U.S. patent application number 11/805678 was filed with the patent office on 2008-03-20 for application of static light to a fluid flow of cnts for purposes of sorting the cnts.
Invention is credited to Herman A. Lopez, Shida Tan, Yuegang Zhang.
Application Number | 20080067111 11/805678 |
Document ID | / |
Family ID | 36124485 |
Filed Date | 2008-03-20 |
United States Patent
Application |
20080067111 |
Kind Code |
A1 |
Zhang; Yuegang ; et
al. |
March 20, 2008 |
Application of static light to a fluid flow of CNTs for purposes of
sorting the CNTs
Abstract
A method is described that comprises sorting carbon nanotubes
(CNTs) within a fluidic flow for a targeted subset of the CNTs. The
sorting comprises attracting at least a portion of the CNTs within
the fluidic flow in a direction of increasing intensity of an
electric field component of a substantially stationary beam of
light. The electric field component has a frequency that is less
than one or more resonant frequencies of the CNTs within the
portion.
Inventors: |
Zhang; Yuegang; (Cupertino,
CA) ; Lopez; Herman A.; (Sunnyvale, CA) ; Tan;
Shida; (Milpitas, CA) |
Correspondence
Address: |
Mark L. Watson;Blakely, Sokoloff, Taylor & Zafman LLP
7th Floor
12400 Wilshire Boulevard
Los Angeles
CA
90025
US
|
Family ID: |
36124485 |
Appl. No.: |
11/805678 |
Filed: |
May 23, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10956597 |
Oct 1, 2004 |
7259344 |
|
|
11805678 |
May 23, 2007 |
|
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Current U.S.
Class: |
209/129 |
Current CPC
Class: |
B07C 5/344 20130101;
Y10S 977/845 20130101; C01B 32/172 20170801; B82Y 30/00 20130101;
G01N 2030/0035 20130101; B82Y 40/00 20130101 |
Class at
Publication: |
209/129 |
International
Class: |
B03C 7/00 20060101
B03C007/00 |
Claims
1. An apparatus, comprising: a) a first fluidic flow channel to
guide a first fluidic flow; b) a second fluidic flow channel to
guide a second fluidic flow that carries carbon nanotubes (CNTs);
c) a third fluidic flow channel coupled to said first and second
fluidic flow channels, said third fluidic flow channel to guide
said first fluidic flow and said second fluid flow along side one
another; and, d) a substantially stationary lens to focus
substantially stationary light to a spot within said third fluidic
flow channel, said lens positioned to place said spot such that
said second fluidic flow flows: along or off to a side of said spot
and not along or off to another side of said spot that is opposite
of said side.
2. The apparatus of claim 1 further comprising a series of lenses
to form a plurality of beams of light that are each focused to a
spot within said third fluidic flow channel so as to form a series
of focused spots within said third fluidic flow channel.
3. The apparatus of claim 2 wherein said series of lenses are
positioned to recede said spots into said first fluidic flow.
4. The apparatus of claim 1 further comprising a fourth fluidic
flow channel coupled to said third fluidic flow channel, said
fourth fluidic flow channel to transport at least a portion of said
CNTs that were attracted into at least a portion of said first
fluidic flow because an electric field component of said light had
a frequency that was less than the one or more resonant frequencies
of those CNTs within said portion of said CNTs.
5. The apparatus of claim 4 further comprising a fifth fluidic flow
channel coupled to said third fluidic flow channel, said fifth
fluidic flow channel to transport at least a second portion of said
CNTs that were repelled toward a fluidic flow that flows through
said fifth fluidic flow channel because an electric field component
of said light had a frequency that was greater than the one or more
resonant frequencies of those CNTs within said second portion of
said CNTs.
6. The apparatus of claim 5 further comprising: a sixth fluidic
flow channel downstream from said fourth fluidic flow channel; a
lens to focus second light within said sixth fluidic flow
channel.
7. The apparatus of claim 6 wherein the frequency of the electric
field component of said second light is less than the frequency of
the electric field component of said light.
8. The apparatus of claim 6 wherein the frequency of the electric
field component of said second light is greater than the frequency
of the electric field component of said light.
9. The apparatus of claim 6 wherein the frequency of the electric
field component of said second light is less than the one or more
resonant frequencies of those CNTs within said portion of said
CNTs.
10. The apparatus of claim 6 further comprising: a seventh fluidic
flow channel downstream from said fifth fluidic flow channel; a
lens to focus third light within said seventh fluidic flow
channel.
11. The apparatus of claim 10 wherein the frequency of the electric
field component of said third light is less than the frequency of
the electric field component of said light.
12. The apparatus of claim 10 wherein the frequency of the electric
field component of said third light is greater than the frequency
of the electric field component of said light.
13. The apparatus of claim 5 further comprising: a sixth fluidic
flow channel downstream from said fifth fluidic flow channel; a
lens to focus second light within said sixth fluidic flow
channel.
14. The apparatus of claim 13 wherein the frequency of the electric
field component of said second light is less than the frequency of
the electric field component of said light.
15. The apparatus of claim 13 wherein the frequency of the electric
field component of said second light is greater than the frequency
of the electric field component of said light.
16. The apparatus of claim 13 wherein the frequency of the electric
field component of said second light is greater than the one or
more resonant frequencies of those CNTs within said portion of said
CNTs.
17. An apparatus, comprising: a) fluidic flow channels to run first
a second fluidic flows alongside one another; and, b) one or more
lenses and a laser light source arranged to create substantially
stationary focused laser light that forms a gradient of electric
field intensity within at least one of said fluid flows, said
gradient of electric field intensity and the frequency of said
laser light's electric field component to cause CNTs, as a
consequence of their one or more resonant frequencies relative to
said frequency, to leave said first fluidic flow and enter said
second fluidic flow.
18. The apparatus of claim 17 wherein said first second fluidic
flows run along different vertical planes.
19. The apparatus of claim 17 wherein said second fluid flow runs
above said first fluidic flow.
20. The apparatus of claim 17 wherein said CNTs have a resonant
frequency that is less than the frequency of the electric field
component of said laser light.
21. The apparatus of claim 20 wherein said CNTs are targeted
CNTs
22. The apparatus of claim 17 wherein said CNTs have a resonant
frequency that is greater than the frequency of the electric field
component of said laser light.
23. The apparatus of claim 22 wherein said CNTs are targeted CNTs.
Description
[0001] The present application is a divisional of U.S. application
Ser. No. 10/956,597, filed on Oct. 1, 2004, and priority is claimed
thereof.
FIELD OF INVENTION
[0002] The field of invention relates generally to carbon nanotubes
(CNTs); and, more specifically, to the application of static light
to a fluid flow of CNTs for purposes of sorting the CNTs.
BACKGROUND
[0003] Carbon nanotubes (CNTs) can be viewed as a sheet of Carbon
that has been rolled into the shape of a tube (end capped or
non-end capped). CNTs having certain properties (e.g., a
"conductive" CNT having electronic properties akin to a metal) may
be appropriate for certain applications while CNTs having certain
other properties (e.g., a "semiconducting" CNT having electronic
properties akin to a semiconductor) may be appropriate for certain
other applications. CNT properties tend to be a function of the
CNT's "chirality" and diameter. The chirality of a CNT
characterizes its arrangement of carbon atoms (e.g., arm chair,
zigzag, helical/chiral). The diameter of a CNT is the span across a
cross section of the tube.
[0004] Because the properties of a CNT can be a function of the
CNT's chirality and diameter, the suitably of a particular CNT for
a particular application is apt to depend on the chirality and
diameter of the CNT. Unfortunately, current CNT manufacturing
processes are only capable of manufacturing batches of CNTs whose
tube diameters and chiralities are widely varied. The problem
therefore arises of not being able to collect CNTs (e.g., for a
particular application) whose diameter and chiralities reside only
within a narrow range (or ranges of) those that have been
manufactured.
[0005] United States Patent Application Publication US 2004/0120880
by Zhang, Hannah and Woo (hereinafter "Zhang et al.") and entitled
"Sorting of Single-Walled Carbon Nanotubes Using Optical Dipole
Traps" teaches that CNTs of specific chirality and diameter will
posses electrical dipole moments that will cause the CNT to exhibit
characteristic "attraction/repulsion" behavior under an applied
time-varying electric field. As such, Zhang et al further teaches a
technique that uses the characteristic "attraction/repulsion"
behavior as a basis for collecting "targeted" CNTs of specific tube
chirality and diameter.
[0006] With respect to a CNT's "attraction/repulsion" behavior,
Zhang et al. teaches that the system energy of a CNT placed in a
time-varying electric field is U=-1/2.epsilon..sub.0.chi.E.sup.2
where .epsilon..sub.0 is the permitivity of free space, .chi. is
the dielectric susceptibility of the CNT and E.sup.2 is the
intensity of the time-varying electric field. The dielectric
susceptibility .chi. describes the collective orientation and
strength of the individual electric dipole moments of the CNT in
response to the applied time-varying electric field. According to
Zhang et al., the dielectric susceptibility .chi. is a function of
the frequency of the applied electric field; and, more importantly,
that the collective "direction" of the CNT's electric dipole
moments change as a function of frequency.
[0007] Specifically, for applied electric field frequencies beneath
a "resonant" frequency, the dipole moments collectively "point" in
a direction that causes the CNT to move towards increasing electric
field intensity (i.e., the CNT is attracted to regions of
increasing electric field intensity because lower system energy
results from higher electric field intensities); while, for applied
electric field frequencies above the aforementioned resonant
frequency, the dipole moments collectively "point" in a direction
that causes the CNT to move away from increasing electric field
intensity (i.e., the CNT is repelled from regions of increasing
electric field intensity because higher system energy results from
higher electric field intensities). If the frequency of the applied
time-varying electric field is at the resonant frequency, the
collective pointing direction and motion of the CNT is
unstable.
[0008] Zhang et al also teaches that the specific resonant
frequencies of a CNT are a function of its energy bandgaps, and
that, the energy bandgaps of a CNT are a function of the CNT's
chirality and diameter. Hence, the aforementioned characteristic
attraction/repulsion behavior of a CNT in response to an applied
time-varying electric field is a function of the CNT's chirality
and diameter.
[0009] Zhang et al. further describes a technique for sorting CNTs
based upon the above described attraction/repulsion behavior. In
particular, if an electric field is applied to a group of CNTs
having diverse chiralities and diameters (e.g., such as a batch of
CNTs produced by a single manufacturing process run), a specific
CNT can be collected through the application of a time-varying
electric field whose frequency is tailored in light of the resonant
frequency of the CNT sought to be collected. FIGS. 1a through 1c
demonstrate the technique in more detail.
[0010] FIG. 1a shows a fluidic flow 103 containing manufactured
CNTs. It is assumed that the manufactured CNTs have various
combinations of diameter and chirality. For simplicity, FIG. 1a
shows only two types of manufactured CNTs: 1) a first group 105,
107, 110, 111, 112, 114, 117, 119 having a first chirality and
diameter combination; and, 2) a second group 106, 108, 109 113,
115, 116, 118, 120 having a second chirality and diameter
combination. All of the CNTs 105 through 120 enter the apparatus as
part of fluidic flow 103.sub.1. A second fluidic flow 104 flows
along side fluidic flow 103.
[0011] The general idea is that a particular type of CNT, such as
the CNTs associated with the first group defined above, is to be
extracted from fluidic flow 103 and introduced to fluidic flow 104.
Thus, CNTs of the first type will flow out of the apparatus as part
of fluid flow 104.sub.2 and CNTs of the second type will flow out
of the apparatus as part of fluid flow 103.sub.2.
[0012] The extraction process uses the electric field component of
a laser beam to apply the time-varying electric field. A laser beam
spot 101 is drawn as being impingent upon fluid flow 103. The laser
beam is focused and thus converges to a source image 102 further
along the x axis approximately within the center of fluid flow
103's cross section (FIG. 2, which is discussed in more detail
ahead, provides a three dimensional perspective of a laser beam
focused as just described).
[0013] A focused point 102 in the center of the fluid flow causes
the electric field intensity of any region that is illuminated by
the laser beam to increase in the direction toward the focused
point 102. Therefore, by selecting a laser beam frequency that is
beneath the resonant frequency of the first group of CNTs but above
the resonant frequency of the second group of CNTs, CNTs from the
first group will be attracted toward the focused point 102 while
CNTs from the second group will be repelled from the focused point
102.
[0014] At the instant of time represented by FIG. 1a, sweeping the
laser beam from fluid flow 103 to fluid flow 104 will cause CNTs
105 and 107 to be pulled, as a consequence of their attraction to
focused point 102, into fluid flow 104; while, CNT 106, as a
consequence of its repulsion from point 102, will remain in fluid
flow 103. The situation after the sweeping of the laser beam is
depicted in FIG. 1b.
[0015] It is clear from the situation of FIG. 1b that CNTs 105 and
107 will exit as part of exit flow 104.sub.2 and that CNT 106 will
exit as part of exit flow 103.sub.2. FIG. 1c shows the situation if
the laser beam is swept again from flow 103 to 104 so as to capture
CNTs 110, 111 and 112 from flow 103 and introduce them to flow 104.
It is also clear that repeating this sweeping motion will cause the
CNTs of the first group to exit as part of exit flow 104.sub.2 and
that CNTs of the second group will exit as part of exit flow
103.sub.2. Thus, the sorting of CNTs is accomplished.
FIGURES
[0016] The present invention is illustrated by way of example, and
not limitation, in the figures of the accompanying drawings in
which like references indicate similar elements and in which:
[0017] FIG. 1 (prior art) shows a technique for sorting CNTs that
employs the sweeping of a laser beam;
[0018] FIG. 2 shows attraction/repulsion behavior of CNTs of
diverse chirality and diameter in response to the electric field
component of a focused laser beam within a fluidic flow containing
the CNTs;
[0019] FIG. 3 shows a technique that employs a stationary laser
beam to sort CNTs within a fluidic flow;
[0020] FIG. 4 shows an expansion of the technique of FIG. 3 in
which a plurality of stationary laser beams are used to sort CNTs
within a fluidic flow;
[0021] FIG. 5 shows a cascaded sorting apparatus for sorting
multiple types of CNTs within a fluid flow;
[0022] FIG. 6 shows an expanded version of the cascade sorting
apparatus of FIG. 5;
[0023] FIG. 7 shows a sorting apparatus for producing purified
concentrations of targeted CNTs;
[0024] FIGS. 8a through 8f show CNT sorting where collected CNTs
flow along a different vertical plane than the plane along which
CNTs to be sorted flow.
DESCRIPTION
[0025] FIG. 2 provides a three dimensional perspective of the
attraction/repulsion behavior of CNTs within a fluidic flow in
response to the electric field component of a focused laser beam.
Here, FIG. 2 is drawn from the perspective of a cross section of
the fluid flow. That is, FIG. 2 is consistent with FIG. 1 in that
the fluidic flow is assumed to be in the +z direction. The cross
section 211 of the fluid flow is assumed to be rectangular. The
region of the fluidic flow that is illuminated by light from the
focused laser beam light is drawn as not being shaded; and, the
region of the fluidic flow that is not illuminated by the light
from the focused laser beam is drawn as being shaded.
[0026] The laser beam light is focused 212 in approximately the
middle of the fluidic flow so as to establish a gradient in
electric field intensity throughout the illuminated region.
Specifically, within the illuminated region, the electric field
intensity increases in any direction toward the focused spot 212.
Here, unlike FIG. 1, note that the CNTs 201 through 210 in the
fluidic flow of FIG. 2 are depicted as being concentrated on one
side of the fluidic flow (i.e., the right hand side).
[0027] Vectors are drawn from each of the CNTs 201-210 in FIG. 2 to
demonstrate the direction of the induced motion that each CNT will
experience under the influence of the electric field component of
the laser beam. Here, CNTs 201, 202, 203, 204, 205 are like the
"second group" discussed above with respect to FIG. 1 in that each
of these CNTs is repelled from focused spot 212. Also, CNTs 206,
207, 208, 209, 210 are like the "first group" discussed above with
respect to FIG. 1 in that each of these CNTs is attracted to
focused spot 212. The vector arrangement observed in FIG. 2 can be
configured, for instance, if the frequency of the laser light is
less than the resonant frequency of the first group CNTs but higher
than the second group CNTs.
[0028] Importantly, because the CNTs 201-210 are concentrated on
the right hand side of focused spot 212, the vector of every CNT
from the second group has a component directed along the -y axis;
and, the vector of every CNT from the first group has a component
directed along the +y axis. As such, all CNTs from the second group
will exhibit some degree of momentum/motion in the -y direction and
all CNTs from the first group will exhibit some degree of
momentum/motion in the +y direction.
[0029] As such, a sorting mechanism is made to exist. That is,
collectively, the first group CNTs are moving in a direction
opposite that of the second group CNTs. Given enough time, without
any collisions, the CNTs from the different groups will completely
separate from one another even if the laser beam light is removed
(i.e., conservation of momentum acts to allow the CNTs to continue
to travel along the vectors indicated). This new separation
technique just described above, unlike the technique discussed
above with respect to FIG. 1, does not need to sweep the laser
beam. That is, the laser beam can remain substantially fixed
("static") in terms of its position within the fluidic flow. Thus,
at least with respect to the optics, the new technique of FIG. 2
should be less complicated than the technique of FIG. 1.
[0030] In order to effect the separation mechanism of FIG. 2, as
mentioned above, the CNTs should be concentrated toward the side of
the focused laser beam spot 212. FIG. 3 depicts an apparatus
configured to influence the flow of CNTs along a side of a focused
laser beam spot 312 so as to effect the sorting technique described
just above. According to the apparatus of FIG. 3, two fluidic flows
303, 304 are made to run along side one another in the +z
direction. CNTs are introduced along the input flow of fluidic flow
304 (i.e., fluidic flow 304.sub.1). The basic strategy is to
attract "targeted" CNTs of specific chirality and diameter (or
range thereof) from fluidic flow 304 to fluidic flow 303.
[0031] The laser beam light is configured to effect the attraction
of the targeted CNTs. In particular, because only those CNTs that
are illuminated by the light are affected by the sorting technique,
the diameter of the laser beam light 301 is made expansive so as to
illuminate as many CNTs from fluidic flow 304.sub.1 as is possible.
Here, one technique for focusing laser beam light from an expansive
beam is to focus the light from a large numerical aperture (NA)
lens (e.g., an NA between 0.5 and 1.5 inclusive). Moreover, the
focused spot 312 is placed within fluidic flow 303 (or at the
border of fluidic flow 303 and 304) and proximate to the
convergence of input flows 303.sub.1 and 304.sub.1 so as to ensure
that targeted CNTs are not repelled from fluidic flow 303. Lastly,
the laser beam's electric field component has a frequency that is
less than the resonant frequency of the targeted CNTs.
[0032] FIG. 3 shows exemplary motion vectors for those CNTs that
are illuminated by the laser beam light 301. All of the observed
motion vectors have a component in the +z direction at least
because of the fluidic flow. Moreover, the targeted CNTs have a
motion component in the +y direction toward fluidic flow 303; and,
the non targeted CNTs have a motion component in the -y direction
away from fluidic flow 303. As a consequence of their +y motion
components, the targeted CNTs will drift into fluidic flow 303 even
after they flow downstream past the laser light 301 (i.e.,
conservation of momentum acts to cause the targeted CNTs to
continue traveling in the +y direction even after they are no
longer irradiated with a time varying electric field). Likewise, as
a consequence of their -y motion components, the non-targeted CNTs
will drift away from fluidic flow 303 even after they flow
downstream past the laser light 301 (i.e., conservation of momentum
acts to cause the non targeted CNTs to continue traveling in the -y
direction even after they are no longer irradiated with a time
varying electric field). As such, by the time the fluidic flows
reach their exit regions, the targeted CNTs will be carried by exit
flow 303.sub.2 and the non-targeted CNTs will be carried by exit
flow 304.sub.2.
[0033] FIG. 4 shows an improvement over the basic apparatus of FIG.
3. According to the approach of FIG. 4, a plurality of laser beams
401.sub.1 through 401.sub.4 are used to attract the targeted CNTs.
Here, although four separate laser beams are shown, it should be
understood that more or less than four laser beams may be used
depending on design. Like the approach of FIG. 3, a pair of fluid
flows 403, 404 are made to run along side one another. CNTs enter
the apparatus as part of entry flow 404.sub.1.
[0034] The plurality of laser beams 401.sub.1-401.sub.4 effectively
set up a wall of light that continually attracts targeted CNTs
toward fluid flow 403 and continually repels non targeted CNTs away
from fluid flow 403 as the CNTs flow for an extended distance
downstream (e.g., according to one embodiment, the electric field
component of each laser beam has a frequency that is less than the
resonant frequency of the targeted CNTs). Like the approach of FIG.
3, targeted CNTs should emerge from exit flow 403.sub.2 and non
targeted CNTs should emerge from exit flow 404.sub.2. Of course, a
series of lenses could be used to form the wall of light.
[0035] In the embodiment of FIG. 4, the "wall" of laser beams are
oriented such that the wall gradually recedes further and further
in the +y direction into fluidic flow 403. The effect of orienting
the wall in this manner is to begin to attract targeted CNTs in the
proximity of the first beam 401.sub.1 and then "hand off" the
targeted CNTs to the attractive forces of the second beam
401.sub.2. As the targeted CNTs move downstream they are next
"handed off" to the attractive forces of the third beam 401.sub.3.
By the time the targeted CNTs have moved sufficiently downstream to
be handed off to the attractive forces of the fourth beam
401.sub.4, they are well within fluidic flow 403 and therefore
should exit the apparatus from exit flow 403.sub.2.
[0036] By contrast, any non targeted CNTs that reside within
fluidic flow 403 should be repelled by the wall of light. In the
embodiment of FIG. 4, the last beam 401.sub.4 is sufficiently
distant from exit flow 404.sub.2 so as to allow any non targeted
CNT that is provided momentum toward fluidic flow 404 by the
repelling forces of beam 401.sub.4 enough time to drift into
fluidic flow 404.
[0037] In a further embodiment, the focused spots of the laser
beams 401.sub.1 through 401.sub.4 are positioned at different
levels along the x axis so as to more fully illuminate the fluidic
flows through the apparatus. As a consequence, the collection
efficiency of targeted CNTs should be more efficient than the
approach of FIG. 3. In order to understand the concept in more
detail, referring to FIG. 2, note that the motion of targeted and
non targeted CNTs alike will not be affected for those CNTs that
pass only through the non illuminated shaded region. By having
multiple beams whose focused spots are positioned at different
levels along the x axis, fewer targeted CNTs should be able to
"miss" the illuminated regions of fluidic flow.
[0038] In an alternative embodiment, in order to even further
enhance the collection efficiency of the targeted CNTs, the wall of
laser beams not only include different x axis locations for its
respective focused spots, but also, the wall is not made to recede
gradually into fluidic flow 403 and instead runs in the +z
direction (i.e., substantially along the direction of the fluidic
flow). So orienting the wall of laser beams creates an even greater
likelihood that all CNTs will flow through the illuminate region of
at least one laser beam.
[0039] FIG. 5 shows another embodiment is which of pair of sorters
like that in FIG. 4 are coupled in a cascaded fashion so as to sort
multiple types of CNTs. In particular, the sorter apparatus of FIG.
5 is meant to sort three different kinds of CNTs: "dotted",
"shaded" and "darkened". The first wall 501 is constructed of light
whose frequency is less than that of the resonant frequency of the
"dotted" CNTs but greater than that of the "shaded" and "darkened"
CNTs. The second wall 502 is constructed of light whose frequency
is less than the resonant frequency of the "shaded" CNTs but
greater than the resonant frequency of the "darkened" CNTs.
[0040] CNTs are entered at entry flow 503. From the arrangement
described above, the first wall 501 will attract "dotted" CNTs such
that they flow from exit flow 504 and will repel the "shaded" and
"darkened" CNTs into the flow that flows to wall 502. The second
wall 502 will attract "shaded" CNTs such that they flow from exit
flow 505 and will repel "darkened" CNTs such that they flow from
exit flow 506. In an embodiment, the "dotted" CNTs have the lowest
resonant frequency amongst all the CNTs and the "shaded" CNTs have
the second lowest resonant frequency amongst all the CNTs. So doing
guarantees that any missed "dotted" CNTs targeted by wall 501 will
be repelled by wall 502 so as not to taint output flow 505 with
"dotted" CNTs.
[0041] In order to enhance the collection efficiency of any of the
sorting techniques observed in FIGS. 3, 4 and 5, the fluid flow
that is not fed by a attractive force may be fed back to the input
flow. For example, referring to FIG. 3, exit flow 304.sub.2 may be
fed back to input flow 304.sub.1; referring to FIG. 4, exit flow
404.sub.2 may be fed back to input flow 404.sub.1; and, referring
to FIG. 5, exit flow 506 may be fed back to input flow 503. Here,
it is assumed that all targeted CNTs may not be caught by the
attractive forces of the light beam(s) that have been configured to
capture them. As such, there is some probability that targeted CNTs
will not flow out the desired exit port the first time they pass by
the light.
[0042] In the case of FIGS. 3 and 4, coupling flow 304.sub.2 back
to flow 304.sub.1 and flow 404.sub.2 back to flow 404.sub.1 allows
those targeted CNTs that were not captured (i.e., "missed") along a
pass by of the laser light to have another chance at being
captured. Moreover, in the case of FIG. 5, coupling flow 506 back
to flow 503, permits "dotted" CNTs that were not captured along a
pass-by of wall 501 to be recaptured. Here, as described above, any
missed "dotted" CNTs will be repelled by wall 502 provided that the
"dotted" CNTs have lower resonant frequency than the "shaded"
CNTs.
[0043] As another approach, to increase the total flow of targeted
CNTs per cycle, the cascade structure of FIG. 5 may be used where
the electric field component frequency of both walls 501, 502 is
the same (or, at least, the electric field component frequencies of
both walls 501, 502 are tailored to attract the same CNTs).
According to this approach, should any targeted CNTs "miss" wall
501, they may be attracted by wall 502 so as to flow from output
flow 505. Additional stages may be added to further increase the
sorting efficiency.
[0044] FIG. 6 shows a multi-dimensional expansion of the sorting
strategy of FIG. 5 in which the electric field intensity of various
applied laser beams are configured to provide multiple output flows
for different types of targeted CNTs. According to the technique of
FIG. 6, a batch of manufactured CNTs are entered at input flow 601
and the electric field component frequency f1 of a first laser beam
602 (wall or otherwise) divides (e.g., approximately "in half") the
anticipated range of manufactured chirality and diameter
combinations such that those CNTs having a resonant frequency
beneath f1 are attracted to fluidic flow leg 603 and that those
CNTs having a resonant frequency above f1 are repelled to fluidic
flow leg 604.
[0045] The electric field component frequency f2 of a second laser
beam 605 (wall or otherwise, where f2 is less than f1) divides
(e.g., approximately "in half") those CNTs that flow through leg
603 such that those CNTs having a resonant frequency beneath f1 and
f2 are attracted to fluidic flow leg 614 and those CNTs having a
resonant frequency beneath f1 and above f2 are repelled to fluidic
flow leg 613. The electric field component frequency f3 of a third
laser beam 606 (wall or otherwise, where f3 is greater than f1)
divides (e.g., approximately "in half") those CNTs that flow
through leg 604 such that those CNTs having a resonant frequency
above f1 and beneath f3 are attracted to fluidic flow leg 612 and
those CNTs having a resonant frequency above f1 and above f3 are
repelled to fluidic flow leg 611.
[0046] The electric field component frequency f4 of a fourth laser
beam 610 (wall or otherwise, where f4 is less than f2) divides
(e.g., approximately "in half") those CNTs that flow through leg
614 such that those CNTs having a resonant frequency beneath f1, f2
and f4 are attracted to fluidic flow leg 615 and those CNTs having
a resonant frequency beneath f1 and f2 and above f4 are repelled to
fluidic flow leg 616. The electric field component frequency f5 of
a fifth laser beam 609 (wall or otherwise, where f5 is greater than
f2 but less than f1) divides (e.g., approximately "in half") those
CNTs that flow through leg 613 such that those CNTs having a
resonant frequency beneath f1, above f2 and beneath f5 are
attracted to fluidic flow leg 617 and those CNTs having a resonant
frequency beneath f1, above f2 and above f5 are repelled to fluidic
flow leg 618.
[0047] The electric field component frequency f6 of a sixth laser
beam 608 (wall or otherwise, where f6 is less than f3 but greater
than f1) divides (e.g., approximately "in half") those CNTs that
flow through leg 612 such that those CNTs having a resonant
frequency above f1, beneath f3 and below f6 are attracted to
fluidic flow leg 619 and those CNTs having a resonant frequency
above f1 beneath f3 and above f6 are repelled to fluidic flow leg
620. The electric field component frequency f7 of a seventh laser
beam 607 (wall or otherwise, where f7 is greater than f1 and f3)
divides (e.g., approximately "in half") those CNTs that flow
through leg 611 such that those CNTs having a resonant frequency
above f1, above f3 and beneath f7 are attracted to fluidic flow leg
621 and those CNTs having a resonant frequency above f1, above f3
and above f7 are repelled to fluidic flow leg 622.
[0048] FIG. 7 shows another approach that may be used to produce
high purity concentrations of targeted CNTs (i.e., the collection
of CNTs outside the targeted range is diminished). FIG. 7 is
comparable to FIG. 5 except that an output fluid channel 705 exists
that is fed by two or more laser beam walls 701, 702 that attract
the targeted CNTs. That is, laser beam wall 701 attracts targeted
CNTs into fluidic flow 704; and, laser beam wall 702 attracts
targeted CNTs into fluidic flow 705. As such, in order for a non
targeted CNT to exit from fluidic flow 705, it will have to escape
the repelling forces of both of walls 701 and 702. Additional one
or more laser beam wall stages designed to attract targeted CNTs
can be designed to follow from fluidic flow 705 so as to further
enhance the purity of the ultimate output flow.
[0049] In the above descriptions, the electric component frequency
of the applied laser light has always been suggested to be less
than the resonant frequency of the "targeted" CNTs. In reverse
embodiments, rather than attempt to attract targeted CNTs as
described above, the electric field component frequency is set to
be greater than a targeted CNT's resonance (so as to repel the
targeted CNT) but less than one or more non targeted CNTs (so as to
attract the non targeted CNTs). In this case, for example,
referring to FIGS. 3, 4 and 5, the targeted CNTs emanate from flows
304.sub.2, 404.sub.2, and 506, respectively.
[0050] FIGS. 8a-8c shows another embodiment of a sorting technique
using stationary laser light where collected CNTs flow along a
different vertical plane than the flow of CNTs to be sorted 803.
According to the approach of FIGS. 8a-8c, a flow of CNTs to be
sorted 803 flows along a first flow channel 801 that runs "beneath"
(when measured along the x axis) a second fluid channel 802 that is
designed to collect targeted CNTs within the flow of CNTs to be
sorted 803. The fluid flow of the second channel 802 runs in the +y
direction. As such, pure fluid 805 flows in channel 802 before the
intersection of channels 801 and 802; and, a fluid flow of
collected, targeted CNTs 806 flows after the intersection of
channels 801 and 802.
[0051] Laser beam light is shaped and given the appropriate
electric field component frequency to attract targeted CNTs from
flow 803 "up" into channel 802. According to the observed
depiction, a focused spot of the laser light 808 is positioned such
that: 1) the laser's light 809 illuminates the intersection region
of the two channels; and, 2) the flow of CNTs to be sorted 803 run
along a side of the circular/elliptical shape of the light 809
similar to that described with respect to FIG. 2 (in particular, as
observed, flow 803 runs through a "lower" portion of the
circular/elliptical field of light 809. Moreover, the frequency of
the electric field component of the light is made to have a
frequency that is less than the resonant frequency of the targeted
CNTs.
[0052] These conditions will cause an increasing electric field
intensity gradient to be established in the region of intersection
of the two channels so that: 1) targeted CNTs will be pulled "up"
in the +x direction 807 from channel 801 into channel 802; and, 2)
non targeted CNTs (or at least those CNTs having a resonant
frequency above the laser beam's electric field component
frequency) will be repelled further "downward" in channel 802 in
the -x direction. As such targeted CNTs exit at flow 806 and non
targeted CNTs exit at flow 804.
[0053] In an alternate embodiment, the laser beam spot 808 could be
lowered directly from its depicted position beneath channel 801 and
the frequency of the electric field component of the light could be
raised above the resonant frequency of the targeted CNTs but
beneath the resonant frequency of all other CNTs. This approach
would "repel" the targeted CNTs "up" into channel 802 and would
attract all other CNTs to remain in channel 801.
[0054] A potential implementation issue with the approach of FIGS.
8a-8c is the optics. That is, assuming channel 801 is truly
"beneath" channel 802, the light 809 is focused along the side of
the chip/carrier that the channels 801, 802 are constructed in.
FIGS. 8d and 8e show another approach that is perhaps easier to
implement that the approach of FIGS. 8a-8c if channel 802 is higher
along the vertical axis than channel 801. According to the approach
of FIGS. 8d and 8e, the applied light 810 will travel along the
vertical axis if channels 801, and 802 run along different vertical
planes.
[0055] The behavior of the various flows 803 through 807 are the
same as described with respect to FIGS. 8a through 8c. Note that
according to the depictions of FIGS. 8d and 8e, the electrical
component of the applied light 810 will have a frequency beneath
the resonant frequency of the targeted CNTs to attract them "up"
into channel 802. In an alternate approach, the focal point 808 of
the light can be lowered to the bottom of channel 801 (or beneath
channel 801) and the frequency of the electrical component of the
light can be set above the resonant frequency of the targeted CNTs.
This will cause the targeted CNTs to be repelled "up" into
channel.
[0056] FIG. 8f shows an elaboration on the technique of FIGS. 8d
and 8e. Here, multiple beams of light are depicted as being applied
through the intersection of channels 801 and 802. Similar to the
discussion provided above with respect to FIG. 4, multiple beams of
light can improve the collection efficiency by applying stronger
electric field intensity gradients and/or applying light to a
channel region that might receive little or no light with a single
applied beam of light. According to the depiction of FIG. 8f, focal
points of the various beams are found along the z axis. Similarly,
although not shown, focal points of other additional beams may be
found along the y axis. Also, and again not depicted in FIG. 8f,
the focal points may be positioned at different x axis levels to
form the collection light appropriately. Multiple beams of light
may be applied to the collection approach described in FIGS. 8a
through 8c as well as the collection approach of FIGS. 8d and 8e as
just described. Finally, the beams of light may be positioned to
attract or repel targeted CNTs based upon the position of the focal
points.
[0057] For any of the approaches described above note that if the
laser power is high it will produce strong attraction/repulsion
forces which corresponds to a strong optical force. Generally, in
order to provide the strongest sorting affect, it is advisable to
maintain the flow rate at a level that causes the drag forces
created by the flow to be smaller than the optical
attraction/repulsion forces. In terms of the useable solution(s)
for implementing the fluid flows, water or any solution that
solubilizes CNTs may be used (water, organic solvents, acids, etc.)
provided that the solution does not destroy the fluidic
channel.
[0058] In the foregoing specification, the invention has been
described with reference to specific exemplary embodiments thereof.
It will, however, be evident that various modifications and changes
may be made thereto without departing from the broader spirit and
scope of the invention as set forth in the appended claims. The
specification and drawings are, accordingly, to be regarded in an
illustrative rather than a restrictive sense.
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