Bioresorbable electronic devices are currently fabricated by complex and expensive vacuum-based Integrated Circuits (IC) processes. In this paper, we report a low-cost manufacturing approach for bioresorbable conductors on bioresorbable polymer substrates by evaporation-condensation-mediated laser printing and sintering of Zn nanoparticle. Laser sintering of Zn nanoparticles has been technically difficult due to the readily formation of surface oxide. We report a novel way to print and sinter Zn nanoparticle on low temperature substrate facilitated by evaporation-condensation in confined domain. This new approach circumvents the surface oxide, which notoriously hinders the nanoscale sintering process. The entire metallization process can be realized in non-vacuum environment allowing easy integration on a roll-to-roll production platform for economical manufacturing of bioresorbable electronics.
There have been extensive research on micro/nano additive manufacturing methods employing laser (or optical) and ion/electron beams. Many of these processes utilize specially designed photosensitive materials consisting of additives and effective components. Due to the presence of additive (such as polymer and binders), the effective components are relatively low resulting in high threshold for device operation. In order to direct print functional devices at low cost, there has been extensive research on laser processing of pre-synthesized nanomaterials for non-polymer functional device manufacturing. Pre-synthesized nanocrystals can have better control in the stoichiometry and crystallinity. In addition, pre-synthesis process enjoys the flexibility in material choice since a variety of materials can be synthesized.
In this paper, we report femtosecond laser assembly and deposition of nanomaterials for 3D micro/nano additive manufacturing. The laser-nanomaterial interaction and nanomaterial transport under laser excitation and modification are studied. A scheme to directly printing functional nanostructures was demonstrated by laser excitation of gold nanocrystals. The scheme paves the way for laser selective electrophoretic deposition as a micro/nanoscale additive manufacturing approach.
Direct writing using single or multiple energized beams (e.g. laser, ion or electron beams) provides high feature resolution (<1μm) compared with other solution-based printing methods (e.g. inkjet printing). There have been extensive researches on micro/nano additive manufacturing methods employing laser (or optical) and ion/electron beams. Many of these processes utilize specially designed photosensitive materials consisting of additives and effective components. Due to the presence of additive (such as polymer and binders), the effective components are relatively low resulting in high threshold for device operation. In order to direct print functional devices at low cost, there has been extensive research on laser processing of pre-synthesized nanomaterials for non-polymer functional device manufacturing. Pre-synthesized nanocrystals can have better control in the stoichiometry and crystallinity. In addition, pre-synthesis process enjoys the flexibility in material choice since a variety of materials can be synthesized. Femtosecond laser assembly and deposition of nanomaterials can be a feasible 3D micro/nano additive manufacturing approach, although mechanisms leading to assembly and deposition have not been fully understood. In this paper, we propose a mechanism for 2D and 3D deposition of nanocrystals by laser excitation with moderate peak intensities(1011-1012 W/cm2). It is postulated that laser induced charging is responsible for the deposition. The scheme paves the way for laser selective electrophoretic deposition as a micro/nanoscale additive manufacturing approach.
Inkjet direct writing of functional materials provides a promising pathway towards realization of ultra-low-cost, largearea
printed electronics, albeit at the expense of lowered resolution (~20-50 μm). We demonstrate that selective laser
sintering and ablation of inkjet-printed metal nanoparticles enables low-temperature metal deposition as well as highresolution
patterning. Combined with an air-stable carboxylate-functionalized polythiophene, all-inkjet-printed and
laser-processed organic field effect transistors with micron to submicron critical feature resolution were fabricated in a
fully maskless sequence, eliminating the need for any lithographic processes. All processing and characterization steps
were carried out at plastic-compatible low temperatures and in air under ambient pressure. The fundamental mechanisms
of the nanoparticle sintering process have been investigated by both Molecular Dynamics (MD) simulations as well as
in-situ probing.
In-situ experimental work on laser induced pressure waves in water is presented in this paper. A double frequency
Nd:YAG laser(532 nm, 4 ns pulse width) was irradiated on a chromium thin film on quartz substrate in contact with
water. A plane pressure wave with high temporal and spatial resolution was generated by the laser induced
thermoelastic stress around 8~12 mJ/cm2 below the regime of shock wave generation. The pressure wave was
observed to propagate at the speed of sound in water. The plane acoustic wave could be interacted and focused with
solid structures. FEM numerical simulations of the aforementioned phenomena are also carried out to solve the 2D
transient wave equation and compared with the experimental results.
The low temperature fabrication of OFET (organic field effect transistor) on the flexible polymer substrate is
presented in this paper. A drop-on-demand (DOD) ink-jetting system was used to print gold nano-particles suspended
in Alpha-Terpineol solvent, PVP (poly-4-vinylphenol) in PGMEA (propylene glycol monomethyl ether acetate)
solvent, semiconductor polymer (modified polythiophene) in dichlorobenzene (o-DCB) solution to fabricate OFET on
flexible polymer substrates. Short pulsed laser ablation enabled finer electrical components to overcome the resolution
limitation of inkjet deposition. Continuous Argon ion laser was irradiated locally to evaporate carrier solvent as well
as to sinter gold nano-particles. In addition, a new selective ablation of multilayered gold nanoparticle film was
demonstrated using the SPLA-DAT (selective pulsed laser ablation by differential ablation threshold) scheme for
sintered and non-sintered gold nanoparticles. Finally, selective ablation of multilayered film was used to define narrow
channel of a FET (field effect transistor) and semiconductor polymer solution was deposited on top of channel to
complete OFET (organic field effect transistor) fabrication.
The low temperature fabrication of active (field effect transistor) electrical components on flexible polymer substrates
is presented in this paper. A drop-on-demand (DOD) ink-jetting system was used to print gold nano-particles
suspended in organic solvent, PVP (poly-4-vinylphenol) in PGMEA (propylene glycol monomethyl ether acetate)
solvent, semiconductor polymer in organic solvent to fabricate passive and active electrical components on flexible
polymer substrates. Short pulsed laser ablation enabled finer electrical components to overcome the resolution
limitation of inkjet deposition. Continuous Argon ion laser was irradiated locally to evaporate the carrier solvent as
well as to sinter gold nano-particles. In addition, a new method for the selective ablation of multilayered gold
nanoparticle film was demonstrated.
Molecular Dynamics simulations were employed to investigate the mechanism and kinetics of the sintering of two crystalline gold nanoparticles (4.4-10.0nm) induced by low energy laser heating. At low temperature (300K), sintering can occur between two bare nanoparticles by elastic and plastic deformations driven by strong local potential gradients. This initial neck growth occur very fast (<150ps), therefore they are essentially insensitive to laser irradiation. This paper focuses on the subsequent longer time scale intermediate neck growth process induced by laser heating. The classical diffusion based neck growth model is modified to predict the time resolved neck growth during continuous heating with the diffusion coefficients and surface tension extracted from MD simulation. The diffusion model underestimates the neck growth rate for smaller particles (5.4nm) while satisfactory agreement is obtained for larger ones (10nm). The deviation is due to the ultra-fine size effect of below 10nm particles. Possible mechanisms were discussed.
The low temperature fabrication of passive electrical components (conductor, capacitor) on the flexible polymer substrate is presented in this paper. A drop-on-demand (DOD) ink-jetting system was used to print gold nano-particles suspended in Alpha-Terpineol solvent and PVP in PGMEA solvent to fabricate passive electrical components on flexible polymer substrate. Short pulsed laser ablation enabled finer electrical components to overcome limitation of inkjet process. Continuous Argon ion laser was irradiated locally to evaporate carrier solvent as well as to sinter gold nano-particles. In addition, a self alignment technique for PVP layer was demonstrated taking advantage of the deliberate modification of surface wetting characteristics. Finally, a new selective ablation of multilayered gold nanoparticle film was demonstrated using the ablation threshold difference for sintered and non sintered gold nanoparticles.
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