High-Frequency AC Electrospray for Micron-Sized Drop Control
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Solution Overview
Problem
Current electrospray technologies primarily utilize direct current (DC) fields, which limit the generation of micron-sized drops and have not effectively explored the potential of high-frequency alternating current (AC) fields above 10 kHz for producing liquid aerosol drops, microspheres, and fibers.
Innovation Solution
An electrospray device employing micro-needles and conducting elements with a high-frequency AC electric field above 10 kHz to induce the ejection of micron-sized drops, microspheres, and fibers, utilizing biodegradable materials for encapsulation and synthesis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If direct current (DC) electric field is used for electrospray, then a steady continuous beam of charged droplets can be generated, but the drop size control and power efficiency are limited
Solution Approach 1:
The patent applies periodic AC electric fields at frequencies above 10 kHz to replace continuous DC fields. This periodic action creates time-varying Maxwell stresses that efficiently eject droplets at specific phases of the AC cycle, improving power efficiency by eliminating continuous energy consumption while achieving precise drop size control through frequency modulation.
Solution Approach 2:
The patent changes the fundamental parameter of electric field type from DC to high-frequency AC (>10 kHz). This parameter change enables new mechanisms for droplet ejection where the alternating field creates dynamic Maxwell stresses that can be tuned by frequency and amplitude, providing superior control over droplet size and significantly improving power efficiency compared to continuous DC operation.
2Use of energy by moving object
If high-frequency AC electric field above 10 kHz is used, then power efficiency and drop size control are improved, but the net Maxwell stress was expected to vanish making drop ejection impossible
Solution Approach 1:
The patent exploits periodic action by applying AC fields at frequencies above 10 kHz. The periodic nature of the field creates time-varying Maxwell stresses that, while averaging to zero over complete cycles, generate effective ejection forces during specific phases of the oscillation. This resolves the apparent contradiction by showing that periodic application of stress can achieve cumulative ejection effects.
Solution Approach 2:
The patent transitions from static DC fields to dynamic AC fields, utilizing the time-varying nature of the electric field. The dynamic application of Maxwell stresses at high frequency creates inertial effects and resonant phenomena that enable droplet ejection despite the zero time-averaged stress, converting the apparent weakness (vanishing net stress) into a mechanism for controlled drop generation.
3Productivity
If DC electrospray is used to produce sub-micron charged droplets, then a continuous beam can be achieved, but the application versatility for microspheres and fibers is limited
Solution Approach 1:
The patent achieves universality by demonstrating that high-frequency AC electrospray can produce multiple types of structures (droplets, microspheres, and fibers) from the same basic apparatus. The versatility is enabled by tuning AC field parameters (frequency, amplitude, waveform) and liquid flow conditions, allowing a single system to perform multiple functions that previously required different DC-based setups.
Solution Approach 2:
The patent utilizes parameter changes in the AC electric field (frequency >10 kHz, amplitude, waveform shape) to control the morphology of ejected material. By varying these parameters, the system can transition between producing droplets, microspheres, and fibers, thereby achieving broad application versatility including drug delivery, microencapsulation, and tissue engineering from a single platform.
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
The device generates distinct micron-sized electro-neutral drops and fibers, expanding application areas by offering improved drop size, power efficiency, and potential for miniaturization, with advantages in drug delivery, microencapsulation, and tissue engineering.
Implementation Method 1
introducing an alternating current electric field with a frequency greater than approximately 10 kHz across the one or more micro-needles and the one or more conducting elements to induce the ejection of liquid aerosol drops
Implementation Method 2
The Taylor cone is formed due to a static balance between the azimuthal capillary stress and the Maxwell normal stress exerted by the predominantly tangential and singular electric field in the liquid
Implementation Method 3
surface ions from the bulk electrolyte are transported and concentrated at the tip to drive a Rayleigh fission process
Implementation Method 4
The Taylor cone is formed due to a static balance between the azimuthal capillary stress and the Maxwell normal stress
Data Source
AI summary
The present invention provides an electrospray device using a high frequency alternating current (AC) above 10 kHz to generate fine micron sized drops. The apparatus generally functions by applying a high frequency alternating current electric field across one or more micro-needles and one or more conducting elements. The present invention may be used to generate aerosol drops for respiratory drug delivery or as a microencapsulation technique for the encapsulation of drugs, DNA, protein, osteogenic or dermatological growth factors, bacteria, viruses, immobilized enzyme receptors and fluorescent particles for controlled release drug delivery, tissue or bone engineering, clinical or environmental field testing and as biosensors for clinical or drug monitoring. In addition, the present invention may be used to synthesize biodegradable fibers as bioscaffolds for tissue engineering, surgical sutures or medical gauze that enhance blood coagulation, and further may be encapsulated by other agents.