Dynamic Non-Wettable Surface for Nanoliter Droplet Manipulation
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Solution Overview
Problem
Existing methods for manipulating tiny liquid droplets face challenges in achieving precise and loss-free transfer due to high surface tension and contradictory requirements for liquid/solid adhesion, particularly when dealing with droplets of microliter and nanoliter sizes, and are not applicable for real-time manipulation or handling of oil droplets.
Innovation Solution
A dynamic patterned non-wettable surface with microstructures of varying surface energy is introduced, allowing for reversible adhesion switching by forming capillary bridges that enable firm pinning and effortless release of droplets, using micro-fibers with wettability contrast that can be extended or retracted to modify surface chemistry in-situ.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high liquid/solid adhesion is provided to overcome surface tension and balance gravitational force for reliable droplet capture, then droplet manipulation reliability is improved, but droplet release becomes difficult because the same high adhesion prevents dispersion on target surface
Solution Approach 1:
The surface adhesion property is made dynamic and switchable between high adhesion state (for droplet capture and manipulation) and low adhesion state (for droplet release). This is achieved through a non-wettable surface with microstructures that can reversibly change their wetting state, allowing the same surface to provide both strong holding force and easy release functionality.
Solution Approach 2:
The liquid/solid adhesion parameter is changed by modifying the surface energy state of the non-wettable surface. By controlling the wetting state of the microstructures on the surface, the adhesion force can be tuned between high and low values, enabling reliable capture when needed and easy release when needed.
2Measurement precision
If conventional measurement tools are used for tiny droplets, then volume measurement is required, but significant liquid residue remains on the measurement tools after manipulation leading to loss
Solution Approach 1:
The measurement function is extracted from conventional measurement tools and integrated directly into the non-wettable surface system. The surface itself can capture and hold droplets for volume determination without requiring separate measurement instruments, and the non-wettable property ensures minimal residue loss during transfer.
Solution Approach 2:
The non-wettable surface performs both manipulation and measurement functions for tiny droplets without requiring external measurement tools. The surface's inherent non-wettable properties enable it to self-regulate droplet adhesion and minimize residue, making the system self-sufficient for precise droplet handling.
3Quantity of substance
If techniques like pyroelectrodynamic shooting or focused acoustics ejection are used to prepare nanoliter droplets, then droplet aliquoting capability is improved, but droplet manipulation and deposition on liquid-repellent surfaces becomes unreliable due to low liquid/solid adhesion
Solution Approach 1:
The non-wettable surface incorporates microstructures with specific local properties that create regions of controlled adhesion. These microstructures can be designed to provide appropriate liquid/solid adhesion locally, enabling reliable deposition and manipulation of nanoliter droplets on otherwise liquid-repellent surfaces.
4Adaptability or versatility
If smart non-wettable surfaces with responsive liquid adhesion are used, then adhesion switching capability is improved, but responding time is long and switching adhesion is ex-situ requiring different droplets for testing
Solution Approach 1:
The non-wettable surface is pre-configured with microstructures that enable rapid adhesion switching. The surface chemistry and microstructure geometry are designed in advance to facilitate quick transitions between wetting states, eliminating the need for lengthy response times and enabling real-time droplet manipulation.
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
This method allows for precise, rapid, and nearly loss-free manipulation of tiny droplets, including both water and oil, down to nanoliter volumes, with tunable adhesion and capacity, suitable for real-time applications in micro-reactors and multi-component synthesis, and is durable with good chemical resistance.
Implementation Method 1
large adhesion can be generated by a capillary bridge formed between the liquid droplet and the micro-wettable domain
Implementation Method 2
it is essential that the manipulator provide high liquid/solid adhesion so as to overcome the substantial surface tension of the droplet
Implementation Method 3
Without capillary bridges, adhesion between the droplet and non-wettable surface is negligible due to the Cassie state of the droplet
Implementation Method 4
micro-fibers with wettability contrast that can be extended or retracted to modify surface chemistry in-situ
Data Source
AI summary
An apparatus and method are provided for rapid and precise manipulation and transfer of tiny liquid droplets. by dynamically introducing microstructures with relatively high surface energy to a non-wettable surface, which surface has in-situ switchable adhesion to liquid droplets. By penetrating microstructures on the background surface, the chemical property of the surface is locally modified. Capillary bridges will form between microstructures and liquid droplets which lead to high adhesive forces. When the microstructures are retracted, the capillary bridges either pinch-off or recede, which drastically reduces the adhesion. With proper chemical modification, the surface can either manipulate a liquid droplet in air or in an immiscible carrier liquid. Tiny droplets with volumes down to nanoliter scale can be prepared and dispensed by using the surface.