Digital Microfluidic Droplet Printing via Electrowetting
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Solution Overview
Problem
Current methods for printing large arrays of small liquid volumes are limited by minimum volume dispensing and throughput, are often expensive, and time-consuming, particularly for nano- to femtoliter ranges, and lack flexibility in printing on planar or curved surfaces with desired size and shape control.
Innovation Solution
A digital microfluidic system using electrowetting-on-dielectric actuation to move parent droplets over hydrophilic-in-hydrophobic micropatches, allowing for the efficient creation of arrays of nano- to femtoliter droplets by dividing parent droplets into smaller droplets, enabling high-throughput, flexible, and cost-effective printing on various surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional methods are used to print small liquid volumes, then minimum volume dispensing is achieved, but throughput is limited and the process becomes time-consuming
Solution Approach 1:
The parent droplet is segmented into multiple smaller daughter droplets by passing it over an array of hydrophilic micropatches. This segmentation enables simultaneous printing of multiple droplets in parallel, dramatically increasing throughput while reducing the time required compared to conventional sequential dispensing methods.
Solution Approach 2:
The system uses the surface tension and wettability properties of the hydrophilic micropatches to automatically divide and deposit droplets without requiring complex dispensing mechanisms. The parent droplet self-divides as it contacts the hydrophilic regions, enabling high-throughput printing with minimal mechanical intervention and reduced processing time.
2Productivity
If conventional printing methods are used, then minimum volume dispensing is achieved, but the process becomes expensive
Solution Approach 1:
The hydrophilic-in-hydrophobic micropatterned surface automatically performs the droplet division and deposition function without requiring expensive precision dispensing equipment. This self-service mechanism enables cost-effective printing of nano- to femtoliter volumes by utilizing surface tension and wettability differences rather than complex mechanical or electrostatic systems.
3Adaptability or versatility
If conventional methods are used for printing, then minimum volume dispensing is achieved, but flexibility in printing on various surfaces is limited
Solution Approach 1:
The surface is patterned with alternating hydrophilic and hydrophobic regions at the micro-scale. The hydrophilic micropatches have specific wettability properties that attract and retain droplets, while the hydrophobic regions repel them. This local variation in surface quality enables flexible printing on diverse substrates while maintaining precise control over droplet size, shape, and position through the geometric parameters of the micropatches.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables rapid, semi-automatic, and high-throughput printing of nano- to femtoliter arrays with precise control over droplet size and shape, facilitating applications such as aptamer selection and crystal deposition, while preventing evaporation and improving sensitivity in bio-assays.
Implementation Method 1
A digital microfluidic system using electrowetting-on-dielectric actuation to move parent droplets over hydrophilic-in-hydrophobic micropatches
Implementation Method 2
moving parent droplets over hydrophilic-in-hydrophobic micropatches, allowing for the efficient creation of arrays of nano- to femtoliter droplets by dividing parent droplets into smaller droplets
Data Source
AI summary
A miniaturized, automated method for controlled printing of large arrays of nano- to femtoliter droplets by actively transporting mother droplets over hydrophilic-in-hydrophobic (“HIH”) micropatches. The technology uses single or double-plate devices where mother droplets can be actuated and HIH micropatches on one or both plates of the device where the droplets are printed. Due to the selective wettability of the hydrophilic micropatches in a hydrophobic matrix, large nano- to femtoliter droplet arrays are created when mother droplets are transported over the arrays. The parent droplets are moved by various droplet actuation principles. Also, a method using two plates placed one top another while being separated by a spacer. One plate is dedicated to confirming and guiding parent droplets by using hydrophilic patches in a hydrophobic matrix, while the other plate contains HIH arrays for printing of the droplets. When the parent droplet guidance plate is rotated over the plate dedicated to printing of nano- to femtoliter droplets, the droplets are dispensed inside the HIH array utilizing their selective wettability. The methods allow the parent droplets to move over the HIH arrays many times, providing advantages for performing bio-assays or miniaturized materials synthesis in nano- to femtoliter sized droplets. With controlled evaporation of the dispensed droplets of solution, large arrays of printed material can be generated in seconds. The methods provide a nano- to femtoliter droplet printing technique for a wide variety of applications, e.g., protein- or cell-based bio-assays or printing of crystalline structures, suspensions of nanoparticles or microelectronic components.