Please enable JavaScript.
Coggle requires JavaScript to display documents.
Development of Printable Platinum Ink Nano-Films (Previous literature…
Development of Printable Platinum Ink Nano-Films
Overview
Abstract
Inkjet printing of functional materials
Platinum organometallic inks
Organometallic: Chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal
Produce films with similar resistivity to bulk platinum
Printed and tested 4 patterns
Increased platinum in the nano films, reducing printing time by 25%
Precious metals: Excellent conductivity, high melting point, biocompatability
Platinum had not previously been used for the creation of thin films due to the cost of traditional material deposition methods in small quantities
Goal: Further develop the platinum films, improve electrical performance
Previous literature
Additive manufacturing
The process of joining materials to make objects from 3D model data, usually layer upon layer, as opposed to subtractive manufacturing technologies
Focus here is material jetting, hailed as a reliable way to create complicated pieces of equipment
Demand for precious metals in medical field for thin films, they're non-corrosive and non-reactant but high cost as thin-film deposition is generally high waste
Inkjet printing
Fabricate electronic circuits using conductive inks, cure at high temperatures
Continuous inkjet printing: liquid jet subject to a force that breaks the droplets to a uniform size, guided to place by an electric field
High risk of contamination
Deposit on demand (DOD): Ink is formed and ejected only when required by a piezoelectric force on the chamber
Nanoparticle inks: Carrier ink contains nanoparticles of a conductive metal, evaporate the carrier ink, problems with distribution of the nanoparticles
Organometallic inks: Inks that use solvated organometallic particles
Ceimig
Jettable ink: 1<Z<10
Z=1/Oh (Inverse of Ohnesorge number)
Oh=sqrt(Webber no.)/(Reynolds no.)
Droplet formation and ejection in DOD inkjet
Thermal or piezoelectric forces
Electrical potential to piezoelectric element, channel is deformed, pressure disruption travels in waves
Pressure wave and nozzle acts against viscous dissipation and surface tension, driving through a single drop
Waveform
Stabilised
Decrease voltage, meniscus moves upwards
Maximum voltage, chamber compressed, increase in ink levels and ejection occurs
Reduce voltage to control tail of drop
Volume ejected depends on force applied and thus voltage applied
For a stable drop, tail and head completely merge before impact with substrate
Sufficient jetting distance is generally around 2-3cm at 6-12m/s
Substrate interaction
On contact, drop spreads due to inertial forces, then withdraws due to surface tension
Final drop spread with a diameter d0 can be calculated (there's an equation)
Contact/receding angle dictates drop interactions on the substrate
Coffee-stain effect: Evaporation of solvents quicker on boundaries
Platinum
Most previous work in gold inks
Unique qualities
Precious
Highly non-reactive
Highly conductive
Bio compatible
Applications
Biosensors
Fuel cells
Pacemakers (current use)
Electrophysiology catheter tips
Project scope
Previous studies largely focused on printing method
Goldie: Temperature dependence of the resistivity in Pt films is closer to bulk platinum than previously thought
Goal here is to test the reproducability of the results
Methods
Inkjet printing and ink characterisation
Printer
Drop-on-Demand
Deposit platinum organometallic ink onto glass substrates
Dimatix Fujifilm DMP-2800
Ink
Injected into a print-head cartridge
Prepared by completing a 3 second purge (wetted nozzles, ensured no blockages)
Pulse-width and velocity monitored with camera
Pattern was a serpentine track 1mm width 50mm length
Ink concentrations
Viscosity changer added to ink to increase viscosity
Inks had 2 volume ratios organometallic carrier ink : Cyclohexanol
20:80
50:50
Also tested Toluene-Cyclopentanone solvent solution that carries the platinum organometallic inks
Density
Weight measurements of 1ml at 18-19C
Viscosity
Viscometer tube in constant temperature bath
Viscosity at 30C important as optimal for the ink chamber
Surface Tension
Used Kruss drop-watcher at 20C
Use Tate's Law to determine drop weight
Waveforms
Two created due to different viscosities of inks
20:80 - 2.048us, 25V maximum
50:50 - 4.48us, 16.9V maximum
Curing and electrical measurements
Curing process
Glass substrates placed on ceramic slide in furnace
320C for 5 minutes
Volatile elements evaporate, soluble organometallic molecule forms platinum
Electrical measurements
0-1V in 0.1V increments
Resistance measured at each increment
150-425K
Height Profiling
Surface profilimeter
Measure resistivity factor from w,h,l measurements
Results
Height measurements
Film surface broke up in places, particularly sample 1
Film not curing uniformly, evaporated solvents trapped under surface layer of ink
Is the increased platinum deposition with the 50:50 ink producing thicker films and inhibiting uniform solvent evaporation when curing?
Samples
50:50, 15um drop overlap, 3 layers, 8m/s velocity, aged organometallic
50:50, 15um, 3, 8m/s, aged organometallic
50:50, 20um, 3, 7m/s, newer organometallic
20:80, 20um, 4, 6.5m/s, newer organometallic
Ref. 20:80, 20um, 4, 7.5m/s, from Goldie paper
Resistance measurements
Reference sample: 700-1102Ω
Sample 2: 371.21-422.18Ω
Sample 3: 747.35 - 1020.8Ω
Sample 4: 7.11 - 7.85kΩ
Sample 1: 253.77 - 327.96Ω
Conclusions
Sample 4 shows 700% increase in resistance versus Goldie paper
Sample 3 and reference show a 9% resistance improvement at room temperature
Sample 3 had 1 less layer, reducing printing time by 25%
Sample 2 had a 50% or resistance at room temperature
Sample 1 and 2 showed break up of film surface near centre of track
Further work
Optimisation of the curing process
Cure at lower temperatures?
Can viscosity of inks be reduced further?
What is the shelf life of the ink?
