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Diffractive encoding of microparticles for application to bead-based biological assays

Diffractive encoding of microparticles for application to bead-based biological assays
Diffractive encoding of microparticles for application to bead-based biological assays

A new method for high-capacity encoding of microbeads that allows non-contact optical reading has been developed. In this new approach, a bead is encoded by a number of superimposed gratings with different periods manufactured on the surface of the bead, where each distinguishable tag has a unique combination of superimposed gratings. The tags are read optically at a distance, by detecting the diffraction pattern produced by the superimposed gratings. It has been demonstrated that the tagging method allows for millions of unique and distinguishable tags only a few tens of micrometers in size, when read by visible laser light. Using 2-dimensional superimposed gratings has been demonstrated to further increase the number of unique tags. The tagging method was first demonstrated using chromium-on-glass libraries of tags manufactured by e-beam lithography. Two libraries containing tags with up to five su- perimposed gratings were fabricated, one containing 1-dimensional tags, and the other containing 2-dimensional tags. A laser reading system has been developed including a software package that automatically identifies individual tags in the library. Capacity for up 68000 unique 50/iin long 1-dimensional tags and up to 108 unique 50 x 50/xm 2-dimensional tags was demonstrated. The diffractive tags were developed for biological, chemical and medical applications by manufacturing them from the polymer SU8, which is suitable for biochemical functionalisa- tion. A nano-imprint process for creating diffractive tags in SU8 has been developed, that allows for high-throughput manufacturing. A library of 100 different tags were shown to produce high-quality diffraction patterns, recognisable in the laser reading system. Capac- ity for up to 104 unique lOO^xm long 1-dimensional tags and up to 108 unique 100 x 100/LXHI 2-dimensional tags was demonstrated using this manufacturing method. A version of the tagging technology based on holographic writing has been developed. Holograms of binary arrays of spots were written into SU8 doped with a photochromic dye. This version of the technology offers a number of potential advantages, including use of error-checking algorithms and smaller diffraction angles. Capacity for 1014 codes was demonstrated to be theoretically achievable on a 100 x 100/i,m tag. A laser reading system has been developed with a software package that automatically identifies individual holographic tags. Capacity for 1019 tags was demonstrated on bulk photochromic-doped SU8. A dry-etch based method was developed for manufacturing individual particles of SU8 doped with photochromic dye. Capacity for 512 tags has been demonstrated on a 500/u,m particle. Additionally, it was shown that tags written using this technique could be erased and re-written, which is the first demonstration of rewritable microbead tagging.

University of Southampton
Birtwell, Sam William
Birtwell, Sam William

Birtwell, Sam William (2008) Diffractive encoding of microparticles for application to bead-based biological assays. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

A new method for high-capacity encoding of microbeads that allows non-contact optical reading has been developed. In this new approach, a bead is encoded by a number of superimposed gratings with different periods manufactured on the surface of the bead, where each distinguishable tag has a unique combination of superimposed gratings. The tags are read optically at a distance, by detecting the diffraction pattern produced by the superimposed gratings. It has been demonstrated that the tagging method allows for millions of unique and distinguishable tags only a few tens of micrometers in size, when read by visible laser light. Using 2-dimensional superimposed gratings has been demonstrated to further increase the number of unique tags. The tagging method was first demonstrated using chromium-on-glass libraries of tags manufactured by e-beam lithography. Two libraries containing tags with up to five su- perimposed gratings were fabricated, one containing 1-dimensional tags, and the other containing 2-dimensional tags. A laser reading system has been developed including a software package that automatically identifies individual tags in the library. Capacity for up 68000 unique 50/iin long 1-dimensional tags and up to 108 unique 50 x 50/xm 2-dimensional tags was demonstrated. The diffractive tags were developed for biological, chemical and medical applications by manufacturing them from the polymer SU8, which is suitable for biochemical functionalisa- tion. A nano-imprint process for creating diffractive tags in SU8 has been developed, that allows for high-throughput manufacturing. A library of 100 different tags were shown to produce high-quality diffraction patterns, recognisable in the laser reading system. Capac- ity for up to 104 unique lOO^xm long 1-dimensional tags and up to 108 unique 100 x 100/LXHI 2-dimensional tags was demonstrated using this manufacturing method. A version of the tagging technology based on holographic writing has been developed. Holograms of binary arrays of spots were written into SU8 doped with a photochromic dye. This version of the technology offers a number of potential advantages, including use of error-checking algorithms and smaller diffraction angles. Capacity for 1014 codes was demonstrated to be theoretically achievable on a 100 x 100/i,m tag. A laser reading system has been developed with a software package that automatically identifies individual holographic tags. Capacity for 1019 tags was demonstrated on bulk photochromic-doped SU8. A dry-etch based method was developed for manufacturing individual particles of SU8 doped with photochromic dye. Capacity for 512 tags has been demonstrated on a 500/u,m particle. Additionally, it was shown that tags written using this technique could be erased and re-written, which is the first demonstration of rewritable microbead tagging.

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Published date: 2008

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Local EPrints ID: 466587
URI: http://eprints.soton.ac.uk/id/eprint/466587
PURE UUID: b6b5d81f-dce4-4d48-99c7-e452736a26ac

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Date deposited: 05 Jul 2022 05:54
Last modified: 05 Jul 2022 05:54

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Author: Sam William Birtwell

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