2012 10-15-sirris µprinting-day-zoellmer

© Fraunhofer IFAMContact: Dr. Volker Zöllmer, Tel.: +49 [email protected]

Mikro Printing Day at Sirris, 15th October 2012

Volker Zöllmer(1), Edit Pál(2,3), Marcus Maiwald(1), Cindy Behrens(1), Christian Werner(1), Dirk Godlinski(1), Ingo Wirth(1), Matthias Busse(1,2)

(1) Fraunhofer IFAM, Funktionsstrukturen, Bremen, Germany

(2) University of Bremen, Faculty of Production Engineering, Near Net Shape Technology, Bremen, Germany

Functional materials for printed sensor structures

© Fraunhofer IFAMContact: Dr. Volker Zöllmer, Tel.: +49 [email protected]

Functional materials for printed sensor structures

1. Introduction Fraunhofer-Society and Fraunhofer IFAM

2. Motivation: Functional printing at Fraunhofer IFAM

3. Processes and materials

4. Examples: thermocouples, strain gauges, gas sensors, bio printing

© Fraunhofer© Fraunhofer IFAMContact: Dr. Volker Zöllmer, Tel.: +49 [email protected]

1. IntroductionFraunhofer-Institute for Manufacturing Technology and Advanced Materials - IFAM

Departments Shaping and Functional

Materials Adhesive Bonding Technology

and Surfaces

Locations in Bremen and Dresden

Project groups in Oldenburg and Stade

535 Employees

Overall budget in 2011: 40 Mio. €


Photovoltaic

Displays

Lighting (LED & OLED)

Electronics (RFIDs, Storage, Battery…)

Integrated Smart Systems (Sensors, Textiles,…)

(© OE-A Roadmap for Organic and Printed Electronics, 4th Ed. 2011)

2. Printed Sensor StructuresTechnology platform at Fraunhofer IFAM


Motivation:

Functionalization of surfaces, parts and components by use of additive manufacturing

Technologies:

Screen printing

Dispensing / ventile printing

Ink-Jet-Printing (Continuous, Drop-On-Demand)

Aerosol JetⓇ

Benefit:

Direct application of miniaturized structures

„Customized“ structures for electronics, sensors, medical applications etc.



Material screening: metals, alloys, polymers, ceramics, bio-materials, …

Ink / paste formulation

Design & Layout

Printing processes: InkJet, Aerosol Jet, Screen printing, dispensing …

Thermal activation: UV, Laser, Oven, …

Characterization: Mechanical, optical, electrical, …



■ Maskless, non-contact, digital, additive

■ Min. structures of ca. 25 μm

■ Printheads with 16 to 128 nozzles

3. Printed Sensor Structures InkJet printing


1. Functional ink is placed in the atomiser, gas flow creates an aerosol 2. Aerosol droplets ca.1-5μm, larger droplets return to ink (gravity effect)3. The aerosol is carried to the deposition head, excess gas removed4. The aerosol is focussed inside the nozzle by a secondary gas flow (sheath gas)

(© Neotechservices)

1

2

3 4

3. Printed Sensor StructuresAerosol Jet®


Flexible module for customized functionalization

3. Printed Sensor Structures3-d-printing

Printing on 3-d-components


Flexible module for customized functionalization


Printing on 3-d-components

Foot pedal of a bicycle functionalized with aerosol printed strain gauges


IFAM development of printable inks:

Ag, Au, Pt, Cu, alloys (e.g. CuNiMn, NiCr, …)

Isolators: Ceramics (TiO2, SiO2, …), Polymers

Dielectric Materials

Biological materials: Enzymes, Proteins, DNA, Bio-ceramics…



Interactions between (nano-) particles and ink solvents(© www.sciencedirect.com)

3. Printed Sensor StructuresMaterials development


Ink optimization:

Investigation of sedimentation stabilities

Surface tensions characterization

Contact angle characterization

Viscosity characterization

Particle surface modification

Particle size distributions

Particle morphology (SEM,TEM,...)

Material/phase analysis (EDX, XRD, ...)

Surface characterization (BET, XPS, ...)



CuNiMn is an appropriate material for printed strain gauges

Cu0.55Ni0.44Mn0.01 (constantan)

low temperature coefficienct of resistance (TCR)

mechanical properties

Ag CuNiMn

TCR: 3.8 x 10-3 K-1 TCR: 0.01 x 10-3 K-1

Commercially available fromdifferent suppliers

not commercially available



Different physical and chemical approaches:

VERL (Vacuum Evaporation on Running Liquids)

Peparation of Cu55Ni45Mn1 – alloy inks



Sintering

Remove organic content

Enhance electrical conductivity

Optimize mechanical properties

Oven sintering under H2, N2, Argon, … (up to 1700 °C) Substrate limitations, relatively long processing time)

Laser Sintering

Microwave Sintering

UV Curing

Sintering under pressure

Electrical sintering

100 nm

3. Printed Sensor StructuresSintering technology


Electrical conductivity of CuNi structures:

Dr. Edit Pál, et al. ISIS Scientific Centre, University of Bremen

TEM: CuNiChemical process

TEM: CuNiPhysical process

3. Printed Sensor StructuresDevelopment of printable alloy inks


Strain gauge printed on steel substrate

Wheatstone full bridge

Resistance Rx = additional resistance for bridge balancing

Measuring setup parameters:

Room temperature continuous strain (1000 N tensile

stress, 500 N compressive stress testing frequency 25 Hz 105 cycles

5 mm5 mm

4. Printed Sensor StructuresPrinted strain gauges for SHM - applications

AlR

llk

RR

R

F


CuNiMn - strain gauges printed on ceramic substrates



Dynamic test (tensile stress: 1000 N, compressive stress: 500 N, 25 Hz, 7675 cycles)

Reproducible signals of Ag-strain gauges

No significant influence of porous structure



Thermocouple: Seebeck Effect

TNU materialmaterial )( 21

4. Printed Sensor StructuresPrinted thermocouples for SHM - applications


Printed thermocouple and heating structure

Heating structure

TNU materialmaterial )( 21

U

DT


Thermocouple

linear increase of thermocouple voltage in dependance of temperature difference between hot and cold junctions

Seebeck coefficient of printed thermocouple comparable with Seebeck coefficient of bulk material

printed thermocouple allows direct temperature measurements on surfaces and components


Thermocouple

linear increase of thermocouple voltage in dependance of temperature difference between hot and cold junctions

Seebeck coefficient of printed thermocouple comparable with Seebeck coefficient of bulk material

printed thermocouple allows direct temperature measurements on surfaces and components



4. Printed Sensor StructuresSensor structures for gas detection

Deposition of functionalized interdigital structures

Digital structures of noble metals

Customized functionalization to enhance sensitivity and selectivity



Deposition of functionalized interdigital structures

Use of e.g. metal oxides as gas sensitive functionalization

High specific surface

SnO2, ZnO, WO3


BSA - FITC

BSA - Rhodamin

BSA - Alexa Fluor 350

Printing of fluorescence marked BSA-Proteine materials



Functionalization of interdigital structures

High specific surface, high sensitivity

E.g.: Functionalization with enzymes



Printing of bio ceramics for cell growth management

Day 7

Day 1

4. Printed Bio CeramicsCell growth management


Printing of bio ceramics for cell growth management

4. Printed Bio CeramicsCell growth management


Functional materials for printed sensor structures- Summary

Functional printing as a flexible technology platform for sensor deposition and integration.

Printing processes, functional inks and thermal post treatment have to be considered

Printing technologies are feasible for e.g.

Strain sensor structures and thermocouples

Gas sensor structures and deposition of gas sensitive materials

Integration of sensor structures in composites

Printing of bio materials possible


Volker Zöllmer(1), Edit Pál(2,3), Marcus Maiwald(1), Cindy Behrens(1), Christian Werner(1), Dirk Godlinski(1), Ingo Wirth(1), Matthias Busse(1,2)

(1) Fraunhofer IFAM, Funktionsstrukturen, Bremen, Germany

(2) University of Bremen, Faculty of Production Engineering, Near Net Shape Technology, Bremen, Germany

Thank you for your attention!

Functional materials for printed sensor structures- Acknowledgments

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