Modification of a Solid Surface

Abstract

A process for the modification of a surface of a solid material, said solid material comprising a polymer material arranged at the surface of the solid material. Said process comprises the step of: contacting the polymer at the surface of the solid material with an oxygen source and a catalytic amount of a transition metal compound under such conditions that oxygen is incorporated into the polymer surface, wherein a hydroxy group is formed, which is attached to a carbon atom of the polymer.

Claims

1. A process for the modification of a surface of a solid material, said solid material comprising a polymer material arranged at the surface of the solid material, said process comprising the step of: i. contacting the polymer at the surface of the solid material with an oxygen source and a catalytic amount of a transition metal compound under such conditions that oxygen is incorporated into the polymer surface, wherein a hydroxy group is formed, which is attached to a carbon atom of the polymer.

2. The process according to claim 1, wherein during the modification step i. the oxygen is predominantly incorporated in the polymer surface in the form of the hydroxy group, which is attached to a carbon atom of the polymer, with respect to all carbon-oxygen bonds formed at the polymer surface.

3. The process according to claim 1, wherein the oxygen source comprises a peroxide material, preferably hydrogen peroxide.

4. The process according to claim 1, wherein the transition metal compound comprises at least one cation selected from the group consisting of Chromium, Manganese, Iron, Cobalt, Nickel and Copper, preferably a Cu(II) cation, or selected from the group consisting of Rhodium, Palladium, and Platinum.

5. The process according to claim 4, wherein the transition metal compound comprises Cu(II) (acetate).sub.2 or Cu(II) (nitrate).sub.2.

6. The process according to claim 1, wherein during the first modification step i. the concentration of the transition metal compound in a solvent is less than 100 mM.

7. The process according to claim 1, wherein the first modification step i. is assisted by applying a microwave irradiation to the solid material.

8. The process according to claim 1, wherein the first modification step i. is performed at temperatures below a phase transition temperature of the polymer, such as a glass transition temperature T.sub.g or a melting transition temperature T.sub.m of the polymer.

9. The process according to claim 1, wherein said surface is an internal surface of the solid material.

10. The process according to claim 9, wherein said surface is a surface of a micro fabricated structure inside the solid material.

11. The process according to claim 1, wherein the oxygen source and the transition metal compound are applied in the form of an aqueous solution thereof.

12. The process according to claim 1, wherein the modification step i. comprises using a patterned stamp structure for locally contacting the surface of the polymer, thereby locally bringing the oxygen source and/or the transition metal compound in contact with the surface of the polymer.

13. The process according to claim 12, wherein the stamp structure comprises a gelled material having the transition metal compound arranged at its contacting surface.

14. The process according to claim 12, wherein the stamp structure comprises an elastic material configured for carrying the oxygen source and/or the transition metal compound, preferably in the form of an aqueous solution, at its contacting surface.

15. The process according to claim 1, wherein the first modification step a) is assisted by adding an acidic component in a substantially catalytic amount.

16. The process according to claim 1, said process comprising the step of: ii. contacting the oxidized polymer surface obtained in the oxidation step i. with a reducing agent to obtain a polymer surface having hydroxy nucleophilic groups, which are attached to carbon atoms of the polymer.

17. The process according to claim 1, wherein the reducing agent comprises a borohydride, preferably a sodium borohydride.

18. The process according to claim 1, wherein the polymer comprises a cyclic olefin polymer, preferably a cyclic olefin copolymer.

19. The process according to claim 18, wherein the cyclic olefin polymer comprises an ethylene polymer segment and/or a norbornene polymer segment.

20. The process according to claim 1, wherein the polymer comprises at least one segment of the group consisting of a polyolefin segment, a polymethylmethacrylate segment, a polystyrene segment and a polycarbonate segment.

21. The process according to claim 1, wherein the process further comprises the steps of: iii. contacting the surface of the solid material comprising the polymer including hydroxy nucleophilic groups attached thereon with a hydrosilane to produce a hydrosilanized surface, and iv. contacting said hydrosilanized surface with at least one alkene and/or alkyne under irradiation with visible and/or ultraviolet light.

22. A solid material, said solid material comprising a polymer material arranged at the surface of the solid material, wherein said surface is an internal surface of the solid material, said solid material being obtainable by the process according to claim 1.

Description

DESCRIPTION OF THE FIGURES

[0071] FIG. 1A shows a reaction scheme for the modification of COC (i) into a nucleophilic surface, COCOH, via copper-catalyzed peroxidative oxidation.

[0072] FIG. 1B shows a reaction scheme for the modification of COC (i) into a nucleophilic surface, COCOH, via copper-catalyzed peroxidative oxidation, which is followed by a mild reductive washing step.

[0073] FIG. 1C shows a reaction scheme for the subsequent silanization with HSiCl.sub.3/HSiPhCl.sub.2 (5:1), which yields the COCSi-.sub.1-H.sub.5 hybrid material.

[0074] FIG. 1D shows a reaction scheme for the mild light-induced hydrosilylation with a terminal alkene.

[0075] FIG. 2 shows GATR-FTIR of a COC surface after oxidation by (a) air plasma for 10 s; (b) copper-catalyzed peroxidative oxidation for 30 min and (c) coppercatalyzed peroxidative oxidation with HNO.sub.3 as additive for 30 min; (d) after washing with methanolic NaBH.sub.4 (unmodified COC used as a reference background).

[0076] FIG. 3 shows XPS wide scans (i), C1s (ii) and O1s (iii) narrow scans of (a) COC subjected to air plasma; (b) COC oxidized with Cu(II)/H.sub.2O.sub.2 mixture for 30 minutes 5 W microwave irradiation at 40 C.; (c) COC oxidized with Cu(II)/H.sub.2O.sub.2 mixture at R.T. under sonification; (d) COC oxidized with Cu(II)/H.sub.2O.sub.2/HNO.sub.3 mixture, and (e) COC oxidized with Cu(II)/H.sub.2O.sub.2 mixture and washed with methanolic NaBH.sub.4; and (f) bare COC.

[0077] FIG. 4 shows (a) XPS wide scan of (b) a COCSi-.sub.1-H.sub.5 substrate. (c) GATR-FTIR of the COCSi-.sub.1-H.sub.5 substrates, showing the two SiH stretching vibrations (COCOH was used as reference background).

[0078] FIG. 5 shows (a) XPS wide scan of (b) a COCSi-.sub.1-H.sub.5 substrate modified with TFAAD in the presence of 330 nm light for 16 h. (c) GATR-FTIR of the TFAAD modified substrates, showing inversion of the two types of SiH stretching vibrations and presence of the carbonyl from TFAAD.

[0079] FIG. 6 shows (a) Photograph and SEM image (b) of a TFAAD-patterned COCSi-.sub.1-H.sub.5 after exposure to DCM (dichloromethane) (30 min).

[0080] FIG. 7 shows a Microscope image of plastic microchip with (a) a TFAAD-modified COC channel; (b) a partially TFAAD-modified COC channel (the part on the left was coated; the right part is uncoated) after exposure to a flow of DCM (white arrow indicates flow direction; 50 L/min; 30 min), showing significantly more damage in the uncoated part.

[0081] FIG. 8 shows a reaction scheme for the light-induced reaction of an ROH compound with a silanized COC-substrate.

DETAILED DESCRIPTION OF THE INVENTION

Static Water Contact Angle Measurements (SCA):

[0082] Static water contact angles (SCA) were measured using a Krss DSA-100 goniometer. Droplets of 3 L were dispensed on the surface, and contact angles measured with a CCD camera using a tangential method. The reported value is the average of at least five droplets of at least three different samples, and has an error of 1 between samples.

Germanium Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (GATR-FTIR):

[0083] GATR-FTIR spectra were recorded with a Bruker Tensor 27 FT-IR spectrometer, using a commercial variable-angle reflection unit (Auto Seagull, Harrick Scientific). A Harrick grid polarizer was installed in front of the detector and was used for measuring spectra with p-polarized radiation with respect to the plane of incidence at the sample surface. Single channel transmittance spectra were collected at an angle of 25 using a spectral resolution of 2 cm.sup.1 and 2048 scans while flushing with dry N.sub.2. Obtained spectra were referenced with a clean H-glass substrate (H-glass substrates were referenced with freshly plasma-cleaned glass).

X-Ray Photoelectron Spectroscopy (XPS):

[0084] XPS spectra were recorded on a JPS-9200 photoelectron spectrometer (JEOL, Japan). The analysis was performed under ultra-high vacuum conditions using a monochromatic Al K source at 12 kV and 20 mA and an analyzer pass energy of 10 eV. A takeoff angle of 80 was used, with a precision of 1. All XPS spectra were analyzed with Casa XPS software (version 2.3.15). The binding energies were calibrated on the hydrocarbon (CH.sub.2) peak with a binding energy of 285.0 eV. Because of the electrostatic charging of the surface during the measurements, a charge compensation was used with an accelerating voltage of 2.8 eV and a filament current of 4.80 A.

Atomic Force Microscopy (AFM):

[0085] AFM images (512512 pixels) were obtained with an MFP3D AFM (Asylum Research, Santa Barbara, Calif.). The imaging was performed in contact mode under air using NP silicon nitride cantilevers with a stiffness of 0.58 N/m (Veeco Metrology, Santa Barbara, Calif.) at a scan speed of 1 m/s. Images were flattened with a zeroth-order flattening procedure using MFP3D software.

Scanning Electron Microscopy/Scanning Auger Microscopy (SEM/SAM):

[0086] Morphologies of TFAAD micropatterns were analyzed by SEM/SAM. Measurements were performed at room temperature with a scanning Auger electron spectroscope system (JEOL Ltd. JAMP-9500F field emission scanning Auger microprobe). SEM and SAM images were acquired with a primary beam of 0.8 keV. The takeoff angle of the instrument was 0. For Auger elemental image analysis an 8 nm probe diameter was used.

EXAMPLES

Materials and Chemicals

[0087] 1-Hexadecene was obtained from Sigma Aldrich and distilled twice before use. Acetone (Aldrich, semiconductor grade VLSI PUNARAL Honeywell 17617), dichloromethane (DCM, Sigma Aldrich) and n-hexane (Merck Millipore) were used for cleaning before modification and Milli-Q water (resistivity 18.3 Mcm) for rinsing after hydrolysis process. Cyclic olefin copolymer (COC, grade 6013) was obtained from TOPAS Advanced Polymers. All other chemicals were purchased from Sigma Aldrich and used as received. 10-Trifluoro-acetamide-1-decene (TFAAD) was synthesized based on literature methods..sup.20

Substrate Preparation

Plasma-Activated Cyclic Olefin Co Polymer (COC):

[0088] The COC substrate obtained from TOPAS was sonicated in isopropanol (iPrOH) for 30 min, rinsed with iPrOH after taking it out, and dried under a stream of nitrogen.

Oxidation

[0089] In order to be able to covalently silanize a COC substrate, the surface first needs to be activated. Activation of a COC surface into a nucleophilic anchor-containing surface can be achieved via oxidation of the alkane surface into COH groups (e.g. alcohol or acid). A ubiquitous surface oxidation method makes use of oxygen or air plasma, modifying the CH terminus into a COx (e.g. alcohol, acid, ketone, aldehyde). This plasma method was evaluated and compared with a mild oxidation based on exposure to an aqueous solution of hydrogen peroxide and a copper acetate (FIG. 1A). FIG. 1A shows a reaction scheme for the modification of COC (i) into a nucleophilic surface, COCOH, via copper-catalyzed peroxidative oxidation, which may optionally in an exemplary embodiment be followed by a mild reductive washing step.

Using Plasma Treatment of COC Substrates

[0090] An air plasma-based treatment of COC substrates for 10 s gives immediate results. The static water contact angle drops from 100 to <30, indicating the rapid formation of hydrophilic surface groups.

[0091] From GATR-FTIR measurements it becomes clear that a variety of surficial carbonyl species are present (FIG. 2a). FIG. 2a shows GATR-FTIR of a COC surface after oxidation by air plasma for 10 s. Wide range XPS data reveal an increase in total oxygen content (FIG. 3a), while XPS C1s narrow scans show many peaks to indicate that multiple functional groups are now present on the surface (due the presence of various oxidized forms of carbon, e.g. (COH) 286.9 and 289.3 (CO). Unfortunately, this surface modification technique is not able to homogeneously functionalize the inside of intricate COC channels due to plasma-diffusion limitations in microfluidic devices.

Using Catalysed Peroxidation of COC Substrates

[0092] In order to bypass the limitations stated above, we first exposed COC to 30% (v/v) H.sub.2O.sub.2 and no change in the water contact angle was observed, even after simultaneous sonication for 30 mins.

[0093] Then it was compared with a mild oxidation based on exposure to an aqueous solution of hydrogen peroxide20% (v/v)and copper acetate (20 mM) (FIG. 1A). Upon the addition of copper(II) acetate, a contact angle of 832 was obtained in just 30 min by contacting the aqueous solution of hydrogen peroxide20% (v/v)and copper acetate (20 mM) to the surface of the COC substrate at room temperature using sonication.

[0094] We reviewed how the addition of additives, such as triphenylphosphine PPh.sub.3, in the washing/quenching solution can be used after the oxidation step to favour the decomposition of the CyOO.Math. species into the alcohol (CyOH) counterparts instead of into ketones or other minor overoxidation products such as esters.

[0095] However, attempts to use PPh.sub.3 to favor the conversion of COCOO.Math. to COCOH did not yield satisfactory results. The PPh.sub.3 oxidation adduct (OPPh.sub.3) forms a sticky precipitate that whitens the substrates and clogs microfluidic channels.

[0096] Adding a small amount of nitric acid (20 mM) in the oxidation solution, increased the yield slightly and shows some tuning ability towards the alcohol product is possible; similar results were found in solution.

[0097] Additionally, after the oxidation step a washing step with a polar solvent, such as methanol, may be used to remove Cu oxide contaminants from the surface of the polymer.

Using Additional Reducing Step

[0098] We found an easy method for reducing the oxidized surface of the polymer by using methanolic NaBH.sub.4 (40 mM) in the washing step (by sonication for 5 mins at room temperature) of the copper catalyzed oxidized surfaces (see reaction scheme in FIG. 1B). FIG. 1B shows a reaction scheme for the modification of COC (i) into a nucleophilic surface, COCOH, via copper-catalyzed peroxidative oxidation, which is followed by a mild reductive washing step by using methanolic NaBH.sub.4 in the washing step.

[0099] This yielded further a reduction in the water static contact angle to 722. These values are close to those of other COCOH substrates found in literature.

[0100] Our method represents a clear improvement in that it is much milder (no UV required, room temperature, aqueous solution), and leaves far less contaminants on the surface.

[0101] To further corroborate the exemplary embodiments of the process according to the present invention, the surfaces were analyzed by GATR-FTIR (FIG. 2b-d). FIG. 2 shows GATR-FTIR of a COC surface after oxidation by (a) air plasma for 10 s; (b) copper-catalyzed peroxidative oxidation for 30 min and (c) coppercatalyzed peroxidative oxidation with HNO.sub.3 as additive for 30 min; (d) after washing with methanolic NaBH4 (unmodified COC used as a reference background).

[0102] The presence of alcohol (3174 cm1) and carbonyl groups (1735 cm1) indicates that the surface has undergone oxidation. The reduced amount of carbonyl-related stretching peaks compared to what is observed upon air plasma treatment is further evidence that the aqueous Cu/H.sub.2O.sub.2 oxidation is mild. Of specific interest is the basically flat IR spectrum in the CO region (FIG. 2d) upon NaBH.sub.4washing.

[0103] XPS wide scans show that our peroxidative treatment yields a clear increase of oxygen content when compared to bare COC, and less than for plasma-treated COC (FIG. 3a-e).

[0104] FIG. 3 shows XPS wide scans (i), C1s (ii) and O1s (iii) narrow scans of (a) COC subjected to air plasma; (b) COC oxidized with Cu(II)/H.sub.2O.sub.2 mixture for 30 minutes 5 W microwave irradiation at 40 C.; (c) COC oxidized with Cu(II)/H.sub.2O.sub.2 mixture at room temperature under sonication; (d) COC oxidized with Cu(II)/H.sub.2O.sub.2/HNO.sub.3 mixture, and (e) COC oxidized with Cu(II)/H.sub.2O.sub.2 mixture and washed with methanolic NaBH.sub.4; and (f) bare COC.

[0105] In FIG. 3 (ii) the C1s narrow scans indicate a predominance of CC bonds (285.0 eV) for all substrates, while in the oxidized substrates COH and CO are distinctively present (286.8 and 289.3 eV).

[0106] In FIG. 3 (iii, a), the O1s narrow scans show the presence of COH (532.7 eV-57.6%) and OCO (533.8 eV-42.4%) for the COC that was subject to plasma treatment.

[0107] COC that has been subjected to the Cu/H.sub.2O.sub.2 oxidation (see FIG. 3c) or Cu/H.sub.2O.sub.2/HNO.sub.3 oxidation (see FIG. 3d) show a predominant presence of COH (532.4 eV-56% or 68%) along with the less prevalent CO (531.4 eV-17.2% or 11.6%), OCO (534.0 eV-26.5% or 20.1%), and copper oxide (529.9 eV) contaminants due to just washing with water for analysis purposes.

Microwave Radiation

[0108] Furthermore, COC that has been subjected to the Cu/H.sub.2O.sub.2 oxidation while being subjected to a microwave irradiation of 5 W (see FIG. 3b) for 30 minutes show a further increase of presence of COH (532.4 eV) with respect to the Cu/H.sub.2O.sub.2 oxidation under sonication without using microwave (see FIG. 3c) along with a less prevalent CO (531.4 eV), OCO (534.0 eV).

[0109] The amount of oxidation O1s has increased by subjecting the substrate to a microwave irradiation of 5 W during oxidation (9.5% with microwave irradiation versus 5.0%-7.6% without microwave irradiation). Furthermore, the selectivity towards COH (532.4 eV) has increased due to the microwave irradiation.

[0110] Furthermore, in line with the IR and C1s XPS results, the inclusion of a subsequent washing step of reductive agent NaBH.sub.4 (see FIG. 3e) yields a near-quantitative conversion to alcohols, free of Cu oxide contaminants.

[0111] The resulting presence of basically only one type of oxidized carbon, i.e. COH (532.4 eV), is a major improvement over air/oxygen plasma methods.

[0112] As previously mentioned, the ability to generate OH terminated COC surfaces allows for a wide variety of functionalization chemistries. In the current paper, we present as an example the first of those under current development. Given the increasing use of COC in the fabrication of microfluidic devices, chemistries that allow for plastics photolithography are extremely desirable.

Stamp Patterning Process

[0113] An another experiment, a patterned stamp structure is used for locally contacting the surface of the polymer, thereby locally bringing the a solution of the oxygen source and the transition metal compound in contact with the surface of the polymer.

[0114] The stamp structure comprises an elastic material, which in this example is polydimethylsiloxane (pdms). A hydrogen peroxide oxygen source H.sub.2O.sub.2 and the transition metal compound (Cu(II)acetate) in the form of an aqueous solution thereof are provided on a contacting surface of the pdms stamp by dipping the PDMS stamp in a Cu(II)acetate/H.sub.2O.sub.2 solution and press the contacting surface of the pdms stamp including the Cu(II)acetate/H.sub.2O.sub.2 solution onto half of a COC substrate.

[0115] After the experiment a considerably reduction is observed in contact angle of the processed (half part) surface of the COC substrate from 98-100 to 92.

[0116] In this way, a controlled patterned part of the surface of the COC substrate may be processed according to exemplary embodiments of the process of the present invention, thereby oxidizing the surface of the COC polymer.

[0117] Additionally, further modifications of the controlled patterned parts on the surface of the COC substrate may be carried out according to exemplary embodiments of the process of the present invention.

Silanization of the COC Polymer Surface

[0118] In line with our previous work done on borosilicate glass and described in co-pending application in The Netherlands with application number 2016290, which is hereby incorporated by reference, we aimed to modify COCOH with a 5:1 mixture of trichlorosilane and dichlorophenylsilane.

[0119] With this, we envisioned to fabricate a hybrid material, hydrogen-(phenyl)-terminated silanized COC (COCSi-.sub.1-H.sub.5), that would have a similar reactivity as the previously reported H--glass.

[0120] Of specific interest were the findings that H--glass was shown to be highly stable in air for months, while smoothly reactive towards alkenes using light of 328 nm.

[0121] FIG. 1C shows a reaction scheme for the subsequent silanization with HSiCl3/HSiPhCl2 (5:1), which yields the COCSi-.sub.1-H.sub.5 hybrid material.

[0122] The hybrid material COCSi-.sub.1-H.sub.5 (FIG. 4B) was prepared along these lines and analyzed. Static water contact angles (85 for COCSiH and 90 for COCSi-.sub.1-H.sub.5) were similar to the ones we reported for analogous silicon-based substrates. XPS wide scans (FIG. 4A) show the presence of Si at 102 eV, indicating the formation of an ultrathin layer on top of COC.

[0123] Analysis by GATR-FTIR, while using COCOH as a reference background, confirms the presence of two different SiH stretching bands, which we attributed to O3SiH at 2249 cm1 and to O2SiH at 2185 cm1 (FIG. 4C).

Photochemical Surface Modification

[0124] Having characterized the COCSi-1-H5 substrates, we proceeded with modifying it further via light-induced hydrosilylation.

[0125] For this, we chose 10-trifluoro-acetamide-1-decene (TFAAD) as a reactivity probe. This alkene is useful to evaluate attachment, due to the IR-active carbonyl group and three CF bonds with characteristic XPS C1s and F1s signals, and can be easily converted into an amine, upon deprotection.

[0126] FIG. 1D shows a reaction scheme for the mild light-induced hydrosilylation with a terminal alkene. COCSi-.sub.1-H.sub.5substrates were modified with TFAAD using 328 nm light. The TFAAD-substituted COCSi-.sub.1-H.sub.5 substrates (as shown in FIG. 5B) were characterized by GATR-FTIR using COCSi-.sub.1-H.sub.5 as reference background.

[0127] The carbonyl stretching peak from TFAAD was clearly present at 1705 cm1 (FIG. 5C). The reversal of the SiH peaks at 2249 nm and 2185 nm indicates that there are less SiH bonds than before the hydrosilylation, i.e., that the alkene reacted with the hydrogen-terminated surfaces forming SiC bonds. Wide range XPS scans show the presence of fluorine, while C1s narrow scans indicate the presence of CF3 groups at 293.5 eV (FIG. 5A). This further confirms covalent attachment of TFAAD onto the COCSi-.sub.1-H.sub.5surfaces (as shown in FIG. 5B).

[0128] Similarly to the results obtained on glass, AFM measurements of these surfaces show that the roughness does not change considerably upon modification (RMS roughness from 1.90.2 nm to 2.00.5 nm), which is another significant improvement over plasma-based oxidations.

[0129] Photolithography on open substrates was performed by positioning a contact mask (circular TEM grid with circles and spokes) on top of the COCSi-.sub.1-H.sub.5 substrates during the light induced hydrosilylation reaction. We then planned to visualize the resulting pattern by scanning electron microscopy (SEM) (FIG. 6). FIG. 6 shows a Photograph (FIG. 6a) and SEM image (FIG. 6b) of a TFAAD-patterned COCSi-.sub.1-H.sub.5 after exposure to DCM (30 min).

[0130] Interestingly, when cleaning the modified substrate with dichloromethane (DCM) for 5 mins to allow for SEM measurements, we observed that the pattern had slowly become visible by naked eye (FIG. 6a). Further exposure to DCM showed clear degradation by the solvent of the non-exposed areas, while the TFAAD-modified areas resisted solvent damage effectively (FIG. 6b). Overall, the ability to covalently bind an ultrathin, yet highly protective coating that can be further modified, opens the use of these substrates for many applications.

[0131] Alternatively, considering that light in the presence of water can be used to hydrolyse the SiH surface, one could also use light in the presence of a molecule of formula ROH (such as water HOH, an alcohol COH. or a silica-hydroxide molecule SiOH) to locally modify a COCOSiH group. A reaction scheme for the light induced reaction with ROH is illustrated in FIG. 8.

Modification of Microfluid Device

[0132] We then finally proceeded to modify the channel of an already bonded COC microreactor (Micronit) into COCOH by flowing the oxidation solution for 20 mins at 50 L/min and washing for 5 mins (50 L/min) with methanolic NaBH4.

[0133] Silanization was carried out and a fully modified COCSi-.sub.1-H.sub.5 microfluidic channel was photopatterned with TFAAD (see Info of photolithography for details).

[0134] We then tested the ability of the TFAAD patches to protect the device from a prolonged flow of Dichloromethane DCM (30 min at 50 L/min). As can be seen from FIG. 7b, the coating provides significant protection even to harsh solvents such as DCM.

[0135] In the absence of a protective coating, the polymer swells and cracks, starting as stripe-like cracks at the side of the channel (FIG. 7b). In addition, the bonding strength between the COC top and bottom substrates is severely weakened and leakage occurs. Since the TFAAD moiety is by no means optimized for this purpose, functional group optimization will likely provide significant possibilities for further improvement of the protection.

[0136] In conclusion, we have demonstrated a mild aqueous CH activation method to modify the surface of cyclic olefin copolymers (COC).

[0137] This method can be applied to open plastic substrates as well as to bonded microchannels, and yields highly defined alcohol-terminated COC surfaces with less or none carbonyl-containing moieties. Due to their nucleophilic character, such surface-bound alcohol moieties can be used for a very wide array of surface modifications.

[0138] When e.g. reacted with hydrosilanes (such as Cl.sub.3SiH or Cl.sub.2PhSiH), this surface yields a hydrogen-terminated COC surface. This new hybrid surface is highly stable in air and photo-patternable via a mild light-induced hydrosilylation with terminal alkenes. The TFAAD functional monolayer attached in this fashion enhanced the resistance of the COC to organic solvents (e.g. DCM).

[0139] In addition, TFAAD is well known for its ability to undergo further surface modifications for e.g. biological applications.

[0140] This research opens a door towards the mild activation of what was considered a highly inert substrate that required harsh modification techniques. This technique is transposable to other CH containing polymer analogues, e.g. a polymer comprises at least one segment of the group consisting of a polyolefin segment, a polymethylmethacrylate segment, a polystyrene segment and a polycarbonate segment, or polyphenyl ethers/oxides (PPEs/PPOs) and polyether ether ketone (PEEK) segment.

Silanization

[0141] In the examples given, silanization may be performed using either triethoxysilane or trichlorosilane.

[0142] In the reactions with both triethoxysilane and trichlorosilane, O.sub.3SiH groups are formed onto the surface of the solid material. This bestows an entirely new chemical reactivity onto the solid material.

Using Trichlorosilane (HSiCl.SUB.3.), COC and CVD:

[0143] Chemical vapour deposition (CVD) was used for gas-phase modification with HSiCl.sub.3. The COC substrate was held in a desiccator, and a HSiCl.sub.3 system prepared in the glove box was connected to this desiccator. The HSiCl.sub.3 flask was then used to fill the desiccator with trichlorosilane gas, and the silanization of the COC was carried out for 30 minutes. After 30 minutes, the system was then quenched.

Photochemical Surface Modification

[0144] In example experiments carried out for the present invention, silanized substrates were subsequently used for the light-induced modification with an alkene or alkyne.

[0145] In this photochemical modification method, a drop of the chosen alkene or alkyne was placed on the flat silanized sample within a glove box. A slide, for example, a COC substrate, was then placed on the drop and gently pressed against the silanized sample to homogenously spread the alkene between the two slides, and also to mimic a closed microfluidic channel. The slide assembly was then illuminated with a UV pen lamp (with a wavelength of 254, 302, 330 or 365 nm, Jelight Company, Irvine, Calif., USA) which was placed approximately 4 mm above an external surface of either the silanized sample of the slide. The entire setup (i.e. the UV lamp and the slide assembly) was then covered in aluminium foil and the sample irradiated for 16 h. After irradiation, the substrates were extensively rinsed with distilled dichloromethane and hexane and dried under argon. The surfaces were then directly used for surface characterization or stored under air.

Photolithography

Planar Surface:

[0146] Photolithography was performed with a 302 nm lamp in combination with a gold electron microscope grid (SEM F1, Gilder Grids). This gold electron microscope grid (i.e. a photolithographic mask) was placed on top of a flat silanized sample of a solid material (for example, a slide of COC substrate) together with a drop of a suitable alkene. After the liquid had been spread across the silanized surface of the solid material, a borosilicate glass slide (SCHOTT) was placed on top of the mask as a cover, above which the UV pen lamp was placed at a distance of approximately 4 mm. The slide assembly was irradiated for 16 h. removed from the glove box and cleaned by extensively rinsing with distilled dichloromethane and hexane and drying under argon.

[0147] In this photolithography process, the gold electron microscope grid was used to pattern the surface by locally blocking UV light.

Inside Surface of a Microchannel:

[0148] For the microchannels, photolithography was performed by applying a photolithographic mask on the bottom side of a microfluidic chip, for example, a chip provided by Micronit.