Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/02—Printing inks
  • C09D11/03—Printing inks characterised by features other than the chemical nature of the binder
  • C09D11/037—Printing inks characterised by features other than the chemical nature of the binder characterised by the pigment
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/02—Elements
  • C08K3/04—Carbon
  • C08K3/042—Graphene or derivatives, e.g. graphene oxides
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/02—Elements
  • C08K3/08—Metals
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K9/00—Use of pretreated ingredients
  • C08K9/02—Ingredients treated with inorganic substances
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/02—Printing inks
  • C09D11/03—Printing inks characterised by features other than the chemical nature of the binder
  • C09D11/033—Printing inks characterised by features other than the chemical nature of the binder characterised by the solvent
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/30—Inkjet printing inks
  • C09D11/32—Inkjet printing inks characterised by colouring agents
  • C09D11/322—Pigment inks
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/52—Electrically conductive inks
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
  • C09D5/24—Electrically-conducting paints
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
  • C09D7/40—Additives
  • C09D7/60—Additives non-macromolecular
  • C09D7/61—Additives non-macromolecular inorganic
  • C09D7/62—Additives non-macromolecular inorganic modified by treatment with other compounds

Definitions

• the present disclosure relates to material, methods, and process for synthesis, deposition, and laser processing of a graphene oxide coated liquid metal Nano particles, for applications in stretchable electronics, stretchable and flexible stretchable and flexible optoelectronics devices such as displays and photovoltaics, stretchable and flexible energy storage devices, sensors, and memory devices.
• Transparent conductors based on high-aspect ratio conductors such as AgNWs have been investigated by several groups during the past years.
• High aspect ratio conductors percolate at low percentages of metal, thus permitting formation of conductive thin-films with large empty spaces.
• AgNWs are extremely costly, their deposition is challenging, and suffer from low adhesion to substrates, and poor contact at wire-wire junctions.
• These problems are obstacles against their scalable fabrication, and affect their performance against mechanical strain.
• the tolerance to strain and strain cycle is usually limited. This is associated with the brittle nature of the nanowire junctions and their high contact resistance.
• LMs liquid metals
• EGain Eutectic Gallium Indium
• GF Gauge Factor
• materials and methods for low-cost and scalable fabrication of a stretchable transparent conductor based on specially engineered liquid metal nano droplets is shown. This is performed by surface modification of liquid metal droplets using graphene oxide sheets, or engineering composites in which liquid metal droplets bind to high aspect ratio carbon based sheets, such as Graphene Oxide (GO), followed by posterior laser assisted sintering.
• GO Graphene Oxide
• the synthesis technique, and by changing the amount of graphene oxide in the formulation, the deposition technique and posterior sintering parameters it is obtained a variety of composites that differ in transparency, conductivity, mechanical and chemical resilience. It was also engineered to be applicable through different methods of application, including spray coating, and thin-film application through roll coating or blade coating.
• an Infrared fiber laser to sinter the ink into highly conductive, stretchable and transparent film.
• the laser sintering typically makes the non- conductive or very poorly conductive electrodes (e.g. in the order of Mega Ohm / Cm 2 ) to highly conductive electrodes (ohm/ cm 2 range).
• EGain nanoparticles with their gallium oxide shell and liquid core assembly, have been reported as a laser sensitive material, inducing the production of conductive patterns on soft substrates like PDMS (polydimethylsiloxane).
• PDMS polydimethylsiloxane
• the laser ruptures the nanometric GajC semiconductor shell around the EGain particles, resulting in formation of conductive EGain micropaths [7,8],
• obtaining electrical transparency is unique feature that happens only by surface modification of the EGain nano particles.
• the liquid metal droplets in previous works are very PH sensitive, and rapidly aggregate into larger spheres in highly acidic or basic solutions, thus limiting many of their applications, for instance in energy storage or sensor electrodes.
• Graphene Oxide (GO) is used for the purpose of surface modification, the overall concept can be extended to other materials that are able to bond to gallium oxide through galvanic replacement or surface charges. This material is then applied over a substrate as a thin-film, and sintered by laser.
• the film can be sintered, or ablated, to adjust the transparency and conductivity.
• it was used a CO2 laser to create a semiconductor composite, that can be used as a Memristor that is programable through application of current, and also a pressure sensitive film, whose electrical resistance changes upon application of mechanical pressure.
• the applied film can be made slightly transparent by adjusting the dimensions of GO sheets, but the transparency is limited, and moreover the sample is not conductive, or is a very poor conductor.
• Laser sintering improves significantly the transparency and conductivity through various mechanisms. This includes partially reducing the graphene oxide, thinning the graphene oxide sheets, and aggregation and sintering of liquid metal particles. Laser assisted aggregation improves significantly the conductivity and as well the transparency. Conductivity is improved by 6 orders of magnitude, from mega ohms to ohms. That practically means nonconductive samples become conductive. Transparency is improved by reduce of the occupied surface and volume, due to aggregation of smaller particles into larger aggregates. Note that in all cases graphene oxide sheet act as guides, over which the liquid metal droplets bind. Therefore, their geometry, size and concentration has an important role is obtaining transparent conductors.
• the present disclosure relates to forthe first time materials and methods for obtaining transparent conductors.
• This includes new ink formulation and synthesis technique, including low-concentration and high-concentration GO-EGaln inks that can self-assemble into clusters for formation of 3D percolating network.
• film deposition techniques and is also shown for the first time laser processing of such composite, in which by adjusting the laser type and power, we obtain composites with partial sintering (kilo ohm conductivity range), full sintering (ohm range), and ablation. This permits fabrication of transparent or semi-transparent, flexible or stretchable electrodes, sensors, memristors, and energy storage devices.
• the disclosed invention permits a significant improvement both in conductivity and stretchability (over 6 times improvement compared to the highest records).
• Graphene decorated EGain particles can potentially combine the advantages of graphene, i.e. high surface area, excellent mechanical and chemical resistance, with the excellent electromechanical properties of liquid metals, e.g. high electrical conductivity. Besides, the solid-liquid interface between the graphene and the liquid metal can enhance the charge transfer within the composite.
• this technique can serve as a versatile method for rapid prototyping, and scalable fabrication of laser reduced GO@EGaln (Graphene Oxide-EGaln) electrodes with micron sized features in few seconds.
• CVD Chemical Vapor Deposition
• spin coating the simple coating technique used in this work, such as spray coating, thin-film application, or direct writing allows deposition of large area conductors.
• spray coating thin-film application
• direct writing allows deposition of large area conductors.
• the resulting electrodes after laser treatment present an acceptable repeatability in terms of electrical resistance, and surface roughness in micrometric range. Therefore, this material composition, and the fabrication method developed, is a step towards scalable and low-cost fabrication of graphene based large area electrodes, transparent stretchable conductors, energy storage electrodes, sensing devices, among others.
• a suspension or colloid comprising liquid metal droplets bound with graphene-based particles, wherein the liquid metal is gallium or a gallium alloy, and the graphene-based particles are selected from a list of graphene, graphene oxide, reduced graphene oxide, graphene quantum dots, carbon nanotubes, or combinations thereof.
• the liquid metal is gallium or a gallium alloy
• the graphenebased particles are selected from a list of graphene, graphene oxide, reduced graphene oxide, graphene quantum dots, carbon nanotubes, or combinations thereof [i.e. a netlike combination of filaments],
• the weight ratio between graphene-based particles to liquid metal droplets is 0.0001 - 0.5%, preferably 0.001 - 0.1%.
• an ink comprising a concentrated network according to any of the claims 2 - 4, obtainable by separation of said network from a colloid or suspension according to claim 1.
• the ink is obtainable by: suspending graphene-based particles in a first medium to obtain a first suspension, mixing liquid metal into the first suspension to obtain a mixture with the network of liquid metal droplets and graphene-based particles, and separating the concentrated network of liquid metal droplets and graphene-based particles from the mixture; or suspending liquid metal droplets in a second medium to obtain a second suspension, mixing graphene-based particles into the second suspension to obtain a mixture with the network of liquid metal droplets and graphene-based particles, and separating the concentrated network of liquid metal droplets and graphene-based particles from the mixture.
• the ink is obtainable by suspending graphene-based particles in a first medium to obtain a first suspension and suspending liquid metal droplets in a second medium to obtain a second suspension, mixing said suspensions and separating the concentrated network of liquid metal droplets and graphene-based particles from the mixture, where the first medium and second medium are miscible [the first medium and second medium can be seen as co-solvents],
• the separating is carried out by precipitation, centrifuge, and/or filtering.
• the first medium is water or an aqueous solvent
• both first medium and second medium are water or an aqueous solvent
• the second medium is ethanol or an alcohol-based solvent.
• a printable ink further comprising a binder for improving ink adhesion and/or viscosity, in particular for improving ink adhesion and/or viscosity for nozzle extrusion or screen printing.
• a conductor obtainable by applying a coating of suspension, colloid, network, or ink according to any of the disclosed embodiments over a substrate, and laser sintering said coating, in particular the conductor being an electrode or a circuit trace or a circuit.
• the conductor is transparent or translucid.
• the conductor is flexible or stretchable.
• the coating is carried out by spraying, rod-coating, slot-die, inkjet printing, aerosol jet printing, or blade coating.
• the conductor comprises conductive patterns obtainable by laser patterning or lithography.
• gallium alloy is an alloy of gallium-indium or gallium-indium-tin or eutectic gallium-indium.
• a process for obtaining a suspension or colloid comprising binding liquid metal droplets with graphene-based particles, wherein the liquid metal is gallium or a gallium alloy, and the graphene-based particles are selected from a list of graphene, graphene oxide, reduced graphene oxide, graphene quantum dots, carbon nanotubes, or combinations thereof.
• a process for obtaining a network of liquid metal droplets bound with graphene-based particles comprising binding liquid metal droplets with graphene-based particles, wherein the liquid metal is gallium or a gallium alloy, and the graphene-based particles are selected from a list of graphene, graphene oxide, reduced graphene oxide, graphene quantum dots, carbon nanotubes, or combinations thereof.
• the process for obtaining a suspension, colloid, or network includes coating liquid metal droplets with graphene-based particles.
• the first medium is water or an aqueous solvent
• both first medium and second medium are water or an aqueous solvent
• the pH of the aqueous solution containing graphene-based particles is between 1 to 6, preferably between 2 to 3.5.
• the second medium is ethanol or an alcohol-based solvent, in particular the liquid metal being 0.5-10% (w/w) of the ethanol or an alcohol-based solvent.
• the laser is a fiber laser having a wavelength ranging from UV to IR.
• the conductor comprises conductive patterns obtainable by laser patterning or lithography.
• a device comprising a suspension, colloid or network according to any of the disclosed embodiments, an ink according to any of the disclosed embodiments, or a conductor according to any of the disclosed embodiments.
• the device is an optoelectronic device, pressure or strain sensitive piezo resistive composite, a pressure or strain sensor, a temperature sensor, an electroluminescent device, a photovoltaic device, a memory device or an electrode for energy storage device.
• Figure 1 Schematic representation of an embodiment of the fabrication of rGO@EGaln composite, deposition and laser processing: A) composite synthesis via ultrasonic treatment and mixing; B) core-capsule structure of a single rGO@EGaln particle; C) spray coating on a glass substrate; D) laser irradiation of the rGO@EGaln films: from laser reduction to total film ablation.
• Figure 2 Illustration of results of an embodiment of a Laser parametrization for spray coated rGO@EGaln films: A-i) Sheet resistance of the films processed at different pulse widths; B-i) Sheet resistance of the films processed at different laser powers; A-ii) a sample showing the different laser marks made at different pulse widths; B-ii) a sample showing the different laser marks made at different laser powers; C) Sheet resistance of the films processed at different laser speeds; D) transmittances of the different films processed at different laser powers.
• Figure 3 Illustration of results of A) XRD diffraction patterns of spray coated and laser processed GO@EGaln films, with the amorphous and crystalline peaks detected for each sample.
• Figure 4 Schematic representation of GO-EGaln ink synthesis, deposition and activation.
• Figure 5 SEM imaging comparing laser processing on Liquid metal nano particles without (top), and with graphene oxide decoration (Bottom).
• Figure 6 Schematics of the GO@EGaln (Graphene Oxide-EGaln) network after deposition and after laser processing.
• Figure 6B Shows increasing the amount of GO (from I to III), increases the transparency of the electrode after laser sintering.
• Figure 7 Illustration of the comparing optical transparency of laser processed liquid metal nanoparticles without GO decoration (bottom) that is non-transparent, the film of GO- EGaln network (middle) that is semi-transparent, and the same film of GO-EGaln network (top), with significantly improved transparency and conductivity.
• Figure 8 Results of the optical transparency of laser processed electrode ( ⁇ 50-70%), and the same electrode further patterned by laser into honeycomb structure to further increase optical transparency to about 90%.
• Figure 9 the results of electrical resistance vs. Strain fortransparent conductors made by materials and methods disclosed in this work.
• Figure 10 Illustration of the results of electrical resistance of the sample under 5000 repetitive cycles of 100%.
• Figure 11 Representation of electroluminescent device that uses laser sintered GO- EGaln ink at both sides.
• Figure 12 Representation of Electroluminescent device under 600% strain.
• Figure 13 Photographic representation of a Multi/pixel electroluminicent device composed of a light emiting composite sandwiched between electrically conductive and stretchable electrode rows and columns fabricated through laser sintering and laser patterning of GO-EGaln network.
• Figure 14 Representation of the results of an embodiment forcomparingthe electrical conductance and optical transparency of various technologies of the state of the art compared to this work/disclosure.
• Figure 15 Illustration of the results of an embodiment comparing the electrical conductance and maximum stretchability of various technologies of the state of the art compared to this work/disclosure.
• Figure 16 Illustration of the results of an embodiment where A) represents the synthesis of GO@EGaln nanocomposite.
• Figure 17 Representation of an embodiment of: A) Cyclic voltammogram of symmetric proposed supercapacitor for different scan rates. B) GCD graphs of soft-matter supercapacitor at different current densities for 3pm thickness. C) Bar graphs of areal specific capacitance obtained with various thickness of active materials. D) Capacitance retention subject to charging/discharging cycles for supercapacitors without strain for up to 1000 cycles. E) Capacitance retention subject to charging/discharging cycles for supercapacitors with multiple strain cycles (10 times, 30%) applied in 20 and 300 charging/discharging cycles for up to 500 cycles. F) An illustration of the mechanism occurring in a two-electrode system for a proposed supercapacitor during charging and discharging.
• Figure 18 Illustration of the results that demonstrates the electrochemical cycling process
• Figure 19 Representation of an embodiment containing: (Left) Schematic of a wirelessly chargeable supercapacitorthat combines an energy harvesting antenna, power cast transmitter, and electronic components; (Right) Optical images of the integrated supercapacitor and antenna in various deformed shapes.
• Figure 20 Representation of a memristor device fabricated using GO coated liquid metal droplets as MEMRISTOR composite, and as well for sintered electrode
• Figure 21 Representation of a Memristor Behaviour observed in GO coated liquid metal composite
• Figure 22 Representation of a pressure sensitive screen, composed of liquid metal filled transparent conductor.
• the present invention relates to a colloid comprising liquid metal droplets coated with graphene-based particles, wherein the liquid metal is gallium or a gallium alloy, and the graphene-based particles are selected from a list of graphene, graphene oxide, reduced graphene oxide, graphene quantum dots, carbon nanotubes, or combinations thereof.
• GO graphene oxide
• LM liquid metal
• GO@LM GO coated LM droplets
• GO@EGaln GO coated LM droplets
• rGO@LM reduced graphene oxide coated liquid metal
• the rGO@EGaln colloidal solution was obtained by sonicating ( ⁇ 20 min) 1 g of EGain into 20 ml of 0.4% (wt) graphene oxide water solution (Graphenea), with the intermediate addition of 1 ml of acetic acid (0.1 M).
• the GO/EGaln weight ratio is only 0.08.
• the solution was then mixed for 3 min at 2000 rpm using a planetary mixer (Thinky ARE-250). This results in a suspension of partially reduced GO coated EGain particles - Fig. 1 B).
• the solution was then spray coated over a substrate (i.e. glass or poly(methyl methacrylate), PMMA), using a spray gun.
• the sheet resistance of the spray coated samples, prior to the laser reduction was measured to be ⁇ (30 ⁇ 5) kQ/sq, which is ⁇ 3 orders of magnitude lower than that of spray coated EGain particles prior to the laser reduction.
• the spray coated sample was further reduced using a 20 W MOPA laser (JPT).
• rGO@EGaln refers to reduced graphene decorated EGain particle before laser processing. Note that during sonication the GO is partially reduced. To distinguish, it was used LrGO@EGaln to refer to the material after being laser reduced.
• the pulse width was increased from 6 to 250 ns; while the frequency was progressively decreased between 350 kHz and 40 kHz.
• No conductivity was measured for the films processed at or above 30 ns (pulse width), as the particles were likely ablated too harshly, with no significant material left.
• the 9 ns pulse width sample was able to provide the best trade-off between conductivity and transparency. It can be also noticed from Figs. 2 A-i) and 2 B-i) that, although the samples were manually spray coated, the final registered electrical resistance after laser reduction presents repeatable results.
• X-Ray diffraction (XRD) analysis in a range of 20 angle from ⁇ 7 to ⁇ 45 2 was performed on the as-sprayed films, with and without laser processing for better understanding the crystal phases of the synthesized composites.
• XRD X-Ray diffraction
• three types of samples were analyzed: one with no laser irradiation, which we refer to as a pristine sample, and two others processed at 50% and 75% laser powers, which correspond to a non-transparent and a semi-transparent sample, respectively.
• the results are shown in Fig. 3A).
• a sharp peak of GO in 20 ⁇ 9.89 2 is evident that related to the (0 0 1) crystal plane.
• the MOPA laser induces local high temperature on the spray coated films, that further induces crystallinity of GazOs.
• thermal sintering at >300 °C was reported to induce crystallinity of Gaz h in spray coated EGain nanoparticles, while laser sintered EGain remained amorphous [9],
• Fig. 3 B shows the general profile of the obtained Raman spectra of the investigated samples.
• Figs. 3C)-E) present the plots of IZD/IG and of ID/IG, as well as the full- width-at-half-width of the D band for the spectra of the studied samples as a function of the power of the laser. From Fig. 3C), one can see that the I 2D/IG ratio reaches a maximum for the laser power of ⁇ 60% indicating that the reduction of the GO increases with the power of the laser.
• the IZD/IG ratio start to decrease due to the effect of disorder (higher amounts of defects) increase, which tends to increase the intensity ratio.
• 60% power is the threshold in which samples start to show some transparency.
• the IZD/IG ratio reaches a nearly constant value, a result that combined with the data shown in Figs.3D) and 3E) seems to indicate that for laser powers greater than ca. 80% the degrees of reduction of the GO and of the disorder are not significantly different.
• the laser power here mentioned is only indicative and relative to the type of laser. Changing the laser type, lens, or other properties will change the power of the laser. For instance, using a lower or higher power laser also changes the required parameters, and these parameters should be adjusted according to the laser used.
• materials and methods referred above were used in order to make a flexible transparent conductor.
• another novel formulation, synthesis, deposition, and laser processing process that permits highly stretchable and highly conductive transparent conductors.
• This new synthesis is intentionally designed to be nonstable in the solvent, allowing for settling of a GO-EGaln network.
• this new GO-EGaln nanocomposite network can be collected as a highly concentrated matter, that can be applied through common thin-film application techniques.
• the key challenge during the process of creating EGain particles is to overcome its high surface tension, which drives adjacent droplets to combine.
• a physical barrier should be created on the surface of droplets. In most works this is performed by the naturally forming gallium oxide layer on the surface of the EGain droplets.
• the passivating oxide is stable [10]
• simply sonicating liquid metal in water leads to an unstable colloidal suspension, where suspensions usually precipitate within tens of minutes.
• Changing the medium to ethanol instead of water the formed EGain particles remained suspended up to several weeks.
• the high colloidal stability can be attributed to graphitic carbon coating formation during sonication.
• these stabilizing outer shells prevent the liquid droplets from coalescing, subsequent growth, and formation of large sediments of LMP at the bottom of the container. Additionally, the average particle diameters can be decreased by increasing the sonication time, however, high sonication times could form indium enriched nanoparticles due to the selective removal of gallium, driving phase transitions from liquid to solid.
• These dispersions can be used for fabrication of electronics by using spray or inkjet [1] printing methods, however, a high ratio of ethanol/EGaln should be used during sonication, which turns the ink deposition more challenging, specially to produce uniform films.
• Graphene Liquid Metal Network for the synthesis of Graphene Liquid Metal Network:
• the motivation lies in having a highly concentrated ink of the particles produced by sonication, which can be applied using rod coating/ thin film applicator or other similar techniques.
• the printing time will be significantly reduced, compared with the typical low concentration LMPs suspension.
• the synthesis method was formulated to avoid recoalescence of EGain particles into larger droplets, while permitting them to cluster into networks.
• the formulation was engineered to be able to produce an ink filled with spherical EGain particles that have liquid cores with a reduced thickness of gallium oxide shells.
• the gallium oxide shells are high aspect ratio sheets that bind to the liquid metal particles.
• these sheets can be cut into smaller sheets, it is generally preferred to maintain large sheets to form transparent conductors. This is because these large sheets determine how the liquid metal droplets self-assemble into percolating networks that leave holes that permit light transmission. That means that, as the liquid metal particles bind to these GO sheets, due to surface potentials or galvanic replacement, we can engineer the size of high aspect ratio sheets, so that after deposition of the film from this ink, they do not fully cover the whole surface of the substrate, and leave some holes for transmission of light.
• Encapsulation of EGain liquid metal nanoparticles (LMNPs) using graphene oxide (GO)[2, 10] and reduced GO (rGO) [ 11,12] have been used to change the LMNPs surface properties.
• GO graphene oxide
• rGO reduced GO
• 3 no such encapsulation occurs[ 3]
• the resultant processing cosolvent acidic exposes the bare metal of the LMPs by the dissolution of the gallium oxide shell [11,12], enabling the interaction of the GO sheets and LMPs.
• This process is governed by the positive Zeta potential of the LMNPs and the negatively charged GO sheets.
• GO tends to bond to the surface of LMPs to balance the charge.
• LMPs aggregation happens due to electrostatic interaction between several LMPs and larger GO sheets. Consequently, this results in formation of small clusters of LMPs mounted on high aspect ratio sheets of graphene oxide.
• the LMP acts as an anchoring point for exposed surface GO clusters.
• the required quantity of GO for gathering all the dispersed particles depends on the particles surface area, for example, when the same amount of LM is sonicated for 2 h instead of 10 min the required GO amount should be 7 times higher to provoke precipitation.
• the highly concentrated ink can be separated by removing the excess ethanol from the top of the flask.
• This provides advantages over low viscosity inks with liquid metal EGain droplets that should be applied using spray coating or similar.
• ethanol with the combination of acidic PH in the GO dispersion, play an important role to avoid Ga oxidation, and GO coating.
• other carbon products such as graphene quantum dots, carbon particles, or tubes may be as well used to replace the GO.
• the concentrated GO-EGaln network is then applied over a transparent elastic polymer such as Styrene-isoprene block copolymers or PDMS, using a thin-film applicator or a rod.
• a transparent elastic polymer such as Styrene-isoprene block copolymers or PDMS
• the amount of GO has a significant role in changing the properties of the composite both before, and after laser processing. GO improves mechanical and chemical properties of the nano particles. But excessive GO can reduce the conductivity of the samples. [0095] Afterdrying, it was used a MOPA (master oscillator power amplifier) laserwith Infrared wavelength to "activate" the ink. A rectangle (20x50mm) was hatched with a line spacing of 0.01mm using 20% power. The resistance of the sample after laser sintering is ⁇ 4Q. This is over 100 times of improvement compared to the previous formulation disclosed in this patent that had an electrical resistance of over 5000.
• MOPA master oscillator power amplifier
• FIG. 4 shows the summary of the process, from synthesis, deposition, and laser processing. After laser sintering, the ink self-assembles into percolating networks of EGain.
• Figure 5 shows SEM imaging comparing laser processing on Liquid metal nano particles without (top), and with graphene oxide decoration (Bottom). As can be seen, without GO the resulting device covers the surface which blocks the light transmission.
• Figure 6 shows schematics of the GO@EGaln network after deposition, and after laser processing. As can be seen, the partially reduced GO sheets act as guidelines for attachment of EGain droplets. When the laser scans the electrode, these EGain droplets coalescence into conductive lines, that occupy less volume compared to the sample prior to laser processing. Therefore, they leave empty spots that permit the light transmittance. Note that the same doesn't happen in absence of GO.
• Figure 6B shows an optical image of 3 electrodes, in which the GO amount was increased (from I to III), resulting in increased transparency.
• Figure 7 shows the resulting film of laser sintered EGAIN droplets without GO which is non-transparent (bottom), and a film of GO-EGaln deposited over a transparent substrate (middle), which is slightly transparent and non-conductive or very poorly conductive (kiloO- megaO) range depending on the GO concentration and film thickness.
• Top image shows the same film after laser processing, which is both transparent and highly conductive ( ⁇ 10O).
• Figure 8 shows the optical transparency of a laser sintered sample ( ⁇ 55-70% transmittance), and another electrode laser sintered and laser patterned to honeycomb structure ( ⁇ 90% transmittance). Laser patterning can increase the transmittance by selectively removing materials from the film. However, for most applications it is not necessary.
• Figure 9 shows an example of conductive semi-transparent device and the electromechanical characterization of the sample.
• the sample maintains its high electrical conductivity even when subject to large mechanical strains.
• the transparent conductor withstands 1300% of strain, and its electrical resistance remains below 10O even at 150% of strain.
• Figure 10 shows 5000 strain cycles of 100%. The sample is able to maintain a stable behavior even at this harsh condition.
• Figure 11 shows an example of a stretchable electroluminescence device in which both sides of the conductor are GO-EGaln ink.
• the middle layer includes a composite from an elastic material and electroluminescent powder.
• the top and bottom layer are composed of the same GO-EGaln ink.
• This configuration functions without the addition of a dielectric layer with high dielectric constant, which is common in electroluminescent devices. Therefore, the fabrication is simpler.
• the electroluminescent light can be seen from both sides of the electroluminescent device equally.
• Figure 12 shows an electroluminescent device under extreme strain conditions.
• Figure 13 shows a multi-pixel electroluminescent device composed of conductive rows and column electrodes made with GO-EGaln network and laser sintered and laser patterned using the techniques previously disclosed.
• Figure 14 and 15 show the optical transmittance, electrical resistance, and strain tolerance of transparent conductors made by this method compared to previous works, that demonstrates a clear and significant improvement over the state of the art.
• the current invention permits improving significantly electrical conductivity, and maximum strain tolerance of transparent conductors.
• liquid metal provides better strain tolerance due to its fluidic nature.
• Graphene oxide sheets act as guidelines for liquid metal droplets. Liquid metal droplets selectively bind to these sheets, and therefore they do not spread all over the surface, permitting slight transmittance of light. Laser sintering, further combines these particles to more compact form, creating additional spaces that increase light transmittance.
• Liquid metal droplets without GO coating are as well smearing to touch.
• the GO@EGaln as well improved the mechanical resistance of the particles to rupture, and improve the smearing behaviour.
• high performance, EGain-based SCs and batteries can be formed by using GO coated EGain nano particles (NPs).
• Thin-film electrodes made by this composite has extremely higher chemical stability, compared to the EGalnNPs without GO. This allows for the first time exposing EGalnNPs the use of EGalnNPs as energy storage electrodes that are stable, in the presence of highly acidic or alkaline electrolytes.
• a facile, rapid, low-cost, and scalable fabrication technique based on single step laser processing of GO@EGaln. This allows fabrication of conductive interdigitated geometries from a precoated film in a few minutes.
• IR Infrared Laser
• GO-coated EGain nanodroplets were first synthesized by sonication of lg bulk EGain in 20 ml solution of water based GO solution. It is known from the literature that the stability of EGain nanodroplets is dependent to their ultrathin ( ⁇ 3nm) Ga?O3 shell (Fig. 16B-i). Through fiber laser radiation, we can eliminate the GazOs shell , for a significant improvement in conductivity (Fig 16B-ii). Unfortunately, neither the EGalnNPs, nor the laser sintered LM scaffolds are stable when exposed to a highly alkaline solution.
• FIG. 16B-i and ii show that few seconds after exposure to a drop of 6M KOH aqueous solution, LM droplets/ scaffolds dewed from the surface, and aggregate into balk LM and therefore the background of the coated glass becomes visible.
• the film with GO encapsulated EGain composite stays intact after exposure to the same 6M KOH aqueous solution (Fig. 16B-iii, iv)
• Figures 16C-i and ii show schematically the role of the GO sheets in protecting EGain from chemical corrosion.
• a simple manual spray coating gun to form the GO@EGaln thin film over various substrates on a hotplate.
• a IR MOPA laser (1064 nm) was used, both for patterning of the desired geometry through full ablation of the coated material from the film (e.g. formation of the interdigitated architecture), and for further reduction of the GO layers into reduced graphene oxide (rGO).
• laser treatment can improve surface area (Fig. 16D) and energy storage capacity, but even without the laser reduction the device functions.
• laser reduction can be as well performed by other wavelengths and other types of lasers, such as COz laser. Laser reduction further decreased the sheet resistance from ⁇ 30KO/n to ⁇ lKQ/n.
• the soft-matter supercapacitor can be produced from pre-coated films in a few minutes through simultaneous laser reduction and patterning (ablation).
• the film itself contains a highly stretchable Ag-EGaln-SIS (styreneisoprene block copolymers)[16] as a first current collector (CC), followed by a Carbon Black- SIS (CB-SIS) film as a second CC. Both are applied by a thin-film applicator and the binder-free rGO@EGaln nanocomposite is applied through spray coating.
• Figure 16F demonstrates an example of a thin-film SC produced with this technique, showing that it can be stretched, bent, twisted or rolled.
• cyclic voltammetry was used in order to study the electrochemical behaviour of two-electrode symmetric rGO@EGaln SCs in presence of 6M KOH hydrogel electrolyte.
• CV curves on rGO@EGaln were listed at a potential window of 0-2 V with scan rates of 10-200 mV s" 1 .
• Redox peaks in the CV plots of the rGO@EGaln//rGO@EGaln SC are related to Faradaic redox reactions, and indicates the pseudocapacitive behavior of the SC. Additionally, the overall form of the CV graphs remain nearly unchanged during the increase in the scan rate.
• Fig. 17B shows the galvanostatic charge/discharge (GCD) plots of SC at various current densities and in the potential window range from 0 to 2 V.
• GCD galvanostatic charge/discharge
• Figure 17B inset demonstrates the changes of the areal capacitances in different current densities, ranging from 1.2 F/cm 2 for 300pA/cm 2 charge/discharge current to 85 mF/cm 2 for 3 mA/cm 2 .
• the areal-specific capacitance is increased when decreasing the current densities. Note that these results are all based on a SC with an electrode thickness of 3pm.
• Fig. 17C demonstrates the areal-specific capacitance, for various electrode thickness, ranging from ⁇ 0.5pm to ⁇ 15pm, for a discharge current density of ImA/cm 2 .
• Figure 17D demonstrates the ratio of the areal capacitance to the initial capacitance as a function of the number of cycles.
• the capacitor shows cycling stability, retaining ⁇ 98.4% of their initial capacitance after 1000 charging/discharging cycles at 3 mA/cm 2 .
• Insets show a zoom window from four cycles at beginning (after 3 hours) and at the end of measurement (after 32 hours).
• Figure 17E shows the SC behaviour when subject to 30% mechanical strain.
• Figure 17F schematically shows the electrochemical reaction during charging/discharging in each of the electrodes.
• the redox reaction is non- spontaneous and is activated by the supplied electrical energy, which initiates the reaction. Therefore, right after the fabrication of the SC, we perform a one-time activation step, to form the required metal Ions for creation of the potential difference between the electrodes.
• the KOH is converted to K + and OH- ions that move towards the electrode with the opposite charge (pH ⁇ 14).
• Ga 2+ + 3H 2 O GaOl ⁇ + 6H + + e ⁇ E a “ 1.868 - 0.3546 p rH + 0.0591 log o ⁇ [ G a a 0 2+].
• Figure 18 demonstrates the electrochemical cycling process.
• Figure 18 represents A) Diagram of a supercapacitor obtained during charging and discharging (marked points represent sampling locations). B) Images of SEM in different stages, as shown in the above diagram. Insert) BSE images in the same locations of SEM.
• Figure 18 shows the that the results seem to indicate that indium is migrating out of the EGain droplets during the charging process.
• the reason for the plateau at 0.5 volts is related to the elimination of the protective layer of gallium oxide (GazOs) in some of the particles, which allows contact between the electrolyte and the oxide-free liquid metal, thus resulting in formation of gallium ions (GaO3 3 and Ga 2+ ) and indium oxide (InzOs) particles.
• the elimination of GazCh layer at 0.5V is consistent with a previous work that investigated switchable surface activity of liquid metal [14],
• Figure 19 shows an integrated patch composed of a dipole antenna for far-field energy harvesting, which is coupled to an RF to DC (P1110B RF) board for converting the energy to a constant DC voltage and GO@EGaln super capacitors for energy.
• the circuit is on a soft and stretchable thin-film SIS elastomer substrate.
• all circuit components i.e. antenna, electrical interconnect, and supercapacitors were patterned rapidly from the same coated film. We first charged the supercapacitor, using a transmitter antenna, and then used the stored energy in the SC to light an LED.
• a memristor and pressure sensitive device based on go coated liquid metal composite shows Memristor behaviour.
• a CO2 laser to only partially sinter the composite.
• This step permits to make a composite that has memory and sensing devices.
• the top electrode shown in Figure 19 is fully sintered using an IR laser to make a highly conductive electrode, interfacing the memristor composite.
• Figure 20 shows the memristor behaviour of the device.
• this composite is a pressure sensitive film, whose electrical conductivity improves, when a pressure is applied.
• Figure 22 shows a transparent pressure sensitive electrode made by laser processing and patterning GO-EGaln network. Thisfilm is applied over a mobile phone screen to make a transparent pressure sensor which permits taking into account the pressure applied by the user, as an input for games or other programs.

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Wood Science & Technology (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Medicinal Chemistry (AREA)
• Health & Medical Sciences (AREA)
• Polymers & Plastics (AREA)
• Inorganic Chemistry (AREA)
• Carbon And Carbon Compounds (AREA)
• Paints Or Removers (AREA)
• Inks, Pencil-Leads, Or Crayons (AREA)
• Exposure Of Semiconductors, Excluding Electron Or Ion Beam Exposure (AREA)
• Conductive Materials (AREA)
• Manufacturing Of Electric Cables (AREA)
• Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)
• Pigments, Carbon Blacks, Or Wood Stains (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

Family

ID=86604095

Family Applications (1)

Country Status (5)

Cited By (2)

Families Citing this family (1)

• 2023
  • 2023-04-26 WO PCT/IB2023/054321 patent/WO2023209608A1/en not_active Ceased
  • 2023-04-26 EP EP23726601.0A patent/EP4514908A1/en active Pending
  • 2023-04-26 JP JP2024563741A patent/JP2025519017A/ja active Pending
  • 2023-04-26 US US18/860,738 patent/US20250333614A1/en active Pending
  • 2023-04-26 KR KR1020247038105A patent/KR20250006897A/ko active Pending

Non-Patent Citations (17)

Also Published As

Similar Documents

Legal Events