WO2020012454A1 - Procédé de fabrication dirigée de matériaux à l'aide d'ondes acoustiques - Google Patents

Procédé de fabrication dirigée de matériaux à l'aide d'ondes acoustiques Download PDF

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Publication number
WO2020012454A1
WO2020012454A1 PCT/IL2018/050739 IL2018050739W WO2020012454A1 WO 2020012454 A1 WO2020012454 A1 WO 2020012454A1 IL 2018050739 W IL2018050739 W IL 2018050739W WO 2020012454 A1 WO2020012454 A1 WO 2020012454A1
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Prior art keywords
solid
ssaw
acoustic wave
standing acoustic
reaction
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PCT/IL2018/050739
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English (en)
Inventor
Haim SAZAN
Silvia PIPERNO
Hagay SHPAISMAN
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Bar-Ilan University
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Priority to PCT/IL2018/050739 priority Critical patent/WO2020012454A1/fr
Publication of WO2020012454A1 publication Critical patent/WO2020012454A1/fr

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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/172—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using resonance effects
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
    • B01J19/10—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor employing sonic or ultrasonic vibrations
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/162—Selection of materials
    • G10K11/165—Particles in a matrix
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
    • B01J2219/0873—Materials to be treated
    • B01J2219/0879—Solid

Definitions

  • the present invention relates to methods for the directed fabrication of solid or semi-solid materials utilizing standing acoustic waves.
  • additive manufacturing also known as two or three-dimensional (2D or 3D) printing
  • 2D or 3D printing refers to a method used to produce a two or three-dimensional object, in which continuous layers of material are manipulated under the guidance of a computer program.
  • the final object may be obtained in various shapes, sizes, orientations, and geometries, utilizing different materials.
  • the main downside of the current 2D or 3D printing methods is that each one is adapted for a specific type of a material.
  • Stereolithography is suitable only for photopolymers
  • FDM Fused Deposition Modeling
  • thermoplastic materials such as polymers (metals and ceramics may be incorporated by the use of a binder, enabling the material to be used in a filament form)
  • DMLS Direct Metal Laser Sintering
  • Additional techniques developed in the last decades for the manipulation of materials include, inter alia , electric, optical, optoelectronic, magnetic, and acoustical tweezers techniques.
  • acoustic techniques such as the use of acoustic standing waves show great promise for their ability to affect existing particles.
  • a standing acoustic wave is a wave existing in a medium in which each point on the axis of the wave has an associated constant amplitude.
  • the locations at which the amplitude is at minimum are called nodes, while the locations where the amplitude is at maximum are called antinodes.
  • manipulation with standing surface acoustic waves shows promise as an emerging direction.
  • a suspended particle that is exposed to an ultrasound standing wave field may respond to the primary acoustic radiation force by transporting to specific locations along the wave (pressure nodes or pressure antinodes).
  • the primary acoustic radiation force acting on any particle in a SSAW field depends on the acoustic pressure, acoustic wavelength, volume of the particles, density of the particles, density of the suspending medium, compressibility of the particles, and compressibility of the suspending medium, and the distance between the particle and the pressure node.
  • SSAWs were used for manipulating and directing of polydimethylsiloxane (PDMS) particles flowing through a microfluidic channel, fabricated by standard lithography (Shi, Jinjie, et al. "Focusing microparticles in a microfluidic channel with standing surface acoustic waves (SSAW).” Lab on a Chip 8.2 (2008): 221-223).
  • the channel width was designed to cover only one pressure node such that particles were focused at that node when the SSAW was generated.
  • the motion of PDMS droplets was directed along separate microchannel paths at high volume flow rates using a surface acoustic wave device (Franke, Thomas, et al. "Surface acoustic wave (SAW) directed droplet flow in microfluidics for PDMS devices.” Lab on a Chip 9.18 (2009): 2625-2627).
  • SAW surface acoustic wave
  • US Patent No. 4,879,011 discloses a process for supporting a particulate material in a fluid medium by means of an ultrasonic standing wave, while a reaction is effected or controlled involving the material supported, for example with the fluid medium or other material contained in the medium.
  • the process has particular applications to biological reactions, such as fermentation, and to chromatography, as examples.
  • US Patent No. 9,458,450 discloses a system having improved trapping force for acoustophoresis, where the trapping force is improved by manipulation of the frequency of the ultrasonic transducer.
  • US Patent No. 5,840,241 discloses a process used to control the spacing and alignment of previously randomly distributed and randomly oriented loose fibrous elements in a fluid medium.
  • US Patent No. 4,743,361 discloses the separation of particles types from a mixed population of particles in a liquid, which is obtained in an ultrasonic wave produced by interference between the outputs from spaced ultrasonic sources.
  • US Patent No. 9,199,217 discloses a method of fabricating a material comprising the steps of suspending particles in a solidifiable fluid, generating at least one acoustic standing wave in the fluid, and solidifying the fluid so as to form the material to have the concentration profile of particles fixed in place.
  • standing acoustic waves in the additive manufacturing processes were used solely to manipulate and order preformed materials.
  • the present invention provides a method and device for the directed fabrication of solid and semi-solid materials, utilizing standing acoustic waves.
  • the method includes the steps of initiating and continuing a chemical reaction in a reaction medium, which is exposed to at least one standing acoustic wave.
  • the present invention is based in part on the unexpected discovery that standing acoustic waves can be used not only to manipulate and order preformed materials, but also to influence ongoing chemical reactions. Multiple types of various chemical reactions can be conducted under the influence of standing acoustic waves to provide directed material formation, as long as at least one product or intermediate product of said reaction has a positive or a negative contrast acoustic factor in respect to the medium in which it is suspended. It is to be emphasized that the method of the present invention requires that the reaction medium is exposed to the at least one standing acoustic wave prior to the formation of the at least one product or intermediate product.
  • the present invention provides a method for the directed fabrication of a solid or semi-solid material, comprising the steps of: providing a reaction medium comprising at least one reagent and a suspending medium; generating at least one standing acoustic wave; exposing the reaction medium to the at least one standing acoustic wave; initiating a chemical reaction in the reaction medium under said at least one standing acoustic wave, wherein at least one product or intermediate product of said chemical reaction has a non-zero acoustic contrast factor with respect to the suspending medium, so that the at least one product or intermediate product migrates to at least one pressure node or at least one pressure antinode of the at least one standing acoustic wave; and continuing the chemical reaction until a desired amount of the solid or semi-solid material is formed at the at least one pressure node or the at least one pressure antinode.
  • the at least one product or intermediate product comprises particles.
  • the at least one intermediate product comprises a nucleation site.
  • the chemical reaction is selected from the group consisting of polymerization, precipitation, sol-gel, combination reaction, replacement reaction, decomposition reaction and combinations thereof.
  • the polymerization is selected from the group consisting of emulsion polymerization, solution polymerization, suspension polymerization, step-growth polymerization and chain-growth polymerization. Each possibility represents a separate embodiment of the invention.
  • the at least one reagent is selected from the group consisting of an organic molecule, organometallic molecule, siloxane molecule, inorganic salt, inorganic acid, inorganic base, organic salt, organic acid, organic base, metallic ion and non- metallic ion.
  • an organic molecule organometallic molecule, siloxane molecule, inorganic salt, inorganic acid, inorganic base, organic salt, organic acid, organic base, metallic ion and non- metallic ion.
  • the suspending medium is selected from a gas or a liquid.
  • the liquid is selected from the group consisting of water, aqueous solution and organic solvent. Each possibility represents a separate embodiment of the invention.
  • the step of initiating a chemical reaction comprises controlling the reaction rate thereof. In some embodiments, the step of initiating the chemical reaction comprises supplying an initiator to the reaction medium. In certain embodiments, the initiator is selected from a chemical or a physical initiator.
  • the reaction medium comprises a substrate upon which the solid or semi-solid material is formed.
  • the chemical reaction is emulsion polymerization
  • the suspending medium comprises water
  • the product comprises a polymer, selected from the group consisting of: polydimethylsiloxane (PDMS), styrene-butadiene (SBR), polybutadiene, polychloroprene (neoprene), nitrile rubber, acrylic rubber, fluoroelastomer (FKM), polyvinyl chloride (PVC), polystyrene, poly(methyl methacrylate) (PMMA), acrylonitrile-butadiene-styrene terpolymer (ABS), polyvinylidene fluoride (PVDF), polyvinyl fluoride, polytetrafluoroethylene (PTFE), and polyaniline (PANI).
  • the polymer is PDMS.
  • the chemical reaction is precipitation
  • the suspending medium comprises water
  • the product is selected from the group consisting of titanium dioxide, gold, silver, chrome, copper, fluorapatite, zinc oxide, iron oxide, cadmium hydroxide, yttrium oxide and derivatives and combinations thereof.
  • the product comprises titanium dioxide
  • the at least one standing acoustic wave has a chosen wavelength, l, in the suspending medium.
  • the wavelength, l, of the standing acoustic wave is selected such that a chosen number of pressure nodes and/or pressure antinodes is generated.
  • the wavelength, l ranges from about 10 nm to about 10 m.
  • the at least one standing acoustic wave is generated by an acoustic transducer selected from the group consisting of: an acoustic resonator, electromagnetic acoustic transducer, a microphone, a magnetic induction based microphone, a flat diaphragm loudspeaker, a piezoelectric crystal, a mechanical vibrator and a shaped diaphragm loudspeaker.
  • an acoustic transducer selected from the group consisting of: an acoustic resonator, electromagnetic acoustic transducer, a microphone, a magnetic induction based microphone, a flat diaphragm loudspeaker, a piezoelectric crystal, a mechanical vibrator and a shaped diaphragm loudspeaker.
  • the reaction medium comprises a reaction vessel. According to some other embodiments, the reaction medium comprises a resonator cavity comprising at least one surface spaced from an opposing reflecting surface.
  • the method of the present invention further comprises generating a series of standing acoustic waves having a controlled constructive and destructive interference to create a pattern of pressure nodes and pressure antinodes in one or more dimensions.
  • the at least one standing acoustic wave is a surface standing acoustic wave (SSAW).
  • SSAW surface standing acoustic wave
  • generating the at least one SSAW comprises providing a surface configured to transmit acoustic waves and coupling at least one acoustic transducer to the surface.
  • said surface contacts the reaction medium.
  • said surface is a piezoelectric surface and the SSAW is generated by applying an altering electric field to interdigitated transducers (IDTs) that are deposited on said piezoelectric surface.
  • the SSAW is generated by an array of IDTs, comprising from 1 to 10000 pairs of IDTs.
  • the pair of IDTs has an acoustic aperture of from about 0.5 mm to about 2000 mm.
  • the step of generating the at least one SSAW comprises applying an RF signal of about 0.001 to about 5000 MHz to the pair of IDTs.
  • the step of generating the at least one SSAW comprises applying an RF signal of about 1 to about 500 Vpp (peak to peak voltage) to the pair of IDTs.
  • the method of the present invention is configured for the preparation of a solid or semi-solid material having a three-dimensional structure, wherein a first SSAW or a series of SSAWs are generated on a surface and further comprising the steps of: removing the formed material from said surface; generating a second SSAW or a series of SSAWs on said surface; and forming a three-dimensional solid or semi-solid material by combining the material formed under the first SSAW or series of SSAWs with the material formed under the second SSAW or series of SSAWs.
  • the three-dimensional structure comprises at least two layers of the formed material.
  • the combination of the material formed under the first SSAW or series of SSAWs with the material formed under the second SSAW or series of SSAWs is performed by the formation of physical and/or chemical bonds.
  • the step of generating a first SSAW or series of SSAWs on a surface further comprises a step of continuously extruding the formed material from said surface.
  • the method further comprises terminating the first SSAW or series of SSAWs and generating a second SSAW or series of SSAWs on said surface during the extrusion of the formed material.
  • the method of the present invention for the preparation of a solid or semi-solid material having a three-dimensional structure comprises generating a series of standing acoustic waves having a controlled constructive and destructive interference to create a pattern of pressure nodes in more than one dimension by a plurality of acoustic transducers.
  • the method further comprises a step of separating the formed solid or semi-solid material from the suspending medium.
  • a solid or semi-solid material fabricated by the method of the present invention as described in various embodiments hereinabove.
  • the material is selected from the group consisting of inorganic material, organic material, polymeric material, organometallic material, and composite or hybrid material. Each possibility represents a separate embodiment of the invention.
  • the structure of the material fabricated by the method of the present invention is selected from the group consisting of elongated structures, patterned structures, periodic structures, porous structures, symmetric structures and Chladni pattern structures. Each possibility represents a separate embodiment of the invention.
  • the material has a structure defined by the parameters of the at least one standing acoustic wave.
  • said parameters are selected from the group consisting of number of generated standing acoustic waves, number of pressure nodes and antinodes, position of pressure nodes and antinodes relative to the reaction medium, wavelength of the standing acoustic wave, wave phase, amplitude of the standing acoustic wave, and waveform of the standing acoustic wave.
  • Figure 1A schematically illustrates the device for directed fabrication of a solid or semi solid material, in accordance with some embodiments of the invention.
  • Figure IB schematically illustrates the cross-section of the device for directed fabrication of a solid or semi-solid material, in accordance with some embodiments of the invention.
  • Figure 2A represents a flowchart of the method for the multi-step fabrication of a three- dimensional material, according to some embodiments of the invention.
  • Figure 2B schematically represents one of the steps of said method using two pairs of IDTs and a moving unit.
  • Figure 2C schematically represents a position of acoustic transducers in the method for the one-step fabrication of a three-dimensional material, according to some embodiments of the invention.
  • Figure 3 depicts the bright-field microscope images of patterning of PDMS emulsion droplets at different concentration of a cross-linker (in situ).
  • Figures 4A-4C demonstrate the bright-field microscope images of polymerization of PDMS strips at different time periods: about 30 seconds after generating the SSAW (Figure 4A); 3 minutes after generating the SSAW ( Figure 4B); and 10 minutes after generating the SSAWs ( Figure 4C).
  • Figures 5A-5D depicts SEM images of PDMS emulsion droplets at different concentrations of Na 2 S0 4 salt: No salt (Figure 5A); 0.35% wt. salt (Figure 5B); 0.7% wt. salt ( Figure 5C); and 1.4% wt. salt ( Figure 5D).
  • Figure 6A represents influence of the SSAW intensity on the thickness of the polymerized material.
  • Figure 6B represents a profile (height) of polymerized strips, wherein the voltage applied to the IDTs is 20Vpp (peak to peak voltage).
  • Figure 7 represents a bright-field microscopy image of the two-layer PDMS structure prepared in a multi-step process.
  • Figures 8A-8B depict the Ti0 2 formation in a precipitation reaction.
  • Figure 8A demonstrates the comparative example of the Ti0 2 system without SSAWs, indicating a homogenous distribution.
  • Figure 8B demonstrates the directed formation of titanium dioxide after 6 minutes from the SSAW generation, indicating the formation of Ti0 2 wires.
  • Figures 9A-9B demonstrate SEM images of Ti0 2 strips formed under the SSAWs. The scale bar for both images is 2 pm.
  • Figure 9A depicts a dense structure; and
  • Figure 9B depicts a porous structure (part of a stripe that is about 15 pm in width).
  • the present invention relates to a unique method for directing chemical reactions using standing acoustic waves, leading to the formation of the products of these reactions into predefined 1D, 2D and/or 3D structures.
  • standing acoustic waves can be used to influence ongoing chemical reactions.
  • the present invention is based in part on an unexpected finding that standing acoustic waves can promote the formation of stable solid or semi-solid materials, when applied to a reaction medium in which a chemical reaction takes place.
  • acoustic forces can influence any system where there is a difference in compressibility and density between the formed material and the surrounding medium (i.e., difference in acoustic contrast).
  • At least one product or intermediate product of the chemical reaction has an acoustic contrast factor in respect to the medium in which it is suspended following its formation, which is non-zero.
  • the beneficial method of the invention utilizes standing acoustic waves not only to dictate the spatial distribution of materials but also to influence the mesoscopic structure thereof and the kinetics of the reaction.
  • Standing acoustic waves can be used for fabricating and/or printing predefined structures from various types of materials, such as, but not limited to, organic molecules, polymers, metals, ceramics, semi conductors, oxides or any combination thereof.
  • the present invention therefore provides a cost efficient and simple method for the fabrication of solid and semi-solid products based on a wide range of materials.
  • the fabrication method of the present invention is highly modular, and can be adapted for the fabrication of one-dimensional, two-dimensional, and three-dimensional structures.
  • One of the multiple advantages of the present method is that it can be used for a one- step (or simultaneous) fabrication of 3D structures in contrast to the currently available additive (or layer-by-layer) techniques.
  • the method of the present invention is easily scalable, and does not impose limits on the size of the printable area. The method according to the principles of the invention can, therefore, be used in fabrication of complex structures, including sensors, electronic devices, medical devices, plastics and various parts for a wide range of industries (including, inter alia , automotive, aerospace, and architecture).
  • the present invention provides a method for directed fabrication of a solid or semi-solid material, comprising the steps of: providing a reaction medium comprising at least one reagent and a suspending medium; generating at least one standing acoustic wave; exposing the reaction medium to the at least one standing acoustic wave; initiating a chemical reaction in the reaction medium under said at least one standing acoustic wave, wherein at least one product or intermediate product of said chemical reaction has a positive acoustic contrast factor or a negative acoustic contrast factor with respect to the suspending medium, so that the at least one product or intermediate product migrates to at least one pressure node or at least one pressure antinode of the at least one standing acoustic wave; and continuing the chemical reaction until a desired amount of the solid or semi-solid material is formed at the at least one pressure node or the at least one pressure antinode.
  • standing acoustic wave refers to a wave existing in a medium, in which each point on the axis of the wave has an associated constant amplitude.
  • acoustic is to be understood to encompass wavelengths ranging from about 20Hz to about lOGHz.
  • the terms“axis”,“longitudinal axis”,“longitudinal plane” and“direction” with respect to the standing acoustic wave are used interchangeably.
  • pressure node refers to a location along the longitudinal axis or plane of the wave at which the amplitude is at minimum.
  • pressure antinode refers to a location along the longitudinal axis or plane of the wave at which the amplitude is at maximum.
  • reaction medium refers to a medium, in which a chemical reaction takes place.
  • the reaction medium is a reaction vessel.
  • the non limiting examples of the reaction vessels useful in the methods of the present invention include a beaker, a microfluidic channel, a mixing vessel, a pressurized vessel, a reactor and a micro-reactor.
  • the reaction medium comprises a resonator cavity.
  • the resonator cavity has at least one surface spaced from an opposing reflecting surface.
  • the acoustic wave applied to the at least one surface is reflected from the corresponding reflecting surface to form a standing acoustic wave comprising spaced pressure nodes and antinodes.
  • the resonator cavity can comprise a fluid container having parallel walls, such as, for example, a cuvette.
  • the resonator cavity can be coupled to at least one acoustic transducer. In certain embodiments, two acoustic transducers are attached to the opposing sides of the resonator cavity.
  • the resonator cavity has more than one pair of opposing reflecting surfaces.
  • said pairs of opposing reflecting surfaces are orthogonal to each other.
  • each two opposing surfaces of the resonator cavity are reflecting surfaces.
  • the cuvette can include six acoustic transduces, wherein each acoustic transducer is attached to each of the six walls of the cuvette.
  • the resonator cavity can have various shapes selected from, but not limited to, cube, prism, pyramid, cylinder and sphere.
  • the prism or a pyramid-shaped resonator cavities can have polygonal cross-sections such as, but not limited to trigonal, cubic, rectangular, pentagonal, hexagonal, and octagonal cross-sections.
  • the term“cross-section”, as used herein, refers to a cross-section along the plane which is orthogonal to the opposing reflecting surfaces.
  • the reflective surfaces of the resonator cavity can be flat or curved, such as convex or concave. Each possibility represents a separate embodiment of the invention.
  • the opposing surfaces of the resonator cavity are parallel.
  • the angle between the opposing surfaces of the resonator cavity ranges between about 180° to about 5°.
  • suspending medium refers to a phase which surrounds the at least one reagent and/or at least one product or intermediate product before, during and/or after the chemical reaction takes place in the reaction medium.
  • Said phase can be liquid or gaseous.
  • the suspending medium comprises a liquid phase.
  • liquid suspending media include water, aqueous solution and organic solvent.
  • gaseous suspending media include air, noble gas and inert gas.
  • the inert gas can include, for example, nitrogen.
  • the suspending medium can include at least one additive, which affects chemical or physical properties of the at least one reagent, the at least one product or intermediate product, and/or the suspending medium.
  • said at least one additive can alter the ionic strength of the suspending medium, thereby changing the electrostatic field sensed by the at least one reagent and/or the at least one product or intermediate product.
  • the at least one additive can alter the surface tension of the at least one reagent or intermediate product.
  • the non-limiting examples of the additives suitable for use in the method of the present invention include a salt and a surfactant.
  • reagent refers to a component participating in the chemical reaction, which results in the formation of the at least one product or intermediate product.
  • the reagent is liquid.
  • the reagent and the suspending medium form a liquid.
  • the reagent is a solute dissolved in the suspending medium.
  • the reagent comprises ions.
  • the reagent is gaseous. In some embodiments, the reagent is solid. In other embodiments, the reagent is not solid.
  • the reagent is selected from an organic molecule, an organometallic molecule or a siloxane molecule. Each possibility represents a separate embodiment of the invention.
  • the reagent comprises a monomer.
  • said organic molecule, an organometallic molecule and/or a siloxane molecule is a monomer.
  • the non-limiting examples of monomers useful in the method of the present invention include dimethylsiloxane, dimethyldiethoxysilane vinylferrocene, h 5 -vi nyl cycl opentadi enyl , acrylate ethylene, acetate, amino acid, and derivatives thereof.
  • said monomer is liquid.
  • said monomer is present in a suspending medium in a form of emulsion droplets.
  • the suspending medium comprises water.
  • the suspending medium comprises oil.
  • the reagent comprises a cross-linker.
  • cross-linkers useful in the method of the present invention include trimethoxysilane, ethylene glycol di(meth)acrylate, methylenebisacrylamide, divinylbenzene, trimethylolpropane ethoxylate, and derivatives thereof.
  • said cross-linker is liquid.
  • said cross-linker is present in a suspending medium in a form of emulsion droplets.
  • the suspending medium comprises water.
  • the suspending medium comprises oil.
  • the reagent is selected from an inorganic salt, inorganic acid, organic base, metallic ion and non-metallic ion.
  • said salt is dissolved in the suspending medium.
  • the suspending medium can include water.
  • the reagent comprises an inorganic salt and the suspending medium is water.
  • inorganic salts useful in the method according to the principles of the present invention include salts, such as, but not limited to, sodium sulfate, ammonium hexaflourotitanate, barium acetate, calcium bromide, calcium nitrate, lithium acetate, ammonium acetate and aluminum phosphate.
  • the reagent comprises an ionic liquid.
  • the reagent is a gaseous organic molecule.
  • the gaseous organic molecule is selected from hydrogen chloride (HC1), ammonia (NH 3 ) and a combination thereof.
  • the at least one product of the chemical reaction is a sodium chloride (NH 4 Cl) salt.
  • the method of directed fabrication of a solid or semi-solid material comprises a step of initiating a chemical reaction in the reaction medium under the at least one standing acoustic wave using the at least one reagent.
  • chemical reaction refers in some embodiments to a process that leads to the transformation of the at least one reagent to a different chemical substance, and to the formation of the at least one product or intermediate product from said at least one reagent.
  • the at least one product or intermediate product of the chemical reaction has an acoustic contrast factor in respect to the medium in which it is suspended following its formation, which is different than zero.
  • the at least one product or intermediate product which is exposed to an acoustic standing wave field may respond to the primary acoustic radiation force by transporting to specific locations along the wave. If the product or the intermediate product are in a form of a sphere, the primary acoustic radiation force acting on such sphere in a SAW field can be expressed by Equations I and II:
  • P 0 , l, Vc, pc, pw, Pc and Pw are the acoustic pressure, acoustic wavelength, volume of the sphere, density of the sphere, density of the suspending medium, compressibility of the sphere, and compressibility of the suspending medium, respectively;
  • z is the distance between the sphere and the pressure node.
  • the at least one product or intermediate product of the chemical reaction has different density than the suspending medium. In further embodiments, the at least one product or intermediate product of the chemical reaction has greater density than the suspending medium. In additional embodiments, the at least one product or intermediate product has lower density than the suspending medium.
  • the at least one product or intermediate product has different compressibility than the suspending medium. In further embodiments, the at least one product or intermediate product has lower compressibility than the suspending medium. In additional embodiments, the at least one product or intermediate product has greater compressibility than the suspending medium.
  • the at least one reagent has greater density than the suspending medium. In some embodiments, the at least one reagent has lower compressibility than the suspending medium. In certain such embodiments, the at least one reagent, which is exposed to an acoustic standing wave field may respond to the primary acoustic radiation force by transporting to the standing acoustic wave pressure nodes.
  • the at least one reagent has lower density than the suspending medium. In some embodiments, the at least one reagent has greater compressibility than the suspending medium. In certain such embodiments, the at least one reagent, which is exposed to an acoustic standing wave field may respond to the primary acoustic radiation force by transporting to the standing acoustic wave pressure antinodes.
  • the density of the at least one product or intermediate product is greater than that of the at least one reagent. In some embodiments, the compressibility of the at least one product or intermediate product is lower than that of the at least one reagent.
  • the chemical reaction comprises a nucleation reaction.
  • the at least one intermediate product comprises a nucleation site.
  • nucleation refers to a first step in the formation of a new structure via self-assembly or self-organization of materials.
  • nucleation site refers to the initial aggregation of the material formed in a chemical reaction, which facilitates formation of the additional material thereon.
  • the nucleation sites comprise colloids.
  • the chemical reaction involves formation of micelles.
  • the at least one intermediate product comprises a micelle or an emulsion droplet.
  • emulsion droplet refers to a liquid phase, which is immiscible with the surrounding medium, such as, for example, suspending medium.
  • the emulsion droplet comprises a monomer or a cross-linker.
  • said emulsion droplets are suspended in water.
  • the chemical reaction comprises at least two intermediate products.
  • the first intermediate product comprises an emulsion droplet and the second intermediate product comprises a nucleation site.
  • the chemical reaction comprises transformation of the emulsion droplet into a nucleation site.
  • the chemical reaction comprises transformation of the reagent into an emulsion droplet.
  • the chemical reaction comprises transformation of the nucleation site into a solid or semi-solid material.
  • the at least one intermediate product comprises a particle. In some embodiments, the at least one intermediate product comprises a particle.
  • the particles can have a size in the nano-, micro-, or millimeter scale.
  • the particle can be in a form of a crystal.
  • the particles can be of various types, including, inter alia , organic, inorganic, metallic, and magnetic particles.
  • the at least one product or intermediate product is solid or semi-solid.
  • solid refers in some embodiments, to a material that can support its own weight and hold its shape, but can flow under pressure.
  • the at least one standing acoustic wave is generated prior to the formation of the at least one product or intermediate product.
  • the method comprises generating the at least one standing acoustic wave prior to the formation of the at least one product or intermediate product being in a form of a particle.
  • the method comprises generating the at least one standing acoustic wave prior to the formation of the at least one product or intermediate product being in a form of a nucleation site.
  • the method comprises generating the at least one standing acoustic wave prior to the formation of the at least one product or intermediate product being in a form of an emulsion droplet.
  • the step of exposing the reaction medium to the at least one standing acoustic wave is performed prior to the formation of the at least one product or intermediate product. According to further embodiments, the step of exposing the reaction medium to the at least one standing acoustic wave is performed prior to the formation of the at least one product or intermediate product being in a form of a particle. According to some embodiments, the step of exposing the reaction medium to the at least one standing acoustic wave is performed prior to the formation of the at least one product or intermediate product being in a form of a nucleation site. According to some embodiments, the step of exposing the reaction medium to the at least one standing acoustic wave is performed prior to the formation of the at least one product or intermediate product being in a form of an emulsion droplet.
  • the step of initiating a chemical reaction comprises spontaneous initiation.
  • spontaneous initiation refers to the type of process, which does not require application of energy or a promoter (also termed herein“initiator”) to occur.
  • the step of initiating a chemical reaction comprises providing a sufficient period of time for the reaction to start. In some embodiments, the step of initiating a chemical reaction comprises adjusting the concentration of the at least one reagent. In further embodiments, said adjusted concentration of the at least one reagent provides a defined onset of the chemical reaction. In some embodiments, the step of initiating a chemical reaction comprises controlling the reaction rate thereof.
  • initiating the chemical reaction comprises supplying an initiator to the reaction medium, wherein the initiator is selected from a chemical or a physical initiator.
  • the chemical initiator can be a catalyst selected from a heterogeneous catalyst, homogeneous catalyst, organocatalyst, enzyme, nano-material based catalyst, autocatalyst, or tandem catalyst.
  • the non-limiting examples of catalysts include organic peroxide, azo compound, metal iodide, metal alkyl, hydrogen peroxide, and persulfate.
  • the chemical initiator can be an additional reagent, which reacts with the at least one reagent in the reaction medium, generating a chemical reaction.
  • the step of initiating a chemical reaction comprises adding an additional reagent to the reaction medium.
  • the additional reagent comprises a cross-linker.
  • the physical initiator comprises supplying energy to the reaction medium, the at least one reagent and/or the suspending medium.
  • the energy can be supplied in a form radiation, temperature increase or pressure increase.
  • Physical initiator can further include a change in the pH in the reaction medium.
  • the term“continuing” with respect to a chemical reaction refers in some embodiments to a spontaneous continuing of the chemical reaction.
  • the step of continuing the chemical reaction can include providing a sufficient period of time for the reaction to form the desired amount of the solid or semi-solid material. In some embodiments, the step of continuing the chemical reaction is performed from about 10 seconds to about 10 hours.
  • continuing chemical reaction comprises adding the at least one reagent to the reaction medium. In some embodiments, continuing chemical reaction comprises adding the initiator.
  • continuing chemical reaction comprises agitating the at least one reagent and/or the suspending medium.
  • the method comprises exposing the reaction medium to the at least one standing acoustic wave without further agitation.
  • the method comprises providing continuous flow of the reagent through the reaction medium being under the at least one standing acoustic wave.
  • the present invention provides a method of fabrication of solid and semi-solid materials utilizing various chemical reactions.
  • suitable chemical reactions include polymerization, precipitation, sol-gel, combination reaction, replacement reaction and decomposition reaction.
  • the polymerization reaction is selected from emulsion polymerization, solution polymerization, suspension polymerization, step-growth polymerization, and chain-growth polymerization.
  • the at least one reagent can include a monomer and/or cross-linker.
  • the at least one reagent is a monomer or a combination of monomers and the step of initiating the chemical reaction comprises adding the cross-linker to the reaction medium.
  • the reaction medium further comprises a surfactant for stabilizing the reaction during polymerization.
  • the chemical reaction is an emulsion polymerization reaction.
  • the at least one reagent comprises dimethyldiethoxysilane and trimethoxysilane.
  • the suspending medium comprises ammonia and water.
  • the weight ratio between dimethyldiethoxysilane and trimethoxysilane can range from about 1 :99 to about 99: 1.
  • the weight ratio between dimethyldiethoxysilane and trimethoxysilane can range from about 1 :99 to about 1 : 1.
  • the weight ratio between dimethyldiethoxysilane and trimethoxysilane ranges from about 1 : 10 to about 1 : 1.
  • the weight ratio between dimethyldiethoxysilane and trimethoxysilane is about 1 :4.
  • the suspending medium further comprises NaS0 4 .
  • the chemical reaction is a precipitation reaction.
  • the at least one reagent comprises ammonium hexaflourotitanate and boric acid and the suspending medium comprises water.
  • the product or intermediate product of the chemical reaction is formed on a surface.
  • the solid or semi-solid material is formed on said surface.
  • the reaction medium comprises a substrate upon which the solid or semi-solid material is formed.
  • the substrate has an adhesive surface.
  • at least one of the surfaces of the reaction medium constitutes a substrate upon which the solid or semi-solid material is formed.
  • the reaction medium is a reaction vessel
  • the solid or semi-solid material can be formed on the bottom of the reaction vessel.
  • the method comprises forming the solid or semi-solid material on at least one of the bottom inner surface and top inner surface of the reaction vessel.
  • the solid or semi-solid material is formed on both the bottom inner surface and top inner surface of the reaction vessel.
  • the at least one standing acoustic wave has a chosen wavelength, l, in the suspending medium.
  • the pressure nodes are spaced apart by l/2.
  • the pressure antinodes are spaced apart by l/2.
  • the wavelength, l, of the standing wave can be selected such that a chosen number of pressure nodes is generated. According to some embodiments, the wavelength, l, ranges from about 10 nm to about 10 m.
  • the wavelength, l ranges from about 50 nm to about 5 m, from about 100 nm to about 1 m, from about 500 nm to about 500 mm, from about 1 pm to about 100 mm, from about 50 pm to about 10 mm, or from about 100 pm to about 1 mm.
  • the at least one standing acoustic wave has an amplitude ranging from about 1 Vpp to about 100 Vpp in the suspending medium.
  • the at least one standing acoustic wave can have various waveforms selected from, but not limited to, sinusoidal, triangular, saw and square waveforms.
  • the standing acoustic wave can be generated in any enclosed medium.
  • the acoustic wave can be generated by means of an acoustic transducer.
  • the acoustic transducer can be selected from an electromagnetic acoustic transducer, a microphone, a magnetic induction based microphone, a flat diaphragm loudspeaker, a shaped diaphragm loudspeaker, a piezoelectric crystal or a mechanical vibrator.
  • said acoustic transducer is an acoustic resonator.
  • the reaction medium can be placed in the acoustic field generated by said acoustic transducer.
  • the acoustic transducer is coupled to the reaction medium.
  • the acoustic transducer is coupled to the reaction vessel.
  • the acoustic transducer is coupled to the resonator cavity.
  • the at least one standing acoustic wave is generated by a pair of acoustic transducers.
  • the term“pair”, as used herein, refers to two similar objects, being positioned in parallel to each other, e.g., on opposing parallel surfaces, sides or edges of a surface.
  • the at least one standing acoustic wave is generated by an array of acoustic transducers, comprising from 1 to 100 acoustic transducers.
  • the at least one standing acoustic wave is generated by 15 to 60 acoustic transducers.
  • the at least one standing acoustic wave is generated by 20 to 30 or by 35 to 45 acoustic transducers. In some embodiments, the at least one standing acoustic wave is generated by 2 to 10 acoustic transducers, such as by 3 to 9, by 4 to 8, or by 5 to 7 acoustic transducers. Each possibility represents a separate embodiment of the invention.
  • the number and position of the acoustic transducers relatively to each other and to the reaction medium can be chosen to generate a series of standing acoustic waves.
  • the acoustic transducers are positioned to generate two orthogonal standing acoustic waves.
  • the acoustic transducers can be positioned to generate at least two standing acoustic waves, wherein the angle between the longitudinal axis or plane thereof is greater than 0° and less than 180 °, such as, for example, about 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80°, 90°, 100°, 110°, 120°, 130°, 140°, 150°, 160°, or 170°.
  • the method comprises situating the acoustic transducers on the same plane or different planes.
  • Said planes can be parallel to one another, orthogonal, or shifted by different angles.
  • the planes can be shifted by an angle greater than 0° and less than 180°, such as, for example, by about 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80°, 90°, 100°, 110°, 120°, 130°, 140°, 150°, 160°, or 170°
  • the standing acoustic waves are used for producing one-, two- or three- dimensional structures.
  • the method includes generating the at least one standing acoustic wave in one dimension.
  • the term “dimension”, as used with respect to the standing acoustic wave refers, in some embodiments, to a plane parallel to the longitudinal axis or plane of the standing acoustic wave.
  • Generating one standing acoustic wave in one dimension can be used to form elongated and/or parallel structures in a one-step fabrication process.
  • Said structures can be one-dimensional or two-dimensional. Each possibility represents a separate embodiment of the invention.
  • the method comprises generating a series of standing acoustic waves having a controlled constructive and destructive interference to create a pattern of pressure nodes and pressure antinodes in one or more dimensions.
  • a series of standing acoustic waves can be generated one dimension.
  • two-dimensional complex structures can be formed in a one-step fabrication process.
  • a series of standing acoustic waves in one dimension can be created using an array of acoustic transducers.
  • two orthogonal standing acoustic waves can be generated by two pairs of orthogonally positioned acoustic transducers.
  • a series of standing acoustic waves in one dimension can be created using a resonator cavity comprising more than one pair of opposing reflecting surfaces or having a cross-section other than a rectangular or cubic cross-section.
  • the method comprises generating a series of standing acoustic waves having a controlled constructive and destructive interference to create a pattern of pressure nodes and pressure antinodes in more than one dimension.
  • three-dimensional complex structures can be formed in a one-step fabrication process.
  • a series of standing acoustic waves in more than one dimension can be created using an array of acoustic transducers.
  • a series of standing acoustic waves in more than one dimension can be created using a resonator cavity comprising more than one pair of opposing reflecting surfaces being orthogonal to each other.
  • the at least one standing acoustic wave is a surface standing acoustic wave (SSAW).
  • SSAW surface standing acoustic wave
  • the term“standing surface acoustic wave” (SSAW) is used herein to describe a standing acoustic wave traveling along the surface of a material.
  • generating the at least one SSAW comprises providing a surface configured to transmit acoustic waves.
  • the SSAW is generated by applying an acoustic wave on the surface.
  • the acoustic wave can be applied to the surface by means of an acoustic transducer or a mechanical vibrator.
  • the SSAW is generated by coupling at least one acoustic transducer to the surface.
  • said acoustic transducer is an acoustic resonator, thereby providing a surface standing acoustic wave, when coupled to the surface.
  • a plurality of acoustic transducers is used to generate a SSAW.
  • two acoustic transducers can be positioned at the opposite sides of the surface to which they are coupled. Controlling the wavelength and amplitude of the surface acoustic waves generated by said two transducers can generate a resonance between said two waves, thereby forming a SSAW.
  • the plurality of acoustic transducers (such as at least four, at least six, at least ten, or at least twenty transducers) can be selected to provide a SSAW pattern by controlling the constructive and destructive interferences of the SSAWs generated by said acoustic transducers.
  • the surface which is configured to transmit acoustic waves has defined edges.
  • said defined edges of the surface are used as reflectors of the applied acoustic wave to form the SSAWs.
  • the acoustic wave can be applied to the surface by an acoustic transmitter.
  • a plurality of acoustic waves can be applied to the surface, by a plurality of acoustic transducers to form a desired pattern of pressure nodes and pressure antinodes on said surface.
  • the surface, which is configured to transmit acoustic waves is in contact with the reaction medium. In further embodiments, the surface which is configured to transmit acoustic waves is in contact with the surface on which the product or the intermediate product of the chemical reaction is formed. In yet further embodiments, the surface which is configured to transmit acoustic waves is in contact with the surface on which the solid or semi solid material is formed. In further embodiments, the surface which is configured to transmit acoustic waves is in contact with a substrate. According to some embodiments, the reaction medium is coupled to the surface which is configured to transmit acoustic waves. In further embodiments, the substrate in the reaction medium is coupled to said surface.
  • the reaction medium and/or the substrate can be attached directly to the surface which is configured to transmit acoustic waves without any adhesive layer. In other embodiments, the reaction medium and/or the substrate are attached to said surface with an adhesive layer. In some embodiments, the reaction medium is positioned in the acoustic field without directly contacting said surface.
  • the surface is a piezoelectric surface.
  • the SSAW is generated by applying an altering electric field to interdigitated transducers (IDTs) that are deposited on said piezoelectric surface.
  • IDTs interdigitated transducers
  • a first interdigitated transducer is located on one side of the piezoelectric surface
  • a second interdigitated transducer is located on the opposite side of the piezoelectric surface.
  • IDTs generate surface acoustic waves by converting electric signals to surface acoustic waves by generating periodically distributed mechanical forces via piezoelectric effect.
  • an electric signal such as alternating current
  • a SSAW can be formed, by controlling the wavelength and amplitude of the generated acoustic waves.
  • the step of exposing the reaction medium to the at least one SSAW can include direct or indirect contacting.
  • the step of exposing the reaction medium to the at least one SSAW comprises contacting the reaction medium with the surface configured to transmit acoustic waves.
  • said surface is a piezoelectric surface.
  • the reaction medium is coupled to the piezoelectric surface.
  • the surface on which the product or the intermediate product of the chemical reaction is formed is coupled to the piezoelectric surface.
  • the surface on which the solid or semi-solid material is formed is coupled to the piezoelectric surface.
  • the substrate in the reaction medium is coupled to the piezoelectric surface.
  • the reaction medium is exposed to the at least one SSAW, by means of indirect contact. In certain such embodiments, the reaction medium is positioned in the acoustic field without directly contacting the piezoelectric surface.
  • Device 11 includes microfluidic channel 13, including inlet 15 and outlet 17.
  • Device 11 further includes piezoelectric substrate 19, on which microfluidic channel 13 is disposed. Further disposed on substrate 19 is a pair of IDTs 21a and 21b, which are electrically connected to function generator 23.
  • Curved line 31 represents standing acoustic wave formed between IDTs 21a and 21b when function generator 23 is operating.
  • Parallel lines 33 represent the node areas of the standing acoustic wave.
  • Device 51 includes microfluidic channel 53 disposed between a pair of IDTs 55a and 55b on piezoelectric substrate 57. IDTs 55a and 55b are electrically connected to a function generator (not shown). Curved line 61 represents standing acoustic wave formed between IDTs 55a and 55b when the function generator is operating.
  • microfluidic channel 53 comprises at least one reagent suspended in a suspending medium and a chemical reaction is initiated, the formed product or intermediate product represented by circles 63 is directed to the node areas of the standing acoustic wave. Continuing the chemical reaction facilitates formation of an additional amount of reaction product 63 in the nodes areas, thereby fabricating a solid or semi-solid material in a directed manner.
  • the at least one SSAW is generated by using a pair of IDTs. In some embodiments, the at least one SSAW is generated by a plurality of IDT pairs. A person skilled in the art will readily realize that said plurality of IDT pairs (such as at least two, at least five, at least ten, or at least twenty IDT pairs) can be selected to provide a pattern comprising nodes and antinodes by controlling the constructive and destructive interferences of the SSAWs generated by said IDT pairs.
  • the SSAW is generated by an array of IDTs, comprising from 1 to 100 pairs of IDTs. In further embodiments, the SSAW is generated by 15 to 60 pairs of IDTs. In further embodiments, the SSAW is generated by 20 to 30 or by 35 to 45 pairs of IDTs. In some embodiments, the SSAW is generated by 2 to 10 pairs of IDTs, such as by 3 to 9 pairs, by 4 to 8 pairs, or by 5 to 7 pairs of IDTs. Each possibility represents a separate embodiment of the invention.
  • the piezoelectric surface comprises a transparent piezoelectric substrate comprising single-crystal lithium niobate or quartz.
  • the IDT typically has a periodic structure, comprising two interlocking comb-shaped arrays of metallic electrodes pairs (also termed herein“fingers”), as can be seen, for example, in Figure 1A.
  • the IDT suitable for use in the methods of the invention comprises from about 10 to about 100 electrode pairs. In certain embodiments, the IDT comprises from about 25 to about 40 electrode pairs. The number of electrode pairs of each one of the IDTs can be same or different.
  • the IDTs can be characterized by the space ratio of the fingers, which is the ratio between the width of the electrode and the space between the electrodes, and by an acoustic aperture, which corresponds to the length of the electrode.
  • the IDTs suitable for use in the methods of the invention have a space ratio of from about 3 : 1 to about 1 :3. In some exemplary embodiments, the IDT has a space ratio of about 1 : 1.
  • the IDTs suitable for use in the methods of the invention have an acoustic aperture of from about 0.5 mm to about 2000 mm. In certain embodiments, the acoustic aperture of from about 1 mm to about 1000 mm, from about 1 mm to about 500 mm, from about 1 mm to about 200 mm, from about 1 mm to about 100 mm, from about 1 mm to about 50 mm, or from about 1 mm to about 10 mm. Each possibility represents a separate embodiment of the invention. In some exemplary embodiments, the IDT has acoustic aperture of about 5 mm.
  • the electrodes of the IDTs can be made of any suitable metal, such as, but not limited to Cr, Au, Pt, Co, or combinations thereof.
  • the electrodes can be formed by sputtering said metal on the piezoelectric substrate.
  • the thickness of said electrodes can range from about 2 nm to about 500 nm, such as for example, from about 5 nm to about 400 nm, from about 10 nm to about 300 nm, from about 50 nm to about 200 nm. Each possibility represents a separate embodiment of the invention.
  • the electrodes comprise a layer of about 5 nm Cr and a layer about 100 nm Au.
  • the step of generating the at least one SSAW comprises applying a radio frequency (RF) signal to the IDTs.
  • the frequency can range from about 0.001 MHz to about 5000 MHz. In certain embodiments, the frequency ranges from about 0.051 MHz to about 2500 MHz, from about 0.01 MHz to about 1000 MHz, from about 0.5 MHz to about 500 MHz, or from about 1 MHz to about 100 MHz. Each possibility represents a separate embodiment of the invention. Each possibility represents separate embodiment of the invention. Each possibility represents separate embodiment of the invention. In some embodiments, said frequency ranges from about 15 MHz to about 35MHz. In some exemplary embodiments, the frequency is about 20 MHz and/or about 30 MHz. Said signal can be generated by a function generator. In some embodiments, said signal comprises alternating current.
  • the amplitude of the SSAW can be controlled, inter alia , by voltage applied to the IDT.
  • the applied voltage ranges from about 1 Vpp to about 500 Vpp. In further embodiments, the applied voltage ranges from about 5 Vpp to about 100 Vpp, or from about 10 Vpp to about 50 Vpp. Each possibility represents a separate embodiment of the invention. In some exemplary embodiments, the applied voltage is about 20Vpp.
  • the method of the present invention is used the preparation of a solid or semi-solid material having a one- or two-dimensional structure, comprising generating at least one surface acoustic wave in one dimension.
  • the method comprises generating one surface acoustic wave.
  • Materials obtainable by such method can have an elongated shape, including, inter alia , fibers, rods, wires, whiskers, strips, tubes, and combinations thereof.
  • the method comprises generating more than one surface acoustic wave. Materials obtainable by such method can have a 2D patterned structure, periodic structure, symmetric structure, and/or Chladni pattern structure.
  • the surface acoustic wave is SSAW.
  • the method of the present invention is used for the preparation of a solid or semi-solid material having a three-dimensional structure.
  • the method can be used to fabricate the material in one step or in multiple steps.
  • the method of the present invention is used to fabricate the three- dimensional material in multiple steps.
  • the terms“multiple steps” or“multi-step” refer in some embodiments, to a process, which includes more than one step of generating the at least one standing acoustic wave.
  • the method for the preparation of a solid or semi-solid material having a three-dimensional structure comprises generating a first standing acoustic wave or a series of standing acoustic waves in one dimension; and further comprises the steps of: removing the formed material; generating a second standing acoustic wave or a series of standing acoustic waves in said one dimension; and forming a three-dimensional structured solid or semi-solid material by combining the material formed under the first standing acoustic wave or series of standing acoustic waves with the material formed under the second standing acoustic wave or series of standing acoustic waves.
  • said standing acoustic wave is a SSAW.
  • the SSAW is generated on a surface and the material is formed on said surface.
  • the method comprises removing the formed material from said surface.
  • the method comprises generating a second SSAW or series of SSAWs on said surface. It is to be understood that the surface on which the SSAW is formed and the surface on which the material is formed can be different surfaces being in contact with each other, such as, for example, a piezoelectric surface and a bottom of the reaction vessel or a substrate.
  • the first standing acoustic wave or series of standing acoustic waves and the second standing acoustic wave or series of standing acoustic waves can be same or different. In some embodiments, the first standing acoustic wave or series of standing acoustic waves and the second standing acoustic wave or series of standing acoustic waves are different. The first standing acoustic wave can differ from the second standing acoustic wave by the direction of the longitudinal axis or plane of the standing acoustic wave relatively to the reaction medium.
  • a first standing acoustic wave and a second standing acoustic wave, having different directions of longitudinal axis or plane can be generated, for example, by two acoustic transducers having different orientations with respect to the reaction medium (but not being parallel to each other).
  • said two acoustic transducers can be positioned on adjacent walls of the cuvette, which serves as a resonator cavity.
  • the standing acoustic wave is SSAW.
  • a first SSAW and a second SSAW, having different directions of longitudinal axis or plane can be generated, for example, by two pairs of IDTs coupled to the same piezoelectric surface.
  • the first SSAW is generated by a first IDT pair and the second SSAW is generated by a second IDT pair.
  • the two pairs of IDTs can be positioned on the piezoelectric surface such that there is an angle between the electrode array direction of one IDT of the first IDT pair and one IDT of the second IDT pair.
  • the angle can be greater than 0° but smaller than 180°. In certain embodiments, the angle is 90° (i.e., the two IDT pairs are positioned orthogonally to each other).
  • the first standing acoustic wave can differ from the second standing acoustic wave by a parameter selected from, but not limited to, wavelength, amplitude, and waveform.
  • the step of removing the material formed under the first standing acoustic wave or a series of standing acoustic waves can be performed automatically or manually.
  • the material is removed automatically.
  • a moving unit such as, for example, a moving arm
  • the moving unit can be configured to descend towards the surface on which the material is formed.
  • the moving unit comprises an adhesive surface, configured to facilitate attachment of the formed material thereto.
  • the moving unit comprises an adjustable fixture, configured to facilitate attachment of the formed material thereto.
  • the moving unit is further configured to ascend from the surface on which the material is formed.
  • the method comprises repeating the steps of generating a first standing acoustic wave or a series of standing acoustic waves, removing the formed material and generating a second standing acoustic wave or a series of standing acoustic waves until a desired amount and/or thickness of the 3D material is formed.
  • Parameters of the standing acoustic waves can be altered between different steps to produce a complex structure.
  • the method comprises additional steps of generating additional standing acoustic wave or a series of standing acoustic waves, which can be the same as the first standing acoustic wave or a series of standing acoustic waves and/or the second standing acoustic wave or a series of standing acoustic waves, or different.
  • Figure 2A represents a flowchart of the method for the multi-step fabrication of a three- dimensional material, according to some embodiments of the invention.
  • Figure 2B schematically represents one of the steps of said method using IDTs configuration 101 and moving unit 111.
  • One pair of IDTs comprising IDTs 103a and 103b and another pair of IDTs comprising IDTs 105a and 105b are positioned on the piezoelectric surface (not shown) orthogonally to each other.
  • STEP 201 IDTs pair 103a and 103b generates a first SAW (not shown), enabling formation of material 107a.
  • STEP 202 Material 107a is removed by moving unit 111.
  • Removing material 107a comprises lowering unit 111, contacting it with material 107a and lifting.
  • STEP 203 IDTs pair 105a and 105b generates a second SAW (not shown), enabling formation of material 109a.
  • STEP 204 Material 109a is combined with material 107a by lowering unit 111, contacting material 107a, which is attached to unit 111, with material 109a and lifting unit 111.
  • STEP 20 la IDTs pair 103a and 103b generates a first SAW (not shown), enabling formation of material 107b.
  • STEP 202a Material 107b is removed by moving unit 111.
  • Removing material 107b comprises lowering unit 111, contacting material 109a, which is attached to unit 111, with material 107b and lifting.
  • STEP 203a IDTs pair 105a and 105b generates a second SAW (not shown), enabling formation of material 109b.
  • STEP 204a Material 109b is combined with material 107b by lowering unit 111, contacting material 107b, which is attached to unit 111, with material 109b and lifting unit 111.
  • the method represented in Figures 2A and 2B provides a multi-step fabrication of 3D materials.
  • the at least one reagent and/or the chemical reaction taking place under the first standing acoustic wave or series of standing acoustic waves and under the second standing acoustic wave or series of standing acoustic waves can be the same or different.
  • the method can include removing the unreacted reagent from the reaction medium following formation of material under the first standing acoustic wave or series of standing acoustic waves and adding a different reagent prior to generating the second standing acoustic wave or series of standing acoustic waves.
  • the three-dimensional structure comprises at least two layers of material formed.
  • the three-dimensional structure comprises at least three layers of material formed.
  • the three-dimensional structure comprises at least four, five, ten or twenty layers of material formed. Each possibility represents a separate embodiment of the invention.
  • the combination of the material formed under the first standing acoustic wave or series of standing acoustic waves with the material formed under the second standing acoustic wave or series of standing acoustic waves is performed by the formation of physical and/or chemical bonds. In certain embodiments, the combination of material formed under the first standing acoustic wave or series of standing acoustic waves with the material formed under the second standing acoustic wave or series of standing acoustic waves is facilitated by adhesion of said materials.
  • the material formed under the first standing acoustic wave or series of standing acoustic waves and the material formed under the second standing acoustic wave or series of standing acoustic waves are the same materials. In some embodiments, the material formed under the first standing acoustic wave or series of standing acoustic waves and the material formed under the second standing acoustic wave or series of standing acoustic waves are different.
  • the different materials can have different structures, chemical composition, dimensions, shape, weight, bulk density, or any combination thereof.
  • the multi-step method for the preparation of a solid or semi solid material having a three-dimensional structure comprises generating a first standing acoustic wave or a series of standing acoustic waves in one dimension and further comprising a step of continuously extruding the formed material.
  • said standing acoustic wave is a SSAW.
  • the SSAW is generated on a surface, the material is formed on said surface and the method comprises extruding the material from said surface.
  • the term“extruding” refers in some embodiments, to a process of displacing the formed material from said surface while maintaining its connection with a new material being formed on said surface.
  • the method comprises continuing the chemical reaction during the extrusion step.
  • the formed material is being extruded from said surface under said first SSAW or a series of SSAWs.
  • the method comprises terminating the first standing acoustic wave or series of standing acoustic waves and generating a second standing acoustic wave or a series of standing acoustic waves in said one dimension during the extrusion of the formed material.
  • the method comprises terminating the first SSAW or series of SSAWs and generating a second SSAW or a series of SSAWs on said surface during the extrusion of the formed material.
  • the formed material is being extruded under at least one of the first standing acoustic wave or series of standing acoustic waves and the second standing acoustic wave or series of standing acoustic waves.
  • the method enables continuous formation of a complex three-dimensional material without the need to combine distinct layers of the material following their formation.
  • the first standing acoustic wave or series of standing acoustic waves and the second standing acoustic wave or series of standing acoustic waves can be same or different.
  • the step of extruding the material formed under the first standing acoustic wave or a series of standing acoustic waves can be performed automatically, for example, by a moving unit, such as, but not limited to, a moving arm.
  • the moving unit can be configured to descend towards the surface on which the material is formed.
  • the moving unit comprises an adhesive surface, configured to facilitate attachment of the formed material thereto.
  • the moving unit comprises an adjustable fixture, configured to facilitate attachment of the formed material thereto.
  • the moving unit is further configured to controllably and/or continuously ascend from the surface on which the material is formed.
  • the method comprises repeating the steps of generating a first standing acoustic wave or a series of standing acoustic waves, extruding the formed material and generating a second standing acoustic wave or a series of standing acoustic waves until a desired amount and/or thickness of the 3D material is formed. Parameters of the standing acoustic waves can be altered between different steps.
  • the method comprises additional steps of generating additional standing acoustic wave or a series of standing acoustic waves, which can be the same as the first standing acoustic wave or a series of standing acoustic waves and/or the second standing acoustic wave or a series of standing acoustic waves, or different.
  • the at least one reagent and/or the chemical reaction taking place under the first standing acoustic wave or series of standing acoustic waves and under the second standing acoustic wave or series of standing acoustic waves can be the same or different.
  • the three-dimensional structure comprises at least two layers of material formed.
  • the three-dimensional structure comprises at least three layers of material formed.
  • the three-dimensional structure comprises at least four, five, ten or twenty layers of material formed. Each possibility represents a separate embodiment of the invention.
  • the method of the present invention is used to fabricate the three-dimensional material in one step.
  • the method comprises generating at least one standing acoustic wave or series of standing acoustic waves in greater than one dimension.
  • Figure 2C schematically represents IDTs configuration 301 for use in the method for the one-step fabrication of a three-dimensional material, according to some embodiments of the invention.
  • IDTs configuration 301 comprises a plurality of acoustic transducers 302, which are located on surfaces 303a, 303b, 303c and 303d of the resonator cavity.
  • Acoustic transducers can be switched on and off to generate a series of standing acoustic waves, forming a pattern of pressure nodes and antinodes, which defines the structure and/or form of the solid-or semi-solid material, fabricated by the method of the invention.
  • 3D materials obtainable by the single- and multi-step methods according to the various embodiments of the invention can have a 3D patterned structure, periodic structure, symmetric structure and/or Chladni pattern structure.
  • the method of the present invention comprises separating the formed solid or semi-solid material from the suspending medium.
  • the fabricated solid or semi-solid material is stable, thereby allowing removing thereof from the reaction medium even without a supporting substrate.
  • the fabricated solid or semi-solid material is removed from the reaction medium, while being supported on a substrate.
  • the solid or semi-solid material is selected from inorganic material, organic material, polymeric material, organometallic material, and composite or hybrid material. Each possibility represents a separate embodiment of the invention.
  • the material is polymeric.
  • the non-limiting examples of the polymeric materials obtainable by the method according to the principles of the invention include PDMS, styrene- butadiene (SBR), polybutadiene, polychloroprene (neoprene), nitrile rubber, acrylic rubber, fluoroelastomer (FKM), polyvinyl chloride (PVC), polystyrene, poly(methyl methacrylate) (PMMA), acrylonitrile-butadiene-styrene terpolymer (ABS), polyvinylidene fluoride (PVDF), polyvinyl fluoride, polytetrafluoroethylene (PTFE), polyaniline (PANI), polyacrylonitrile (PAN), and any combination thereof.
  • SBR st
  • the inorganic material obtainable by the method of the invention can include, inter alia , metals, metal oxides, metal hydroxides and metal sulfides.
  • the non-limiting examples of the inorganic materials obtainable by the method according to the principles of the invention include gold, silver, chrome, copper, titanium dioxide, fluorapatite, zinc oxide, iron oxide, cadmium hydroxide, yttrium oxide and derivatives and combinations thereof.
  • the inorganic material is titanium dioxide.
  • the solid or semi-solid material fabricated by the method according to the principles of the invention can have a two-dimensional structure.
  • the material has a three- dimensional structure.
  • the structure and/or shape of the solid or semi-solid material is defined by the parameters of the at least one standing acoustic wave.
  • the non-limiting examples of the parameters of the at least one standing acoustic wave which can define the structure and/or shape of the fabricated material include the number of generated standing acoustic waves, wavelength, amplitude, waveform, wave phase, the direction of the longitudinal axis or plane with respect to the reaction medium and combinations thereof.
  • the solid or semi-solid material fabricated by the process of the invention has a pattern, which is defined by the pattern of the pressure nodes and antinodes formed by a series of saws generated in the reaction medium.
  • the parameters of the at least one SSAW can be defined by the IDTs parameters and/or operation mode.
  • the amplitude of the SSAW can be defined by the voltage applied to the IDTs.
  • the wavelength can be defined by the IDTs parameter selected from applied signal frequency, acoustic aperture, space ratio, the type of the piezoelectric surface and any combination thereof.
  • the structure and/or shape of the solid or semi-solid material is defined by the parameters of the IDTs.
  • the wavelength and/or amplitude of the at least one SSAW can further be defined by the composition of the reaction medium, including the suspending medium.
  • the structure and/or shape of the solid or semi-solid material can be controlled by a computer program, which defines the parameters of the at least one standing acoustic wave.
  • the solid or semi-solid material comprises at least one simple and/or complex geometric shape and structure. According to some embodiments, the solid or semi-solid material has a symmetric shape and/or structure in at least one dimension. In certain embodiments, the solid or semi-solid material has a Chladni pattern structure. In some embodiments, the solid or semi-solid material has a hollow or semi-hollow structure. In additional embodiments, the solid or semi-solid material has a periodic structure.
  • the solid or semi-solid material has an elongated structure.
  • elongated structure refers in some embodiments, to a structure, which length is at least two times greater than its width.
  • term “elongated structure” refers to a structure, which length is at least three, four, five, ten, fifteen, twenty, fifty, or hundred times greater than its width.
  • the non-limiting examples of said elongated structure include wires, rods, fibers, strips, whiskers, tubes, and combinations thereof.
  • the cross-section of the elongated structure can be selected from substantially circular, triangular, square, or rectangular.
  • the solid or semi-solid material has a shape selected from a cube, sphere, polyhedron and ellipsoid.
  • the solid or semi-solid material obtainable by the method of the invention can have a size in the nanometer, micrometer, millimeter and macro scale. According to some embodiments, the size of the solid or semi-solid material ranges from about 10 nm to about 10 m.
  • the term“size”, as used in various embodiments of the invention refers to the length of the object in the longest dimension thereof.
  • the size of the material ranges from about 10 nm to about 100 nm, from about 100 nm to about 500 nm, from about 500 nm to about 1 pm, from about 1 pm to about 100 pm, from about 100 pm to about 500 pm, from about 500 pm to about 1 mm, from about 1 mm to about 100 mm, from about 100 mm to about 500 mm, from about 500 mm to about 1 m, or from about 1 m to about 10 m.
  • Each possibility represents a separate embodiment of the invention.
  • the solid or semi-solid material fabricated by the method according to the principles of the invention is stable.
  • the term“stable”, as used herein, refers to a feature of maintaining the two-dimensional or three-dimensional shape following the fabrication of the material. In some embodiments, the shape is maintained following the separation of the material from the suspending medium. In some embodiments, the shape is maintained following the separation of the material from the reaction medium. In some embodiments, the shape is maintained even if a standing acoustic wave is applied to the material following the fabrication thereof.
  • the solid or semi-solid material has adhesive properties.
  • said adhesive properties facilitate the formation and/or stability of the 3D structures thereof.
  • the chemical reaction is emulsion polymerization
  • the at least one reagent comprises dimethyldiethoxysilane
  • the suspending medium comprises water
  • the solid material is PDMS.
  • the suspending medium can further comprise ammonium.
  • the at least one reagent can further include trimethoxysilane.
  • the polymeric material has a two-dimensional structure.
  • the polymeric material is in a form of strips.
  • the polymeric material has a three-dimensional structure.
  • the polymeric material is in a form of two or more stacked layers of strips, forming a grid.
  • the thickness of the strips ranges from about 1 to about 100 pm.
  • the thickness of the strips ranges from about 5 to about 90 pm, from about 10 to about 80 pm, from about 20 to about 70 pm, from about 30 to about 60 pm, of from about 40 to about 50 pm. Each possibility represents a separate embodiment of the invention. In some exemplary embodiments, the thickness of the strips ranges from about 40 to about 50 pm. In some embodiments, the height of the strips ranges from about 1 pm to about 10 pm. In some exemplary embodiments, the height of the strips ranges from about 2.5pm to about 4pm.
  • the chemical reaction is precipitation
  • the at least one reagent comprises ammonium hexaflourotitanate
  • the suspending medium comprises water
  • the solid material is titanium dioxide.
  • the at least one reagent can further include boric acid.
  • the inorganic material has a two-dimensional structure. In further embodiments, the inorganic material is in a form of strips.
  • the material fabricated by the method according to the principles of the invention is for use in the fabrication of sensors, electronic devices, medical devices, plastics, building elements, and automotive and aerospace parts.
  • the solid of semi-solid material fabricated by the method of the invention can be used in the fabrication of sensors, electronic devices, energy storage devices, medical devices, plastics, and various elements for automotive aerospace, and architecture applications.
  • a device for the directed fabrication of a solid or semi-solid material comprising at least one acoustic transducer configured to provide at least one standing acoustic wave in at least one dimension; means to configure at least one standing acoustic wave, and a reaction vessel, configured to include at least one reagent and a suspending medium.
  • the reaction vessel is directly or indirectly coupled to said acoustic transducer.
  • Said means to configure the at least one standing acoustic wave can include an additional acoustic transducer.
  • the two acoustic transducers are located on two opposite sides of the reaction vessel.
  • the standing acoustic wave can be configured to have a controlled constructive and destructive interference to create a pattern of pressure nodes and antinodes in at least one dimension.
  • the device comprises a resonator cavity in which the reaction vessel is disposed.
  • the at least one standing acoustic wave is SSAW.
  • the device comprises a surface configured to transmit the at least one SSAW, the surface having defined edges.
  • said means to configure the at least one SSAW include the edges of said surface.
  • the acoustic transducer comprises a pair of IDTs.
  • the device comprises a piezoelectric surface.
  • the reaction vessel comprises a substrate.
  • the substrate is in direct or indirect contact with said piezoelectric surface.
  • the device further comprises an RF signal generator.
  • the device comprises a plurality of acoustic transducers.
  • the number of acoustic transducers can range from 1 to 10000 acoustic transducers. In certain embodiments, the number of acoustic transducers ranges from 1 to 5000, from 1 to 1000, from 1 to 500, from 1 to 100, or from 1 to 50. Each possibility represents a separate embodiment of the invention.
  • the device comprises a plurality of IDTs pairs.
  • the two pairs of IDTs can be positioned on the piezoelectric surface such that there is an angle between the electrode array direction of at least one IDT of the first IDTs pair and at least one IDT of the second IDTs pair.
  • the angle can be greater than 0° but smaller than 180°. In certain embodiments, the angle is 90° (i.e., the two IDT pairs are positioned orthogonally to each other).
  • the device comprises a plurality of acoustic transducers, which are located on different surfaces of the resonator cavity.
  • the device comprises a rectangular or cubic resonator cavity, wherein at least three of the walls thereof comprise at least one acoustic transducer.
  • each wall of the resonator cavity comprises an acoustic transducer.
  • each wall of the resonator cavity comprises a plurality of acoustic transducers. Additional configurations of the resonator cavity, as described hereinabove, can be used.
  • the device further comprises means to configure at least one standing acoustic wave, having a controlled constructive and destructive interference to create a pattern of pressure nodes and antinodes in one or more dimensions.
  • said means are configured to control the operation of the plurality of acoustic transducers, including, inter alia , switching on, switching off, applied voltage, and RF signal frequency.
  • the device further comprises a moving unit, configured to remove the fabricated material from the reaction vessel.
  • the moving unit is configured to facilitate adhesion of the layers of the fabricated material.
  • the motion of the moving unit is controllable, thereby allowing slow continuous removal from the substrate.
  • the substrate is moveable, thereby allowing removal of the fabricated material from the reaction vessel.
  • the reaction vessel can include a beaker, a microfluidic channel, a mixing vessel, a pressurized vessel, a reactor and a micro-reactor.
  • the reaction vessel is a microfluidic channel.
  • the microfluidic channel can be made of any suitable material, such as but not limited to, PDMS, glass, and quartz.
  • the device comprises a PDMS microfluidic channel comprising a glass substrate.
  • the PDMS walls are treated by a UV Ozone treatment.
  • the device comprises two IDTs deposited on a piezoelectric substrate; and a microfluidic channel positioned between said IDTs.
  • the device comprises two IDTs pairs (i.e., the two IDT pairs are positioned orthogonally to each other) deposited on a piezoelectric substrate; and a microfluidic channel positioned between said IDTs pairs.
  • the device comprises the moving unit.
  • Example 1 SSAW device fabrication and operation
  • a pair of interdigitated transducers was deposited on a transparent piezoelectric substrate. IDTs deposition was carried out by photolithography. A layer of photoresist (A Z 5214 E, microchem) was spin coated, irradiated by UV light source and subsequently developed in a photoresist developer (AZ 351B, microchem). A double metals layer was successively deposited on the wafer by electron beam evaporator and a lift-off process was used to remove the photoresist and the attached metal. The double metals layer included a 5 nm layer of sputtered Cr covered by a 100 nm layer of Au. Two different devices were fabricated. The first device included a pair of IDTs each having 40 pairs of electrodes.
  • the second device included a pair of IDTs each having 25 pairs of electrodes.
  • Space ratio of each IDT electrode array was 1 : 1 (electrode width was equal to the space between the electrodes), while acoustic aperture of each device was 1.2 mm.
  • the wavelength l of the SSAW generated by the IDTs is determined by Equation (III):
  • V is the speed of sound in the medium and F is the frequency.
  • the substrate was 128° Y-rotated, X-propagating, single-crystal lithium niobate.
  • a radio frequency (RF) signal was generated by dual channel arbitrary function generator (Siglent SDG 5162) without any amplifier. Measurements were performed on the two different devices, operating at an RF signal of 19.5 and 32.5 MHz. The applied voltage to each IDT in all of the following experiments was held constant at peak to peak amplitude of 20V and 12.5V. Each IDT comprised respectively 40 and 25 fingers electrode pairs.
  • PDMS microchannel 22 pm height was fabricated through a standard soft lithography and mold replica procedure, and positioned between the two IDTs.
  • Photoresist AR-N-4400-50
  • the silicon mold was coated with l, l,l,3,3,3,Hexamethyldisilizan (Merk).
  • Sylgard TM184 silicon elastomer base and SylgardTMl84 silicon elastomer curing agent (Dow Coming) were mixed at a 10: 1 weight ratio, cast on to the silicon mold and cured at 80°C for 2 hours, and finally peeled off from the silicon mold.
  • a cover glass was used as a substrate for the PDMS strips patterning.
  • UV Ozone treatment was performed only to the PDMS channel.
  • Silicon oil was used to couple the glass substrate to lithium niobate (LiNb0 3 ) chip with silicon oil.
  • Example 2 Silicone monomers emulsion solution preparation
  • Emulsion solution of silicone monomers in water was prepared as follows:
  • DMDES dimethyldiethoxysilane monomer
  • MTES trimethoxysilane cross- linker
  • the desired final weight percent of the polymer in the emulsion solution was kept at 12.5 wt% of the total solution, while varying the amounts of monomer (DMDES) and crosslinker (MTES) (including 0, 40, 60, 80 and 90 wt% MTES).
  • the solutions (from example 2) were infused into the microfluidic of the SSAW device (presented at Example 1) channel by a pres sure- driven flow. The flow was stopped after the microchannel was filled with the solution.
  • the radio frequency (RF) of 19.5 MHz and 32.5 MHz signals was applied to both IDTs. Two series of surface acoustic waves propagated in opposite directions, and their constructive interference results in the formation of a SSAW (as illustrated in Figures 1 A and 1B). Periodic distribution of the pressure nodes (minimum pressure amplitude) and anti-nodes (maximum pressure amplitude) on the substrate were formed.
  • the interaction of the generated SSAW with the emulsion droplets forces the droplets to migrate to the pressure nodes of the SSAW.
  • emulsion droplets also termed herein“micelles”
  • MTES cross-linker forces the droplets to migrate to the pressure nodes of the SSAW.
  • the process of the PDMS polymerization under SSAW can be divided into three main time dependent phases: 1) emulsion droplets or colloids (i.e., nucleation sites) migrate under the influence of the acoustic force to node positions; 2) colloids coalesce under the SSAW in the pressure nodes; and 3) polymerization is completed, additional polymerized colloids cannot be included in the formed strips.
  • Figures 4A-4C represent the polymerization of PDMS strips at different times from the exposure of the emulsion solution to the SSAW. The pictures were acquired by bright field microscope in situ on wet sample.
  • Figure 4A shows the reaction medium following about 30 seconds after generating the SSAW.
  • Figure 4B shows the reaction medium following about 3 minutes after generating the SSAW. It can be seen that most of colloids have coalesced and formed continuous strips.
  • Figure 4C shows the reaction medium following about 10 minutes after generating the SSAW. The strips are almost completely polymerized and additional solid particles cannot coalesce. The distance between the strips is 60p
  • Example 5 PDMS polymerization under SSAW using varying amounts of the cross-linker
  • Example 6 PDMS polymerization under SSAW with varying ionic strength of the solution
  • NaS0 4 in the emulsion solution is to reduce the electrostatic charge between emulsion droplets and to improve coalescence.
  • Figure 5A In the absence of salt (Figure 5A) only single polymerized beads were aligned along the node line, and coalescence did not take place due to the absence of screening of the electrostatic charge between the emulsion droplets.
  • Increasing the amount of salt from 0.3 to 0.7 wt% facilitated formation of continuous structures and improved the coalescence (Figure 5B and 5C, respectively).
  • the emulsion droplets were characterized by wide size distribution, such that the smaller droplets were located between the nodes and larger drops were located in the nodes. The concentration of the droplets in the nodes was not high enough to form a well-defined structure (Figure 5D).
  • Example 7 PDMS polymerization under SSAWs with varying amplitudes
  • FIG. 6A The influence of SSAW intensity (i.e. amplitude) on the thickness of polymerized structure is shown in figure 6A.
  • the experiment has been performed on 80% wt. cross-linker sample, 0.7% wt. Na 2 S0 4 salt. 20 m ⁇ of the solution have been infused into the PDMS channel 10 minutes after preparation. The results have shown that at 20V peak-to-peak amplitude, almost 80% of emulsion droplets are well ordered in the form of strips. At the 12.5V peak-to-peak amplitude only 50% of the droplets were formed into ordered continuous strips.
  • Figure 6A represents the effect of the primary acoustic radiation force on the thickness of the formed strip. Increase in the intensity of the acoustic force leads to the decreased thickness of the strips.
  • the thickness of the PDMS strips varies in the range between about 40-49pm and their height varies in the range between about 2.5pm and 4pm ( Figure 6B). Accordingly, the SSAWs parameters can be fine-tuned in order to provide solid or semi-solid materials with different dimensions.
  • Example 8 multi-step PDMS polymerization
  • a 3-dimentional structure was prepared by a multi-step process by stacking two layers of PDMS strips (Figure 7).
  • Each PDMS layer underwent polymerization under SSAW as demonstrated in the previous examples, wherein the orientation of the SSAW during the fabrication of the first layer was different than the orientation of the SSAW during the fabrication of the second layer.
  • the two layers were connected using cohesive forces between the PDMS strips.

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Abstract

La présente invention concerne un procédé de fabrication dirigée d'un matériau solide ou semi-solide qui consiste à effectuer une réaction chimique dans un milieu réactionnel exposé à au moins une onde acoustique stationnaire. L'invention concerne en outre des matériaux solides et semi-solides fabriqués par le procédé de l'invention.
PCT/IL2018/050739 2018-07-08 2018-07-08 Procédé de fabrication dirigée de matériaux à l'aide d'ondes acoustiques WO2020012454A1 (fr)

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CN114988388A (zh) * 2022-06-08 2022-09-02 电子科技大学 电火花合成催化剂的声悬浮cvd制备碳材料一体化装置

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US9199217B2 (en) * 2010-03-12 2015-12-01 Los Alamos National Security, Llc Material fabrication using acoustic radiation forces
US20160339360A1 (en) * 2015-05-20 2016-11-24 Flodesign Sonics, Inc. Acoustic manipulation of particles in standing wave fields

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9199217B2 (en) * 2010-03-12 2015-12-01 Los Alamos National Security, Llc Material fabrication using acoustic radiation forces
US20160339360A1 (en) * 2015-05-20 2016-11-24 Flodesign Sonics, Inc. Acoustic manipulation of particles in standing wave fields

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114988388A (zh) * 2022-06-08 2022-09-02 电子科技大学 电火花合成催化剂的声悬浮cvd制备碳材料一体化装置
CN114988388B (zh) * 2022-06-08 2023-09-15 电子科技大学 电火花合成催化剂的声悬浮cvd制备碳材料一体化装置

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