GB2493817A - Rewritable photopatterning - Google Patents

Abstract

A method of photopatterning rewritable reactive groups onto surfaces using typically a plasmachemical deposition of functionalized polymer material, followed by molecular printing of inks on the polymer surface. Subsequent treatment of the reactive groups allows for surface rewriting and also the method allows for the creation of either positive or negative image multifunctional rewritable patterned surfaces. An example of a functionalized surface comprising anhydride reactive groups to which a functional molecular dye (cresyl violet perchlorate) is attached. The dye molecules may be selectively attached and detached to provide a rewritable photopattern.

Description

A Method of Producing a Functionalized Surface and Surfaces made thereby

Field of the Invention

The current invention relates to a method of producing a functionalized surface and in particular but not exclusively to patterned functionalized surface that can be rewritten. Furthermore the invention relates to functionalized surfaces made by the method described.

Background of the Invention

Patterned functional surfaces are widely used for a whole host of applications including integrated optics, engineering templates, sensor arrays, nano-electronic devices and cellular interactions. An important attribute which is often sought is directed rewritability, which although well established for bulk materials such as holographic image storage, electronic memory devices, thermal recording materials, photo-detectors, inks, and optical data storage it remains a challenge for surface molecular printing.

For instance, dye attachment to surfaces is of relevance to molecular lattice devices, organic photoreceptors, clinical immunoassays, specific cell marking (dye-protein interactions), and genetics ((lye-DNA interactions). However, currently there only exist non-rewritable methods for dye patterning onto solid surfaces; for example, soft-lithography, UV irradiation, and ink-jet printing. In each case, the dye molecule is reacted with functional groups already present at the surface (which have normally been prepared by a substrate-dependent multistep procedure).

The present invention seeks to overcome the problems of the prior art by providing patterned functionalized surfaces that can be deposited easily onto surfaces, and which can be re-written.

Summary of the Invention

According to a first embodiment of the invention there is provided a method of producing a patterned functionalized surface, the method involving: (i) contacting a surface with a plasma polymer having reactive groups so the groups are deposited on the surface to produce a fiinctionalized polymer layer on said surface; and (ii) contacting the functionalized polymer layer with a flinctional molecule that reacts with the ffinctionalized polymer layer to produce a patterned surface having one or more areas of reactive surface functionality.

It is envisaged that the substrate for the surface can be any solid material. An example of the substrate material is any solid, particulate, permeable and/or porous substrate or finished article, consisting of any materials (or combination of materials) as are known in the art. Examples of materials include, but are not limited to, woven or non-woven fibres, natural fibres, synthetic fibres, metal, glass, ceramics, semiconductors, cellulosic materials, paper, wood, or polymers such as polytetrafluorocthylcnc, polyethylene or polystyrene. In particular the solid material may by silicon.

It is envisaged that the polymer is formed by plasma polymerization, thermal chemical vapour deposition, initiated chemical vapour deposition (iCVD), photodeposition, ion-assisted deposition, electron beam polymerization, gamma-ray polymerization, target sputtering, graft polymerization, or solution phase polymerization. Preferably the polymer is formed by plasma deposition and in particular by pulsed plasma deposition, It is envisaged that the reactive group is an anhydride and in particular the anhydride is plasma deposited using maleic anhydridc precursor. Individual anhydride precursors may be used or combinations of compounds which have groups that can be flinctionalized.

It is preferred that the functional molecule dye, such as a nucleophile containing ink and this ink is typically cresyl violet pcmhloratc. Individual or combinations of dyes/inks may be used.

It is prefeffed that the functionalized polymer layer is polymerized prior to contacting with the dye as in step (ii).

It is envisaged that the patterned surface is produced by irradiating the functionalized polymer layer in discrete areas prior to contacting said layer with one or more dyes.

Tn an alternative situation the patterned surface is produced by irradiating the functionalized polymer layer after contacting said layer with the dye.

Tt is envisaged that irradiation is undertaken using a beam of plasma, photons, electrons, ions, radicals, atomic species, or molecular species. Preferably the radiation is (iv irradiation and typically the pattern is produced by irradiating through a mask. The pattern may be produced using a focused irradiation source.

In a preferred arrangement the patterned functionalized surface is erasable to allow rewriting of the patterned functionalized surface.

It envisaged that the surface density of the groups or dye on the surface is controlled by varying the plasma cycle, typically the plasma duty cycle.

Typically, the patterning of the surface is negative or positive image liv patterning.

According to a further embodiment of the invention there is provided a method of producing a functionalized polymer layer to be patterned according to any preceding claim, the method involving contacting a surface with a plasma polymer having reactive groups so the groups are deposited on the surface to produce a functionalized polymer layer on said surface.

According to another embodiment of the invention there is provided a thnctionalizcd patterned surface produced by a method according to any one of the preceding claims.

In yet a further embodiment there is provided a functionalized polymer layer produced by a method according to claim 22.

It is envisaged that a functionalized patterned surface or flinctionalized polymer layer according to the embodiments of the invention are used in molecular lattice devices, organic photoreceptors, clinical immunoassays, specific cell marking (dye-protein interactions), and genetics ((lye-DNA interactions).

Furthermore, the ftmctionalized patterned surface or functionalized polymer layer can be included in kits including molecular lattice devices, organic photoreceptors, clinical immunoassays, specific cell marking (dye-protein interactions), and genetics (dye-DNA interactions).

The invention has particular advantages in that it allows for nucleophile containing ink molecules to be patterned onto pulsed plasma deposited maleic anhydride nano-film surfaces.

Both positive and negative rewritable images can be created by utilising liv lithography in combination with chemical regeneration of surface anhydride groups as a typical method of using the invention.

Brief Description of the figures

An embodiment of the invention will be described with reference to and as illustrated in the accompanying figures by way of example only, in which: Figure I shows: Infrared spectroseopy: (a) reflection-absorption spectra of deposited maleic anhydride pulsed plasma polymer; (b) absorbance spectra of eresyl violet perchlorate dye; and (c) reflection-absorption spectra of plasma polymer functionalised with cresyl violet perehlorate dye; Figure 2 shows: negative image UV patterning of surface immobilised cresyl violet dye; Figure 3 shows: positive image UV patterning of surface immobilised cresyl violet dye molecules using anhydride group regeneration step; Figure 4 shows: optical and fluorescence microscopy images of liv patterned surfaces of cresyl violet perchloratc dye molecules attached to maleic anhydridc pulsed plasma polymcr: (a) negative patterning and (b) positive patterning; Figure 5 shows: infrared reflection-absorption spectra of: (a) deposited maleic anhydride pulsed plasma polymer; (b) plasma polymer functionalised with 4-ethylaniline; (c) plasma polymer functionalised with 4-ethylaniline and heated at 120° C; (d) UV irradiation and hydrolysis of (c); (e) regenerated anhydride group; and (f functionalization of (e) with cresyl violet perchlorate dye.

Figure 6 shows: a schematic method showing the re-writable property of the maleic anhydride pulsed plasma polymer film surfaces.

Figure 7 shows: (a) bifunctional patterned surface via UV exposure of surface immobilised Dye I (cresyl violet perehlorate) molecules followed by regeneration of anhydride groups and immohilisation of Dye 2 TTiLyte Fl ilor 488 amine) molecules (b) Corresponding fluorescence microscopy image showing cresyl violet perchlorate (red) and HiLyte Fluor 488 (blue) dye molecules attached to maleic anhydride pulsed plasma polymer Detailed Description of Embodiments of the Invention In general the invention involves film formation where there is generation of active sites (predominantly radicals) at the substrate surface and within the electrical discharge during the short plasma duty cycle on-period (microseconds). This process is followed by conventional polymerization reaction pathways proceeding during each prolonged extinction off-period (milliseconds) to yield well-defined poly (maleic anhydride) nano-fllms. The reactive surface anhydride functionalities can then be employed to tether functional molecules (for example dyes such as cresyl violet perchlorate. Furthermore, the rewritablc patterning of these surfaces is demonsttatcd by subsequent IJV lithography to facilitate the removal of immobilised molecules and regeneration of reactive anhydride groups in readiness for the next write step. This methodology provides scope for the fabrication of either positive or negative image patterned functional surfaces. Some inherent advantages of this approach include the fact that the plasmachemical surface functionalization step is substrate independent (due to thc activating nature of the elcctrical discharge) and also the surface density of tethered molecular species can be finely tuned by varying the pulsed plasma duty cycle.

Deposition of Anhydride Functionalized Nano-layers Briquettes of maleic anhydride (Aldrich, +99%) were ground into a fine powder and loaded into a glass monomer tube prior to attachment to an electrodeless cylindrical glass plasma reactor (4.5 em diameter, 460 cm3 volume, base pressure of 5 x 10 mbar, with a leak ratc lower than 1.0 x 10 kgs-') enclosed in a Faraday cage. This was fitted with an externally wound copper coil (4 mm diameter, 9 turns, spanning 8-15 cm from the gas inlet), a thermocouple pressure gauge, and a L mini twostage rotary pump connected to a liquid nitrogen cold trap. All joints were greasefree. An L-C circuit matched the output impedance of the RF power generator (13.56 MHz) to that of the partially ionised gas load. Pulsed plasma deposition entailed triggering the RF power supply from a signal generator. The pulse width and amplitude were monitored with an oscilloscope. Prior to each experiment, the reactor was cleaned with detergent and then a 30 mm high-power (50 W) air plasma treatment. Next, the chamber was vented to air and a piece of silicon substrate (MEMC Electronic Materials, +99.9%) was placed into the centre, followed by evacuation back down to base pressure. At this stage, maleic anhydride vapour was introduced into the reactor at a constant pressure of 0.2 mbar, followed by plasma ignition. The optimum deposition conditions corresponded to power (P) = 5 W, pulse on-time (iou) = 20 jis, off-time (tof4 = 1200 s, and total deposition time = 30 mm. Upon plasma extinction, the RF supply was switched off and the monomer feed is allowed to continue flowing through the system for a ifirther 5 mm prior to evacuating to base pressure.

The deposited maleic anhydride pulsed plasma polymer film thickness was estimated by refleetometry to be 92 5 nm. XPS analysis indicated five types of carbon functionality in the C(ls) envelope: hydrocarbon (CH.= 285.0 eV), carbon singly bonded to an anhydride group (C-C(O)-O-285.7 cv), carbon singly bonded to oxygen (-C-O 286.6 eV), carbon doubly bonded to oxygen (O-C-O/-C0 287.9 eV), and anhydride groups (0C-O-C=O 289.4 eV), Complete coverage of the underlying silicon substrate was confirmed by the absence of any Si(2p) signal showing through;.

Infrared analysis confirmed structural retention of the anhydride groups in the pulsed plasma deposited layers and this is shown in Figure 1. The following characteristic cyclicanhydride absorbances were identified: asymmetric and symmetric C=O stretching (1860 cm1(A) and 1796 cm' (B)), cyclic conjugated anhydride group stretching(1241 cm'(N)) and 1196 cm(O)), C-O-C stretching vibrations (1097 cm' P) and 1062 cm' (S)), and cyclic unconjugated anhydride group stretching (964 cm', 938 cm' and 906 cm' (U)).

Inclusion of Dyes Attachment of dyes to the surface of the functionalized layer entailed immersion of a piece of pulsed maleic anhydride plasma polymer coated substrate into a I x l0 M solution of cresyl violet perehlorate (+99.9%, Aldrich) dissolved in anhydrous N,N-dimethylformamide (+99.9%, Aldrich) for I hour (this solvent avoids the hydrolysis of anhydride groups1o). Afterwards, the surface was rinsed with N,N-dimethylformamide and dried under a stream of nitrogen. For bifunctional patterning, HiLyte Fluor 488 amine dye (Cambridge Bioscence) was used in a similar fashion.

The cresyl violet perchlorate dye molecule (which contains amine groups) displays two intcnsc bands in the infrared absorption spectrum 1591 cur' (NH bending (F)) and 1335 cm' (C-N stretching / C-N-H bending of the amine groups (K)) as shown in Figure 2. A number of other characteristic absorbances were also identified for this molecule: 1649 cur', 1544 cm', 1514 cm', 1485 cm', 1435 cm', 1308 cm', 1298 cm', 1129 cur', 1093 cur', 1076 cur', 1004 cm, 856 cur', 845 cur', 818 cm', and 776 cm'.

Tmmersion of the maleic anhydride pulsed plasma polymer layer into a solution of cresyl violet perchlorate dissolved in N,N-dimethyl formamide gave rise to dye attachment at the surface via amide linkages (aminolysis reaction) and electrostatic acid-base interactions and negative patterning is shown in Figure 2. Infrared spectroseopy confirmed the presence of: amide groups (amide I at 1656 cm' (D) and amide II at 1553 cm' (F)), carboxylic acid stretching (1721 cm' (C)), and C-NH monosubstituted amide stretching (1470 -1420 cm' (I)). The accompanying acid-base interaction arising from the other amine group in the dye molecule manifests in the symmetric COO-stretching band(1405 cm' (J)). An absence of the NH2 bending mode (1520 cm-i) and presence of only the NHf; bending mode (1591 cm-i (E)) is consistent with aminolysis occurring at only one end of the dye molecule, in addition, the following fingerprint associated with the cresyl violet dye molecule were observed: 1514 cm-' (G), 1485 cm' (H), 1335 car' (K), 1308 cm" (L), 1298 cm' (M), 1093 car' (Q) 1076 cm" (R), 1004 car' (1), 856 cm' (V), 845 cm' (W), 818 cm'(X) and 776 cm'(Y).

The continued presence of background maleie anhydride pulsed plasma polymer infrared bands (1860 cm1 (A), 1796 cm' (B), 1241 cmt (N). 1196 cm' (0), 1097 cm' (P), 1062 cm-' (S) and 938 cm' (U)) confirmed that reaction had only taken place at the solid-solution interface.

A corresponding change in the elemental XPS composition was found at the plasma polymer surface following exposure to cresyl violet perchlorate solution. The absence of any chlorine signal originating from the parent cresyl violet molecule is consistent with the model depicted in Figure 2. An accompanying change in the C(ls) envelope was also evident comprising hydrocarbon (CR 285.0 cv), carbon singly bonded to an amide / carboxylic acid groups (CH7C(OJNHR / CH2C-(0)OH -285.6 cv), amine groups (C-NH2 286.0 cv), carbon singly bonded to oxygen (-0 286.4 cv) amide groups (RNH-C0 287.9 eV), and anhydride / carboxylic acid / carbonyl groups (0ç-O-cO / C(0)OH / C(O)O-289.4 cv). Whilst two types of nitrogen functionality were identified in the N( Is) spectrum: amide linkage groups / nitrogen atom belonging to the central dye molecule ring (RNH-C=0 / C-N=C -399.8 cv), and the counter-ion (C=NH2-400.8 cv), in accordance with the expected 2: I stoichiornctric ratio.

Surface Patterning Surface patterning entailed uv irradiation (Hg-Xe lamp. Model 6136, Oricl Corporation) through a copper mask (5 pm grid width, with 20 pm x 20 m open squares, Agar Scientific Ltd) for 1 hour in ambient air. For the biflinctional dye patterns, nickel masks were used (2000 mesh: 7.5 p.m open squares, 5 p.m bar width, Agar Scientific Ltd). In the case of negative image generation, U_V photopatterning of the maleic anhydride plasma polymer surface worked for both prior to or following dye molecule immobilisation, as shown in Figure 2.

Whilst in the case of positive image formation Figure 3, the maleic anhydride pulsed plasma polymer film was first capped by aminolysis with 4-ethylaniline (Aldrich, 98%) vapour at 1 mbar pressure in a sealed glass chamber at 20 °C for 45 mm. The whole apparatus was then pumped back down to base pressure, and the thnctionalized substrate placed into an oven at 120 °C for 2 hours to facilitate imidization. The surface was then UV photopatterned, rinsed in ultra purified water (30 mm) and dried under a stream of nitrogen. Re-activation of the UV-exposed areas consisted of dipping the substrate into a solution of 0.1 M trifluoroacetic anhydride (Aldrich, +99%) and 0.2 M triethylamine (Aldrich, 99.5%) dissolved in anhydrous N,Ndimethylformamide for 20 mm, and then rinsing in dichloromethane followed by drying under nitrogen. The regenerated surface anhydride groups were then ready for further chemical reactions and a schematic of this is shown in Figure 6.

Film thickness measurements were carried out using a spectrophotometer (nkd-6000, Aquila Instruments Ltd.). The obtained transmittance-reflectance curves (350 -1000 nm wavelength range) were fitted to the Cauchy model for dielectric materials using a modified Levenberg-Marquardt method.

XPS analysis was undertaken using a VG ESCALAB MKII electron spectrometer equipped with an unmonochromated Mg Ku X-ray source (1253.6 e\T) and a concentric hemispherical analyser.

Photo emitted electrons were collected at a take-off angle of3O° from the substrate normal, with electron detection in constant ana'yser energy mode (CAB = 20 cv). The C(ls) envelopes were fitted to Gaussian components with equal full-width-at-half-maximum using a Marquardt computer algorithm. Instrumental sensitivity (multiplication) factors were taken as C(Is) :O(ls): N(ls) Cl(2p) equals 1.00:0.36:0.60:0.34 respectively.

A FTTR spectrometer (Perkin-Fimer Spectrum One) equipped with a liquid nitrogen cooled MCT detector and p-polarization variable angle accessory (Speeae Ltd) was used for reflection-absoiption (PAIRS) measurements. The incident infrared beam was set at an angle of 66° from the substrate normal, and all spectra were acquired at 4 em-' resolution over 256 scans.

Sessile drop contact angle measurements were carried out using a video capture apparatus (A.S.T. Products VCA2500XE) with 2 R' high purity water drops and averaged over 5 readings.

Fluorescencc mapping for the monofirnetional cresyl violet dye patterns was performed using a Raman microscope (Labram, Jobin Yvon Ltd). The Ne-He laser (632.8 nm line, 20 mW power) beam was scanned across the substrate surface using 1.0 m steps to give a fluorescence map.

The backscattering configuration of the instrument allowed the simultaneous acquisition of both Raman and fluorescencc signal. In the case of the bifunctional dye patterns, fluorescence microscopy was performed using an Olympus IX-70 microscope driven by the SoftWorx package system (DeltaVision RT, Applied Precision). Image data was collected using excitation wavelengths at 488 nm and 633 nm corresponding to the absorption maxima of the dye molecules, Hilyte Fluor 488 amine and cresyl violet perehlorate respectively as shown in Figure 7.

Negative Image Patterning Exposure of the cresyl violet perchlorate functionalised maleic anhydride plasma polymer surface to UV light through a photomask in air gave rise to localized destruction (oxidation) of immobilised dye species which were removed by subsequent rinsing in N,N-dimethylformamidc, Figure 2 and Figure 4. Pattcrncd 20!tm x 20 m squares were clearly distinguishable by optical microscopy, where the bright areas correspond to UV irradiation and the dark regions arc unexposed (non-degraded). The patterned surface was also mapped using fluorescence microscopy, since the cresyl violet pcrchlorate dye fluoresces at an excitation maximum of 637 nm to produce an emission maximum at 654 nm. Fluorcsccnce imaging of the patterned surface confirmed crcsyl violet perchlorate dye attachment onto the malcic anhydride pulsed plasma layer only in the UV unexposed regions. The optical and fluorescence images were found to be complcmcntaiy to each other as shown in Figure 4. Similar features were observed if the maleic anhydride plasma polymer surface was UV-patterned prior to immersion in cresyl violet pcrchlorate solution.

Rewriting and Positive tmage Patterning Reaction of 4-ethylaniline vapour with the deposited maleic anhydride pulsed plasma polymer surface gave rise to ring opening of the cyclic anhydride centres to yield amide linkages (amide 1 at 1658 cm1 (0), amide II at 1563 cm' CIi) and CN-H monosubstituted amide (1490 -1400 cm' (1)), and carboxylie acid groups (1721 ear' (F)). Once again, reaction appeared to be restricted to just the near-surface region (i.e. background maleic anhydride pulsed plasma polymer infrared features remain). Heating to 120 °C gave rise to cyclic imide formation, as seen by attenuation of the characteristic amide and acid absorption bands in conjunction with the emergence of two imide stretching bands at 1777 cm1 (J) and 1711 cm' (K).

Infrared analysis following UV exposure and then rinsing in water of these imide fiinctionalized surfaces indicated a drop in intensity of the asymmetric and symmetric maleic anhydridc group C=O stretching bands (1860 cm' (A) and 1796 cm' (B)) and the appearance of a strong new band at 1730 cm' (L) attributable to overlap between C=O stretching features of non-hydrogen bonded and hydrogen bonded carboxylie acid centres. There was also a broad absorbance centred at 1411 cm' (M) belonging to COO-symmetric stretching vibrations. Further reaction with trifluoroacetic anhydride resulted in the feature centred at 1730 cm' (L) losing intensity to be replaced by two characteristic anhydride group absorption bands at 1859 cm' (N) and 1790 cm' (0). Accompanying cyclic anhydride group stretching (1230 cm', 1180 cm' (F)), C-0-C stretching vibrations (1107 cm', 1074 cm' (Q)), and cyclic unconjugatcd anhydride group stretching (broad band centered at 937 eni' (R)) absorbanccs were also observed. Thcsc regcncrated anhydride surfaces were then immersed into a solution of cresyl violet perchlorate dissolved in anhydrous 1-mcthyl-2-pyrrolidinonc to give localised dye attachment via amide bonds (amide I at 1666 cm-' (S)) and electrostatic acid-base interactions (COO stretching at 1405 cm' (U) and NH2' deformations at 1592 em' (V). In addition, the strong fingerprint spectral features associated with the cresyl violet perchlorate dye were evident: C-N stretching and C-N-H bending (1335 cm1 (W)), C-H bending and NH2 rocking (1256 cm' (X)), NH2 in-phase bending and NH2 rocking (1514 em' and 1485 car' (Y)), and C-H wagging and twisting band (872 em' (Z)), Figure 5. Verification of the rewriting step was undertaken by placing a 0.1 jl droplet of eresyl violet dye solution onto a maleic anhydride pulsed plasma polymer film surface, and then the substrate was rinsed with N,N dimethylformamide, followed by drying under a stream of nitrogen. Fluorescence microscopy confirmed the attachment of cresyl violet perchlorate dye (excitation wavelength 637 nm) onto the substrate.

This fluorescence signal completely disappeared after UV exposure and rinsing in water.

Subsequent dipping of the substrate into a solution of trifluoroacetic anhydride and triethylamine dissolved in anhydrous N,N dimethylformamide gave rise to the reformation of anhydride groups. Repetition of placing a 0.1 p1 droplet of cresyl violet dye solution onto the regenerated area and rinsing with N,N dimethylformamidc, once again resulted in fluorescence, thus confirming dye attachment onto the substrate. This rewritable behavior was repeated over 10 times, and ultimately depends upon the thickness of the pulsed plasma polymer film. A range of other dyes behaved in a similar fashion towards IJV irradiation and surface regeneration, including 1-pyrenemethyl amine hydrochiorde (excitation wavelength 325 nm) and 7-amino-4-methylcoumarin (excitation wavelength 353 nm).

Contact angle measurements taken at each stage of reaction for Figure 3 were found to be consistent with the aforementioned description. A negligible change in water contact angle (46° to 500) occurred upon reaction of 4-cthylanilinc with the malcic anhydride plasma polymer surface. Whilst imidization produced a more marked increase in contact angle (57°) due to the elimination of surface carboxylic acid groups. Similarly, an improvement in hydrophobicity was noted following the regeneration of anhydridc groups at the UV-hydrolyscd surface (from 15° to 45°). The final cresyl violet perchlorate dye attachment step led to a lowering in contact angle value to 38 as a consequence of anhydride ring opening.

Pafterned IJV photo-rewriting of these surfaces gave rise to the selective attachment of cresyl violet perchlorate dye molecules exclusively in the regenerated anhydridc group regions (i.e. positive imaging), Figure 4 and 5. The multifunctional feature of this approach was illustrated by creation of a biftinctional pattern. Fluorescence imaging confirmed the generation of a bithnctional surface with cresyl violet dye (bars) and Hilyte Fluor 488 amine dye (squares) attached onto the maleic anhydride pulsed plasma layer, Figure 7.

As is shown the invention provides a simple and reproducible way of producing pattered surfaces. Previous reports of single writc patterning of dyes onto solid surfaces have included the attachment of dansyl dyes onto hyperbranched poly(aerylie acid) organic thin films using a five step approach, a four step method utilising microcontact printing of COOH-terminated self-assembled monolayers (SAMs), electrochemieal oxidation of SAMs and a multi-stage vapour deposition process.

The current methodology offers a number of distinct advantages. These include the fact that only 2 steps are required (pulsed plasmachemical deposition and molecular inking), the surface density of tethered dye molecules can be tailored by varying the pulsed plasma duty cycle parameters, and a variety of substrates can be utilized (unlike for instance self-assembled monolayer systems). Furthermore, it is evident that (iv lithography can be employed to prepare multiflinctional rewritable arrays. The surface anhydride groups should also be amenable to a range of other chemistries including hydrolysis, acylation, acetylation, and esterification.

It is to be understood that the above embodiments have been provided only by way of exemplification of this invention, such as those detailed below, and that further modifications and improvements thereto, as would be apparent to persons skilled in the relevant art, are deemed to fall within the broad scope and ambit of the present invention described. Furthermore where individual embodiments are discussed, the invention is intended to cover combinations of those embodiments as well.