Ultrasonic-assisted liquid manipulation
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Solution Overview
Problem
Current hand-drying methods, such as forced air dryers, are often slow and loud, leading to increased usage of wasteful paper towels due to inefficiencies, and existing technologies for liquid manipulation lack effective, non-contact methods for speeding up the drying process without causing damage to skin.
Innovation Solution
A phased array of ultrasonic transducers is used to create arbitrary acoustic fields that focus ultrasound energy on the surface of the hand, utilizing nonlinear pressure fields to push liquid droplets off the skin and enhance evaporation through capillary wave-induced atomization, while avoiding direct contact and potential tissue damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-powered ultrasound is applied directly to the bulk of the hand, then drying speed increases, but tissue damage occurs through heating, mechanical stress, or cavitation
Solution Approach 1:
The patent divides the hand surface into multiple focal zones using a phased array of ultrasonic transducers. Each transducer focuses acoustic energy on a specific small area, and the focal zones are sequentially activated or overlaid in a scanning pattern. This segmentation prevents any single location from receiving excessive cumulative energy that would cause heating or cavitation damage, while collectively covering the entire hand surface for effective drying.
Solution Approach 2:
The patent implements dynamic scanning of the focal zones across the hand surface. The phased array electronically steers and moves the focal points in a predetermined pattern, ensuring that each location on the hand receives ultrasonic energy only temporarily before the focus moves to the next location. This dynamic approach distributes the total energy exposure over time and space, preventing localized overheating or mechanical damage while maintaining high drying efficiency.
2Object-affected harmful factors
If airborne ultrasound is used to manipulate liquids, then direct contact is avoided and skin safety is improved, but coupling efficiency decreases
Solution Approach 1:
The patent employs parametric acoustic arrays that generate ultrasonic frequencies (typically 20-100 kHz) which are then modulated to produce audible difference frequencies (20-20 kHz). This parametric conversion allows the system to use high-frequency airborne ultrasound for effective liquid manipulation while the lower difference frequencies provide efficient coupling to the skin and liquid surface. The parameter change from ultrasonic to audible frequencies enables both skin-safe airborne operation and effective energy transfer.
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 efficiently speeds up the drying process by using airborne ultrasound to manipulate liquids, reducing drying time and energy consumption, while minimizing mechanical stress and heating on the skin, thereby increasing hand dryer usage and reducing maintenance costs.
Implementation Method 1
Ultrasound signals may be used to manipulate liquids by interacting with the resulting acoustic pressure field
Implementation Method 2
utilizing nonlinear pressure fields to push liquid droplets off the skin and enhance evaporation through capillary wave-induced atomization
Implementation Method 3
While some signaling may penetrate into the hand, most of the energy (99.9%) is reflected
Data Source
AI summary
A phased array of ultrasonic transducers may create arbitrary fields that can be utilized to manipulate fluids. This includes the translation of drops on smooth surfaces as well speeding the evaporation of fluids on wetted hands. Proposed herein is the use airborne ultrasound focused to the surface of the hand. The risk is that coupling directly into the bulk of the hand may cause damage to the cellular material through heating, mechanical stress, or cavitation. Using a phased array, the focus may be moved around, thus preventing acoustic energy from lingering too long on one particular position of the hand. While some signaling may penetrate into the hand, most of the energy (99.9%) is reflected. Also disclosed are methods to couple just to the wetted surface of the hand.