Organic Substrate - LCP

• Liquid Crystal Polymer (LCP) can be used as a high performance multilayer substrate

• Excellent electrical properties (εr ~ 3.10 and tanδ=0.002)

• Flexible (printed circuits can be rolled or molded into desired shape)

• Good performance: mechanical integration compatibility and economic viability

Wideband (9%) UHF RFID tag on LCP to cover the global 860-930 MHz band

Antennas fabricated on 12”x12” in LCP Film

Why consider LCP as a substrate?

Why Consider Paper as a Substrate?

- Environmental Friendly and low cost (LOWEST COST MATERIAL MADE BY HUMANKIND)

- Large Reel to Reel Processing

- Low surface profile with appropriate coating

- Compatible for printing circuitry by direct write methodologies

- Host nano-scale additives (e.g. fire retardant textiles)

- Can be made hydrophobic

- Dielectric constant εr (~3) close to air’s, allowing EM waves to penetrate substrate easily with minimum (5-6%) power reflection

Coated paper

Drop of water on hydrophobic paper

Organic Substrate - Paper

The down shifted TEmnp mode resonant frequency between an empty and a lorded cavity gives the information of the sample dielectric constant.

Empty Cylinder (unloaded)

peak shifting

Paper Sample Inserted (loaded)

TE011 ∆f=2.2%

Paper Dielectric Properties Characterization

Characteristics:

• Piezo-driven jetting device to preserve polymeric properties of ink

• 10 pL drops give ~ 21 µm

• Drop placement accuracy ±10 µm gives a resolution of 5080 dpi

• Drop repeatability about 0.5%

• Printability on organic substrates (LCP, paper …)

Inkjet-printing Technology - Printer

High resolution inkjet printed copper (50 µm)

Nano-sized Silver Ink Particle Size = 30 nm SEM Images of a Layer of Printed ink, Beore and

After a 15 Minute Cure at 150ºC

Ink:

• Consisting of nano-spheres melting and sintering at low temperatures (150 °C)

• After melting a good percolation channel is created for electron flow

• Provides a better result than traditional polymer thick film material approach which uses metal flakes

Inkjet-printing Technology - Ink

Carbon Nanotubes as Gas Sensor

� CNTs structure can be conceptualized by wrapping a one-atom-thick layer of graphite into a seamless cylinder.

� Single-walled CNTs and Multi-walled CNTs

� A diameter of close to 1 nanometer, with a tube length that can be many thousands of times longer.

� CNTs composites have electrical conductance highly sensitive to extremely small quantities of gases, such as ammonia (NH3) and nitrogen oxide (NOx).

� The conductance change can be explained by the charge transfer of reactive gas molecules with semiconducting CNTs.

CNT Particles : Single Walled CNT

Solvent : Dimethylformamide (DMF)

1. Particle size < 215um

2. Viscosity 10-13 cps

3. Surface tension 28 dynes/cm

Inkjet-printed SWCNT Films

Overlapping Zone

500um

10L

15L

20L

25L

SWCNT Film

Silver Electrode

� Silver electrodes were patterned before depositing the SWCNT film, followed by a 140˚C sintering.

� The electrode finger is 2mm by 10mm with a gap of 0.8mm. SWCNT film was 2mm by 3mm.

� 1.1mm overlapping zone to ensure the good contact between the SWCNT film and the electrodes.

Formulation:

- P2 sample from purified SWCNT by air oxidation and catalyst removing (aggregated at the concentration of 0.1mg/ml)

- P3 sample from purified SWCNT after nitric acid processing (go up to 0.4mg/ml)

- 0.4mg/ml P3 sample dispersed in DMF

- 12 hours sonication to prevent aggregations of large particle residues.

Gas Chamber Measurement

� Gas chamber: gas inlet, outlet and exhaust hood

� 4% Ammonia gas for 30 minutes

� SWCNT stable response up to 1GHz

� 25L was used for future steps

25L 20L

Antenna Design and Performance

EU RFID Band

� Bandwidth 810MHz – 890MHz

� When bended 814MHz – 891MHz

� 2.01dBi Directivity with 94.2% efficiency.

� Conductive ink has become the major cost of an RFID tag after introducing the paper-based substrate.

� Minimizing the amount of ink used per antenna will save thousands of dollars in the mass production.

Gas Detection

( ) ηλ

π+−

−++= dGGPP

rttr 1010 log404

log4022

SWCNT Film @868MHz Z=51.6-j6.1 Ohm in air

Z=97.1-j18.8 Ohm in NH3

Tag Antenna @ 686MHz

Zant=42.6+j11.4 Ohm

2

*

ANTload

ANTIoad

ZZ

ZZ

+

−=η

+

+

� Power reflection coefficient changes from -18.4dB to -7.6dB. At reader’s side, this means 10.8dBi increase of the received power level.

� By detecting this backscattered power

differnce, the sensing function is fulfilled.