WO2023091324A1

WO2023091324A1 - Pulsed-laser sintering of ink-based electronics

Info

Publication number: WO2023091324A1
Application number: PCT/US2022/049123
Authority: WO
Inventors: Ying Liu; Ying Zheng
Original assignee: Corning Incorporated
Priority date: 2021-11-22
Filing date: 2022-11-07
Publication date: 2023-05-25
Also published as: TW202339876A

Abstract

Methods, systems, devices, and apparatuses are described. A material including metallic nanoparticles (e.g., an ink including silver nanoparticles) may be sintered using a pulsed light source with a relatively short pulse length (e.g., a picosecond laser) and relatively high repetition rate (e.g., greater than 100 kilohertz). The sintered material may be uniformly sintered through a full thickness of the material (e.g., 1 micrometer or more). In some examples, the material may be deposited on a substrate using various printing techniques, and the material may be sintered by directly applying light from the light source to the material. Additionally or alternatively, the material may be sintered by transmitting the light through the substrate. In some cases, the material may be consolidated (e.g., via evaporation) prior to sintering, and the sintering process may use some pattern (e.g., a raster pattern) for applying the light from the pulsed light source to the material.

Description

PULSED-LASER SINTERING OF INK-BASED ELECTRONICS

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Serial No.: 63/281,879, filed on November 22, 2021, the content of which is relied upon and incorporated herein by reference.

FIELD OF TECHNOLOGY

[0002] The present disclosure relates generally to sintering conductive materials, and more specifically to pulsed-laser sintering of ink-based electronics.

BACKGROUND

[0003] Various technologies have designs that rely on flexible, printed electronics. For example, displays (e.g., flexible displays, tiled displays), wearable devices, electronic textiles (e.g., smart clothing), photovoltaic devices, medical devices, Internet of Things (loT) devices, and other types of devices may incorporate electronics (e.g., transistors, capacitors, coils, resistors) that are printed on a substrate. Printed electronics may be fabricated by printing one or more inks (e.g., metallic inks) on the substrate using various techniques including, for example, inkjet printing, screen printing, aerosol jet printing, and other methods. Printed electronics may provide cost-effective and lightweight circuitry for various technologies that can be integrated into new and existing designs.

SUMMARY

[0004] The methods, apparatus, and devices of this disclosure each have several new and innovative aspects. This summary provides some examples of these new and innovative aspects, but the disclosure may include new and innovative aspects not included in this summary.

[0005] The described techniques relate to improved methods, systems, devices, and apparatuses that support pulsed-laser sintering of ink-based electronics. For example, a material, such as a material including metallic nanoparticles (e.g., an ink including silver nanoparticles), may be deposited on an optically transmissive substrate, and the material may be sintered using a laser, such as an ultrafast laser (e.g., a picosecond laser), with a relatively high repetition rate (e.g., greater than about 100 kilohertz (kHz)). As used herein, an optically transmissive substrate is a substrate that transmits at least about 80% of incident light over a range from about 400 nanometers to about 2000 nanometers when measured with an optical power meeter, for example that transmits at least about 85% of incident light, or that transmits at least about 90% of incident light over a wavelength range from about 400 nanometers to about 2000 nanometers. In some examples, the material may be consolidated (e.g., via evaporation) prior to sintering, and the material may be sintered by applying light output by the ultrafast laser from one or more directions (e.g., through the substrate, directly on the material). Further, the light output by the ultrafast laser may be applied to the material using some pattern (e.g., a raster pattern) for efficiently sintering the material. The sintering techniques described herein may result in printed electronics (e.g., electrodes or other electrical components) having improved electrical performance, such as relatively reduced electrical resistivity, while reducing or avoiding thermal damage to the substrate and other components during the sintering process. Sintering materials using a picosecond laser, as one example, may enable approximately uniform sintering of relatively thick electronics (e.g., having a thickness of about 1 micrometer (pm) or greater) that may have relatively complex geometries. For instance, the low-temperature sintering techniques described herein may result in printed electronics being sintered through the full thickness of the material, while providing precise sintering for materials having various geometries, resulting in electrical components with enhanced performance, among other benefits.

[0006] Accordingly, in a first aspect, a method is disclosed comprising depositing a material comprising a plurality of metallic nanoparticles on a first surface of a substrate and sintering through a full thickness of the deposited material using light output from a pulsed laser source, wherein the full thickness of the material after sintering is at least 1 micrometer.

[0007] In a second aspect, the pulsed laser source may comprise a picosecond laser, wherein the light output from the picosecond laser has a wavelength between about 700 nanometers and about 1100 nanometers, a pulse duration of the picosecond laser is less than about 10 picoseconds, and a repetition rate of the picosecond laser is between about 100 kilohertz and about 1000 kilohertz

[0008] In a third aspect, the method may comprise evaporating, before sintering the material according to any one of the first or second aspects, a portion of the material deposited on the substrate using one or more heat sources, wherein the portion of the material comprises a solvent material.

[0009] In a fourth aspect, a temperature of the substrate of the third aspect may be less than or equal to about 150 degrees Celsius while evaporating the portion of the material. [0010] In a fifth aspect, sintering the material of any one of the first through the fourth aspects may comprise applying the light output from the pulsed laser source from one or more directions facing the first surface of the substrate.

[0011] In a sixth aspect, the substrate of any one of the first through the fifth aspect may comprise an optically transmissive substrate, and sintering the material comprises applying the light output from the pulsed laser source through a second surface of the substrate opposite the first surface and through a volume of the substrate.

[0012] In a seventh aspect, sintering the material of any one of the first through the sixth aspects may comprise applying the light output from the pulsed laser source to the material in a raster pattern.

[0013] In an eighth aspect, the material of any one of the first aspect through the seventh aspect may be deposited using one or more aerosol-type printing procedures.

[0014] In a ninth aspect, a temperature of the substrate of any one of the first through the eighth aspect may change by less than about 5 degrees Celsius while sintering the material.

[0015] In a tenth aspect, the material of any one of the first through the ninth aspect deposited on the first surface may be between about 25 micrometers and about 75 micrometers in width, and the full thickness may be between about 1 micrometer and about 10 micrometers.

[0016] In an eleventh aspect, an electronic device is disclosed comprising a substrate and a sintered material comprising a plurality of metallic nanoparticles deposited on a first surface of the substrate, wherein a full thickness of the sintered material is sintered by light output from a pulsed laser source, the full thickness of the sintered material being at least 1 micrometer, and a line resistivity of the sintered material is between about 3. OX and 20X of the resistivity of a bulk material that is the same as a material of the plurality of metallic nanoparticles.

[0017] In a twelfth aspect, the sintered material of the eleventh aspect may comprise a solvent material that has been partially evaporated.

[0018] In a thirteenth aspect, the sintered material of the eleventh or the twelfth aspect deposited on the first surface further may comprise at least one of a solvent material or an adhesive material.

[0019] In a fourteenth aspect, the plurality of metallic nanoparticles of any one of the eleventh through the thirteenth aspect may comprise silver nanoparticles.

[0020] In a fifteenth aspect, the sintered material of any one of the eleventh aspect through the fourteenth aspect may comprise an electrode.

[0021] In a sixteenth aspect, a method is described comprising depositing an ink comprising silver nanoparticles and one or more solvents on a surface of a substrate, evaporating a portion of the one or more solvents using one or more heat sources, a temperature of the substrate not exceeding 150 degrees Celsius while evaporating the portion of the one or more solvents and sintering through a full thickness of the silver nanoparticles using light output from a picosecond laser operating at a repetition rate of at least 100 kilohertz, wherein the full thickness of the silver nanoparticles is at least 1 micrometer after sintering.

[0022] In a seventeenth aspect, the light output from the picosecond laser of the sixteenth aspect may have a pulse duration less than about 10 picoseconds, a wavelength between about 1000 nanometers and about 1100 nanometers, and an average power between about 0.1 watt and about 10 watts.

[0023] In an eighteenth aspect, sintering the silver nanoparticles of the sixteenth or the seventeenth aspect may comprise scanning the silver nanoparticles in a raster pattern with the light output from the picosecond laser at a scanning speed of about 100 millimeters per second. [0024] In a nineteenth aspect, the method of the eighteenth aspect may further comprise modifying a position of the substrate relative to the picosecond laser at a speed between about 1 millimeter per second and 5 millimeters per second while scanning the silver nanoparticles. [0025] In a twentieth aspect, the substrate of any one of the sixteenth aspect to the nineteenth aspect may transmit light at a same wavelength as the light output from the picosecond laser and sintering the silver nanoparticles comprises scanning the silver nanoparticles with the light output by the picosecond laser through a volume of the substrate.

[0026] Additional features and advantages of the aspects disclosed herein will be set forth in the detailed description that follows, and in part will be clear to those skilled in the art from that description or recognized by practicing the aspects described herein, including the detailed description which follows, the claims, as well as the appended drawings. It is to be understood that both the foregoing general description and the following detailed description present aspects intended to provide an overview or framework for understanding the nature and character of the aspects disclosed herein. The accompanying drawings are included to provide further understanding and are incorporated into and constitute a part of this specification. The drawings illustrate various aspects of the disclosure, and together with the description explain the principles and operations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 illustrates an example of an apparatus that supports pulsed-laser sintering of inkbased electronics in accordance with aspects of the present disclosure; [0028] FIG. 2 illustrates an example of a system that supports pulsed-laser sintering of inkbased electronics in accordance with aspects of the present disclosure;

[0029] FIG. 3 illustrates an example of a system that supports pulsed-laser sintering of inkbased electronics in accordance with aspects of the present disclosure;

[0030] FIGS. 4A and 4B illustrate examples of a sintering process and a cross-section of a sintered material that support pulsed-laser sintering of ink-based electronics in accordance with aspects of the present disclosure; and

[0031] FIG. 5 shows a flowchart that supports pulsed-laser sintering of ink-based electronics in accordance with aspects of the present disclosure.

DETAILED DESCRIPTION

[0032] Printed electronics may be used across various types of devices and technologies, including, for example, displays (e.g., flexible displays, tiled displays), wearable devices, electronic textiles (e.g., smart clothing), photovoltaic devices, medical devices, Internet of Things (loT) devices, and other types of devices and components thereof. As an example, a tiled display may include light emitting diodes (LEDs) (e.g., micro LEDs that are less than about 100 micrometers (pm) in size) for multiple self-illuminating pixels of the display, providing enhanced contrast and improved image quality compared to some other displays, among other advantages. To power the LEDs, printed electronics (e.g., electrodes) may be used to complete connections between the LEDs and one or more other components of the display. In some cases, the electrodes may have a complex geometry to support a reduced form factor (e.g., a small distance between respective pixels) of the display and its components.

[0033] Printed electronics may refer to one or more electronic components, such as electrodes, transistors, lines, coils, capacitors, resistors, etc., that are printed on a substrate using various printing procedures. For example, an ink including one or more conductive materials (e.g., metallic materials) may be printed on a substrate using inkjet printing, aerosol printing, screen printing, or the like. The printed ink may be sintered to generate a conductive electronic component. Here, sintering may refer to the application of thermal energy (e.g., heat) and/or pressure to a material to coalesce components of that material (e.g., particles, nanoparticles, microparticles) into a solid or porous mass. For instance, sintering a material including metallic nanoparticles may provide for a solid or porous metallic material that is capable of conduction, where the metallic nanoparticles may be at least partially melted during the sintering process. Sintering may also occur via inter-particulate surface necking (e.g., in addition to or instead of full melting of particles).

[0034] Various sintering techniques, including thermal sintering, intense pulsed light (IPL) sintering, laser sintering, electrical sintering, chemical sintering, and plasma sintering may be used for sintering various materials (e.g., including metallic nanoparticles). Thermal sintering may include subjecting a material and a substrate on which the material is printed to increased temperatures (e.g., in an oven that is about 150 degrees Celsius (°C) or more) for some duration. Laser sintering, which may include ultrafast laser sintering (e.g., sintering using an ultrafast pulsed laser having pulses that are picoseconds in duration, nanoseconds in duration, femtoseconds induration), may have various advantages to achieve selective and rapid thermal heating of a material, while resulting in less thermal damage to a substrate or surrounding materials, or both. For instance, with ultrafast-laser sintering, formation of localized hot spots due to enhanced electromagnetic fields generated at the particle junctions may heat the particles of the material to enable the sintering.

[0035] In some examples, however, some sintering techniques may have deficiencies that result in ineffective sintering or undesirable effects on the material, the substrate, on other components, or combinations thereof. For example, sintering using a femtosecond laser may only be effectively used to fully sinter thin materials (e.g., about 350 nanometers (nm) or less, about 1 pm or less). In some examples, femtosecond laser sintering may not be capable of fully sintering (e.g., through a full thickness) materials that are at least 1 pm thick. Further, due to a limited thermal penetration depth and a porous structure of the material, electrical performance of the material sintered using a femtosecond laser may be limited by particle density and fdm thickness. On the other hand, a continuous-wave (CW) or long-pulsed laser may sinter the material by partial or full melting, but such techniques may also result in heat buildup and damage to the substrate on which the material is deposited, making such approaches less desirable.

[0036] The techniques described herein provide enhanced sintering techniques using a pulsed laser source with a high repetition rate. Specifically, the described techniques provide for sintering of printed electronics (e.g., electrodes or other components) from a material (e.g., including metallic nanoparticles) using a picosecond laser operating with a repetition rate greater than about 100 kilohertz (kHz), which may enable approximately uniform sintering through a full thickness of the material (e.g., about 1 micrometer (pm) or greater in thickness). Such techniques may provide for printed electronics with enhanced electrical performance (e.g., relatively low resistivity) while also avoiding or minimizing thermal damage to the substrate and/or other components. In some examples, the material may be sintered from one or more directions, such as applying an output of the picosecond laser directly to the material and/or applying the output of the picosecond laser to a side of the substrate (e.g., a side opposite to where the material is deposited) so that the laser output sinters the material after being transmitted through a volume of the substrate. In some examples, the material may be condensed after it is deposited on the substrate, where one or more techniques may be used to evaporate at least a portion of solvents from the material deposited on the surface of the substrate (e.g., in some examples at least part of the solvents may be present after evaporation). In any case, the described techniques may provide for enhanced low-temperature sintering of ink-based materials that result in printed electronics with improved conductive properties.

[0037] Aspects of the disclosure are initially described in the context of an apparatus that includes one or more printed electronics sintered using a pulsed laser scanning at a high repetition rate. Aspects of the disclosure are further illustrated by and described with reference to systems configured for sintering materials. Additional aspects are then described with reference to a sintering pattern using a pulsed leaser, micrographs showing sintered materials, and flow charts.

[0038] This description provides examples, and is not intended to limit the scope, applicability or configuration of the principles described herein. Rather, the ensuing description will provide those skilled in the art with an enabling description for implementing various aspects of the principles described herein. As can be understood by one skilled in the art, various changes may be made in the function and arrangement of elements without departing from the application.

[0039] It should be appreciated by a person skilled in the art that one or more aspects of the disclosure may be implemented in a system to additionally or alternatively solve other problems than those described herein. Further, aspects of the disclosure may provide technical improvements to other different systems or processes as described herein. However, the description and appended drawings only include example technical improvements resulting from implementing aspects of the disclosure, and accordingly do not represent all of the technical improvements provided within the scope of the claims.

[0040] FIG. 1 illustrates an example of an apparatus (e.g., an electronic device) 100 that supports pulsed-laser sintering of ink-based electronics in accordance with aspects of the present disclosure. For instance, the apparatus 100 may be an example of an apparatus that includes one or more printed electronics that are sintered using a picosecond laser scanning at a high pulse rate (e.g., greater than about 100 kHz). In some examples, the apparatus 100 may be an example of a micro LED tile of a tiled display. The apparatus 100 described with reference to FIG. 1, however, is provided for illustrative purposes only, and other apparatuses and devices, or components thereof, may include some examples of printed electronics that are sintered in accordance with the described techniques. Thus, the examples described with respect to the apparatus 100 should not be considered limiting to the scope of the claims and the disclosure.

[0041] In the example of FIG. 1, the apparatus 100 may include one or more glass tiles 105 (e.g., a glass tile 105-a and a glass tile 105-b) that may each include one or more electrodes 110 (e.g., an electrode 110-a and an electrode 110-b). The glass tiles 105 are an example of a substrate (e.g., a glass substrate, an optically transmissive substrate). In some aspects, the glass tile 105 may include an aluminosilicate glass material, an alkali-aluminosilicate glass material, an aluminoborosilicate glass material, an alkali-aluminoborosilicate glass material, a soda line glass material, a borosilicate glass material, an alkali-borosilicate glass material, or other types of glass materials. Each glass tile 105 may include one or more pads 115 (e.g., electric pads including a copper material, a gold material, a silver material, or the like) and/or a pixel component 120 that includes, for example, a set of one or more LEDs 125 (e.g., micro LEDs). [0042] The apparatus 100 may be a component of or portion of a flat-panel display (e.g., a micro LED display) that provides enhanced resolution and small pixel pitch (e.g., small spacing between the pixel component 120-a and the pixel component 120-b). As such, the apparatus may include a plurality of LEDs 125, such as microscopic LEDs 125, that may self-illuminate per pixel component 120 (e.g., a display pixel). With its own light source, each LED may turn on or off, providing enhanced contrast and limited light bleed on surrounding pixels. Compared to other display technologies, such as organic LED (OLED) displays, an inorganic material (e.g., gallium nitride) used may enable the individual LEDs 125 (e.g., red-green-blue (RGB) LEDs) to operate brighter and longer. Due to these and other advantages of micro LED displays, the apparatus 100 may be included in various types of technologies and devices, such as digital signage, smartwatches, wireless devices (e.g., smartphones), tiled televisions, computer monitors, and other displays, as well as vehicle interior displays, among other examples.

[0043] To power the LED 125 while enabling a seamless design (e.g., minimizing the distance between the glass tiles 105 and therefore minimizing the distance between the pixel component 120-a and the pixel component 120-b), the electrodes 110 may be configured to be relatively thin while also enabling an electrical connection from a front surface of a glass tile 105 to a back surface of the glass tile 105. For example, the electrode 110-a may be configured (e.g., shaped) to provide an electronic coupling of the pixel component 120-a on one surface of the glass tile 105-ato circuitry or other components on another surface of the glass tile 105-a (e.g., via the one or more pads 115). In some aspects, the electrode 110-a and electrode 110-b may be referred to as a wrap-around electrode that wraps around an edge of a substrate, or some other terminology.

[0044] Each of the electrodes 110 is an example of a printed electronic. In such cases, a material (e.g., an ink) may be printed onto a substrate and sintered to produce the electrodes 110. Each electrode 110 may be a sintered material including, for example, metallic nanoparticles. For instance, the electrodes 110 may be produced from one or more metallic inks (e.g., silver inks, gold inks), which in some examples may provide for increased conductivity (e.g., compared to polymer-based materials). In such cases, the material (e.g., including one or more noble metals) may be dispersed in solvents as nanoparticles, enabling sintering processes with increased thermodynamic efficiency. In other examples, non-noble metals, such as copper, may be printed in a precursor form and/or be sintered in an inert environment (e.g., to avoid or reduce oxidation). Comparatively, silver-based inks may be inert, highly conductive, and relatively inexpensive compared to other metals. In some cases, silver nanoparticle inks may provide enhanced control for the dimensions and geometry of the electrodes 110 (e.g., as compared to silver precursor inks). Thus, the electrodes 110 may be produced from silver inks or inks including some other metallic materials. Additionally or alternatively, the electrodes 110 may include one or more other conductive materials, such as a noble metal (e.g., a metallic material that is resistant to oxidation and corrosion, which may include copper, gold, silver, among other examples).

[0045] Prior to sintering the electrodes 110, various techniques may be used for applying the electrode material (e.g., the metallic ink used to fabricate an electrode 110) on a glass tile 105, including aerosol printing, screen printing, Gravure printing and inkjet printing. Sintering the material deposited on a glass tile 105 may be a process that ensures the electronic properties of the components (e.g., the electrodes 110). As such, techniques that enable precise control over the material being sintered may enhance the efficiencies of the sintering process. For example, the electrodes 110 may have a complex geometry, and sintering techniques that are configured to accommodate this geometry may be desirable.

[0046] In some examples, sintering may be performed using a thermal treatment (e.g., thermal sintering), where the material deposited on the substrate may be sintered, for example, in an oven or using some other heat source that heats both the substrate and the material. Other different sintering processes, such as those using an oven, however, may be performed at high temperatures (e.g., about 150 °C or greater, about 200 degrees °C or greater), which may subject the substrate (and other components) to thermal exposure, and resulting damage, from the heating. More specifically, the glass tile 105 with the deposited material to form an electrode 110 may be subjected to increased temperatures for some duration of time during the sintering process, potentially causing damage (e.g., warping) to the glass tile 105. Additionally or alternatively, if one or more components (e.g., color filters or others) are deposited on the glass tile 105 prior to sintering, high heat applied during the sintering process may potentially cause damage to those components as well.

[0047] As such, it may be desirable to sinter the material used to form the electrodes 110 at lower temperatures. For example, subjecting the substrate to temperatures less than about 200 °C may avoid or reduce potential damage to the substrate. Similarly, subjecting the substrate (and other corresponding components) to temperatures less than about 150 °C may protect those components during sintering. Reducing the temperature for other different thermal sintering processes (e.g., those using an oven or other radiative heat source) to avoid damage to the substrate or other components, however, may result in decreased performance of the sintered materials (e.g., the electrodes 110). For example, sintering a material at lower temperatures using thermal sintering techniques (e.g., where the material and the substrate are subjected to heat), a line resistivity of the sintered material may increase after being sintered for some amount of time at 150 °C (e.g., as compared to when the electrode is sintered at 200 °C). As an example, line resistivity may increase more than 30% when a material is sintered using an oven at 150°C compared to being sintered using an oven at 200°C. Line resistivity is , „ . .. . cross-sectional area of the line denned as: line resistance X - - l -engt —h of — th —e l -ine . Additionally . ,■ using oven sintering & during other different techniques, even at reduced temperatures, may heat the substrate and any corresponding components and such thermal sintering techniques may result in thermal damage during the sintering process.

[0048] Other sintering techniques may include IPL sintering, laser sintering, electrical sintering, chemical sintering, and plasma sintering. Among these techniques, laser sintering may have advantages to achieve selective thermal heating with less thermal damage to the substrate or surrounding material (e.g., other than the material to be sintered). In ultrafast laser sintering, for example, formation of hot spots due to enhanced electromagnetic fields at particle junctions may heat the particles effectively. Sintering may take place by inter-particular surface necking in addition to melting of particles. In some cases, however, due to limited thermal penetration depth and a porous structure, the achieved electrical performance of the sintered material may be limited by particle density and film thickness. CW and long-pulsed laser techniques may sinter inks efficiently by partial or full melting, but such techniques may inflict heat buildup and damage to the glass tile 105. Therefore, alternative low-temperature and selective sintering methods may be desirable to minimize thermal load on the substrate, while also avoiding mechanical or thermal degradation of heat sensitive components integrated alongside the electrodes 110 (or other similar printed electronics).

[0049] As described herein, techniques for sintering the material used to form the electrodes 110 (e.g., including metal nanoparticles) may include the use of a pulsed light source (e.g., a picosecond laser) operating at a high repetition rate (e.g., greater than about 100 kHz) to solve deficiencies with other different sintering techniques. For example, the described low- temperature sintering techniques may avoid or minimize thermal damage to a substrate (e.g., the glass tile 105), while also enabling enhanced electrical performance of the sintered material. As such, particular aspects of the subject matter described herein may be implemented to realize one or more advantages. For example, the described sintering techniques may be used to produce uniformly in-depth sintered nanoparticle-based electrodes 110 having a thickness over about 1 pm, and the line resistivity of the electrode 110 may be, for example, about 3.5X the resistivity of bulk silver. Moreover, sintering using the pulsed laser source with a high repetition rate may provide for a low-temperature sintering process, where a substrate temperature may increase by only a few degrees (e.g., 2-3 °C) above ambient temperature during laser sintering. In addition, the substrate temperature may not be greater than 150 °C during the sintering process, avoiding damage to the substrate and/or other components of the apparatus 100.

[0050] FIG. 2 illustrates an example of a system 200 that supports pulsed-laser sintering of ink-based electronics in accordance with aspects of the present disclosure. For example, the system 200 may support techniques for selective sintering of materials including one or more inks with metal micro/nano-sized particles using a pulsed laser scanning at a high pulse rate. [0051] The system 200 may include various components that are configured for directing light to one or more surfaces of a substrate and used for sintering a material 210 that has been printed on the substrate 205. For example, the system 200 may include a light source 215 (e.g., a pulsed light source) that is configured to output light for sintering the material on the surface of the substrate 205. In some examples, one or more optical components of the system 200 may be used to modify the light output by the light source 215. For example, the system 200 may further include a waveplate 220, a beam splitter 225, a beam expander 230, one or more mirrors 235, and a scanner 240. In some examples, the substrate 205 may be supported by one or more components of the system 200, including a stage 255, a platform 260, and a vacuum chuck 265. The system 200 may, in some examples, include a camera 270.

[0052] The substrate 205 is an optically transmissive substrate (e.g., a substrate that enables the transmission of light at various wavelengths). For example, the substrate 205 may be optically transmissive to one or more wavelengths of light output by the light source 215 such that electromagnetic radiation from the light source 215 passes through the substrate 205. For instance, the transmittance of the substrate 205 may be greater than some percentage (e.g., greater than about 80 percent, greater than about 85 percent, or greater than about 90 percent) for normal incident light of a wavelength between about 400 nm and about 2400 nm. In other examples, at least a portion of the light output by the light source 215 may be transmitted through the substrate 205. In any case, the transmissivity of the substrate 205 may enable the material to be sintered by light from the light source 215 that is transmitted through the substrate 205. The substrate 205 may comprise a glass material including, for example, an aluminosilicate glass material, an alkali-aluminosilicate glass material, an aluminoborosilicate glass material, an alkali-aluminoborosilicate glass material, a soda line glass material, a borosilicate glass material, an alkali-borosilicate glass material, or other types of glass materials. In other examples, the substrate 205 may be another type of material or multiple materials. In some aspects, the substrate 205 may be a glass tile 105 described with reference to FIG. 1. The material 210 deposited on the substrate 205 may include a nanoparticle material (e.g., a nanoparticle ink) that includes particles, such as metallic particles, to be sintered.

[0053] The material 210 deposited on (e.g., printed on) the surface of the substrate 205 comprises metallic particles. In some cases, the material 210 may include one or more solvents. The particles of the material 210 may be nanoparticles, microparticles, nanowires, or any combination thereof. An average particle size may be about 100 nm or a different (e.g., smaller or larger) size. In some examples, the solvents may include one or more stabilizers for the dispersion of the particles. The solvent may in some cases include an adhesive promoter for the adhesion of the material 210 to the substrate 205. In some examples, the material 210 may be or include one or more metallic inks (e.g., silver inks, gold inks). In some cases, the material (e.g., including one or more noble metals) may be dispersed in solvents as nanoparticles, enabling sintering processes with increased thermodynamic efficiency. In other examples, the material 210 may include one or more non-noble metals (e.g., metallic materials that are resistant to oxidation and corrosion), that may be printed on the surface of the substrate 205 in a precursor form and/or be sintered an inert environment (e.g., to avoid or reduce oxidation). Additionally or alternatively, the material 210 may include one or more other conductive materials, such as a noble metal (e.g., copper, ruthenium, rhodium, palladium, platinum, gold, silver, osmium, iridium). In some examples, the material 210 may be an example of an electrode 110 described with reference to FIG. 1.

[0054] The light source 215 may be an example of a picosecond pulsed laser that is configured to operate at some wavelength of light, Z. The light source 215 may generate optical power in multiple pulses (e.g., bursts) with some repetition rate. Each laser beam pulse may include a burst of multiple sub-pulses, and a duration of a sub-pulse may be some number of nanoseconds in duration, some number of picoseconds in duration, some number of femtoseconds in duration, among other example durations. As one example, the light source 215 may be configured to operate using a pulse duration of about 10 picoseconds, an operating frequency of about 800 kHz, a wavelength of about 1.03 pm, a beam diameter of about 10 millimeters (mm), an average power of about 3 watts (W), and a laser pulse energy of 3.75 microjoules ( j). In other examples, the light source 215 may be configured to operate using a pulse duration less than about 10 picoseconds, an operating frequency between about 700 nanometers and about 1100 nanometers, a beam diameter between about 5 mm and 15 mm, an average power between about 0.5 W and 6 W, and a laser pulse energy between about 3 pj and 4 pj. The light source 215 may be a mode-locked laser, a Q-switching laser, a pulsed-pumping laser, among other examples, that generate a pulsed output (e.g., a non-continuous output). The light source 215, however, may be an example of another type of laser or light source not mentioned herein, but the examples described herein should not be considered limiting to the scope covered by the claims or the disclosure.

[0055] In some aspects, the wavelength of the light source 215 may be configured for sintering the material deposited on the surface of the substrate 205. For instance, the wavelength, Z. of the light source 215 may be based on a material of the substrate 205 such that the substrate 205 is substantially transparent to the laser light generated by the light source 215 (e.g., the substrate 205 may not absorb any light output by the light source at the wavelength Z). In some examples, the wavelength of the light source 215 may be about 1030 nm. In other examples, the wavelength of the light source 215 may be between about 700 nm and about 1100 nm. The system 200 may additionally or alternatively include a different number of (e.g., more) light sources 215 than illustrated in the system 200, which may provide for additional flexibility and configuration of the system 200, thereby enhancing an ability to efficiently sinter the material 210 deposited on the substrate 205.

[0056] An output of the light source 215 may be an example of a Gaussian beam. A Gaussian beam profile describes a laser beam having a beam profile that symmetrically decreases as the distance from the center of the laser beam cross-section increases, which may be described by a Gaussian function. In other examples, the output of the light source 215 may be a laser beam having a top hat beam profde (which may also be referred to as a flat top beam profde, tophat beam profile, top-hat beam profile, or other similar terminology) that has a constant profile through the cross-section of the laser beam. A laser beam with a top-hat beam profile may be formed (e.g., through beam shaping using one or more optical components) by a Gaussian beam. In some examples, the output of the light source 215 may be modified by the waveplate 220. For example, the waveplate may comprise a half-wave plate that modifies a polarization state of the output of the light source 215. In such cases, the output of the light source 215 may be linearly polarized after being transmitted by the waveplate 220. Other types of wave plates or optical components may be used to modify or adjust various properties of the light output by the light source 215. In some examples, light output from the waveplate 220 may be modified by the beam splitter 225. The beam splitter 225 may split the incident light into multiple beams.

[0057] The beam expander 230 may further modify light output by the beam splitter 225, where a beam diameter of the light may be modified (e.g., increased). As an example, the beam expander 230 may increase a diameter of the light output by the light source 215 (e.g., that is transmitted through one or more other optical components, including the waveplate 220 and the beam splitter 225). In some examples, the diameter of light that is transmitted by beam expander 230 may be about 14 mm or some other diameter. In some cases, the beam expander 230 (and the corresponding diameter of the light output by the beam expander 230) may be configured based on the material to be sintered by the system 200, or based on one or more other components of the system 200, or any combination thereof. One or more mirrors 235 may be configured to modify a direction of light (e.g., an expanded laser beam) output by the beam expander 230. As an example, the mirror 235 may direct light from the beam expander 230 to one or more other optical components, including the scanner 240.

[0058] The scanner 240 may be a galvanometer scanner (e.g., a galvo scan head). The scanner 240 may, for example, be a computer-controllable scanning component capable of deflecting and positioning of light from the mirror 235. The scanner 240 may include a set of mirrors that may be steered in various ways so as to control a path of a beam 245 (e.g., a laser beam) output by the scanner 240. For instance, the scanner 240 may be configured to modify a path of the beam 245 in accordance with a pattern (e.g., a raster pattern) when the beam 245 is used to sinter the material 210 on the substrate 205. In some examples, the scanner 240 may use a transformation of beam directivity in different dimensions through the use of multiple (e.g., two) scanning mirrors. Further, the beam 245 may be focused on the substrate 205 (and the material 210) using a lens 250 (e.g., an F-theta focusing lens or other type of focusing lens). In some examples, the lens 250 may have a focal length (e.g., a 45 mm focal length) configured to sinter the material on the surface of the substrate 205. The scanner 240 may be another type of scanner (e.g., a polygon laser scanner) that may be used to sinter the material 210 deposited on the surface of the substrate 205 in accordance with a predetermined pattern.

[0059] The stage 255 may be an example of a X-Y-Z linear stage configured to modify a position of the substrate 205 (e.g., for sintering the material 210 deposited on the surface of the substrate 205). As an example, the stage 255 may be an example of a computer-controlled X- Y-Z motion stage that may be configured for precise movement of the substrate 205 (e.g., during, before, and after the sintering process). In some examples, the stage 255 may be moved (e.g., vertically) a predetermined distance (e.g., 240 pm) from the focal plane of the lens 250, which may enable the beam 245 to have some configured size (e.g., a 55 pm diameter) on the surface of the substrate 205 for sintering the material 210. The beam 245 may be a defocused beam based on a position of the stage 255 or a position of the scanner 240, or both.

[0060] The platform 260 may be an example of a tilt platform that may be used to modify the position of the substrate 205. For example, the platform 260 may be a multi-axis tilt platform that is configured to provide tilt, alignment, and/or rotation adjustments during the sintering process. The vacuum chuck 265 may be a vacuum clamping system that secures the substrate 205 to the platform 260 and the stage 255. Other components or chucks may be used to secure the substrate to the platform 260 and the stage 255.

[0061] The system 200 may include the camera 270 to enable viewing of the material 210 and the sintering process performed by the system 200. Additionally or alternatively, other devices or components (e.g., a thermocouple) may be included in the system 200 to enable various measurements of the sintering process to monitor, for example, a temperature of the substrate 205.

[0062] Thus, the system 200 may perform selective laser sintering, such as picosecond laser sintering, of electrodes (e.g., wrap-around electrodes) and other printed electronics on the substrate 205 (e.g., glass). In such cases, the material 210 may be printed on the substrate 205 prior to sintering. The substrate 205 may then be fixed on the stage 255 (e.g., a motorized rotation stage) to enable rotation of the substrate 205, for example, to sinter the material 210 from one or multiple directions (e.g., top, edge, and bottom sintering). Such techniques may enable selective sintering of the material 210, which may be a printed electronic device having a complex geometry. [0063] As an illustrative example of the operation of the system 200, the material 210 including silver nanoparticles may be deposited on the surface of the substrate 205 prior to sintering using one or more printing techniques (e.g., inkjet printing, screen printing, aerosol jet printing). In such cases, one or multiple lines of the material 210 may be applied (printed, deposited) as an ink with predetermined dimensions (e.g., about 50 pm wide and about 5 pm thick).

[0064] In some examples, the lines of the material 210 may be consolidated (e.g., preconsolidated, dried, evaporated), for example, by applying heat to material 210 prior to sintering, during sintering, or both. For instance, the material 210 may include one or more other materials, such as solvent materials (e.g., organic solvent materials), adhesive materials, or other types of materials. The solvent materials may separate nanoparticles from each other, preventing interaction between particles of the material 210. An example of a composition of the material 210 (e.g., a silver nanoparticle ink) is provided by Table 1:

Table 1 - Ink Composition

[0065] Heat may be applied to the material 210 to enable the evaporation of one or more solvent materials (e.g., propylene glycol monomethyl ether or others), consolidating the material 210 prior to sintering. Consolidation may remove at least a majority of the solvent or other materials from the printed material 210 (e.g., while some amounts of these solvents and other materials may remain after consolidation in some examples). In examples where the solvents are not fully removed, the remaining solvent(s) may function as a binder between the substrate 205 and the nanoparticles of the material 210. Additionally or alternatively, some of the remaining solvent(s) may function as a stabilizer that may be removed during sintering of the material 210.

[0066] To consolidate (e.g., evaporate, dry), the material 210 and the substrate 205 may be placed in a heat source (not shown) (e.g., an oven, a radiative heat source, other types heat sources) for a predetermined time duration. As an example, the material 210 may be consolidated by placing the substrate 205 and the material 210 in an oven at 150 °C or lower temperatures for 30 minutes, and some portion of the material 210 may be evaporated by the heat. In some cases, the material 210 may be consolidated for longer or shorter amounts of time (e.g., from a few minutes to an hour or even multiple hours). In some examples, the consolidation of the material may be performed in a temperature-controlled environment. Consolidating the material 210 may modify light absorption properties of the material 210. For example, consolidating the material for one hour at 150 °C may result in a higher light absorption at some wavelengths (e.g., a 30% greater light absorption at about 1 pm wavelength).

[0067] Additionally or alternatively, the material 210 may be consolidated using another light source (e.g., a laser) that is applied to the material 210. In some examples, the other light source may be configured to operate at a lower power than light source 215. In this example, the material 210 may therefore include silver nanoparticles as well as some amounts of one or more solvent materials (e.g., both prior to and after evaporation of solvents). Although Table 1 shows examples of the composition of the material 210, as described herein, the material 210 may include other types of materials, and the examples described herein should not be considered limiting to the scope of the claims or the disclosure.

[0068] The material 210 may then be sintered using a pulsed laser, such as a pulsed picosecond laser (e.g., the light source 215) operating at a wavelength, such as a wavelength of about 1030 nm, and a pulse rate, such as a pulse rate of about 800 kHz, and using on-the-fly rapid scanning, which may result in a sintered material 210 with reduced electrical resistivity. The wavelength of the light source 215 during sintering may be between about 600 nm and about 2 pm, a pulse rate of the light source 215 may be between about 100 kHz and about 1000 kHz, and a pulse duration of the light source 215 may be between about 1 picosecond and about 1 nanosecond. In some examples, a numerical aperture for light output by the light source may be between about 0.02 and about 0.3. Further, the light source 215 may output light that is modified by one or more components of the system 200 (e.g., the waveplate 220, the beam splitter 225, the beam expander 230, one or more mirrors 235, the scanner 240, the lens 250, or any combination thereof) to generate the beam 245 that is used to sinter the material 210 deposited on the surface of the substrate 205.

[0069] The sintering of the material 210 may include scanning the material 210 from a predetermined direction relative to a surface of the substrate 205 (e.g., top, bottom, through the substrate, or combinations thereof). In some cases, based on a configuration and operation of the scanner 240 and one or more of the platform 260 or the stage 255, the material 210 may be scanned in accordance with a predetermined pattern, such as a raster pattern. Additionally or alternatively, the platform 260 or the stage 255, or both may be held stationary, and the scanner 240 may be configured to scan the material 210 in accordance with the predetermined pattern. As an example, an area (e.g., a 1 mm x 6 mm area) of the material 210 may be sintered by the beam 245 using a raster pattern. In such cases, the stage 255 may move (e.g., continuously) at a predetermined rate (e.g., between about 1 mm/s and about 3 mm/s), while the scanner 240 may raster along an axis in accordance with predetermined scanning parameters (e.g., a processing width (e.g., a width of an area where the material 210 is sintered) of about 1 mm, a speed of about 100 meter/second). The beam 245 may therefore follow a triangle wave on the material 210, as described in further detail with respect to FIG. 4B. In some cases, the scanning (and sintering) of the material 210 may be performed at different (e.g., increased) speeds.

[0070] In some examples, a power of the light source 215 may be varied during sintering, for example, between 0.1 W and about 10 W or between about 0.6 W and about 3.5 W. In some cases, a power range of the light source 215 is associated with a beam size and off-focus distance (e.g., some distance away from a focal point of a laser beam). As such, the power range of the light source 215 may be modified in cases where the beam size and the off-focus distance are modified. In addition, pulse rate, laser beam diameter, and scan speed may be selected to yield a predetermined effective pulse number, N, (e.g., defined by A = ^-, where f is equal to the pulse rate of the light source 215, d is equal to a diameter of the beam 245, and V is equal to a scan speed (e.g., 1920 in the example of a 100 mm/s scanning speed), describing a high (e.g., 99.77%) pulse overlap during the sintering process. In some examples, the pulse rate of the light source 215 may be fixed or variable.

[0071] Laser scanning using a high pulse rate (e.g., greater than about 100 kHz) for the beam 245, heat accumulation and heat diffusion from adjacent areas on the surface of the substrate 205 (e.g., areas adjacent to the areas processed by the beam 245) may provide for decreased heating and cooling rates compared with other laser sintering techniques. The described techniques may therefore result in a lower temperature gradient over an entire processing volume, and a heat effect during sintering may be more uniform across the surface of the substrate 205 and through a thickness of the material 210. As such, the system 200 may support sintering of the material 210 through a full thickness of the material 210 (e.g., at least 1 pm in thickness).

[0072] Further, the sintering process may result in small temperature changes in the substrate 205. As an example, the sintering process using the system 200 may be performed at room temperature (23.7 °C), and a temperature of the substrate 205 may increase by a few degrees (e.g., between about 3 °C and about 4 °C). Such measurements of the substrate temperature may be obtained using, for example, a thermocouple or other device attached to the substrate 205 (e.g., on a surface of the substrate 205) and at a position near the material 210 (e.g., 2 mm away from the material 210). For example, a thermocouple may be adhered to (e.g., taped to) a surface of the substrate 205 adj acent to the material 210, and the thermocouple may be located at the same side as a laser processing area for sintering the material 210. The thermocouple may provide a local temperature measurement that corresponds to a temperature measurement of the substrate 205, for example, before, during, and after the sintering process. Thus, the described sintering techniques may provide for sintering of the material 210 with minimal temperature increases in the substrate 205, and the material 210 may likewise be sintered without subjecting the substrate 205 to high temperatures (e.g., 150 °C or higher). For example, a temperature of the substrate 205 during the sintering process may be between 20 °C and 100 °C.

[0073] Sintering the material 210 using the system 200 may also result in a sintered material 210 (e.g., an electrode) that has improved electrical performance. For example, the sintered material 210 may have a line resistivity about 3.5X the resistivity of bulk silver materials, which may be comparable to thermal sintering techniques (e.g., in a 200 °C oven), while also preventing damage to the substrate and/or other components through thermal effects. Put another way, the described techniques may produce a sintered material 210 that has electrical performance that may otherwise be achieved through other high-temperature sintering processes, but without subjecting the substrate 205 to temperatures above 150 °C.

[0074] Thus, the system 200 may support improved laser sintering, such as picosecond laser sintering, which may provide various advantages over other laser sintering techniques, including a uniformly in-depth sintered material 210 having a thickness over 1 pm, a line resistivity of about 3.5X the resistivity of bulk silver, small substrate temperature changes (e.g., 3-4 °C above ambient temperature) during the laser sintering process, preventing the substrate temperature from reaching 150 °C during the laser sintering process, and sintering of materials (e.g., wrap-around electrodes) having a complex geometry, among other advantages.

[0075] FIG. 3 illustrates an example of a system 300 that supports pulsed-laser sintering of ink-based electronics in accordance with aspects of the present disclosure. The system 300 is an example of the system 200 described with reference to FIG. 2. For instance, the system 300 may include a substrate 305 with a material 310 deposited on a surface of the substrate 305. The system 300 may further include a stage 320 (e.g., a rotational stage) configured to support the substrate 305 (e.g., during laser sintering). The system 300 may also include a beam 325 that is output by a light source (e.g., a light source 215 described with reference to FIG. 2). The substrate 305, the material 310, the stage 320, and the beam 325 may be examples of the respective components described with reference to FIGS. 1 and 2. For instance, the material 310 may be an example of a material including metallic nanoparticles (or nanoparticles of another conductive material) and the substrate 305 may be an example of an optically transmissive substrate (e.g., a glass material, an alkali-boroaluminosihcate material). Notably, one or more components of the system 300, have been omitted for the sake of brevity and ease of description. As such, the system 300 may include one or more other components that are not shown, and the system 300 supports the described techniques for sintering materials that include one or more inks with metal micro/nano-sized particles using a pulsed laser scanning at a relatively high repetition rate.

[0076] In some examples, the material 310 may be sintered from one or more different directions. For instance, other than directly sintering the material 310 from a direction opposite the surface of the substrate 305, the described techniques may also be used for back-side sintering (e.g., sintering the material 310 through another surface of the substrate 305). Such techniques may further minimize thermal impact on one or more components that may be located near the material 310 (e.g., on the same side as the material 310) on the substrate 305. Such techniques may also be used to sinter the particles of the material 310 at the glass interface (e.g., an interface where the material 310 and the substrate 305 meet). Such techniques may reduce contact resistance between the material 310 and the substrate 305. In any case, the stage 320 may be a rotational stage that is configured to rotate the substrate 305 (e.g., through 360 degrees).

[0077] As an example, the stage 320 may rotate the substrate 305 such that the beam 325 is applied to the material 310 through a volume of the substrate 305. Here, sintering may occur with light irradiated from the back side of the substrate 305 as illustrated, which may induce thermal melting of nanoparticles of the material 310 at an interface, resulting in a conductive network and reduced contact resistance (e.g., a resistance across a contact interface). In some case, a contact pad (e.g., an indium-tin oxide (ITO) contact pad, a contact pad including other materials) may be used at a contact layer between the substrate 305 and the material 310. That is, the contact pad may be deposited on the surface of the substrate 305 and the material (e.g., a silver ink) may then be deposited (e.g., printed) on top of the contact pad. In some examples, the described back-side sintering process (e.g., through a volume of the substrate 305) may be used to reduce conductivity between a contact pad (e.g., an ITO layer) and the substrate 305, which may utilize a heat accumulation effect caused by irradiation at the ITO layer from the beam 325 generated by a light source (e.g., a high-repetition rate picosecond laser).

[0078] As illustrated the stage 320 may enable rotation of the substrate 305 for example, to perform top, edge, and bottom sintering of the material 310. Such techniques may enable selective sintering of printed electronics having a complex geometry or design with resistivity comparable to about 3.4X the resistivity of the bulk metal. Further, picosecond laser processing with a high repetition rate (e.g., greater than about 100 kHz) may enable enhanced precision for sintering the material 310, which may further provide for repeatable and adjustable sintering of materials through a full thickness of the material (e.g., having a thickness of at least 1 pm, having a thickness of at least 2 pm, having a thickness of at least 5 pm, or the like). The system 300 may accordingly support low-temperature sintering without damaging the substrate 305 or other heat-sensitive components on the substrate 305.

[0079] FIGS. 4A and 4B illustrate examples of a sintering process 401 and a cross-section 402 of a sintered material that support pulsed-laser sintering of ink-based electronics in accordance with aspects of the present disclosure. The sintering process 401 illustrates a substrate 405 and a material 410 deposited on a surface of the substrate 405. In some examples, the substrate 405 may be the glass tile 105, the substrate 205, or the substrate 305, as described with reference to FIGS. 1, 2, and 3, respectively. Likewise, the material 410 may be the electrode 110, the material 210, or the material 310, as described with reference to FIGS. 1, 2, and 3, respectively. For instance, the material 410 may be a silver nanoparticle material deposited on a surface of the substrate 405, where the substrate may be an optically transmissive substrate (e.g., a glass material).

[0080] The material 410 may be deposited (e.g., in respective areas) on a surface of the substrate 405 using, for example, an aerosol printing system or other techniques. The material 410 may be printed on the substrate 405 using one or more patterns (e.g., micropattems). In the examples shown in FIG. 4A, the material 410 may be printed in multiple lines, but other patterns are possible. The material may comprise multiple electrodes (e.g., wrap around electrodes). In some cases, one or more dimensions of the material 410 may be configured to satisfy one or more parameters for a thickness, width, and length of each line including the material 410 that is printed on the substrate 405. A thickness of each line may be about 5 pm and the width of the material 410 may be about 50 pm. In other examples, the width of the material 410 may be between about 25 pm and 75 pm, and the thickness of the material 410 may be greater than 1 pm, for example, after consolidation, where some portion of the material 410 may be evaporated. For instance, the printed material 410 may be consolidated using one or more techniques for heating the material 410 (e.g., using an oven, using a laser) to evaporate one or more solvents from the material 410, and the thickness of the material 410 may refer to a thickness of the material 410 after it has been consolidated.

[0081] After the application of the material 410 to the surface of the substrate 405, the material may be sintered, for example, using a beam 425 generated by a pulsed light source (e.g., a picosecond laser configured with a high pulse rate (e.g., about 100 kHz or greater)). The beam 425 may accordingly be an example of a beam 325 described with reference to FIG. 3 or a beam 245 described with reference to FIG. 2. The sintering process may include scanning the material 410 from a predetermined direction relative to a surface of the substrate 405 (e.g., a direction facing the surface of the substrate 405 where the material 410 is deposited, a direction opposite the surface of the substrate and through a volume of the substrate 405).

[0082] The material 410 may be sintered in accordance with a pattern 430, such as a raster pattern. As an example, a processing area (e.g., a 1 mm x 6 mm area, an area where the beam 425 is incident on the material 410 and enables sintering of the material 410) of the material 410 may be sintered by the beam 425 using the pattern 430, where a stage holding the substrate 405 may move continuously at a predetermined rate (e.g., between about 1 mm/s and about 3 mm/s), while a scanner may raster the beam 425 along an axis in accordance with predetermined scanning parameters (e.g., a width of about 1 mm, a speed of about 100 meter/second). The beam 425 may follow a triangle wave on the material 410 as illustrated by the pattern 430. In some cases, the scanning (and sintering) of the material 410 may be performed at different (e.g., increased) speeds or using patterns different from the pattern 430. [0083] In some examples, the line overlap of the triangle wave illustrated by the pattern 430 may be between 72% and 91%. Here, the overlap may be based on a stage speed (e.g., a stage moving between 1 mm/s and 3 mm/s). In some examples, the processing area (the 1 mm x 6 mm processing area) may be used to apply the beam 425 to a full area of the material 410. During the scanning of the beam, a laser intensity may be at a lower level than a non-linear light absorbing threshold for the substrate 405. As such, energy from the beam 425 may be absorbed in the material 410 and not the substrate 405.

[0084] FIG. 4B illustrates a cross-section 402 of the sintered material 410 after sintering using the described techniques. The cross-section 402 may be an example of one of the lines including the material 410 printed on the substrate 405 and sintered in accordance with the pattern 430. As described herein, sintering of the material 410 is achieved by inter-particle connections and partial melting. The sintered material 410 may be porous as a result of the sintering. In the example shown by the cross-section 402, the sintered material 410 may be fully sintered through a thickness of at least 5 gm, and the sintered material 410 may be about 50 gm wide. The described sintering techniques may, however, be used to fully sinter materials that have different dimensions (e.g., between 1 gm and 10 gm thick). As such, by sintering the material 410 using a picosecond laser at a high pulse rate may provide advantages over other laser sintering techniques. For example, sintering using a femtosecond laser may not be capable of sintering materials that are 1 pm (or greater) in thickness. In particular, compared to shorter pulse duration laser sintering (e.g., femtosecond laser sintering), a picosecond laser enables uniform in-depth sintering of the material 410, where a morphology (e.g., a microstructure) of the material 410 is approximately the same through the full thickness of the material 410. Further, compared to longer pulse duration laser sintering (e.g., quasi-CW or CW laser sintering), the sintered material 410 may not be fully melted.

[0085] In some examples, the height and width of the sintered material 410 may change based on a power of the beam 425 used for sintering. As one example, using a high laser power (e.g., 2.5W or above), there may be a decrease for the width and height of the sintered material 410. When the material 410 is sintered at a lower power, the thickness profde may not change (e.g., compared to pre-sintering dimensions).

[0086] The electrical resistance of the sintered material 410 may be low based on the described techniques used to sinter the material 410. The electrical resistance of the sintered material 410 may be measured using a four-probe resistance measurement (which may be referred to as four- terminal sensing) or some other techniques. The resistivity of the sintered material may be calculated based on the resistance and the cross-sectional area of the material, as shown by the cross-section 402. A dimensionless parameter p may be calculated by dividing the calculated resistivity of the sintered material by a resistivity of the bulk material (e.g., a bulk material that corresponds to the particles in the material 410). In some cases, the line resistivity of the sintered material 410 may be about 3.4X or less than the resistivity of the bulk material. In other examples, the line resistivity of the sintered material 410 may be between about 3X and 20X the resistivity of the bulk material.

[0087] FIG. 5 shows a flow chart illustrating a method 500 that supports pulsed-laser sintering of ink-based electronics in accordance with aspects of the present disclosure. The operations of the method 500 may be implemented by a device or its components as described herein. For example, the operations of the method 500 may be performed by a device or system (e.g., a system 200 or a system 300 described with reference to FIGS. 2 and 3) configured to sinter a nanoparticle material. In some examples, the device may execute a set of instructions to control the functional elements of the device to perform the described functions. Additionally or alternatively, the device may perform aspects of the described functions using special-purpose hardware.

[0088] At 505, the method may include depositing, on a first surface of an optically transmissive substrate, a material including a plurality of metallic nanoparticles. The operations of 505 may be performed in accordance with examples as disclosed herein.

[0089] At 510, the method may include sintering the deposited material through a full thickness thereof using light output from a pulsed laser source, where the full thickness of the material after sintering is at least 1 pm. The operations of 510 may be performed in accordance with examples as disclosed herein.

[0090] In some examples, an apparatus as described herein may perform a method or methods, such as the method 500. The apparatus may include, features, circuitry, logic, means, or instructions (e.g., a non-transitory computer-readable medium storing instructions executable by a processor) for depositing a material including a plurality of metallic nanoparticles on a first surface of a substrate and sintering through a full thickness of the deposited material through using light output from a pulsed laser source, where the full thickness of the material after sintering is at least 1 pm.

[0091] In some examples of the method 500 and the apparatus described herein, the pulsed laser source is a picosecond laser, the light output from the picosecond laser has a wavelength between about 700 nm and about 1100 nm, a pulse duration of the picosecond laser is less than about 10 picoseconds, and a repetition rate of the picosecond laser is between about 100 kHz and about 1000 kHz.

[0092] In some examples of the method 500 and the apparatus described herein, the apparatus may include operations, features, circuitry, logic, means, or instructions for evaporating, before sintering the material, a portion of the material deposited on the substrate using one or more heat sources, where the portion of the material includes a solvent material. In some examples of the method 500 and the apparatus described herein, a temperature of the substrate may be less than or equal to about 150 degrees Celsius while evaporating the portion of the material.

[0093] In some examples of the method 500 and the apparatus described herein, the apparatus may include operations, features, circuitry, logic, means, or instructions for applying the light output from the pulsed laser source from one or more directions facing the first surface of the substrate.

[0094] In some examples of the method 500 and the apparatus described herein, the substrate may be an optically transmissive substrate, and the apparatus may include operations, features, circuitry, logic, means, or instructions for applying the light output from the pulsed laser source through a second surface of the substrate opposite the first surface and through a volume of the substrate.

[0095] In some examples of the method 500 and the apparatus described herein, the apparatus may include operations, features, circuitry, logic, means, or instructions for applying the light output from the pulsed laser source to the material in a raster pattern while the substrate is moved relative to the pulsed laser source.

[0096] In some examples of the method 500 and the apparatus described herein, a temperature of the substrate may change by less than about 5 degrees Celsius while sintering the material. In some examples of the method 500 and the apparatus described herein, the material deposited on the first surface is between about 20 pm and about 100 pm wide, and the full thickness is between about 1 pm and about 10 pm.

[0097] An electronic device is described. The electronic device may include an optically transmissive substrate and a sintered material including a plurality of nanoparticles deposited on a first surface of the optically transmissive substrate, where the sintered material is sintered through a full thickness of the sintered material by light output from a pulsed laser source, the full thickness of the sintered material being at least 1 pm, and a line resistivity of the sintered material is between about 3. OX and 20X of the resistivity of a bulk material that is the same as a material of the plurality of metallic nanoparticles.

[0098] In some examples of the electronic device, the sintered material further includes a solvent material that has been partially evaporated. In some examples of the electronic device, the sintered material deposited on the first surface further includes a solvent material or an adhesive material.

[0099] In some examples of the electronic device, the plurality of metallic nanoparticles includes silver nanoparticles. In some examples of the apparatus, the sintered material includes an electrode.

[0100] Another apparatus as described herein may perform another method or other methods. The apparatus may include, features, circuitry, logic, means, or instructions (e.g., a non- transitory computer-readable medium storing instructions executable by a processor) for depositing an ink comprising silver nanoparticles and one or more solvents on a surface of a substrate, evaporating a portion of the one or more solvents using one or more heat sources, a temperature of the substrate not exceeding 150 degrees Celsius while evaporating the portion of the one or more solvents, and sintering through a full thickness of the silver nanoparticles using light output from a picosecond laser operating at a repetition rate of at least 100 kilohertz, wherein the full thickness of the silver nanoparticles is at least 1 pm after sintering.

[0101] In some examples of the method 500 and the apparatus described herein, the light output from the picosecond laser has a pulse duration less than about 10 picoseconds, a wavelength between about 1000 nm and about 1100 nm, and an average power between about 0.1 watts (W) and about 10 W.

[0102] In some examples of the method 500 and the apparatus described herein, the apparatus may include operations, features, circuitry, logic, means, or instructions for scanning the silver nanoparticles in a raster pattern with the light output from the picosecond laser, the silver nanoparticles are scanned at a scanning speed of about 100 mm per seconds.

[0103] In some examples of the method 500 and the apparatus described herein, the apparatus may include operations, features, circuitry, logic, means, or instructions for modifying a position of the substrate relative to the picosecond laser while scanning the silver nanoparticles, the position of the substrate is modified at a speed between about 1 mm per second and 5 mm per second.

[0104] In some examples of the method 500 and the apparatus described herein, the substrate transmits light at a same wavelength as the light output from the picosecond laser, and sintering the silver nanoparticles comprises scanning the silver nanoparticles with the light output by the picosecond laser through a volume of the substrate.

[0105] It should be noted that these methods describe examples of implementations, and that the operations and the steps may be rearranged or otherwise modified such that other implementations are possible. In some examples, aspects from two or more of the methods may be combined. For example, aspects of each of the methods may include steps or aspects of the other methods, or other steps or techniques described herein. Thus, aspects of the disclosure may provide for consumer preference and maintenance interface.

[0106] The description set forth herein, in connection with the appended drawings, describes example configurations and does not represent all the examples that may be implemented or that are within the scope of the claims. The term “exemplary” used herein means “serving as an example, instance, or illustration,” and not “preferred” or “advantageous over other examples.” The detailed description includes specific details for the purpose of providing an understanding of the described techniques. These techniques, however, may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described examples. [0107] As used herein, the term “about” means that the modified characteristic (e.g., a verb or adjective modified by the term substantially) or a related aspect (e.g., related action or function), need not be absolute but is close enough to achieve the advantages of the characteristic or related aspect (e.g., related action or function).

[0108] In the appended figures, similar components or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If just the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.

[0109] The various illustrative blocks and modules described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a digital signal processor (DSP), a central processing unit (CPU), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general -purpose processor may be a microprocessor, but in the alternative, the processor may be any processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration). The functions of each unit may also be implemented, in whole or in part, with instructions embodied in a memory, formatted to be executed by one or more general or application-specific processors.

[0110] The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Other examples and implementations are within the scope of the disclosure and appended claims. For example, due to the nature of software, functions described herein can be implemented using software executed by a processor, hardware, firmware, hardwiring, or combinations of any of these. Features implementing functions may also be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations. Also, as used herein, including in the claims, “or” as used in a list of items (for example, a list of items prefaced by a phrase such as “at least one of’ or “one or more of’) indicates an inclusive list such that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C). Also, as used herein, the phrase “based on” shall not be construed as a reference to a closed set of conditions. For example, an exemplary step that is described as “based on condition A” may be based on both a condition A and a condition B without departing from the scope of the present disclosure. In other words, as used herein, the phrase “based on” shall be construed in the same manner as the phrase “based at least in part on.” [0111] Computer-readable media includes both non-transitory computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A non-transitory storage medium may be any available medium that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, non-transitory computer-readable media can comprise random-access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general -purpose or specialpurpose processor. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, include CD, laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media.

[0112] The description herein is provided to enable a person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not limited to the examples and designs described herein but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein.

Claims

What is claimed is:

1. A method of sintering ink-based electronics, comprising: depositing a material comprising a plurality of metallic nanoparticles on a first surface of a substrate; and sintering through a full thickness of the deposited material using light output from a pulsed laser source, wherein the full thickness of the material after sintering is at least 1 micrometer.

2. The method of claim 1, wherein the pulsed laser source comprises a picosecond laser, the light output from the picosecond laser has a wavelength between about 700 nanometers and about 1100 nanometers, a pulse duration of the picosecond laser is less than about 10 picoseconds, and a repetition rate of the picosecond laser is between about 100 kilohertz and about 1000 kilohertz.

3. The method of claim 1 or claim 2, further comprising evaporating, before sintering the material, a portion of the material deposited on the substrate using one or more heat sources, wherein the portion of the material comprises a solvent material.

4. The method of claim 3, wherein a temperature of the substrate is less than or equal to about 150 degrees Celsius while evaporating the portion of the material.

5. The method of any one of claims 1 to 4, wherein sintering the material comprises applying the light output from the pulsed laser source from one or more directions facing the first surface of the substrate.

6. The method of any one of claims 1 to 5, wherein the substrate comprises an optically transmissive substrate, and sintering the material comprises applying the light output from the pulsed laser source through a second surface of the substrate opposite the first surface and through a volume of the substrate.

7. The method of any one of claims 1 to 6, wherein sintering the material comprises applying the light output from the pulsed laser source to the material in a raster pattern.

8. The method of any one of claims 1 to 7, wherein the material is deposited using one or more aerosol-type printing procedures.

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9. The method of any one of claims 1 to 8, wherein a temperature of the substrate changes by less than about 5 degrees Celsius while sintering the material.

10. The method of any one of claims 1 to 9, wherein the material deposited on the first surface is between about 25 micrometers and about 75 micrometers in width, and the full thickness is between about 1 micrometer and about 10 micrometers.

11. An electronic device comprising: a substrate; and a sintered material comprising a plurality of metallic nanoparticles deposited on a first surface of the substrate, wherein a full thickness of the sintered material is sintered by light output from a pulsed laser source, the full thickness of the sintered material being at least 1 micrometer, and a line resistivity of the sintered material is between about 3. OX and 20X of a resistivity of a bulk material that is the same as a material of the plurality of metallic nanoparticles.

12. The electronic device of claim 11, wherein the sintered material comprises a solvent material that has been partially evaporated.

13. The electronic device of claim 11 or claim 12, wherein the sintered material deposited on the first surface further comprises at least one of a solvent material or an adhesive material.

14. The electronic device of any one of claims 11 to 13, wherein the plurality of metallic nanoparticles comprises silver nanoparticles.

15. The electronic device of any one of claims 11 to 14, wherein the sintered material comprises an electrode.

16. A method of sintering ink-based electronics, comprising: depositing an ink comprising silver nanoparticles and one or more solvents on a surface of a substrate; evaporating a portion of the one or more solvents using one or more heat sources, a temperature of the substrate not exceeding 150 degrees Celsius while evaporating the portion of the one or more solvents; and

30 sintering through a full thickness of the silver nanoparticles using light output from a picosecond laser operating at a repetition rate of at least 100 kilohertz, wherein the full thickness of the silver nanoparticles is at least 1 micrometer after sintering.

17. The method of claim 16, wherein the light output from the picosecond laser has a pulse duration less than about 10 picoseconds, a wavelength between about 1000 nanometers and about 1100 nanometers, and an average power between about 0.1 watt and about 10 watts.

18. The method of claim 16 or claim 17, wherein sintering the silver nanoparticles comprises scanning the silver nanoparticles in a raster pattern with the light output from the picosecond laser at a scanning speed of about 100 millimeters per second.

19. The method of claim 18, further comprising modifying a position of the substrate relative to the picosecond laser at a speed between about 1 millimeter per second and 5 millimeters per second while scanning the silver nanoparticles.

20. The method of any one of claims 16 to 19, wherein the substrate transmits light at a same wavelength as the light output from the picosecond laser and sintering the silver nanoparticles comprises scanning the silver nanoparticles with the light output by the picosecond laser through a volume of the substrate.