U.S. patent application number 13/642913 was filed with the patent office on 2013-06-27 for functionalized surface for flow control device.
This patent application is currently assigned to HALLIBURTON ENERGY SERVICES, INC.. The applicant listed for this patent is Jason D. Dykstra, Michael Linley Fripp, Michael T. Pelletier. Invention is credited to Jason D. Dykstra, Michael Linley Fripp, Michael T. Pelletier.
Application Number | 20130161018 13/642913 |
Document ID | / |
Family ID | 48653431 |
Filed Date | 2013-06-27 |
United States Patent
Application |
20130161018 |
Kind Code |
A1 |
Fripp; Michael Linley ; et
al. |
June 27, 2013 |
Functionalized Surface for Flow Control Device
Abstract
Flow control devices can include functionalized surfaces on
inner regions of walls. A functionalized surface can include a
hydrophilic and/or a hydrophobic material that can affect fluid
flowing in a flow path of a wall to facilitate fluid selection by
the flow control device. Fluids may be switched in a flow control
device using a functionalized surface even when a density and
viscosity of different oil and water mixtures of the fluids are the
same.
Inventors: |
Fripp; Michael Linley;
(Carrollton, TX) ; Pelletier; Michael T.;
(Houston, TX) ; Dykstra; Jason D.; (Carrollton,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Fripp; Michael Linley
Pelletier; Michael T.
Dykstra; Jason D. |
Carrollton
Houston
Carrollton |
TX
TX
TX |
US
US
US |
|
|
Assignee: |
HALLIBURTON ENERGY SERVICES,
INC.
Houston
TX
|
Family ID: |
48653431 |
Appl. No.: |
13/642913 |
Filed: |
December 21, 2011 |
PCT Filed: |
December 21, 2011 |
PCT NO: |
PCT/US11/66410 |
371 Date: |
October 23, 2012 |
Current U.S.
Class: |
166/319 |
Current CPC
Class: |
E21B 34/06 20130101;
E21B 34/08 20130101 |
Class at
Publication: |
166/319 |
International
Class: |
E21B 34/06 20060101
E21B034/06 |
Claims
1. (canceled)
2. The assembly of claim 10, wherein the wall is adapted to be
positioned antecedent in a flow path to a switching mechanism for a
flow control device.
3. The assembly of claim 2, wherein at least one of the hydrophobic
material or the hydrophilic material is adapted to increase surface
roughness of part of the inner region of the wall based on at least
one property of fluid flowing through the flow path.
4. The assembly of claim 2, wherein at least one of the hydrophobic
material or the hydrophilic material is adapted to cause fluid
flowing through the flow path to oscillate, resulting in an
increase differential pressure for the fluid during flow through
the flow path to the switching mechanism.
5. The assembly of claim 4, wherein at least one of the hydrophobic
material or the hydrophilic material is adapted to cause fluid
flowing through the flow path to oscillate by changing a velocity
profile of the fluid flowing through the flow path.
6. The assembly of claim 2, wherein the switching mechanism is
adapted to be positioned between a vortex assembly and the first
portion and the second portion of the inner region of the wall, the
switching mechanism comprising a plurality of passageways that
provide separate flow paths to the vortex assembly.
7. The assembly of claim 10, wherein at least one of: first
material on the first portion of the inner region of the wall is
configured to change to the hydrophobic material in response to
stimuli applied to the first material in the wellbore; or second
material on the second portion of the inner region of the wall is
configured to change to the hydrophilic material in response to the
stimuli applied to the second material in the wellbore.
8. The assembly of claim 7, wherein the stimuli comprises one of:
light; electric energy; or a chemical.
9. The assembly of claim 10, wherein the first portion and the
second portion are in a pattern on the inner region of the
wall.
10. An assembly capable of being positioned in a wellbore, the
assembly comprising: a hydrophobic material on a first portion of
an inner region of a wall; and a hydrophilic material on a second
portion of the inner region of the wall, wherein the first portion
is on an opposite side of the inner region of the wall to the
second portion.
11. (canceled)
12. A flow control device adapted to be positioned in a wellbore,
the flow control device comprising: an inner region of a wall
comprising a portion having a hydrophilic material thereon; and a
switching mechanism subsequent to the portion in a flow path of the
flow control device, wherein the inner region of the wall further
comprises a second portion having a hydrophobic material
thereon.
13. The flow control device of claim 12, wherein the portion and
the second portion are in a pattern on the inner region of the
wall.
14. The flow control device of claim 12, wherein the portion is on
an opposite side of the inner region of the wall to the second
portion.
15. The flow control device of claim 12, wherein the hydrophilic
material is adapted to increase surface roughness of part of the
inner region of the wall in response to fluid having a higher
concentration of water than other types of fluid.
16. The flow control device of claim 15, wherein the part of the
inner region of the wall having the increase surface roughness is
configured to change a velocity profile of the fluid having the
higher concentration of water than other types of fluid, wherein
the switching mechanism is configured to cause the fluid to be
selected using the change to the velocity profile of the fluid.
17. The flow control device of claim 12, wherein the hydrophilic
material comprises a material that changes to the hydrophilic
material in response to stimuli applied to the material in the
wellbore, wherein the stimuli comprises one of: light; electric
energy; or a chemical.
18. (canceled)
19. A flow control device adapted to be positioned in a wellbore,
the flow control device comprising: an inner region of a wall
comprising a portion having a hydrophobic material thereon; and a
switching mechanism subsequent to the portion in a flow path of the
flow control device, wherein the inner region of the wall further
comprises a second portion having a hydrophilic material
thereon.
20. The flow control device of claim 19, wherein the hydrophobic
material is adapted to increase surface roughness of part of the
inner region of the wall in response to fluid having a higher
concentration of hydrocarbons than other types of fluid.
Description
TECHNICAL FIELD OF THE INVENTION
[0001] The present invention relates generally to flow control
devices having a functionalized material on a surface configured to
affect fluid flow in a bore in a subterranean formation in and,
more particularly (although not necessarily exclusively), to
hydrophilic and/or hydrophobic materials in a flow control device
that can affect fluid flow.
BACKGROUND
[0002] Various devices can be installed in a well traversing a
hydrocarbon-bearing subterranean formation. Some devices control
the flow rate of fluid between the formation and tubing, such as
production or injection tubing. An example of these devices is an
autonomous valve that can select fluid, or otherwise control the
flow rate of various fluids into the tubing.
[0003] An autonomous valve can select between desired and undesired
fluids based on relative viscosity of the fluids. For example,
fluid having a higher concentration of undesired fluids (e.g. water
and natural gas) may have a certain viscosity in response to which
the autonomous valve directs the undesired fluid in a direction to
restrict the flow rate of the undesired fluid into tubing. The
autonomous valve may include a switching mechanism that is, for
example, in a flow ratio control device and may include a vortex
assembly usable to select fluid based on viscosity. The flow ratio
control assembly can include two passageways. Each passageway can
include narrowed tubes that are configured to restrict fluid flow
based on viscosity of the fluid. For example, one tube in the first
passageway may be narrower than the second tube in the second
passageway, and configured to restrict fluid having a certain
relative viscosity more than fluid having a different relative
viscosity. The second tube may offer relatively constant resistance
to fluid, regardless of the viscosity of the fluid.
[0004] Fluid entering the vortex assembly via a first passageway,
such as a passageway that is tangential to the vortex assembly, may
be caused to rotate in the vortex assembly and restricted from
exiting an exit opening in the vortex assembly. Fluid entering the
vortex assembly via a second passageway, such as a passageway that
is radial to the vortex assembly, may be allowed to exit through
the exit opening without any, or much, restriction.
[0005] Although this autonomous valve is very effective in meeting
desired fluid selection downhole, devices that can facilitate
greater fluid switching are desirable.
SUMMARY
[0006] Certain aspects and embodiments of the present invention are
directed to at least one material on an inner region of a wall. The
material may facilitate directing fluid flow through the flow path
to, for example, a switching mechanism of a flow control
device.
[0007] One aspect relates to an assembly that can be positioned in
a wellbore. The assembly includes a hydrophobic material and a
hydrophilic material. The hydrophobic material is on a first
portion of an inner region of a wall. The hydrophilic material is
on a second portion of the inner region of the wall.
[0008] Another aspect relates to a flow control device that can be
positioned in a wellbore. The flow control device includes an inner
region of a wall and a switching mechanism. The inner region of the
wall includes a portion that has a hydrophilic material on it. The
switching mechanism is subsequent to the portion in a flow path of
the flow control device.
[0009] Another aspect relates to a flow control device that can be
positioned in a wellbore. The flow control device includes an inner
region of a wall and a switching mechanism. The inner region of the
wall includes a portion that has a hydrophobic material on it. The
switching mechanism is subsequent to the portion in a flow path of
the flow control device.
[0010] These illustrative aspects are mentioned not to limit or
define the invention, but to provide examples to aid understanding
of the inventive concepts disclosed in this application. Other
aspects, advantages, and features of the present invention will
become apparent after review of the entire application.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a schematic illustration of a well system having
flow control devices that can include a functionalized surface
according to one embodiment of the present invention.
[0012] FIG. 2 is a cross-sectional side view of a screen and a flow
control device with a functionalized surface that includes a
hydrophilic or a hydrophobic material according to one embodiment
of the present invention.
[0013] FIG. 3 is a cross-sectional top view of a flow control
device that includes hydrophilic material and hydrophobic material,
and fluid flow having a greater concentration of a first type of
fluid according to one embodiment of the present invention.
[0014] FIG. 4 shows the flow control device of FIG. 3 with fluid
flow having a greater concentration of a second type of fluid
according to one embodiment of the present invention.
[0015] FIG. 5 is a cross-sectional side view of a wall having a
hydrophobic material or hydrophilic material on the wall according
to one embodiment of the present invention.
[0016] FIG. 6 is a cross-sectional side view of a wall having a
hydrophobic material and a hydrophilic material on the wall in a
pattern according to one embodiment of the present invention.
[0017] FIG. 7 is a cross-sectional top view of a flow control
device with material on a wall that can respond to stimuli provided
to the material according to one embodiment of the present
invention.
DETAILED DESCRIPTION
[0018] Certain aspects and embodiments relate to a functionalized
surface of an inner region of a wall. The surface can be
functionalized using at least one of a hydrophobic material or a
hydrophilic material on a portion of the surface. The
functionalized surface can facilitate directing fluid flow through
the flow path to, for example, a switching mechanism of a flow
control device. For example, fluids may be switched in an assembly
using the functionalized surface even when a density and viscosity
of different oil and water mixtures of the fluids are the same.
[0019] Hydrophobic material may be a material that repeals fluid
having a high concentration of water. Hydrophilic material may be a
material that can bond with fluid having a high concentration of
water, such that the effect may be that the material attracts fluid
having a high concentration of water. In some embodiments,
hydrophobic material may attract fluid having a high concentration
of oil or other hydrocarbon, and hydrophilic material may repeal
fluid having a high concentration of oil or other hydrocarbon.
[0020] Examples of hydrophilic material include aluminum oxide,
silica compounds such as silicon oxide, nylon, and smooth
Teflon.RTM.. Examples of hydrophobic material include nylon with
alcohol, textured Teflon.RTM., silicone oils, metal surfaces (which
may be metal surfaces other than metal oxides), and textured metal
surfaces. Hydrophobic material in some embodiments may be created
by imbedding polar compounds or asphaltenes into a structural
matrix in an inner wall of an assembly. For example, surfaces that
include sulfur, graphite, and coal may become a hydrophobic
material.
[0021] In some embodiments, a wall can include a hydrophilic
material on one side of the wall and a hydrophobic material on an
opposite side of the wall. Fluid having a higher concentration of
water may flow through a flow path by the materials. The presence
of at least one of the material may change a velocity profile of
the fluid. For example, the fluid may be attracted to the side that
includes the hydrophilic material such that fluid flows with a
higher velocity on the opposite side of the wall. A switching
mechanism subsequent to the material in the flow path can use the
change in velocity profile to guide more fluid to one passageway
over another in a flow control device.
[0022] In other embodiments, hydrophobic material and hydrophilic
material can be patterned, such as alternating adjacent portions
with hydrophobic and hydrophilic material, on an inner region of a
wall. The patterned material may affect a velocity profile, or
otherwise affect flow, of fluid flowing by the patterned material,
depending on a property of the fluid. The property may include the
relative concentration of water or other type of fluid in the fluid
flow.
[0023] Material according to some embodiments may be in an inner
region of a wall that can respond to stimuli that is provided while
the material is in the wellbore to change, permanently or
temporarily, to a hydrophobic material and/or a hydrophilic
material. For example, certain material may be located in the wall
in a wellbore that, when exposed to a light of a certain frequency
or color, can change to a hydrophilic material for a definite
length of time. Material may respond to other stimuli, such as
electric energy or voltage, and chemicals introduced into the flow
path. Examples of material that may respond to stimuli to change to
a hydrophilic material include functionalized spiropyrans ferro
fluids and functionalized quinones. Examples of material that may
respond to stimuli to change to a hydrophobic material include
azobenzenes and functionalized azobenzens (thiol terminated).
Examples of additional materials that may respond to stimuli to
change to a hydrophilic and/or hydrophobic material include
self-assembled monolayers, shape-memory polymers, rotaxane,
catenane, DNA monolayers, and peptide monolayers.
[0024] These illustrative examples are given to introduce the
reader to the general subject matter discussed here and are not
intended to limit the scope of the disclosed concepts. The
following sections describe various additional embodiments and
examples with reference to the drawings in which like numerals
indicate like elements, and directional descriptions are used to
describe the illustrative embodiments but, like the illustrative
embodiments, should not be used to limit the present invention.
[0025] FIG. 1 depicts a well system 100 with chambers having flow
control devices according to certain embodiments of the present
invention that include hydrophobic and/or hydrophilic material in
inner regions of walls. The well system 100 includes a bore that is
a wellbore 102 extending through various earth strata. The wellbore
102 has a substantially vertical section 104 and a substantially
horizontal section 106. The substantially vertical section 104 and
the substantially horizontal section 106 may include a casing
string 108 cemented at an upper portion of the substantially
vertical section 104. The substantially horizontal section 106
extends through a hydrocarbon bearing subterranean formation
110.
[0026] A tubing string 112 extends from the surface within wellbore
102. The tubing string 112 can provide a conduit for formation
fluids to travel from the substantially horizontal section 106 to
the surface. Flow control devices 114 and production tubular
sections 116 in various production intervals adjacent to the
formation 110 are positioned in the tubing string 112.
[0027] On each side of each production tubular section 116 is a
packer 118 that can provide a fluid seal between the tubing string
112 and the wall of the wellbore 102. Each pair of adjacent packers
118 can define a production interval.
[0028] Each of the production tubular sections 116 can provide sand
control capability. Sand control screen elements or filter media
associated with production tubular sections 116 can allow fluids to
flow through the elements or filter media, but prevent particulate
matter of sufficient size from flowing through the elements or
filter media. In some embodiments, a sand control screen may be
provided that includes a non-perforated base pipe having a wire
wrapped around ribs positioned circumferentially around the base
pipe. A protective outer shroud that includes perforations can be
positioned around an exterior of a filter medium.
[0029] Flow control devices 114 can allow for control over the
volume and composition of produced fluids. For example, flow
control devices 114 may autonomously restrict or resist production
of formation fluid from a production interval in which undesired
fluid, such as water or natural gas for an oil production
operation, is entering. "Natural gas" as used herein means a
mixture of hydrocarbons (and varying quantities of
non-hydrocarbons) that exists in a gaseous phase at room
temperature and pressure and in a liquid phase and/or gaseous phase
in a downhole environment.
[0030] Formation fluid flowing into a production tubular section
116 may include more than one type of fluid, such as natural gas,
oil, water, steam and carbon dioxide. Steam and carbon dioxide may
be used as injection fluids to cause hydrocarbon fluid to flow
toward a production tubular section 116. Natural gas, oil and water
may be found in the formation 110. The proportion of these types of
fluids flowing into a production tubular section 116 can vary over
time and be based at least in part on conditions within the
formation and the wellbore 102. A flow control device 114 according
to some embodiments can reduce or restrict production from an
interval in which fluid having a higher proportion of undesired
fluids.
[0031] When a production interval produces a greater proportion of
undesired fluids, a flow control device 114 in that interval can
restrict or resist production from that interval. Other production
intervals producing a greater proportion of desired fluid, can
contribute more to the production stream entering tubing string
112. For example, the flow control device 114 can include
hydrophobic and/or hydrophilic material in a wall that can
facilitate the flow control device 114 in selecting fluid based on
one or more properties of the fluid.
[0032] Although FIG. 1 depicts flow control devices 114 positioned
in the substantially horizontal section 106, flow control devices
114 (and production tubular sections 116) according to various
embodiments of the present invention can be located, additionally
or alternatively, in the substantially vertical section 104.
Furthermore, any number of flow control devices 114, including one,
can be used in the well system 100 generally or in each production
interval. In some embodiments, flow control devices 114 can be
positioned in simpler wellbores, such as wellbores having only a
substantially vertical section. Flow control devices 114 can be
positioned in open hole environments, such as is depicted in FIG.
1, or in cased wells.
[0033] FIG. 2 depicts a cross-sectional side view of a production
tubular section 116 that includes a flow control device 114 and a
screen assembly 202. The production tubular defines an interior
passageway 204, which may be an annular space. Formation fluid can
enter the interior passageway 204 from the formation through screen
assembly 202, which can filter the fluid. Formation fluid can enter
the flow control device 114 from the interior passageway through an
inlet 206 to a flow path 208 of a vortex assembly 210 that includes
a switching mechanism 211. The flow control device 114 includes a
material 212 on an inner region of a wall of the flow control
device 114. The material 212 may be a hydrophobic or a hydrophilic
material that can facilitate fluid selection by the switching
mechanism 211.
[0034] FIGS. 3-4 show a flow control device according to one
embodiment. The flow control device includes a wall 302 and a
switching mechanism 304 providing a flow path to two passageways
306, 308 that allow fluid to flow to a vortex assembly 310 at a
radial angle (passageway 306) or a tangential angle (passageway
308). Fluid flowing into the vortex assembly 310 via passageway 306
may be guided to an exit opening 312 in the vortex assembly 310.
Fluid flowing into the vortex assembly 310 via passageway 308 may
be guided into a vortex about the exit opening 312 and restricted,
at least partially and for at least a certain amount of time, from
exiting through the exit opening 312.
[0035] Although a vortex assembly is depicted in FIGS. 3-4, any
fluid selection mechanism may be used.
[0036] On portions of the wall 302 are hydrophilic material 314 and
hydrophobic material 316. Hydrophilic material 314 and hydrophobic
material 316 may overlay the wall 302 or be embedded in the wall
302. FIGS. 3-4 depict hydrophilic material 314 on an opposite
portion of the wall 302 from the hydrophobic material 316, but
other configurations may be possible. For example, hydrophilic
material 314 may be on the same side of the wall 302 as hydrophobic
material 316. In other embodiments, hydrophilic material 314 is on
an opposite side of the wall 302 from hydrophobic material 316, but
not directly opposite from the hydrophobic material 316. In still
other embodiments, one of the hydrophilic material 314 or the
hydrophobic material 316 is used, but not both types of
materials.
[0037] FIGS. 3-4 show via arrows fluid flowing in a flow path
defined by the wall 302 and by the hydrophilic material 314 and
hydrophobic material 316. In FIG. 3, the fluid may have a high
concentration of water. Part of the fluid flowing proximate the
hydrophilic material 314 may be attracted to the hydrophilic
material 314, and in some cases may accumulate on the hydrophilic
material 314. Accumulating fluid on the hydrophilic material 314,
or otherwise the attraction of fluid toward the hydrophilic
material 314, may change the effective surface roughness of the
wall 302 to cause a change in a velocity profile to at least part
of the fluid flowing in the flow path. The change in velocity may
be used by the switching mechanism 304 to select more fluid to flow
through one of the passageways 306, 308 than the other passageway.
In some embodiments, the change in velocity profile may result in
fluid oscillate and in an increase differential pressure for the
fluid during flow through the flow path to the switching
mechanism.
[0038] For example, and as shown in FIG. 3, part of the fluid
flowing through the flow path closer to the hydrophobic material
316 than the hydrophilic material 314 may flow at a higher velocity
such that more of the fluid flows through passageway 308 than
passageway 306. Although not depicted in FIG. 3, some fluid may
flow through passageway 306, but at lesser amount than through
passageway 308.
[0039] In FIG. 4, the fluid may have a higher concentration of oil
or other type of hydrocarbon. Part of the fluid flowing proximate
the hydrophobic material 316 may be attracted to the hydrophobic
material 316, and in some cases may accumulate on the hydrophobic
material 316 and change the effective surface roughness of the wall
302 to cause a change in a velocity profile to at least part of the
fluid flowing in the flow path. The change in velocity may be used
by the switching mechanism 304 to select more fluid to flow through
one of the passageways 306, 308 than the other passageway. For
example, and as shown in FIG. 4, part of the fluid flowing through
the flow path closer to the hydrophilic material 314 than the
hydrophobic material 316 may flow at a higher velocity such that
more of the fluid flows through passageway 306 than passageway
308.
[0040] Although FIGS. 3-4 depict hydrophilic material 314 on a side
of the wall 302 corresponding to a radial passageway 306 and
hydrophobic material 316 on a side of the wall corresponding to a
tangential passageway 308, other and opposite configurations are
possible.
[0041] FIG. 5 depicts a cross-section of a portion of a wall 402
that includes a material 404 on an inner region of the wall 402.
The inner region of the wall 402 may be any shape, including
rectangular. The material 404 may be hydrophilic material,
hydrophobic material, or a material capable of being hydrophobic
and/or hydrophilic material in response to stimuli. The material
404 may be sized to provide desired performance in affecting a
velocity profile of fluid flowing through a flow path in the wall
402. In some embodiments, material 404 is on an entire
circumferential portion of the inner region of the wall 402.
[0042] Material 404 may be screen-printed or otherwise overlaid on
the inner region of the wall 402. In some embodiments, material 404
is bonded to the inner region of the wall 402 via an adhesive or
mechanical coupler. In other embodiments, material 404 may be
embedded in the wall 402. For example, part of the inner region of
the wall 402 can be removed and material 404 can be coupled to the
wall 402 in place of the removed portion. Embedding material 404 in
the wall 402 may avoid material 404 extending into the flow path in
the wall 402.
[0043] In other embodiments, material may be included in an inner
region of a wall in a pattern. FIG. 6 depicts a cross-section of
part of a wall 502 that includes hydrophilic material 504 and
hydrophobic material 506 in a pattern. The pattern can include
hydrophilic material 504 adjacent to the hydrophobic material 506.
More complex patterns than is shown in FIG. 6 can be used. For
example, hydrophobic material and hydrophilic material may be
alternately positioned adjacent to each other.
[0044] FIG. 7 shows a flow control device according to another
embodiment. Similar to the embodiment in FIGS. 3-4, the flow
control device includes a wall 602 and a switching mechanism 604
providing a flow path to two passageways 606, 608 that allow fluid
to flow to a vortex assembly 610 at a radial angle (passageway 606)
or a tangential angle (passageway 608). Fluid flowing into the
vortex assembly 610 via passageway 606 may be guided to an exit
opening 612 in the vortex assembly 610. Fluid flowing into the
vortex assembly 610 via passageway 608 may be guided into a vortex
about the exit opening 612 and restricted, at least partially and
for at least a certain amount of time, from exiting through the
exit opening 612.
[0045] The flow control device includes material 614 on a portion
of an inner region of wall 602 that is antecedent to the switching
mechanism 604. The material 614 may be capable of responding to
stimuli by changing to a hydrophilic material and/or a hydrophobic
material. A stimuli source 616 is positioned on an opposite side of
the wall 602 to the material 614. A control line 618 is coupled to
the stimuli source 616. The control line 618 may provide
communication to a surface of a wellbore, or the control line 618
may be coupled to another component capable of providing control
signals to the stimuli source 616.
[0046] The stimuli source 616 in FIG. 7 may be a light source
capable of providing light at a certain frequency to cause material
614 to change to a hydrophilic or hydrophobic material. The light
source can be controlled via control line 618. The light source can
be powered via a local power source (e.g. a battery or power
generator) or via power delivered over control line 618. A signal
can be carried to the light source to cause the light source to
emit light at a selected frequency (e.g. red or blue). In response
to being exposed to the light, the material 614 can change to a
hydrophobic material or a hydrophilic material, as may be
configured, and affect fluid flowing through a flow path of the
wall 602. The material 614 may be configured to remain as a
hydrophobic material or a hydrophilic material for a certain amount
of time after being exposed to the light, until the light source
exposes the material 614 to light having a different frequency, or
permanently.
[0047] In other embodiments, the light source is positioned on the
same side of the wall 602 as the material 614. For example, the
light source may be embedded in the wall 602, but behind the
material 614.
[0048] Stimuli sources according to other embodiments may provide
stimuli that is different than light. For example, a stimuli source
may controllably provide stimuli that include voltage or a chemical
to material. The material may be configured to respond to a certain
chemical or electric energy, such as a certain voltage, to change
to a hydrophobic material or a hydrophilic material.
[0049] Stimuli sources according to some embodiments may also
measure fluid that may accumulate on the stimuli sources. Based on
properties measured from the fluid, a stimuli source may output a
certain stimuli to cause material to change to a hydrophobic
material or a hydrophilic material.
[0050] The foregoing description of the embodiments, including
illustrated embodiments, of the invention has been presented only
for the purpose of illustration and description and is not intended
to be exhaustive or to limit the invention to the precise forms
disclosed. Numerous modifications, adaptations, and uses thereof
will be apparent to those skilled in the art without departing from
the scope of this invention.
* * * * *