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Shape Memory Alloy (SMA) The

Future Of HapticsDr Andrea Cantone – Head of New Products

CW Future Devices & Technology SIG event, Smart Devices of 2025, March 27th 2018

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CML overview

▪ Cambridge Mechatronics (CML) is a high technology design and engineering company based in Cambridge, UK

▪ 70 multidisciplinary staff from top global universities located in Cambridge (UK) and Greater China

▪ The company has protected its innovations with anextensive IP portfolio, including over 100 granted patents

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Introduction to SMA

▪ Shape Memory Alloy (SMA) is a unique material that contracts significantly when heated, creating large forces and motion

▪ CML is the first company in the world to precisely control the contraction of SMA wire

▪ This has resulted in a single-piece motor the size of a human hair that can be controlled to the accuracy of the wavelength of light

▪ CML has applied this technologyto actuators for a number ofhigh value applications

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Products in market

SMA ACTUATORS ARE PRODUCED UNDER LICENSE FROM CML BY GLOBAL MANUFACTURES

CML’s TECHNOLOGY IS ALREADY SHIPPING IN AUTOFOCUS AND OIS CAMERAS IN WEARABLES, SMARTPHONES AND DRONES

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ERM LRA Piezo EAP SMA

Type of

Sensation

Whole device

haptic feedback

Local

haptic feeling

Frequency

range90-200Hz 150-200Hz 150-300Hz 90-125Hz 0-250Hz

Response time 50ms 30ms <5ms <5ms <1ms

Approximate

size and format

11x4.5x4.5

mm

Bar

30x12x3 mm

Taptic

engine

3.5x3.5x42

mm

Matchstick

45x38x0.8

mm

Flat panel

15x4x0.95

mm

Energy/pulse 30mJ 15mJ 64mJ 120mJ 6mJ

Haptic technology comparison

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CML haptic technology benefits

1. Wide frequency range & very quick response time

2. Low power consumption and drive voltage

3. Small size

4. Simple, low cost design and manufacture

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▪ Users like to tailor settings to their personal preferences, such as apps, ringtones & wallpaper

▪ A mechanical button delivers a single waveform that may not be preferred by all consumers

▪ The SMA waveform can be selected, tuned and changed by the user creating a customisable experience

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Haptic Button Pulse A

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Haptic Button Pulse C

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Haptic Button Pulse B

Frequency range and response time (1/2)

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▪ An SMA haptic button can also give sequential pulses

▪ Below are two potential usage applications,– Delivering a pulse when skipping music tracks and a different pulse

to indicate the first or last track has been reached

– Delivering a pulse when changing audio volume level and a different pulse to indicate the maximum or minimum volume has been reached

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Track 5 Track 4 Track 3 Track 2

Track 1

Frequency range and response time (2/2)

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Low power consumption

▪ A typical feedback pulse (as shown) will have the following power consumption characteristic,– Voltage: 2.5V to 5.0V

– Energy: 6mJ

▪ Table of number of pulses for a full device battery

Device type Battery size % of battery used per 1K

presses

Smartphone 2000mAh 0.02%

Smartwatch 200mAh 0.2%

Wireless

earphones100mAh 0.4%

020406080

100120140160180

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m)

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Small size

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Increased design flexibility

▪ The lateral motion of SMA haptics allows the side buttons to be completely smooth to the handset casework which prevents buttons protruding from the side of the handset casework

▪ The small mechanical movement results in a minimal gap between the button and the casing, allowing greater design flexibility

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Simple, low cost design

▪ When activated, the SMA wire is heated and quickly contracts

▪ The SMA haptic actuator structure is similar to CML’s SMA smartphone optical image stabilisation (OIS) actuators already in mass production

▪ Similarly to SMA OIS actuators, the key components are SMA wire (<$0.10 per actuator) and a return spring

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Simple manufacture

▪ The component parts of the SMA haptic button can all be produced using standard manufacturing processes, such as plastic injection moulding and metal pressing

▪ Assembly is straightforward and can be fully automated if necessary

▪ SMA wire handling is the only non-standard assembly process, but similar to the SMA camera actuator process

▪ CML will support licensees with this equipment and process development, as it has done successfully with its smartphone camera actuator licensees

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Comparison summary

Actuator Type Advantages Disadvantages

ERM Low cost and simple

Strong at high frequencies

Easy to drive

Non local

Slow response time

High energy consumption

LRA Faster response time than ERM

High definition waveform

Non local

Single frequency

Difficult to drive

Piezo High definition

Fast response

High cost

High instantaneous power

Requires high drive voltage

EAP Large frequency range

Thin profile

High instantaneous power

High cost

Requires high drive voltage

SMA Large frequency range

Fast response time

Thin profile

Low power & low voltage

Low cost

Limited to short duration pulse