# US 7,745,788 B2 · Optical trapping with a semiconductor

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- Number: US 7,745,788 B2
- Document ID: US7745788B2
- Status: Granted
- Kind: B2
- Application number: 11/525,518
- Filed: 2006-09-22
- Published: 2007-03-29
- Granted: 2010-06-29
- Earliest claimed: 2005-09-23
- Assignees: Massachusetts Institute of Technology
- Inventors: David C. Appleyard; Matthew J. Lang
- Web page: https://patentgrep.com/patent/US7745788B2

## CPC

- G21K 1/00: Arrangements for handling particles or ionising radiation, e.g. focusing or moderating
- G21K 1/30: for confining neutral particles or handling confined neutral particles, e.g. atom traps
- G02B 21/32: Micromanipulators structurally combined with microscopes
- G21K: HANDLING OF PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A method and apparatus are disclosed for forming an optical trap with light directed through or above a semiconductor material. A preferred embodiment selected light-trapping wavelengths that have lower absorption by the semiconductor. A preferred embodiment provides for an optical trapping through semiconductor employing a thin silicon (Si) wafer as a substrate. Further embodiments of the invention provide for microchannel fabrication, force probe measurement, sorting, switching and other active manipulation and assembly using an optical trap.

## Claims

### Claim 1

A method for optically trapping an object comprising:
optically coupling an active volume comprising a semiconductor material, to a light source; and
directing light through the semiconductor material to form an optical trap in the active volume, the light applying a force to an object in the active volume.

### Claim 2 (depends on 1)

The method of claim 1, wherein the semiconductor material comprises silicon.

### Claim 3 (depends on 1)

The method of claim 1 further comprising providing a laser light source emitting at a wavelength in a range of 900 nm to 1400 nm for trapping through the semiconductor.

### Claim 4 (depends on 1)

The method of claim 1 further comprising positioning a light converging lens between an infrared light source and the active volume.

### Claim 5 (depends on 1)

The method of claim 1 further comprising providing a second lens to collect light from the active volume and an imaging device.

### Claim 6 (depends on 1)

The method of claim 1 further comprising providing a semiconductor material less than 250 micrometers in thickness for trapping through the semiconductor.

### Claim 7 (depends on 1)

The method of claim 1 further comprising providing a semiconductor material that is double-side-polished for trapping through the semiconductor.

### Claim 8 (depends on 1)

The method of claim 1, further comprising forming a plurality of optical traps simultaneously within the active volume.

### Claim 9 (depends on 1)

The method of claim 1, further comprising trapping a first object in said optical trap and trapping one or more additional microstructures from the group comprised of a nano-wire, a nano-bridge, a micro-stylus, an oligonucleotide strand, a biomolecular assemblage, a cell, a protein, a fluid and a force probe; and
fixedly attaching at least one of the said additional microstructures to said first object; and
controllably holding both the trapped first object and at least one additional microstructure by the optical trap applied to said first object.

### Claim 10 (depends on 9)

The method of claim 9, further comprising moving the optical trap to move the object and said additional microstructure into direct contact with a surface on or above the semiconductor material.

### Claim 11 (depends on 10)

The method of claim 10, further comprising fixedly attaching to said surface, by photo-polymerization, hydrophobicity or bonding agent, one of the said first object and the said additional microstructure that has been made to contact said surface.

### Claim 12 (depends on 1)

The method of claim 1, further comprising positioning a surface on or above the semiconductor material, said surface having non-homogeneous features that direct electrical or photonic signals.

### Claim 13 (depends on 1)

The method of claim 1, further comprising positioning a surface on or above the semiconductor material, said surface having non-homogeneous features that uses microfluidic flow.

### Claim 14 (depends on 11)

The method of claim 11, further comprising providing a surface on or above semiconductor material, said surface having a plurality of surface features that conduct electrical or photonic signals; and
fixedly attaching one of the said first object and the said additional microstructure to said substrate at a location of one of said surface features.

### Claim 15 (depends on 11)

The method of claim 11, further comprising positioning a surface on or above the semiconductor material, said surface having non-homogeneous features that direct microfluidic flow; and
fixedly attaching one of the object and microstructure to said substrate at a location of said non-homogeneous surface feature.

### Claim 16

A device for optically trapping an object comprising:
an active volume comprising a surface of a semiconductor material; and
a light source optically coupled to the active volume through the semiconductor material to form an optical trap of the object in the active volume.

### Claim 17 (depends on 16)

The device of claim 16 wherein the semiconductor is silicon.

### Claim 18 (depends on 16)

The device of claim 16 further comprising a laser light source emitting at a wavelength in a range of 900 nm to 1600 nm.

### Claim 19 (depends on 16)

The device of claim 16 further comprising an optical element or a light converging lens positioned between the light source and the active volume.

### Claim 20 (depends on 16)

The device of claim 16 further comprising a second lens to collect light from the active volume and an imaging device.

### Claim 21 (depends on 16)

The device of claim 16 further comprising a semiconductor material less than 250 micrometers in thickness.

### Claim 22 (depends on 16)

The device of claim 16 further comprising a semiconductor material SSP, double-side-polished or flat to form a trap.

### Claim 23 (depends on 16)

The device of claim 16, further comprising one or more additional light sources optically coupled to the volume to produce respectively one or more additional optical traps or position sensing beams simultaneously within the active volume.

### Claim 24 (depends on 16)

The device of claim 16, further comprising a light source beam that is controllably movable so as to enable the optical trap to be controllably movable.

### Claim 25 (depends on 24)

The device of claim 24, further comprising a device for fixedly attaching a trapped object to the semiconductor material by photo-polymerization, hydrophobicity or other bonding means.

### Claim 26 (depends on 16)

The device of claim 16, wherein the surface of the semiconductor material comprises non-homogeneous features designed to control electrical or photonic signals.

### Claim 27 (depends on 16)

The device of claim 16, wherein the surface of the semiconductor material comprises a non-homogeneous feature that directs microfluidic flow.

### Claim 28 (depends on 16)

The device of claim 16 further comprising a light detector coupled to the active volume.

### Claim 29 (depends on 28)

The device of claim 28 wherein the detector detects an image of one or more trapped objects.

### Claim 30 (depends on 16)

The device of claim 16 further comprising a position detector.

### Claim 31 (depends on 28)

The device of claim 28 wherein the detector detects light transmitted through the volume by a second light source.

### Claim 32 (depends on 16)

The device of claim 16 further comprising a beam steering device to steer a beam from a laser that traps an object in the volume.

### Claim 33 (depends on 16)

The device of claim 16 further comprising a beam expander to control a size of a light beam coupled to the active volume.

### Claim 34 (depends on 32)

The device of claim 32 wherein the beam steering device comprises an acousto-optic device.

### Claim 35 (depends on 16)

The device of claim 16 wherein the optical trap traps a fluid.

### Claim 36 (depends on 35)

The device of claim 35 wherein a trapped object comprises a fluid tether.

### Claim 37 (depends on 36)

The device of claim 36 wherein the tether is at least 10 μm long.

### Claim 38 (depends on 16)

The device of claim 16 further comprising a detector that detects light transmitted through the active volume.

### Claim 39 (depends on 16)

The device of claim 16 further comprising a detector that detects light reflected from the active volume.

### Claim 40 (depends on 16)

The device of claim 16 further comprising a detector that detects a trapped object attached to the surface of the semiconductor.

### Claim 41 (depends on 16)

The device of claim 16 further comprising a nanostructure to be trapped in the active volume.

### Claim 42 (depends on 16)

The device of claim 16 further comprising a second trapping volume having a second semiconductor surface.

### Claim 43 (depends on 16)

The device of claim 16 further comprising a switcher to synchronously switch a light beam to trap a plurality of objects.

### Claim 44 (depends on 16)

The device of claim 16 further comprising a holographic optical element to trap a plurality of objects.

### Claim 45 (depends on 16)

The device of claim 16 wherein the semiconductor comprises one or more optically conductive elements.

### Claim 46 (depends on 16)

The device of claim 16 wherein the semiconductor further comprises one or more electrically conductive components.

### Claim 47 (depends on 16)

The device of claim 16 further comprising focusing light from the light source onto the active volume to form the optical trap.

### Claim 48

A method of controlling motion of an object comprising optically coupling light to an active volume through a semiconductor material to control motion of an object within the active volume, the object being moveable while tethered relative to a surface of the semiconductor material.

### Claim 49 (depends on 48)

The method of claim 48 further comprising coupling the object relative to a surface of a semiconductor device.

### Claim 50 (depends on 48)

The method of claim 48 wherein the object is coupled with a fluid tether.

### Claim 51 (depends on 48)

The method of claim 48 further comprising rotating the object relative to the surface.