3 research outputs found
Electroless Copper Plating of Inkjet-Printed Polydopamine Nanoparticles: a Facile Method to Fabricate Highly Conductive Patterns at Near Room Temperature
Aqueous dispersions of artificially
synthesized, mussel-inspired polyÂ(dopamine) nanoparticles were inkjet
printed on flexible polyethylene terephthalate (PET) substrates. Narrow
line patterns (4 ÎĽm in width) of polyÂ(dopamine) resulted due
to evaporatively driven transport (coffee ring effect). The printed
patterns were metallized via a site-selective Cu electroless plating
process at a controlled temperature (30 °C) for varied bath times.
The lowest electrical resistivity value of the plated Cu lines was
about 6 times greater than the bulk resistivity of Cu. This process
presents an industrially viable way to fabricate Cu conductive fine
patterns for flexible electronics at low temperature, low cost, and
without need of sophisticated equipment
Interfacial Targeting of Sessile Droplets Using Electrospray
We
report on the use of electrospray atomization to deliver nanoparticles
and surfactant directly to the surface of sessile droplets. The particles
delivered to the target droplet remained adsorbed at its interface
since they arrived solvent-free. Upon complete evaporation, the interface
of the target drop was mapped to the underlying substrate, forming
a nanoparticle deposit. The use of electrospray permitted the exploration
of the interfacial particle transport and the role of surfactants
in governing particle motion and deposit structure. When no surfactant
was present in the sprayed solution, there was no observable convection
of the interfacial particles. When Tween 80, a high-molecular-weight
surfactant, was added to the sprayed solution, the surface flow was
similarly suppressed. Only when small surfactants (e.g., sodium dodecyl
sulfate) were present in the sprayed solution was Marangoni flow,
directed toward the droplet apex, induced at the interface. This flow
drove the interfacial particles to the apex of the target droplet,
creating a particle-dense region at the center of the final deposit.
We found that small surfactants were capable of desorbing from the
interface at a sufficiently high rate relative to the evaporation
time scale of the target droplet. Once inside the drop, the desorbed
surfactant was convected to the contact line where it accumulated,
inducing a surface tension gradient and a solutal Marangoni flow.
Numerical modeling using the lattice Boltzmann–Brownian dynamics
method confirmed this mechanism of particle transport and its relationship
to deposit structure. The use of sacrificial targets combined with
electrospray may provide a unique capability for building colloidal
monolayers with organized structure in a scalable way
Regulation of the Deposition Morphology of Inkjet-Printed Crystalline Materials via Polydopamine Functional Coatings for Highly Uniform and Electrically Conductive Patterns
We report a method to achieve highly
uniform inkjet-printed silver nitrate (AgNO<sub>3</sub>) and a reactive
silver precursor patterns on rigid and flexible substrates functionalized
with polydopamine (PDA) coatings. The printed AgNO<sub>3</sub> patterns
on PDA-coated substrates (glass and polyethylene terephthalate (PET))
exhibit a narrow thickness distribution ranging between 0.9 and 1
ÎĽm in the line transverse direction and uniform deposition profiles
in the line axial direction. The deposited reactive silver precursor
patterns on PDA-functionalized substrates also show “dome-shaped”
morphology without “edge-thickened” structure due to
“coffee-stain” effect. We posit that the highly uniform
functional ink deposits formed on PDA-coated substrates are attributable
to the strong binding interaction between the abundant catecholamine
moieties at the PDA surface and the metallic silver cations (Ag<sup>+</sup> or AgÂ(NH<sub>3</sub>)<sup>2+</sup>) in the solutal inks.
During printing of the ink rivulet and solvent evaporation, the substrate–liquid
ink (S–L) interface is enriched with the silver-based cations
and a solidification at the S/L interface is induced. The preferential
solidification initiated at the S–L interface is further verified
by the in situ visualization of the dynamic solidification process
during solvent evaporation, and results suggest an enhanced crystal
nucleation and growth localized at the S–L interface on PDA
functionalized substrates. This interfacial interaction mediates solute
transport in the liquid phase, resulting in the controlled enrichment
of solute at the S–L interface and mitigated solute precipitation
in both the contact line region and the liquid ink–vapor (L–V)
interface due to evaporation. This mediated transport contributes
to the final uniform solid deposition for both types of ink systems.
This technique provides a complementary strategy for achieving highly
uniform inkjet-printed crystalline structures, and can serve as an
innovative foundation for high-precision additive delivery of functional
materials