Methods, devices, and systems for controllable magneto-photonic particles (e.g., for light delivery and/or collection) are provided. In one aspect, a magneto-photonic particle includes a supporting material, a photonic structure configured to manipulate light, and a magnetic structure controllable to make the particle move. The photonic structure and the magnetic structure are supported by the supporting material.

TECHNICAL FIELD

This present disclosure is related to controllable signal delivery and/or collection.

BACKGROUND

The ability to deliver and collect light to and from a target spot in a medium has broad relevance for applications across biology and biomedicine, from neural stimulation and imaging to drug delivery and thermotherapy.

SUMMARY

The present disclosure provides methods, devices, systems for controllable magneto-photonic particles, e.g., for light collection and delivery.

One aspect of the present disclosure features a particle including: a supporting material; a photonic structure configured to manipulate light; and a magnetic structure controllable to make the particle move, where the photonic structure and the magnetic structure are supported by the supporting material.

In some embodiments, the photonic structure is configured to diffract, steer, reflect, focus, scatter, direct, absorb, or transmit the light.

In some embodiments, the photonic structure is configured to deliver the light towards a target in a medium, to focus the light from the target in the medium, to collect the light from a target in a medium, to diffract light with a first wavelength towards a first direction and light with a second wavelength towards a second direction, to diffract light with a first wavelength and absorb light with a second wavelength, or a combination thereof.

In some embodiments, the magnetic structure is configured to be directionally orientable, has a non-circularly symmetric shape, has a triangular shape, includes a solid structure made of a magnetic material, includes an engineered structure of a magnetic material, the engineered structure configured to transmit the light from the photonic structure, includes cobalt, nickel, iron, iron-oxide, an alloy comprising at least one magnetic material, or a combination thereof.

In some embodiments, the supporting material includes at least one of a polymer material, a dielectric material, a semiconducting material, a non-magnetic metal, or a photoresist material.

In some embodiments, the particle has a disc shape with a diameter at an order of ones to tens of micrometers.

In some embodiments, the photonic structure is formed on top of the supporting material.

In some embodiments, the magnetic structure is below the photonic structure and embedded in the supporting material.

In some embodiments, the magnetic structure is on a bottom of the supporting material.

In some embodiments, the supporting material includes a top surface and a bottom surface along a direction. The photonic structure can be formed on the top surface of the supporting material, and the magnetic structure can be embedded in the supporting material

In some embodiments, a thickness of the supporting material from the top surface to the bottom surface along the direction is in an order of micrometers.

In some embodiments, the magnetic structure has an upper edge and lower edge, and has a thickness from the upper edge to the lower edge along the direction in an order of tens of nanometers.

In some embodiments, a distance from the top surface to the upper edge of the magnetic structure is substantially identical to a distance from the lower edge of the magnetic structure to the bottom surface.

In some embodiments, a distance from the top surface to the upper edge of the magnetic structure is larger than a distance from the lower edge of the magnetic structure to the bottom surface.

In some embodiments, the upper edge and lower edge of the magnetic structure each have a substantially isosceles triangular shape in a plane perpendicular to the direction. A width and a height of the triangular shape can be at an order of tens of micrometers.

In some embodiments, an outer surface of the particle includes one or more functional chemical or biological groups.

Another aspect of the present disclosure features a particle including: a supporting material; a photonic structure configured to manipulate an electromagnetic signal; and a magnetic structure controllable to make the particle move, where the photonic structure and the magnetic structure are supported by the supporting material.

In some embodiments, the electromagnetic signal includes at least one of ultraviolet light, visible light, infrared light, a radio-frequency (RF) signal, a microwave signal, or an acoustic signal.

In some embodiments, the supporting material includes at least one of a polymer material, a dielectric material, a semiconducting material, a non-magnetic metal, or a photoresist material.

In some embodiments, the magnetic structure comprises at least one of cobalt, nickel, iron, iron-oxide, or an alloy including at least one magnetic material.

In some embodiments, the photonic structure is configured to manipulate the electromagnetic signal by diffracting, steering, reflecting, focusing, scattering, directing, absorbing, or transmitting the electromagnetic signal.

Another aspect of the present disclosure features a method of forming magneto-photonic particles including: forming multiple discrete supporters on a substrate; forming respective magnetic structures on the multiple discrete supporters; forming a respective photonic structure above each of the respective magnetic structures; and releasing the multiple discrete supporters from the substrate to form multiple magneto-photonic particles each having a photonic structure and a magnetic structure.

In some embodiments, forming the multiple discrete supporters includes: depositing a supporting material on the substrate; and patterning the supporting material according to a pattern corresponding to the multiple discrete supporters on the substrate.

In some embodiments, forming the respective magnetic structures on the multiple discrete supporters includes: depositing a magnetic layer on the multiple discrete supporters; and performing, on each discrete supporter, a lift-off of a portion of the magnetic layer. The magnetic layer can include at least one of cobalt, nickel, iron, iron-oxide, or an alloy including at least one magnetic material.

In some embodiments, the method includes forming a separation layer on top of the respective magnetic structures.

In some embodiments, the multiple discrete supporters and the separation layer include a same material.

In some embodiments, the multiple discrete supporters include a first material, and the separation layer include a second, different material.

In some embodiments, the respective magnetic structures include a magnetic material compatible with a material of the multiple discrete supporters.

In some embodiments, forming the respective photonic structure on the separation layer and above each of the respective magnetic structures includes: imprinting the separation layer with a photonic pattern on a stamp or patterning the photonic structure using e-beam lithography.

In some embodiments, forming the respective photonic structure on the separation layer and above each of the respective magnetic structures includes: depositing a metallic layer on the imprinted pattern or patterning a metallic layer using e-beam lithography; or both. The metallic layer can include a metal.

In some embodiments, releasing the multiple discrete supporters from the substrate to form the multiple magneto-photonic particles includes: dissolving the substrate to release the multiple discrete supporters.

In some embodiments, each of the magneto-photonic particles includes the particle as described in the present disclosure.

Another aspect of the present disclosure features a method of operating magneto-photonic particles including: illuminating, with an electromagnetic (EM) signal, a magneto-photonic particle in a medium; and moving the magneto-photonic particle to a vicinity of a target in the medium by controlling a magnetic structure in the magneto-photonic particle, such that a photonic structure of the magneto-photonic particle delivers the EM signal to the target.

In some embodiments, the method further includes orienting the magneto-photonic particle to direct the EM signal by the photonic structure to the target, collecting another EM signal coming from the target by the photonic structure of the magneto-photonic particle, or both.

In some embodiments, the EM signal coming from the target includes at least one of: a scattered EM signal, a reflected EM signal, or an emitted EM signal.

Another aspect of the present disclosure features a method of operating magneto-photonic particles including: moving a magneto-photonic particle to a vicinity of a target in a medium by controlling a magnetic structure in the magneto-photonic particle; and collecting an electromagnetic (EM) signal from the target by a photonic structure of the magneto-photonic particle.

Another aspect of the present disclosure features a method of operating magneto-photonic particles including: moving a magneto-photonic particle to a vicinity of a target in a medium by controlling a magnetic structure in the magneto-photonic particle; and illuminating, with an electromagnetic (EM) signal, the magneto-photonic particle to deliver the EM signal by a photonic structure of the magneto-photonic particle to the target.

In some embodiments, moving the magneto-photonic particle to the vicinity of the target in the medium includes: translating or rotating a magnetic controller relative to the magneto-photonic particle.

In some embodiments, translating or rotating the magnetic controller relative to the magneto-photonic particle causes the magneto-photonic particle to translate or rotate relative to the magnet.

Another aspect of the present disclosure features a system including: one or more magneto-photonic particles each according to the particle as described in the present disclosure; and a magnetic controller configured to directionally move the one or more magneto-photonic particles.

In some embodiments, the system further includes: an electromagnetic (EM) source configured to illuminate an EM signal on the one or more magneto-photonic particles, an EM signal detector configured to detect an EM signal from a target in a vicinity of the one or more magneto-photonic particles, or both.

The details of one or more embodiments of the subject matter described in the present disclosure are set forth in the accompanying drawings and description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.

Like reference numbers and designations in the various drawings indicate like elements. It is also to be understood that the various example implementations shown in the figures are merely illustrative representations and are not necessarily drawn to scale.

DETAILED DESCRIPTION

Implementations of the present disclosure provide controllable magneto-photonic particles, e.g., for light collection and/or delivery where the particles can be remotely actuated with a magnetic field. The magneto-photonic particles can include an optically active surface with a magnetic core. Integrating a photonic structure on the surface of a magneto-photonic particle allows for complex optical responses, and the magnetic core facilitates controlled steering and movement of the magneto-photonic particle. The design parameters of the magneto-photonic particles can be chosen to allow both optical and magnetic functionalities.

In some embodiments, e.g., as illustrated with further details inFIGS.2A-2B, the photonic structure of the magneto-photonic particle can be configured for light manipulation, e.g., optical functionalities such as diffraction, scattering, reflection, absorption, transmission, and wavelength dependence of those functionalities. The photonic structure can include subwavelength features to provide control of direction of scattering properties, e.g., by controlling the surface refractive index variation.

In some embodiments, e.g., as illustrated with further details inFIGS.3and4, the magnetic structure in the magneto-photonic particle can be configured to be directionally orientable. For example, the magnetic structure can have a non-circularly symmetric shape, e.g., a triangle shape. In such a way, the magnetic structure can facilitate controlled steering and movement of the magneto-photonic particle, e.g., by a magnetic field. Further, the controllable orientation of the magneto-photonic particle enables directional control of light manipulated by the photonic structure, e.g., as illustrated with further details inFIGS.6A-6C.

The photonic surface that provides sophisticated control of direction of scattering properties can be patterned onto the particle using nanoimprint lithography, e.g., as illustrated with further details inFIG.5, which enables the production of complex features at nanoscale resolution, while being highly scalable. A surface photonic pattern of the photonic structure can be optimized or configured depending on its application.

Once the orientation of the pattern of a photonic surface of the photonic structure and direction of magnetization of the magnetic structure are synchronized, the position of a target spot of light delivery and/or collection can be controlled with an external magnetic field. Moreover, as the photonic structure is on a surface of the magneto-photonic structure, the surface of the photonic structure can be functionalized with functional chemical or biological groups, which can be used to bind targeted objects (e.g., molecules, cells, or tissues) for enhanced performance (e.g., stronger capability for light delivery and collection).

The combination of the photonic structure and the magnetic structure in a small size particle can result in an implantable and embeddable particle whose position and orientation can be externally controlled to deliver and collect light to a target (e.g., a molecule) in a medium, e.g., as illustrated with further details inFIG.1.

The implementations described herein can provide various technical benefits and advantages. For example, the techniques enable magneto-photonic particles to deliver and/or collect light of desired properties (e.g., wavelength, intensity, polarization, etc.) to/from any target spot in a medium. The magneto-photonic particles can exhibit high directionality and significant selectivity for desired light properties, can be adaptively controlled with a non-invasive mechanism, and do not require direct line-of-sight access to the target spot. For example, the ability to translate and rotate a magneto-photonic particle within the medium i) facilitates light encountering the magneto-photonic particle when it would otherwise be difficult, e.g., the light source is fixed, and ii) enables light delivery and/or collection to a target when it would otherwise be difficult, e.g., when the target is fixed.

The techniques can provide a suitable platform that enables targeted delivery of light within relevant biological windows, with possible applications across biology and biomedicine fields, e.g., from opto-genetics, bio-electronics, neural stimulation and imaging to drug delivery and thermotherapy (such as non-invasive localized heating). For example, a magnet can externally control the particles when the particles are embedded within a medium (e.g., a biological or biomedical medium). The magneto-photonic particles can be used to send infrared light or localized heat to a tissue (e.g., for thermotherapy) or detect molecules, cells, or tissues (e.g., for sensing, neural stimulation). Also, the magneto-photonic particles can be used to improve imaging of biomaterials by increasing electromagnetic field strength and/or collecting light in a localized area (e.g., near-field imaging). Near-field imaging can be compromised when a camera is located external to the medium and outside of the diffraction limit for the object to be imaged. The magneto-photonic particles can enable imaging an object in the near field, e.g., the magneto-photonic particles and the object are within a few wavelengths of the light of each other.

Further, the magneto-photonic particles can be scalable in size, which can depend on applications, light wavelengths, particle materials, and/or targets. The size can be in a range, e.g., from 1 μm to 1 mm such as 10 μm to 100 μm or 50 μm to 100 μm. Compared to nanoparticles that operate via Rayleigh scattering, the size of the magneto-photonic particles allows for more control of the direction of light steering. The techniques enable large-volume and cost-effective fabrications of the magnetic-photonic particles, e.g., by nanoimprinting and semiconductor fabrication technologies. As different components (e.g., photonic structure and magnetic structure) in the magneto-photonic particles can be independent from each other to implement respective functionalities, different suitable combinations of materials can be chosen. The techniques can be applied to various types of signals, such as light (e.g., infrared light or visible light), other electromagnetic signals (e.g., radio-frequency signals, micro-wave signals), or acoustic signals (e.g., ultrasound signals). For example, photonic structures can be configured to have electromagnetic (EM) functionality at longer wavelengths than infrared light, e.g., radio-frequency signals or microwave signals, in which there may be biological transparency windows for biological or biomedical applications. For illustration purpose, light is used as an example of the EM signal in the present disclosure.

Example Systems

FIG.1is a schematic diagram of an example system100using magneto-photonic particles. As illustrated inFIG.1, the system100can include magneto-photonic particles102and a magnetic source106. In some examples, the system100further includes at least one of a light source104or a light detector108. The system100can be configured to control the magneto-photonic particles102to deliver light to and/or collect light from one or more targets112(e.g., molecules, cells, or tissues) in a medium110(e.g., a biological or biomedical medium).

The light source104is configured to provide light to illuminate the magneto-photonic particles102. The light source104can include a laser, a light emitting diode (LED), or any suitable light source. In some examples, the light is an infrared light, e.g., with a wavelength in range from 780 nm to 1.4 μm or beyond. In some examples, the light is a visible light, e.g., with a wavelength in a range from 400 nm to 700 nm. In some examples, the light is an ultra-violet (UV) light, e.g., with a wavelength less than 400 nm. The light source104can be located externally relative to the medium110, e.g., movable or fixable in location.

In some embodiments, a magneto-photonic particle102includes a magnetic structure. The magnetic structure can be embedded in the magneto-photonic particle102as a magnetic core. The magnetic source106can cause the magneto-photonic particles102to rotate, translate, or both. The magnetic source106can be a magnet, an electrical coil, or any suitable source that can generate a magnetic field. The magnetic source106generates a magnetic field105, which interacts with the magnetic structure of the magneto-photonic particles102. As an example, rotating the magnetic source106about the X axis can alter the orientation of the magnetic field105and cause the magneto-photonic particles102to rotate, thus changing their orientation, e.g., as illustrated with further details inFIG.6C. As another example, the magnetic source106can be translated to a targeted spot along the Y axis or Z axis, e.g., as illustrated with further details inFIG.4, increasing the strength of the magnetic field105experienced by the magneto-photonic particles102. The magnetic source106can be externally located relative to the medium110. In some embodiments, the magnetic source106is located within the medium110and an external magnetic controller is configured to control the magnetic source106to move.

In some embodiments, the magneto-photonic particle102includes a photonic structure120. The photonic structure120can be formed on a surface of the magneto-photonic particle102and be configured for any suitable light manipulation, e.g., optical functionalities such as diffraction, scattering, reflection, absorption, transmission, and wavelength dependence of those functionalities. For example, the photonic structure120can include a photonic material that can include a dielectric material, e.g., having a dielectric constant k greater than one, a high refractive index material, e.g., having a refractive index great than 1.5, a non-magnetic material, or a combination thereof.

A surface photonic pattern of the photonic structure120can be optimized or configured depending on a particular application. Examples of the photonic structure120include, but are not limited to, diffraction gratings (e.g., transmissive or reflective), metastructures such as metagratings, and reflective mirrors. The photonic structure120can have wavelength dependence. For example, the spacing characterizing the photonic structure for infrared applications can be larger than the spacing for visible or ultraviolet applications. The photonic structure can include one-dimensional (1D) structure, two-dimensional (2D) structure, and/or three-dimensional (3D) structures. In some examples, e.g., as illustrated with further details inFIGS.2A-2B, the photonic structure120can be configured to deliver light, to collect light, or to deliver and collect light. The photonic structure can be configured to act as or be a microlens or a focusing mirror to focus light to the target112or from the target112.

As an example, as shown inFIG.1, the photonic structure120of the magneto-photonic particle102is configured to deliver (e.g., steer) light to the target112, e.g., by reflectively diffracting, steering, or reflecting light incident on the magneto-photonic particles102. The steered light by the magneto-photonic particles102can be focused onto the target112. Light from the target112, e.g., scattered light, reflected light, or emitted light, can be collected or detected by the light detector108. The inlet inFIG.1shows a close-up of an example magneto-photonic particle102. The surface of the magneto-photonic particles102includes a 2D metagrating, e.g., a geometric pattern that creates varying index of refraction. The 2D metagrating can be configured to directionally steer the incident light.

As an example,FIG.1depicts light delivery, e.g., the magneto-photonic particles102redirect incident laser light from the light source104to the target112. However, other methods involving the magneto-photonic particles102are possible. For example, a target112can emit light, e.g., under an excited light or without external excitation. The emitted light can be fluorescent light or luminescent light. The magneto-photonic particles102can be oriented and located to collect the emitted light, receive, and/or focus the emitted light at the target112.

In some embodiments, the system100is configured to control a magneto-photonic particle102to collect light, deliver light, or both. In some embodiments, the system100is configured to control multiple magneto-photonic particles102acting as an ensemble to collectively collect light, deliver light, or both.

In some embodiments, as the photonic structure is on a surface of the magneto-photonic particle102, the surface of the photonic structure can be functionalized (e.g., chemically or biologically) with functional groups (e.g., biological or chemical groups), which can be used to bind targeted objects (e.g., molecules, cells, or tissues) for enhanced performance (e.g., stronger light intensity for delivery and collection). For example, the magneto-photonic particles102can be chemically functionalized with functional groups to reduce a distance between the target112and the photonic structure120, which can enhance light intensity and/or image quality of the target112.

In some embodiments, the magneto-photonic particle102includes a supporting material122(as shown in the inlet ofFIG.1) that is configured to support the photonic structure120and the magnetic structure. The supporting material122can include any suitable material, e.g., polymer, dielectric, semiconducting, non-magnetic metal, or photoresist material. Photoresist material can be a positive or a negative photoresist for photo-lithography. The supporting material122can be configured to form the photonic structure120on a surface of the supporting material122, e.g., as described with further details inFIG.5. In some examples, the supporting material122is SU-8.

The photonic structure120can be formed on a surface of the supporting material122. The magnetic structure can be formed within the supporting material122, e.g., at a center of the supporting material122.

Example Photonic Structures

FIG.2Aillustrates various examples of magneto-photonic particles for light delivery and collection with corresponding photonic structures.

For example, diagram (a) ofFIG.2Ashows a magneto-photonic particle200aconfigured for light delivery, which includes a supporting material202a(e.g., the supporting material122ofFIG.1), a magnetic structure206a, and a photonic structure204a(e.g., the photonic structure120ofFIG.1). Incident light201acan encounter the photonic structure204a, which can be configured to redirect (e.g., diffract, scatter, or reflect) the incident light towards a target210ain a medium as redirected light203.

The incident light201acan be from a light source (e.g., the light source104ofFIG.1) that can be a laser or different light source. The light source can be external to the medium that contains the magneto-photonic particle200aand target210. Both the location and orientation of the magneto-photonic particle200arelative to the light source of the incident light201acan be controlled such that the photonic structure204adelivers light to the target210a. Additionally, the characteristics of the photonic structure204acan be selected to redirect incident light201atoward the target210a. Further, the location and orientation of the photonic structure204acan be controlled to redirect the incident light201atoward the target210a, e.g., by controlling the magnetic structure in the magneto-photonic particle200aas discussed herein. In some embodiments, the photonic structure204acan be designed using one or more wavelengths of the incident light201a, e.g., as illustrated with further details inFIG.2B.

Diagram (b) ofFIG.2Ashows another example magneto-photonic particle200bfor light delivery. The magneto-photonic particle200bcan be configured to function as a focusing reflector (e.g., mirror). The magneto-photonic particle200bcan include a supporting material202b(e.g., the supporting material122ofFIG.1), a magnetic structure206b, and a photonic structure204b(e.g., the photonic structure120ofFIG.1). Light201billuminates the photonic structure204b, and the photonic structure204bcan be configured to focus substantially parallel light201bat a particular distance, e.g., a distance to the target210b, away from the photonic structure204b, and the focused light203bcan be incident on the target210b.

Diagram (c) ofFIG.2Ashows another example magneto-photonic particle200cconfigured for light collection. The magneto-photonic particle200ccan include a support material202c(e.g., the supporting material122ofFIG.1), a magnetic structure206c, and a photonic structure204c. A target210ccan emit light, e.g., luminescent or fluorescent light, reflect light, or scatter light. Light201cfrom the target210ccan encounter the photonic structure204cthat can be configured to redirect (e.g., diffract, scatter, or reflect) the emitted light201cin a particular direction as redirected light203c, e.g., away from the magneto-photonic particle200cand towards a light detector (e.g., the light detector108ofFIG.1).

Diagram (d) ofFIG.2Ashows another example magneto-photonic particle200dconfigured for light collection. The magneto-photonic particle200dcan include a supporting material202d(e.g., the supporting material122ofFIG.1), a magnetic structure206d, and a photonic structure204d. A target210dto be detected or imaged can emit, reflect, or scatter light towards the photonic structure204d. The photonic structure204dcan be configured to redirect (e.g., diffract or reflect) the light201dfrom the target210dat a distance away from the magneto-photonic particle200d, e.g., towards a light detector (e.g., the light detector108ofFIG.1). Redirected light203dcan be parallel and can then be focused onto the light detector.

Diagram (e) ofFIG.2Ashows another example magneto-photonic particle200econfigured to both direct and collect light, which includes a supporting material202e(e.g., the supporting material122ofFIG.1), a magnetic structure206e, and a photonic structure204e. In this example, incident light201e1, e.g., light from a laser, can encounter the photonic structure204e. The photonic structure204ecan be configured to redirect the incident light201e1as redirected light203e1toward a target210e. In response to receiving the redirected light203e1, the target210ecan reflect, scatter, or absorb and then emit light. Light201e2from the target210ecan encounter the photonic structure204eagain that can be configured to redirect the light201e2as redirected light203e2along a particular direction.

In some embodiments, the photonic structure204ecan have wavelength dependent properties. For example, incident light201e1can have a first wavelength λ1, and light201e2can have a second wavelength λ2. The photonic structure204ecan be configured to direct light of first wavelength λ1towards the target201eand light of the second wavelength λ2towards a light detector such as a camera.

FIG.2Billustrates examples of magneto-photonic particles for light manipulation with corresponding wavelength dependent photonic structures. For example, diagram (a) ofFIG.2Bshows an example magneto-photonic particle250aconfigured to deflect, e.g., diffract, light at different angles depending on the wavelengths. The magneto-photonic particle250acan include a supporting material252a, a magnetic structure256a, and a photonic structure254a. The photonic structure254acan be configured to direct incident light251a1of a first wavelength λ1along a first direction and incident light251a2of the second wavelength λ2along a second direction. Consequently, redirected light253aland253a2can propagate in the first and second directions, respectively.

Diagram (b) ofFIG.2Bshows another example magneto-photonic particle250bconfigured to deflect light of a first wavelength λ1and absorb light of a second wavelength λ2. The magneto-photonic particle250bcan include a supporting material252b, a magnetic structure256b, and a photonic structure254b. Incident light251b1of the first wavelength λ1can encounter the photonic structure254band be deflected as redirected light253b. Incident light251b2of the second wavelength λ2can encounter the photonic structure254band be absorbed by the magneto-photonic particle250b.

Diagram (c) ofFIG.2Bshows another example magneto-photonic particle250cconfigured to deflect light of a first wavelength λ1and transmit light of a second wavelength λ2. The magneto-photonic particle250ccan include a supporting material252c, a magnetic structure256c, and a photonic structure254c. Incident light251c1of the first wavelength λ1can encounter the photonic structure254cand be deflected as redirected light253c. Incident light251c2of the second wavelength λ2can encounter the photonic structure254cand be transmitted through the magneto-photonic particle as transmitted light255.

In some embodiments, the material choices of the photonic structure254c, supporting material252c, and magnetic structure256ccan be chosen to transmit light within a particular frequency range. The shape of the magnetic structure256ccan be chosen to allow transmission of light within the particular frequency range. For example, instead of the solid core, the magnetic structure256ccan be engineered to include microstructures or one or more thin layers (nanoscale slivers), arranged throughout the supporting material252cto allow transmission of light within the particular frequency range.

Although the magneto-photonic particles illustrated inFIGS.2A-2Bcan have different photonic structures for different applications, the magnetic structures in the magneto-photonic particles can be same or similar, and be configured to be directionally controllable, e.g., as discussed with further details below.

Example Magnetic Structures

FIG.3illustrates an example magnetic structure304in a particle300. The particle300can be an example of the magneto-photonic particle102ofFIG.1before a photonic structure is formed on the top surface. The particle300can be a circular disk, e.g., have a circular outline when viewed from above as in the “top view” ofFIG.3. A magnetic structure304can be embedded within a supporting material302, e.g., the surface of the particle300does not include a portion corresponding to the magnetic structure304. In general, the shape of magnetic structure204can lack a circular symmetry, such that it can be oriented along a preferred direction by a magnetic field, e.g., be directionally orientable.

In this example, the particle300has a first width w1corresponding to the diameter of the particle300. The first width w1of the particle300can be in a suitable range, e.g., 1 to 100 μm such as 50 to 100 μm. In some examples, the magnetic structure304can be a triangular prism, e.g., have a triangular outline cross section when viewed from the “top view.” The triangular outline can correspond to an isosceles triangle, the triangle having a width w2and a height h1. The width w2can be smaller than the first width w1, e.g., 40 μm. The height h1can be smaller than the first width w1of the particle300, e.g., 70 μm. The main constraint is that the size of the magnetic structure be no larger than that of the overall structure of the particle300.

A “side view,” e.g., a cross-section of the particle300, can reveal a rectangular shape of both the particle300and the magnetic structure304. The magnetic structure304can be embedded within the supporting material302(e.g., in a center of the supporting material302), such that the top and bottom of the magnetic structure304do not reach the top 306 and/or bottom308of the particle300. In some examples, a height h2of the supporting material302below the magnetic structure304can be in a suitable range, e.g., 100 nm to 1 μm such as 500 nm. A height h3of the magnetic structure304can be in a suitable range, e.g., 10 nm to 100 nm such as 50 nm. The height h4of the supporting material302above the magnetic structure304can be identical to or larger than the height h2of the supporting material302below the magnetic structure304. In some embodiments, the heights of the supporting material302above and below the magnetic structure304being substantially the same can facilitate a uniform control of the orientation of the particle300. For example, the height h4can be in a suitable range, e.g., hundreds of nm to several μm, such as 1 μm.

The supporting material302can be transparent, such that the magnetic structure304is visible from a top and bottom view of the particle300before a photonic structure is formed on either side.

In some embodiments, the magnetic structure304does makeup a portion of the bottom308of the particle300, e.g., the height h2between the bottom308of the magneto-photonic particle300and the bottom of the magnetic structure304is zero.

FIG.4shows example controllable movements of a particle402with a non-symmetric magnetic structure403. The particle402can be an example of the magneto-photonic particle102ofFIG.1or the particle300ofFIG.3. A magnetic source406(e.g., the magnetic source106ofFIG.1) can generate a magnetic field401that the particle402experiences. For example, the magnetic field401can extend through the particle402, causing the particle402to translate in space relative to the magnetic source406and change orientation, due to the magnetic structure403lacking circular symmetry. The magnetic source406can be an external magnet.

The effect of the magnetic field on the particle402can differ based on the distance between the magnetic source406and the particle402. For example, when the magnet source406is far enough away from the particle402(e.g., greater than 10 cm such as 20 cm), the magnetic source406can primarily cause rotation of the particle402. This distance can depend on the strength of the magnet source406. Scenes411,413, and415depict the particles402changing their orientation in response to the magnetic source406moving, e.g., rotating or moving relative to the particles402. In some examples, the magnetic source406can be moved along a circular path to induce rotation of a particle402. The circular path can be approximately concentric with the position of the particle402.

In scene411, the magnetic source406has a first orientation405, e.g., “up.” This first orientation405causes the magnetic source406to generate a magnetic field, which causes the triangular magnetic structure403to point along the direction of the first orientation405.

In scene413, the orientation of the magnetic source406changes to a second orientation407, e.g., “left.” The second orientation407causes the magnetic source406to generate a magnetic field, which causes the triangular magnetic structure403to point along the direction of the second orientation407.

In scene415, the orientation of the magnetic source changes to a third orientation409, e.g., “right.” The third orientation409causes the magnetic source406to generate a magnetic field, which causes the triangular magnetic structure403to point along the direction of the third orientation409.

Because the magnetic source406primarily affects the orientation of the particles402in the far field limit, the location in space of the particles402does not notably change when the orientation of the magnetic source406does. Because this particular particle402has a disk shape, e.g., a cylinder, it can rotate about an axis through the center of the cylinder without changing its location relative to the magnetic source406.

As another example, when the magnetic source406is close enough to the particle (e.g., less than 10 cm), the magnetic source406can primarily cause translation of the particle402. This distance can depend on the strength of the magnetic source406. Scenes410,420,422, and426depict a series of translations of the particle402in response to the magnetic source406moving. In some examples, the magnetic source406is moved along a same line designed for the particle402to move. The magnetic source406can be translated, without rotation.

Scene410depicts a particle402, a target, and a series of three steps to arrive at the target. The particle402starts at a first position412. The location and orientation of the magnetic source406cause the magnetic source406to generate a magnetic field that causes the particle402to translate along a first path414. Along the first path414, the orientation of the magnetic structure403does not notably change, e.g., the triangular outline of the magnetic structure403remains pointing down.

In some examples, e.g., as shown in scenes420,422,426below, the particle402is both oriented and translated to be guided to reach a desired position at an end of a second path. The triangular core of the magnetic structure403can be aligned with the direction of the translation.

Scene420depicts the particle402after it has translated to a second position416by moving along the first path414. Moving the magnetic source406, e.g., translating, rotating, or both relative to the particle402can cause translation along a second path418.

Scene422depicts the particle402after it has translated to a third position425. The orientation of the particle402changes between scenes420and422. Moving the magnetic source406, e.g., translating, rotating, or both, relative to the particle402can cause translation along a third path424.

Scene426depicts the particle402having arrived at the target location428by moving along the third path424. Once again, the orientation of the particle402can change between scenes426and422.

Example Fabrication Process

FIG.5shows an example process500of fabricating magneto-photonic particles501. The magneto-photonic particles501can be the particles102ofFIG.1,200a-200eofFIG.2A,254a-254cofFIG.2B,300ofFIG.3, or402ofFIG.4. In general, atomic layer deposition (ALD), nano-imprinting, lithography methods and systems, or any other suitable methods and systems can be used to perform the process500.

The process500can start with providing a substrate502. The substrate502can be, for example, a silicon wafer. A first polymer504can be deposited onto the substrate502. In some embodiments, the first polymer504is spin coated to provide a uniform coating on top of the substrate502. In some embodiments, the first polymer504is an epoxy-based, negative photoresist, such as SU-8.

The first polymer504can be patterned to form multiple discrete supporters506on the substrate502. For example, the pattern can correspond to evenly-spaced circular disks, such that the portion of the first polymer504not corresponding to the circular disks is removed from the substrate502. In some examples, a supporter506includes cross-linked SU-8. For example, SU-8 film can be prepared as the first polymer504on the substrate by spin coating and pre-annealing process. Then, the SU-8 film can be exposed region-selectively by ultraviolet (UV) light using photolithography, which can create radicals in exposed regions. Then, post-annealing process can make the radicals active and create the SU-8 cross-linked.

For each supporter506, a respective magnetic structure508can be formed on the surface of the discrete supporters506. In some embodiments, the magnetic structure508is formed by a metal lift-off method. In some embodiments, the magnetic structure508is cobalt. The material choice of the magnetic structure508can allow for the magnetic structure508to be controllable by a magnetic field while remaining in place while other layers dissolve during fabrication, e.g., compatible with the material of the supporters506.

The substrate502with the supporters506on top can receive a second polymer510, which can completely cover the supporters506. The second polymer510can include a supporting material, e.g., the material that supports the magnetic structure508and holds it in place relative to the first polymer504layer. The second polymer510can be made of the same material of the first polymer504, e.g., SU-8.

The second polymer510can form a separation layer on top of the magnetic structures508, e.g., a portion of the second polymer510can later be dissolved to release the magneto-photonic particles501.

In some embodiments, the second polymer510is an uncured, epoxy-based photoresist, such as uncured SU-8. In some embodiments, the first polymer504, the second polymer510, or both are transparent, such that the supporters506with their respective magnetic structures508are visible when viewed from above. In some embodiments, the first polymer504, the second polymer510, or both are a nonmagnetic material.

Because the second polymer510is uncured, the second polymer510can be nano-imprinted with a stamp514to form a photonic structure516on the surface of the second polymer510. The stamp514can have preconfigured microstructure and/or nanostructures. In some embodiments, the photonic structure516is formed using e-beam lithography. The photonic structure516can include micro- and/or nanoscale photonic features. The photonic structure516can be the photonic structure120ofFIG.1, any one of204a-204eofFIG.2A, or any one of250a-250cofFIG.2B.

The second polymer510can be patterned such that the discrete circular disks, e.g., the supporters506, remain on the substrate502. The pattern used to pattern the first polymer504can be the same as that used to pattern the second polymer510. As a result of the patterning, each supporter506has a photonic structure512, which corresponds to a portion of the photonic structure516.

The supporters506can be released from the substrate502to form multiple magneto-photonic particles501, each having a photonic structure512and a magnetic structure508. In some limitations, releasing the supporters506from the substrate502can include a sacrificial layer dissolution, e.g., dissolving at least part or all of the substrate502.

Optionally, before releasing the supporters506from the substrate502, a layer of metal520can be deposited onto the supporters506and substrate502. As a result, the magneto-photonic particles501have a metallic coating on top of the photonic structure512. A metallic coating can be beneficial, because, although the photonic structure512might have a desirable morphology, it might not be highly efficient in reflecting light. For example, the contrast in the refractive indices between air and SU-8 is less than the contrast in refractive indices between air and metal, which can lead to a low reflection coefficient of the photonic structure512. In some embodiments, a silicon nitride/silicon dioxide (Si3N4/SiO2) dielectric material can be used in place of metal as a coating for the photonic structure512.

Example Applications

FIG.6Ashows an example fabricated magneto-photonic particle600(e.g., the magneto-photonic particle501fabricated by the process500ofFIG.5). A front view602shows the top of the magneto-photonic particle600, e.g., the photonic surface with a metal coating. A back view604shows the bottom of the magneto-photonic particle600. Because the supporting material between the magnetic coating and the bottom of the magneto-photonic particle600is transparent, the triangular magnetic structure is visible in the back view604. The magneto-photonic particles600can be, for example, the magneto-photonic particles102ofFIG.1,200a-200eofFIG.2A,254a-254cofFIG.2B,300ofFIG.3, or402ofFIG.4.

FIG.6Bshows an example system621for controlling the magneto-photonic particle600ofFIG.6A. The system621can be similar to, or the same as, the system100ofFIG.1. The system621can include a light source606, a hemispherical dome610filled with the medium628such as water, a platform612that supports the hemispherical dome610, and magneto-photonic particles600immersed in the medium628. In this example, the magneto-photonic particles600can be configured to diffract light of a particular wavelength, e.g., 635 nm. The light source606can shine a laser beam608into an opening of the hemispherical dome610at a particular polar coordinate614, e.g., 0° as depicted inFIG.6B.

Depending on the orientation of the magneto-photonic particles600, e.g., the direction in which the triangular magnetic structure points (measured by the azimuthal coordinate616), the diffraction pattern (e.g., diffracted light at a series of diffraction orders) seen in the top view618can differ its orientation.

FIG.6Cshows results of controlling light steering directions of the magneto-photonic particle600ofFIG.6Aby controlling orientations of the magneto-photonic particle600. The magnetic source can move, e.g., translate or rotate relative to the magneto-photonic particle600, to cause the orientation of the magneto-photonic particle600to change, as discussed in relation toFIG.4. The hemispherical dome610can be translucent, such that light diffracted by the magneto-photonic particles600within the medium628can illuminate the hemispherical dome610.

In the first scene601, the orientation622of the magneto-photonic particle600is slightly tilted to the right, and the resulting diffraction pattern620is also slightly tilted to the right. In the second scene603, the orientation626of the magneto-photonic particle600is upright, and the resulting diffraction pattern624is also upright. In the third scene605, the orientation630of the magneto-photonic particle600slightly tilted to the left, and the resulting diffraction pattern632is also slightly tilted to the left. Accordingly, the direction of light delivery can be controlled by orienting magneto-photonic particle600.

Example Processes

FIG.7is a flowchart of an example process700for forming magneto-photonic particles. The magneto-photonic particles can be any of the magneto-photonic particles102,200a-200e,250a-250c,300,402,501, and600, as discussed in the present disclosure. The process700can be similar to, or the same as, the process500ofFIG.5.

A deposition system can form multiple discrete supporters on a substrate (702). In some embodiments, forming the multiple discrete supporters (e.g., the supporters506ofFIG.5) includes depositing a polymer (e.g., the first polymer504ofFIG.5) on the substrate and patterning the polymer according to a pattern corresponding to the multiple discrete supporters, e.g., multiple circular disks.

The deposition system can form respective magnetic structures on the multiple discrete supporters (704). In some embodiments, forming the respective magnetic structures (e.g., the magnetic structures508ofFIG.5) on the multiple discrete supporters includes depositing a magnetic material (e.g., a magnetic metal such as cobalt) on the plurality of discrete supporters; and performing, on each discrete supporter, a lift-off of a portion of the magnetic material.

In some embodiments, the respective magnetic structures include a magnetic material that is compatible with a material of the multiple discrete supporters.

The deposition system can form a respective photonic structure above each of the respective magnetic structures (706). In some embodiments, forming the respective photonic structure (e.g., the photonic structure516ofFIG.5) above each of the respective magnetic structures includes: imprinting a separation layer (e.g., the second polymer510ofFIG.5) with a photonic pattern on a stamp (e.g., stamp514ofFIG.5); depositing a metal layer on the imprinted pattern; or both.

The deposition system can release the multiple discrete supporters from the substrate to form multiple magneto-photonic particles each having a photonic structure and a magnetic structure (708). In some embodiments, releasing the multiple discrete supporters from the substrate to form the multiple magneto-photonic particles includes dissolving the substrate to release the multiple discrete supporters.

In some embodiments, the process700can include one or more additional steps, fewer steps, or some of the steps can be divided into multiple steps. As an example, the process700can include forming a separation layer on top of the respective magnetic structures. As another example, after step704, a deposition system can deposit a layer of a polymer, portions of which can later be dissolved as a sacrificial layer.

In some embodiments, the multiple discrete supporters and the separation layer include the same material, e.g., an epoxy-based, negative photoresist such as SU-8. In some embodiments, the multiple discrete supporters and the separation layer include different materials.

FIG.8Ais a flow chart of an example process800for operating magneto-photonic particles for delivering light. The process800can be performed by a system, e.g., the system100ofFIG.1or the system621ofFIG.6B. The magneto-photonic particles can be any of the magneto-photonic particles102,200a,200b,200e,250a-250c,300,402,501, and600.

The system can illuminate, with light, a magneto-photonic particle in a medium (802). In some embodiments, one or more magneto-photonic particles can be immersed in the medium. The medium can include a biological or biomedical medium.

The system can move the magneto-photonic particle to a vicinity of a target in the medium by controlling a magnetic structure in the magneto-photonic particle, such that a photonic structure of the magneto-photonic particle delivers the light to the target (804). The target can include a biological or biomedical object such as a molecule, a cell, or a tissue.

In some embodiments, the process800can include one or more additional steps, fewer steps, or some of the steps can be divided into multiple steps. For example, the process800can include orienting the magneto-photonic particle to direct the light by the photonic structure to the target.

In some limitations, the process800includes collecting light coming from the target by the photonic structure of the magneto-photonic particle. The light coming from the target can include at least one of: scattered light, reflected light, or emitted light, e.g., the target can be a fluorescent molecule.

FIG.8Bis a flow chart of another example process830for operating magneto-photonic particles for delivering light. The process830can be performed by a system, e.g., the system100ofFIG.1or the system621ofFIG.6B. The magneto-photonic particles can be any of the magneto-photonic particles102,200a,200b,200e,250a-250c,300,402,501, and600. Different from the process800ofFIG.8A, the process830can be performed by first moving the magneto-photonic particles before illuminating light.

The system can first move a magneto-photonic particle to a vicinity of a target in a medium by controlling a magnetic structure in the magneto-photonic particle (832). In some embodiments, moving the magneto-photonic particle to the vicinity of the target in a medium can include translating or rotating a magnetic controller relative to the magneto-photonic particle. In some embodiments, translating or rotating the magnetic controller relative to the magneto-photonic particle causes the magneto-photonic particle to translate or rotate relative to the magnet.

After the magneto-photonic particle is moved to the vicinity of the target in the medium, the system can illuminate, with light, the magneto-photonic particle to deliver the light by a photonic structure of the magneto-photonic particle to the target (834).

FIG.8Cis a flow chart of another example process850for operating magneto-photonic particles for collecting light. The process830can be performed by a system, e.g., the system100ofFIG.1or the system621ofFIG.6B. The magneto-photonic particles can be any of the magneto-photonic particles102,200c,200d,200e,250a-250c,300,402,501, and600.

The system can move a magneto-photonic particle to a vicinity of a target in a medium by controlling a magnetic structure in the magneto-photonic particle (852). The system can then collect emitted light from the target by a photonic structure of the magneto-photonic particle (854).

The order of steps in the processes800,830, and850described above is illustrative only, and forming magneto-photonic particles can be performed in different orders. For example, the location of the target can change, and the system can repeatedly illuminate and move the magneto-photonic particle throughout the medium. Processes800,830, and850can be combined for applications involving both the collection and delivery of light via the magneto-photonic particle.

Further modifications and alternative embodiments of various aspects will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only. It is to be understood that the forms shown and described herein are to be taken as examples of embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description.