The present invention relates to methods for fluidic micro-assembled structure and, in particular, to methods and apparatuses for selective fluidic assembly of micro-components can be performed.
Micro-assembled devices offer the promise of an entirely new generation of consumer, professional, medical, military, and other products having features, capabilities and cost structures that cannot be provided by products that are formed using conventional macro-assembly and macro-fabrication methods. For example, there is a need, particularly in the field of flat panel displays, smart cards and elsewhere, for microelectronic devices or chips that can be integrated into or assembled as either a system or as an array, in a relatively inexpensive manner. In another example, there is a need for a cost effective method for allowing accurate and cost effective assembly of colored display elements such as electrophoretic beads in specific locations on display panels.
One advantage of such micro-assembled devices is that they can utilize different materials and devices (a process generally termed heterogeneous integration) in ways that create new product possibilities. For example, such heterogeneous integration provides the opportunity for relatively rigid structures such as such as silicon transistors or other electronic devices to be assembled into more complex electronic circuits using a flexible substrate as opposed to the rigid silicon substrates currently used for this purpose. In this example, such heterogeneous integration would provide a less expensive means to assemble silicon based integrated circuit components and/or any other kind of circuit components to form integrated circuits on flexible or rigid supports that are not made from silicon. However, it will be appreciated that in providing such heterogeneous integrated circuits, it is necessary that these processes provide for precise placement of multiple types of independent structures on the substrate. Such heterogeneous integration can also be used for other purposes. For example, heterogeneous integration can be used for purposes such as the assembly of pharmaceutical products, advanced materials, optical structures, switching structures, and biological structures.
Of particular interest in the electronic industry is the potential for micro-assembly to solve existing problems in the assembly of highly desirable but complex structures such as electronic displays. Typical electronic displays use a structure known as a “front plane” as the image forming surface. The “front plane” comprises an arrangement of image forming elements also known as active elements formed from structures such as liquid crystals, electroluminescent materials, organic light emitting diodes (OLEDs), up converting phosphors, down converting phosphors, light emitting diodes, electrophoretic beads, or other materials that can be used to form images. Such active elements typically form images when an electric field or some other stimulus or other field is applied thereto. Such electronic displays also incorporate a structure known as a “back plane” that comprises structures such as electrodes, capacitors, transistors, conductors, and pixel drivers and other circuits and integrating components that are intended to provide appropriate stimulus to the active components to cause the active components to present an image. For example, the active components can react to stimulus by emitting controlled amounts of light or by changing their reflectivity or transmissivity to form an image on the front plane.
It is well known to use heterogeneous integration methods to place elements on a substrate. Such heterogeneous integration methods can be generally divided into one of two types: deterministic methods and random methods. Deterministic methods use a human or robotic structure to place individual elements into particular locations on the substrate. Such methods are also known as “pick and place” methods. Such “pick and place” methods offer two advantages: complete control and positive indication that components have been appropriately placed in a desired location. Further, such “pick and place” methods also allow the precise assembly of different types of micro-components to form a micro-assembled structure that integrates different types of materials, micro-assembled structures and components.
It will be appreciated that deterministic methods require a high degree of precision by the person or machine executing the deterministic assembly process. Accordingly, such deterministic methods are difficult to apply in a cost effective manner. This is particularly true where the assembly of micro-components is to occur at a high rate of assembly or where large-scale assembly of micro-components is to be performed such as is required in commercial, pharmaceutical, or other applications.
Random placement methods such as fluidic self-assembly have been used to integrate electronic devices such as GaAs LEDs onto silicon substrates. Fluidic self-assembly is a fabrication process whereby a large number of individual shaped micro-assembled structures are integrated into correspondingly shaped recesses on a substrate using a liquid medium for transport. This method of self-assembly relies on gravitational and shear forces to drive the self-assembly of micro-components. Examples of this include U.S. Pat. No. 5,545,291 filed by Smith et al. on Dec. 17, 1993 entitled Method for Fabricating Self-Assembling Micro-Assembled Structures; U.S. Pat. No. 5,783,856 filed by Smith et al. on May 9, 1995 entitled Method for Fabricating Self-Assembling Micro-Assembled Structures; U.S. Pat. No. 5,824,186 filed by Smith et al. on Jun. 7, 1995 entitled Method and Apparatus for Fabricating Self-Assembling Micro-Assembled Structures; and, U.S. Pat. No. 5,904,545 filed by Smith et al. on Jun. 7, 1995 and entitled Apparatus for Fabricating Self-Assembling Micro-Assembled Structures.
a illustrates, generally, the operation of one type of prior art random placement method. In
Other approaches have been developed for using fluidic self-assembly to build a micro-assembled structure without relying exclusively on gravitational and/or shear forces. Some of these are illustrated in
In
c shows another fluidic self-assembly method. The method illustrated in
In the prior art illustrated in
Electrostatic attraction has been, proposed for use in positioning micro-components during micro-assembly. U.S. patent Publication No. 2002/0005294 filed by Mayer, Jackson and Nordquist, entitled “Dielectrophoresis and Electro-hydrodynamics Mediated Fluidic Assembly of Silicon Resistors”; and S. W. Lee, et al., Langmuir “Electric-Field-Mediated Assembly of Silicon Islands Coated With Charged Molecules”, Volume 18, Pg. 3383-3386, (2002) describe such methods.
As noted above, many micro-assembled structures incorporate a variety of different types of micro-components. Thus, heterogeneous integration of more than one type of micro-component using such a massively parallel random placement process, such as fluidic micro-assembly, is highly desirable. What is needed therefore is a method for assembling micro-components into a micro-assembled structure on the massive scale enabled by random placement methods such as conventional fluidic assembly but with the precision and selective assembly capabilities of deterministic methods.
Modifications to at least one of the fluidic self-assembly methods described above have been proposed in an attempt to meet this need. For example, in one approach, conventional fluidic assembly techniques have evolved that use differently shaped micro-components that are adapted to engage differently shaped receptor sites on a substrate. This requires that the substrate has binding sites that are uniquely shaped to correspond to a shape of a particular type of micro-component. However, the constraints of surface etching techniques, micro-component formation techniques, cost, electrical function, and orientation limit the number of shape configurations that are available for use in discrimination, which in turn limits the number of different components that can be placed on the substrate using such a process.
In another approach, Bashir et al. discuss the use of binding between complementary DNA molecules or ligands to discriminate between binding sites. While this approach provides a high degree of differentiation high cost may be encountered in patterning the DNA or ligands on the substrate. (H. McNally, M. Pingle, S. W. Lee, D. Guo, D. Bergstrom, and R. Bashir, “Self-Assembly of Micro and Nano-Scale Particles using Bio-Inspired Events”, Applied Surface Science, vol. 214/1-4 pp 109-119, 2003).
Thus, there is a need for a more cost effective method for the high volume heterogeneous assembly of micro-components.
A support and a method for fluidic assembly are provided. The support has a surface having binding sites adapted to receive micro-components of a type that are applied to the surface using a fluid; and energy absorbing heat producers at selected binding site. Each energy absorbing heat producer is adapted to receive energy and to transduce a portion of the received energy to heat the fluid proximate to the selected binding sites; so that when the micro-components are applied using a fluid that increases viscosity when heated, the heat generated by the energy absorbing heat producers increases the viscosity of the fluid proximate to the selected binding sites to prevent the micro-components from attaching to the selected binding sites.
In another aspect of the invention, a support is provided. The support having a surface having binding sites adapted to receive micro-components provided on the surface when such micro-components are incorporated into a fluid that increases viscosity in response to heat; and first energy absorbing heat producers at a first set of the binding sites each adapted to heat the support to increase the viscosity of the fluid proximate to the selected binding sites so that micro-components do not become attached to the selected binding sites in response to an energy exposure above a first level. Second energy absorbing heat producers at a second set of the binding sites are each adapted to receive a first energy exposure and to heat the support in response thereto to increase the viscosity of the fluid proximate to the selected binding sites in response to both the energy exposure above said first level and an energy exposure above a second, lower level.
In still another aspect of the invention a method is provided for assembling a structure on a support having a pattern of binding sites with selected binding sites being associated with energy absorbing heat producers. In accordance with the method, a first fluid is provided on the surface of the support with the first fluid being of a type that that increases viscosity when heated, said first fluid having first micro-components suspended therein each adapted to engage the binding sites; and the support is exposed to a first type of energy so that a first set of the energy absorbing heat producers release heat to increase the viscosity of the first fluid proximate to the selected binding sites so that the first micro-components suspended in the first fluid are inhibited from engaging the binding sites associated with the first set of energy absorbing heat producers. In a further aspect of the invention, a method is provided for assembling a structure on a support having a pattern of binding sites with selected binding sites being associated with energy absorbing heat producers. In accordance with the method, a first fluid is provided on the surface of the support with the first fluid being of a type that that increases viscosity when heated. The support is exposed to a first type of energy so that a first set of the energy absorbing heat producers releases heat into the first thermally responsive fluid to increase the viscosity of the responsive fluid proximate to the selected binding sites. A first carrier fluid is provided containing first micro-components each adapted to engage the binding sites. The exposure of the support to said first type of energy is continued so that said first set of the energy absorbing heat producers continue to release heat into the first fluid to maintain the increased viscosity of the responsive first fluid proximate to the selected binding sites so that the first micro-components suspended in the first carrier fluid are inhibited from engaging the binding sites associated with the first set of energy absorbing heat producers.
a-1e illustrate various types of methods that are known in the prior art for fluidic self-assembly;
a is a flow diagram of one embodiment of the method of invention;
b is a flow diagram of another embodiment of the method of the invention for use in assembling several different types of micro-components;
a and 4b illustrate the assembly of a first type of micro-components 80 to a support 60 to form a first micro-assembled structure;
c and 4d illustrate the assembly of an intermediate type of micro-component to first micro-assembled structure to form an intermediate micro-assembled structure;
e illustrates the assembly of a final type of micro-component to the intermediate micro-assembled structure to form a final micro assembled structure;
a-5g show embodiments of the invention, wherein a set of energy absorbing heat producers are incorporated into a support proximate to selected binding sites;
h-5j show embodiments of the invention wherein a set of different energy absorbing heat producers are incorporated into a support proximate to selected binding sites
k-5m illustrate micro-assembly using another embodiment of a support having a set of different energy absorbing heat producers;
n illustrates one embodiment of the invention wherein a support is provided energy absorbing heat producers;
a-6d illustrate various other embodiments of the invention wherein energy is selectively applied to cause localized heating of a carrier fluid;
a shows an embodiment of an apparatus for assembling a micro-assembled structure in which energy can be applied selectively to a support and thereby to a thermally responsive fluid having micro-components therein in order to permit selective assembly;
b shows an embodiment of a pattern energizer adapted to supply energy selectively to a support;
c and 8d illustrate a thermal printhead embodiment of a pattern energizer;
e shows a pattern energizer having a source of broadest energy and a filter;
a-d provide illustrations depicting the application of one embodiment or method and apparatus of the invention in the assembly of a display;
a is a flow diagram of one embodiment of the method of invention.
Support 60 has pattern of binding sites shown in
In operation, a thermally responsive fluid 72 is applied to support 60 (step 106). In the embodiment shown in
As used herein, the term thermally responsive fluid is used to mean a fluid that increases its viscosity upon heating. Examples of useful thermally responsive fluids include, but are not limited to, concentrated aqueous solutions of polymers, polysaccharides, or combinations thereof that increase viscosity upon heating. Useful polymers can include poly(ethylene oxide) (PEO), and poly(propylene oxide) (PPO) or a PEO-PPO copolymer surfactant (poloxamers). Poloxamer solutions are thermal gels with gel transition temperatures that can be tuned by concentration and type of poloxamer. PEO-PPO-PEO surfactants such as Pluronic® surfactants are commercially available from BASF Corp. that can be useful as a thermally responsive fluid for thermally controlled fluidic self-assembly. Other thermally responsive fluids can include aqueous solutions of: morpholine ethyleneoxide methacrylate, glycol derivatives, copolymers of morpholine ethyleneoxide methacrylate with polyethylene, polypropylene glycol derivatives, polysaccharides such as glycan or xyloglucan gels, and methylcellulose-polyethylene glycol-citric acid ternary system.
The useful range of poloxamer surfactants in solution depends on the gel transition temperature required. For example, for Pluronic® F127 fluid, the preferred concentration range for gel transition temperature of 45-50° C. is 8-20 wt %. For a Pluronic® P85 the preferred concentration is about 15 wt % for gel transition temperature of about 70° C. For Pluronic® L62 the preferred concentration is about 25 wt % for gel transition temperature of about 46° C. For Pluronic® F87 the preferred concentration is about 22 wt % for gel transition temperature of about 38° C.
Still other examples of a thermally responsive fluid include aqueous solutions of morpholine ethyleneoxide methacrylate and copolymers of morpholine ethyleneoxide methacrylate with polyethylene and polypropylene glycol derivatives. U.S. Pat. No. 5,955,515, entitled “Water-Based Ink for Ink-Jet, and Ink-Jet Recording Method and Instruments Using the Ink”, filed by Kimura, et al. on Sep. 26, 1995, describes the following examples of morpholine ethylenoxides and corresponding temperatures at which the examples convert into a gel:
In still other embodiments, a thermally responsive fluid can comprise solutions of xyloglucan gels such as aqueous solutions of xyloglucan polysaccharide that have been partially degraded by B-galactosidase to eliminate 44% of galactose residues form gels at concentrations of 1.0-1.5 w/w at 37° C.
In yet another embodiment, a thermally responsive fluid can comprise an aqueous solution of a methylcellulose-polyethylene glycol-citric acid ternary system: with from is 0-10% polyethylene glycol (PEG), 0.1-3% methyl cellulose (MC), and 0.1-10% citric acid (SC). Preferably the molecular weight of the PEG is 1000-100,000 daltons, but most preferably 3,000-6,000 daltons. Most preferred formulation for a gel transition temperature of 38-46° C. is 0-2% PEG (Mw=4000), 1.0 wt % MC and 3.5 wt % SC, adjusted to pH of 5.
The aqueous solutions described herein can include but are not limited to alcohols and polyethylene glycol. Non-aqueous solutions can also be used. For example, a thermally responsive fluid can be provided that incorporates chlorinated solvents and other non-aqueous solvents.
Energy 90 is applied to heat thermally responsive fluid 72 in areas in and/or near selected binding sites on support 60, shown in
Accordingly, as is shown in
Micro-components 80 can include, but are not limited to, integrated circuits on silicon, nanowires, beads, rods, cubes, disks, buckey balls, capsules, electrophoretic beads, LEDs, light emitting materials, light reflecting materials, light absorbing materials, conductive materials, magnetic materials, dielectric materials, aerogels, biological cells, DNA and DNA derivatives, and DNA templated structures. Micro-components 80 can be sized within any range of sizes that can effectively be suspended in solution in the thermally responsive fluid. In this regard, in selected embodiments, micro-components 80 can be sized as small as 1 nanometer, and as large as several millimeters.
The first type of micro-components 80 are adapted to engage binding sites 62, 64, 66 and 68 as is known generally in the art described above. However, in the illustration of
After first type micro-components 80 have been assembled to each of the non-selected sites 64 and 68, first carrier fluid 73 and any non-engaged first micro-components 80 are removed from first micro-assembled structure 102 (step 109). This can be done by mechanical action, by vacuum, or by rinsing, for example. In one embodiment, a liquid such as thermally responsive fluid 72 is rinsed over support 60 to remove any of the first type of micro-components 80 that remain on support 60 and that are not bound to one of binding sites 62, 64, 66 or 68. During removal of first slurry 70, energy 90 is supplied to the selected binding sites 62 and 66 to prevent any non-engaged micro-components 80 of the first type from binding to the selected sites 62 and 66. The supply of energy 90 to binding sites 62 and 66 can be terminated after removal is complete (step 110). When energy 90 is terminated, temperature increases dissipate proximate to binding sites 62 and 66 and barrier zones 92 and 94 that are created as a result of such local temperature increases also dissipate. The first micro-assembled structure 102 is formed as a result of the union of the first type of micro-components 80 with support 60. This first micro-assembled structure 102 can, in some embodiments such as the embodiment of
Additional micro-components can also be assembled to first micro-assembled structure 102.
When it is determined that only one further assembly step is necessary to create a final micro-assembled structure 104 (step 112), a final slurry 76 of carrier fluid 73 having a final type of micro-component 84 is applied to first micro-assembled structure 100 (step 115). This enables a final type of micro-components 84 to engage binding sites 62 and 66 and thus form a final micro-assembled structure 104 as illustrated in
When it is determined that more than two micro-assembly steps are to be performed (step 112), such as for example, where more than two different types of micro-components are to be joined to support 60, additional steps 118-122, shown in
a and 4b illustrate the assembly of a first type of micro-components 80 to a support 60 to form a first micro-assembled structure 100 in the same manner as is described above with reference to
Steps 111-122 can be repeated as necessary to permit many cycles of micro-assembly to occur, each with an additional application of an intermediate slurry 74 of a carrier fluid 73 bearing intermediate type micro-components 82 to a previously formed micro-assembled structure. In any of these additional steps, energy can be applied as necessary to form barrier zones. When it is determined that only one further assembly step is to be performed (step 112) steps 113-117 are performed to yield a final micro-assembled structure 104 as shown in
As used herein, the first, intermediate, and final types of micro-components can comprise the same structures and can be different as necessary to permit heterogeneous micro-assembled structure.
Energy Application
The steps of providing energy (steps 107, 114, and 119) can be performed in a variety of ways. As noted above, energy can be applied indirectly to thermally responsive fluid 72 by applying energy to support 60 or to some component of support 60 so that support 60 radiates heat. In certain embodiments, energy is broadly applied to support 60 and support 60 is adapted to react to this energy in a selective way, and to thereby selectively heat the thermally responsive fluid 72. In other embodiments, energy is selectively applied to selectively heat the thermally responsive fluid 72.
a-5g show embodiments of the invention, wherein a set of energy absorbing heat producers 132, 134, 136, and/or 138 are positioned in association with support 60 proximate to selected binding sites shown as binding sites 62-68. Energy absorbing heat producers 132, 134, 136, and 138 receive energy in the form of optical, electrical, microwave, sonic or other sources and convert this received energy into heat. Examples of such energy absorbing heat producers 132, 134, 136, and 138 include deposits of materials that are reactive to an energy field such as compositions and compounds that are capable of receiving energy and converting at least some of this energy into heat including, but not limited, to metals and dyes that are capable of absorbing electromagnetic radiation of predetermined wavelengths. Examples of such dyes include but are not limited to: cyanine dyes, tellurium adducts, oxonol dyes, squaraine dyes, merocyanine dyes, and metal dithiolenes. Other examples of such absorbing heat producers 132, 134, 136, and 138 include ferro-magnetic heaters, thermal transducers, and other such heat generating materials. In the example shown in
b shows another embodiment of a support 60 having an arrangement of energy absorbing heat producers 132, 134, 136, and 138. In this embodiment, energy absorbing heat producers 132, 134, 136, and 138 are positioned around and proximate to binding sites 62, 64, 66, and 68. Energy 90 is shown to be selectively applied to energy absorbing heat producers 132 and 136 in the manner described above with respect to
c shows another embodiment of a support 60 having an arrangement of energy absorbing heat producers 132, 134, 136 and 138. Specifically, in the embodiment shown in
d shows still another embodiment of a support 60 having an arrangement of energy absorbing heat producers 132, 134, and 136. In this embodiment, support 60 has an arrangement of binding sites 62, 64, and 66 each having a liquid 140 that is adapted to engage a liquid engagement surface 88 of a micro-component 80. Energy absorbing heat producers 132, 134, and 136 are positioned on support 60 proximate to binding sites 62, 64, and 66. Energy absorbing heat producers 132, 134, and 136 receive energy 90 and convert this energy into heat. For example, when energy 90 is applied to energy absorbing heat producer 132 heat is produced. When this heat is transferred into first thermally responsive fluid 72 a barrier zone 92 is formed that inhibits micro-components 80 from engaging liquid 140.
e shows another embodiment wherein support 60 has binding sites 62, 64, and 66 each having a liquid 140 associated therewith to engage a liquid engagement surface 88 of a micro-component 80. As is shown in
f shows still another embodiment wherein a support 60 is used having binding sites 62, 64, and 66 each having a liquid 140 associated there with and provided to engage in liquid engagement surface 88 of a first micro-component 80. As is shown in
In any of
h through 5n show embodiments wherein support 60 is adapted with binding sites 62, 64, 66, and 68 that are associated with energy absorbing heat producers 132, 134, and 136 that can convert the same level of exposing energy into different levels of heat.
In
h,
5
i, and 5j illustrate how this can be done. In
i illustrates a second assembly step. In this assembly step, support 60 receives a lower energy exposure 190 that is adequate for the more efficient energy absorbing heat producers 134 to form a barrier zone 96 but that is inadequate for the less efficient energy absorbing heat producers 132 and 136 to form barrier zones so that introduction of an intermediate slurry 74 having second or intermediate micro-components 82 therein allows the intermediate type of micro-components 82 to engage binding sites 62 and 68 that correspond to the less efficient energy absorbing heat producers 132 and 136.
j illustrates yet another assembly step, such as a final assembly step. In this step, the exposure of support 60 to energy is too low to cause the more efficient energy absorbing heat producers 134 to form barrier zones and allows a final slurry comprising final type of micro-component 84 in a carrier fluid 76 to attach to binding sites 64 corresponding to those more efficient heat producers 134.
Dependence of the absorbance of the energy absorbing heat producers upon the spectral constitution of the energy, rather than gradation of that absorbance, can confer discrimination. For energy sources such as optical radiation electromagnetic radiation or sound, the frequency of oscillations of the energy determines its coupling to the energy absorbing heat producers. Discrimination can be conferred upon sites by making at least two types of energy absorbing heat producers with differing absorption spectra, then adjusting the oscillating frequency content of the energy source when the slurries are switched so that both types of energy absorbing heat producers form protective barriers with the first nominally uniform exposure but only one of the types of energy absorbing heat producers absorbs enough energy at a sufficiently rapid rate at the second exposure's oscillating frequency to radiate sufficient heat to form a barrier zone in a thermally responsive fluid.
k-5m depict another embodiment of a support 60 having an arrangement of energy absorbing heat producers 132, 134, 136, and 138 that respond to the a uniform exposure to energy by producing different amounts of heat. In this embodiment, energy absorbing heat producers can be provided on support 60 that have the same absorptivity but can provide discrimination. Accordingly, such energy absorbing heat producers of differing types can all be fabricated from the same material and can be the same thickness. This simplifies the production of the energy absorbing heat producers and control of the location of their mounting to the support 60.
Discrimination is accomplished in this embodiment by using an arrangement of energy absorbing heat producers having a different sizes to selectively control the amount of electromagnetic, optical, acoustic or other energy, limiting the rate of energy available for heating a thermally responsive fluid in a slurry to produce a barrier zone. The spatial distribution of the flow of heat away from the energy absorbing heat producer into cooler regions of the slurry determines the profile of elevated temperature surrounding each energy absorbing heat producer. Sufficient exposure 90 can cause an energy-absorbing heat producer to produce a barrier beyond the lateral extent of that heat producer.
k-5m show one embodiment of this arrangement of energy absorbing heat producers. In the embodiment shown in
m shows the application of a final slurry 76 having final micro-components 84 applied to support 60, while support 60 is not exposed to energy or is exposed to a level of energy (not shown) that is insufficient for any energy absorbing heat producer to produce a barrier zone. This allows each binding sites 62 and 68 associated with the widest energy absorbing heat producers 132 and 136 to receive final micro-component 86 upon introduction of final slurry 76.
n shows yet another embodiment of a support 60 that has energy absorbing heat producers 132 and 134 that are adapted to convert electromagnetic signals into heat. Specifically, in the embodiment shown in
Electrical circuits of this type found in energy absorbing heat producers 132 and 134 of
It will be appreciated that in general it is possible to obtain with a first energy absorbing heat producer a different response to a frequency or other spectral characteristics of electromagnetic radiation or sound form of energy, or to the wavelength that is inversely proportion to the frequency of that form of energy, compared to the response of a second energy absorbing heat producer by fabricating the first energy absorbing heat producer from a different dye, pigment, metal or other material or combination of materials exhibiting a different absorption or combination of materials exhibiting a different absorption spectrum than the second energy absorbing heat producer does.
a-6e illustrate various other embodiments of the invention wherein energy as is selectively applied to cause localized heating of a thermally responsive fluid 72. As is shown in
b illustrates the heating of a selected binding site 62 using contact heater 148 comprising a patterned heating block 150 with projections 152 to heat a support 60 having binding sites 62, 64, and 66 each associated with a liquid 140.
It will be appreciated that such a contact heater 148 can take many forms. For example, a heating block 150 of the type shown in
c shows a different embodiment of a heating block 150 having projections 152 in contact with support 60 and proximate to binding sites 62 and 66. In this embodiment, projections 152 have selectably addressable actuators 154 that bring projections 152 into and out of contact with support 60 on demand. In this way, during multiple assembly cycles, the pattern of heat applied to support 60 can be dynamically adjusted without moving either block 150 or support 60. In the embodiment shown, projections 152 have selectively addressable actuators such as electrically actuatable micro-motors or piezoelectric actuators that can selectively bring projections 152 into or out of contact with support 60 on demand.
d illustrates the heating of selected sites using a heating block 150 having projections 152. In this embodiment, projections 152 are adapted to incorporate a selectively actuatable resistive energy absorbing heat producer 156 so as to permit dynamic adjustment of the pattern of heat applied to support 60.
After support 60 has been heated by heat 90b, support 60 is passed through a first bath 165. First bath 165 contains thermally responsive fluid 72. As thermally responsive fluid 72 is exposed to heat radiated by support 60, barrier zones are formed as described above. Support 60 with certain sites blocked by the barrier zones is passed through a first slurry bath 166. Alternatively, support 60 can be heated by transfer energy as it is passed through first bath 165.
First slurry bath 166 contains a first slurry 70 having micro-components, such as first micro-components 80, within carrier fluid 73 such as thermally responsive fluid 72. The barrier zones inhibit the first micro-components 80 from engaging selected binding sites. Micro-components 80 engage binding sites not protected by barrier zones to form a micro-assembled structure 100. As support 60 continues to move through the system 158 shown in
The web of support 60 then passes over at least one intermediate roller 170. In the embodiment shown, intermediate roller 170 comprises another thermal transfer roller that is adapted to receive energy 90a from an intermediate pattern energizer 172 and to transfer heat 90b to selectively heat web of support 60. After support 60 has been heated by heat 90b, support 60 is passed through an intermediate slurry bath 174. Intermediate slurry bath 174 has a carrier fluid 73, comprising in this embodiment, a thermally responsive fluid 72 containing intermediate type micro-components 82. Intermediate micro-components 84 are then permitted engage binding sites on micro-assembled structure 100 to form an intermediate micro-assembled structure 102. The type of thermally responsive fluid 72 used in the intermediate slurry bath 174 can be the same as or can be different than the type of thermally responsive fluid used in carrier fluid that is used in the first slurry bath 166.
As thermally responsive fluid 72 is exposed to heat radiated by support 60, barrier zones are formed as described above. These barrier zones inhibit intermediate micro-components 84 from engaging selected binding sites. Micro-components 84 engage binding sites not protected by barrier zones to form a micro-assembled structure 100. As support 60 continues to move through the system 158 shown in
Web of support 60 then passes over final roller 180. In the embodiment shown, final roller 180 comprises another thermal transfer roller that is adapted to receive energy 90a from a final pattern energizer 182 and to transfer heat 90b to selectively heat web of support 60. After support 60 has been heated by heat 90b provided by final roller 180, web of support 60 is passed through an final slurry bath 184. Final slurry bath 184 contains at least one final type of micro-component 86 within a carrier fluid 73 such as thermally responsive fluid 72. It will be appreciated however that the thermally responsive fluid 72 can be used in the intermediate slurry bath 184 can be the same as or can be different than the carrier fluid that is used in the first slurry bath 166 or in the second slurry bath 174.
As thermally responsive fluid 72 is exposed to heat from support 60, barrier zones are formed as described above. These barrier zones inhibit the final type micro-components 86 from engaging selected binding sites. Micro-components 84 engage binding sites not protected by barrier zones to form a final micro-assembled structure 104. As support 60 continues to move through the system 158 shown in
It will be appreciated that once a pattern of energy is transferred to support 60, “hot spots” are formed on support 60 that have a finite lifetime because they cool by dissipating heat to their surroundings. A hot spot cools at a rate that depends primarily on the temperature difference between the hot spot and its surroundings including the thermally responsive fluid 72. In order to prolong the lifetime of a hot spot, a thermally responsive fluid 72 may be advantageously supplied at a temperature slightly below a transition temperature at which the viscosity of the thermally responsive carrier fluid undergoes meaningful change or transition of viscosity, such as a transition temperature at which thermally responsive carrier fluid 72 transitions from a liquid to a 921 so as to minimize the heat required to form a barrier zone 92 while at the same time reducing the temperature difference between the hot spot and its surroundings.
Another embodiment that applies a pattern of energy to form barrier zones corresponding to selected binding sites on a support, is shown in
Alternatively, any of the patterned energizers 164, 172, or 182 can also comprise a thermal head. For example, a typical thermal head for use in the method of the present invention contains a plurality of adjacent, microscopic heat-resistor elements, which convert electrical energy via a joule effect into heat. Such thermal printing heads can be used in contact or, in close proximity with support 60 so as to transfer the heat generated thereby to support 60 or to a thermal transfer roller such as first roller 162, intermediate roller 170, or final roller 180. The operating temperature of common thermal printheads is in the range of 300 to 400 C and the heating time per element may be less than 1 ms, the pressure contact of the printhead with the material being, for example, 50-500 g/cm2 to ensure good heat transfer.
b shows one embodiment of pattern energizer such as first pattern energizer 164 comprising a roller 191 that is adapted to provide a pattern of energy directly to support 60. As is shown in
Any of the pattern energizers 164, 172, and 182 can comprise, for example, a laser. Typical lasers which may be used include but are not limited to a near infra red laser such as GaAs semi-conductor laser diodes Nd:Yag, and/or Nd:YLF lasers. Alternatively, He/Ne or Ar lasers can also be used. Typically, this is done where support 60 has energy absorbing heat producers positioned to receive the energy from such lasers. In one embodiment, such lasers can be selectively scanned across support 60 to selectively apply energy to support 60 so that barrier zones can be created. For example, a laser such as an infra-red laser can be scanned across support 60 and energy required to produce the desired heating can be selectively applied thereby. In one embodiment, a scanning mirror such as is described in U.S. Pat. No. 6,069,680, filed May 30, 2000 in the names of Kessler et al., entitled “Flying Spot Laser Printer Apparatus and a Method of Printing Suitable for Printing Lenticular Images”, can be used to scan a laser.
In another embodiment of this type, laser thermal print heads developed for the graphics arts field such as GaAlAs lasers, can be used or modified to heat the localized regions of support 60. U.S. Pat. No. 4,911,526 filed Mar. 27, 1990 in the names of Hsu et al.; U.S. Pat. No. 4,900,130 filed Feb. 13, 1990 in the name of Haas; U.S. Pat. No. 6,169,565 filed Jan. 2, 2001 in the names of Ramanujan et al.; and WO 01/56788 A2 filed Feb. 1, 2001 in the name of Moulin describe laser thermal print heads 189 that can be used for such purposes. Light from channels of such laser printheads can be individually switched on and off to selectively expose localized regions of support. Hence the printhead prints the pattern of heat where barrier zones are to be established.
In still another embodiment of the invention, energy can be selectively applied by the use of a sound transducer adapted to emit sonic waves that generate heat in the fluid or in the support. An acoustic transducer embodiment of a pattern energizer can comprise for example a piezoelectric transducer or an array of piezoelectric transducers can be used for this purpose.
c shows an illustration of a section of a linear laser light beam 183 from a linear laser thermal printhead that can be used for this purpose. In this illustration, linear laser light beam 183 is segmented into a plurality of channels 185. Each channel 185 provides focused light to support 60 to heat support 60. Examples of such multi-channel print heads are provided in U.S. Pat. Nos. 6,582,875, 6,169,565 and WO 0156788. In the embodiment of
To improve the absorption of light supplied by a laser, or any optically based pattern heater that uses energy in the form of a beam of light, a compound or other material which is capable of efficiently converting light into heat can be added to a binding site, to the support itself, or to a liquid that is applied to the support. It will be appreciated that the embodiments of
In still other embodiments, any of pattern energizers 164, 172, and 182 can comprise a linear array heater disposed across a pathway used by support 60 such as an array of laser diodes, or another array of energy absorbing heat producers including but not limited to microwave sources. In yet another embodiment, a pattern of energy is applied using a source of broadcast energy to transmit the energy toward the support and a filter to absorb portions of the broadcast energy so that non-absorbed portions of the broadcast energy strike the support proximate to selected binding sites, causing heat to be transferred by the support proximate to the binding sites. In an alternative embodiment of this type, the pattern of energy formed in this manner is applied to the fluid. In one example of this, a photolithography type process can be used to image a pattern of light onto support 60 or into the thermally responsive fluid in order to create barrier zones as described above. 28.
e shows one embodiment of such an arrangement. As shown in
It will be appreciated that the methods described with respect
However, in another embodiment shown in
In another embodiment, individual sheets of support 60 can be passed through any of the above-described embodiments of an apparatus 158 for forming a micro-assembled structure without platens 190. For example, the individual sheets can be passed through apparatus 158 using any known conveyor system including but not limited to a belt drum or other conveying system.
In any of the embodiments shown in
a-11d illustrate the application of one embodiment of an apparatus 158 for forming a color display having color display elements comprising, in this embodiment, a combination of red, green, and blue colored electrophoretic beads or bichromic beads.
Referring to
A first slurry bath 166 applies a first slurry 70 of carrier fluid 73 having red micro-beads 230 to support 60. When the first slurry 166 is applied, red micro-beads 230 bind to red micro-cup sites 214.
In this way a first micro-assembled structure 102 is formed. Micro-assembled structure 100 is then rinsed in rinse 168 to remove any residual unbound red micro-beads 230. The energy that allowed the formation of barrier zones 92 and 94 is then removed or allowed to dissipate so that other barrier zones can be subsequently applied to first micro-assembled structure 102.
In the embodiment shown, after red micro-beads 230 are removed from first micro-assembled structure 100, a new pattern of energy is applied to first micro-assembled structure 100 and first micro-assembled structure 100 is exposed in an intermediate slurry bath 174 having, in this embodiment, intermediate micro-components comprising green micro-beads 232 in a thermally responsive fluid 72 causing the formation of intermediate barrier zones 96 proximate to blue micro-cup sites 218 as is shown on
Green micro-beads 232 are barred from engaging red micro-cup sites 214 because red micro-cup sites 214 are occupied by red micro-beads 230 and are also barred from engaging blue micro cups 218 because blue micro-cup sites 218 are shielded by barrier zones 96. Accordingly, as is shown in
As is also shown in
A final slurry bath 184 applies a final slurry 76 having blue micro-beads 234 and a carrier fluid 73 to intermediate micro-assembled structure 102. Blue micro-beads 234 are blocked from engaging red micro-cup sites 212, and green micro cup sites 214 as they are occupied by, respectively, red micro-beads 230 and green micro-beads 232. Accordingly, as is shown in
The first embodiment of this type shown in
Electrical conductors 242, 244, 226 and 248 can be formed from any material that is known to produce heat when electrical energy is passed therethrough. Examples of materials that can be used to form electrical conductors such as conductors 242, 244, 246 and 248 include but are not limited to compositions having metals such as copper, aluminum, or steel therein, carbon, graphite, and compositions of Indium Tin Oxide. Electrical conductors 242, 244, 226 and 248 can be formed during fabrication of the support 60 or can be later applied thereto using for example conventional ink jet, continuous ink jet, thermal, vacuum deposition or contact printing techniques known in the art. Electrical conductors 242, 244, 226 and 248 can be positioned on a surface of support 60 or within support 60.
As is shown in
One way to adjust the resistance of a portion of a conductor is to reduce amount of area through which current must pass when traveling through that portion of the conductor. This has the effect of increasing the resistance of that portion of the conductor and is schematically illustrated in
Electrical energy can be applied to the conductors of
It will be appreciated that in some cases the micro-assembly process described herein can be used to assemble an electrical circuit that incorporates the micro-assembled structures, the support and the conductors in a manner that is similar to a conventional circuit board. In such an embodiment, the conductors therein are primarily shaped and defined for use in carrying electrical or other signals between micro-assembled structures. However, these conductors can also be used to generate heat for forming barrier zones. One way to accomplish this is to simply apply electrical energy to conductors 246 of the circuit in the manner described above. The energy can be applied across the entire length of the conductor or across segments of the conductor as shown above.
Alternatively, as is shown in
In a subsequent assembly step, electrical energy is not passed between input conductor 260 and output conductor 262 thus, no barrier zone is provided in gap G and micro-components such as intermediate micro-components 84 or final micro-components 86 can enter the gap and can cooperate with input conductor 260 and output conductor 262 to form a micro-assembled circuit.
It will be appreciated that are a variety of ways in which electrical energy can be passed through a fluid. For example, in one embodiment shown in
Although conductors 242-252 and 260 and 262 are shown in
In any embodiment of the invention, the application of energy to heat a thermally responsive fluid can be performed at any time before or during an assembly process and/or before or during rinsing process so long as the energy is applied under circumstances that will allow the formation of barrier zones while there is a meaningful risk that micro-components will be positioned to engage the binding sites. Thus, for example, in the embodiment of
In various illustrations shown above, barrier zones 92, 94 and 96 have been shown having shapes defined for illustrative purposes and these shapes are not limiting. It is sufficient that a barrier zone provide only the minimum resistance to the binding of micro-components to a selected binding site to inhibit such binding. For example, in certain embodiments, a partial blockage of a binding site can be sufficient. In another example, where ligands or other biological binding sites are used, it can be sufficient merely to block or mask the receptor sites of the ligand.
Further, in the embodiments illustrated above, barrier zones have been shown as being provided only for open binding sites that do not have micro-components bound thereto. This too is not limiting and the invention can be practiced in a manner that allows the formation of barrier zones proximate to binding sites that are occupied by micro-components.
This can be done, for example, to protect such micro-components from damage during subsequent assembly steps.
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
This application is related to U.S. Ser. No. [Attorney Docket No. 87692], entitled THERMALLY CONTROLLED FLUIDIC SELF-ASSEMBLY METHOD, in the names of Daniel D. Haas et al.; and U.S. Ser. No. [Attorney Docket No.88328], entitled THERMALLY CONTROLLED FLUIDIC SELF-ASSEMBLY METHOD AND CONDUCTIVE SUPPORT, in the names of Theodore K. Ricks et al., all filed concurrently herewith.