FIELD OF INVENTION
This invention relates to a process for generating miniaturized replicas of a 2D or 3D pattern or an object. This invention correlates closely to two areas: i) Shrinkage of soft materials like gels and ii) Soft pattern Transfer.
BACKGROUND OF THE INVENTION
Patterning of substrates on micro- or nano- meter scales is of great technological importance in the fabrication of semiconductors, integrated circuits, optical devices like display devices, anti-reflective surface coatings, MEMS/NEMS, chemical or biological sensors, DNA enrichment and other biological applications, lab-on-a-chip diagnostic devices, micro-fluidics, super hydrophobic surfaces etc. Lithography, which has several major variants, is the key process to create patterns on thin films or surfaces, hard or soft. The pattern created can be physical (relief patterns) or can be chemical (different wettability domains or different type of doping) in nature.
Of all the lithographic methods, photolithography is the most well established and popular method (see, for example, reference Xia, Y. and Whitesides, G. M. Angew. Chem. Int. Ed. 1998, 37, 550). A typical photolithography process involves placing a mask on a resist layer (a photosensitive polymer) and exposing it with an optical source. In most cases, upon exposing the resist layer to the source light, the chemical structure of the exposed area (areas not covered by

the mask) of the film changes, so that when immersed in a developer, either the exposed area or the unexposed area of the resist (depending on whether the resist used is positive or negative) gets removed to recreate the patterns. The lithography resolution is limited by the wavelength of the optical source and proper alignment of the mask with respect to the surface. Photolithography requires dedicated setup and can pattern only a photosensitive polymer layer. Photolithography is however a method closely associated. with the microelectronic industry and not suitable for all types of polymers.
Numerous technologies have been developed which aims at obtaining as small feature size as possible, overcoming the optical resolution limit of photolithography. Electron beam lithography has demonstrated 10 nm lithography resolutions, (see references Broers, A. N., Harper J. M. and Molzen, W. W. Appl. Phys. Lett. 1978, 33, 392, Fischer, P. B. and Chou, S. Y. Appl. Phys. Lett. 1993, 62, 2989). The applications of patterned surfaces is not only limited to semiconductor or electronics industry only and thus, there is need for processes that are able to rapidly produce micron and submicron sized surface patterns at affordable costs, without using very sophisticated instruments and will be able to pattern 'soft' surfaces like those of polymers. That is the reason for the alternative, "soft" lithographic processes (see, for example, reference Xia, Y. and Whitesides, G. M. Angew. Chem. Int. Ed. 1998, 37, 550) like micro contact printing, micro molding in capillaries, replica molding, Nano Imprint Lithography etc. becoming preferred and popular tools for patterning soft surfaces over large areas.
In the context of patterning of polymeric surfaces and creation of physical relief structures at submicron dimensions, Nano imprint lithography (NIL) (U. S. Patent No. 5,772,905 and references Chou, S. Y., Krauss, P. R. and Renstrom, P. J. Appl. Phys. Lett. 1995, 67, 3114 and Science 1996, 272, 85) has been successfully demonstrated as a method to create relief pattern of sub 25 nm feature size on polymer surfaces, over large areas. U. S. Patent No. 6,818,139 describes a method in which a polymer thin film is deposited on the substrate. A rigid mold having the desired shape and pattern is pressed into the polymer film at room temperature by high pressure compression techniques. U. S. Patent No. 6,833,162 describes a method for
generating colored nanolithography patterns of parallel lines or cross pattern lines on a glass or plastic substrate, said process consisting the steps of pressing a polycarbonate or aluminum mold obtained from a compact disk. U. S. Patent No. 7,117,790 describes a micro-contact printing tool having a print unit including a stamp head with a stamp and a wafer chuck for retaining a substrate. U. S. Patent 6,966,997 describes a method of patterning a thin polymer film coated on a surface using an elastomeric stamp. U. S. Patent 6,342,178 describes a replica molding method by curing a photo-curable liquid silicone rubber composition to form a transparent mother mold having a cavity corresponding to the outer contour of a master mold.
The patents and published literature which has been referred here as well as the state of the art in the field of soft lithography is based on the concept of creating a replica or an imprint of an original pattern or object on another film or object. The imprint or the replica thus obtained forms at the same length scale as that of the original pattern. This invention describes a method which can create a reduced sized replica of the original pattern.
Hydrogels are shown to be an important class of material in a wide range of chemical and biological applications because of their biocompatibility and response to a host of stimuli like pH, ionic strength (see, for example reference: Eachenbaum, G. M. Kiser, P. F. Simon, S. A. And Needham, D. Macromolecules 1998, 31, 5084.), temperature ,(see, for example reference: Harmon, M. E. Tang, M. and Frank, C. W. Polymer 2003, 44, 4547.), electric field (see, for example reference: Tanaka, T. Nishiq, I. Sun, S and Ueno-Nishio, S. Science 1982, 218, 467.), light (see, for example reference: Suzuki, A. and Tanaka, T. Nature 1990, 346, 345.), presence of chemical species (see, for example reference:Miyata, T., Asami, N. and Uragami, T. Nature 1999, 399, 766.) etc. Hydrogel films thus find important applications in substrata for cell cultures and cell immobilization, in tissue engineering (see for example, reference: Bhatia, S. N. and Liu, V. A. Biomed. Microdevices 2002, 4, 257.), biological and chemical sensors, electrophoretic separation and chromatography, drug delivery, (see, for example reference: He, H., Cao, X. and Lee, L. J. J. Controlled Release 2004, 95, 391.), flow actuators in microfiuidics (see for example, reference: Beebe, D. J., Moore, J. S., Bauer, J. M., Yu, Q., Liu, R. H., Devadoss, C. and Jo, B. Nature 2000, 404, 588.) and many other applications. Micro-patterned hydrogels are also useful in enhancing the effectiveness of sensors, preparation of arrays of tiny beakers for confined chemistry and DNA chip applications, probing of cell behavior on patterned surfaces, microfiuidics and lab-on-a-chip applications, (see for example, references: Unger, M. A.,Chou, H., Thorsen, T., Scherer, A. and Quake, S. R. Science 2000, 288, 113; Revzin, A., Tompkins, R. G. and Toner, M. Langmuir 2003, 19, 9855.; Zguris, J. C., Itle, L. J., Koh, W. and Pishko, M. V. Langmuir 2005, 21, 4168.; Weibel, D. B., Lee, A., Mayer, M., Brady, S. F., Bruzewicz, D., Yang, J., DiLuzio, W. R., Clardy, J. and Whitesides, G. M. Langmuir 2005, 21, 6436.)
U. S. Patent 7,CK)1,987 describes methods of making Hydrogels with controllable mechanical, chemical, and biological properties, particularly with proteinaceous hydrogels. U. S. Patent 7,052,913 relates to Matrices for drug delivery and methods for making and using the same. U. S. Patent 6,201,065 also describes the usage of Multi-block biodegradable hydrogels for drug delivery and tissue treatment, where invention describes how Gel-forming macromers including at least four polymeric blocks, at least two of which are hydrophobic and at least one of which is hydrophilic, and including a crosslinkable group are provided. The macromers can be covalently crosslinked to form a gel on a tissue surface in vivo.
In the existing soft patterning techniques, broadly referred to as "soft lithography" where the created surface patterns are nearly the same length scale as the patterns on the mold or master. As an example, in the existing methods, 1 pm periodicity patterns can be created using a mold or master which also has ~ 1 um features. However, following the proposed method, using the same 1 um periodicity mold or master, final miniaturized patterns could be engineered to be anything in the range of 10 nm to 1 um.
The objective of the existing methods in the field of soft lithography is to create a replica or an imprint of an original pattern or object on another film or object. The imprint or the replica thus obtained forms at the same length scale as that of the original pattern.
Thus, the present invention combines the concepts of soft patterning and volume shrinkage to invent a new soft lithography method, which can replicate the original pattern or object with miniaturization. The novel step is to miniaturize from a larger object, which is far easier and cheaper to fabricate, rather than fabricate directly a micrometer or sub-micrometer object by specialized and expensive tools like the e-beam patterning, photolithography and Focused ion beam, etc. In fact, fabrication of 3-D and complex large area 2-D microstructures is not even possible or straightforward or cost effective by using conventional nano- or micro-fabrication methods.
OBJECTS OF THE INVENTION
The primary object of this invention is to propose a process for generating miniaturized replicas of the original pattern or an object, which is easier and cheaper to fabricate.
Another object of this invention is to propose a process for generating miniaturized replicas of the original pattern or an object which is cost effective.
The inventive steps of the present invention have been indicated in the principal claim and advantageous features are mentioned in the dependent
SUMMARY OF THE INVENTION
This invention describes a method which can create a reduced sized replica of the original pattern. The replication can take place by any of the existing soft lithography methods like molding, imprinting etc. but the novelty of the method is the ability to create replicated structures at reduced length scale than the original pattern. The miniaturization is achieved using a soft shrinkable material, which can undergo volume shrinkage. The shrunk replicas can be replicated again on a non shrinkable material and can be subsequently replicated again on a shrinkable material and shrunk further. This cycle can continue for as many number of times, depending on the extent of miniaturization desired.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings and wherein:
Figure 1: Schematic Representation of the proposed method of generating Patterns and Objects by Successive Miniaturization using Shrinkable Replicating Materials.
Figure 2: (a)-(e) A macroscopic pattern of shape "O" was miniaturized following the procedure depicted in Figure 1. In each cycle the size of the pattern could be shrunk by ~ 38%. After 4 cycles, overall reduction in size was 86% of the original size, 4 miniaturization cycles, (f)-(i) A three dimensional object is miniaturized to demonstrate that the size reduction is isotropic. The scale bars in all the images are 1 mm.

Figure 3: (a) and (d) AFM scans of the patterned aluminum foils of CD and DVD respectively, which were used as the original patterns to demonstrate the viability of the technique, (b), (c) and (e),(f) are the second and third generation shrunk and miniaturized patterns on dried shrinkable replicating material, polyacrylamide hydrogel in the respective cases.
Figure 4: Effect of initial water content of the gel pre-polymer on the extant of miniaturization. The figures show AFM images of second generation shrunk hydrogel patterns when the initial water content in the pre polymer solution was (a) 55%, (b) 70% and (c) 85% respectively. In all the cases, the first generation stamp used was a CD foil, as shown in figure 3(a), (d) The plot shows the percentage reduction in the periodicity (star) and height (circle) of the stripes in the second generation patterns. Unfilled and filled symbols represent data using a CD and a DVD foil respectively.
Figure 5: Using a CD foil as the "Original Pattern" shown in figure 3(a), different extant of shrinkage has bee achieved in different cycles by varying the solvent (water) content in the gel. Polyacrylamide Hydrogel was used as the shrinkable material with Solvent content for: (a) first cycle was 70%, which resulted in 38% shrinkage, (b) Second cycle, solvent content was 55% resulting in ~ 27% shrinkage and (c) Third cycle, solvent content was 85%, resulting in ~ 42% shrinkage. Overall shrinkage achieved ~ 73%.
Figure 6: Pattern miniaturization following the steps shown in Figure 1 and using resorcinol flormaldehyde (RF) hydrogel as the shrinkable material used was polyacrylamide based hydrogel. The original pattern was a CD foil, (a) Replica of the original pattern on non shrinkable replicating material, cross linked PDMS and (b) Replica of shrunk and dried second generation pattern on RF gel.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO ACCOMPANYING DRAWINGS
The present invention relates to a method which can create a reduced sized replica of the original pattern which can be a 2-D or a 3-D object or pattern. The replication can take place by any of the existing soft lithography methods like molding, imprinting etc. but the novelty of the method is the ability to create replicated structures at reduced length scale than the original pattern, which is shown schematically in figure 1. The process makes use of volume shrinkage characteristic of soft gels in response to specific changes in its environment. The starting first generation mould or master for the miniaturization process is either the original pattern or object to be miniaturized, or it can be a negative replica of the same in an appropriate non-shrinkable moldable replicating material such as cross-linked polydimethysiloxane (PDMS). A negative replica of this mould or master is obtained by casting a soft shrinkable material (for example, a gel pre-polymer solution like polyacrylamide containing solvent^water in the range of 20% to 90% and its subsequent cross-linking). The material is then shrunk under controlled conditions to shrink it to the desired extent. This step results in a reduced size replica of the original pattern or object. At an appropriate time during shrinkage, the replica is removed from the mould or master and shrunk further if needed. This shrunk and dried pattern or object, called the second generation pattern or object, is then again replicated with a non-shrinkable moldable material, for example, polydimethylsiloxane (PDMS). This produces the second generation pattern or object which is shrunk replica on the dried shrinkable (gel) material. These replicated and miniaturized objects or patterns on the dried shrinkable material can further be replicated again on a non shrinkable material, which can be subsequently be used as the mold or master

for the subsequent cycle and the pattern can be replicated again on a shrinkable material and shrunk further. This cycle can continue for as many numbers of times, depending on the extant of miniaturization desired, as shown in figure 1.
Figure 2 provides the example where it is demonstrated that miniaturization of macroscopic objects, having dimension in the range of several cm is possible with polyacrylamide hydrogels over multiple successive miniaturization cycles. Figure 2(a) shows the digicam image of the macroscopic pattern. The shrinkable replicating material, (a polyacrylamide gel precursor solution, in this case) was poured onto this master and was allowed to polymerize. The shrinkable material having the imprint of the original mold or master was then dried in a controlled environment for an appropriate period of time (ranging between 4 hours to 96 hours), with constant temperature (in the range of 15°C - 40°C) and constant relative humidity (in the range of ~ 10% to 90%). Under these controlled conditions, the gel sample dried slowly but uniformly without undergoing undulations and distortions at the surface. This pattern with reduced size is referred here as the second generation pattern.
A replica of the second generation pattern on the dried shrinkable material was created on a non shrinkable material by pouring elastomer such as Slygard 184 mixed with the curing agent, (for this material, the ratio of the curing agent to the main elastomer can be in the range of 2% v/v to 25% v/v) followed by de-aeration in vacuum, and subsequent curing for 1 hour to 36 hours at elevated temperature of 30°C to 140°C. In Sylgard 184 used, curing is carried out by

keeping the sample, at elevated temperature in an oven as noted above, which cross-links the mixture and makes it an. elastic .solid. Curing of other moulding materials may however follow a different route for example curing in some materials may be by UV exposure, etc.After peeling off, the crosslinked block of PDMS, having the imprint of this second generation pattern was used as the master in the next cycle to achieve subsequent pattern miniaturization.
Figure 2(b)-(f) show the gradually miniaturized patterns which were obtained in successive generations by continuing the process over several cycles. For example, figure 2(b), which shows the original master pattern has a characteristic lengthscale of 15 mm/However, figures 2(c)-(f), which represents the miniaturized patterns generated after every cycle, shows approximately ~ 35% shrinkage in each cycle, which finally resulted in upto ~ 90% overall reduction compared to the original master. Furthermore reduction in size was isotropic which ensures no shape change for three dimensional objects. This is demonstrated in figures 2(g)-(j) in which a hexagonal block was miniaturized although the angle between any two planes remained unaltered.
The ability of the invented method to miniaturize 2 -D patterns with sub micron and micron size and periodicity engraved on flexible substrates is demonstrated in figure 3. Figure 3(a) and 3(d) show the atomic force microscope (AFM) images of patterns on the protective Aluminum foils of a commercially available CD and DVD, which were used as the original master here. Figure 3 shows also the typical patterns which were obtained in two successive cycles of the above process performed on the patterns from CD and DVD which resulted in ~ 35%

reduction in size depending in each cycle. For example, gel pre-polymer solution was used containing 55% water onto a CD foil having stripes with periodicity and height of 1.5 um and 110±5 nm respectively. After implementing the above miniaturization process, the periodicity of the second (figure 3(b)) and the third (figure 3(c)) generation patterns were 961±17 nm and 638±12 nm respectively. Thus the extent of miniaturization in the two consecutive cycles was ~ 36% and ~ 34.5% respectively. The height of the stripes also reduced from the original 110 nm to 74±6 and 52±3 nm respectively. Similarly, using a patterned DVD foil as the master (periodicity and height of stripes: 800 nm and 65±3 nm respectively), the periodicity of the second and third generation patterns were 531±14 nm (figure 3(e) and 359±7 nm (figure 3(f) respectively. The height of the stripes also reduced from 65 nm to 44±4 nm and then further to 30.2±3 nm respectively which decreased to and (figure 3(f)) after the next cycle. Thus the overall reduction in length scale of the patterns was -56%. However, the miniaturization could be achieved over a large area (~ cm2).
Figure 4 demonstrates how the miniaturization achieved in each cycle if affected by the initial solvent content (water, in this case) of the gel pre - polymer solution. Typical second generation miniaturized patterns obtained using a CD foil as the original stamp (figure 3(a)) is shown in figures 4(a) - 4(c), when the initial water content was 55%, 70% and 85% respectively. Furthermore, the plot in figure 4(d) shows that the percentage reduction in periodicity and the height of the stripes at any water content of the gel was nearly identical for both the CD and the DVD patterns, emphasizing the isotropic nature of the shrinkage.

The images demonstrate the extent to which miniaturization of' the pattern could be enhanced by increasing the initial water content in the pre-polymer solution, but without limiting to the same.
Figure 5 demonstrate s that a greater control on the desired extent of overall shrinkage can be achieved by tuning the shrinkage at each step. In this case, a CD foil was used as the original stamp, with 1.5 um periodicity and a 70% solvent containing gel pre polymer solution was used for the first cycle, resulting in ~ 40% miniaturization. In the second cycle, a 55% solvent containing gel pre-polymer solution was used in the second shrinkage cycle, which resulted in ~ 35% reduction. The periodicity of the final pattern was ~ 589 ± 3 nm, which indicated that -61% overall shrinkage could be achieved.
Figure 6 demonstrates that the method of present invention is not only limited to the use of polyacrylamide based hydrogels (PAA) as the only shrinkable material that could be used, as it is demonstrated that similar miniaturization is possible with another variety of volume shrinkable gel material such as the resorcinol formaldehyde hydrogels. This example demonstrates the material independent nature of the invented method.
The main advantages of the present invention are:
1. The proposed method, in conjugation with existing soft .lithography methods like molding, imprinting, embossing etc. can be used to generate features which are smaller than the feature size of the original master pattern. This concept can be extremely useful, as patterns with smaller periodicity and line width which are inherently difficult and costly to fabricate can be obtained starting from a master having much higher feature size.

2. In the proposed method, the initial pattern can be a 2 -D or a 3 - D
pattern or object. Of particular interest is the ability to miniaturize large 3
-D objects in a wide range of length scales: macroscopic to sub-micron,
can be generated without using any sophisticated tools or equipment.
3. The proposed method can create miniaturized replicas of objects sub-
rnicron (few nm) to macroscopic (several centimeters) dimensions.
4. The length-scale of the final 3D object or pattern generated can be
significantly smaller than that of the initial master pattern or object.
5. Starting from the same original object or pattern, multiple replicas having
different length scales can be simultaneously produced, in different cycles.
6. Large area submicron patterning of wide range of soft surfaces without
using any specially designed tool or equipment.
7. The proposed method is general irrespective of the material type of the
initial pattern or object, as it can be made of polymers, glass, ceramic or
metal.
8. The proposed method is general irrespective of the structural rigidity of the
initial pattern or object, as it can be rigid or flexible.
9. Successive steps of replication or molding and miniaturization are used
intelligently.
10. The 3D object or the pattern generated at each stage can be
used as a potential mask or mold for other lithographic methods of
generating patterns.
11. In the proposed method, the initial pattern can be engraved on a planar
or a curved substrate.

12. The extent of miniaturization can be controlled by varying the initial solvent content of the starting shrinkable material and rate and time of drying as well as the number of miniaturization cycles. In the proposed method, the miniaturization can be isotropic or anisotropic, depending on the "controlled conditions" used for drying.
Probable areas of application of the patterned surfaces using the present invention:
In general, the invention will be useful for micro- and nano- fabrication which is the central application in all the areas related to nanotechnology. Topographically patterned surfaces, moulds, masks and stamps having sub micron and nanometer scale resolutions are important to a host of scientific and commercial applications like components of electronics, optical devices, scaffolds for tissue engineering, biological, and chemical sensors, patterned adhesives, carbon-MEMS/NEMS, microbattery, etc. In all these areas, the greatest challenge is to create structures with ever increasing smaller feature sizes and periodicity inexpensively. For example: photolithography, typically produces feature sizes greater than about one micron and certainly cannot produce sub-100 nm structures because of diffraction limits. Next generation lithography methods, like e-beam lithography and FIB milling require sophisticated and costly instruments for mask and mould making at sub-micron scales.
The proposed invention offers a new method for the creation of patterns with smaller periodicity and sizes, starting from large molds or masters, thereby offering reduced fabrication costs, especially for sub-micron objects.

Specifically, the invention will be useful for the areas listed below, without limiting to the same.
• Micro patterning of polymer surfaces for Biomaterials applications.
• Surfaces for nano-biotechnology applications like biochemical sensors, drug
delivery, tissue engineering, single molecule enzymology, proteomic or
genomic arrays, photodiode arrays for sub retinal implant and patterned
substrates for probing of cell behavior etc.
• Fabrication of diffraction gratings/optical wave guides.
• Confined chemistry applications.
• Application in the areas of microfluidics, for example for fabrication of large
number of parallel micro channels, starting from a easy to fabricate
macroscopic mold, which may be fabricated in a workshop rather than a
micro fabrication facility.
• Creating of surfaces with structural colors.
• Fabrication of patterned "smart" adhesives and super adhesive surfaces
with possible "clean" peeling options.
EXAMPLES
EXAMPLE 1:
Miniaturization of Macroscopic objects using multiple successive
miniaturization cycles using polyacrylamide hydrogels.
Figure 2 provides the example where it is demonstrated that miniaturization of macroscopic objects, having dimension in the range of several cm is possible with polyacrylamide hydrogels over multiple successive miniaturization cycles. Figure 2(a) shows the digicam image of the macroscopic pattern in the shape of the English alphabet "O". The gel precursor solution was

poured onto this master and was allowed to polymerize for about 15 minutes. The hydrogel sample having the imprint of the master was then dried in a controlled environment of 28°C temperature and 60% relative humidity at which the gel sample dried slowly but uniformly without undergoing undulations and distortions at the surface. This pattern with reduced size, referred here as the second generation pattern, was used as the master in the next cycle to achieve subsequent pattern miniaturization. However, this dried piece of hydrogel containing the second generation pattern could not be directly used as the master, because the gel pre-polymer solution swells the dry gel and thereby damages the pattern. Instead, a non-polar crosslinkable Sylgard 184 elastomer (PDMS) was first used to develop the master for the next cycle. The Sylgard 184 elastomer mixed with the curing agent (10:1 v/v), de-aerated in vacuum, was poured onto the dried sample and cured for about an hour at 80°C. After peeling off, the crosslinked block of PDMS, having the imprint of this second generation pattern was used as the master for the next cycle. However, since the PDMS surface was non-wettable by the pre-polymer solution it led to poor fidelity of the imprinted patterns, particularly near to the sharp corners. Hence, in order to ensure complete wetting, the PDMS stamp was plasma oxidized at 0.05 torr pressure for about one minute inside a plasma chamber.
Figure 2(b)-(f) show the patterns which were obtained in successive generations of the above process. Whereas figure 2(b), having a characteristic lengthscale of 15 mm, represents the master or the first generation pattern, figures 2(c)-(f) represent the ones of the subsequent cycles. Here, reduction in size of 35-45% (by length) was achieved in each cycle which finally resulted in about 86% reduction from the initial size of the master. Furthermore reduction in size was isotropic which is essential for miniaturizing three dimensional objects. This is demonstrated in figures 2(g)-(j) in which a hexagonal block was miniaturized although the angle between any two planes remained unaltered.

This example demonstrates that substantially reduced sized replicas of macroscopic objects and patterns, including 3-D objects can be achieved by the invented method, without a change in shape of the original objects and the replicas. It also shows that depending on the number of cycles used for shrinkage, miniaturized replicas of different length scales can be obtained from the same original mold or master. EXAMPLE 2:
Miniaturization of Microscopic Patterns engraved on flexible surfaces using multiple successive miniaturization cycles using polyacrylamide hydrogels.
The ability of the invented method to miniaturize 2 -D patterns with sub micron and micron size and periodicity engraved on flexible substrates is demonstrated in figure 3. Figure 3(a) and 3(d) show the atomic force microscope (AFM) images of the periodic stripes on the protective Aluminum foils of a commercially available CD and DVD, which were transferred and miniaturized by the method described in figure 1. For pattern transfer, a piece of the foil was gently peeled off the polycarbonate backing of a CD/DVD and was subsequently attached to a rigid support and placed on the gel pre-polymer solution in a container. The polymerization reaction was complete within 15 minutes. The crosslinked block of gel was subsequently cooled down to normal temperature and the aluminum foil was removed from the surface of the hydrogel, leaving behind an imprint of the pattern. This block of hydrogel was then dried in a controlled condition similar to that for miniaturization of macroscopic patterns. Figure 3 shows also the typical patterns which were obtained in two successive cycles of the above process performed on the patterns from CD and DVD which resulted in 30% -50% reduction in size depending on the initial content of water in the gel. For example, we used gel pre-polymer solution containing 55% water onto a CD foil having stripes with periodicity and height of 1.5 um and 110±5 nm respectively. After implementing the above miniaturization process, the periodicity

of the second (figure 3(b)) and the third (figure 3(c)) generation patterns were 961±17 nm and 638±12 nm respectively. Thus the extent of miniaturization in the two consecutive cycles was ~ 36% and ~ 34.5% respectively. The height of the stripes also reduced from the original 110 nm to 74±6 and 49±3 nm respectively during this process. Similarly, using the pattern on DVD as the master (periodicity and height of stripes: 800 nm and 65±5 nm respectively), the periodicity and height of the second generation patterns were 531±14 nm and 44±4 nm respectively (figure 3(e)) which decreased to 359±7 nm and 30.2±3 nm (figure 3(f)) after the next cycle. Thus the overall reduction in length scale of the patterns was -56%. Importantly, this reduction in size could be easily achieved within an area of 1cm x 1cm.
EXAMPLE 3:
Controlling the Extant of miniaturization by varying the solvent content in the shrinkable material (using polyacrylamide hydrogels):
The ability to control the desired extant of shrinkage by varying the initial solvent content of the shrinkable material is demonstrated in figures 4 and 5. While in figure 4 the effect of initial solvent content on the shrinkage is demonstrated, figure 5 elaborates the example where the solvent content in the shrinkable material can be varied or tuned in each cycle to tailor the extant of shrinkage achieved at each shrinkage step.
Figure 4(a)- 4(c) represent the typical example of second generation patterns developed by using 55, 70 and 85% water containing gel. Whereas the reduction in size was more for the 85% water containing gel, the transfer of pattern was somewhat unsatisfactory as it led to the appearance of few defects. The pattern

transfer and its reduction was however perfect when a gel with lower water content of ~ 50% - 70% was used. Furthermore, the plot in figure 4(d) shows that the percentage reduction in periodicity and the height of the stripes at any water content of the gel was nearly identical for both the CD and the DVD patterns, emphasizing the isotropic nature of the shrinkage. The images demonstrate that the extents miniaturization of the pattern could be enhanced by increasing the initial water content in the pre-polymer solution, but not without a limit.
Figure 5 demonstrate s that a greater control on the desired extant of overall shrinkage can be achieved by tuning the shrinkage at each step. For example, it is desired to create a stripe pattern with a precise periodicity of 585 nm and for the purpose an original mold with 1.5 um periodicity is available. Starting from the original mold, if the solvent content in the gel pre-polymer solution is kept 55% at each cycle, the periodicities of the second and third generation replicas will be ~ 975 nm and 630 nm respectively, as ~ 35% shrinkage is achieved for a 55% solvent gel pre polymer solution (figure 4(d)). Similarly, if a 70% solvent containing gel pre-polymer solution is used for both the cycles, the respective periodicities will be - 900 nm and 540 nm, assuming ~ 40% shrinkage for 70% solvent containing gel. Similarly in case of an 85% solvent containing gel pre-polymer solution, which will result in ~ 45% shrinkage (figure 4(d)), the periodicities of the first and second generation patterns will be 825 nm and 450 nm respectively. Thus a desired target of 585 nm periodicity pattern cannot be achieved following this strategy. However, if a 70% solvent containing gel pre polymer solution is used for the first cycle (~ 40% reduction; expected second generation periodicity: 900 nm) and a 55% solvent containing gel, pre-polymer solution is used in the second shrinkage cycle (~ 35% reduction; expected second generation periodicity: 585 nm) then the desired dimensions can be

achieved by controlled miniaturization. This example is shown with the help of AFM scans in figure 5, where 589 ± 3 nm periodicity patterns has been successfully created by controlling and varying the concentrations of the solvent in the gel pre - polymer solution at each shrinkage step.
EXAMPLE 4:
Miniaturization of Microscopic Patterns engraved on flexible surfaces using multiple successive miniaturization cycles using resorcinol flormaldehyde hydrogels.
The ability of the invented method to miniaturize patterns with resorcinol flormaldehyde hydrogels is demonstrated in figure 6. Similar to the experiments in figure 3, a patterned CD foil was used as the original stamp. Slow drying of the wet gel over three days resulted in miniaturized patterns having periodicity and height of the stripes of 743±11 nm and 53±5 nm respectively; i.e. isotropic shrinkage of the order of ~ 50% could be achieved in one cycle.
It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention, which is further set forth under the following claims:-

WE CLAIM
1. A process for generating miniaturized replicas of a 2D or 3D pattern or an
object comprising steps of :
- replicating original shape of the pattern or an object into a soft
shrinkable material,
- miniaturization by shrinkage followed by repeatation of said
procedure until the desired degree of miniaturization.
2. A process as claimed in claim 1 comprising steps of:
- replication of shrunk object or pattern in non-shrinkable material
and
- replication in shrinkable material followed by miniaturization,
which may be repeated until the desired degree of miniaturization is
achieved.
3. A process as claimed in claim 1 or 2 wherein the step of shrinkage is
carried out under controlled conditions of constant temperature of 15-40°C and constant relative humidity of approximately 10-90%.
4. A process as claimed in any of the preceding claims comprising of two
dimensional/patterned substrate or surface or a three dimensional object as the initial mould or master.

5. A process as claimed in any of the preceding claims wherein the pattern is
engraved on a planer or a curved substrate, which is a three dimensional object.
6. A process as claimed in any of the preceding claims wherein the pattern
or object may have sub-micron (few nm) to macroscopic (several centimeters) dimensions.
7. A process as claimed in any of the preceding claims wherein the pattern
or object may be rigid or flexible, which is made of for ex: polymers, glass, ceramic and metal.
8. A process as claimed in any of the preceding claims wherein the non-
shrinkable molding material is a molding or imprinting material for example: cross-linked polydimethylsiloxane (PDMS) and gelatin and soft shrinkable material is for example- a gel or a hydrogel like acrylamide, hydrogel, resorcinol - formaldehyde hydrogel etc.
9. A process as claimed in any of the preceding claims wherein the soft
shrinkable material is shrunk by removal of solvent, for example by evaporation, solubilization,. heating or any other specific process appropriate for the material, for example, pH, ionic strength, temperature for specific hydrogels responsive to these stimuli.

10. A process as claimed in any of the preceding claims wherein the
miniaturization may be isotropic or anisotropic and extent of which
can be controlled by any one or a combination of the following steps:
i. by varying the initial content of solvent in the soft shrinkable material used for miniaturization,
ii. by varying amount of solvent removed from the shrinkable material iii. by varying the solvent removal rate.
11. A process as claimed in any of the preceding claims wherein the replica
of the second generation pattern on the dried shrinkable material is
created on non shrinkable material by pouring elastomer such as
sylgand!84 mixed with a curing agent in a ratio of for example 5 % v/v
followed by de-aeration in vacuum and curing for about an hour at for
example 80°C.