Piezocomposite Ultrasonic Array for Precise Wearable Haptics
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Solution Overview
Problem
Current haptic technologies are bulky, require physical anchoring, and struggle with spatially imprecise stimulation, making them unsuitable for small-scale, lightweight, and wearable applications.
Innovation Solution
An ultrasonic haptic device using a piezocomposite phased array transducer that focuses ultrasound energy at or below the skin's surface, utilizing a piezoelectric transducer composed of PZT pillars with a matching layer and phased array focusing to deliver a spatially precise stimulus without physical anchoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If mechanical actuators are used for tactile stimulation, then force can be imparted to the skin, but the devices become bulky and require physical anchoring
Solution Approach 1:
The patent replaces mechanical actuators with ultrasonic transducers that generate acoustic radiation pressure. Instead of using mechanical motors and linkages to impart force, the system uses ultrasonic waves to create acoustic radiation pressure on the skin surface, eliminating the need for bulky mechanical components and physical anchoring structures.
Solution Approach 2:
The patent changes the operating parameters by using ultrasonic frequencies (typically 20-100 kHz) instead of mechanical actuation frequencies. This parameter change allows the system to generate sufficient tactile force through acoustic radiation pressure while using much smaller, lighter transducer elements that can be worn without physical anchoring.
2Volume of moving object
If ultrasonic transducers are used for tactile stimulation, then device size can be reduced, but power consumption increases significantly
Solution Approach 1:
The patent applies partial action by using a small array of ultrasonic transducers (e.g., 4x4 grid) rather than large arrays. Each transducer element is small (e.g., 10x10 mm) and operates at high frequency, achieving sufficient tactile stimulation through coordinated activation of only a partial array, thereby reducing overall power consumption while maintaining effective device size.
Solution Approach 2:
The patent uses periodic action by modulating the ultrasonic transducers at tactile frequencies (e.g., 1-50 Hz envelope modulation) rather than continuous high-power operation. The ultrasonic carrier wave is amplitude-modulated or pulse-width-modulated at lower frequencies that correspond to perceived tactile sensations, reducing average power consumption while maintaining effective stimulation.
3Measurement precision
If ultrasonic waves are focused at a point in space, then tactile sensation can be delivered, but the device becomes large and requires high power
Solution Approach 1:
The patent segments the ultrasonic array into multiple independently controllable elements arranged in a grid pattern. Each element can be individually activated and phased to contribute to the focal point, allowing the system to achieve precise spatial localization of tactile sensation while distributing the acoustic energy across many small elements rather than requiring a single large transducer.
Solution Approach 2:
The patent transitions from three-dimensional acoustic focusing (used in mid-air haptic devices) to two-dimensional surface focusing by placing ultrasonic transducers directly on or near the skin surface. This dimensional change allows the focal point to be achieved within the skin depth rather than in free space, reducing the required device area and power while maintaining spatial precision.
4Volume of moving object
If individual actuators are made small for wearable applications, then device can be worn on fingertip, but force generation becomes insufficient
Solution Approach 1:
The patent merges multiple small ultrasonic transducer elements into a coordinated array that works together to generate sufficient tactile force. While individual elements remain small and wearable, the combined acoustic radiation pressure from multiple elements (e.g., 16 or more elements working in unison) produces enough force to provide meaningful tactile feedback on the fingertip.
Solution Approach 2:
The patent uses composite structures combining ultrasonic transducer elements with acoustic matching layers and vibration isolation materials. The transducers are mounted on a flexible substrate with acoustic coupling agents and vibration isolation layers, creating a composite structure that efficiently transfers ultrasonic energy to the skin while accommodating the small form factor and providing sufficient tactile force.
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 is scalable, lightweight, and delivers precise tactile sensations, overcoming the limitations of previous technologies by reducing size and power consumption while maintaining effective haptic rendering.
Implementation Method 1
an ultrasonic haptic device that focuses ultrasound energy at or below the skin's surface using a piezocomposite phased array transducer
Implementation Method 2
energy is transferred from the impinging wave to the surface of the skin through acoustic radiation force, delivering a tactile sensation to the user
Implementation Method 3
a piezocomposite phased array transducer that focuses ultrasound energy
Data Source
AI summary
A wearable, low power, compact ultrasonic haptic device that focuses ultrasound at or below the skin's surface using a piezocomposite transducer consisting multiple arrayed acoustic pixels, each acoustic pixel comprising an array of piezocomposite pillars separated by an epoxy and topped by a metal electrode. The high efficiency of the piezocomposite transducer facilitates sufficient production of ultrasonic energy directed at a focal point at or below the surface the skin to stimulate a tactile sensation.