MXPA99004004A - Thermally switchable optical devices - Google Patents

Abstract

Devices that comprise novel, mesoscopically periodic materials that combine crystalline colloidal array (CCA) self assembly with the temperature induced volume phase transistions of various, materials, preferably poly (N-isopropylacrylamide) (PNIPAM) are disclosed. In one embodiment, a PNIPAMCCA is formed in an aqueous media (14) and contained within cell means (16). In another embodiment, a CCA of charged particles (12) is formed and polymerized in a PNIPAM hydrogel. Methods for making these devices are also disclosed. The devices of the present invention are useful in many applications including, for example, optical switches, optical limiters, optical filters, display devices and processing elements. The devices are further useful as membrane filters. All of these devices have the feature of being tunable in response to temperature. Devices that change diffracted wavelength in response to pressure are also disclosed.

Description

THERMALLY CHANGEABLE OPTICAL DEVICES BACKGROUND DB THE INVENTION This invention was made with support from the Government under the Naval Research Office Grant No. N00014-94-1-0592 and from the Pittsburgh Material Research Center through the Air Force Office of the Granting of No Scientific Research. AFOSR-91-0441. The government of the United States of America has certain rights in this invention. 1. Field of the Invention The present invention relates generally to optical devices and methods for making them. More specifically, the present invention relates to novel periodically novel materials that combine self-assembly with crystalline colloidal array (CCA) with volume-induced transitions of volume of materials that undergo a volume change in response to changes in temperature. temperature. These materials are used to create refinable optical devices such as optical switches, optical limiters, optical filters that select and / or reject predetermined wavelengths of light. In addition, these materials can be used to create various display devices and processing elements as well as filter devices whose pore sizes can be varied. 2. Art Background The charged colloidal particles, when suspended in water, form a stable dispersion due to the Coulomb retention forces between particles. The property of the structural arrangement in such dispersions has been exploited to make devices such as printed web optical retro filters. The phenomenon of arrangement in colloidal suspensions has been useful in spectroscopy and in the Bragg diffraction techniques. See, for example, U.S. Patent No. 4,627,689. It has been found that mesoscopic crystalline structures can take many practical applications as optical filters in military, space, medical and research applications. In many such cases, it is necessary and desirable to filter out narrow bands of selected wavelength from a broader spectrum of incidental radiation.

Asher, in U.S. Patent No. 4,627,689 discloses a linear crystalline colloidal narrow band radiation filter which is made by forming a highly ordered crystalline colloidal structure within a container. The crystalline colloidal structure is formed by dispersing the ionized particles, for example, the polystyrene particles within an appropriate solvent.

A related description was made in Asher, U.S. Patent No. 4,632,517. This patent describes another narrow-band, colloidal crystalline radiation filter application, which forms the basis for a highly efficient and mechanically simple monochromator. This has application in improved systems for Raman research or spectrum emission of selected sample materials. Both of the aforementioned patents disclose structures that can be used to diffract a fresh radiation band from a wider radiation band.

A solid filter and a method for making a solid filter of an ordered dispersion of particles within a medium is described by Asher, in U.S. Patent No. 5,281,370. This patent describes a filter which is capable of diffracting Braggs, narrow bands of radiation. This is a solid filter, which has many practical applications.

Other filtering devices are also known. For example, U.S. Patent No. 4,803,688 describes the use of an ordered colloidal suspension for an optical device.

An optical filter is also disclosed in U.S. Patent No. 4,548,473. The filter comprises a first substance essentially transparent to light with a selected range of sequences and having a prime refractive index. The filter also includes a second substance, which has at least one resonance frequency within the first frequency range within the second refractive index, which is essentially equal to the first refractive index at all frequencies within the first frequency range except the frequencies near The resonance frequency. This device is based on resonance scattering by a disordered sample. The device is only a passive device meaning that the refractive index is not considered to depend on the time of the intensity.

The patent of the United States of America No.

No. 3,620,597 discloses a device which is capable of acting as a non-linear absorber of essentially all excess radiant energy of a predetermined intensity. The mechanism used by the device is different from that of the present invention.

U.S. Patent No. 4,832,466 describes an optical element that includes a modulating liquid cap composed of a solvent containing soluble polymer. The device requires polymers to be precipitated from a solution due to changes in temperature. This is not required by the present invention.

U.S. Patent No. 4,648,686 discloses an arrangement of the optical switch, which uses the refractive index temperature dependent characteristics of a crystalline material, however, the device is limited to being used for switching in a waveguide. Other devices for use in waveguides were described in the US Pat. Nos. 4,828,362 and 4,938,557.

U.S. Patent No. 4,268,413 describes devices that have the property of reversibly variable light-to-light absorbency. The device is said to be used in temperature measuring devices, in slippery ice warning devices and the like.

U.S. Patent No. 5,452,123 discloses a nonlinear optical device and a method for making the same. The method includes a solid crystalline colloidal dispersion of charged particles within the medium and introducing into the particles or medium a radiation response component, which, when struck at a critical density, causes a change in the respective index of the articles, whether the position is ordered, the average or both.

U.S. Patent Nos. 5,368,781 and 5,266,238 are directed to a finely tuned narrow band radiation filter comprising a crystalline colloidal array of charged particles fixed in a hydrogel film. Methods for filtering incidental radiation using these filters are also described.

In U.S. Patent No. 4,720,355 is directed to a non-linear optical medium having a "host" thermoplastic polymer which contains a "host" organic component; the organic component has an asymmetric electronic load structure and describes a non-linear optical response.

U.S. Patent Nos. 5,330,685, 5,338,492 and 5,342,552 are all directed to narrowband radiation filters comprising a crystalline colloidal array of charged particles in a polymeric hydrogel.

None of the patents mentioned above describe the unique devices of the present invention. However, there remains a need therefore for the optical device of diffraction of a predetermined wavelength band 30 and to be easily refined in terms of diffraction and diffraction wavelength region.

SYNTHESIS OF THE INVENTION These and other needs are met by the present invention, which provides useful optical devices such as optical switches, optical limiters, and / optical filters that respond to changes in temperature. "Optical switch" as used herein refers to an optical device that diffracts a wavelength of particle light weakly at a temperature and strongly at another temperature such a device is therefore "switched" open or closed by changing the temperature. The "optical filter" as used here, refers to an optical device that allows all light to pass but of a given wavelength; The diffractioned wave length d can be changed or refined by changing the temperature. An optical limiter as used herein refers to an optical device that allows radiation transmission below a certain threshold intensity, but decreases transmission at higher light intensities. The term "band" of wavelengths will be understood by those skilled in the art, which refers to an extension of wavelength. This band can be narrow, with a width of less than one nanometer or wide, covering a lot of nanometers.

The devices of the present invention function to selectively and effectively diffuse a narrow band of wavelengths from a broader spectrum of incidental radiation while transmitting adjacent wavelengths to a high degree. For example, the optical devices of the present invention can filter more than about 99 to 99.9% of a wavelength band of about 2 to 500 A while transmitting more than about 70 to 90% d of the wavelengths remaining.

The methods for making these optical devices are also described. Generally these methods are involved in creating a crystalline colloidal arrangement, where it is formed by electrical repulsive forces between particles, which have a charge of the same polarity. These particles self-assemble to form the crystalline colloidal array (CCA) of the present invention. An embodiment of the present invention is directed to a crystalline colloidal arrangement of poly (N-isopropylacrylamide) particles (PNIPAM) in water, contained within a cell. Another embodiment of the present invention is directed to a crystalline colloidal arrangement of polystyrene or other charged particles embedded in a PNIPAM gel. Other materials that undergo a phase d volume transition in response to temperature changes can also be used, such as poly (N-tert-butylacrylamide).

The optical devices of this invention can form the basis for highly efficient mechanically simple optical switches, optical limiters, optical filters, optical fine filters useful in many applications including, but not limited to, light curtains, optical computers, and optical protection. sensor in scientific and medical instrumentation, eye protection for laser welding, display devices, computer applications and laser applications such as laser surgery. The devices are also useful for many military applications. In general, the devices can be used with any product in which the radiation filtration characteristics are desirable. In addition, the present technology can be used to create efficient membrane filters for size separation.

It is an object of the present invention to provide an optical switching device which can operate to diffract in certain Bragg form wavelength bands of incidental light.

It is a further object of the present invention to provide an optical switching device that increases the diffraction intensity decreases in response to temperature changes.

It is another object of the present invention or device that functions as an optical limiter.

It is a further object of the invention to provide an optical switch or an optical limiter that operates to block the transmission of wavelengths of radiation within several microseconds or over longer or shorter periods, if desired.

It is a further object of the invention to provide a method for creating an optical device that can effectively filter 99% of the incidental radiation.

It is another object of the invention to provide such a method and device which are adapted, can be employed in the incorporations of optical limiter or in the incorporations of optical switch.

It is another object of the present invention to provide a device that filters a narrow band of wavelengths from a broader spectrum of incidental radiation while transmitting the adjacent wavelengths to a higher degree.

It is a further object of the invention to provide such an optical filter which may be at the end and through the ultraviolet, visible and infrared spectrum in response to the temperature.

It is another object of the present invention to provide devices that can be used in display devices and computer applications.

Another object of the invention is to provide useful devices such as wavelength tuning mirrors.

A further object of the invention is to provide devices useful for filtering particles.

This device can be used as a membrane filter whose pore size is adjusted in response to temperature changes.

These and other objects of the invention will be more fully understood from the following description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 demonstrates the temperature dependence of the diameter and turbidity of the disordered suspension of the PNIPAM colloid, as determined by the methods of Example 2.

Figure 2 is a schematic illustration of colloidal particles dispersed within a medium, the particles of which have undergone self-assembly to form a crystalline colloidal array according to one aspect of the present invention.

Figure 3 is a graph showing the diffraction of a crystalline colloidal array of PNIPAM at 10 ° C and at 40 ° C as determined according to the methods of example 3.

Figure 4 is a graph showing the refined Bragg diffraction temperature from a 125 micrometer thick film of a polymerized crystalline colloidal array of 99 polystyrene spheres of 99 nanometers embedded in a PNIPAM gel as determined by the methods of Example 5 .

Figure 5 is a graph showing the temperature dependence of the diffracted wavelength for a polymerized crystalline colloidal array according to the embodiment of the present invention.

DESCRIPTION OF PREFERRED INCORPORATIONS The present invention is directed to optical devices and novel methods for making the devices. The present invention is further directed to the methods of using the devices such as optical switches, optical limiters and / or optical filters.

The optical devices of the present invention generally comprise an ordered crystalline colloidal array (CCA) which can be either a suspension of ionized colloidal particles in an appropriate solvent or a solid version consisting of an array embedded in a hydrogel matrix. Any colloidal particles or hydrogel matrix are made of a material that undergoes a volume phase transition in response to temperature changes. More specifically, the colloidal particles used to form a crystalline colloidal array according to an embodiment are particles of any material that exhibit a change in particle volume in response to changes in temperature. The material used to form the matrix, according to another embodiment of the present invention, can be any material that forms a gel that changes the spatial dimension as a function of temperature. While it will be appreciated that any materials having the above described characteristics can be used, poly (N-isopropylacrylamide) is preferred for both of these embodiments. Therefore, these optical devices comprise crystalline colloidal arrays (CCA) of poly (N-isopropylacrylamide) colloids (PNIPAM) in a suitable solvent or a crystalline colloidal arrangement of polystyrene or other particles polymerized in poly (N-isopropylacrylamide) hydrogel. The poly (N-isopropylacrylamide exhibits a phase transition of volume induced by temperature) Thus, the optical devices of the present invention have the characteristic of being "switchable" and / "refinable" in response to changes in temperature.

Due to the use of the materials that respond to the temperature, the optical devices of the present invention are dynamically refinable and / or switchable, either with relasio to the size or the periodicity of the arrangement. This characteristic d commutability results from the change in the volume of this materials that accompanies a change in temperature. For example, poly (N-isopropylacrylamide) in water below 30 ° C is hydrated and swollen, but undergoes a phase transition of reversible volume from this swollen and hydrated state to a collapsed and dehydrated state when heated above the lower critical solution temperature of about 32 ° C. Such an increase in temperature causes the polymer to expel the water and contract in a state of hydrophobic polymer. This volume phase transition is used in the various embodiments of the present invention to create refinable or switchable optical devices.

Figure 1 illustrates the temperature dependence of the diameter and tubidity of a diluted suspension of the poly (N-isopropylacrylamide) coloid. The sphere diameter increases d from about 100 nm to 40 ° C to about 300 nm to 10 ° C; this corresponds to an increase of approximately 27 times in volume. The turbidity of the poly (N-isopropylacrylamide) suspension increases as the diameter of the sphere decreases at higher temperatures because the size and the refractive index of the particles of the poly (N-isopropylacrylamide) spheres are related.

An embodiment of the present invention is generally directed to an optical device comprising a crystalline colloidal array formed from the self-assembly of the poly (N-isopropylacrylamide) colloids. It is a feature of such an optical device that the size of the poly (N-isopropylacrylamide) colloids in the array can be altered or switched in response to the temperature. This change in size results in a change in the refractive index of the colloid particle and therefore in the diffraction intensity of the device. This difference in intensity allows the device to function as a diffraction intensity switch. The device can operate as the high-speed optical switch in the sense that radiation becomes opaque within the range of one nanosecond to one microsecond.

Highly charged colloidal particles that were dispersed and dispersed in a liquid medium of low ionic strength self-assemble due to electrostatic repulsion to form the crystalline colloidal array. These ordered structures are either cubic arrays of centered bodies (BCC) or cubic centered faces (FCC) with network constants in the mensocale range (50-500 nanometers (nm)). Just as X-rays diffract the atomic crystals by finding the Bragg condition, a crystalline colloidal arrangement diffracts visible ultraviolet (UV) radiation and near infrared (IR) light. The crystal colloidal arrangement can be prepared as macroscopically arranged arrangements of unpacked spheres nearby. Such arrangements exhibit a highly efficient Bragg diffraction; almost all the light that fills the Bragg condition is diffracted, while the adjacent spectral regions not satisfying the Bragg conditions will be transmitted freely. The "spheres not closely packed" refers to an order in which the spheres are spaced at some distance from each other.

The Bragg diffraction law is represented by the following formula: m? = 2 nd without? where m is the diffraction order,? is the wavelength of the incidental light, n is the index of the suspension, d is the interplanar spacing, and? is the angle between the incidental light and the glass planes.

Highly charged poly (N-isopropylacrylamide) colloidal particles can be prepared by the dispersion polymerization of N-isopropylacrylamide or an ion monomer and a cross-launch agent. U surfactant can be optionally added to make the colloids more monodisperse, which helps in the preparation of crystalline colloidal arrangement. A libr radical initiator must also be added to initiate polymerization. The polymerization can be run in water, preferably in ultrapurified water, at a temperature of at least about 40 ° C, preferably around 70 ° C, for a period of time sufficient to allow the reaction to be completed, typically at least about 30 minutes, preferably about 3 to 4 hours.

A preferred co-monomer and sole for use in the polymerization is 2-acrylamido-2-methyl-1-propanesulfonic acid; other co-monomers and only suitable ones include the sodium salt of styrene sulfonate, the salt of 3-sulfopropyl potassium methacrylate, the vinyl sulfonate, and 1-sodium, 1-allyloxy-2-hydroxypropane sulfonate. Any other ionic co-monomers can be used, in the absence of compatibility problems. The use of an anionic co-monomer in the polymerization process has the effect of increasing the surface charge density on the suspended copolymer particles. The increased surface charge increases the electric forces that form and reinforce the crystal arrangement.

Preferred cross-release agents are N, N'-methylenebisacrylamide and methylenebismethacrylamide. With polymerization, the cross-launch agents form an array and polymer cross-linked in which it keeps the colloidal particles intact. A weight ratio of the crosslinking agent to poly (N-isopropylacrylamide) of from about 1: 5 to 1: 200 is preferred. The more cross-launch agents used, the higher the rigidity and the lower the response of the colloid particles. Therefore, the amount of crosslinker can be altered to create the desired response in the optical device.

A preferred surfactant is sodium dodecyl sulfate and a preferred free radical initiator is potassium presulfat. Other free radical initiators suitable for use in the present invention include benzoin methyl ether benzoin ethyl ether, succinic acid peroxide, 2-hydroxy-2-methyl-1-phenylpropane-1-one, 4- (2-hydroxyethoxy) -phenyl- (2-propyl) acetone, 2,2'-azobis (2,4-dimethyl-4-methoxivalero) nitrile and azobisisobutyronitrile. The catalytic amounts of initiator, usually about 1 to 10% by weight, are effective for the purpose of the invention. The initiators are preferably employed in amounts of about 4% by weight based on the total weight of the monomers.

As will be appreciated by one skilled in the art, any other suitable ion co-monomers, cross-linked linkers, surfactants and libr radical initiators can be used in the absence of compatibility problems. The particles must be purified by any means known in the art. Preferably, the purification is achieved by ultracentrifugation, dialysis and / or ion exchange resin. The purification helps to ensure the self-assembly of the crystalline colloidal array, which generally takes place at a very low ionic strength level.

After polymerization, the particles can be stored in an ion exchange resin preferably in a 10% by weight bath of ion exchange resin suspension, such as the commercially available analytical class AG501X8 bed resin. Bio-Rad from Richmond, California. The io exchange resin should preferably be cleaned before use through a suitable process such as that taught by Vanderhoff et al., In the Journal of Science of Entrecara and Colloid, volume 28, pages 336-337 (1968).

Polymerization of poly (N-isopropylacrylamide) dispersion at temperatures of about 70 ° C gives collapsed colloidal spheres in the range of 60 to 120 nm in diameter. These small colloidal particles exhibit the same volume response at temperature as conventional poly (N-isopropylacrylamide) gels.

As illustrated in Figure 2, the poly (N-isopropylacrylamide) particles 12 in water 14 are contained within a chamber 16 of sufficient size to contain the crystalline colloidal array that is formed. The concentration of particles 12 in water 14 in this step determines at what wavelength the crystalline colloidal array will diffract light. Generally, the more "water the particle concentration is lower and the longer the wavelength to be diffractioned, the chamber 16 is preferably composed of quartz, LEXAN® or glass coated with LEXAN®. a bonded polymer of thermoplastic carbonate produced by the reaction of bisphenol A and phosgene The chamber 16 has a lower part 18 and the vertical side walls 20, 22, 24 and 26. The chamber 16 is sealed with an air-proof cover 28 The sealed chamber 16 is then maintained at ambient temperature for a suitable period of time to allow the array to crystallize.The highly charged colloidal poly (N-isopropylacrylamide) particles self-assemble to form a crystalline colloidal array, as shown in FIG. The camera should not be disturbed during the formation of the crystalline colloidal arrangement.Preferably, the camera is transparent to use the device in optical applications.These crystalline colloidal arrays will both be formed above and below the phase transition temperature of poly (N-isopropylacrylamide). The crystalline colloidal arrangement can be formed in any suitable solvent. As used herein, the term "suitable solvent" refers to any solvent that is compatible with the poly (N-isopropylacrylamide) or other suitable material that is being used, will promote the formation of the crystalline colloidal arrangement and will allow said crystalline colloidal arrangement suffering a volume phase transition in response to temperature changes. The preferred solvent is deionized water.

A crystalline colloidal arrangement of swollen and hydrated particles will weakly diffract light, but crystalline colloidal arrangement of compact particles will diffract efficiently. The concentration of particles inside the chamber when the optical switch is being used determines the wavelength that is diffracted and the temperature of the particles determines whether the light of the wavelength is weakly strongly diffracted, for example if the optical switch is "off" or "on".

Figure 3 shows the extinction spectrum of poly (N-isopropylacrylamide) crystalline colloidal array at both 10 and 40 ° C. The network constant of the BCC array is 342 nm and the closest neighboring sphere distance is 242 nm. low, the particles are swollen and touching In this state, the diffraction efficiencies of the crystalline colloidal array are small.Upstream of the transition phase, however, the particles become compact they diffract almost all the incidental light to the length of the Bragg wave. Therefore, the crystalline colloidal arrangement of compact spher diffracts light much more efficiently than the crystalline colloidal arrangement of swollen sphere, this is due to the non-coincidence of the superior refractive index for the compacted sphere, while the temperature change does not affect the The diffraction intensity of these devices does not affect the network spacing, the change in lnm of the diffraction d maximum wavelength with the heating from 10 ° to 40 ° C, shown in Figure 3, results almost entirely from the change in the refractive index of the water.

The diffraction efficiency of the crystalline colloidal arrangement depends on the scattered cross-section of the colloidal particles as well as on the order of arrangement. The change in particle size results in a change in the cross-section of sphere spreading, which in turn means changes in the diffraction intensity or in the efficiency of the array. Thus, the crystalline poly (N-isopropylacrylamide) colloidal array functions as a thermally controlled optical switch that can be activated or deactivated by changing the temperature at which the device is exposed.

Changing the temperature of the crystalline colloidal array can be achieved by any means known in the art. For example, the crystalline colloidal array can be placed in an oven, in hot or cold water, or the cell containing the crystalline colloidal array can be heated or cooled.

In another embodiment, an optical limiter is prepared by attaching an absorbing dye, preferably a non-luminescent dye-absorbent dye to the colloidal poly (N-isopropylacrylamide) particles before the crystalline colloidal array is assembled. Suitable dyes for this purpose include but are not limited to basic fuchsin (color index 42500), coffee Bismarc Y (color index 21000) and yellow Acridine G (color index 46025). The dye absorbs the radiation and generates heat which causes the particles of the crystalline colloidal arrangement to shrink. The refractive index of the particles is highly dependent on the temperature and shrinking the particles increases the refractive index. The thermally induced change in the refractive index occurs within several microseconds and changes the optical behavior of the device. The ordered arrangement diffracts more strongly when the particles shrink. In this way, the material acts as an optical limiter and Bragg diffracts a predetermined wavelength band of incidental radiation. The diffractioned wavelength is determined by the spacing and the crystal structure of the arranged.

In another embodiment of the present invention, wavelength diffraction devices are created by polymerizing a crystalline colloidal array of electrically charged particles within a hydrogel matrix to create a polymerized crystalline colloidal array (PCCA) film. These films use the volume phase transition properties of a polymerized medium, such as poly (N-isopropylacrylamide) gel, to control the periodicity of the crystalline colloidal array. The optical filters thus created have the ability to selectively diffract by thus filtering a narrow band of radiation from a wider band of incidental radiation. Materials for filtering particles can also be created.

This first step in the preparation of the incorporation devices is that of preparing the charged particles. The colloids of monodisperse particles can be prepared by emulsion polymerization or by any other means. For example, an emulsion polymer can be prepared by mixing the desired monomer with a crosslinking agent, a surfactant to aid in the formation of the emulsion, a buffer to maintain the pH of the solution constant and to prevent coagulation of the emulsion. particles, and a free radical initiator to initiate polymerization. In a preferred embodiment, the monomer is styrene, the cross-linking agent is divinyl benzene, the surfactant is sodium-di (1,3-dimethyl butyl) sulfosuccinate, initiators potassium persulfate and an ionic comonomer, preferably 1- is also added. sodium, l-allyloxy-2-hydroxypropane sulfonate. The compounds can also be used to prepare the emulsion polymers as long as compatibility problems do not arise. The particles should be purified by the use of centrifugation, by the use of centrifugation, dialysis and / or an ion exchange resin, if necessary, so as to form a crystalline colloidal arrangement. Alternatively, electrically charged particles which can be used in accordance with this embodiment are commercially available from Dow Chemical or from Polysciences, Inc. Purification of commercially available particles is also recommended.

The electrically charged particles are then dispersed from an aqueous solution containing N-isopropylacrylamide, a cross-linking agent and an ultraviolet photoinitiator. Alternatively, any material that undergoes a volume phase transition in response to changes in temperature can be used in place of N-isopropylacrylamide, including but not limited to poly (N-tert-butylacrylamide). Any cross-linking agent discussed with respect to the first incorporation can also be used. N, N'-methylenebisacrylamide is preferred. Preferred ratios of the cross-linking agent to the monomer are from about 1: 5 to 1:20, more preferably from about 1: 8 to about 1:12 and more preferably from 1: 9. In addition to forming the polymer network in the crystalline colloidal array, the cross-linking agent as used in this step, in this embodiment aids in the formation of the hydrogel and response to the resulting hydrogel film so that a self-supporting film results. The hydrogel films can be formed with some retention of the crystalline structure when also not as 1 part in 100 parts by weight d the co-monomer mixture is the cross-linking agent. In addition, an ultraviolet cauterizer can be added; The preferred compound for this use is 2,2'-diethoxyacetophenone. U free radical initiator sensitive to heat has been activated at a moderate temperature and can also be used alone or in combination with the activators.

After the formation, the mixture is then placed between two plates, preferably quartz plates separated by a parafilm spacer., at a temperature d from between about 0o to 10 ° C. A nonionic ultraviolet photoinitiator can then be used to initiate the polymerization. Any other means known in the art can be used to initiate polymerization as long as the method is chosen for the polymerization does not destroy or otherwise mess with the crystalline colloidal arrangement. Upon completion of the polymerization, the plates are removed and the stable polymerized crystalline colloidal array results. This film can be approximately 10 micrometers thick and can be made thicker based on the needs of the user.

An advantage of the device according to this embodiment of the present invention and that the highly ordered crystalline array of colloidal particles after d fixed in the hydrogel by polymerization, no longer depends on the interactive electric forces of charged particles for • maintain the crystalline structure.

Another advantage is that the optical device can be self-supporting membrane polymeric films, without the need for cell walls to contain the filter.

The particles used to create the crystalline colloidal array can be any particles selected from the group consisting of colloidal polystyrene, polymethylmethacrylate, silicon dioxide, aluminum oxide, polytetrafluoroethylene, or any other suitable materials, which are generally uniform in size and charge. 15 surface. The particles are chosen for their properties, as desired for the particular application. The particles • preferably they have a diameter between about 50 and 500 nanometers and can be either synthesized as discussed above or obtained commercially. 20 The polymerized crystalline colloidal arrangement film functions as an easily controlled, findable optical filter. The gel dimensions shrink and expand irreversibly continuously between about 10 and 35 ° C and the arrangement of embedded particle sphere, follow, changing the network spacing or the distance between the array particles.

By changing the network spacing, the length of dif diffractioned by the device also changes. More specifically, as the temperature increases, the network spacing decreases and the diffractioned wavelength decreases. The diffractioned wavelength must therefore be altered by varying the temperature and is thermally tunable from the far red to the near ultraviolet part of the spectrum. The diffracted wavelength can also be altered by varying the angle at which light hits the device. At a fixed angle to the incidental ray, the polymerized crystalline colloidal array acts as a findable wavelength reflector.

The heating of the polymerized crystalline colloidal arrangement can be effected by any of the means known in the art, as discussed above.

The width and height of the diffraction peak can be easily short, by choosing the colloidal particles of different size and diffraction index or by making different colloidal polymerized polymer films of different thickness. Generally, the larger particles will diffract more strongly and at a wider wavelength band; the smaller particles have a weaker diffraction, but diffract over a narrower band of wavelengths. Generally, a thicker polymerized colloidal array will diffract more than a thinner polymerized colloidal array, because each "layer" of the polymerized crystalline colloidal array will diffract by a certain amount of light thereby exhibiting a cumulative effect with multiple layers. The tuning range of the device can be extended or stressed by synthesizing polymerized crystalline colloidal array films with higher or lower concentrations of the cross-linking agents respectively. The amount of cross-linking agent greatly determines the rigidity of the crystalline colloidal array. The more crossed linker is added, the more rigid the crystalline colloidal array and the smaller the radiation band on the towel and the device can be tuned.

Figure 4 shows that the diffractioned wavelength for the prepared polymerized crystalline colloidal arrangement film can be tuned between about 4 points and 7 nanometers points by varying the temperature. It will be appreciated that the range of the monomer can be made wider.

Figure 5 shows the temperature dependence of the diffraction wavelength for the polymerized crystalline colloidal arrangement film where the incidental light is normal to the plane (110) of the BCC network. In addition to the change in wavelength, the diffracted wavelength, the peak diffraction intensity increases with decreasing volume. This is because the diffraction intensity is proportional to the intensity of scattering per layer that increases when the material shrinks.

A volume phase can also be effected by changing the solvent which is contained in a polymerized crystalline colloidal arrangement. Many polymers undergo some change with reversible conformational shape with changes in the solvent to which they are exposed. Therefore, a crystalline colloidal array polymerized in water can have a volume, and therefore a region of diffraction wavelength when taken out of water and placed in an organic solvent. Examples of organic solvents, which can induce volume changes include glycerol, ethylene glycol, methanol, ethanol, dimethylsulfoxide, phenylmethylsulfoxide, dioxane, dimethylformamide, polyethylene glycol, and acetonitrile and mixtures of these and other solvents.

The optical devices of the present invention wherein a crystalline colloidal array is formed of, for example, poly (N-isopropylacrylamide) colloids in water and contained within cell means, can also be used in transmissive display devices and / or reflective of two dimensions. As indicated above, the crystalline colloidal array of diffraction to light with a finely tuned temperature efficiency controlled by the final sphere diameter d temperature. A local temperature increase within the crystalline colloidal array so that the crystallized poly (N-isopropylacrylamide) colloidal array spheres in the heated area shrink and therefore more efficiently diffuse the heated n area. Therefore, an image is created in the crystalline colloidal arrangement that reflects the light of the color of sense by the wavelength region by diffraction of colloidal array cristalin and with an intensity terminated by the temperature. This application is particularly low in the sense that the present devices can be used to exhibit applications in bright environments such as sunlight. In addition, sharp films are reflected light of different colors such as by stacking films of red, blue green, a thin film color solution device can be created.

For example, a silica device still comprising three sharpened layers can be created in which each cap comprises a crystalline colloidal array of charged particles containing a light absorbing dye in an aqueous medium contained with cell means. Each layer has a different light absorber tint, so that each dye absorbs a different predetermined wavelength of light. A preferred embodiment, a layer has a dye that absorbs green, one that absorbs red and one that absorbs blue. Three light sources, each having different wavelengths corresponding to one of the light absorbing dyes used. The intensity of the light sources determines the amount of heat applied to each of the layers. Therefore, the excitation of the layers stacked by the three lights controlled turn on the colors in each case. E differential heating results in the appropriate combination of red, green and blue to produce the desired color.

Any known means in the art can be employed to effect the arrangement and to assemble such display devices. For example, the crystalline colloidal arrangement can be self-assembled between two quartz plates. Each of these quartz plates is equipped with narrow transparent metal strips, such as tin oxide strips of indium, which are on the inner surface of the plate and therefore in contact with the crystalline colloidal arrangement. The two plates are also oriented so that the two sets of strips are perpendicular to each other. A voltage difference located across the plates will cause current flow and localized heating of the region between the strips; the distraction of light will increase in the area that is heated and an observed color.

Another method of creating display devices is the use of thin wires in a cross pattern on the surface of only one of the plates. A flow of current through a pair of crossed wires will increase the temperature of the area where the wires cross.

Localized heating to effect the thermally induced color intensity change can also be effected through the use of electrical resistance materials of adequate resistivity.

In addition, such display devices can be created by the use of electronic circuits on glass or quartz plates. The circuits can be designed in such a way that the current flowing through the circuit adjacent to a pixel area heats that area controlled by the intensity of the pixel color. Other electronic means known to those skilled in the art can also be used.

In yet another method for creating a display device, a light beam or laser scanner is used to write a temperature pattern in the crystalline colloidal array. An absorbing dye, transparent in the visible spectral region, is incorporated into the crystalline colloidal arrangement. By illuminating said dyes the crystalline colloidal arrangement is heated through the absorption of light. The crystal colloidal arrangement will diffract light more efficiently in heated regions.

A thin-dimensional reflective display device can also be made by using the polymerized crystalline colloidal array discussed above. Because the crystalline colloidal array differs different colors at different temperatures, such a device can be used to create a multi-color display. This effect is achieved by heating different parts of the crystalline colloidal array at different temperatures. The heating can be effected by the means described above, such as by the use of metal strips which conduct d electrical resistance materials, electrical circuits or dye-absorbing light that generate heat upon exposure to light.

These display devices have numerous applications in computer technology, including but not limited to various processing elements and display devices.

The crystalline colloidal array of the present invention can also be used as a findable filtering membrane. The polymerized crystalline colloidal array material has two different types of pores within it, the first resulting from the hydrogel network and the second resulting from the interstitial spaces of the crystal lattice. The gel size is related to the synthetic parameters of the hydrogel formation, such as the monomer and the cross-linking concentration, the temperature and the solubility of the monomers and polymer chains. The gel can be synthesized so that this pore size can vary from as low as 1 nm or as large as one micrometer. The interstitial size is a function of the network spacing and diameter of the particles in the crystalline colloidal array. This pore size can be controlled by from about 5 nm to about 500 nm. The polymerized crystalline colloidal array can be made so that the porous hydrogels are larger than the interstitial pores, so that the interstitial pores will limit the factor by controlling the passage of large molecules such as DNA or other small particles through the material. . The size of the interstices in the polymerized crystalline colloidal poly (N-isopropylacrylamide) array can be selected by controlling the temperature and swelling or shrinking of the gel, or by placing the crystallized colloidal array polymerized in a solvent that will swell or shrink to the gel to the desired size. Therefore, the user can control the limiting pore size for which particle size the filter can receive, and the pore size can be easily monitored by examining the wavelength of the diffractioned light and applying the Bragg law.

The pore size of these filtration membranes must be adjusted to be equal to or less than the particles to be filtered. The material to be filtered sticks on the gel membrane filter and the membrane filter resists the passage of macromolecules or particles through the membrane interpices. These filters can be used to filter particles of these microns, or larger. Alternatively, these polymerized crystalline colloidal arrays can be polymerized onto a poly (N-isopropylacrylamide) hydrogel resulting from fibers having similar volume-induced changes in volume.The resulting filter will have interstitial pore sizes that are continuously variable by setting the parameter of network, by changing the temperature of the filter solution by between about 10 and 40 ° C. This will allow the selection of the temperature of the exact pore size desired.As will be appreciated by one skilled in the art, the hydrogel can be made from any monomers, including but not limited to acrylamide monomers that undergo a volume change in response to temperature and / or solvent changes.

The polymerized crystalline colloidal arrangement of the present invention has additional application as an additional sensor that liquids the temperature. For example, the polymerized crystalline colloidal arrangement can be applied to a surface; as the temperature changes, the color of the polymerized crystal array will change, with an increase in temperature changing the diffracted wavelength to the blue region.

In yet another embodiment, the devices of the present invention can be used as pressure sensors. To change the pressure on your devices, the network spacing of the particles in the array will also change. Therefore, changes in pressure will be detected by changes in the color diffractioned by the arrangement. Due to the response of the two devices of the present invention to the temperature, said temperature must be kept constant while the pressure changes are measured. Alternatively, materials that exhibit a volume phase transition in response to temperature can be used.

EXAMPLES The following examples are intended to illustrate the invention and should not be considered as limiting the invention in any way.

Example 1 Polymerization was carried out with dispersed to form charged particles of N-isopropylacrylamide to be used in the formation of crystalline colloidal array. The polymerization was carried out by using about 3.47 grams of N-isopropylacrylamide, 0.03 grams of 2-acrylamide-2 methyl-1-propanesulfonic acid, 0.105 g of N, N 'methylenebisacrylamide, O.OSOg of sodium dodecyl sulfate and 0.014 of persulfates potassium These ingredients were mixed around 250ml of ultrapurified water around 70 ° C for about 4 hours. After the synthesis, the latex was purified by exhaustive ultracentrifugation and subsequent mixing with a mixed bed ion exchange resin.

E-example 2 The temperature dependence of the diameter and turbidity of a suspension of colloidal poly (N-isopropylacrylamide) particles prepared according to the methods of Example 1 was determined. The diameter of the sphere was determined using a commercial quasi-elastic light scattering apparatus, specifically a Malvern Zetasizer 4. The tubidity measurements were carried out in a quartz cell of 1.0 centimeter length using an almost infrared spectrophotometer. visible ultraviolet. The solids content of the sample in the tubidity experiment was 0.071%, which corresponds to a particle concentration of 2.49 x 1012 spheres per millimeter. Figure 1 graphically showed the changes in diameter and turbidity when changing the temperature. As can be seen from the graph, the diameter decreased with increasing temperature, while the turbidity increased with increasing temperature. The example shows that the diameter of the particles changes with temperature, and that the light scattering from the particles increased with temperature.

Example 3 The diffraction of the crystalline colloidal arrangement of poly (N-isopropylacrylamide) at 10 ° C and at 40 ° C was determined. The spectra were recorded using a Perkin-Elmer? -9 UV-visible-near IR spectrophotometer. The suspension is contained in a 1.0 mm quartz cover oriented at a normal incidence to the incidental ray. The changing behavior was reversible; the spectrum was recorded after the seventh consecutive heat-cold cycle. The inclusion demonstrates the change in temperature between the arrangement of swollen spheres below the phase transmission temperature and the identical arrangement of compacted spheres above the transition. As can be seen from Figure 3, the diffraction intensity of the crystalline colloidal array at 40 ° C is considerably greater than that at 10 ° C. At lower temperatures a weaker diffraction was seen but at higher temperatures a strong diffraction was seen. Therefore, the device can be changed during one diffraction intension to another by changing the temperature.

Example 4 It was synthesized by photopolymerization or polymerized crystalline colloidal arrangement. About 0.2 grams of monodisperse polystyrene colloids (diameter of 9 nanometers, 19% solids), 0.35g N-isopropylacrylamide, 0.02 N, N'-methylenebisacrylamide and 0.004g of diethoxyacetophenon as an ultraviolet photoinitiator were used. The mixture was then stirred with an ion exchange resin. The mixture was then placed between two quartz plates separated by a paraffin spacer at about 2.0 ° C. The photopolymerization was initiated with ultraviolet light until s completed polymerization of the hydrogel. The quartz plates were removed. It was further determined that the polymerized film diffracted in a manner similar to that of the polymeric precursor. It was determined by comparing the diffraction of crystallized colloidal array polymerized at 2 ° C with the diffraction of the monomeric precursor.

Example 5 The temperature tuning capabilities of a polymerized crystalline colloidal array prepared according to example 4 were tested. The crystallized polymerized colloidal array was 125 mm thick and contained polystyrene spheres with diameters of 99 nanometers embedded in a poly (N-isopropylacrylamide) ge. Figure 4 confirms that the diffraction wavelength change resulting from the volume change induced by gel temperature alters the network spacing, and therefore the wavelength that diffraction e. The spectrum was recorded in a near-visible-UV IR spectrophotometer with the sample placed normal to the incidental lu ray.

As will be understood by one skilled in the art, the present invention provides optical devices which function either as optical change devices or as optical filtering devices. These devices are unique in the sense that they use the volume phase transition of the poly (N-isopropylacrylamide) that results from the temperature changes to control the optical properties.

While particular embodiments of this invention have been described for the purposes of illustration, it will be apparent to those skilled in the art, that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims. .

Claims (85)

R E I V I ND I C A C I ONE S

1. A thermally activatable radiation screening device comprising: a crystalline colloidal arrangement of particles charged in an aqueous medium; cell means for containing said crystalline colloidal array and the medium; Y wherein said charged particles undergo a volume phase transition in response to changes in temperature.

2. The device as claimed in clause 1, characterized in that said particles are particles of poly (N-isopropylacrylamide).

3. The device as claimed in clause 1, characterized in that said aqueous medium is water.

4. The device as claimed in clause 1, characterized in that said cell means are made of a material selected from the group consisting of quartz, bonded polymer of thermoplastic carbonate, and glass coated with a bonded polymer of thermoplastic carbonate.

5. The device as claimed in clause 1, characterized in that a photoabsorbent dye is attached to said particles.

6. The device as claimed in clause 1, characterized in that said device is an optical switch.

7. The device as claimed in clause 1, characterized in that said device is an optical limiter.

8. A method for making a thermally activatable radiation filtering device comprising: placing charged colloidal particles in an aqueous medium in a cell; allowing said charged colloidal particles to self-assemble to form a crystalline colloidal array; Y *. 45 wherein said charged particles undergo a volume phase transition in response to changes in • temperature.

9. The method as claimed in clause 8, characterized in that it includes the use of poly (N-isopropylacrylamide) particles as said particles.

10. The method as claimed in 10 clause 9, further characterized in that it includes the step of forming said charged particles by the dispersion and polymerization of N-isopropylacrylamide with a comonomer, a cross-linking agent and a free radical initiator. 15

ll. The method as claimed in clause 10, characterized in that it includes the use as said comonomer an ionic comonomer.

12. The method as claimed in clause 11, characterized in that it includes the use of 2-acrylamido-2-methyl-l-propane sulfonic acid as the ionic comonomer.

13. The method as claimed in 25 clause 12, characterized in that it includes employing N, N 'methylenebisacrylamide as said cross-linking agent.

14. The method as claimed in clause 13, characterized in that it includes the use as initiator of free radical a libr radical initiator selected from the group consisting of potassium sulfate benzoin methyl ether, benzoin ethyl ether, succinic acid peroxide, 2-hydroxy-2-methyl-1-phenylpropane-1-one, 4- (2-hydroxyethoxy) -phenyl- (2-propyl) ketone, 2, 2'-azobis (2,4-dimethyl-4-methoxivalero) nitrile, and azobisibutironitrile.

15. The method as claimed in clause 10, characterized in that it includes employing a surfactant in said dispersion polymerization.

16. The method as claimed in clause 15, characterized in that it includes the use of sodium dodecyl sulfat as said surfactant.

17. A method for filtering a narrow wavelength band from a wider spectrum of electromagnetic radiation with a thermally activatable filtering device comprising: forming a crystalline colloidal array of charged particles in an aqueous medium within a cell directing said broader spectrum of electromagnetic radiation over said cell means at an angle of incidence, whereby said wavelength band is diffracted Bragg outside said cell. broader spectrum of electromagnetic radiation; Y wherein said charged particles are undergoing a volume phase in response to changes in temperature.

18. The method as claimed in clause 17, characterized in that it includes employing the poly (N-isopropylacrylamide) particles as said particles.

19. The method as claimed in clause 17, characterized in that it includes employing said method as an optical switch.

20. The method as claimed in clause 17, characterized in that it includes employing said method as an optical limiter.

21. A thermally-findable radiation filtering device comprising a crystalline colloidal array of charged particles polymerized in a hydrogel; Y wherein said hydrogel undergoes a phase transition of volume in response to temperature.

22. The device as claimed in clause 21, characterized in that said particles are selected from the group consisting of colloidal polystyrene, polymethyl methacrylate, silicon dioxide, aluminum oxide, polytetrafluoroethylene.

23. The device as claimed in clause 22, characterized in that said hydrogel is a hydrogel of poly (N-isopropylacrylamide).

24. A method for making a thermally findable radiation filtering device comprising the steps of: a) adding electrostatically charged particles to a medium which, with polymerization, undergoes a phase transition of volume in response to changes in temperature; b) allow said particles to self-assemble in a crystalline colloidal arrangement; Y c) polymerizing said crystalline colloidal array within said medium so that a hydrogel matrix is formed around the crystalline colloidal array.

25. The method as claimed in clause 24, characterized in that it includes the use of electrostatically charged particles, particles selected from the group consisting of colloidal polystyrene, polymethyl methacrylate, silicon dioxide, aluminum oxide, polytetrafluoroethylene.

26. The method as claimed in clause 24, characterized in that it includes employing colloidal polystyrene as said particles and further includes the step d preparing said electrostatically charged particles mediant emulsion polymerization of said particles with a crosslinking agent as a surfactant, a buffer and its free radical initiator.

27. The method as claimed in clause 26, characterized in that it includes the use of divinylbenzene as said potassium persulfate crosslinking agent as said free radical initiator di (1,3 dimethylbutyl) sulfosuccinate sodium as a surfactant dich and an aqueous solution of N-isopropylacrylamide with said medium.

28. The method as claimed in clause 24, characterized in that it includes employing a crosslinking agent and a UV photoinitiator in said medium.

29. The method as claimed in clause 28, characterized in that it includes employing N, N 'methylene bisacrylamide as said cross-linking agent, and 2,2'-diethyxyacetophenone as said photoinitiator.

30. The method as claimed in clause 29, characterized in that it includes making said polymerization pass by ultraviolet radiation.

31. A method for filtering a narrow wavelength band from a broader spectrum of electromagnetic radiation with a thermally-findable optical filter device comprising: a) adding electrostatically charged particles to a medium that, with polymerization, undergoes a phase transition of volume in response to temperature changes; b) allow said particles to self-assemble in a crystalline colloidal arrangement; c) polymerizing said crystalline colloidal arrangement within said medium so that a hydrogel matrix is formed around the crystalline colloidal arrangement; d) adjusting the temperature of the polymerized crystalline colloidal arrangement such that said narrow wave length band is diffractioned; Y e) directing said broad spectrum of electromagnetic radiation over said polymerized crystalline colloidal array within said hydrogel matrix to effect filtering of the narrow wavelength band.

32. A thin two-dimensional diy device comprising: a crystalline colloidal arrangement of particles charged in an aqueous medium; cell means for containing said crystalline colloidal array and the medium; means for heating said crystalline colloidal arrangement; Y wherein said charged particles undergo a volume phase transition in response to the change in temperature.

33. The device as claimed in clause 32, characterized in that said heating means are selected from the group consisting of metal strips, d a light source used with light absorbing dye, electrical resistance materials and electronic circuits .

34. The device as claimed in clause 33, characterized in that said metal strips are strips of indium tin oxide conducting current.

35. The device as claimed in clause 32, further characterized in that it is useful as a processing element in an optical computer.

36. The device as claimed in clause 32, further characterized in that it is useful as a diy device in a computer.

37. The diy device as claimed in clause 32, characterized in that said diy is a monochrome diy.

38. The diy device as claimed in clause 32, characterized in that said diy is a color diy.

39. A diy device comprising: a) three stacked layers, each of said layer comprises a crystalline colloidal arrangement of particles charged in an aqueous medium, cell means for containing said crystalline colloidal array and the medium, and a light-absorbing dye that absorbs a light length of predetermined light wave, e wherein each of said layers has an absorber dye different from that of each of said other layers; Y b) three light sources, wherein each of said light sources is a different wavelength than each of the other lights and where each of the lights corresponds to one of said dyes so that each light and selectively absorbed by one of said dyes.

40. The diy device as claimed in clause 39, characterized in that one of said dyes absorbs blue, one of said dyes absorbs green and one of said dyes absorbs red.

41. The diy device as claimed in clause 40, characterized in that said light source are lasers.

42. A thin two-dimensional diy device comprising: a crystalline colloidal arrangement of charged particles polymerized in a hydrogel; means for heating said hydrogel; Y wherein said hydrogel undergoes a phase transition of volume in response to temperature.

43. The device as claimed in clause 42, characterized in that said heating means are selected from the group consisting of strips of metal, a light source used with a light absorbing dye, electrical resistance materials and electronic circuits.

44. The device as claimed in clause 43, characterized in that dishas strips of metal are strips of tin oxide of indium that conduct current.

45. The device as claimed in clause 42, also characterized in that it is useful as a processing element in an optical computer.

46. The device as claimed in clause 42, further characterized in that it is useful as a diy device in a computer.

47. The diy device as claimed in clause 42, characterized in that said diy is a monochrome diy.

48. The diy device as claimed in clause 42, characterized in that said diy is a color diy.

49. A display device comprising: a) three stacked sapas, each of said layers comprises a crystalline colloidal arrangement of serged particles polymerized in a hydrogel that undergoes a volume phase transition in response to temperature, wherein each of said sapes also includes an absorbing dye light absorbing a predetermined wavelength of light, wherein one of said layers has a different light absorbing dye than that of each of said other layers; Y b) three sources of light, where each of the different sources of light is a different wavelength than that of one of the other lights, and where each of the luses corresponds to one of dish dyes, so that Light is selectively absorbed by one of these dyes.

50. The display device as claimed in clause 49, characterized in that one of said dyes absorbs blue, one of said dyes absorbs green and one of said dyes absorbs red.

51. The display device as such is claimed in clause 50, which is sarasterized because the light source dishas are lasers.

52. A method for producing a thin two-dimensional display device that is: a) single charged colloidal particles, which undergo a volume phase transition in response to temperature changes in an aqueous medium in a cell; b) allowing said single-stranded partisans to auto-assemble to form a crystalline solidary arrangement; Y s) at least some of the crystalline solids arrangement to exert a phase transition of volume d said dished part of the solarium solitary arrangement.

53. The method as claimed in clause 52, sarasterized because it involves employing poly (N-isopropylarylamide) particles as the slendered particles.

54. The method as such is claimed in clause 52, characterized in that it includes the use of water as a mean disheveled medium.

55. The method as such is claimed in clause 52, characterized in that said cell has two quartz plates.

56. The method as claimed in clause 55, characterized in that it involves the use of quartz plasmas having metal strips attached to said plates, the metal strips of which are in contact with said crystalline colloidal arrangement.

57. The method as claimed in clause 56, characterized in that it involves the use of tin oxide strips of indium somo dishas strips of metal.

58. The method as such is claimed in Clause 57, which is sarasterized because it is employed to employ said step of heating a flow of current through said indium tin oxide strips.

59. The method as such is claimed in clause 52, characterized in that it includes the use of a light absorbing dye that heats up the exposure to light as said heating step.

60. The method as claimed in Clause 52, sarasterized because it involves the use of a sirsuite elestróniso in a dishousing step.

61. The method as such is claimed in clause 52, which is sarasterized because it involves the use of electrical resistance materials in said heating step.

62. A method to create a thin two-dimensional display device that appears: a) adding electrostatically harvested particles to a medium which undergoes a volume phase transition in response to changes in temperature with the polymerization; b) allow said particles to self-assemble in a crystalline colloidal arrangement; c) polymerizing medium disho so that the hydrogel matrix is formed around the monocrystalline solar array; Y d) heating at least some part of the crystalline colloidal arrangement to effete a volume phase transition of said heated part of said crystalline colloidal array.

63. The method as claimed in clause 62, characterized in that it includes the use of an aqueous solution containing N-isopropylarylamide somo medium disho and solidal polystyrene somo dishas serrated partisulas.

64. The method as such is claimed in clause 62, which is sarasterized because it also includes the use of a cross-linking agent and a UV photoinitiator.

65. The method as claimed in clause 64, characterized in that it includes the use of N, N'-methylenebisasilamida somo disho slugging binding agent and 2, 2'-diethoxyazophenone somo disino photoinisiator.

66. The method as such and somo is claimed in clause 55, which is sarasterized because it includes the effete of the polymerization step by means of UV radiation.

67. The method as claimed in clause 63, characterized in that it includes employing said heating pad in the group-selected heating means consisting of strips of metal that conduct the sorptive, a light-absorbing dye that is peeled off. Exposure to light and sirsuitos elestrónisos.

68. A method for filtering material that appears: a) add elastrostátisamente charged particles to a medium that, with the polymerization suffers a volume phase transition in response to temperature changes; b) allow said particles to self-assemble in a monocrystalline solar array; s) polymerizing medium disho so that the hydrogel matrix is formed around the crystalline arrangement; d) establishing a distal membrane filter with a crystalline solidal arrangement polymerized in a hydrogel matrix, where the filter has gel pores and interstitial pores and at least one of these pore media is less than or equal to the material that will be filtered; e) adjusting at least one of pore sizes d by changing the temperature; Y f) to make sure that the material contained in the material is filtered by sticking on the membrane filter and thus resist the passage of materials larger than equal to the pore size.

69. The method as claimed in clause 68, characterized in that it employs as the said electrostatically charged particles, particles selected from the group consisting of solido polystyrene, polymethyl methacrylate, silicon dioxide, aluminum oxide, polytetrafluoroethylene.

70. The method as claimed in Clause 69, sarasterized because it involves employing the single-stranded polystyrene as said particles and further inscribing the step of preparing said particles electrostátisament charges by emulsion polymerization of said particles with a cross-linking agent, a surfactant , a damped and a free radical initiator.

71. The method as claimed in Clause 70, sarasterized because it includes the use of divinylbensen somo disho slug-binding agent, potassium persulfate somo free radical free radical, di (1,3 dimethylbutyl) sulfosussinate sodium, said surfactant, and a Assuous solution of N-isopropylarylamide, medium disho.

72. The method as such is claimed in Clause 68, which is sarasterized because it also includes the use in said medium of a scribed bonding agent and an ultraviolet photoinisiate.

73. The method as such and somo is claimed in clause 72, sarasterized because it involves employing N, N'-methylene bisacrylamide as said cross-linking agent and 2,2'-diethoxyacetophenone as said photoinitiator.

74. The method as claimed in clause 73, sarasterized because it involves performing said polymerization step by ultraviolet radiation.

75. A filtering device comprising a membrane filter comprising a crystalline colloidal array of charged particles polymerized in a hydrogel that undergoes a volume phase transition in response to the temperature where said filter has gel pores and interstitial pores and therefore minus one of these pore sizes change response to temperature.

76. The device as claimed in clause 75, characterized in that said particles are selected from the group consisting of colloidal polystyrene, polymethyl methacrylate, silicon dioxide, aluminum oxide, polytetrafluoroethylene.

77. The device as claimed in clause 76, sarasterized because the hydrogel is poly (N-isopropylacrylamide).

78. A tunable filtering device comprising a monocrystalline single-stranded arrangement of sergeant particles polymerized in a hydrogel, wherein said hydrogel undergoes a phase transition of suar volume moving from a prime solvent in the sual the hydrogel is in a state in which the second solvent The sual the hydrogel is in a somatic state.

79. The device as claimed in clause 78, sarasterized because there are separate parts of the group consisting of polystyrene alone, polymethyl methacrylate, silicon dioxide, aluminum oxide polytetrafluoroethylene.

80. The device, as such, is claimed in clause 79, characterized in that said first solvent is water and said second solvent is acetonitrile.

81. The device, as claimed in clause 79, is sarasterized because first and second solvent disks are sequestered independently of the group consisting of a solvent and a mixture of solvents.

82. The display device, as such, is claimed in clause 49, which is sarasterized because the hydrogel is poly (N-isopropylarylamide).

83. A method to monitor the temperature that comes up: employing the device comprising a crystallized colloidal array polymerized in a hydrogel that undergoes a phase-volume transicion in response to temperature, wherein said device diffracts a different wavelength at different temperatures, and monitor changes in diffracted wavelength in response to temperature variations.

84. A method to monitor the pressure qu somprende: employing the device that comprises a monocular array of crystalline partisans in a mean state sewing means for containing a single-sided array and the medium, wherein said device diffracts at a different wavelength at different pressures; Y monitor changes in diffractioned wavelength in response to pressure variations.

85. A method to monitor the pressure comprising: employing the device comprising a crystallized colloidal array polymerized in a hydrogel wherein said device diffracts a different wavelength at different pressures; Y monitor the sambios at the diffracted wavelength in response to pressure variations. SUMMARY Devices comprising mesoscopically novel periodic materials that comprise self-assembled crystalline solular arrays (CCA) are disclosed are the volume phase transitions induced by the temperature of various materials, preferably poly (N-isopropylacrylamide) (PNIPAM). In one embodiment, a PNIPAMCCA is formed in the aqueous medium and is contained within the cell means. In another incorporation, a monocrystalline monocrystalline sarsapartic arrangement is formed and polymerized in a PNIPAM hydrogel. The methods for making these devices are also described. The devices of the present invention are useful in many applications including, for example, optical switches, optical limiters, optical filters, display devices and processing elements. These devices are also useful as membrane filters. All these devices have the ability to be refinable and response to temperature. It is also, so dessritos the devices that sambian difrassionada wavelength and response to pressure.