying physics (e.g., surface tension, wetting, surface texturation, and coatings), and capillary forces have been exploited in a variety of applications (e.g., capillary picking, self-alignment, capillary sealing, and capillary bearings). As several stimuli can be used to control liquid menisci, these forces have been used mainly in microrobotics in open loop (i.e., without real-time feedback). However, at least two major sources of uncertainty hinder these forces from working properly in open loop: the variability due to contact-angle hysteresis (the difference between wetting and unwetting) and the variability in the involved volume of liquid. To be able to reject these disturbances, successful sensor integration and associated advanced control schemes need to be embedded in capillary microrobotic microsystems. This article analyzes research contributions in this field from three different perspectives: the stimulus action of the surface tension effect (light, B-field, etc.), the application field (actuation, picking, sealing, etc.), and the sensing and control schemes. Technologically complex developments coexist with elegant and straightforward engineering solutions. Biological aspects of surface tension are not included in this review. Expected final online publication date for the Annual Review of Control, Robotics, and Autonomous Systems, Volume 14 is May 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

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Large membrane deflection via capillary force actuation

Cited by 3 publications

References 25 publications

Actuation of Flexible Membranes via Capillary Force: Single-Active-Surface Experiments

Actuation of Flexible Membranes via Capillary Force: Single-Active-Surface Experiments

Actuating droplets with electrowetting: Force and dynamics

Exploiting Liquid Surface Tension in Microrobotics

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