Haptic Button With Shape Memory Alloy Actuator

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Solution Overview

Problem

Conventional haptic buttons in portable consumer electronics face challenges in providing a satisfying tactile response due to their low profile design, which limits their ability to move and generate effective haptic feedback, while also being difficult to make waterproof and dustproof.

Innovation Solution

The development of haptic button assemblies that incorporate a shape memory alloy (SMA) actuator wire coupled with an intermediate moveable element, allowing the button to move perpendicularly within a compact space, providing a localized and customizable haptic sensation, and featuring a sealing mechanism to ensure water and dustproofing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If a low profile button design is used to maximize display screen space, then the device thickness is reduced and display size is increased, but the button cannot move sufficiently to provide a satisfying tactile response

Engineering Contradiction:

Improvebutton travel distanceVSAvoidbutton assembly height

Core Design Contradiction:

Volume of moving objectVSLength of stationary object

Solution Approach 1:

The patent transforms the button's movement from a purely vertical dimension to include lateral movement through an intermediate moveable element. The button moves vertically while the intermediate element moves laterally, allowing sufficient tactile travel without increasing the overall assembly height, thus resolving the contradiction between button travel distance and assembly height.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The intermediate moveable element acts as a mediator between the button and the shape memory alloy actuator. It converts the vertical button movement into lateral movement, enabling the button to provide satisfying tactile feedback within a compact vertical space constraint.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If a low profile button design is used, then the device becomes more compact, but the button assembly becomes more difficult to waterproof and dustproof

Engineering Contradiction:

Improvewaterproof and dustproof capabilityVSAvoidbutton assembly height

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

The patent employs a flexible sealing membrane that conformally seals around the button and intermediate moveable element. This flexible film approach allows effective waterproof and dustproof sealing within a low profile configuration, resolving the contradiction between compactness and sealing reliability.

Inventive Principle:

Principle #30Flexible shells and thin films

3Force

If conventional actuators are used in a compact space, then the button assembly height is reduced, but the actuator cannot provide sufficient force for effective haptic feedback

Engineering Contradiction:

Improvehaptic feedback forceVSAvoidactuator height

Core Design Contradiction:

ForceVSLength of stationary object

Solution Approach 1:

The patent replaces conventional mechanical actuators (such as motors or solenoids) with a shape memory alloy actuator that utilizes thermal-mechanical coupling. This substitution enables sufficient haptic feedback force within a compact height by leveraging the high force density of SMA materials and their ability to generate significant force through thermal activation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The shape memory alloy actuator changes its physical state through temperature variation, transitioning between austenite and martensite phases. This parameter change allows the actuator to generate sufficient force for effective haptic feedback while maintaining a compact form factor, as the phase transition provides high force output without requiring large mechanical dimensions.

Inventive Principle:

Principle #35Parameter changes

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 solution enables haptic button assemblies with a low profile that can provide a satisfying tactile response, are more aesthetically pleasing with reduced visible gaps, and are easier to waterproof and dustproof, while allowing for customizable haptic feedback.

Implementation Method 1

at least one shape memory alloy (SMA) wire coupled to the at least one intermediate moveable element and arranged to, on contraction, move the intermediate moveable element in the plane

Methodology Applied

Scientific EffectShape memory alloy: Shape Memory Alloy

Data Source

PatentUS12254136B2Haptic button with SMA

Publication Date: 2025.03.18 CAMBRIDGE MECHATRONICS

AI summary

Broadly speaking, embodiments of the present techniques provide haptic button assemblies in which the haptic button has a low profile while still providing a satisfying tactile response or sensation to a user. Advantageously, the haptic button assemblies may have a profile that, for example, enables the assembly to be incorporated into the free space along an edge of a portable computing device. The haptic assemblies may, for example, be arranged to move the button perpendicularly with respect to the edge of the device.