Holographically encoded microparticles for bead-based assays

Birtwell, Sam W., Banu, Shahanara, Zheludev, Nikolay I. and Morgan, Hywel (2009) Holographically encoded microparticles for bead-based assays. Journal of Physics D: Applied Physics, 42 (5), 55507. (doi:10.1088/0022-3727/42/5/055507).

Abstract

We demonstrate a re-writable, high capacity holographic encoding technique for multiplexed bead-based suspension assays. The microparticles are made from SU8 doped with a photochromic diarylethene dye and manufactured using multilayer photolithography and dry etching. Each particle is encoded with a unique hologram, whose diffraction pattern consists of bright and dark regions, representing a binary number that identifies the particle. Theoretically up to 10²⁴ unique codes are available on a 100 µm particle using this method, when the code is read with a standard 2/3" CMOS camera. Encoding capacities of 512 unique codes have been demonstrated on a 500 µm SU8 particle. The code is thermally stable for 3 days at 25 °C, and once written, the code can be erased and re-written once whilst still remaining readable. The code can be written into the particle during an assay experiment (no pre-encoding is required) and requires simple optics for reading.

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Contributors

Author: Nikolay I. Zheludev

Author: Hywel Morgan

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