The invention concerns the manufacturing of an optical micro-array, comprising a high quality polymer (plastic) window array for e.g. micro sensors.
Polymer optical micro-arrays for e.g. multi-analyte sensors in clinical microbiological analysis, environmental, health and safety, food/beverage and chemical processing applications must be highly transparent and the mutual crosstalk of the optical analysis signals minimal. Conventional polymer processing techniques trying to produce one-piece window arrays have not been successful until now as they did not result in a sufficiently high transparency of the windows (low optical signal attenuation) and/or a sufficiently low signal crosstalk level between those windows.
Use of two materials, viz. optical transparent micro structures for transferring optical signals and an optical non-transparent frame material for mechanical support and optical signal isolation (crosstalk prevention), gives problems w.r.t. the manufacturing and particularly the assembly of such arrays. Positioning and fixing of the optical micro structures (lenses, windows) within the frame make high demands on process and materials (location accuracy, damage of optical structures, shrinking differences) while extra care is required for mutual binding the micro structures and frame.
Aim of the present invention is to provide a method for manufacturing a polymer body which comprises one or more first areas which are transparent and one or more second areas which are non-transparent.
According to an aspect of the invention, there is provided an optical micro-array for use in conjunction with a chemical sensor, comprising a polymer body comprising one or more first areas which are transparent, the transparent areas sectioned by second areas which are non-transparent; wherein the micro-array is comprised of a single body; the transparent areas being formed by non-crystallized polymer and the non-transparent areas being formed by crystallized polymer.
The micro-array can be manufactured based on the understanding that the morphology of polymers may comprise amorphous (non-crystalline, transparent) areas and/or crystalline (non-transparent) areas. The degree of crystallinity of so-called semi-crystalline polymers is determined by the thermal history of the polymer, especially by the cooling rate. In general it can be stated that cooling down quickly will suppress the formation of crystals, resulting in a more amorphous polymer, whereas slow cooling will lead to the formation and grow of crystals.
According to another aspect, the method according to the invention comprises next steps:
a. a semi-manufactured body is produced by applying any method known as such, the semi-manufactured body comprising said first and second areas which, however, in this semi-manufactured stage are either both transparent or both non-transparent;
b. when the first and the second areas of the semi-manufactured body are transparent, the polymer in said second areas is heated to above the polymer's melting temperature and subsequently cooled so slowly as to realize substantial crystallization of the polymer in the second areas;
c. when the first and the second areas of the semi-manufactured body are non-transparent, the polymer in said first areas is heated to above the polymer's melting temperature and subsequently cooled so quickly as to prevent substantial crystallization of the polymer in the first areas
d. in a further additional step, the transparent areas may be provided with an optically active material; for optical read out before, and during or after exposure to a chemical substance to be tested; so that the polymer window can be used for testing purposes in a (micro) sensor. Preferably, the sensor is of a multi-analyte type.
It may be preferred to start with an entirely non-transparent semi-manufactured body (option c), because the cooling down time, which has to be so short as to prevent substantial crystallization of the polymer in the first areas, will be, in consequence, shorter than when starting with an entirely transparent semi-manufactured body (option b), where the cooling down time has to be rather long, viz. long enough for the crystallization process in the second areas to realize a non-transparent morphology there.
On the other side, it may preferred to start with an entirely transparent semi-manufactured body (option b), because the focus can primarily be put on the optical transparency of the starting material of the semi-manufactured body, ignoring possible signal crosstalk problems, which are resolved in the final manufacturing stage, viz. by (re)heating and crystallization the second areas, serving as crosstalk preventing barriers.
The semi-manufactured polymer body may be manufactured by e.g. a well-known process like injection moulding, warm pressing of sheet or film e.g. by means of embossing or via a roll-to-roll process etc. When starting with a entirely transparent semi-manufactured body, in the second production step optical non-transparent, anti-crosstalk barriers are realized e.g. around the optical transparent (micro)windows. When starting with a entirely non-transparent semi-manufactured body, in the second production step optical transparent e.g. (micro)windows may be made within the non-transparent environment. To either case, the polymer of the semi-manufactured body is melted locally and then cooled in a controlled way, either quickly, to prevent (re)crystallization, or slowly, to realize deliberate (re)crystallization.
Local heating of the semi-manufactured body can be performed within or outside the mould which was used to make the semi-manufactured body. Electric, fluid, laser heating, microwave and ultrasonic heating may be applied to change the amorphous polymer structure into a semi-crystalline or inversely. Without additives to the polymer, a CO2 laser may be used or, by adding a NIR absorbing additive, a diode laser.
Cooling rates for a polymer to become mainly amorphous are in the order of tens of degrees Celsius per second. When, however, the cooling down rate is about hundredths of degrees Celsius per second, a substantial crystalline state will be reached.
a and 1b show two exemplary embodiments of a semi-manufactured body, serving as a starting structure for a micro-window array, to be made in a subsequent step.
a shows a entirely transparent (coloured black) polymer body 1 in semi-manufactured fashion, e.g. made by injection moulding, which comprises several first areas 2 and several second areas 3. Both, the first areas 2 and the second areas 3 are transparent, as is the entire body 1.
b shows a entirely non-transparent (coloured white) polymer body 1 in semi-manufactured fashion, e.g. made by injection moulding, which comprises several first areas 2 and several second areas 3. Both, the first areas 2 and the second areas 3 are non-transparent, as is the entire body 1.
Typical dimensions of the areas 2 are 2×2 mm, so that for instance an array area on body 1 of typically 30×30 mm is available of about 100 transparent areas 2. On these transparent areas 2, preferably, of the body 1 a chemically selective coating is applied, for instance, with dispensing techniques, e.g. based on adhesives application or ink printing techniques. Such coatings can react with substances in gaseous or liquid media to be analysed, changing the transmission properties (wavelength, absorption) of the transparent areas of the window array enabling the detection of the substances. Coatings can be applied, selective, for instance, for the detection of carbon dioxide, ammonia, methanol, ethanol, grades of fuel and other gaseous and liquid substances.
Accordingly, the optical micro-array can form part of an optical micro sensor system as will be further elucidated with reference to
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Heating the areas 2 or 3 respectively—e.g. by laser heating—may either be performed when the semi-manufactured body still remains in the mould or in another device after the semi-manufactured body has taken out of the injection mould.
It is noted that in both cases—viz. either starting from a transparent or from a non-transparent semi-manufactured body 1—, the polymer body 1 in semi-manufactured fashion could be made from or even be part of a (pre-manufactured) foil—e.g. stored on a roll—instead of made by injection moulding. When made from foil the areas 3, which are somewhat protruding in the figures, will preferably protrude minimally or entirely not.
In the case that the polymer body 1 in semi-manufactured fashion is made from or part of a pre-manufactured foil, e.g. wound at a storage coil, both process steps could be performed by means of some form of “embossing” or “roll-to-roll” processing. In such a (more continuous) processing environment the heating of the areas 2 or 3 respectively may be performed in the form of a (semi-)continuous process, e.g. during unloading of the semi-manufactured (foil) body—part of a (semi-)continuous foil flow—from its storage coil (reel) either to another storage coil or to another processing or storage module.
In the context of this application, an area 2 is considered to be transparent if it is suitable for guiding light, in particular it is considered transparent if the transmittance of light of at least a particular wavelength through 1 mm of the area is at least 80%, preferably at least 90%, and more preferably 95-100%.
An area 3 is considered to be non-transparent if it is suitable to serve as a light barrier, in particular if the transmittance of light of at least a particular wavelength through 1 mm of the area is at most 20%, preferably at most 10%, and more preferably 0-5%. Such non-transparent areas are suitable for acting as a light barrier.
In principle, the light wavelength can be any wavelength in the ultraviolet, visible or infrared spectrum, in particular any wavelength from 190 to 1 500 nm. Preferably, the area is transparent respectively non-transparent over a wavelength range of at least 50 nm, preferably at least 100 nm. Usually, the wavelength range will not exceed 250 nm. Preferably, the transparent areas are transparent for light with a wavelength between 400 and 800 nm and the non-transparent areas are not transparent for light within this range.
The optical micro-array can be composed of any semi-crystalline thermoplastic polymer, including copolymers and blends. In particular, such polymers include polyethyleneterephthalates, polyamides, polymethylpentenes, polypropylenes, and polyethylenenaphthalates.
Although the invention has been explained with reference to exemplary embodiments, it is not limited thereto. For instance, alternatively, the optical micro-array can be provided in a reflective mode, for instance, by integrating a reflective surface in the array 1 or placing the array on a reflective surface provided in the sensor system (not shown). The scope of the invention is defined by the claims annexed hereto.
Number | Date | Country | Kind |
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06075107.0 | Jan 2006 | EP | regional |
06076307.5 | Jun 2006 | EP | regional |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/NL07/50021 | 1/18/2007 | WO | 00 | 9/26/2008 |