The document discusses developments in conductive inks for printed electronics. It summarizes a masterclass on the future of conductive printing that covered: 1) the current status and types of conductive inks, 2) a EU project called CLIP that developed low-cost silver and copper nanoparticle inks for various printing methods, and 3) state-of-the-art developments by companies in producing more conductive and lower cost inks, such as NANOGAP's stable silver nanoparticle dispersions and multimodal particles. The conclusions are that while printed electronics growth has not met expectations, technical issues are now being solved and commercial uptake is increasing, which will help reduce costs and allow printed electronics to compete.

1. Masterclass: Future of Conductive Printing
Conductive Ink Development
Dr Allen Reid, Commercial Director, NANOGAP

2. Conductive Ink Development
• Current Status
– Market Size
– Types of Ink
– Applications
• Market Drivers and Barriers
• CLIP Project
– Objectives
– Tasks
– Achievements
• State of the Art Developments
– NANOGAP stable and Multimodal Ag Dispersions
– Intrinsiq Nano Cu
– NANOGAP Ag Nanofibers
– Market Round-up
• Conclusions

3. Current Status – Conductive Inks*
• 2012 market size: $2.86 billion, dominated by silver flake inks
• 2018 forecast: $3.36 billion, of which $735 million is based on nano Ag and Cu
Conductive Ink Type / Applications Advantage Disadvantage
Material Printing process
Silver Flake Predominantly Silicon PV, membrane Cost effective for Limited conductivity,
Screen printing switches, automotive, many applications thick films, surface
EMI shielding, screen roughness, difficult
heaters to photocure
Silver Thin films, flexibility, High cost, can have
Nanoparticles high conductivity, poor adhesion
Silicon PV, logic and rapid photocuring
Predominantly
memory, packaging,
Copper Inkjet Same as Ag NP, but Can oxidise and lose
PCBs, RFID, OPV, sensors
Nanoparticles lower cost conductivity
Silver Nanowires Screen, die-slot Tranparent Conductive Compared to Difficult to inkjet
Films for touchpanels, sputtered ITO, lower print, Haze
solid state lighting and cost and improved
PV conductivity
* Adapted from IDTECHEX report: Conductive Ink Markets, 2012

4. Market Drivers
• Silver flake inks for screen printing will continue to dominate with largest market share
– Mature technology, competitive pricing, sufficient technical performance for most applications
– However, PV is biggest market, and move towards ultra thin crystalline silicon PV may require the use of
inkjet printing with nanoparticle base inks
• Other emerging opportunities which require printing onto delicate or irregular shaped
objects will also drive a move towards ink jet and and nanoparticle inks
• The ability to print onto cheap flexible substrates (polymer film, paper) requires low
temperature sintering which is also driving a move towards nanoparticle inks
• For transparent conductive films (TCF) there is an overwhelming requirement for an
alternative to sputtered ITO due to cost, supply and performance issues
– Silver nanowire / nanofiber inks can be formulated into inks and printed to form TCFs with technically
superior conductive properties to ITO films for use in touch panels, solid state lighting and PV applications

5. Market Barriers
• Cost
– Nanoparticle silver is significantly more expensive that
silver flake
– However with market uptake and economies of scale
nanoparticle inks will become more cost competitive
– Total in-use cost needs to be considered rather than a
price comparison of inks
• Technical
– Long term stability of nanoparticle inks is a key concern
for large scale commercial uptake
– High resolution printing e.g. 10 microns required for
transistor applications
– Value chain integration including optimization of
conductive ink formulations for specific printing
processes and products

6. CLIP: Conductive Low Cost Ink Project
Objectives
• Development, formulation, and
feasibility of low cost inks
• Development of optimized inks for
screen, flexo, rotary gravure and
inkjet
• Optimization of inks for large area
printing with high resolution, <50
microns
• Prepare demonstrators

7. CLIP: Conductive Low Cost Ink Project
Ink Development Tasks
Materials Ink Formulation Printing
USC and NANOGAP developed PRA developed screen and flexo KTH performed inkjet trials with
and supplied multi-modal Ag NP inks based on: inks developed by Sirris
dispersions Cu flakes + Cu NP
Cu flakes + Ag NP
Sirris performed inkjet trials
IML supplied Cu nanoparticle
with inks developed by Sirris
dispersions
Sirris developed inkjet inks based
on:
USC developed Ag coated Cu NP Sirris performed aerosol jet
Ag NP dispersions
trials with Ag dispersions
Multi-modal Ag NP dispersions,
AVL developed and supplied supplied by USC / NANOGAP
Cu NP dispersions
micro Cu flakes
Acreo performed screen and
Sirris developed and supplied Ag flexo trials with inks developed
coated micro Cu flakes by PRA
Commercially sourced materials
included:
Ferro Ag coated Cu flake,
Cabot Ag inkjet ink,
DuPont Ag screen and flexo inks

8. CLIP: Conductive Low Cost Ink Project
Ink Development Achievements
• Screen and Flexo Inks (Cu flake + Cu NP)
– Good Printing properties
– Sheet Resistance after flash curing = 1 Ω∕□
– Work on-going to optimise formulation to improve conductive properties
– Raw material cost of inks ~230€/kg, so after adding process costs and margins
selling price is estimated at <500€/kg which compares favourably to commercial
ink prices
• Inkjet Inks (NANOGAP / USC Uni-modal and Multi-modal Ag) 5.00
Sheet resistance (ohm per square)
dropspacing 20 µm, PEL, 1 Layer
– Good printing properties from all Uni-modal and multi-modal Ag inks
4.00
– Sirris demonstrated lower sintering temperatures and improved conductivity of tri-
modal ink compared to equivalent multi-modal ink and commercial reference 3.00
2.00
• Aerosol Jet Inks (NANOGAP / USC Uni-modal and Multi-modal Ag)
1.00
– Good printing properties from all Uni-modal and multi-modal Ag inks
– On paper, bi and tri-modal inks achieved 3.5 to 4 x bulk Ag resistivity compared to 0.00
5 x for mono-modal 0 20 40 60 80 100
curing time at 120°C (first 20 mins), then 150°C (minutes)
– On PET, bi-modal ink achieved 4 x bulk Ag resistivity compared to 11 x for mono-
modal mono tri commercial ink
• Potential cost savings in inkjet and aerosol jet printing are achievable
through more efficient use of silver (level of conductivity achieved
from weight of silver deposited) as a result of performance
improvements

9. State of the Art Developments:
NANOGAP Stable Ag NP Dispersions
125
100 42,52±14,5 nm
75
50
25
0
10 20 30 40 50 60 70 80 90 100 110
Diameter (nm)
40 nm Ag Nanoparticle
dispersions with excellent long
term stability available for ink
formulators
NGAP FI Ag-4101
Ag Content (wt %) 30
Inkjet Trials at PEL Aerosol Jet Trials at Sirris
Ag Mean Particle Size 40 - 60 • Printed onto paper • Printed onto paper and PET
(nm)
Ag Particle Size 25-75 with Xaar print head • Laser cured
Distribution (nm) (95% wt) • Cured at 120oC for 2 • On Paper, 5x silver bulk
Viscosity (cP) 8 - 10
Surface Tension 25 - 28 minutes resistivity
(mN/m)
Carrier Liquid Ethylene Glycol
• Resistivity = 4.4x10-5 • On PET, 11x silver bulk
& IPA Ω.cm resistivity
Surface Functionality PVP

10. State of the Art Developments:
NANOGAP Multi-modal Technology
• Multi-modal particle size distributions
improve particle packing leading to
improved sintering and conductivity
• Very small size (<1nm) AQC promote
low temperature sintering
• Development samples currently under
evaluation
Development Samples
DS13 Bi-modal (40nm/6nm) in EG/IPA blend with
water at <3% Aerosol Jet Printing Trials at Sirris
DS15 Bi-modal (40nm/6nm) in EG with water at • Printed onto Paper and PET
<3%
Bi-modal (40nm/6nm) in EG/IPA blend
• Laser cured
DS20
with BYK 430 and water at <7% • For DS13, 4x silver bulk resistivity on PET and Paper
DS29 Tri-modal (40nm/6nm/<1nm) in EG/IPA • For DS29, 3.5x silver bulk resistivity on Paper
blend with water at 3%

11. State of the Art Developments:
Intrinsiq Nano Cu
• Nano Cu produced by Plasma Process
• Product is surface treated with organic coating (to
promote dispersion, and reduce reactivity, but maintain
electrical conductivity (patented process)
• Suitable for direct formulation into inkjet ink (size <
50nm)
– Formulated inks available
– Between 1.5 and 5 x bulk Cu conductivity
– Once sintered, the tracks can maintain performance, are
equivalent to PCB tracks and can be similarly treated for
extended life
• Suitable for formulation with micron copper into screen
print ink
• Potential for
– Offset litho
– Flexo
– Gravure
• Coating process available for other metals – nickel and
STEM image of nano copper with organic coating which
silicon inks in development encapsulates the nanoparticles

12. State of the Art Developments:
NANOGAP Ag Nanofibers for TCF
• Ag Nanofiber dispersions available
to ink formulators
• Alternatives to ITO transparent
conductive films are required for
many opto-electronic applications
including touch panels and solid
state lighting
• Inks based on NANOGAP silver
nanofibers have been used to
prepare TCF with sheet resistance
<50ohms/sq and total light
TYPICAL CHARACTERISTICS
transmission > 95%
NanoFiber Diameter (nm) 80 – 120
5% wt dispersions available in the following liquids
(95% wt/wt)
NGAP NP Ag-3103-W Water
NGAP NP Ag-3103-E Ethanol
NanoFiber Length 5 – 50
(µm) (95% wt/wt) NGAP NP Ag-3103-EG Ethylene glycol
NGAP NP Ag-3103-IPA Isopropyl alcohol
Mean NanoFiber Length (µm) 20-30
NGAP NP Ag-3103-Bt Butanol
NGAP NP Ag-3103-B Benzyl alcohol
Surface Functionality PVP

13. State of the Art Developments:
Market Round-up* (1)
• Dupont MicroCircuit Materials
– Inks for thinner printed lines
– Eliminating precious metal and replace with low cost conductors
– Improving ink functionality e.g. for heaters and sensors
– Printed conductors replacing wires e.g. heaters and automotive interiors
– Inks for roll to roll printing
• Toyochem
– Ultrafine, low temperature, low resistivity
– Screen printing as alternative to photolithography and etching
– UV cured inks
– Alternatives to Ag
• Other companies working on thin lines and features <50 microns
– Pchem
– Creative Materials
* Principal Source : printedelectronicsnow.com

14. State of the Art Developments:
Market Round-up* (2)
• NovaCentrix
– Ag and Cu based nanoparticle inks
– PulseForge Photonic curing system
– Copper Oxide based inks reduce in-situ to Copper metal during PulseForge
Sintering
• SunChemical
– Inks for thin film PV technology
– Inks for OPV for BIPV market
• Metalonix
– “liquid metal” inks composed of metal atoms that convert to metal at low
temperature following printing
• Other Conductive Inks
– Vorbeck Graphene inks for screen, flexo, gravure
– Bayer aqueous CNT Inks for inkjet, gravure and screen
– PEDOT:PSS from Agfa and Clevios
* Principal Source : printedelectronicsnow.com

15. Conclusions
• Nano particle based inks for printed electronics has been one of the many over-
hyped areas of nanotechnology, with the market growth failing to meet expectations
over the last 10-20 years
• However, there is now good signs on the commercial uptake of nano particle based
inks
• Innovation is solving technical problems and leading to improved products
– Stable nano inks,
– Efficient ,and high conductivity,
– Low temperature sintering
• Cost issues are being addressed
– With commercial uptake and scale up cost will fall and competive position will rise
– Cheaper Cu systems now available
– Must consider whole process cost and not jut price of ink
• Supply chain collaborations and strategic partnerships are key to success
– Companies that make conductive particles are not necessarily the best ink formulators

16. Allen Reid
a.reid@nanogap.es
+44 7980 866 656
www.nanogap.es