WO2009029859A2

WO2009029859A2 - Nanodisks and methods of fabrication of nanodisks

Info

Publication number: WO2009029859A2
Application number: PCT/US2008/074883
Authority: WO
Inventors: Yaowu Hao; Shih-Hsin Chang
Original assignee: Board Of Regents, The University Of Texas
Priority date: 2007-08-31
Filing date: 2008-08-29
Publication date: 2009-03-05
Also published as: WO2009029859A3

Abstract

Structures and methods for use in microarray technologies are provided. One structure includes at least two magnetic layers separated by a nonmagnetic layer. One method includes one or more of said structures in a microarray.

Description

TITLE OF THE INVENTION Nanodisks and Methods of Fabrication of Nanodisks

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of U.S. Provisional Application Number 60/969,471, filed August 31, 2007, herein incorporated by reference.

BACKGROUTVD OF THE INVENTION

[0002] The present invention relates to the general field of scanning or detecting systems and processes. In particular, it relates to structures and processes for magnetic scanning or detecting and making the same.

[0003] First developed in the early 1990s, deoxyribonucleic acid (DNA) microarrays enable researchers to analyze the expression of thousands of genes in a single experiment, providing a powerful tool for scientists trying to understand the fundamental aspects of cellular function and the genetic causes of disease. In recent years, DNA microarray technology has moved out of the research laboratory into a wide variety of practical applications in genetics, pathology, criminology, food safety, and many other fields.

[0004] Fluorescence-label based DNA microarrays are being used commercially. Fluorescence-label based DNA microarrays use fluorescent compounds or labels to contact the DNA strands of interest. The deposited DNA material is then illuminated and emits a fluorescent signal. The emission signal is then collected by an optical system, such as a laser scanner, to detect the DNA strands contacting the label, and transmitted to a detector. However, the current commercial fluorescence-label based DNA microarrays faces several technical challenges, including high cost of the detection equipment (laser scanner), high background fluorescence signal from microarray substrates, scattering of fluorescent signals, and photobleaching of samples when exposed to light.

[0005] Recently, DNA arrays with feature size below 100 nm, so-called "DNA nanoarrays", have emerged to be the next generation of DNA microarrays. These DNA nanoarrays have much higher spot densities than microarrays. They have two most notable advantages: (1) much less analyte materials are needed and (2) diffusion can be the transport mechanism for efficient mixing, avoiding the need for additional instrumentation and laboratory steps for mixing. DNA nanoarrays hold enormous promise for on-site and point-of-care applications. However, as a consequence of the nanoscale size, finding a suitable detection method becomes a major hurdle to this technology. At present, optical detection has been utilized for the detection of nanoarrays. But due to the optical diffraction limit, most fabricated nanoarrays have nanoscale features but are spaced micrometers apart, which greatly enlarge the total array area. At this spacing, it becomes questionable if there is any need for nanoscale features because it is the total array area that defines the amount of required sample and the diffusion length. Densely packed nanoarrays have been explored using gold (Au) nanoparticles as labels and atomic force microscopy (AFM) as the detection method. But they have shown little practical importance for intended on-site and point-of-care applications, where portable, rapid, cost-efficient detection systems are required. [0006] One alternative to fluorescence-label based DNA microarrays are magnetic-label based DNA microarray, also known as magnetic DNA microarray. Magnetic DNA microarray is based on the detection of biologically functionalized magnetic labels using high-sensitivity magnetoresistive magnetic field sensors. Magnetic DNA microarray technology offers several advantages including high-sensitivity detection, stable labeling system, low magnetic background and cheap detection components. In addition, this magnetic detection scheme will provide a practical detection method for DNA nanoarrays, realizing nanoarrays as a next generation of DNA microarrays.

[0007] Commercially available magnetic labels for magnetic DNA microarrays are beads of dispersed iron oxide particles in a polymer. The iron oxide beads typically have a 10-20% of iron oxide in each particle and are required to be in the range of several micrometers to produce enough magnetic fields to be detected. Alternative particles commercially available which may be smaller, often suffer from reduced magnetic moments and broad size distribution. A reduced moment may result in non-detection of the particle and a broad size distribution may result in improperly labeling and subsequent detection. Additionally, magnetic particles for use in magnetic DNA microarrays have been observed to have a lack of size uniformity and the particles tend to aggregate due to magnetic attraction, which may result in embedding a undesirable amount magnetic particles or result in a large size distribution of the labels to provide imprecise readings.

SUMMARY

[0008] Provided herein are systems, methods and compositions for forming structures having desired inter-structure and intra-structure magnetic moments. Included are magnetic DNA microarrays that have a uniform size distribution, a lack of aggregation, and sufficient moment to be detected by a magnetic scanner.

[0009] The systems, methods and compositions are set forth in part in the description which follows, and in part will be obvious from the description, or can be learned by practice of the methods, apparatuses, and systems. The advantages of the systems, methods and compositions will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the systems, methods and compositions, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] For more complete understanding of the features and advantages of the present invention, reference is now made to the detailed description of the invention along with the accompanying figures.

[0011] FIG. IA is a perspective exploded schematic view of one embodiment of the nanodisk structure; FIG. IB is a schematic of the expected hysteresis loop of the multilayer magnetic nanodisk; FIG. 1C is a graph of the hysteresis loop of the nanodisk of the film on the template and the field of plane; FIG. ID is a perspective exploded schematic view of one embodiment of the nanodisk structure; FIG. IE is plane view Scanning Electron Microscope (SEM) micrograph of one embodiment of the nanodisks; and FIG. IF is a graph of the hysteresis loop of one embodiment of the nanodisk with the film on flat substrate and the field of plane. [0012] FIGS. 2A-2I are perspective schematic views of one embodiment of the nanodisk structure formation process.

[0013] FIGS. 3A-3H are side views of one embodiment of a process for forming a nanodisk structure template.

[0014] FIGS. 4A-4B are side views of one embodiment of the process to fabricate the anodic alumina template.

[0015] FIG. 5A is a plane view SEM micrograph of the ultra thin anodic alumina template, and FIG. 5B is a SEM micrograph of the side view of the ultra thin anodic alumina template. [0016] FIGS. 6A-6E are side views of one embodiment of processes of fabricating the nanodisks. [0017] FIGS. 7A-7B are side views of one embodiment of the process to fabricate the pillar templates using the anodic alumina template.

[0018] FIGS. 8A-8F are side and perspective views of one embodiment of a coupling and scanning nanodisk process on a microarray.

[0019] FIGS. 9A-9D are side and perspective views of another embodiment of a coupling and scanning nanodisk process on a microarray.

[0020] FIG. 10 is an illustration of magnetic multiplexing using the nanodisks.

[0021] FIG. 11 is a side view of one embodiment of a coupling of the nanodisk to a non-DNA molecule on a microarray.

[0022] FIG. 12 is a perspective exploded schematic view of one embodiment of the nanorod structure.

DESCRIPTION OF THE INVENTION

[0023] Although making and using various embodiments are discussed in detail below, it should be appreciated that the various embodiments provides many inventive concepts that may be embodied in a wide variety of contexts. The specific aspects and embodiments discussed herein are merely illustrative of ways to make and use the invention, and do not limit the scope of the invention.

[0024] In the description which follows like parts may be marked throughout the specification and drawing with the same reference numerals, respectively. The drawing FIGS, are not necessarily to scale and certain features may be shown exaggerated in scale or in somewhat generalized or schematic form in the interest of clarity and conciseness

[0025] Structures and methods for manufacturing the structures are provided to form magnetic nanodisks for use in magnetic microarrays. The nanodisk comprises alternating layers of magnetic and non-magnetic materials to provide a detectable moment with minimal or no interstructure or inter-nanodisk magnetic interaction. "Microarray" is any kind of biological assay including, but not limited to, DNA microarrays, such as cDNA microarrays and oligonucleotide microarrays, microRNA chips, protein microarrays, tissue microarrays, transfection microarrays (also called cell microarrays), chemical compound microarrays, antibody microarrays, and gene chip analysis.

[0026] FIG. IA illustrates one embodiment of an exploded schematic view of a structure for use in a microdevice, such as a microarray. In one embodiment, the structure comprises a nanodisk 100 comprising a first non-magnetic layer 110 separating at least two layers of magnetic material. The two layers of magnetic material comprise a first magnetic layer 120 and a second magnetic layer 140, wherein the first magnetic layer 120 includes a soft magnetic material and the second magnetic layer 140 comprises a hard magnetic material. The first and second magnetic layers 120 and 140 and the first nonmagnetic layer 110 include a disk-like shape, comprising a first circular face 122, a second circular face 124, a diameter D, and a thickness T between the first and second circular face 122 and 124, as shown in FIG. IA. In one embodiment, the first and second magnetic layers 120 and 140 and the nonmagnetic layer 110 form a trilayer 126, which includes magnetic nanodisks 100 ranging from about 10 to about 200 nm in size and can generate a sufficient magnet signal for biosensing with a magnet sensor. The magnetic nanodisks 100 are single domain nanodisks, since breaking into two domains will greatly increase the exchange and anisotropy energy. The trilayer magnetic nanodisks are permanent nanomagnets, wherein the first and second magnetic layers 120 and 140 attract each other. The first nonmagnetic layer 110 includes an interlayer magnetostatic coupling between the first and second magnetic layers 120 and 140 to cause a very low remanent moment, as shown in FIG. 1C, which is a graph of the hysteresis loop of one embodiment of the nanodisk. FIG. IB is schematic of the expected hysteresis loop of the trilayer nanodisk. Therefore, the trilayer nanodisks do not attract other trilayer nanodisks, i.e. cause inter-nanodisk aggregation. The nonmagnetic layer 110 serves as an artificial domain wall layer to separate the two magnetic domains of the first and second magnetic layers 120 and 140. The hysteresis loop of the nanodisks 100 includes a very low remanence due to the magnetostatic interaction between the first and second magnetic layers 120 and 140. The first and second magnetic layers 120 and 140 include two magnetic domains with magnetizations that point to the opposite direction to minimize the magnetostatic energy.

[0027] The nanodisk 100 may have a shape selected from the group of disk-like, circular, annular, round, elliptical, hexagonal, octagonal, parabolic disk, hyperbolic disk, or similar shape, and combinations thereof as well as any shaped formed in the template/substrate on which it is formed. The direction of the magnetism is influenced by the shape of the materials, i.e. the shape anisotropy. For example, nanodisks 100 with rectangular or elliptical shapes have a primary direction of magnetization determined by shape anisotropy, for example, magnetism prefers to align to the longest axis among three axes. At remanence, the magnetizations of the two magnetic layers relax back to the long axis direction, and the two magnetizations point to the opposite direction. The magnetic moments from the two magnetic layers cancel with each other, which leads to a very low remanent moment. A relatively harder material can serve as the soft layer since shape anisotropy rotates the magnetization into the opposite direction of the hard layer, with the alignment to the long axis. For a circular nanodisk configuration, shape anisotropy between two magnetic layers become of minimal influence in the magnetism direction, and the magnetization direction will be determined by magnetocrystal anisotropy. Magnetocrystal anisotropy refers to the concept that magnetization prefers to align to a certain crystal direction and the energy cost per atom to align its magnetization from one crystallographic direction to another. The polycrystalline nature of the magnetic layers, the direction that the magnetization relaxes back to at remanence can be random. If the soft layer includes a small value for the magnetocrystal anisotropy, the minimization of magnetostatic energy forces its magnetization to the opposite direction of the hard layer. [0028] In another embodiment of the nanodisk 100 as shown in FIG. ID, the structure comprises a nanodisk 100 having a stack of interlayers including the first non-magnetic layer 110, the first magnetic layer 120 disposed on first non-magnetic layer 110, a second nonmagnetic layer 130 disposed on the first magnetic layer 120, the second magnetic layer 140 disposed on the first non-magnetic layer 130, and a third non-magnetic layer 150 disposed on the second magnetic layer 140. Optionally, the nanodisk 100 may further comprise a sacrificial layer 105 on which the first non-magnetic layer 110 may be disposed. The first and second magnetic layers 120 and 140, the first, second, and third nonmagnetic layers 110, 130, and 140, and the sacrificial layer 105 include a disk-like shape, comprising a first circular face, a second circular face, a diameter D for the disk, and a thickness T between the first and second circular face. The nanodisk 100 may have a diameter or width between about 1 nanometer and about 200 nanometers, such as between about 20 nanometers and about 100 nanometers, for example, about 65 nanometers. The nanodisk 100 may have a shape selected from the group of disk-like, circular, annular, round, elliptical, hexagonal, octagonal or similar shape, and combinations thereof as well as any shaped formed in the template/substrate on which it is formed. The first and second magnetic layers 120 and 140, the first, second, and third nonmagnetic layers 110, 130, and 140 may be facially coupled with each respective layer, such that there are no gaps between interlayers. FIG. IE is plane view SEM micrograph of one embodiment of the nanodisks. FIG. IF is a graph of the hysteresis loop of a bulk multilayer nanodisks with the film on flat substrate and the field of plane.

[0029] The nanodisks 100 may have a magnetic moment between about 0.05 fAm² and about 1.5 fAm², such as between about 0.1 fAm² and about 0.5 fAm², for example, about 0.1 fAm². The nanodisks may have an intra-structure magnetic interaction field between about 5 Oersteds and about 1000 Oersteds, such as between about 10 Oersteds and about 100 Oersteds, and an inter-structure magnetic interaction field comprises between about 0.01 Oersteds and about 5 Oersteds, such as between about 0.1 Oersteds and about 1 Oersteds.

[0030] The first non-magnetic layer 110 is a non-magnetic material selected from the group consisting of gold, silver, platinum, silicon oxide, silicon, silicon nitride, aluminum oxide, aluminum nitride, titanium, titanium oxide, and combinations thereof. The second non-magnetic layer 130 may be selected from the group consisting of gold, silver, platinum, copper, silicon, silicon oxide, silicon nitride, aluminum oxide, aluminum nitride, ruthenium, titanium, titanium oxide, and combinations thereof. The third non-magnetic layer 150 may be selected from the group consisting of gold, silver, platinum, silicon oxide, silicon, silicon nitride, aluminum oxide, aluminum nitride, titanium, titanium oxide, and combinations thereof. The third non-magnetic layer comprises a material capable of forming a thiol-metal linkage, such as gold, which can provide for nucleic acid attachment. Nucleic acids that may be attached include, deoxyribonucleic acid (DNA), including, but not limited to, complementary DNA (cDNA), genomic DNA (gDNA), multicopy single-stranded DNA (msDNA), and mitochondrial DNA (mtDNA); ribonucleic acid (RNA), including, but not limited to, messenger RNA (mRNA) (pre- mRNA/ heterogeneous nuclear RNA hnRNA), transfer RNA (tRNA), ribosomal RNA (rRNA), antisense RNA (aRNA), guide RNA (gRNA), microRNAs (miRNA), non-coding RNA (ncRNA), Piwi-interacting RNA (piRNA), small hairpin RNA (shRNA), small interfering RNA (siRNA), small nuclear RNA (snRNA), small nucleolar RNA (snoRNA), smalltTemporal RNA (stRNA), trans-acting siRNA (ta-siRNA), and transfer-messenger RNA (tmRNA); nucleic acid analogues, including, but not limited to GNA, LNA, PNA, TNA, and morpholino; variable number tandem repeats (VNTR), short tadem repeat (STR), oligonucleotides, single nucleotide polymorphism (SNP), and cloning vectors, including, but not limited to, phagemid, plasmid, lambda phage, cosmid, Pl phage, fosmid, BAC, YAC, and HAC. Alternatively, the third nonmagnetic layer may be configured with a ligand and/or antibody to bind to a receptor/antigen of interest as described below. The third nonmagnetic layer may comprise aminodextran layer to provide the surface chemistry of attachment or conjugation of antibodies, ligands, or small molecules. Alternatively, the third nonmagnetic layer may comprise a silica layer and be functionalized with amine or carboxyl groups to covalently coupled the antibodies, ligands, or small molecules. Alternatively, the third nonmagnetic layer may comprise gold with its known affinity for biomolecules, especially for its ability to bind to proteins and thiols. The third non- nonmagnetic layer 150 may be deposited from the same materials at the same layer thicknesses as the first non-magnetic layer 110. Two or more layers of the non-magnetic layers 110, 130, and 150, may comprise the same material.

[0031] The first non-magnetic layer, second non-magnetic layer, and third non-magnetic layer may each have variable thicknesses based on the desired structure size and desired magnetic properties. For example, each of the first non-magnetic layer, second non-magnetic layer, and third non-magnetic layer may have respective thicknesses between about 1 nanometers (nm) and about 200 nm. Two or more layers of the non-magnetic layers 110, 130, and 150, may have the same thickness. Alternatively, second nonmagnetic layer 130 may have a thickness greater than the thicknesses of the first and third nonmagnetic layers 110, 150. For the first nonmagnetic layer to serve as artificial domain wall, the thickness may be more than 1 nm, regardless of the thicknesses of two magnetic layers. However, different thicknesses of the first nonmagnetic layer may give different magnetic properties. For example, simulation studies may determine the exact correlation between different thicknesses and different magnetic properties. [0032] Optionally, the nanodisk may further comprise a sacrificial layer 105 on which the first non-magnetic layer 110 may be disposed, as shown in FIG. ID. The sacrificial layer 105 provides a base structure on which the nanodisk layer may be deposited. The sacrificial layer 105 is disposed on a template and the shape, such as a disk-like, round, elliptical, hexagonal, octagonal or similar shape, of the sacrificial layer reflects the shape of the template on which it is disposed. The sacrificial layer 105 may comprise a salt, such as Group I or II metal salt selected from the group of sodium chloride, potassium chloride, or combinations thereof. Alternatively, the sacrificial layer 105 may comprise a metal, such as one selected from the group of copper, silver, aluminum, and combinations thereof, and may be dissolved in an aqueous solution of metal etchants. Preferably, the sacrificial layer 105 is a salt that may be dissolved in water. The sacrificial layer may be deposited to a thickness between about 20 nanometers and about 200 nanometers.

[0033] The first magnetic layer 120 is a soft magnetic material having a magnetization (magnetic moment) between about 600 emu/cm and about 1750 emu/cm , for example about 880 emu/cm³. Suitable materials for the first magnetic layer include soft magnetic materials selected from the group consisting of iron, iron-silicon alloys, iron-aluminum alloys, iron-cobalt alloys (Permendur) having greater than 50 wt.% of iron, nickel, nickel-iron alloys (permalloy), soft ferrites, and combinations thereof. Soft ferrites refer to materials with the chemical formula of MOFe₂O₃, with M is a transition metal selected from the group consisting of such as nickel, iron, manganese, magnesium, zinc, and combinations thereof. Soft ferrites have magnetic switching fields of less than 50 Oersteds.

[0034] The second magnetic layer 140 is a hard magnetic material having a magnetic switching field greater than the magnetic switching field of the first magnetic layer 120, in one embodiment. A magnetic switching field refers to the external field needed to change the direction of magnetization in a magnetic material. The second magnetic layer 140 may include a magnetic switching field between about 50 Oersteds and about 1000 Oersteds, for example about 100 Oersteds. Suitable materials for the second magnetic layer include hard magnetic materials selected from the group consisting of cobalt, cobalt-nickel alloys, cobalt-iron alloys having 50 wt.% or more of cobalt, cobalt-platinum alloys, cobalt-samarium alloys, aluminum-nickel-cobalt alloys, BaO₆Fe₂O₃, SrO₆Fe₂O₃, iron-neodymium-boron alloys, samarium-iron-nitrides, and combinations thereof.

[0035] The first magnetic layer 120 thickness may vary on the desired nanodisk size and desired magnetic properties. The first magnetic layer 120 may be deposited to a thickness between about 3 nanometers (nm) and about 70 nm, such as between about 7 nm and about 30 ran, for example, about 18 nanometers, for a nanodisk having a diameter or width between about 1 nanometers and about 200 nanometers, such as between about 30 nm and about 100 nm. The second magnetic layer 140 may be deposited to a thickness between about 3 nanometers (nm) and about 70 nm, such as between about 7 nm and about 30 nm, for example, about 10 nanometers, for a nanodisk having a diameter or width between about 1 nanometers and about 200 nanometers, such as between about 30 nm and about 100 nm. The first magnetic layer 120 may have a thickness of the same or greater than the second magnetic layer 140. Alternatively, the second magnetic layer 140 may have a thickness of the same or greater than the first magnetic layer 120.

[0036] The respective thickness of the first magnetic layer 120 and the second magnetic layer 140 may also be defined by equation (1). Equation (1) provides the means for providing a sufficient low remanent magnetic moment to avoid aggregation due to magnetic attraction. Equation (1) is defined as follows: thard^hard " t_softM soft (1) where /w and t_sof_t are the respective thicknesses of the hard magnetic layer, layer 140, and the soft magnetic layer, layer 120. M '_hard and Af_5O/? are the magnetizations (Af) of the hard magnetic layer 140 and the soft magnetic layer 120, respectively. In one embodiment of the nanodisk, the ratio of the thickness to the diameter is within a ratio of between about 1:3 and about 1 :20, such as between about 1:3 and about 1:10. For example, for a nanodisk having a diameter between about 20 nm and about 200 nm, the thickness may be between about 6 nm and about 70 nm. [0037] The presence of the materials having different abilities to change the respective magnetizations as described for magnetic layers 120 and 140 herein provides for two respective magnetizations to point in opposite directions. The layers 120 and 140 respectively provide for a magnetic "soft" material 120, which is defined as having a magnetic switching field between about 0.1 Oersteds and 50 Oersteds, and a magnetic "hard" material 140 having magnetocrystal anisotropy between greater than 50 Oersteds and about 1000 Oersteds. Magnetic materials, such as used for magnetic layer 120, have been observed to have a magnetic switching field between about 1 Oersted and 50 Oersteds, such as between about 5 Oersteds and about 30 Oersteds. [0038] The direction of the magnetism may also be influenced by the shape of the materials, as discussed previously. For example, sandwich nanomagnets with rectangular or elliptical shapes have a primary direction of magnetization determined by shape anisotropy, for example, magnetism prefers to align to the longest axis among three axes. For circular nanodisk configuration, shape anisotropy between two magnetic layers become of minimal influence in the magnetism direction, and magnetization direction will be determined by magnetocrystal anisotropy.

[0039] At remanence, the magnetizations of the two magnetic layer 120 and 140 change back to the longest axis direction, and the respective magnetizations of the magnetic layer materials 120 and 140 point to the opposite direction. As such, the respective magnetic moments from the two magnetic layers 120 and 140 cancel with each other and the nanodisk has a resulting remanent moment between about 0.0001 fAm² and about 0.01 fAm², for example about 0.002 fAm² or 0.005 fAm².

[0040] The interlayer magnetostatic coupling between two magnetic layers causes a very low remanent moment, such as between about 0.001 fAm² and about 0.01 fAm², for example about 0.005 fAm². The nonmagnetic layer serves as an artificial domain wall to separate the two magnetic domains. The magnetizations in the two domains will point to the opposite direction to minimize the magnetostatic energy, and the two magnetic layers will attract to each other in one nanodisk. As such the interstructure magnetic fields of the nanodisks will be insufficient to result in attraction between the different nanodisks in solution, and prevent any aggregation of the nanodisks.

[0041] The nanodisk 100 provides a saturation moment of between about 0.05 fAm² and about 1.5 fAm², such as between about 0.1 fAm² and about 1 fAm², for example, 0.1 fAm², which would be detectable by a standard magnetic field sensor for a nanodisk larger than 30 nm. [0042] The magnetic properties of a collection of nanodisks can be measured with any standard commercial magnetometers, such as vibrating sample magnetometer, alternating gradient magnetometer, magneto-optical Kerr effect magnetometer and superconducting quantum interface device (SQUID) magnetometer using standard measuring processes known to one of ordinary skill in the art. A single nanodisk' s magnetic properties may be measured by magnetic force microscopy (MFM), which is an operational mode of Atomic Force Microscopy (AFM) with a cantilever coated with magnetic materials, using standard measuring processes known to one of ordinary skill in the art.

[0043] Alternatively, the nanodisk 100 can comprise more than two magnetic layers separated by additional nonmagnetic layers, i.e. including multiple trilayers 126, as to form a nanorod 200, as shown in FIG. 12. For the nanorod, the height or thickness T^_R will exceed the diameter D^_R, such that the thickness T^_R and the diameter D^_R are at a ratio ranging from about 1 : 1 to about 5:1. For example, the nanorod 200 can comprise a third magnetic layer 142 and fourth magnetic layer 144 separated by a fourth nonmagnetic layer 152, wherein the third magnetic layer 142 is disposed on the third nonmagnetic layer 150 of the nanodisk 100 and a fifth nonmagnetic layer may serve as an attachment point for DNA and other molecules of interest, as shown in FIG. 12. The trilayer 126 includes the first and second magnetic layers 120 and 140 separated by the first nonmagnetic layer 130. The third magnetic layer 142 includes a soft magnetic material and the fourth magnetic layer 144 includes a hard magnetic material, as described above. If the third magnetic layer 142 is disposed on the third nonmagnetic layer 150, the third nonmagnetic layer 150 must be a sufficient thickness to separate the third magnetic layer from the second magnetic layer 140 as to prevent interaction between the third magnetic layer and the second magnetic layer 140. For example, the thickness of the third nonmagnetic layer 150 may be about 20 to about 250 nm. The nanorod 200 with the third and fourth magnetic layers can provide an increased magnetic signal for detection purposes.

[0044] FIG. 2A is a perspective schematic view of one embodiment of the nanodisk 100 formation process. The nanodisk 100 may be formed in one embodiment by a support post membrane or a template growth method. In the support post membrane or the template method, a membrane or template 160 having support posts or pillars 185 formed therein, as shown in Step 250 of FIG. 2A, is provided to a deposition apparatus. The deposition apparatus may include an electrodeposition cell, chemical vapor deposition (CVD) apparatus, and the like. The template 160 may serve as a working electrode with a metal film in the electrodeposition cell. The nanodisk 100 material layers including the sacrificial layer are then deposited on the support posts 185 and the membrane or template 160, as shown in Step 260 of FIG. 2 A. Alternatively, and not shown, the nanodisk 100 material layers may be selectively deposited on the support posts 185 without any of the nanodisk materials 100 being deposited on the membrane or template 160 surface. The template 160 may then be exposed to a solution dissolving the nanodisks 100 from the template 160 as shown in Step 270. The support posts 185 of the template 160 can be resusable after cleaning the deposited materials on the substrate bottom. [0045] FIGS. 2B-2I are schematic perspective views further detailing one embodiment of the nanodisk layering process 200. A template 160 is provided for the formation of the nanodisk 100 thereon in step 210 as shown in FIG. 2B. The template 160 may comprise any suitable material such as an anodic aluminum oxide, and may also comprise a membrane material, such as titanium oxide (TiO₂). The template 160 includes a first side 167, a second side 169, and a plurality of apertures 162 formed in the template from the first side 167 to the second side 169 as shown in FIG. 2B. The template 160 may be between about 100 nanometers and about 60,000 nanometers thick. Alternatively, some of the apertures 162 may not be formed completely from the first side 167 to the second side 169. A template structure for depositing the nanodisk materials thereon may also be manufactured from patterning processes including anodic alumina, nanosphere lithography, interference lithography, block copolymer lithography, and imprint lithography in addition to the process described herein.

[0046] The template 160 may comprise a material selected from the group of anodic aluminum oxide, silicon, silicon dioxide, titanium dioxide, and combinations thereof. Alternatively, the template 160 may comprise a membrane material including titanium oxide. The template 160 may be designed to provide for the formation of nanodisk structures between about 1 nm and about 1000 nm in size, for example between about 10 nm and about 500 nm in size. The template provides for a patterned of apertures 162 formed therein. The apertures 162, for example, may be between about 20 nm and about 100 nm. Further, the apertures 162 may have a ratio of height to width of between about 1:1 and about 1000:1, such as between about 10:1 and about 400:1, for example, about 200:1. The apertures may have cross-sectional shapes that are elliptical, circular, hexagonal, octagonal, prismatic, or combinations thereof. The template 160 may be configured to provide for the formation of between about 1x10 and about 1x10 nanodisks per cm².

[0047] A backside layer 170 may be deposited on a second side 169 in Step 220 as shown in FIG. 2C. The backside layer 170 may comprise a material that is suitable for electrochemical deposition processes, such as electroplating or electroless deposition. Suitable backside layer materials include silver, copper, gold, platinum, zinc, tin, lead, and combinations thereof. The backside layer may be deposited to a thickness between about 200 nanometers and about 3000 nanometers, such as between about 400 nm and about 1000 nm, for example, about 500 nm. The backside layer 170 may also be deposited by a method selected from the group of physical vapor deposition (sputtering), evaporation, chemical vapor deposition, and combinations thereof. [0048] A metal fill layer 180 is then deposited in the apertures 162 of the template 160 at Step 230 as shown in FIG. 2D. The metal fill layer 180 may be a deposited thickness less than or equal to that of the length of the aperture, for example, the thickness of the template, or for example, the aperture's depth if not formed substantially from first side to the second side. In one embodiment of the metal fill layer 180 deposition process, the metal fill layer 180 may be deposited between 10% and 20% of the depth of the aperture. For example, for an aperture having a depth of 60,000 nm, the metal fill layer 180 may be deposited to between about 6,000 nm and about 12,000 nm. The metal fill layer 180 comprises a metal material selected from the group of gold, copper, silver, platinum, zinc, lead, tin, and combinations thereof. The metal fill layer 180 may be deposited by an electrochemical deposition process including electroplating or electroless deposition. Alternatively, the metal fill layer may be deposited from a process for depositing in the features with limited deposition on the pillars of the structures, for example, collimated physical vapor deposition.

[0049] The second side 169 is planarized to remove the backing layer 170 and expose the exposed metal fill layer material 180 on surface 165 at Step 240 and as shown in FIG. 2E. The planarization process may be performed by methods known in the art, for example, by chemical mechanical polishing, chemical etching, or a combination thereof.

[0050] Portions of the template 160 are then selectively removed from the surface 165 to form the support structures or posts 185 at Step 250 and as shown in FIG. 2F. The template surface 165 may be selectively removed compared to the metal fill layer material 180 by an etching process or other material removal step. Etching may include wet etching, where the material is dissolved when immersed in a chemical solution or dry etching, where the material is sputtered or dissolved using reactive ions or a vapor phase etchant. In one embodiment of the etching process, sufficient amounts of the template are removed to provide for exposing the posts 185 at a height equal to or greater then the subsequently deposited materials, such that a portion or all of a sacrificial layer disposed on the posts will be exposed to the respective dissolving solution for removal of the disks following later deposition. Alternatively, between about 50 nm and about 500 nm, such as between about 100 nm and about 300 nm, for example, about 150 nm of the template 160 material may be removed to form the exposed post 185 structure shown in FIG. 2F. The layers 105, 110, 120, 130, 140, and 150, respectively of sodium chloride (NaCl)/ gold (Au)/nickel-iron (NiFe)/gold (Au)/cobalt (Co)/gold (Au), may be deposited as described above at Step 260 as shown in FIG. 2G. Alternatively, an additional step may chemically functionalize the nonmagnetic layer 150 with antibodies, receptors, or ligands, which are described below. [0051] The formed nanodisks 190 may then be removed from the template post structures 185 by dissolving the sacrificial layer 105 in a suitable composition at Step 270 as shown in FIG. 2H. For example, water may be used to dissolve a sacrificial layer 105 of salt or an acid/metal etchant may be used to dissolve a metal sacrificial layer. Suitable metal etchants may be obtained from Transene, Inc., of Danvers, Massachusetts. The free nanodisks 190 in the solution as shown in FIG. 2H may then be used in processing with the microarrays. The same solution used to remove or store the nanodisks may be used to supply the nanodisks to the DNA arrays as appropriate. Alternatively, nanodisks will be washed and then dispersed again into appropriate solutions to provide the nanodisks to the respective DNA arrays. Alternatively, an additional step may chemically functionalize the nonmagnetic layer 150 with antibodies, receptors, or ligands, which are described below.

[0052] Alternatively, at Step 270, the template 160 may be dissolved in a suitable composition to separate the nanodisks 100 from the template 160 as shown in FIG. 21. In such an embodiment, the sacrificial layer 105 of the nanodisk 100 may not be deposited in the process for forming the nanodisk 100. The unused deposited material 100' disposed on the template 160 may be removed and the template 160 may then be reused for generation another series of nanodisks according to the processes described herein.

[0053] In an alternative manufacturing process, the nanodisks 100 may be formed by the use of a porous alumina membrane with a thickness of about 10 μm or greater. In this process, a sacrificial layer, such as the materials of the sacrificial layer, for example, copper, is sputtered or vaporized on one side of the membrane to form a structure. The layers 110, 120, 130, 140, and 150, such as gold (Au)/nickel-iron (NiFe)/gold (Au)/cobalt (Co) /gold (Au) are deposited in the membrane pores as respectively described herein. Multiple nanodisks 100 may be deposited in the same membrane by repeating the steps of deposition of a sacrificial layer followed by deposition of the layers 110, 120, 130, 140, and 150 of the nanodisk 100. The membrane and the sacrificial layer may then be dissolved.

[0054] An example of a template forming process includes providing an anodic aluminum oxide material having about 1x10⁹ apertures of about 65 nm in diameter with an aspect ratio of height to width of about 200:1 formed therein. A backside layer of silver is deposited on the template to a thickness of about 500 nm. A metal fill layer of gold is then deposited by electroplating in the apertures to a depth of about 6000 nanometers. The backside layer is then removed by chemical mechanical polishing. A portion of the template is then etched by a process/solution including sodium hydroxide to remove about 0.2% of the template material to expose about 100 nanometers of the metal fill layer above the etched anodic aluminum oxide surface. A sacrificial layer of sodium chloride may be deposited by an evaporation process to a thickness of about 30 nanometers on the etched anodic aluminum oxide surface. A first gold layer is deposited by an evaporation process to a thickness of about 10 nanometers on the sodium chloride sacrificial layer. A magnetic layer of nickel-iron (NiFe) is deposited on the first gold layer by an evaporation process to a thickness of about 18 nanometers. A second gold layer is deposited by an evaporation process to a thickness of about 10 nanometers on the nickel-iron layer. A magnetic layer of cobalt (Co) is deposited by an evaporation process to a thickness of about 10 nanometers on the second gold layer. A third gold layer is deposited by an evaporation process to a thickness of about 10 nanometers on the cobalt layer. The deposited materials and the template are then exposed to water to dissolve the sodium chloride sacrificial layer. [0055] In a further alternative manufacturing embodiment an anodic aluminum template may be formed by depositing a metal layer, such as gold, on a substrate, depositing a dielectric layer on the metal layer, and depositing an aluminum layer on the metal layer. Alternatively, the dielectric layer may be omitted from this process. A positive voltage is applied in the presence of an acid to form an oxide layer with a parallel array of nominally cylindrical apertures to the dielectric layer. The dielectric layer may be etched to expose the underlying metal layer. Metals, such as silver, may then be deposited in the apertures. The aluminum oxide layer may then be removed to form an array of pillars of the electrodeposited metal materials. [0056] Dielectric material templates, such as silicon and silicon based oxide templates can be formed by depositing colloidal spheres to form a lithographic mask over the dielectric substrate surface. A reactive ion etching process may be used to remove the exposed dielectric materials under the colloidal sphere lithographic mask. The etching processes results in the formation of pillars formed from the materials masked by the spheres.

[0057] FIGS. 3A-3H are side views of one embodiment of a process 300 for forming a nanodisk structure template using a lithographic mask approach or nanosphere lithography. A substrate 301 is provided as shown in FIG. 3 A at Step 300. The substrate may comprise a dielectric material. Examples of suitable dielectric materials are selected from the group consisting of silicon oxide, silicon, and combinations thereof. The spheres (or spherical or substantially spherical structures) 305 may be deposited on the substrate surface, preferably as a mono-layer of particles. The nanospheres 305 may comprise an inorganic material, such as silica, or a polymeric material, such as polystyrene or polystyrene latexes. The nanospheres 305 may be nanospheres each having a respective diameter in the range between about 10 nm and about 10,000 nm, such as in the range between about 80 nm and about 200 nm, for example about 100 nm. [0058] Alternatively, the substrate surface may be pretreated with a surface modifying compound before deposition of the nanospheres 305. The surface modifying compound may be used to form a positively charged surface for attraction and/or retention of the nanospheres 305. For example, a SiO₂ or Si substrate may be modified with a cationic surfactant to form a self- assembled monolayer (SAM) of nanospheres resulting in a positively charged surface. Nanospeheres 305, such as polystyrene nanospheres, with anionic charges can then be adsorbed onto the substrates surface from solution by electrostatic interactions. Surface modifying compounds for silicon (Si, with or without native silicon oxide) and silicon oxide (SiO₂) may include trichlorosilanes or trialkoxysilanes with functional groups having positive charges, for example, the surfactant 3-aminopropyl)triethoxysilane (APTES), and cationic surfactants to silicon (with or without native silicon oxide) and silicon oxide (SiO₂) surfaces, such as dodecylpyridinium chloride. Alternatively, a combination of the surface modifying compounds described herein may be used.

[0059] Optionally, the nanospheres, such as polystyrene nanospheres, may be etched or have material removed therein to produce a reduced diameter nanosphere 307 at Step 310 as shown in FIG. 3B. For example, the diameter of polystyrene nanospheres may be reduced by oxygen plasma. The process may be used to reduce the nanospheres between about 10% and about 60%, for example about 35%.

[0060] A first mask material 315 may be deposited on the reduced diameter nanospheres 307 and the surface of the substrate 301 at Step 330 as shown in FIG. 3C. The first mask material 315 may be aluminum, copper, or combinations thereof, and may be deposited by evaporation. The first mask material 315 may be deposited to a thickness between about 10 nm and about 50 run. As the nanospheres 307 perform as a surface for deposition of the first mask material, the first mask material is not deposited on the surface of the substrate 301 beneath a portion or the entire diameter the nanospheres 307.

[0061] The nanospheres 307 are removed from the substrate 301 and expose portions 325 of the substrate without a first mask material 315 disposed thereon at Step 340 as shown in FIG. 3D. The nanospheres 307 may be removed by dissolving the nanospheres in a solution containing one or more solvents from benzene, toluene, xylene, ethylbenzene, methylene chloride, chloroform, carbon tetrachloride, pyridine, acetone, dioxane, dimethylformamide, methyl ethyl ketone, diisopropyl ketone, cyclohexanone, tetrahydrofuran, n-butyl phthalate, methyl phthalate, ethyl phthalate, tetrahydrofurfuryl alcohol, ethyl acetate, butyl acetate, 1-nitro- propane, carbon disulfide, tributyl phosphate, cyclohexane, methylcyclohexane, ethylcyclohexane, or combinations thereof. The expose portions may have a diameter of the same or similar diameter or width as described for posts 185 described above, and, for example, may have a width or diameter between about 20 ran and about 180 nm.

[0062] The exposed portion 325 of the substrate 310 may then be etched to remove a portion of the substrate and form apertures 335 therein at Step 350 as shown in FIG. 3E. The etching process may be a reactive ion etching process or any other type of etching process suitable for removing the substrate material. The apertures 335 may be etched to a depth between about 10 nm and about 50 nm.

[0063] A second mask material 345 may be deposited on the substrate surface and in the apertures 335 at Step 360 as shown in FIG. 3F. The second mask material may be deposited to a thickness of the depth of the apertures 335, and alternatively, may be deposited to a thickness less than the depth of the apertures 335. The second mask material 345 may be chromium, titanium, tungsten, or combinations thereof, and may be deposited by a method including physical vapor deposition, chemical vapor deposition, evaporation, or combinations thereof. [0064] A solution may be used to dissolve the first mark material, such as sodium hydroxide (NaOH) for an aluminum layer, thereby removing the second mask material disposed thereon. Alternatively and optionally, the surface of the substrate 301 may be planarized to remove the first mark material 315, the second mark material 345, and any substrate material disposed above the second mask material 345 formed in the apertures 335 from the surface of the substrate 301 at Step 370 as shown in FIG. 3G. The planarization process may include chemical mechanical polishing or other process known in the art.

[0065] The surface of the substrate 301 may then be etched a second time to form support structures or posts 355 at Step 380 as shown in FIG. 3H. The substrate may be etched as described above. The substrate surface may be etched to a depth between about 30 nm and about 500 nm. Alternatively, the second mask material 345 may be removed from the substrate surface during or following the etching process. The nanodisk materials as described herein may then be deposited on this template as per the nanodisk formation process described herein. [0066] In one embodiment, an ultra thin anodic alumina template 700 may be used in the template growth fabrication process. One embodiment of the ultra thin anodic alumina template 700 is as shown in FIG. 5A as a plane view SEM micrograph. "Ultra thin" includes the thicknesses of less than about 1 μm, such as less than about 500 nm, or less than 200 nm. One embodiment of the thickness of the ultra thin anodic alumina template 700 is shown in FIG. 5B, as a side view of the template. The anodic alumina template 700 includes a plurality of pores 710, and the pore 710 size can range from 15 nm to 100 nm. The pores 710 may not be ordered, but the size distribution is narrow. To make the template 700, an aluminum layer 720 is evaporated on top of a sacrificial layer 730 and a substrate 732, as shown in FIG. 4A. A thin layer of aluminum 720 is evaporated on top of the sacrificial layer 730 on a doped silicon substrate. The doped silicon substrate provides for a semiconductive layer that allows for the thin layer of aluminum 720 to be anodized Then, during an anodization step 800 shown in FIG. 4B, in a simple two-electrode cell where the anode is aluminum metal, the application of a positive voltage (anode versus cathode) ranging from 10 to 100 Volts in the presence of cold (temperature from 4⁰C to 3O⁰C) oxalic acid with concentration from 0.1 to 0.5 mol/L results in an oxide layer that contains a parallel array of nominally cylindrical holes 710 between the anodic alumina 712. These hole templates can be directly used to make nanodisks by electrodeposition or evaporation of multilayers into the holes, as shown in FIG. 6A-6E. The hole template 600 includes a plurality of nanosize holes 610, a conductive layer 612 for electrodeposition,or a sacrificial layer 612 for lift-off. The sacrificing layer 612 can be Cu, Al, NaCl, or SiO₂, and will be deposited at the bottom for releasing the mutilayer nanodisks into solution. Different materials will be either electrodeposited 630 or vacuum evaporated 640 into template holes 610, as shown in FIGS. 6B and 6C, respectively. Hole templates 600 need to be dissolved 650, as shown in FIG. 6D. Then, the sacrificing layer 612 is dissolved 660 to release to release the nanodisks 100 into solution. Alternatively, before the dissolution of the sacrificing layer 612, an additional step may chemically functionalize the nonmagnetic layer 150 with antibodies, receptors, or ligands, which are described below.

[0067] Also, a pillar template 750 can readily be generated by step 810 of casting a polymer solution 760 into the template 700, followed by curing step 820 curing the polymer, as shown in FIG. 7 A. And then a peeling step 830 as shown in FIG. 7B, peeling the polymer off the template 700 and flip it over to generate the pillar template 750. Then using pillar template processes shown in FIG. 2A to make nanodisks. [0068] Detection of Magnetic Nanodisks

[0069] In one embodiment, the nanodisks 100 may be disposed on DNA and detected according to a magnetic field sensor, such as a magnetoresistive sensor, as shown in FIGS. 8A- 8F and 9A-9D. For deposition processes, the DNA single strands 410 are disposed on a microarray 400, which may comprise discrete deposition of DNA material in a pattern on a suitable substrate material, such as silicon, silicon oxide, glass, or combinations thereof, for example, a glass slide as shown in FIG. 8A and FIG. 9 A. The attachment of DNA to glass surfaces can be accomplished by a covalent bond to a chemical matrix (via epoxy-silane, amino- silane, lysine, polyacrylamide or others), such as a poly-L-lysine linkage to DNA, alternatively, probe DNA are attached via epoxy groups embedded into a polymer coating layer on the substrate material. Alternatively, DNA attachment to the glass substrate may be accomplished by conventional spotting or ink-jet printing, printing with fine-pointed pins onto glass slides, photolithography using pre-made masks, photolithography using dynamic micromirror devices, or electrochemistry on microelectrode arrays. The DNA material includes DNA single strands 420 having a first characteristic, such as the same DNA sequence, and DNA single strands 430 having a second characteristic, such as different DNA sequences. Such DNA single strands 420 and 430 may bind to the same DNA molecule of interest, for example, the DNA single strands 420 and 430 may be different DNA analogues, which are nucleic acid compounds structurally similar (analog) to naturally occurring RNA and DNA. Alternatively, all of the DNA single strands 420 may bind to different DNA molecules of interest.

[0070] Referring to FIGS. 8B-8F, analyte single strand DNA materials are extracted from a sample to be tested through standard DNA purification and denaturation protocols. Some of the analyte single strand DNA materials are complementary to the specific probe single strand DNAs 410 on the microarray surface 400. The analyte single strand DNA materials are modified with thiol group, such as a S-H bond, in FIG. 8B, which are called thiolated DNAs 435. The thiolated DNAs 435 are introduced to the microarray surface 400, and hybridize with the single strand DNAs 420, 430. The thiolated DNAs 435 strands are immobilized such as by a hybridization process with single stand DNA materials 430, which immobilized strands 440 are shown in FIG. 8C. The unbound analyte single strand DNA materials are then removed from the microarray 400, such as being washed from the microarray surface. The microarray 400 is then exposed to a solution containing nanodisks 100 as described herein and shown in FIG. 8D. The nanodisks can then be immobilized on selected DNA materials 450 by the thiol-metal linkage, such as thiol-gold bond of the nanodisks. Any non-immobilized nanodisks 100 may then be removed from the microarray as shown in FIG. 8E, such as being washed from the microarray surface. The microarray 400 may then be scanned, such as along path 480, by a magnetic field 460 sensor that produces an electrical signal 470 to a computer (not shown) as shown in FIG. 8F. Alternatively, a magnet can expose the immobilized nanodisks to a magnetic field for the detection of the magnetic field sensor. The sensor will be able to identify which DNA materials 450 have nanodisks that will allow determination of which DNAs the sample possesses. The detection of DNA materials may be used for quantification purposes, diagnostic purposes, purification purposes, gene expression profiling, comparative genomic hybridization, SNP detection, alternative splicing detection, chromatin immunoprecipitation, or in a tiling array. For example, after the DNA materials 450 have been bound, the microarray substrate may be heated to denature the DNA materials 450 to release the DNA materials 450 from the microarray 400. The released single strand DNA material 435 may then be purified by magnetic separation with the nanodisks still being attached to the DNA material 435 due to the thiol-gold bond, and then may be sequenced and/or multiplied through polyermase chain reaction (PCR) protocols. Alternatively, the detection of DNA materials may be used for quantification purposes by quantifying the number of electrical signals 470 produced by the magnetic field sensor, quantification may be achieved by using known volumes of analyte single strand DNA materials from a sample. Diagnostic purposes may be achieved if DNA materials are detected above a specified threshold, pattern, or indication for disease.

[0071] Referring to FIGS. 9B-9D for an alternative approach, analyte single strand DNA materials are extracted from a sample to be tested. Some of the analyte single strand DNA materials are complementary to the specific probe single strand DNAs 410 on the microarray 500 surface. The analyte single strand DNA materials are modified with thiol group and are coupled to nanodisks 100 through thiol-metal, such as thiol-gold linkage, to form nanodisk-DNA conjugates 540 as shown in FIG. 9B. The nanodisk-DNA conjugates 540 are introduced to the microarray 500 surface, and the analyte DNA portion of the nanodisk-DNA conjugates 540 will hybridize to the corresponding complementary probe single stand DNAs 420 and 430, such as single strand DNAs 430, and the nanodisk-DNA conjugates 540 will be immobilized on those strands 550 as shown in FIG. 9C. Any non-immobilized nanodisk-DNA conjugates 540 may then be removed from the microarray by a wash solution, as shown in FIG. 9D. The microarray 500 may then be scanned, such as along path 580, by a magnetic field 560 sensor that produces an electrical signal 570 to a computer (not shown) as shown in FIG. 9E. The sensor 560 will be able to identify which DNA materials 550 have nanodisks that will allow determination of which DNAs the sample possesses.

[0072] Once the nanodisks 100 are disposed on the respective DNA strands to form a detectable structure 450, one or more magnetic sensors 460, such a maganetoresistive sensor is scanned across the DNA arrays 400 to detect magnetic fields. The detected magnetic fields of the magnetic-nanodisk labeled microarray surface are then converted into an electronic signal and forwarded to a process for assembling the data for analysis. Examples of suitable sensors are a read head inside the computer hard disk, a magnetic tunneling junction sensor, and combinations thereof. The computer hard disk includes a magnetoresistive sensor to detect extremely small magnetic objects is already convincingly demonstrated in every personal computer. Suitable scanners include those with scanner read heads, sensors, which are utilized in computer hard disks. Other suitable sensors include magnetic tunnel junction sensors (MTJ) which include two magnetic layers separated by an insulating spacer layer. [0073] A MTJ detector is constructed with a thin insulating tunnel barrier, such as alumina, and the sense current flows perpendicular to the film plane. If the insulating layer (also referred to as the "barrier layer") is sufficiently thin, electrons can flow by quantum mechanical tunneling through the barrier layer. For tunneling between two magnetized materials, the tunneling current is maximum if the magnetization directions of the two electrodes are parallel and minimum then they are aligned anti-parallel. Therefore, the tunneling current, and therefore the resistance of the device, will change as external magnetic fields alter the magnetic orientation of these two electrodes. Electron tunneling between two ferromagnetic electrodes is controlled by the relative magnetization of the two ferromagnetic electrodes, i.e., tunneling current is high when they are parallel and low when antiparallel. A typical MTJ detector is composed of a bottom electrode, magnetic multilayers including a tunnel barrier, and a top electrode. MTJ detectors have magnetoresistance ratios as high as 50% and inherently large device resistances, yielding higher output voltage signals.

[0074] In addition, the nanodisks 100 are compatible with "magnetic multiplexing". The concept of magnetic multiplexing 900 is illustrated in FIG. 10. A magnetic saturation field is the applied external field needed for nanodisks to reach their saturation magnetic moment. The magnetic saturation field comprises a first magnet 910 with a low saturation field and a second magnet 920 with a high saturation field. At a first magnetic field 930, only the first magnet 910 is magnetic and the second magnet 920 is non-magnetic. At a second field 940, both the first and second magnet 910 and 920 are magnetic. Under different applied magnetic fields, nanodisks with different saturation fields can appear strongly magnetic or almost non-magnetic. For multilayered magnetic nanodisks, saturation fields are determined by the strength of magnetocrystal anisotropy and magnetostatic interaction between two magnetic layers. Magnetocrystal anisotropy is a material property with a wide range of values, from very soft to very hard magnetic materials. The magnetostatic interaction between two layers is determined by the separation spacing, i.e. the thickness of the non-magnetic spacing layer, and the interaction strength is inversely propositional to cube of the separation spacing. Multilayered magnetic nanodisks can be designed and produced to have very different saturation fields but with similar sizes by choosing different materials and layer thicknesses.

[0075] Any standard hybridization protocol may be used. For example, double-stranded DNA of interest is heated in a hybridization buffer buffered for pH to separate the separate or denature double-stranded DNA into single strand DNA molecules due to the hydrogen-bonded base pairing becoming thermodynamically unfavorable. The denatured single strand DNA is then mixed with the probe DNA attached to the substrate 400. The combined sets are then cooled slowly to allow the single strand DNA to anneal to complementary probe DNA and form a "hybridized" DNA molecule. [0076] Detecting Non-DNA molecules and Cells

[0077] The nonmagnetic layer can be configured with various molecules possessing compatible binding ligands and/or antibodies to detect to a particular molecule or cell of interest. The ability to chemically functionalize the nonmagnetic layer enhances the utility in other biological applications besides DNA detection. Selectively binding ligands and/or antibodies to the nonmagnetic layer allows additional detection between the nanodisk and other biological molecules and between cells and the nanodisks. It is therefore possible to attach various molecules possessing a compatible binding ligand and/or antibodies to the nonmagnetic layers. Alternatively, different nonmagnetic layers may detect multiple molecules with different ligands and/or antibodies directed to different nonmagnetic layers. A protein microarray, sometimes referred to as a protein binding microarray, is a piece of glass on which different molecules of protein have been affixed at separate locations in an ordered manner thus forming a microscopic array. An antibody microarray is a specific form of protein microarrays, a collection of capture antibodies are spotted and fixed on a solid surface, such as glass, plastic and silicon chip for the purpose of detecting antigens. Accordingly, a microarray substrate 400 may include ligands/antibodies 950 bound to the microarray substrate 400 which selectively bind a particular receptor/antigen of interest, as shown in FIG. 11. The receptor/antigen of interest 960 is then introduced onto the microarray substrate 400 with the bound ligands/antibodies, such that the receptor/antigen of interest 960 is immobilized by the ligand or antibody on the substrate. Then the nanodisks 970 with the ligand/antibody 950 selectively disposed to bind to the receptor/antigen of interest are introduced to the immobilized receptor/antigen of interest on the substrate, such that the nanodisks bind to the immobilized receptor/antigen of interest. Unbound antigens and nanodisks are then removed by washes and then the microarray substrate is scanned with a magnetic field sensor to produce an electrical signal for the detection of the antigen of interest.

[0078] In one embodiment, the material for the nonmagnetic layer is gold. The gold layer can be first coated with streptavidin, which will adsorb spontaneously from an aqueous solution. Biotinylated antibodies will bind with steptavidin providing a good coating. Several other ways of attaching of antibodies onto the gold surface include forming a monolayer of polylysine or copolymer of lysine and cysteine on to the gold surface and attaching periodate oxidized antibody in the presence of sodiumcyano-borohydride on to this monolayer. Alternatively, the antibody may be reduced with dithiotreitol or with some other reductant and the reduced antibody chemisorbs directly on to the gold surface. This method is preferred if the nonmagnetic layer is very thin, having a thickness of half of an antibody molecule.

[0079] The nonmagnetic layer may be modified with functional groups. The functional groups may be atoms or groups of atoms that are capable of further chemical reactivity such as reacting with a ligand or antibody to attach the ligand or antibody to the nonmagnetic layer, or to bind a molecule of interest. Further, different layers of the nonmagnetic layers may be functionalized with different functional groups, providing multiple discrete functional regions that are spatially resolved along the length of the nanodisk with different ligands and/or antibodies. For example, the third nonmagnetic layer may comprise a metal oxide or a metal with a native oxide layer whose surface can be functionalized with a functional group such as a carboxylic acid group. The second nonmagnetic layer may comprise a non-magnetic substrate, such as gold, which can be functionalized with a thiol group. Thus, the nanodisk with different nonmagnetic layers may be functionalized with two independent functional groups wherein each functional group may have different chemical properties.

[0080] Such functional groups may be capable of interacting directly with a molecule or cell of interest in the methods of the present invention. However, the functional group may serve to link or attach to the nanodisk to a secondary molecule or ligand that is capable of interacting with a molecule or cell of interest in the methods of the present invention. In embodiment, different ligands are linked to different nonmagnetic layers of the nanodisk.

[0081] In the process of linking a ligand to the nonmagnetic layer via a functional group, the functional group may be first attached to the nonmagnetic layer, and then the nonmagnetic layer may be reacted with the ligand to tether the ligand to the nonmagnetic layer. Alternatively, the ligand itself may be derivatized so as to contain a functional group suitable for linking it directly to the nonmagnetic layer. Some suitable secondary molecules may inherently possess a "functional group" (e.g. the sulfhydryl groups of cysteine residues, and the carboxy- and amino- terminal functional groups of polypeptides) that are suitable for directly reacting with a segment of a wire.

[0082] Other molecular groups may also be included in the linking arrangement. For example, linear or branched alkyl chains or other polymers may be introduced between the nonmagnetic layer and a ligand in order to, for example, position the ligand further from the surface of the nonmagnetic layer, or to offer the possibility of introducing more than one ligand per functional group to order to increase ligand density on the nonmagnetic layer. Those of skill in the art will recognize that there are many strategies for attaching useful ligands to the nonmagnetic layers. All such variations and modifications are intended to be encompassed by the embodiments disclosed herein.

[0083] Examples of ligands which are suitable for use in the practice of the present invention include, but are not limited to, molecules and macromolecules such as proteins and fragments of proteins, peptides and polypeptides, antibodies, receptors, enzymes, substrates, substrate analogs, ribozymes, structural proteins, nucleic acids such as DNA and RNA and DNA/RNA hybrids, saccharides, lipids, various hydrophobic or hydrophillic substances, lipophilic materials, chemoattractants, enzymes, hormones, fϊbronectin, and the like. Further, such molecules and macromolecules may be naturally occurring or synthetic in nature. The term ligand may also include larger entities such as cells, tissues, entire microorganisms, viruses, etc. [0084] For example, the nonmagnetic layer can be configured to bind to a peptide, to a protein, to a nucleic acid, or to a cell. Optionally, the nonmagnetic layer is configured to bind to an extracellular domain of a protein or transmembrane domain. A variety of cell types can also be targets of the nonmagnetic layer for detection. For example, cells can be selected from one or more of a neoplastic cell, a squameous cell, a transitional cell, a basal cell, a muscle cell, an epithelial cell, a lymphocyte, a leukocyte, a monocyte, a red blood cell, and a mucosal cell. Binding ligands or fragments thereof can be used to bind the nonmagnetic layer to cellular, or other endogenous or exogenous biomarkers. Such biomarkers can include, but are not limited to, proteins, polypeptides, peptides, polysaccharides, lipids, or antigenic portions thereof. When binding mechanisms are used to bind a cell, the nonmagnetic layer can be optionally internalized by the targeted cell. The target ligands can target cells selected from the group consisting of a lung, bronchus, intestine, stomach, colon, heart, brain, blood vessel, cervix, bladder, urethra, skin, muscle, liver, kidney and blood.

[0085] Thus, binding nonmagnetic layer can be targeted to a variety of cells for detection, cell types, antigens (endogenous and exogenous), epitopes, cellular membrane proteins, organs, markers, tumor markers, angiogenesis markers, blood vessels, thrombus, fibrin, and infective agents. The term "epitope" is meant to include any determinant capable of specific interaction with a targeting ligand as described below. Epitopic determinants can consist of chemically active surface groupings of molecules such as amino acids or sugar side chains and can have specific three dimensional structural characteristics, as well as specific charge characteristics. [0086] Optionally, the target can be a protein, and can be a protein with an extracellular or transmembrane domain. Optionally, the target can be the extracellular domain of a protein, a lipid, a virus, a polymer, a toxin, a pharmaceutical compound, a biohazard compound, and an explosive compound.

[0087] Desired targets for detection can be based on, but not limited to, the molecular signature of various pathologies, organs and/or cells. Targeting ligands specific for a molecule that is expressed or over-expressed in a cell, tissue, or organ targeted for imaging, such as precancerous, cancerous, neoplastic, or hyperproliferative cells, tissues, or organs, can be used with the nonmagnetic layers described herein. This use can include the detection, or diagnosis of precancerous, cancerous, neoplastic or hyperproliferative cells in a tissue or organ. The compositions and methods of the invention can be used or provided in diagnostic kits for use in detecting and diagnosing cancer, disease, viruses, and the like. The term "ligand" refers to any entity capable of specifically or non-specifically binding to, attracting, localizing in proximity to, or detecting the presence of a target molecule.

[0088] As used herein, a cancer to be detected or diagnosed can be selected from, but are not limited to, the group comprising lymphomas (Hodgkins and non-Hodgkins), B cell lymphoma, T cell lymphoma, myeloid leukemia, leukemias, mycosis fungoides, carcinomas, carcinomas of solid tissues, squamous cell carcinomas, adenocarcinomas, sarcomas, gliomas, blastomas, neuroblastomas, plasmacytomas, histiocytomas, melanomas, adenomas, hypoxic tumors, myelomas, AIDS-related lymphomas or sarcomas, metastatic cancers, bladder cancer, brain cancer, nervous system cancer, squamous cell carcinoma of head and neck, neuroblastoma/glioblastoma, ovarian cancer, skin cancer, liver cancer, melanoma, squamous cell carcinomas of the mouth, throat, larynx, and lung, colon cancer, cervical cancer, cervical carcinoma, breast cancer, epithelial cancer, renal cancer, genitourinary cancer, pulmonary cancer, esophageal carcinoma, head and neck carcinoma, hematopoietic cancers, testicular cancer, colo-rectal cancers, prostatic cancer, or pancreatic cancer.

[0089] Pre-cancerous conditions to be imaged, detected or diagnosed include, but are not limited to, cervical and anal dysplasias, other dysplasias, severe dysplasias, hyperplasias, atypical hyperplasias, and neoplasias. As would be clear to one skilled in the art, however, additional cancers and pre-cancerous conditions can be detected or diagnosed using the methods and apparatuses described herein.

[0090] Targeting ligands, such as polyclonal or monoclonal antibodies, can be used to detect a molecule or cell. Thus, the nonmagnetic layer can further comprise a fragment of an antibody. Monoclonal antibodies can be obtained from a population of substantially homogeneous antibodies, i.e., the individual antibodies comprising the population are identical except for possible naturally-occurring mutations that can be present in minor amounts. [0091] Non-immunoglobulin polypeptides can be substituted for the constant domains of an antibody of the invention, or they can be substituted for the variable domains of one antigen- combining site of an antibody of the invention to create a chimeric bivalent antibody comprising one antigen-combining site having specificity for a first antigen and another antigen-combining site having specificity for a different antigen. Chimeric or hybrid antibodies also can be prepared in vitro using known methods in synthetic protein chemistry, including those involving crosslinking agents.

[0092] Bispecific antibodies are based on the coexpression of two immunoglobulin heavy chain- light chain pairs, where the two heavy chains have different specificities Because of the random assortment of immunoglobulin heavy and light chains, these hybridomas (quadromas) produce a potential mixture of 10 different antibody molecules, of which only one has the correct bispecific structure. Heteroconjugate antibodies are also within the scope of the described compositions and methods. Heteroconjugate antibodies are composed of two covalently joined antibodies. Heteroconjugate antibodies can be made using any convenient cross-linking methods. [0093] A variety of immunoassay formats can be used to select antibodies that selectively bind with a desired target site or target site antigen. For example, solid-phase ELISA immunoassays are routinely used to select antibodies selectively immunoreactive with a protein, protein variant, or fragment thereof. The binding affinity of a monoclonal antibody can, for example, be determined by the Scatchard analysis.

[0094] The nonmagnetic layer can also comprise a targeting ligand that is a polypeptide or a fragment thereof. Optionally, polypeptides that are internalized by target cells can be attached to the surface of a nonmagnetic layer. Ligands that are internalized can optionally be used for internalization of a nonmagnetic layer into a target cell. Thus nonmagnetic layers can comprise a polypeptide or fragments thereof that interact with a desired target. A nonmagnetic layer can also comprise a binding domain of an antibody or phage.

[0095] The term "polypeptide" or "peptide" is used broadly herein to mean two or more amino acids linked by a peptide bond. The term "fragment" or "proteolytic fragment" also is used herein to refer to a product that can be produced by a proteolytic reaction on a polypeptide, i.e., a peptide produced upon cleavage of a peptide bond in the polypeptide. A fragment can be produced by a proteolytic reaction, but it should be recognized that a fragment need not necessarily be produced by a proteolytic reaction but can be produced using methods of chemical synthesis or methods of recombinant DNA technology, to produce a synthetic peptide that is equivalent to a proteolytic fragment. It should be recognized that the term "polypeptide" is not used herein to suggest a particular size or number of amino acids comprising the molecule, and that a polypeptide of the invention can contain up to several amino acid residues or more. [0096] Thus, a nonmagnetic layer can be compared to a control nonmagnetic layer having all the components of the nonmagnetic layer except the targeting characteristics, such as, for example, targeting ligand or polypeptide. By detecting the magnetic data from the nonmagnetic layer bound to a desired target site versus a control nonmagnetic layer, the specificity or selectivity of binding or internalization can be determined. If an antibody, polypeptide, or fragment thereof, or other targeting ligand is used, selective or specific binding to a target can be determined based on standard antigen/polypeptide/epitope/antibody complementary binding relationships. Further, other controls can be used. For example, the specific or selective targeting of the nonmagnetic layers can be determined by exposing nonmagnetic layers to a control, which includes all the components of the detection solution except for the desired target ligand or epitope. To compare a control sample to a test sample, levels of magnetic detection can be detected by, for example, the systems described above and the difference in levels or location can be compared. [0097] A targeting ligand can be coupled to the surface or shell of at least one of the nonmagnetic layer. Nonmagnetic layers comprising targeting ligands can be produced by methods known in the art. For example ligands, including but not limited to, antibodies, peptides, polypeptides, or fragments thereof can be conjugated to the nonmagnetic layer surface. [0098] Any method known in the art for conjugating a targeting ligand to a nonmagnetic layer can be employed. Established protocols have been developed for the labeling metallic nonmagnetic layers with a broad range of biomolecules, including protein A, avidin, streptavidin, glucose oxidase, horseradish peroxidase, and IgG (antibodies). Nonmagnetic layers can be prepared with bioorganic molecules on their surface (cDNA, antibodies, avidin, phospholipids, etc). The nonmagnetic layers can be characterized, modified, and conjugated with organic and biomolecules. Polymers or other intermediate molecules can be used to tether antibodies or other targeting ligands to the surface of nonmagnetic layers. Methods of tethering ligands to nonmagnetic layers are know in the art.

[0099] Covalent binding of a targeting ligand to a nonmagnetic layer can be achieved, for example, by direct condensation of existing side chains or by the incorporation of external bridging molecules. Many bivalent or polyvalent agents can be useful in coupling polypeptide molecules to other particles, proteins, peptides or amine functions. Examples of coupling agents are carbodiimides, diisocyanates, glutaraldehyde, diazobenzenes, and hexamethylene diamines. [00100] Optionally, one can first derivatize an antibody if used, and then attach the nonmagnetic layer to the derivatized product. As used herein, the term "derivatize" is used to describe the chemical modification of the antibody substrate with a suitable cross-linking agent. Examples of cross-linking agents for use in this manner include the disulfide-bond containing linkers SPDP (N-succinimidyl-3-(2-pyridyldithio)propionate) and SMPT (4-succinimidyl-oxycarbonyl-α- methyl-α(2-pyridyldithio)toluene).

[00101] Targeting ligands/antibodies can also be conjugated to nonmagnetic layers using methods including the preparation of biotinylated antibody molecules and their consequent interaction with streptavidin/nonmagnetic layer conjugates. This approach takes advantage of strong biospecific interaction between biotin and streptavidin and known protocols for immobilization of streptavidin on nonmagnetic layers. Polypeptides with thiol terminated alkyl chains can be directly attached to the surface of nonmagnetic layers. For conjugation procedure one can use a mixture of thiol terminated polypeptides and relatively small mercaptoacetic molecules to avoid high density immobilization of the polypeptides.

[00102] Nonmagnetic layers can be prepared with a biotinylated surface and an avidinated antibody, peptide, polypeptide or fragment thereof can be attached to the nonmagnetic layer surface using avidin-biotin bridging chemistry. Avidinated nonmagnetic layers can be used and a biotinylated antibody or fragment thereof or another biotinylated targeting ligand or fragments thereof can be for detection. For example, a biotinylated targeting ligand such as an antibody, protein or other bioconjugate can be used. Thus, a biotinylated antibody, targeting ligand or molecule, or fragment thereof can bind to a desired target in the detection scheme. Once bound to the desired target, the nonmagnetic layer with an avidinated surface can bind to the biotinylated antibody, targeting molecule, or fragment thereof. An avidinated nonmagnetic layer can also be bound to a biotinylated antibody, targeting ligand or molecule, or fragment thereof for a detection scheme.

[00103] When using a nonmagnetic layer with a biotinylated surface or an avidinated surface a targeting ligand can be used. For example, a biotinylated targeting ligand such as an antibody, polypeptide or other bioconjugate, or fragment thereof, can be used for detection and allowed to accumulate at a target site [00104] When a nonmagnetic layer with a biotinylated surface is used, an avidin linker molecule, which attaches to the biotinylated targeting ligand can be used for detection. Then, a nonmagnetic layer with a biotinylated shell can be used for detection. The nonmagnetic layer binds to the avidin linker molecule, which is bound to the biotinylated targeting ligand, which is itself bound to the desired target. In this way, a three step method can be used to target nonmagnetic layers to a desired target. The targeting ligand can bind to all of the desired targets detailed above as would be clear to one skilled in the art. [00105] EXAMPLES

[00106] The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how the compositions, compositions, articles, devices, systems, and/or methods claimed herein are made and evaluated, and are intended to be purely exemplary and are not intended to limit the scope of compositions, compositions, articles, devices, systems, and/or methods. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.), but some errors and deviations should be accounted for.

[00107] EXAMPLE 1: Nanodisk

[00108] For example, a nanodisk configuration of respective layers 140, 130, and 120 of CoNi/Au/FeNi is formed. Gold (Au) is provided as the nonmagnetic material of material 130. Layer 140 comprises CoNi, which serves as the magnetic "hard" layer with cobalt (Co) providing a magnetization of about 1440 emu/cm³, and a magnetic switching filed of about 450 Oersteds. The presence of nickel (Ni) can increase the corrosion resistance. Layer 120 comprises FeNi, such as Fe₂₀Ni₈₀ alloy, which serves as the magnetic "soft" layer with a magnetization of about 800 emu/cm³, and a magnetic switching filed of about 50 Oersteds. The presence of Ni element also helps to increase the corrosion resistance.

[00109] The nanodisk may also include a gold (Au) material 110 including a thickness of about 10 nanometers, the nickel-iron (NiFe) layer 120 of a thickness of about 18 nanometers, the gold (Au) material 130 of a thickness of about 10 nanometers, the cobalt (Co) layer 140 of a thickness of about 10 nanometers, and a gold (Au) material 150 of a thickness of about 10 nanometers.. The nanodisk is disk-like or circular in shape and has a diameter of about 65 nanometers and has the magnetic properties of a magnetic moment of about 0.1 fAm², an intra-structure magnetic interaction field of about 65 Oersteds, an inter-structure magnetic interaction field of about 0.01

Oersteds, and aremanent moment of about 0.005 fAm².

[00110] EXAMPLE 2: Chemical Functionalization of Nonmagnetic layers

[00111] Dithiobissuccinimidylundecanoate (DSU) has been found to be able to immobilize proteins onto ultra flat gold surfaces. Monolayers of DSU on gold nonmagnetic layers can be formed by immersing the nanodiscs in 1.5 ml DSU solutions (1 rnM in MeOH) for 30 min at room temperature. After rinsing with 7 mlMeOH, N-hydroxysuccinimidyl (NHS)-terminated nonmagneticlayers can dried under a stream of nitrogen followed by immediate immobilization of antibodies onto the gold nonmagnetic layer.

[00112] The nonmagnetic layers may be functionalized by placing the nanodisks in 20 mL ethanol solution containing 20 mM octane thiol (capable of interacting with Au). The nanodisks may be allowed to react at room temperature for 1 hour. The nanodisks can then be collected by placing a magnetic stir bar outside of the reaction flask and decanting the solution. The nanodisks may be rinsed with excess ethanol and isolated via magnetic field exposure.

[00113] While specific alternatives to steps of the invention have been described herein, additional alternatives not specifically disclosed but known in the art are intended to fall within the scope of the invention. Thus, it is understood that other applications of the present invention will be apparent to those skilled in the art upon reading the described embodiment and after consideration of the appended claims and drawing.

Claims

CLAIMSWhat is claimed is:

1. A nanodisk comprising: a first magnetic layer including a soft magnetic material and a second magnetic layer including a hard magnetic material, wherein a first non-magnetic layer separates the first and second magnetic layers to provide a detectable moment with minimal inter-nanodisk magnetic interaction.

2. The nanodisk of Claim I₅ wherein the first magnetic layer includes a first magnetic field and the second magnetic layer includes second magnetic field greater than the first magnetic field of the first magnetic layer.

3. The nanodisk of Claim 2, wherein the first magnetic layer and the second magnetic layer include a disk-like shape comprising a diameter and a thickness, and the ratio between the thickness and diameter is below about 1 :3.

4. The nanodisk of Claim 3, wherein the first magnetic layer, the second magnetic layer, and the first nonmagnetic layer comprise a disk-like shape selected from a group of circular, elliptical, rectangular or similar shape and combinations thereof.

5. The nanodisk of Claim 4, wherein the hard magnetic material is selected from the group of cobalt, cobalt-nickel alloys, cobalt-iron alloys, cobalt-platinum alloys, cobalt-samarium alloys, aluminum-nickel-cobalt alloys, BaO₆Fe₂O₃, SrO₆Fe₂O₃, iron-neodymium-boron alloys, samarium-iron-nitrides, and combinations thereof.

6. The nanodisk of Claim 5, wherein the soft magnetic material is selected from the group of iron, iron-silicon alloys, iron-aluminum alloys, iron-cobalt alloys, nickel, nickel-iron alloys MOFe₂O₃, soft ferrites, and combinations thereof, and M is a transition metal selected from the group consisting of such as nickel, iron, manganese, magnesium, zinc, and combinations thereof.

7. The nanodisk of Claim 6, further comprising a third non-magnetic layer disposed on the second magnetic layer, wherein the third nonmagnetic layer is disposed to selectively bind a molecule of interest.

8. The nanodisk of Claim 7, further comprising the first magnetic layer disposed on the first non-magnetic layer, a second non-magnetic layer disposed on the first magnetic layer, and the second magnetic layer disposed on the second non-magnetic layer.

9. The nanodisk of Claim 8, wherein the first, second, and third non-magnetic layers each comprise a material selected from the group of gold, silver, platinum, silicon oxide, silicon, silicon nitride, aluminum oxide, aluminum nitride, titanium, titanium oxide, and combinations thereof.

10. The nanodisk of Claim 9, wherein the nanodisk has a magnetic moment between about 0.05 fAm² and about 1.5 fAm², and a remanence between about 0.001 fAm² and about 0.01 fAm².

11. The nanodisk of Claim 10, wherein the first magnetic layer has a first magnetism of about 800 emu/cm³ and the second magnetic layer has a second magnetism of about 1440 emu/cm .

12. The nanodisk of Claim 11, wherein the nanodisk has a diameter of between about 20 nanometers and about 100 nanometers.

13. The nanodisk of Claim 7, wherein each of the first non-magnetic layer, the first magnetic layer, the second non-magnetic layer, the second magnetic layer, and the third nonmagnetic layer have a thickness between about 1 nanometers and about 25 nanometers.

14. The nanodisk of Claim 6, wherein at least one of the first non-magnetic layer and the third non-magnetic layer comprises a material adapted to provide a thiol-metal linkage.

15. The nanodisk of Claim 1, wherein an intra-nanodisk magnetic interaction field is between about 5 Oersteds and about 1000 Oersteds, and the nanodisk has an inter-structure magnetic interaction field between about 0.1 Oersteds and about 1 Oersteds.

16. A method for forming an anodic alumina template comprising: a. doping a substrate with a semiconductive material; b. providing a sacrificial layer on the substrate; c. evaporating an aluminum layer on the sacrificial layer; and d. anodizing the aluminum layer with an acid to form an ultra thin anodic alumina template including a parallel array of cylindrical holes.

17. The method of Claim 16, wherein the semiconductive material comprises doped silicon.

18. The method of Claim 16, wherein the evaporated aluminum layer includes a thickness of about 50 to about 500 nm.

19. The method of Claim 16, further comprising casting a polymer solution into the ultra thin anodic alumina template and curing the polymer solution to form a pillar template.

20. A process for detecting a molecule comprising the steps of: a. providing a substrate including a first molecule bonded to the substrate; b. providing a second molecule disposed to selectively bind to the first molecule; c. contacting the second molecule to the first molecule under conditions suitable for selective binding; d. providing a nanodisk disposed to selectively bind to the second molecule; e. contacting the nanodisk and second molecule under conditions suitable for selective binding of the nanodisk to the second molecule to immobilize the nanodisk to the substrate; and f. detecting the immobilized nanodisk.

21. The process of Claim 20, wherein the nanodisk comprises a plurality of magnetic layers separated by a first non-magnetic layer to provide a detectable moment with minimal inter- nanodisk magnetic interaction.

22. The process of Claim 21, wherein the first molecule is a nucleic acid and the second molecule is a nucleic acid.

23. The process of Claim 21, wherein the first molecule is an antibody and the second molecule is a protein selectively binding to the antibody.

24. The process of Claim 21, wherein the second molecule is selected from the group consisting of a nucleic acid, a peptide, a protein, an antigen, a lipid, a virus, a polymer, a toxin, a pharmaceutical compound, a biohazard compound, and an explosive compound.

25. The process of Claim 21, wherein the detecting step comprises scanning the immobilized nanodisk structure with one or more magnetic sensors and detecting the magnetic fields of the magnetic-nanodisk labeled microarray surface

26. The process of Claim 21, further comprising converting the magnetic field into an electronic signal and forwarding the electronic signal to a process for assembling the data for analysis.

27. The process of Claim 21, wherein the magnetic sensors is selected from the group consisting of a read head inside the computer hard disk, a magnetic tunneling junction sensor, and combinations thereof.

28. The process of Claim 21, wherein the substrate is selected from the group consisting of silicon, silicon oxide, glass, and combinations thereof.