U.S. patent application number 16/139756 was filed with the patent office on 2020-08-13 for thin profile user interface device and method providing localized haptic response.
The applicant listed for this patent is Novasentis, Inc.. Invention is credited to Stephen Davis, Li Jiang, Christophe Ramstein, Brian C. Zellers.
Application Number | 20200257363 16/139756 |
Document ID | 20200257363 / US20200257363 |
Family ID | 1000004986778 |
Filed Date | 2020-08-13 |
Patent Application | download [pdf] |
United States Patent
Application |
20200257363 |
Kind Code |
A9 |
Zellers; Brian C. ; et
al. |
August 13, 2020 |
THIN PROFILE USER INTERFACE DEVICE AND METHOD PROVIDING LOCALIZED
HAPTIC RESPONSE
Abstract
Electromechanical polymer (EMP) actuators are used to create
haptic effects on a user interface deface, such as a keyboard. The
keys of the keyboard may be embossed in a top layer to provide
better key definition and to house the EMP actuator. Specifically,
an EMP actuator is housed inside an embossed graphic layer that
covers a key of the keyboard. Such a keyboard has a significant
user interface value. For example, the embossed key provides the
tactile effect of the presence of a key with edges, while allowing
for the localized control of haptic vibrations. For such
applications, an EMP transducer provides high strains, vibrations
or both under control of an electric field. Furthermore, the EMP
transducer can generate strong vibrations. When the frequency of
the vibrations falls within the acoustic range, the EMP transducer
can generate audible sound, thereby functioning as an audio
speaker.
Inventors: |
Zellers; Brian C.;
(Bellefonte, PA) ; Jiang; Li; (Union City, CA)
; Ramstein; Christophe; (San Francisco, CA) ;
Davis; Stephen; (State College, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Novasentis, Inc. |
Burlingame |
CA |
US |
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Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20190025925 A1 |
January 24, 2019 |
|
|
Family ID: |
1000004986778 |
Appl. No.: |
16/139756 |
Filed: |
September 24, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13735804 |
Jan 7, 2013 |
10088936 |
|
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16139756 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G06F 3/016 20130101;
G06F 3/0414 20130101; H01L 41/193 20130101; G06F 3/0202
20130101 |
International
Class: |
G06F 3/01 20060101
G06F003/01; G06F 3/02 20060101 G06F003/02; G06F 3/041 20060101
G06F003/041 |
Claims
1. A two-sided keyboard comprising a first surface and a second
surface on opposite sides of the two-sided keyboard, wherein each
of said first and second surfaces include: a force-sensing layer
including one or more force-sensing sensors; one or more
electromechanical polymer (EMP) transducers to provide a localized
haptic response to a force detected by the force-sensing layer; and
a covering layer covering the force-sensing layer and the EMP
transducers, wherein the EMP transducers are directly attached to
an underside of the covering layer such that the localized haptic
response is transmitted to the covering layer without going through
an intervening passive layer.
2. The two-sided keyboard of claim 1, wherein each of said first
and second surfaces include a cushion attached to each EMP
transducer between the EMP transducer and a corresponding one of
the force-sensing sensors to which the EMP transducer is aligned,
wherein the cushion has a hardness between 20 A-30 A.
3. The two-sided keyboard of claim 1, wherein the force-sensing
sensors comprise a force-sensing resistor material.
4. The two-sided keyboard of claim 1, further comprising a spacer
layer provided between the covering layer and the force-sensing
layer, wherein the spacer layer has one or more cavities each
aligned with one of the force-sensing sensors, so as to accommodate
a corresponding one of the EMP transducers.
5. The two-sided keyboard of claim 1, wherein between the one or
more EMP transducers and the force-sensing layer is provided an air
gap.
6. The two-sided keyboard of claim 1, wherein each of the first
surface and the second surface can be used independently as an
input device.
7. The two-sided keyboard of claim 1, wherein the two-sided
keyboard is attached to a tablet computer.
8. The two-sided keyboard of claim 7, wherein the both of the first
surface and the second surface are used simultaneously for input to
the tablet computer.
9. The two-sided keyboard of claim 7, wherein the first surface and
the second surface are used to cover the tablet computer.
10. The two-sided keyboard of claim 7, wherein tablet computer has
a display and wherein the first surface faces the display, and the
second surface faces away from the display, and wherein the second
surface can be used to provide input to the tablet computer.
11. A portable computing device comprising: a tablet computer
having a first side, a second side, and a controller; and a
two-sided keyboard having a first surface and a second surface
provided to cover the second side of the tablet computer, the
two-sided keyboard having (i) a first configuration wherein, the
first surface of the two-sided keyboard is opened up for data
input, and (ii) a second configuration wherein the two-sided
keyboard rests flat against the second side of the tablet computer
and provides the second surface of the two-sided keyboard for data
input, wherein each surface of the two-sided keyboard comprises: a
force-sensing layer including one or more force-sensing sensors;
one or more electromechanical polymer (EMP) transducers to provide
a localized haptic response to a force detected by the
force-sensing layer; a covering layer covering the force-sensing
layer and the EMP transducers, wherein the EMP transducers are
directly attached to an underside of the covering layer such that
the localized haptic response is transmitted to the covering layer
without going through an intervening passive layer.
12. The portable computing device of claim 11, wherein each of said
first and second surfaces of the two-sided keyboard include a
cushion attached to each EMP transducer between the EMP transducer
and a corresponding one of the force-sensing sensors to which the
EMP transducer is aligned, wherein the cushion has a hardness
between 20 A-30 A.
13. The two-sided keyboard of claim 11, wherein the force-sensing
sensors comprise a force-sensing resistor material.
14. The portable computing device of claim 11, wherein the
two-sided keyboard further comprising a spacer layer provided
between the covering layer and the force-sensing layer, wherein the
spacer layer has one or more cavities each aligned with one of the
force-sensing sensors, so as to accommodate a corresponding one of
the EMP transducers.
15. The portable computing device of claim 11, wherein between the
one or more EMP transducers and the force-sensing layer is provided
an air gap.
16. The portable computing device of claim 11, wherein the both of
the first surface and the second surface are used simultaneously
for input to the tablet computer.
17. The portable computing device of claim 11, further comprising a
protective covering provided to cover the first side of the tablet
computer, wherein the protective covering is configured to be
folded to serve as a stand for propping up the tablet computer, and
wherein only the first surface of the two-sided keyboard is used
for input to the tablet computer.
18. A two-sided keyboard, the two-sided keyboard comprising: a
first surface comprising: a first force-sensing layer including one
or more force-sensing sensors; a first set of electromechanical
polymer (EMP) transducers to provide a localized haptic response to
a force detected by the force-sensing layer; and a covering layer
covering the first force-sensing layer and the first set of EMP
transducers; and a second surface on a side opposite of the first
surface, the second surface comprising: a second force-sensing
layer including one or more force-sensing sensors; and a second set
of electromechanical polymer (EMP) transducers to provide a
localized haptic response to a force detected by the force-sensing
layer.
19. The two-sided keyboard of claim 18, wherein each of said first
and second surfaces include a cushion with a hardness between 20
A-30 A.
20. The two-sided keyboard of claim 18, wherein the both of the
first surface and the second surface are used simultaneously for
input to the tablet computer.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation application of U.S.
Non-Provisional application Ser. No. 13/735,804 filed Jan. 7, 2013,
entitled "Thin Profile User Interface Device and Method Providing
Localized Haptic Response," and PCT Application Serial No.
PCT/US13/71062 filed Feb. 12, 2014, which are incorporated herein
by reference in their entirety for all purposes.
[0002] The present patent application is related to U.S.
Provisional Patent Application ("Copending Provisional
Application"), Ser. No. 61/679,641, filed Aug. 3, 2012, entitled
"Electromechanical Polymer Actuators for Haptic Feedback," and U.S.
Patent Applications ("Copending Applications") (i) Ser. No.
13/683,980, entitled "Haptic System with Localized Response," filed
Nov. 21, 2012, and (ii) Ser. No. 13/683,928, entitled "EMP
Actuators for Deformable Surface and Keyboard Application," also
filed on Nov. 21, 2012. The disclosures of the Copending
Provisional Application and the Copending Applications are hereby
incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0003] The present invention relates to using transducers based on
electromechanical polymers (EMP) layers; in particular, the present
invention relates to use of such transducers to provide haptic
response in keys of a thin profile keyboard.
2. Discussion of the Related Art
[0004] Transducers are devices that transform one form of energy to
another form of energy. For example, a piezoelectric transducer
transforms mechanical pressure into an electrical voltage. Thus, a
user may use the piezoelectric transducer as a sensor of the
mechanical pressure by measuring the output electrical voltage.
Alternatively, some smart materials (e.g., piezoceramics and
dielectric elastomers (DEAP)) deform proportionally in response to
an electric field. An actuator may therefore be formed out of a
transducer based on such a smart material. Actuation devices based
on these smart materials do not require conventional gears, motors,
and cables to enable precise articulation and control. These
materials also have the advantage of being able to exactly
replicate both the frequency and the magnitude of the input
waveform in the output response, with switching time in the
millisecond range.
[0005] For a smart material that has an elastic modulus Y,
thickness t, width w, and electromechanical response (strain in
plane direction) S.sub.1, the output vibration energy UV is given
by the equation:
UV=1/2YtwS.sub.1.sup.2 (1)
[0006] DEAP elastomers are generally soft, having elastic moduli of
about 1 MPa. Thus, a freestanding, high-quality DEAP film that is
20 micrometers (.mu.m) thick or less is difficult to make. Also, a
DEAP film provides a reasonable electromechanical response only
when an electric field of 50 MV/m (V/.mu.m) or greater is applied.
Thus, a DEAP type actuator typically requires a driving voltage of
1,000 volts or more. Similarly, a DEAP type sensor typically
requires a charging voltage of 1,000 volts or more. In a handheld
consumer electronic device, whether as a sensor or as an actuator,
such a high voltage poses safety and cost concerns. Furthermore, a
DEAP elastomer has a low elastic modulus. As a result, to achieve
the strong electrical signal output needed for a handheld device
application requires too thick a film. The article, "Combined
Driving Sensing Circuitry for Dielectric Elastomer Actuators in
Mobile Applications," by M. Matsek et al., published in
Electroactive Polymer Actuators and Devices (EAPAD) 2011, Proc. Of
SPIE vol. 7975, 797612, discloses providing sensor functions in
dielectric elastomer stack actuators (DESA). U.S. Pat. No.
8,222,799 to Polyakov, entitled "Surface Deformation Electroactive
Polymer Transducers," also discloses sensor functions in dielectric
elastomers.
[0007] Unlike a DEAP elastomer, a piezoceramic material can provide
the required force output under low electric voltage. Piezoelectric
materials are crystalline materials that become electrically
charged under mechanical stress. Converse to the piezoelectric
effect is dimensional change as a result of imposition of an
electric field. In certain piezoelectric materials, such as lead
zirconate titanate (PZT), the electric field-induced dimensional
change can be up to 0.1%. Such piezoelectric effect occurs only in
certain crystalline materials having a special type of crystal
symmetry. For example, of the thirty-two classes of crystals,
twenty-one classes are non-centrosymmetric (i.e., not having a
center of symmetry), and of these twenty-one classes, twenty
classes exhibit direct piezoelectricity. Examples of piezoelectric
materials include quartz, certain ceramic materials, biological
matter such as bone, DNA and various proteins, polymers such as
polyvinylidene fluoride (PVDF) and polyvinylidene
fluoride-co-trifluoroethylene [P(VDF-TrFE)]. For further
information, see, for example, the article "Piezoelectric
Transducer Materials", by H. JAFFE and D. A. BERLINCOURT, published
on pages 1372-1386 of PROCEEDINGS OF THE IEEE, VOL. 53, No. 10,
OCTOBER, 1965.
[0008] The strain of a piezoelectric device is linearly
proportional to the applied electric field E:
S.sub.1.noteq.E (2)
[0009] As illustrated in equation (2), when used in an actuator
device, a piezoelectric material generates a negative strain (i.e.,
shortens) under a negative polarity electric field, and a positive
strain (i.e., elongates) under a positive electric field. However,
piezoceramic materials are generally too brittle to withstand a
shock load, such as that encountered when the device is
dropped.
[0010] Piezoceramics and dielectric elastomers change capacitance
in response to a mechanical deformation, and thus may be used as
pressure sensors. However, as mentioned above, DEAP elastomers are
generally soft, having elastic moduli of about 1 MPa. Thus, a
freestanding, high-quality DEAP film that is 20 micrometers (.mu.m)
thick or less is difficult to make.
[0011] Unlike the piezoelectric materials that require a special
type of crystal symmetry, some materials exhibit electrostrictive
behavior, such as found in both amorphous (non-crystalline) and
crystalline materials. "Electrostrictive" or "electrostrictor"
refers to a strain behavior of a material under an electric field
that is quadratically proportional to the electric field, as
defined in equation (3)
S.sub.1.about.E.sup.2 (3)
[0012] Therefore, in contrast to a piezoelectric material, an
electrostrictive actuator always generates positive strain, even
under a negative polarity electric field (i.e., the
electrostrictive actuator only elongates in the direction
perpendicular to the imposed field), with an amplitude that is
determined by the magnitude of the electric field and regardless of
the polarity of the electric field. A description of some
electrostrictive materials and their behavior may be found, for
example, in the articles (a) "Giant Electrostriction and relaxor
ferroelectric behavior in electron-irradiated poly(vinylidene
fluoride-trifluoroethylene) copolymer", by Q. M. Zhang, et al,
published in Science 280:2101 (1998); (b) "High electromechanical
responses in terpolymer of poly(vinylidene
fluoride-trifluoroethylene-chlorofluoroethylene)", by F. Xia et al,
published in Advanced Materials, 14:1574 (2002). These materials
are based on electromechanical polymers. Some further examples of
EMPs are described, for example, in U.S. Pat. Nos. 6,423,412,
6,605,246, and 6,787,238. Other examples include the EMPs whose
compositions disclosed in pending U.S. patent application Ser. No.
13/384,196, filed on Jul. 15, 2009, and the EMPs which are blends
of the P(VDF-TrFE) copolymer with the EMPs disclosed in the
aforementioned U.S. Patents.
[0013] To achieve a substantially linear response and mechanical
strains of, say, up to four (4) percent, in a longitudinal or
transverse direction, the electrorestrictive EMPs discussed above
requires an electric field intensity between 50 to 100 MV/m. In the
prior art, to provide adequate mechanical strength and flexibility,
the polymer films are at least 20 .mu.m thick. As a result, an
actuator based on such an electrostrictive EMP requires an input
voltage of about 2000 volts. Such a voltage is typically not
available in a mobile device.
[0014] Polyvinylidene difluoride (PVDF) and
poly[(vinylidenefluoride-co-trifluoroethylene (P(VDF-TrFE)) are
well-known ferroelectric sensor materials. However, these materials
suffer from low strain, and thus perform poorly for many
applications, such as keys on a keyboard.
[0015] FIG. 1 illustrates the basics of an exemplary EMP actuator
100 creating mechanical motion in response to an electrical
stimulation. As shown in FIG. 1, EMP actuator 100 includes EMP
layer 102, which may be itself consists of a number of EMP layers,
is bonded to substrate 103. Substrate layer 103 is made of a thin,
flexible material that is not compliant the longitudinal direction.
During a quiescent state, i.e., without an electrical potential
imposed across EMP layer 102, EMP actuator 100 is unstressed (FIG.
1a). When a DC electrical potential (i.e., 0 Hz) is imposed across
EMP layer 102, EMP layer 102 elongates. As substrate 102 is not
sensitive to the electrical potential, a large mechanical stress
causes EMP actuator 100 to buckle, as shown in FIG. 1(b). With a
non-zero driving frequency, vibrations may be created at different
frequencies.
[0016] One area that EMPs find application is haptics. In this
context, the term "haptics" refers to tactile user input actions.
In a conventional keyboard, the mechanical, spring-loaded action of
a pressed key and the associated audio "click" are haptic responses
to the touch typist that a key has been successfully depressed.
Similarly, a haptics-enabled touch screen may generate an immediate
haptic feedback vibration when the key is activated by user input.
The feedback vibration makes the virtual element displayed on the
touch screen more physical and more realistic. In a portable device
(e.g., a mobile telephone), a haptic feedback action can reduce
both user input errors and stress, allow a higher input speed, and
enable new forms of bi-directionally interactions, Haptics is
particularly effective for keyboards that are used in noisy or
visually distracting environments (e.g., a battlefield or a gaming
environment). Haptics can reduce input error rates and improve
response speed.
[0017] Recently proposed high-definition (HD) haptics may provide
significantly more tactile information to a user, such as texture,
speed, weight, hardness, and damping. HD haptics uses frequencies
that may be varied between 50 Hz to 400 Hz to convey complex
information, and to provide a richer, more useful and more accurate
haptic response. Over this frequency range, a user can distinguish
feedback forces of different frequencies and amplitudes. The
feedback vibration is expected to be controlled by software. For a
user to experience a strong feedback sensation, HD haptics in this
frequency range, switching times (i.e., rise and fall time) between
frequencies of 40 milliseconds (ms) or less are required. The
ability to provide such HD feedback vibrations in the 50 Hz to 400
Hz band, however, is not currently available. In the prior art, a
typical device having basic haptics has an output magnitude that
varies with the frequency of the driving signal. Specifically, the
typical device provides a greater output magnitude at a higher
frequency from the same input driving amplitude. For example, if a
haptic driving signal includes two equal-magnitude sine waves at
two distinct frequencies, the output vibration would be a
superposition of two sine waves of different magnitudes, with the
magnitudes being directly proportional to the respective
frequencies. Such a haptic response is not satisfactory. Therefore,
a compact, low-cost, low-driving voltage, and robust HD haptics
actuation device is needed.
[0018] Haptic responses need not be limited to 50 Hz to 400 Hz
vibrations. At lower frequency, a mechanical pressure response may
be appropriate. Vibrations in the acoustic range can be made
audible. A haptic response that can be delivered in more than one
mode of sensation (e.g., mechanical pressure, vibration, or audible
sound) is termed "multimodal."
[0019] Recently, the consumer electronics industry has been
demanding very thin profile keyboards (e.g., 2-3 mm thick). For
example, Microsoft Corporation introduced for its Surface tablet
computer a keyboard which also serve as a protective cover of the
tablet computer. FIG. 2 shows a side view of prior art thin profile
keyboard 200. As shown in FIG. 2, keyboard 200 includes substrate
or base layer 201, force-sensing resistor (FSR) layer 202 and cover
layer 203. Base layer 201 provides protection and mechanical
support for keyboard 200. FSR layer 202 is a sensing layer which is
made of a material which resistance changes with an applied
mechanical force on its surface (e.g., the pressure applied by a
human finger, as illustrated in FIG. 2). Cover layer 203 provides
protection to FSR layer 202. Cover layer 203 is thus made of a
durable material. In addition, as the force of the user's finger is
transmitted by cover layer 203 to FSR layer 202, cover layer 203 is
made of a flexible material. Typically, base layer 201 is the most
rigid layer of keyboard 200. However, without haptic feedback, such
thin profile keyboards are not satisfactory to most users.
SUMMARY OF THE INVENTION
[0020] According to one embodiment of the present invention,
electromechanical polymer (EMP) actuators are used to create haptic
effects on a mobile device's mechanical interfaces (e.g., keys of a
keyboard). In some embodiments, the keys of the keyboard are
embossed in a top layer to provide better key definition and to
house the EMP actuator. Specifically, an EMP actuator is housed
inside an embossed graphic layer that covers a key of the keyboard.
The present invention is of significant user interface value. For
example, the embossed key provides the tactile effect of the
presence of a key with edges, while allowing for the localized
control of haptic vibrations. For such applications, an EMP
transducer provides high strains, vibrations or both under control
of an electric field. Furthermore, the EMP transducer can generate
strong vibrations. When the frequency of the vibrations falls
within the acoustic range, the EMP transducer can generate audible
sound, thereby functioning as an audio speaker. Thus, the EMP
actuator of the present invention can provide a multimodal haptic
response (e.g., generating deformable surface, vibration, or
audible sound, as appropriate). In addition, the EMP transducer can
also serve as a touch sensor, as a mechanical pressure applied on
the EMP transducer can induce a measurable electrical voltage
output. Therefore, the EMP transducer may serve as both a sensor
and an actuator.
[0021] The EMP layer is charged by the excitation signal. The
excitation signal may have a frequency in a frequency range within
the human acoustic range. In response to the excitation signal, the
associated EMP actuator vibrates at substantially the frequency of
the excitation signal. The frequency range may be between 0 Hz
(i.e., DC) to 10,000 Hz, depending on the EMP actuator's
application. When the EMP actuator is used to provide a haptic
feedback, the frequency may be in the range of 50 Hz to 400 Hz; and
when the EMP actuator is used to provide certain acoustic
functions, the frequency can be in the range of 400 Hz to 10,000
Hz. The vibration of the EMP actuator may provide an audible sound.
The EMP actuator disclosed herein may have a response latency
relative to the excitation signal of less than 40 milliseconds. In
addition, the EMP actuator may have a decay time of less than 40
milliseconds. The EMP layer may have an elastic modulus greater
than 500 MPa at 25.degree. C. and an electromechanical strain
greater than 1%, when experiencing an electric field of greater
than 100 MV/m.
[0022] Unlike current haptics system which typically vibrates the
entire electrical device, which is often rigid, the EMP
actuator-enabled haptics can vibrate directly under the point of
contact (e.g., a user's finger). In one embodiment, an array or
grid of EMP actuators are provided, in which only the actuator
under the touch is selectively activated, thereby providing a
"localized" haptics feedback. When the EMP actuators are arranged
in sufficiently close vicinity of each other, the haptic system may
take advantage of haptic responses that are superimposed for
constructive interference. In some embodiments, the substrate may
vibrate in concert with the EMP actuators.
[0023] When a specific key is pressed by a user, an excitation
signal may be provided to cause the associated EMP actuator to
vibrate, so as to confirm to the user that the user's typing action
has been detected.
[0024] According to one embodiment of the present invention, the
EMP actuator of the haptic system may be activated by a high
frequency signal having one or more frequency components in the
range of 400 Hz to 10,000 Hz. The high frequency vibration of the
EMP actuator (or the EMP actuator together with the substrate) can
generate an audible acoustic signal as a feedback response.
[0025] The present invention is better understood upon
consideration of the detailed description below in conjunction with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 illustrates the basics of an EMP actuator creating
mechanical motion in response to an electrical stimulation.
[0027] FIG. 2 shows a side view of prior art thin profile keyboard
200.
[0028] FIG. 3 shows a side view of keyboard 300 having an
electromechanical polymer (EMP) actuator included with each key or
surface, in accordance with one embodiment of the present
invention.
[0029] FIG. 4 shows some examples of the shapes of EMP actuators
(e.g., EMP actuators 310) may be made into, as seen from above.
[0030] FIG. 5 shows EMP actuator 500, having a shape that is
suitable for use in keys and surfaces.
[0031] FIG. 6 shows some exemplary cushion shapes, in accordance
with one embodiment of the present invention.
[0032] FIG. 7 shows schematically embossed key 700 of a keyboard in
which EMP actuator 701 is attached to the embossed area 702 of
cover layer 705, in accordance with one embodiment of the present
invention.
[0033] FIG. 8 shows four types of standoffs that can be used in
conjunction with embossed key 700.
[0034] FIG. 9(a) shows embossed key 900, according to another
embodiment of the present invention.
[0035] FIG. 9(b) shows embossed key 920, according to another
embodiment of the present invention.
[0036] FIGS. 10(a), (b) and (c) show different configurations of
mobile computer 1000, which includes 2-sided keyboard 1002 and
cover/stand 1003, in accordance with one embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0037] According to one embodiment of the present invention, haptic
feedback response is provided in a mechanical interface, such as a
thin profile keyboard, using electromechanical polymer (EMP)
actuators. Throughout this detailed description, keys on a keyboard
are used to illustrate the present invention without an intention
to so limit. In fact, the present invention is applicable to other
mechanical interfaces at which a localized haptic response is
desired.
[0038] FIG. 3 shows a side view of keyboard 300 having an EMP
actuator included with each key or surface, in accordance with one
embodiment of the present invention. As shown in FIG. 3, keyboard
300 includes base layer 301, force-sensing resistor (FSR) layer
302, spacer layer 304, including a number of cavities for
accommodating numerous EMP actuators 310, and cover layer 305. EMP
actuators 310 are attached to cover layer 305 and are each
separated from FSR layer 302 by a cushion 303. Base layer 301 and
FSR layer 302 perform like functions as base layer 201 and FSR
layer 202 of FIG. 2. Specifically, base layer 301 provides
protection and mechanical support for keyboard 300. FSR layer 302
is the sensing layer and is made of a material which resistance
changes with an applied mechanical force on its surface (e.g., the
pressure applied by a human finger, as illustrated in FIG. 3). EMP
actuators 310 are each aligned vertically with an active sensing
area of FSR layer 302 ("FSR sensor"). The portions of FSR layer 302
outside of the FSR sensors are inactive areas where support
structures and wiring are provided. Spacer layer 304, having a
thickness in the range of 0.2 mm to 0.5 mm, for example, is
provided above the inactive areas of FSR layer 302. Cover layer
305, which is preferably made of a durable, flexible material,
protects FSR layer 302 and transmits any force impressed, for
example, by a user's finger, to FSR layer 302. When a user touches
a key, the pressure of the touch is transmitted to the
corresponding FSR sensor, which provides an electrical signal to a
controller. In response, the controller activates the corresponding
EMP actuator to provide a haptic feedback response.
[0039] As EMP actuators 310 are made from a polymer material, each
of EMP actuators 310 may be made into any suitable shape. FIG. 4
shows some examples of the shapes EMP actuators 310 may be made
into, as seen from above. In particular, FIG. 5 shows EMP actuator
500, which has a shape that is suitable for use in keys and
surfaces. As shown in FIG. 5, EMP actuator 500 has a footprint that
is, for example, 14 mm by 14 mm, including a 14 mm by 12 mm active
area. An exemplary capacitance for EMP actuator 500 may be about
250 nanofarad of capacitance. As EMP actuators 310 are attached to
the back side of cover layer 305, cover layer 305 together with the
EMP actuators 310 create a vibration structure. That is, an
additional passive layer (e.g., substrate layer 103 of FIG. 1) is
not necessary for creating a vibration structure. When an EMP
actuator is actuated, its vibration is transmitted through cover
layer 305 to provide the haptic feedback to the user.
[0040] As seen from FIG. 3, cushion 303 is provided between each of
EMP actuators 310 and the corresponding FSR sensor. The thickness
of the cushions are specifically designed to be slightly less than
the distance between the EMP actuator on which it is attached and
the corresponding active area of FSR layer 302, so as to avoid
imposing a force on the FSR sensor when there is no force on the
corresponding area of cover layer 305. The cushion reduces
attenuation of the haptic feedback when a user pushes hard on a
key. A properly designed cushion reduces the attenuation of the
haptic feedback response. FIG. 6 shows some exemplary cushion
shapes, in accordance with one embodiment of the present invention.
As shown in FIG. 6, examples (a)-(b) are in the forms of circular
or rectangular cylinders with an annular 1 mm thick cross sections,
and example (c) has four posts each with a rectangular cross
section of about 1 mm in width or breadth. Each cushion may
preferably have a hardness between 20 A to 30 A. The internal
diameter of example (a) is preferably roughly 10 mm.
[0041] According to one embodiment of the present invention, the
EMP actuator is attached to a raised or embossed area of the cover
layer. Such an embossing structure may increase the strength of the
haptic feedback by an EMP actuator. FIG. 7 shows schematically
embossed key 700 of a keyboard in which EMP transducer 701 is
attached to the embossed area 702 of cover layer 705, in accordance
with one embodiment of the present invention. As shown in FIG. 7,
embossed key 700 includes EMP transducer 701, which is attached to
embossed area 702, standoff or cushion 703, and FSR sensor 706
embedded in mechanical ground 704. In FIG. 7, mechanical ground 704
embeds FSR sensor 706; however, other thin film type sensors
underneath standoffs. Cushion 703 may have any of the forms shown
in FIG. 8 (i.e., annular with a circular cross section, in two
parallel strips, in four cubes, annular with a rectangular cross
section) or may be provided as a solid piece. Alternatively, EMP
transducer 701 may serve as both an actuator and an
electromechanical sensor. Standoff or cushion 703 limits the
distance of mechanical travel between EMP transducer 701 and
mechanical ground 704 when embossed key 700 is loaded by a user's
finger. The thickness (t) of standoff 703 determines the distance
of mechanical travel experienced by embossed key 700 when loaded by
a user's finger. Therefore, the thickness allows for tuning of the
mechanical travel. Furthermore, when the user presses on embossed
key 700, standoff 703 captures the pressure on EMP transducer 701,
such that the haptic vibration is not significantly damped. The
height of the embossing may be around 0.20.4 mm, for example.
[0042] The haptic response can be isolated to the embossed
structure (i.e., embossed key 700) only, thus enforcing the ability
to provide a localized haptics response to only the key of
interest. In this way, haptic vibrations occurring at a key of
interest are not felt at a neighboring key. Thus, embossed key 700
has the advantage of incorporating both the kinesthetic presence of
a geometrically defined key, as well as providing a haptic
vibration response, without unduly adding to the thickness of the
key. FIG. 8 shows four types of standoffs that can be used in
embossed key 700. Standoff 703 transfers force from the embossing
structure to the thin film force sensor, and does not significantly
attenuate vibration from the EMP sensor. EMP transducer 701 may
vibrate at different frequencies or at different amplitudes under
different conditions.
[0043] An embossed key is much more clearly defined to the user,
facilitating the user's determination of the exact location of the
key with his/her tactile feeling. In addition, the haptic feedback
response (e.g., vibration) is much stronger in the embossed
structure.
[0044] FIG. 9(a) shows embossed key 900, according to another
embodiment of the present invention. As shown in FIG. 9(a), EMP
actuator 905 is attached to an underside of an embossed area 907 of
cover layer 901 of embossed key 900 in a thin profile keyboard. EMP
actuator 902 is separated by cushion 904 from FSR sensor 905 which
is embedded in a FSR layer provided above substrate or base 903.
Alternatively, as shown in FIG. 9(b), some embodiments need not
include a physical cushion structure underneath the EMP layer.
Thus, FIG. 9(b) shows embossed key 920, according to another
embodiment of the present invention. As shown in FIG. 9(b), EMP
actuator 925 is attached to an underside of an embossed area 907 of
cover layer 921 of embossed key 920 in a thin profile keyboard.
Rather than by a cushion, EMP actuator 925 is separated by air gap
or space 924 from FSR sensor 922, which is embedded in a FSR layer
provided above substrate or base 923. In still other embodiments,
neither cushion 904 nor space 924 is provided, i.e., the EMP
actuator of the EMP actuator directly contacts an FSR sensor. Such
an embodiment may provide a keyboard of even thinner profile.
[0045] Because of their thin profiles, the keyboards of the present
invention may be used with many types of mobile devices, such as
tablet computers. Such a keyboard may be used for other functions
also (e.g., protective covering). FIGS. 10(a), (b) and (c) show
different configurations of mobile computer 1000, which includes
2-sided keyboard 1002, in accordance with one embodiment of the
present invention. As shown in these figures, mobile computer 1000
includes tablet device 1001, 2-sided keyboard 1002 and protective
cover 1003. Protective layer 1003 and 2-sided keyboard 1002 are
attached along one side of table device 1001. Protective cover 1003
may be folded in such a way to serve as a stand to prop up tablet
device 1001 in the manner shown in FIGS. 10(a) and 10(b). In these
configurations, protective cover 1003 serves as a stand for tablet
device 1001. To serve in this function, protective cover 1003 may
be provided a crease or is hinged to allow it to be folded into a
stand. 2-sided keyboard 1002 is a thin pad that has keys of the
present invention provided on both sides, such that each side can
be used by itself as an independent keyboard. In the configurations
of FIGS. 10(a) and 10(b), the user can view the entire surface of
tablet device 1001 at a favorable angle. Either side of 2-sided
keyboard 1002 may be used for input purpose. In FIG. 10(c),
protective cover 1003 is configured to lay flat against tablet
device 1001 to provide protection on the back side, while 2-sided
keyboard 1002 is rests flat against a lower half surface of tablet
device 1001. In this configuration, a portion of tablet device 1001
is covered by 2-sided keyboard 1002. However, mobile computer 1000
may be used in the conventional tablet fashion, allowing data input
to be made through the keys of 2-sided keyboard 1002 on the side
facing away from the display surface of tablet device 1001.
[0046] The electromechanical polymer (EMP) transducers suitable for
the present invention disclosed herein are numerous, including
ferroelectric, dielectric elastomer, piezoelectric and
electro-restrictive materials.
[0047] Some examples of the electromechanically active polymers
incorporated in the EMP transducers of the present invention
include P(VDF-TrFE) modified by either high energy density electron
irradiation or by copolymerization with a third monomer. Under such
a modification, the EMP loses its piezoelectric and ferroelectric
behaviors and become an "electrostrictive" or "relaxor
ferroelectric" material.
[0048] An electromechanical polymer (EMP) transducer typically
includes a large number of EMP active layers (e.g., 1-1000 or more
layers) and electrodes bonded to each layer thereto. The EMP active
layers may be configured as a stack, bonded to each other by an
adhesive or by thermal lamination, for example, to achieve a
cumulative force effect. The electrodes may be arranged to connect
multiple active layers in parallel. With the EMP active layer each
being less than 10 microns thick, the EMP actuators may be actuated
at a low driving voltage (e.g., 300 volts or less; preferably, 150
volts or less) suitable to be powered by a wide variety of consumer
electronic devices, such as mobile telephones, laptops, ultrabooks,
and tablets.
[0049] EMP layers of a EMP transducers used in the present
invention may be preprocessed (e.g., uniaxially or biaxially
stretched, conventionally or otherwise, or having electrodes formed
thereon) to condition the EMP layer's electromechanical response to
an applied external field. A biaxially stretched actuator can
deform in all directions in the plane of the axes of stretching.
When the FSR layer of a key signals that the key is pressed by a
user, an excitation signal is provided by the keyboard controller
to cause the associated EMP actuator to vibrate, as a haptics
response to confirm to the user that the user's typing action has
been detected.
[0050] The electrodes of any EMP transducers discussed herein may
be formed using any suitable electrically conductive materials,
such as transparent conducting materials (e.g., indium tin oxide
(ITO) or transparent conducting composites, such as indium tin
oxide nanoparticles embedded in a polymer matrix). Other suitable
conductive materials include carbon nanotubes, graphenes, and
conducting polymers. The electrodes may also be formed by vacuum
deposition or sputtering using metals and metal alloys (e.g.,
aluminum, silver, gold, or platinum). Nanowires that are not
visible over a graphical display layer may also be used, such as
silver nanowires, copper nanowires, and alloy nanowires with
diameter less than 100 nm.
[0051] The present invention may be used to provide keyboards or
other user interface devices in consumer electronics, which
continue to become smaller and thinner. Low-profile, thin keyboards
are desired for use with many information processing devices (e.g.
tablet computers, ultrabook and MacBook Air). Because the EMP
transducers of the present invention can be made very thin,
according to one embodiment of the present invention, a keyboard
based on EMP transducers may be provided which includes physical
key movements in the manner of a conventional keyboard.
[0052] A haptic response may be provided as confirmation of receipt
of the user's key activation in the user's typing. In this regard,
the EMP actuators may replace the spring mechanism in a classical
keyboard, enabling a low-profile thin keyboard, while still
providing the desirable key travel distance in a conventional
keyboard that a user expects.
[0053] The EMP transducer can also serve as a force or pressure
sensor by itself. Pressing an EMP transducer generates a voltage
across the transducer, which may be used in lieu of a conventional
force transducer (e.g., the FSR sensor). In other words, the EMP
transducer may serve as both the actuator and the sensor without
requiring an additional conventional transducer.
[0054] The EMPs suitable for use in components (e.g., EMP actuators
employed in haptic substrates and haptic devices disclosed herein)
typically show very high strain of about 1% or more under an
electric field gradient of 100 megavolts per meter or greater.
(Strain is measured as the change in length of an EMP layer as a
percentage of the quiescent length.) The EMP layers also may show
elastic modulus of about 500 MPa or more at 25.degree. C., a
mechanical vibrational energy density of 0.1 J/cm.sup.3 or more, a
dielectric loss of about 5% or less, a dielectric constant of about
20 or more, an operating temperature of about -20.degree. C. to
about 50.degree. C., and a response time of less than about 40
millisecond.
[0055] Suitable electrostrictive polymers for EMP layers 140
include irradiated copolymers and semi-crystalline terpolymers,
such as those disclosed in U.S. Pat. Nos. 6,423,412, 6,605,246, and
6,787,238. Suitable irradiated copolymers may include high energy
electron irradiated P(VDF.sub.x-TrFE.sub.1-x copolymers, where the
value of x may vary between 0.5 to 0.75. Other suitable copolymers
may include copolymers of P(VDF.sub.1-x-CTFE.sub.x) or
P(VDF.sub.1-x-HFP.sub.x), where the value of x is in the range
between 0.03 and 0.15 (in molar). Suitable terpolymers that may
have the general form of P(VDF.sub.x-2nd monomer.sub.y-3rd
monomer.sub.1-x-y), where the value of x may be in the range
between 0.5 and 0.75, and the value of y may be in the range
between 0.2 and 0.45. Other suitable terpolymers may include
P(VDF.sub.x-TrFE.sub.y-CFE.sub.1-x-y) (VDF: vinylidene fluoride,
CFE: chlorofluoroethylene, where x and y are monomer content in
molar), P(VDF.sub.x-TrFE.sub.y-CTFE.sub.1-x-y) (CTFE:
chlorotrifluoroethylene), poly(vinylidene
fluoride-trifluoroethylene-vinylidene chloride)(P(VDF-TrFE-VC)),
where x and y are as above; poly(vinylidene
fluoride-tetrafluoroethylene-chlorotrifluoroethylene)(P(VDF-TFE-CTFE)),
poly(vinylidene fluoride-trifluoroethylene-hexafluoropropylene),
poly(vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene),
poly(vinylidene fluoride trifluoroethylene-tetrafluoroethylene),
poly(vinylidene fluoride tetrafluoroethylene tetrafluoroethylene),
poly(vinylidene fluoride-tri fluoroethylene-vinyl fluoride),
poly(vinylideneflouride-tetrafluoroethylene-vinyl fluoride),
poly(vinylidene fluoride-trifluoroethyl eneperfluoro(methyl vinyl
ether)), poly(vinylidene fluoride-tetrafluoroethylene-perfluoro
(methyl vinyl ether)), poly(vinylidene
fluoride-trifluoroethylene-bromotrifluoroethylene, polyvinylidene),
poly(vinylidene fluoride-tetrafluoroethylene-chlorofluoroethylene),
poly(vinylidene fluoride-trifluoroethylene-vinylidene chloride),
and poly(vinylidene fluoride tetrafluoroethylene vinylidene
chloride),
[0056] Furthermore, a suitable EMP may be in the form of a polymer
blend. Examples of polymer blends include of polymer blends of the
terpolymer described above with any other polymers. One example
includes the blend of P(VDF-TrFE-CFE) with P(VDF-TrFE) or blend of
P(VDF-TrFE-CTFE) with P(VDF-TrFE). Other examples of suitable
polymer blends include a blend of P(VDF-TrFE-CFE) with PVDF or a
blend of P(VDF-TrFE-CTFE) with PVDF. Irradiated P(VDF-TrFE) EMP may
be prepared using polymeric material that is itself already a
polymer blend before irradiation.
[0057] According to one embodiment of the present invention, to
form a EMP layer, P (VDF-TrFE-CFE) polymer powder was dissolved in
N, N-dimethylformamide (DMF) solvent at 5 wt. % concentration. The
solution was then filtered and cast onto a glass slide to produce a
30 .mu.m thick film. The film was then uniaxially stretched by 700%
(i.e., the final film length equals to 700% of the cast film
length), resulting in 5 .mu.m thick film. The stretched 5 .mu.m
thick film was further annealed in a forced air oven at 110.degree.
C. for two hours. FIG. 1 shows storage modulus of the resulting
stretched film, as measured using a dynamic mechanical analyzer
(e.g., DMA, TA DMA 2980 instrument) at 1 Hz over a temperature
range of -20.degree. C. to 50.degree. C. The stretched polymer film
may have a storage modulus of 685.2 MPa at 25.degree. C. Thus, an
EMP actuator may be made by casting a layer of EMP polymer (e.g., a
P(VDF-TrFE-CFE) or P(VDF-TrFE-CTFE) terpolymer).
[0058] The stretched EMP film may be metallized by sputtering gold
on both sides of the film. Various voltages were applied to the
resulting EMP actuator and the changes in film length in the
direction parallel to stretching were measured. The stretched EMP
film has strain S.sub.1 of 0.48% at 40 MV/m and 2.1% at 100
MV/m.
[0059] Table 1 shows the performance of actuators made with
modified, P(VDF-TrFE)-based EMP (`EMP"), dielectric elastomer and
piezoceramics.
TABLE-US-00001 Elastomer Piezoceramics Property EMP DEAP (PZT 5H)
Strain (Stretching 2.0% at 100 5-10% at 100 0.1% at 2 Direction)
V/.mu.m V/.mu.m V/.mu.m Young's Modulus (MPa) >500 ~1 ~100,000
Vibration Mechanical >0.1 ~0.005 ~0.05 Energy Density
(J/cm.sup.3) Dielectric Constant 35 3 2500 Dielectric Loss (%) 5 5
2 Minimal Film Thickness 3 18 50 (.mu.m) Voltage for Listed Strain
300 1800 100 Operating Temperature -20.degree. C.~ -20.degree. C.~
-50.degree. C.~ 50.degree. C. 50.degree. C. 100.degree. C. Response
Time (ms) <1 <10 <0.1
[0060] As shown in Table 1, an EMP layer made with modified,
P(VDF-TrFE)-based EMP has balanced electromechanical response and
mechanical modulus. The output vibration mechanical energy density
of such an EMP layer is also significantly higher than the
elastomer DEAP and piezoceramic actuators.
[0061] Each EMP actuator may be actuated independently or in
concert with other EMP actuators. As explained below, the EMP
actuators may excite structural modes of the haptic surface within
a desired haptic frequency band. Also, the EMP actuators may be
arranged to operate as a phased array to focus haptic feedback to a
desired location. In one embodiment, the EMP actuators may be
laminated on a thin glass or plastic substrate that is less than
1,000 .mu.m thick. Such a haptic surface is sufficiently thin to
effectively transmit a haptic event without significantly
attenuating the actuator output. Suitable substrate materials
include transparent materials such as glass, polycarbonate,
polyethylene terephthalate (PET), polymethyl methacrylate,
polyethylene naphthalate (PEN), opaque material such as molded
plastic, or mixtures thereof. Other suitable substrate materials
include multi-component functional sheets such LCD, OLED, PET and
combinations thereof.
[0062] EMP actuators disclosed herein may be actuated by low
driving voltages of less than about 300 volts (e.g., less than
about 150 volts). These driving voltages typically may generate an
electric field of about 40 V/um or more in the EMP layer of the EMP
actuator. The EMP actuators may be driven by a voltage sufficient
to generate an electric field that has a DC offset voltage of
greater than about 10 V/.mu.m, with an alternating component of
peak-to-peak voltage of less than 300 volts. (The excitation signal
need not be single-frequency; in fact, an excitation signal
consisting simultaneously of two or more distinct frequencies may
be provided.) The EMP actuators disclosed herein provide a haptic
vibration of substantially the same frequency of frequencies as the
driving voltage. When the driving voltages are in the audio range
(e.g., up to 40,000 Hz, preferably 400-10000 Hz), audible sounds of
substantially those in the driving frequency or frequencies may be
generated. These EMP actuators are capable of switching between
frequencies within about 40 ms, and are thus suitable for use in HD
haptics and audio speaker applications. The EMP actuators are
flexible and can undergo significant movement to generate high
electrostrictive strains. Typically, a surface deformation
application would use excitation frequencies in the range between
0-50 Hz, a localized haptic application would use excitation
frequencies in the range between 50-400 Hz, and an audio
application would use excitation frequencies in the range between
400-10,000 Hz, for example.
[0063] When driven under an AC signal, the waveform may be
triangular, sinusoid, or any arbitrary waveform. In fact, the
waveform can be customized to generate any specific, desired
tactile feedback. For example, the frequency of the waveform can be
the same throughout the duration of a haptics event, or may be
continuously changed. The waveform or the amplitude of the AC
signal can also be the same throughout the haptics event, or
continuously changed.
[0064] The EMP actuators disclosed herein may have latency rise
time (i.e., the time between the EMP actuator receiving its
activating input signal to the EMP actuator providing the
mechanical haptic response) from less than about 5 milliseconds up
to about 40 milliseconds. The EMP actuators may have a decay time
(i.e., the time between the EMP actuator receiving the cessation of
the activating input signal to the EMP actuator's haptic response
falling below the user's detectable threshold) from less than about
5 milliseconds up to about 40 milliseconds. The EMP actuators may
have an acceleration response of greater than about 0.5 G to about
2.5 G over a frequency range of about 100 Hz to about 300 Hz.
[0065] The above detailed description is provided to illustrate the
specific embodiments of the present invention and is not intended
to be limiting. Numerous variations and modifications within the
scope of the present invention are possible. The present invention
is set forth in the following claims.
* * * * *