Browse Prior Art Database

Microfabricated optically encoded particles

IP.com Disclosure Number: IPCOM000016421D
Original Publication Date: 2003-Jan-21
Included in the Prior Art Database: 2003-Jun-21
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Abstract

Disclosed is a device comprised of particles made from layers of reflective, refractive or absorptive materials to achieve a large number of distinctively "colored" particles which may be optically decoded for sizes down to the micrometer scale. Such distinctive particles are currently of interest as carriers of distinctive biomolecules, such as DNAs, as they allow parallel measurements of many different molecules, each identifiable through the encoded particle. In commercially available embodiments such particles are commonly available as polymer beads loaded with varying amounts of spectrally distinct dyes or colored particles.

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Microfabricated optically encoded particles

  One embodiment of this invention uses multiple laminated dielectric and partially reflective layers to obtain specified reflectance at multiple wavelengths using optical interference phenomena. A structure showing such a laminated structure is shown in the figure below. A series of partial reflectors, Ri, and dielectric spacer layers, Di ,are specified to create the desired reflection amplitudes at specific reflected wavelengths for a specific illumination angle. A simple example might involve a single dielectric layer of optical thickness lamda/2 and a reflective layer with R1=0.5. At normal incidence illumination, optical interference will lead to a reflectance maximum, and apparent color, at wavelength lamda. By stacking such layers, a series of such reflectance maxima can be built up with different reflection amplitudes at a series of different wavelengths. The number of distinct spectral characteristics which may be specified is given by the product of the number of distinguishable reflectance amplitudes times the number of dielectric layers. The particle shown below has a fully reflective core, which is optional or may be located at various positions within the stack. This core can be made magnetic so as to aid in alignment of the particle relevant to the illumination source by including magnetic materials which have a magnetic moment which is aligned in, perpendicular to, or specifically canted relative to, the plane of the particle.[1] Surface layers are included to allow chemical derivitization, passivation, etc of some of the particle surfaces. Obviously their dielectric and reflectivity properties must be included in the analysis as appropriate. It is also possible to obtain some degree of alignment by making the mass distribution within the particle assymmetric so that gravimetric effects can induce preferred orientations.

An alternative embodiment might involve the use of layered, spectrally distinct optically materials, either independently or in combination with the reflectiv...