Stretchable electronics

Size: px

Start display at page:

Download "Stretchable electronics"

Lillian Osborne
5 years ago
Views:

2 Stretchable electronics Constraints and possibilities for direct printing on thermoplastic polyurethanes From flexible printed electronics to stretchable Eric Rubingh, Corné Rentrop, Piet Bouten

< 3 Holst Centre in a nutshell Who we are Open

imec (1300 fte, BE) and TNO (4500 fte, NL) Located

Netherlands Own staff 310 researchers What we do

wireless autonomous microsystems In close

the value chain Holst Centre R2R lab Thin Film clean

Equipment Engineering Life Sciences Materials

3 < 3 Holst Centre in a nutshell Who we are Open innovation research institute Founded in 2005 by imec (1300 fte, BE) and TNO (4500 fte, NL) Located at the High Tech Campus in Eindhoven, The Netherlands Own staff 310 researchers What we do Developing technologies for printed electronics and wireless autonomous microsystems In close collaboration with leading industrial partners along the value chain Holst Centre R2R lab Thin Film clean room Electronic measurement OLED Device Processing Equipment Engineering Life Sciences Materials Analysis Photonics cleanroom EMC lab Electronic Prototyping Reliability lab Holst Centre Offices

4 < 4 Holst Centre: Technologies targeted Hybrid printed electronics such as wearable health monitoring and pressure sensor systems Low power sensor systems for monitoring food, air, water quality Low-cost solar cells, CIGS, Thin film, Perovskites, OPV Flexible OLED lighting and displays

< 5 Holst Centre: Technologies targeted Hybrid printed electronics such as wearable health monitoring and pressure sensor systems Low power sensor systems

5 < 5 Holst Centre: Technologies targeted Hybrid printed electronics such as wearable health monitoring and pressure sensor systems Low power sensor systems for monitoring food, air, water quality Combine into wearables Low-cost solar cells, CIGS, Thin film, Perovskites, OPV Flexible OLED lighting and displays

6 < 6 An explosion of wearable tech

7 < 7 Clothing as wearable tech platform Smart clothing We all wear it and it covers most of our body Monitor vital signs, location, Electronics should be conformable, stretchable, washable,

8 < 8 Wearable electronics, from flexible to stretchable Version 1 Lamination of printed flexible structures Printing of functional structures on thin films Assembly of components Textile lamination with TPU Using standard printed electronics materials Version 2 Lamination of printed stretchable structures Printing functional structures with meanders on films Assembly of components Laser structuring of meanders Textile lamination on TPU Using standard printed electronics materials Version 3 Direct printed stretchable structures Printing of functional structures on TPU Assembly of components Textile lamination Using special stretchable materials

9 < 9 Wearable electronics, from flexible to stretchable Version 1 Lamination of printed flexible structures Printing of functional structures on thin films Assembly of components Textile lamination with TPU Using standard printed electronics materials Version 2 Lamination of printed stretchable structures Printing functional structures with meanders on films Assembly of components Laser structuring of meanders Textile lamination on TPU Using standard printed electronics materials Version 3 Direct printed stretchable structures Printing of functional structures on TPU Assembly of components Textile lamination Using special stretchable materials

10 Version 1: Lamination of printed flexible structures Start from thin plastic films Holst Centre < 10 Typical polymers: polyesters (PEN/PET), polycarbonate (PC), polystyrene (PS) Typical thicknesses: um

11 Version 1: Lamination of printed flexible structures Printing of complex multi-layer structures Holst Centre < 11 Physical activity monitoring patch Multi-layer circuit patterns Done by printing alternating layers of conductive and isolating inks Printing up to 5 circuit layers demonstrated

Version 1: Lamination of printed flexible structures Component integration Holst Centre < 12 WiFi tag on film, 5 stacked circuit layers Component

12 Version 1: Lamination of printed flexible structures Component integration Holst Centre < 12 WiFi tag on film, 5 stacked circuit layers Component integration Several technologies available for reliable integration of components on PE foils Based on ACA, ICA or special soldering technologies

13 Smart textiles Accelerometer Heart rate monitoring Location Not Stretchable Version 1: Lamination of printed flexible structures Textile lamination with TPU Holst Centre 13

14 < 14 Wearable electronics, from flexible to stretchable Version 1 Lamination of printed flexible structures Printing of functional structures on thin films Assembly of components Textile lamination with TPU Using standard printed electronics materials Version 2 Lamination of printed stretchable structures Printing functional structures with meanders on films Assembly of components Laser structuring of meanders Textile lamination on TPU Using standard printed electronics materials Version 3 Direct printed stretchable structures Printing of functional structures on TPU Assembly of components Textile lamination Using special stretchable materials

stretchable through opening/out-of-plane bending Less strain on printed

15 < 15 Version 2: Meander approach for stretchable PE Meander approach Make local spring structures ( meanders ) in the printed electronics film Structures are stretchable through opening/out-of-plane bending Less strain on printed structures/lines The result A stretchable device made from a flexible printed electronics film

16 < 16 Version 2: Meander approach for stretchable PE start from polyester film print electronic structures assemble components laser structure meander Encapsulate in TPU film Washable Laminate on fabric TPU PEN TPU Out of plane deformation of meanders allows stretchability Encapsulation into polyurethane enables washability

17 < 17 Version 2: Meander approach for stretchable PE

18 < 18 Version 2: Meander approach for stretchable PE

Version 2: Meander approach for stretchable PE Holst Centre < 19 or PCB s that are stretchable Reliability of meander approach Reliability of meander approach + component integration Flex

19 Version 2: Meander approach for stretchable PE Holst Centre < 19 or PCB s that are stretchable Reliability of meander approach Reliability of meander approach + component integration Flex testing 2 mm radius) and stretch testing 20% strain) Washability: 25 washing cycles at 50 o C successfully completed Main failure cause: mechanical damage (drum rotation)

20 Version 2: Meander approach for stretchable PE Health Patch Holst Centre < 20 Wearables: Health patch Printed electrical sensors Enables ECG, EMG and breathing analysis Worn as a patch on the body for several days Using stretch technologies for improved comfort

21 Version 2: Meander approach for stretchable PE Smart garment Holst Centre < 21 Smart Garment: Printed electrical sensors Enables ECG, EMG etc. Lamination into shirt using TPU Using stretch technologies for reduction of motion artifacts

22 < 22 Wearable electronics, from flexible to stretchable Version 1 Lamination of printed flexible structures Printing of functional structures on thin films Assembly of components Textile lamination with TPU Using standard printed electronics materials Version 2 Lamination of printed stretchable structures Printing functional structures with meanders on films Assembly of components Laser structuring of meanders Textile lamination on TPU Using standard printed electronics materials Version 3 Direct printed stretchable structures Printing of functional structures on TPU Assembly of components Textile lamination Using special stretchable materials

23 Version 3: Direct printing of electronics on TPU < 23 Thermoplastic polyurethane: Foldable and stretchable One step lamination onto textile TPU used extensively in garments and graphical printing industry

< 24 Thermoplastic polyurethanes (TPU) Stretchable Robust Solvent resistant Washable Adjustable mechanical properties Hardness, young s module,

24 < 24 Thermoplastic polyurethanes (TPU) Stretchable Robust Solvent resistant Washable Adjustable mechanical properties Hardness, young s module, stress /strain characteristics But also: Creep /Hysteresis Thermal shrinkage Time dependency Strain hardening Residual strain *Desmophan - Covestro

< 25 Mechanical testing of TPU s and printed structures Test Set-up Instron Tensile Tester Influence stress-strain on resistance Monitor Load, displacement and resistance Evaluate TPU substrates

25 < 25 Mechanical testing of TPU s and printed structures Test Set-up Instron Tensile Tester Influence stress-strain on resistance Monitor Load, displacement and resistance Evaluate TPU substrates Different types of TPU Polyester or polyether based Different thicknesses and E-moduli Characteristics Compatibility with printing process Thermal shrinkage, creep, residual strain Evaluate stretchable inks and pastes Types of materials Conductive pastes, dielectrics, sensor materials, adhesives Characteristics Stretchability, adhesion, cohesion Conductivity under/after strain Component assembly and die shear testing

< 26 Mechanical testing of TPU s and printed structures Typical test regimes Linear strain Stretching until failure Report absolute and relative resistance (ΔR/R [%]) Progressive strain Deformation:

26 < 26 Mechanical testing of TPU s and printed structures Typical test regimes Linear strain Stretching until failure Report absolute and relative resistance (ΔR/R [%]) Progressive strain Deformation: 2% - 5% - 10% - 15% - 20% Hysteresis effect Report residual strain Report absolute and relative resistance (ΔR/R [%]) Cyclic strain tests Repeated deformation (20% - relaxation) 100 times and up Report maximum and minimum stress/resistance

27 < 27 Mechanical testing: Linear strain Stress/resistance under line strain Resistance is increasing exponentially Conductivity in line fully lost at 70% strain Workable resistance until 30% strain End Start

28 < 28 Mechanical testing: Progressive strain Progressive strain curves as a function of used TPU Residual strain varies per type But residual strain is not the only important parameter! Residual strain 5% Residual strain 2.1% Residual strain 1.3%

ΔR/R [%] Stress [MPa] Holst Centre < 29 Mechanical testing: Progressive strain Influence

20% strain: 275% Resistance in relaxed state after testing important ΔR/R after progressive

particles in structure No visible defects/cracks in line Visual inspection after test Bright

29 ΔR/R [%] Stress [MPa] Holst Centre < 29 Mechanical testing: Progressive strain Influence progressive strain on line resistance Resistance increases with increasing strain Max ΔR/R at 20% strain: 275% Resistance in relaxed state after testing important ΔR/R after progressive strain test: 100% Partly caused by residual strain in TPU Partly caused by reorientation of particles in structure No visible defects/cracks in line Visual inspection after test Bright field: 50x Bright field: 500x Dark field: 200x Strain [%] 0

< 30 Mechanical testing: Progressive strain Stress-strain-resistance

pastes tested Paste A: Time dependency observed in relaxation curve

stretchability with increased stiffness Paste C: High conductivity, no

paste characteristics Printability Adhesion and cohesion

30 < 30 Mechanical testing: Progressive strain Stress-strain-resistance curves as a function of used silver paste Several commercial silver pastes tested Paste A: Time dependency observed in relaxation curve Paste A: Time dependency resolved by over-coating Paste B: High stretchability with increased stiffness Paste C: High conductivity, no stretchability Paste D: High conductivity, high residual strain Silver paste characteristics Printability Adhesion and cohesion Stretchability Conductivity Initial Max strain After strain Component assembly Die shear strength

31 < 31 Mechanical testing: Progressive strain Stress-strain-resistance curves as a function TPU substrate Using silver paste B TPU with high residual strain TPU with low residual strain Observations Resistance curves on both TPU substrates very similar Minimal resistance for low residual strain TPU slightly lower Maximal resistance at strain for high residual strain TPU lower

< 32 Mechanical testing: Cyclic strain test Stress-strain-resistance curves as a function of cycles Using silver paste B Resistance at min and max strain increases After ~70 cycles resistance @

32 < 32 Mechanical testing: Cyclic strain test Stress-strain-resistance curves as a function of cycles Using silver paste B Resistance at min and max strain increases After ~70 cycles min strain stabilizes After ~150 cycles max strain stabilizes Stress 20% strain (high) Stress 7% strain (low) Resistance 20% strain Resistance 7% strain

33 Demonstrator direct printing on TPU Holst Centre < 33 Health patch on TPU Monitor vital signs 3 layer prints Sufficient registration Stretchable

34 < 34 Demonstrator direct printing on TPU Flex smell platform Sensor platform on TPU Temperature and capacitive sensors NFC enabled, app assisted

35 < 35 Other applications Light in clothing Designer jacket Display in clothing Solar shirt Pressure sensor shoe-inlay

36 < 36 Conclusions and work in progress Large variety of TPU substrates available Stress-strain behavior and residual strain important Several other parameters also important Thermal stability, printability, lamination quality and washability Cyclic tests typically reveal stability after ~70 cycles Change of TPU changes stress/strain behavior and performance of pastes Large difference between stretchable pastes Conductivity Stretchability Compatibility with TPU Possible to create functional demonstrators Work in progress Improved component integration in stretchable electronics Washability of devices with larger components Other substrate types like Silicone

37 < 37 Thank you

Manipulation and control of spatial ALD layers for flexible devices. Aimcal Memphis 2016; Edward Clerkx

Manipulation and control of spatial ALD layers for flexible devices Meyer Burger Netherlands Equipment manufacturer Functional inkjet printing Based in Eindhoven, the Netherlands Part of world-wide Meyer