Dielectrowetting for Digital Microfluidics Principle and Application A Critical Review

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Langmuir. 2021 Jun ane; 37(21): 6414–6422.

Continuous Droplet-Actuating Platforms via an Electrical Field Gradient: Electrowetting and Liquid Dielectrophoresis

Received 2021 Feb three; Revised 2021 May 7

Supplementary Materials

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Abstruse

This work develops a technology for actuating aerosol of any size without the requirement for loftier voltages or active command systems, which are typically found in competitive systems. The droplet actuation relies on two microelectrodes separated past a variable gap altitude to generate an electrostatic gradient. The physical machinery for the droplet motion is a combination of liquid dielectrophoresis and electrowetting. Investigating the system beliefs as a function of the driving frequency identified the relative contribution of these two mechanisms and the optimum operating atmospheric condition. A fixed betoken frequency of 0.five kHz actuated diverse liquids and contaminants. Droplet actuation was demonstrated on several platforms, including linear, radial-symmetric, and bilateral-symmetric droplet motion. The electrode designs are scalable and can be fabricated on a flexible and optically transparent substrate: these key advancements will enable consumer applications that were previously inaccessible. A self-cleaning platform was also tested nether laboratory weather condition and on the road. This technology has meaning potential in microfluidics and self-cleaning platforms, for example, in the automotive sector to make clean trunk parts, camera covers, and sensors.

Introduction

Since the pioneering work on microfluidics in the early on 1990s, at that place has been an ever-increasing enquiry focus on droplet manipulation in both open and closed configurations.¹⁻⁵ However, improving and introducing new paradigms to minimize the device complexity is necessary to exploit this technology for large-book applications.

Surface tension and capillary forces are the dominant factors in microfluidic systems due to the reduced operating scale. Electrowetting-on-dielectric (EWOD) and dielectrowetting (DW) are the 2 commonly used techniques to actuate droplets past electric means.^6,vii EWOD is a method to actuate conductive liquids by manipulating the interfacial surface energy in the presence of an electric double layer. A typical EWOD arrangement comprises of a conductive droplet sandwiched between two plates, where the top plate is a common ground and the bottom plate consists of an array of individual signal electrode pads.⁸ Nevertheless, other electrode configurations are likewise possible.⁹

Although EWOD has been widely studied,^10,11 the method is restricted by limitations such as contact bending saturation and actuation incompatibility with not-conductive liquids.^six,vii,12 In contrast, DW has been gaining attention for overcoming the limitations of electrowetting.^13,14 The ascendant mechanism for DW is liquid dielectrophoresis (L-DEP), which exploits the electric majority force produced nearly the liquid–solid interface of a droplet by applying a non-uniform electric field.¹⁵ Droplet manipulation with L-DEP has attracted a peachy deal of research interest, notably in the fields of optofluidics and lab-on-a-chip microfluidics.¹⁶⁻¹⁹

Recently, L-DEP actuation on a single plate using interdigitated electrodes (IDEs) design was demonstrated for splitting and transporting a diverseness of liquid droplets.^xx This study was followed by investigating antibiofouling functioning with a slippery lubricant-infused surface.²¹ Later, a programmable droplet-actuating platform based on 50-DEP demonstrated the droplet actuation with varying volumes using an iterative fractal approach.²² Furthermore, the exploitation of high electrical fields using IDEs with a modest gap altitude reduced the operating voltages (100 V or less).

The actuation of sessile droplets using EWOD and DW can be explained through the asymmetric electrostatic forces changing the contact angle on one side of the droplet, thus causing motion. An array of electrodes can be situated on a single plate and controlled using an electronic control system.²² The application of this technique on a big surface for a cleaning platform is complicated and plush and may also crave a droplet sensing method within a feedback control loop. A few examples are vision systems, fluorescence spectroscopy, capacitive sensing, and impedance measurements.²³⁻²⁶ This limitation is primarily driven by the IDEs fixed surface expanse and varying droplet volume.

Continuous electrowetting is recommended in large-scale platforms for its simplicity and scalability. The initial attempts showed that continuous actuation was viable using liquid metals in a closed aqueduct.²⁷ The electrowetting technique relied on the voltage drop across a sparse layer of aqueous electrolyte to produce droplet motility. The introduction of nonlinear circuit elements enabled the continuous droplet actuation. For example, embedded diodes achieved continuous droplet motion using induced electro-osmotic and electrowetting furnishings.²⁸⁻³¹

Furthermore, the continuous droplet actuation has been reported without requiring external input energy using a wettability gradient.³² The bidirectional droplet motion based on the slope liquid-infused surface was demonstrated for long-distance droplet actuation.³³ There are, as well, new methods to transport microscopic liquid layers based on a unique topological construction.³⁴ The topological fluid diode enabled long-altitude directional liquid transport.³⁴

Here, we demonstrate a continuous droplet motion based on variable interdigitated electrodes (VIDEs). The VIDEs approach represents a significant simplification compared to the traditional electric methods, leading to advantages in terms of reduced costs, control organization requirements, and reliability on dissimilar scales. The foremost advantage is actuating droplets with dissimilar volumes without a command system. Additionally, the VIDEs tin can ship dielectric liquids, an operational limitation of the embedded diodes that require conductive liquids. The technological advancements presented hither introduce a continuous droplet motion for various applications, including a cleaning platform for optical sensors and cameras, in addition to other chemical and biological devices based on droplet-based microfluidics.

Theoretical Background

The combined working mechanism for DW and EWOD tin be explained by the Korteweg–Helmholtz equation of liquid trunk force density.³⁵

1

Here, ρ and ρ_f are the density and free electric accuse density of the liquid, respectively, ϵ is the liquid permittivity, and E is the electrical field. The bold letters are vector quantities. EWOD and DW effects are frequency-dependent, and thus, the applied signal frequency determines the droplet actuation machinery. Note that a greater EWOD outcome is possible using a liquid with higher electrical electrical conductivity. However, the ionic conductivity to a higher place a critical frequency is negligible, and the liquid behaves every bit a dielectric (ρ_f = 0). The electrostriction term is similarly ignored when the liquid is incompressible.³⁵ Therefore, the indications from eq 1 is that the larger values of the electric field and liquid permittivity generate a greater Fifty-DEP force.

The VIDEs exploit the electric field'southward favorable scaling by varying the electrode gap distance to generate an electrostatic net forcefulness, thus causing a continuous droplet motion. Figure ​ ane elaborates on the working mechanism using a ii-dimensional (2d) COMSOL Multiphysics simulation to show the change in the electric field across the electrode. The electric field decays faster with shorter electrodes, resulting in a higher field slope and net force. The dielectric breakup was a pattern constraint and, therefore, very high voltages or a gap distance lower than 20 μm was avoided. Please refer to the Supporting Information for more than details about the simulation setup and purlieus conditions.

2d COMSOL Multiphysics simulation results showing the distribution of electric field between the electrode fingers at two unlike lengths (10 and 5 mm). The gap distance was between 200 and xx μm. The applied voltage was 75 5, and the subfigure shows the cut plane "ten" from where the readings were taken.

Experimental Department

Experimental Setup

The experiments were carried out in a cleanroom maintained at 20 °C. An alternating current (AC) betoken was supplied from a function generator to a signal amplifier and then transmitted to the device. The experimental setup consisted of a testing station with pogo pins for electrical contacts. The testing station was on a leveled bench, and the signals were monitored using an oscilloscope. A microcontroller collection a simple relay module via iii reed relays for switching the electrical signals. MATLAB was the interface to connect, control, and salvage the media files. The actuation time was determined from the videos to summate the actuation speed. The droplet volume was regulated using a micropipette (±0.i μL). Please refer to the Supporting Information (see Tabular array S1) for the list of testing liquid and their properties.

Design and Fabrication

The typical VIDEs consist of interdigitated electrodes with a variable gap distance (D _north) and length (Fifty), as depicted in Figure ​ 2A. The device incorporates 4 separate layers (see Figure ​ twoB). The start layer was a substrate (borosilicate glass), the 2nd layer was an array of VIDEs (aluminum, 70 nm in thickness), and an insulating layer protected the electrodes. Photosensitive epoxy resin (SU-8) with a nominal thickness of 0.5 μm was selected here. Lastly, the SU-eight layer was functionalized with a hydrophobic self-assembled monolayer (SAM), octadecyltrichlorosilane (OTS), to obtain a hydrophobic top-layer for ameliorate functioning with a contact bending of 110° (±4°). The OTS coating is widely used in electrowetting,^36,37 and several other studies take already explored fabricating different SAM-functionalized SU-8 layers.³⁸⁻⁴⁰ Please refer to the Supporting Information for more than details on the fabrication process.

(A) Full general overview of the device moving a droplet. The important parameters are the electrode length (L) and a varying gap distance (D _north). The electrodes are connected to a DC or AC voltage source to generate a variable non-uniform electric field along the length of the device. (B) 2D schematic of a typical device: (i) hydrophobic layer, (ii) insulating layer, (3) electrode patterns, and (iv) substrate.

The surface modification using a lubricant layer reduced the contact angle hysteresis associated with the pinning forces at the droplet contact line.⁴¹ Oil-based lubricant layers are commonly used to produce reversible spreading of the droplets in low-voltage electrowetting studies.⁴²⁻⁴⁴ We considered this approach to take authentic measurements using lower voltages. The selected lubricant layer was mineral oil, with an estimated thickness of 100 μm. The thickness of the oil layer was controlled past regulating the oil-injected volume over a confined area and then spin-coated to aid uniformity. The surface treatment modified the droplet-sliding angle (with a volume of xv μL) from fifteen° to 1°. A superhydrophobic coating using SAM OTS is an culling method to minimize the contact angle hysteresis without using any lubricant treatment.³⁸ Furthermore, the actuation performance is dependent on the practical voltage, in which higher voltages can be employed for less hydrophobic surfaces up to the dielectric breakdown limit.

Betoken Management

Droplet actuation on a large calibration often requires a multilayer structure for electrode contacts, with betoken management complications. The embedded bespeak patterns connect three separate paths (signal and common ground) from a source to whatsoever number of electrodes, removing the pattern requirement to fabricate many electric contact points (come across Effigy ​ three). Combining the multiplexing technique shown here with the electrode design shown in Effigy ​ 2 tin produce droplet actuation without size limitations.

Interlinked bespeak flow between 3 sets of VIDEs. The multiplexing technique is similar to a multiple path maze that follows a spiral loop, with each pattern consisting of a common ground final. This approach requires only a single-layer photolithography procedure to connect multiple electrodes, thereby reducing the costs and fabrication complications of a multilayer design.

Results and Discussion

Spontaneous Droplet Actuation

The ability to dispense droplets of any size is a fundamental requirement for droplet-based microfluidics. Compared to other droplet-actuating methods, the electric-based platforms are non well suited to see this critical performance criterion.⁴⁵ Here, the continuous droplet actuation is verified with different volumes (meet Figure ​ 4A). The variable gaps in the VIDEs produced a internet forcefulness across the electrode pad to initiate the droplet motion regardless of its position or size. Furthermore, the electrode patterns strip the need for a complex control arrangement or the necessity to fabricate a large array of small electrodes, thereby reducing the overall complexity and costs.

Experimental results characterizing the boilerplate droplet speed forth the length of an electrode pad. (A) Elevation view images of droplets with different volumes moving on a typical VIDEs (L = 10 mm and D _n = xx–200 μm). (B) Comparison the actuation speed at different voltages with a fixed frequency of 20 kHz. The testing liquid was DI water with a volume of six μL, verified on ii different pad size lengths. (C) Analysis of the actuation speed for dissimilar volumes of droplets with a fixed voltage of 100 V at a bespeak frequency of xx kHz.

From an application perspective, lower operating voltages are always desirable to avert complex electronics and to help electromagnetic compatibility. The introduction of the lubricant layer reduced the surface adhesion, resulting in lower operating voltages (equally low as 30 V). Yet, the actuation on a plain OTS surface was only possible at higher voltages (100 V or more than). Additionally, applying a modulated pulse AC signal (2 Hz) resulted in a smoother actuation for higher voltages or a pace-by-step motion beyond the VIDEs using lower voltages (see Motion-picture show S1). Two electrode geometries with different lengths were tested to investigate the effect of applied voltage (encounter Figure ​ 4B) and droplet book (see Figure ​ fourC) on the device's functioning. The experimental results in Figure ​ 4 are based on a lubricant surface treatment to minimize the applied voltage.

The droplet size has a major impact on the actuation speed. Droplets with different volumes were tested to investigate the influence of the droplet size on the actuation speed. The actuation process required the droplet to exist over at least one pair of VIDEs; therefore, in the current design, the droplet diameter had to be no less than 500 μm. Yet, a larger net forcefulness is generated when a bigger droplet is situated over multiple VIDEs.

The experiments verified that the shorter electrode delivered a improve performance. The enhanced performance was considering of the sharper changes in the electrode gap distance, producing larger forces. In contrast, the shorter electrodes comprehend a smaller surface area that requires an electronic switching method for larger platforms.

Frequency-Dependent Actuations

The frequency-dependent analysis of aqueous droplets is disquisitional to better understand the relationship between EWOD and L-DEP.^46,47 Electrowetting and L-DEP actuation mechanisms boss microfluidics in depression- and loftier-betoken frequencies, respectively. The utilization of the VIDEs allows the integration of 50-DEP and EWOD domains onto a single device using a suitable signal frequency. A dielectrophoretic response was generated using a variable electric field to a higher place the critical betoken frequency. Alternatively, a variable electrical double layer effect was obtained in a conductive liquid using a signal below the critical signal frequency.

The water-based solutions with a different electrical electrical conductivity were tested at room temperature using a wide range of signal frequencies (0.five kHz to 1.five MHz at 75 V RMS and a DC voltage applied at 75 V). The results are summarized in Figure ​ 5. The testing liquids, saturated potassium chloride (KCl) solution and DI h2o, represent the two extreme examples of electric electrical conductivity, and 0.006 Yard KCl solution had similar backdrop to the natural rain.

Frequency-dependent study for water and KCl solutions with different concentrations tested using DC and AC signal frequencies. The fixed electrode geometry has dimensions of L = 10 mm and D _north = twenty–200 μm.

The highest droplet actuation speed was in the low-frequency spectrum. For instance, the highest dependence on the frequency for DI water was registered between 0.five kHz and x kHz. This is expected equally the disquisitional frequency for DI h2o is around five kHz.⁴⁷ However, the critical frequency tin can slightly vary depending on the device parameters, such as the insulating thickness and the electrode gap distance. The KCl aqueous solutions behave differently considering their conductivities are much higher than that of DI water, with the estimated disquisitional frequencies beingness more than 500 kHz, as experimentally reported elsewhere.⁴⁷

The testing of dielectric liquids highlighted the optimum frequency at which the liquid experienced the highest dielectrophoretic response. The testing results for the dielectric liquids are shown in Figure ​ 6. The actuation of dielectric droplets (i.e., propylene carbonate) was possible at lower voltages due to their superior chemical backdrop, such as high surface tension and large relative permittivity.^{thirteen,twenty} The highest frequency response for the propylene carbonate was at 20 kHz, which was consistent with that of previous studies.²⁰

Testing results of dielectric liquids. The average droplet actuation speed is demonstrated here, highlighting the optimum applied signal frequency for each liquid. The applied voltage was 75 V.

The liquid'south electrical conductivity and permittivity change the critical frequency, meaning that the dielectrophoretic response is different for every liquid. Furthermore, employing a DC voltage resulted in nearly no actuation for dielectric liquids and lower performance for conductive liquids. Moreover, depending on the application, a DC voltage source might be favorable because of simpler control requirements.

Big-Scale Droplet Actuation

Manipulating droplets using simpler and cheaper techniques is cardinal to many lab-on-a-bit and surface-cleaning platforms. A large-scale device with the interlinked betoken design (encounter Figure ​ 3) immune parallel and continuous droplet actuation with different volumes without increasing the complication or fabrication costs.

A fixed sine-wave point frequency of 0.five kHz was selected for the experiments. The active surface area of the electrodes was approximately (4 × 4 cm). Two designs are suggested here (see Figure ​ 7A,B), integrated with the interlinked indicate pattern (shown in Figure ​ 3), to demonstrate linear and radial-symmetric droplet motions on a large scale. There is besides a pocket-size overlap region between every VIDEs for a shine droplet actuation (see Figure ​ 7D).

Three electrode designs to generate a continuous droplet motion on a large calibration. The direction of the droplet motion is highlighted with arrows. (A) Linear droplet motion using seven VIDEs based on the interlinked flow signal shown in Effigy ​ 3. (B) Radial-symmetric droplet motion based on the interlinked flow signal. (C) Bilateral-symmetric droplet motion without an electronic control system. (D) Zoomed-in paradigm, showing the overlapped region between two electrode pads.

The linear droplet motion (Figure ​ sevenA) uses an array of shorter VIDEs to activate a range of droplets, resulting in a higher actuation speed. The blueprint is suitable for a large-scale cleaning platform, where the linear droplet move is advisable, that is, for automotive applications (see the exam results in Figure ​ 8A). The radial-symmetric droplet move (see Figure ​ 7B) is carried out on a sunflower design with different electrode lengths. The droplet movement is validated by introducing random water aerosol on the surface with different volumes so that the device moves them to the outer regions for disposal (meet Figure ​ 8B). This pattern is ideal for applications where radial-symmetric droplet motion is necessary, such equally cleaning electronic sensors on a flat surface. The surface area of the blank gaps in the pattern increases in the outward direction past the golden ratio. The droplets in the inner regions are continuously transported to the outer areas to form larger droplets, eliminating the touch of large gaps in the outer areas of the device. Additionally, the droplet size must exist smaller than the length of the smallest VIDEs. Otherwise, the droplet goes dorsum and along between the smaller pads. The alternative solution dedicates a divide voltage signal for every electrode pad.

Summary of the examination results showing DI water droplets moving on the surface with oil lubricant treatment. There is a 5 s delay between every switching step. (A) Linear droplet motion based on the design shown in Figure ​ 7A using 75 V. (B) Radial-symmetric droplet move based on the design shown in Effigy ​ 7B using 90 5. (C) Bilateral-symmetrical droplet movement based on the blueprint shown in Figure ​ sevenC using 90 V.

A large-scale design is presented in another approach based on the bilateral-symmetric droplet motion without any electronic command systems (run into Effigy ​ 7C). The simple design requires only two signals and a mutual ground to operate (see the test results in Figure ​ 8C). The opposing electric forces in the center of the device (between the 2 VIDEs) could generate a lag in the actuation process and thus foreclose any motion. An effective solution is a basic switch machinery to eliminate the opposing forces (i.e., by switching the VIDEs separately ON-OFF, OFF-ON, ON-OFF ...).

Although previous studies demonstrated droplet movement in a discrete style, the scale of the performance was limited, with applied voltages in backlog of hundreds of volts. The fixed signal frequency was another simplifying factor to minimize the effect of electrical conductivity on the performance. Furthermore, the fabrication of a large-scale device using transparent electrodes expands the application of this technology, that is, to clean optical sensors or cameras. Please refer to the Supporting Information for examples of transparent devices (see Figure S1 and Figure S2).

Surface Cleaning Application

The application of this technology on a large scale, that is, in the automotive industry, requires cleaning from contaminants such as clay, soil, sand, so on. The epitome clarity received by the sensors and cameras under a wide range of environmental weather is critical for road safety.⁴⁸

The signal frequency was fixed to 0.v kHz at 100 V. Nosotros verified the removal of sand and clay contaminants with a diameter of x μm to 1000 μm using a rainwater droplet (come across Figure ​ ixA,B). Additionally, the removal of a typical suspension liquid (mud rain) was demonstrated (encounter Figure ​ nineC). The actuation of mud rain, sand, dirt, and rainwater showed the awarding of this technology for a applied scenario, for example, a motorcar traveling on the highway. The actuation of aerosol in microfluidics has all-encompassing biological applications.⁴⁹ The VIDEs actuated semi-skimmed milk droplets to demonstrate the flexibility of the platform (see Figure ​ 9D). Semi-skimmed milk contains fat, proteins, and vitamins, including A, B3, B5, and D.

Summary of the exam results, showing the top view of unlike aerosol moving on the surface with lubricant treatment. (A) Rain droplet moving dirt contaminants (700–1000 μm), (B) rain droplet moving sand (10–150 μm), (C) actuation of suspension of a muddy water droplet, and (D) actuation of semi-skimmed milk droplet.

A cocky-cleaning cover lens that systematically removes unlike contaminants and liquids without a control arrangement is advantageous in many applications. An alternative approach to the previous designs is too proposed for a miniature cover lens (10 × x mm) using integrated VIDEs with unlike lengths. Figure ​ 10 shows the testing results of moving a suspension of mud rain. The experiment verified the circular symmetric droplet actuation away from the center of the lens using a single voltage source.

(A) Top view images (1–4) of a small-scale device (10 × 10 mm) that demonstrated a round symmetrical droplet movement. The testing liquid was mud rain. (B) Part of the electrode design that consists of three VIDEs with different lengths.

The encompass lens can be attached to the surface for easy integration with any device. The experiments verified the rapid cleaning of a camera lens positioned horizontally. Nevertheless, a simpler pattern similar to the i shown in Figure ​ 9 is more suitable for an inclined surface where the actuation direction is stock-still and linear.

A cocky-cleaning comprehend lens that prevents the build-upwards of contaminants could be an auxiliary add-on to sensors and cameras. Furthermore, the actuation of complex fluids (such as mud rain) is advantageous, which could either obscure the view or, when evaporated, exit a stain on the lens. Even though mechanical cleaning may nevertheless exist necessary, minimizing its use for other solid contaminants is all the same a priority for many applications.

The cleaning platform was mounted on a camera lens and tested (encounter the experimental setup in Figure ​ 11A). The testing results verified the reliable and systematic cleaning of the surface against solid contaminants (see Effigy ​ 11B–E) and mud pelting (run across Figure ​ 11F–I) to maintain a clear view during operation. The testing liquids were DI h2o and mud rain, yet other liquids are similarly compatible, including isopropyl alcohol. Figure ​ 11J shows the luminance beyond the rainbow design during the cleaning process. The scanned regions are indicated with a dotted line.

Summary of the exam results for cleaning a camera cover lens. The black arrow shows the direction of the droplet actuation. (A) Overview of the experimental setup with a rainbow panel, device, and a camera, (B) clean surface, (C) calculation grit particles to the surface, (D) adding a droplet, (E) cleaning the surface of the device, (F) adding another droplet to the surface, (K) cleaning the device, (H) adding a droplet, and (I) cleaning the device. (J) Sit-in of the cleaning process using a 2D plot showing the luminance across the rainbow blueprint (from B–E).

There is a technological demand for an electronic cocky-cleaning platform to remove the surface contaminants on cameras, LIDAR, and sensors, which poses a growing engineering challenge to automotive manufacturers, specifically for cocky-driving cars.⁴⁸ The cover lens was besides tested on the road by mounting it on a camera and connecting it to a car battery via a ability inverter. The device provided skillful visibility during the test when compared to a controlled camera without the VIDEs cover lens. The testing was carried out when the vehicle was stationary and similarly when on the route, moving at 40 mph. Please refer to the Supporting Data for more details (encounter Effigy S3 and Movie S3).

Conclusions

A novel method was successfully demonstrated based on the continuous actuation of aerosol with unlike volumes (1–thirty μL) using L-DEP and EWOD. The reported results verified the droplet actuation at lower voltages (as depression as thirty V). At higher voltages (100 V or more), actuation speeds of up to 36 mm due south^–1 were registered for DI water (6 μL) on a five mm long electrode pad. A stronger electrical field with a deeper penetration at a higher voltage may generate even larger forces, and therefore, further refinement is feasible.

The frequency-dependent written report for different liquids at loftier- and low-frequency limits highlighted the all-time operating parameters. Furthermore, a fixed applied frequency (0.5 kHz) simplified the actuation process. This value was dependent on the liquid properties and may vary for other applications. Furthermore, the interlinked point pattern was another simplifying addition for large-calibration platforms.

The principal limitation of the VIDEs is the unidirectional droplet movement, limiting its awarding. However, bidirectional actuation is as well feasible by using ii sets of electrode patterns with an opposite variation of gap distance. Furthermore, a multilayer electrode design could also produce droplet motility in 2D.

The continuous droplet move of VIDEs has several uses, notably in the fields of lab-on-a-chip microfluidics to transport droplets for analysis. The engineering science is similarly suitable for automotive applications in cleaning sensors and cameras. The droplet actuation on different scales promises significant advantages over the current technologies, including an overall reduction in the device complexity, operating voltage, and fabrication costs. The improvements presented hither open many avenues for future innovative applications based on the VIDEs configuration.

Acknowledgments

We are grateful for the supervision guidance and fiscal support provided by Jaguar Land Rover. The authors would likewise like to thank Jidong Jin for helpful technical discussions.

Supporting Information Available

The Supporting Information is available free of accuse at https://pubs.acs.org/doi/10.1021/acs.langmuir.1c00329.

• Detailed fabrication process, testing liquids, details well-nigh the testing on the road, geometries of the VIDEs, and details about the simulation models (PDF)

• Droplet actuation beyond the VIDE'southward (MP4)

• Device scalability (MP4)

• Application of VIDEs in laboratory settings and on the route (MP4)

Author Present Address

^† Jaguar Land Rover Express, National Automotive Innovation Center, Coventry, CV4 7AL, United kingdom.

Notes

Engineering and Concrete Sciences Enquiry Council (EPSRC), U.K., through the Industrial Case Award EP/P510476/1.

Notes

The authors declare no competing financial interest.

Supplementary Cloth

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Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8397340/

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