User interface system and method

One embodiment of the user interface system comprises: A tactile layer defining a tactile surface touchable by a user and plurality of deformable regions operable between a retracted state, wherein the deformable regions are flush with an undeformable region of the tactile layer; and an expanded state, wherein the deformable regions are proud of the undeformable region. A substrate joined to the undeformable region and defining a fluid port per deformable region and a fluid channel. A displacement device displacing the fluid through the fluid channel and the fluid ports to transition the deformable regions from the retracted state to the expanded state. A first and a second pressure sensor detecting changes in fluid pressure within the fluid due to a force applied to a particular deformable region. A processor determining the particular deformable region to be location of the input force based upon the detected fluid pressure changes.

TECHNICAL FIELD

This invention relates generally to touch sensitive user interfaces, and more specifically to a new and useful system and method for selectively raising portions of a touch sensitive display.

BACKGROUND

Touch-sensitive displays (e.g., touch screens) allow users to input commands and data directly into a display, which is particularly useful in various applications. Such touch screen applications include various consumer products, including cellular telephones and user interfaces for industrial process control. Depending on the specific application, these touch-sensitive displays are commonly used in devices ranging from small handheld PDAs, to medium sized tablet computers, to large industrial implements.

It is often convenient for a user to input and read data on the same display. Unlike a dedicated input device, such as a keypad with discrete and tactilely distinguishable keys, most touch-sensitive displays generally define a flat and continuous input surface providing no significant tactile guidance to the user. Instead, touch-sensitive displays rely on visual cues (e.g., displayed images) to guide user inputs.

A serious drawback of touch-sensitive displays is thus the inherent difficulty a user faces when attempting to input data accurately because adjacent buttons are not distinguishable by feel. Improper keystrokes are common, which forces the user to focus both on the keypad (to properly input the next keystroke) and on the text input line (to check for errors); generally, the user is forced to keep his or her eyes on the display in order to minimize input errors. The importance of tactile guidance is readily apparent in the competition between the Apple's iPhone and RIM's BlackBerry 8800. Touch-sensitive displays and physical hard buttons each have benefits and drawbacks, and digital devices generally incorporate one such component or the other, although some devices do include both disparate components, which often makes for either bulkier devices or devices with less operating power due to size constraints.

As with many touch sensitive displays, nearly any touch on the display surface is registered as an input; this substantially prevents the user from resting a finger or palm on the touch surface while generating proper inputs (such as typing). Furthermore, some touch sensitive displays rely on capacitance changes due to the presence of a finger at a location on the touch surface to indicate a user input, and these devices do not sense user inputs when a barrier exists between a finger of the user and the touch surface, such as when the user is wearing a glove.

Thus, there is a need in the touch-based interface field to create a new and useful interface that incorporates tactile guidance for one or more control buttons and/or incorporates alternatives to sensing a user input. This invention provides such an interface and associated method.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

1. The User Interface System

As shown inFIG. 1, the user interface system100of the preferred embodiment includes: a volume of fluid110; a tactile layer120; a substrate130; a displacement device140; a first pressure sensor150; a second pressure sensor160; and a processor170. The tactile layer120defines an outer tactile surface122touchable by a user and a back surface124opposite the tactile surface122; the tactile layer120includes an undeformable region128and a plurality of deformable regions126, wherein the deformable regions126are operable between: a retracted state (shown inFIG. 4), wherein the deformable regions126are substantially flush with the undeformable region128; and an expanded state (shown inFIG. 5), wherein the deformable regions126are substantially proud of the undeformable region128. The substrate130is joined to the back surface124of the undeformable region128and defines at least one fluid port134per deformable region126, and a fluid channel132, wherein the fluid ports134communicate the fluid110between the fluid channel132and the back surfaces124of the deformable regions126. The displacement device140displaces a portion of the fluid110through the fluid channel132and the fluid ports134to transition the deformable regions126from the retracted state to the expanded state. The first and second pressure sensors150,160detect changes in fluid pressure within a portion of the fluid110due to an input force applied to the tactile surface122at a particular deformable region126(such as in a user input state shown inFIG. 6). The processor170determines the particular deformable region126to be an input location based upon a comparison of the changes in fluid pressure detected by the first and second pressure sensors150,160. The processor170may further characterize input forces received at the tactile surface122as various input types based upon fluid pressure change rates, fluid pressure magnitude, or time-dependent changes in the fluid pressure. The substrate130may further define a support surface138that provides a hard stop for the deformable regions126of the tactile layer120such that a user may not inwardly deform a deformable region126past a certain depth, such as flush with the undeformable region128, as shown inFIG. 6. Furthermore, an attachment point136may join the tactile layer120to the substrate130and define a border between a deformable region126and an undeformable region128.

The user interface system100may further include one or more of the following: a valve180; a touch sensor190; and a display200. The valve180may isolate fluid within a single fluid port and deformable region pair, within a plurality of fluid ports and deformable region pairs, or within a portion of the fluid channel132. The valve180preferably retains a portion of the fluid no at the back surface124of at least one deformable region126to maintain the deformable region126in either the expanded state or retracted state. The touch sensor190preferably detects a user touch129on the tactile surface122, such as at the undeformable region128. The display200preferably outputs an image that is transmitted, through the substrate130and the tactile layer120, to a user.

The user interface system100functions to provide tactile guidance to a user by expanding and retracting the deformable regions126to form distinguishable input regions on the tactile surface122of the tactile layer120, as described in U.S. patent application Ser. No. 12/497,622 titled “User Interface system,” which is incorporated in its entirety by reference. The processor170and the first and second pressure sensors150,160cooperate to determine the location of an input force129applied to the tactile surface122. Specifically, the pressure sensors and processor170cooperate to select, from the plurality of deformable regions126, the particular deformable region126to which the input force129was applied. The user interface system100is preferably incorporated into an electronic device210that includes a digital display, such as the display of an automotive console, a desktop computer, a laptop computer, a tablet computer, a television, a radio, a desk phone, a mobile phone, a PDA, a personal navigation device, a personal media player, a camera, a gaming console or controller, a remote control, or a watch. Such electronic devices often incorporate touch sensors and/or touch displays incorporating capacitive, optical, or resistive touch-sensing technology, or possibly other touch-sensing methods. However, drawbacks may exist in relying on such technology to detect user inputs on deformable tactile surfaces of such electronic devices. Therefore, detecting user inputs at the deformable regions126by sensing pressure changes within the fluid110used to deform the deformable regions126may be more reliable and/or effective than current touch sensor technology. By coupling each fluid port134and associated deformable region126to a central fluid channel132, the number of pressure sensors necessary to isolate the input force location may be substantially reduced. In an example of the user interface device arranged on a display200of an electronic device210, wherein a keypad including twenty-six letters is rendered on the display200, the tactile layer120includes an array of twenty-six deformable regions126, each a separate input region aligned with an image of different letter; the deformable regions126are coupled to the single fluid channel132via fluid ports134, and the displacement device140expands all of the deformable regions126simultaneously such that the user may tactilely distinguish between any two input regions (deformable regions126). Rather than implement twenty-six individual pressure sensors (i.e. one sensor per input region), substantially fewer (e.g., two) pressure sensors detect fluid pressure changes within the fluid channel132and the processor170interprets the signals from the pressure sensors to isolate (i.e. determine) a particular deformable region126to which the input force129is applied by a user. The tactile layer120and substrate130are preferably substantially transparent such that images on the display200may be viewed by the user. However, the user interface system100may be incorporated into any device in any way to reduce the number of sensors and/or sensor complexity required to capture a user input on a deformable tactile surface122.

2. The Volume of Fluid

The volume of fluid110of the preferred embodiment functions as the medium by which pressure is conveyed to the deformable regions126to expand or retract the deformable regions126and by which forces applied to the tactile surface122are conveyed to the pressure sensors150,160. The fluid no is preferably a substantially incompressible fluid, but may alternatively be a compressible fluid or any other suitable fluid sustaining a pressure change during operation of the user interface system100. The fluid110is preferably a liquid (such as water, glycerin, or ethylene glycol), but may alternatively be a gas (such as air, nitrogen, or argon) or any other substance (such as a gel or aerogel) that expands the deformable region126and deforms the tactile surface122. The fluid110preferably substantially fills the fluid ports134and the fluid channel132and is substantially isolated from other fluids that may be external to the user interface system100(or the electronic device210to which the user interface system100is attached), which may reduce the likelihood of air other potential contaminants entering and/or creating bubbles within the fluid110that may disrupt the transmission of an image through the user interface system100. However, any other suitable type of the fluid110may be used.

The volume of fluid is preferably substantially transparent such that an image generated by the display200may be transmitted through the fluid110. The volume of fluid110also preferably has an index of refracted substantially similar to the index of refraction of the substrate130such that light (e.g., an image) passing through a fluid channel132(and/or fluid port134) filled with the fluid110is not optically distorted by the fluid-fluid channel junction. However, the volume of fluid110may have any other property.

3. The Tactile Layer and the Deformable Regions

The tactile layer120of the preferred embodiment functions to define deformable regions126that serve as input regions providing tactile guidance and receive input forces indicating a user input. The tactile layer120preferably defines the tactile surface122that is continuous such that, when swiping a finger across the tactile surface122, the user does not detect interruptions or seams within the tactile layer120. Specifically, the undeformable region128and a deformable region126preferably comprise a single continuous sheet220of material without tactilely distinguishable features between regions. Alternatively, the tactile surface122may include features distinguishing one region from another, such as by differing textures, hardness, dimples, or other tactilely distinguishable features. The tactile surface122is also preferably planar; the tactile surface122may be naturally planar in form or arranged on a surface of the substrate130that is substantially planar. The tactile layer deforms upon displacement of a portion of the fluid110through the fluid channel132and the fluid ports134to the back surface124of the tactile region at the deformable regions126; the tactile layer120also preferably “relaxes” or “un-deforms” back to a normal planar form upon retraction of the portion of the fluid110, whether actively by reversing flow direction of the displacement device140(as shown inFIG. 8) or passively by allowing the elasticity of the tactile surface122to force fluid back through the fluid ports134. In one variation, the tactile layer120contains a deformable region126that is elastic and an undeformable region128that is relatively less elastic. In another variation, the tactile layer120is generally of uniform elasticity throughout at least one cross-section. In yet another variation, the tactile layer120includes or consists of a smart material, such as Nickel Titanium (“Nitinol”), that has a selective and/or variable elasticity. The tactile layer120may be of a uniform thickness or varying thickness; for example, the tactile layer120may be thinner at the deformable regions than at the undeformable region such that the deformable regions are more flexible than the undeformable region.

The tactile layer120is preferably optically transparent, but may alternatively be translucent or opaque. Furthermore, the tactile layer120preferably has one or more of the following properties: high light transmission, low haze, wide viewing angle, minimal internal back reflectance, scratch resistance, chemical resistance, stain resistance, smoothness (e.g., low coefficient of friction), minimal out-gassing, chemical inertness in the presence of the fluid110, and/or relatively low rate of degradation when exposed to ultraviolet light. The tactile layer120preferably comprises a suitable elastic material, including polymers and silicon-based elastomers such as poly-dimethylsiloxane (PDMS) or RTV Silicon (e.g., RTV Silicon 615). In the variation above in which the tactile layer120includes distinct elastic and relatively inelastic portions, the inelastic portion is preferably comprised of a polymer or glass, such as: elastomers; silicon-based organic polymers such as poly-dimethylsiloxane (PDMS); thermoset plastics such as polymethyl methacrylate (PMMA); photocurable solvent-resistant elastomers such as perfluropolyethers; polyethylene terephthalate (PET); or any other suitable material. The tactile layer120may, however, comprise any other suitable material.

Each deformable region126, of the plurality of deformable regions of the tactile layer120, is operable between at least two states, including: a retracted state, wherein the deformable regions126are substantially flush with the undeformable region128; and an expanded state, wherein the deformable regions126are substantially proud of the undeformable region128. However, a deformable region126may be operable in any other state, such as a recessed state, wherein the deformable region126is recessed substantially below the undeformable region128. A deformable region126in the expanded state may act as: (1) a button that, when pressed by the user, implies a single input location (shown inFIG. 9); (2) a slider that, when pressed, implies an input locations at multiple inputs along the deformable region126(shown inFIG. 10); and/or (3) a pointing stick that implies a directional input (shown inFIG. 11). The deformation of the deformable region126may, however, provide any other suitable input type wherein user contact at the deformable region126affects fluid pressure in a portion of the fluid in a way detectable by at least one of the pressure sensors.

A deformable region126that is a button preferably has a dome-like shape, as shown inFIG. 9, but may alternatively have a cylindrical-like shape (with a flat top surface), a pyramid-like shape, a cube-like shape (with a flat top), or any other suitable button shape. The pressure sensors150,160preferably recognize a user touch129applied to the button as a user input.

A deformable region126that is a slider preferably has a ridge like shape, as shown inFIG. 10, but may alternatively have a ring like shape, as shown inFIG. 11; however, a plus-like shape or any other suitable slider shape is also possible. The pressure sensors150,160preferably recognize user touches129at different locations along the slider and distinguish these user touches as different user inputs, such as a first input type for a swipe along the slider in a first direction and a second input type for a swipe in the opposite direction. In one variation, the slider is of a ring-like shape and acts like a “click wheel” similar is form and function to the second-generation Apple iPod, as shown inFIG. 11.

A deformable region126that is a pointing stick, like the button, preferably has a dome-like shape, as shown inFIG. 12, but may alternatively have a cylindrical-like shape (with a flat top surface), a pyramid-like shape, a cube-like shape (with a flat top), or any other suitable button shape. The pressure sensors150,160preferably recognize user touches129in different directions and/or at different locations along the pointing stick and distinguish these user touches as different user inputs. Preferably, depression of the expanded deformable region126that is a pointing stick implies a user input type related to the location of the depression relative to the geometry of the pointing stick. For example, in the variation in which the deformable region126is a pointing stick with a dome-like shape, a depression of the deformable region126in the upper right quadrant is interpreted differently than a depression thereof in the lower right quadrant. Additionally, the user may depress the deformable region126that is a pointing stick in a sweeping motion, for example, a “sweep” from the upper right quadrant to the lower right quadrant of the deformable region126. This may be interpreted as a dynamic input, such as those recognized on the “click wheel” of a second generation Apple iPod. In another example, the inputs on a deformable region126that is a pointing stick may perform in a manner similar to the pointing stick trademarked by IBM as the TRACKPOINT and by Synaptics as the TOUCHSTYK (which are both informally known as the “nipple”).

4. The Substrate

The substrate130of the preferred embodiment functions to support the tactile layer120such that fluid110communicated through the fluid channel132and the fluid ports134outwardly deforms the deformable regions126. The back surface124of the tactile layer120is preferably attached to the substrate130via an attachment point136(shown inFIGS. 1 and 5) that at least partially defines the size and/or shape of the undeformable region128; the attachment point136functions to define a border between a deformable region126and the undeformable region128of the tactile layer120. The attachment point136may be a series of continuous points that define an edge or boundary, but may alternatively be a series of non-continuous points; the system may also comprise a series of attachment points. The attachment point136may be formed via an adhesive, chemical bonding, welding, diffusion bonding, or any other suitable attachment material and/or method. The method and/or material used to form the attachment point136preferably yields similar optical properties as the tactile layer120and/or the substrate130, but may alternatively yield any other optical property. Other undeformable regions of the tactile layer120may or may not be adhered to the substrate130using similar or identical materials and/or methods. However, any other suitable arrangement, material, and/or manufacturing method may be used to join the substrate130to the tactile layer120. The substrate and tactile layer assembly may therefore comprise a sheet220containing at least the passive elements necessary to provide tactile guidance on a surface, such as on a display of an electronic device210.

The substrate130preferably comprises a substantially rigid material such that a force applied on the tactile surface122and transmitted through the substrate130does not substantially deform any of the fluid ports134or the fluid channel132. By substantially maintaining the cross-section of the fluid channel132and/or fluid ports134, the fluid is still preferably communicated throughout the fluid channel132, fluid ports134, back surfaces124of the deformable regions126, and the pressure sensors150,160such that the pressure sensors and processor170may reliably generate and interpret fluid pressure signals to determine the location of a user input on the tactile surface122. The substrate130also preferably defines a substantially rigid support surface138adjacent to a deformable region126. The support surface138of the substrate130preferably resists deformation of the deformable region126inward past flush with the undeformable region128, as shown inFIG. 6. This provides support for the tactile layer120to substantially prevent the tactile layer120from deforming into a fluid port134when the force is applied over a deformable region126. The support surface138also preferably provides a hard stop upon which the deformable region126rests in the retracted state, as shown inFIG. 4, such as following active withdrawal of a portion of the fluid from the fluid channel132to retract the deformable region126. The substrate130is preferably uniform in thickness, though only the side of the substrate130adjacent to the tactile layer120may be planar. The support surface138is also preferably planar, but the support surface138may also define a concave geometry into which the deformable layer deforms in a third, recessed state. However, the substrate130may be of any other geometry that retains the undeformable region128and permits the deformable regions126to expand to the expanded state and retract to the retracted state.

The substrate130also functions to define the fluid channel132and fluid ports134. In a first variation, the substrate130comprises a first sub-layer joined to a second sub-layer, wherein the first sub-layer includes an elongated pocket and the second sub-layer includes a plurality of through-bores. In this variation, the fluid channel132is defined by the elongated pocket of the first sub-layer and a surface of the second sub-layer adjacent to first sub-layer; the through-bores of the second sub-layer define the fluid ports134, and the fluid ports134are preferably aligned with the fluid channel132such that the fluid is communicable between the fluid ports134and the fluid channel132. In this first variation, the pocket is preferably machined into the second sub-layer, such as by laser ablation, bulk micromachining, or conventional machining (e.g., with a keyseat cutter or endmill), but may also be etched, formed, molded or otherwise created in the first sub-layer. The fluid channel132is preferably large enough in cross-section to communicate the fluid to the fluid ports134at a suitable flow rate given a pressure increase generated by the displacement device140; however, the fluid channel132is preferably substantially small enough in cross-section such that the fluid channel132is substantially difficult for the user to detect visually; however, the fluid no may have an index of refraction matched substantially to that of the substrate130such that the fluid channel132is substantially difficult for the user to see despite the size of the fluid channel132. The through-bores are preferably machined into the second sub-layer, such as by laser ablation, bulk micromachining, or conventional drilling, but may also be formed, etched, molded, or otherwise created in the second sub-layer. The bores (fluid ports134) are preferably substantially small in cross-section such that the user does not detect the fluid ports134through the tactile layer120, either visually when looking through the tactile layer120or tactilely when sweeping a finger across the tactile surface122. For example, the fluid ports134may be circular in cross-section and less that 500 um in diameter, though the fluid ports134are preferably less than 100 um in diameter. In a second variation, the substrate130comprises a first sub-layer joined to a second sub-layer, wherein the first sub-layer defines a recess with border substantially encompassing the perimeter of the deformable regions126and the second sub-layer is substantially similar to the second sub-layer described in the first variation. In this second variation, the first and second sub-layers join to enclose the recess and form a substantially long and wide cavity within the substrate130, wherein the cavity communicates a portion of the fluid to the fluid ports134. In the first and second variations above, or in any other variation, the first and second sub-layer may be joined by any acceptable means, such as by the materials and/or methods described above to join the tactile layer120to the substrate130. In a third variation, the fluid ports134are a property of the material; for example, the substrate130may comprise a porous material that includes a series of interconnected cavities that allow the fluid no to flow through the substrate130to the back surfaces124of the deformable regions126. However, the substrate130may comprise any other material or any number of sub-layers containing any number of features formed by any process, and the sub-layers may be joined (if applicable) in any other way. Furthermore, the substrate130may define any number of fluid ports134, of any shape or size, per deformable region126.

In the variation of the substrate130that defines a substantially planar surface adjacent to the back surface124of the tactile layer120, the fluid channel132preferably communicates a portion of the fluid no in a direction substantially parallel to the plane of the substrate130. The fluid channel132is preferably elongated and preferably passes through a substantial portion of the substrate130. Furthermore, the fluid ports134preferably communicate the fluid110in a direction substantially normal to the planar surface of the substrate130. However, the fluid110may pass through the fluid ports134and fluid channel132in any other direction, such as in a variation of the user interface system100comprising a series of stacked fluid channels and a network of fluid ports.

The substrate130preferably has optical properties substantially similar to the optical properties of the tactile layer120, such as optical transparency, low internal reflectance, and low haze characteristics. The substrate130also preferably has chemical properties similar to those of the tactile layer120, such as minimal outgassing and chemical inertness in the presence of the fluid110.

As shown inFIG. 1, the fluid channel132couples the displacement device140to the back surfaces124of the deformable regions126. The fluid channel132allows the fluid110to enter the fluid ports134to expand the deformable regions126. Fluid may also be displaced away from the deformable regions126through the fluid channel132to retract the deformable regions126. As shown inFIGS. 3, and13, in a first variation, a deformable region126is arranged beside the fluid channel132. In a second variation, as shown inFIG. 7, a deformable region126is arranged on top of the fluid channel132; in this second variation, the fluid channel132may be of a cross-sectional area substantially similar to that of the fluid port134, but may alternatively be larger (shown inFIG. 7), smaller (shown inFIG. 2), or of any other suitable size. The second variation of the arrangement of the fluid channel132may decrease complexity in the implementation of multiple deformable regions126. For example, in the first variation, the fluid channel132may require extended fluid ports134that couple the deformable regions126to the fluid channel132, as shown inFIG. 13; but, in the second variation, the fluid ports134may be short and immediately adjacent to the fluid channel132, as shown inFIGS. 1,7, and8. However, the fluid channel132may be of a single main channel of any suitable form, such as a zig-zag (FIG. 8), a serpentine (FIG. 1), a loop, a straight channel, a set of parallel channels, and set of parallel and perpendicular intersecting channels, a set of stacked and non-intersecting channels of any form.

The fluid channel132preferably includes a first end and a second end. In a first variation, the first end is a fluid inlet and a fluid outlet. In this first variation, the second end is preferably closed, or “blind”, such that fluid may neither enter nor exit the fluid channel132at the second end, as shown inFIG. 1. In a second variation, the first end functions as a fluid inlet and the second end functions as a fluid outlet, as shown inFIG. 8. In this variation: the fluid channel132may define a fluid loop within the user interface system100; and/or the first and second ends may function as a fluid inlet and a fluid outlet interchangeably. However, any other suitable arrangement of the fluid channel132may be used.

5. The Displacement Device

The displacement device140of the preferred embodiment functions to displace a portion of the fluid110within the fluid channel132and fluid ports134to expand the deformable regions126from the retracted state to the expanded state. The displacement device140is preferably a mechanical pump (such as micro pump #MDP2205 from ThinXXS Microtechnology AG of Zweibrucken, Germany or micro pump #mp5 from Bartels Mikrotechnik GmbH of Dortmund, Germany). However, the displacement device140may alternatively be a plunger-type device, as shown inFIG. 1, a heating element that expands a portion of the fluid no by heating the fluid, or a series of electrodes that displace a portion of the fluid through the fluid ports134via electroosmotic flow. However, the displacement device140may alternatively influence the volume of the fluid no in any other suitable manner, for example, as described in U.S. patent application Ser. No. 12/497,622 titled “User Interface System” or in U.S. patent application Ser. No. 13/278,125 titled “User Interface System”, which are both hereby incorporated in their entirety by this reference. The displacement device140is preferably coupled to the first end of the fluid channel132, as shown inFIG. 1, but may be coupled to any other section of the fluid channel132. When implemented in a mobile device, such as a cell phone or tablet computer, the displacement device140preferably increases the volume of the fluid no between the substrate130and the back surface124of the tactile layer120at each deformable region126by 0.003 ml to 0.1 ml; this volume is preferably suitable to expand a circular deformable region126, with a diameter between 2 mm and 10 mm, to an extent tacitly distinguishable by the user. When implemented in this or any other application, however, the volume of the fluid displaced may be of any other suitable amount.

6. The First and Second Pressure Sensors

The first and second pressure sensors150,160of the preferred embodiment function to detect a change in fluid pressure within a portion of the fluid no, wherein the pressure change is due to an input force129applied to and inwardly deforming a particular deformable region126. A change in fluid pressure within a portion of the fluid no is preferably communicated to the pressure sensors150,160via a longitudinal pressure wave (e.g., a P-wave) through a portion of the fluid channel132, a portion of a fluid port134, or any other fluid conduit within the user interface system100; however, the pressure change may be communicated via a transverse wave or combination of longitudinal and transverse waves. Pressure wave reflections within the fluid channel132, fluid ports134, or any other fluid conduit in the user interface system100are also preferably captured by the pressure sensors150,160such that the origin of the pressure wave (e.g., the input force) can be traced via analysis of the pressure wave data by the processor170.

The first and second pressure sensors150,160are preferably coupled to the fluid channel132, wherein the first pressure sensor150detects fluid pressure changes in the fluid channel132at a first location and the second pressure sensor160detects fluid pressure changes in the fluid channel132at a second location different than the first location, as shown inFIG. 1. The pressure sensors150,160preferably detect the input force129that is applied on a deformable region126in the expanded state, but may also or alternatively detect the input force129that is applied on a deformable region126in the retracted or recessed states. For example, in the variation in which the substrate130defines a support surface138that is concave, the user may apply a force129to the tactile surface122that inwardly deforms a particular deformable region126past flush with the undeformable region128. When the user applies the input force129to the tactile surface122, the fluid110is preferably prevented from escaping the fluid channel132(e.g., from either end of the fluid channel132), such as by closing a valve180between the fluid channel132and displacement device140or by locking the position of the displacement device140. Thus, the input force129that inwardly deforms the particular deformable region126also increases fluid pressure at the back surface124of the particular deformable region126; the increase in fluid pressure is communicated through the associated fluid port134(or ports), through the fluid channel132, and to the pressure sensors150,160.

The pressure sensors150,160may be located adjacent to the back surface124of a deformable region126, within a fluid port134, and/or in the fluid channel132. A portion of either pressure sensor150or160may be arranged within the substrate130or may be physically coextensive with the substrate130. For example, the first pressure sensor150may include a diaphragm that is physically coextensive with the substrate130and forms a portion of a wall of the fluid channel132such that a fluid pressure change within the fluid channel132deforms the diaphragm (as shown inFIG. 8); this deformation preferably results in an output from the first pressure sensor150. In this example, the diaphragm may be formed (such as by machining, etching, or molding) directly into the substrate130. A portion of either pressure sensor150or160may also or alternatively be arranged on or within the tactile layer120. For example, the first pressure sensor150may comprise a strain gage that is mounted on the back surface124of the tactile layer120at a deformable region126; a force applied to the deformable region126in the expanded state produces an output, from the first pressure sensor150, indicative of a strain at the deformable region126. Furthermore, the variation of a pressure sensor that comprise a strain gauge may indirectly detect a pressure change within the fluid no by capturing a strain in any portion of the tactile layer120and/or the permeable layer140. A strain captured by a pressure sensor is preferably indicative of a change in pressure within a portion of the fluid110(e.g., indicating a user touch on a deformable region126), but such a strain may also be indicative of a user touch elsewhere on the tactile layer120; the processor170preferably compares strains captured by a plurality of strain gauge pressure sensors to determine the particular location of such a user touch. However, the pressure sensors may be arranged anywhere else within the user interface system100, may interface with any other element in any other way, and may be of any other type of sensor that directly or indirectly indicates a change in pressure within the fluid110.

In the variation in which the fluid ports134communicate a portion of the fluid between the plurality of deformable regions126and the fluid channel132, the pressure sensors are preferably coupled to the fluid channel132. For example, the first pressure sensor150may be arranged substantially proximal to the first end of the fluid channel132and the second pressure sensor160may be arranged substantially proximal to the second end of the fluid channel132. A third pressure sensor may also be coupled to the fluid channel132and arranged between the first and second pressure sensors150,160. In the variation that includes a valve180arranged between a fluid port134and the fluid channel132and which closes to prevent fluid flow out of the fluid port134and into the fluid channel132, either of the first or second pressure sensors150or160is preferably located within the fluid port134or adjacent to the back surface124of the deformable region126. A portion of each pressure sensor150,160is preferably in direct contact with the portion of the fluid no within any of the fluid channel132or fluid ports134or at the back surface124of a deformable region126; however, the pressure sensors150,160may be substantially remote from the fluid channel132and fluid ports134such that the fluid110(and thus the fluid pressure and/or a pressure wave) is communicated to the pressure sensors via a fluid duct; such a fluid duct is preferably smaller in cross-sectional area than either of the fluid channel132and the fluid ports134. However, the pressure sensors150,160may be arranged at any other location and fluid pressure may be communicated to the pressure sensors150,160via any other method, feature, or element.

The pressure sensors150,160are preferably absolute pressure sensors, but may alternatively be differential pressure sensors in which the pressure sensors compare the pressure within a portion of the fluid to a reference pressure, such as ambient air pressure proximal to the user interface system100. In the variation of the first pressure sensor150that is a differential pressure sensor taking ambient air pressure as the reference pressure, a feedback control loop between the displacement device140and the first pressure sensor150may be implemented such that fluid pressure within the fluid channel132is maintained substantially at ambient air pressure; in the retracted state, this preferably maintains the deformable regions126substantially flush with the undeformable region128. This may be particularly useful when the user interface system100is taken to higher altitudes: as altitude increases, ambient air pressure decreases and the pressure at the back surface124of a deformable region126is preferably modified, via the control loop, to compensate for the change in ambient air pressure. The pressure sensors150,160may be of any type, such as piezoresistive strain gauge, capacitive, electromagnetic, piezoelectric, optical, potentiometric, resonant, or thermal pressure sensors. The pressure sensors150,160may also comprise or be replaced by flow meters, wherein the flow meters detect fluid flow within the user interface system100(e.g., the fluid channel132and/or the fluid ports134) and the processor170analyzes the outputs of the flow meters to determine the location of an input force on the tactile layer120. However, any other suitable arrangement or type of pressure sensor that detects a change in fluid pressure may be used, and the first and second pressure sensors150,160need not be of the same type or form or arranged in similar ways within the user interface system100. However, the processor170may analyze the output of only a single pressure sensor (such as the first pressure sensor iso) to determine the location of the input force on the tactile layer, such as via a method similar to that described in “TIME-REVERSAL FOR TEMPORAL COMPRESSION AND SPATIAL FOCUSING OF ACOUSTIC WAVES IN ENCLOSURES” by Deborah Berebichez, Ph.D., Stanford University, 2005, which is incorporated in its entirety by this reference.

7. The Valve

The user interface system100may further comprise a valve180operable between an open state, wherein the displacement device140displaces a portion of the fluid through the valve180to transition a deformable region126from the retracted state to the expanded state, as shown inFIG. 8; and a closed state, wherein the valve180substantially retains a portion of the fluid at the back surface124of the deformable region126. The valve180preferably cooperates with the displacement device140to direct a portion of the fluid toward the back surface124of a deformable region126to expand the deformable region126. In a first example, if a first deformable region126is to be expanded and a second deformable region126is to remain retracted, a first valve180, arranged between the first deformable region126and the fluid channel132(e.g., along an associated fluid port134), opens to allow a portion of the fluid to the back surface124of the first deformable region126while a second valve, arranged between the second deformable region126and the fluid channel132, remains closed to prevent a change in the state of the second deformable region126. In a second example, if the state of a first deformable region126A is to be independent of a second deformable region126B, a valve180may be arranged within the fluid channel132and between a fluid port associated with a first deformable region126A and a fluid port associated with a second deformable region126such that the valve isolates the first deformable region126A from the second deformable region126B. To maintain a deformable region126in the expanded state, a valve180arranged between the expanded deformable region126and the fluid channel132may close to prevent fluid flow away from the back surface124of the deformable region126. The valve180may be located: within the fluid channel132, such as to isolate a first group of deformable regions126from a second group of deformable regions126(as shown inFIG. 13); at the first end of the fluid channel132to isolate control flow of the fluid between the fluid channel132and the displacement device140(as shown inFIG. 8); within a fluid port134to isolate a single deformable region126from the plurality of deformable regions126; or at any other location.

The valve180may be any suitable type of valve180, such as a ball, butterfly, check (i.e. one-way), diaphragm, knife, needle, pinch, plug, reed, or spool valve, or any other type of valve. The valve180may also be integral with the displacement device140, such as a piston-type displacement device relying on a series of valves to control fluid flow therethrough. The valve180may be of any size, but preferably defines a fluid gate of cross-sectional area substantially similar to the cross-sectional area of the fluid channel132, fluid port134, or other element to which the valve180is coupled. The valve180is also preferably electrically activated, such as by inducing a voltage differential across two input leads of the valve180to open and/or close the valve180. The valve180is preferably normally in the closed state, but may also normally be in the open state or in any other state. The valve180preferably permits two-way flow but may alternatively be a one-way (e.g., check) valve. In the variation of the valve180that is a one-way valve normally permitting flow from a first side to a second side, the valve180may permit reverse fluid flow only given a fluid pressure at the second side substantially greater than the fluid pressure at the first side (or a fluid pressure at the second side greater than a given threshold pressure). In this variation, a user input of a substantially large force may increase pressure within a portion of the fluid no above a level that is not conducive to the safety or longevity of the user interface system100(or the electronic device210in which the user interface system100is implemented); such a valve180, with a return threshold pressure, may open, given such high fluid pressure, to reduce fluid pressure within the channel and prolong the life of the user interface system100(or electronic device210); such a valve may also or alternatively provide a “click” sensation to the user given an appropriate input in the tactile surface122. This same feature may be implemented without such a one-way valve, such as by actively opening an electromechanical valve given a fluid pressure, detected by either pressure sensor150or160, above a preset fluid pressure threshold. However, any other type of valve180, number of valves, or arrangement of the valve(s) may be implemented in the user interface system100.

8. The Display

The user interface system100may further comprise a display200generating an image that is transmitted through the tactile layer120. The image is preferably aligned with at least one deformable region126of the plurality of deformable regions. The image preferably provides visual guidance to the user, such as by indicating the input type associated with an input force129applied to a particular deformable region126. The display200is preferably coupled to the substrate130opposite the tactile surface122. The display200may be joined to the substrate130via any of the methods or elements described above to join the tactile layer120to the substrate130; however, the display200may also be clamped, suctioned, or statically adhered to the substrate130, or joined thereto by any other means or method. The display200is preferably a digital display, such as an e-ink, LED, LCD, OLED, or plasma display. The display200may also be remote from the user interface system100, wherein the image is projected onto and/or through the tactile surface120. However, the display200may be any other type of display that renders an image that may be transmitted to the user via the substrate130and the tactile layer120.

9. The Touch Sensor

The user interface system100may further comprise a touch sensor190that detects a user touch on the tactile surface122of the tactile layer120. The touch sensor190may be of any form or function described in U.S. patent application Ser. No. 13/278,125 titled “User Interface System.” The touch sensor190is preferably a capacitive touch sensor190, but may also be an optical or resistive touch sensor190or function via any other technology. The touch sensor190is preferably physically coextensive with the display200, but may also be interposed between the display200and the substrate130or between the substrate130and the tactile layer120, or may be physically coextensive, in whole or in part, with any other element. The touch sensor190may also be arranged adjacent to the tactile layer120opposite the substrate130, such as in the variation of the touch sensor190that is an optical touch sensor. The touch sensor190preferably compliments the pressure sensors150,160: the touch sensor190preferably detects a user touch129on the tactile surface122at the undeformable region128and the pressure sensors150,160detect a user touch at the deformable regions126. However, the touch sensor190may serve as the primary detection method for a touch129on a deformable region126, and the pressure sensors150,160may serve a backup or confirmation role in user input detection; however, the opposite may also be implemented. The touch sensor190may, however, be of any other type, arranged in any other location, and used in any other way to detect a user input129on the tactile surface122.

10. The Processor

The processor170of the preferred embodiment functions to determine the location of a user input129to be at a particular deformable region126. The processor170receives signals from the pressure sensors indicating detected changes in fluid pressure in the fluid channel132, the fluid ports134, and/or at the back surface124of the tactile layer120at one or more deformable regions126. The processor170therefore cooperates with the pressure sensors150,160to detect the presence of a force on the tactile surface122and to interpret the force to determine the input location; the processor170may also detect input magnitude, input speed, and/or input direction. The processor170preferably interprets the force based upon the detected pressure changes, the known locations of the pressure sensors150,160, the known locations of the deformable regions126, the known location of an image rendered on the display200and aligned with a deformable region126, and/or any other suitable information. The processor170may also communicate with additional sensors, such as a touch sensor190or a third pressure sensor, to determine the location of the user input.

In a first variation, the pressure sensors150,160detect a fluid pressure change and the processor170interprets the presence of a user input129based upon the pressure change. The processor170preferably compares the detected pressure change to a pressure change threshold to determine whether the detected pressure change is indicative of a user input. By comparing the detected pressure change to the pressure change threshold, a proper input is preferably distinct from an improper input, such as the case of the user resting a finger or palm on the tactile surface122, as action that is not intended to be a proper input. In a first example, the user unintentionally brushes a finger or palm against a particular deformable region126, causing a substantially small pressure change within the fluid channel132; this pressure change is detected by the pressure sensors150,160but is still less than the threshold pressure change, so the processor170does not determine the pressure change to indicate a proper user input. In a second example, the user rests a finger on top of a particular deformable region126without intending to provide an input (this may be comparable to a user of a traditional keyboard resting a finger on a key without substantially depressing the key to generate an input); though this causes a change in pressure within the fluid channel132, the detected pressure change, again, is not determined to be indicative of a proper input when compared against the threshold input pressure. However, if the detected pressure change is above the pressure change threshold, the processor170preferably determines a proper user input event. This provides a benefit over typical touch-sensitive displays (such as those utilizing capacitive sensing methods) that are often unable to differentiate between user touches of varying force (e.g., between a proper input and a user resting a finger on the display200). The processor170, therefore, is preferably able to discern between pressure changes that result from a finger resting on a particular deformable region126and a finger imparting a force resulting in a pressure change that is a proper input. The processor170may also adjust the pressure change threshold, such as for varying initial fluid pressures (e.g., the deformable regions126are raised to varying initial heights in the expanded state by adjusting the initial fluid pressure in the fluid channel132). However, rather than compare fluid pressure changes (e.g., the magnitude of fluid pressure changes, the change rate of fluid pressure changes), the processor170may compare the absolute detected fluid pressure to an absolute pressure threshold; the processor170may also modify this absolute pressure threshold.

The processor170of the first variation may compare the length of time that the detected pressure change (or absolute detected pressure) is above a pressure change (or absolute pressure) threshold to a time threshold (or a combination of time and pressure change thresholds). In an example, the user initiates a user input by touching a particular deformable region126with a finger but changes his mind and quickly retracts a finger from the particular deformable region126; this effectively “cancels” the input. Thus, if the length of time that the increased pressure is detected is below the threshold time, then the processor170preferably determines that a proper input was not provided and the input129is ignored. If the length of time that the increased pressure is detected is above the threshold time, then the processor170preferably determines the presence of a proper user input. However, the processor170and the pressure sensors150,160may cooperate to determine the presence of a user input using any other suitable means and/or method.

In a second variation, the pressure sensors150,160and the processor170cooperate to determine the type of a user input. In a first example, the pressure sensors150,160detect the rate change of the fluid pressure in the fluid channel132, which is proportional to the rate of the applied force on the tactile surface122. The processor170determines the type of user input based upon the detected fluid pressure change rate; for example, a first fluid pressure change rate indicates a first input type and a second fluid pressure change rate less than the first fluid pressure change rate indicates a second input type. In a usage scenario, the input indicates a user desire to scroll through a document: a higher rate of pressure change requests a faster scroll rate and a lower rate of pressure change indicates a slower scroll rate (though this functionality may also be implemented by analyzing the magnitude of the fluid pressure or the magnitude of the change in fluid pressure rather than the fluid pressure change rate). (This usage scenario may also be applied to changing the brightness or contrast of the display200or the volume or processing speed of the electronic device.) In a second example, the pressure sensors150,160detect the magnitude of the fluid pressure and the processor170determines the magnitude of the applied force based upon the magnitude of the fluid pressure, which is proportional to the magnitude of the applied force. Either pressure sensor150or160may thus function as an analog input for the electronic device210, wherein the a varying force applied to a deformable region126results in a variable command, such as volume of a speaker or firing rate of a gun in a computer game. Similar to the first example, a first magnitude of fluid pressure change may indicate a first input type and a second magnitude of fluid pressure change may indicate a second input type. In a third example, a determined first length of time of an applied force may indicate a first input type and a second length of time of an applied force may indicate a second input type. In a usage scenario, the electronic device210is a camera with autofocus capability; the user “half-presses” a shutter button that is a deformable region126, in the expanded state, to initiate autofocus; however, because the force required to “half-press” the button is relatively small, the detected force is not necessarily indicative of a user desire to initiate autofocus. In this usage scenario, the processor170determines the desire to initiate autofocus if the force (e.g., the change in fluid pressure) is detected over a particular period of time; in this usage scenario, the processor170may also detect the magnitude of the applied force (as described in the second example) to distinguish between a user desire to initiate the autofocus capability (a first input type) and a user desire to take a photo (a second input type). In a fourth example, the pressure sensors150,160detect the distance by which the user inwardly deforms the particular deformable region126in the expanded state. The distance by which the user inwardly deforms the particular deformable region126may be detected by measuring the pressure and/or pressure change that results from the inward deformation of the expanded particular deformable region126; specifically, the processor170may determine that a particular pressure and/or pressure change correlates to a particular distance by which the user inwardly deforms the particular deformable region126. However, the processor170and the pressure sensors150,160may cooperate to determine the type of user input by any other suitable method and/or means.

In a third variation, the pressure sensors150,160and the processor170cooperate to determine the location of the user input. The third variation relies substantially on a fluidic property known in the field, wherein an increase in fluid pressure at a particular point in a fluid vessel (e.g., a fluid channel132or fluid port134) propagates throughout the fluid vessel over time. The first pressure sensor150and the second pressure sensor160are preferably coupled to the fluid channel132(or other fluid vessel of the user interface system100) at an appreciable distance from each other, as shown inFIGS. 1 and 8(although the system may incorporate only a single pressure sensor). A change in fluid pressure (or absolute fluid pressure) is detected as a function of time at both the first and second pressure sensors150,160; the outputs of the first and second pressure sensors150,160are preferably of the magnitude of the pressure change (or absolute pressure) relative to time, and a comparison of these two outputs preferably results in a determination of the location of the force129applied to the tactile surface122by the user. In a first variation, the first and second pressure sensors150,160are located at different locations within a cavity defined by the fluid port134and the back surface124of an associated particular deformable region126; the two pressure sensors150,160and the processor170thus cooperate to determine the location of a user input along the particular deformable region126. In a second variation, shown inFIG. 2, the pressure sensors150,160are located at different locations within the fluid channel132, such that the pressure sensors150,160and the processor170cooperate to determine the location of a user input among various deformable regions126coupled to the fluid channel132via a plurality of fluid ports134. In a first example, because an increase in pressure at a particular deformable region126requires more time to travel to the more distant of the first and second pressure sensors150,160, the processor170determines the location of a user input to be closer to the pressure sensor that detects a pressure change of a certain magnitude in the least amount of time; in this example, the processor170preferably determines the specific deformable region126upon which the input force129is applied. In a second example, because fluid pressure changes more rapidly at a location nearer the source of the pressure increase, the processor170determines that the location of the user input129is nearer to the pressure sensor that detects a higher rate of pressure change. In a third example, because fluid pressure in a fluid increases at a faster rate and reaches a higher maximum fluid pressure nearer the origin of the pressure increase, the processor170determines the location of the user input to be more proximal to the sensor that detects a higher fluid pressure after a particular time following a first detected change in fluid pressure (e.g., the application of the input force).

In a fourth variation, the pressure sensors150,160are located within the fluid channel132and detect fluid pressure changes therein, as shown inFIGS. 2 and 7. The fluid channel132is preferably of a substantially uniform cross-section and of a known length. Additionally, in the variation of the fluid channel132shown inFIG. 7and the channel arrangement shown inFIG. 1, the volume of fluid110within the fluid ports134is preferably small relative to the volume of fluid110contained within the fluid channel132; the flow of the fluid110through the fluid channel132may thus be substantially unaffected by fluid flow through any of the fluid ports134. Furthermore, data including the location of the pressure sensors150,160and the length of the fluid channel132is preferably available to the processor170such that standard in-tube fluid flow dynamics may be used to determine the location of a user input129provided on a deformable region126. For example, as a portion of the fluid no is displaced through the fluid channel132as a result of the force129applied by the user, the time at which a change in pressure is detected at the pressure sensors150,160and may used to determine where, within the fluid channel132, the fluid pressure first increases. More specifically, for a fluid of a known viscosity traveling through a tube of a known cross-section, the time difference between when a change in pressure is detected by the first pressure sensor150and when the change in pressure is detected by the second pressure sensor160may be used by the processor170to pinpoint the location of the initial pressure increase within the fluid channel132, such as relative to the first and second pressure sensors150,160; this location is preferably associated with the location of a fluid port134and/or the particular deformable region126associated with the fluid port134.

In the above variations, the processor170preferably interprets data provided by the first and second pressure sensors150,160at a particular time; the processor170may determine the location of the user touch by comparing the data gathered by the first and second pressure sensors150,160. Generally, the processor170may compare the magnitude of the pressure change (in the first variation), the magnitude of the rate of change (in the second variation), the time of the detected pressure change (in the third and fourth variations), or any other suitable data detected by the first and second pressure sensors150,160and pertinent to determining the location of the user input129. Alternatively, the processor170may determine the location of the user touch129by comparing data gathered by the first and second pressure sensors150,160to a dataset. For example, the dataset may be a table or library of pressure-related readings that indicate the location of a pressure increase given particular outputs from the first and/or second pressure sensors150,160; this preferably indicates the particular deformed region to which the input force129is applied. In the example arrangement shown inFIG. 2, a user input at a deformable region126C preferably results in comparison of pressure readings at the first and second sensors150,160that is different than a pressure reading comparison resulting from a user input at a deformable region126B; the processor170determines the input based on these comparisons. This method of determining the location of the user input may also facilitate determining locations of user inputs that are provided on the tactile surface122simultaneously. For example, in the arrangement shown inFIG. 2, simultaneous user inputs provided at deformable region126A and deformable region126B preferably result in a comparison of pressure readings (at the first and second pressure sensors150,160) that is different than a pressure reading comparison resulting from simultaneous user inputs provided at deformable region126B and deformable region126C; both such pressure reading comparisons are preferably different than the pressure reading comparison resulting from a single user input provided at deformable region126A. Preferably, each deformable region126has a distinct input characteristic, such as a distinct time period over which an input force applied on a deformable region126is transmitted, as a fluid pressure change, from the deformable region126to a pressure sensor(s)150or160in terms of time differences. This preferably permits determination of multiple input locations attributed to multiple simultaneous input forces at a plurality of deformable regions126; specifically, this preferably allows the processor170to resolve multiple input locations at once by looking at the combination of pressure signals at each sensor150,160. Furthermore, the processor170may take into account one or more previous input force locations and or relevant timing of previous input forces when determining a more recent input location. The number of pressure sensors and deformable regions is preferably chosen to ensure that each deformable region has such a unique characteristic.

In the variation of the deformable region126that functions as a slider or a pointing stick, as the user varies the location of the user input along the slider or the direction of the input on the pointing stick, the pressure detected by the first and second pressure sensors150,160may be compared to a data set that includes pressure readings expected for such applied inputs. However, the dataset may include any suitable type of data against which the processor170may: compare data gathered from the pressure sensors150,160; and determine the location of a user input129(or a plurality of simultaneous user inputs). This method is particularly useful in a device in which the specific locations of user inputs on deformable regions must be predicted; in such a device, the pressure sensors150,160may be the only sensors necessary to detect relevant details (e.g., location and magnitude) of the user input129, and this preferably decreases the number and complexity of sensors in the device. However, any number of pressure sensors may be incorporated into the user interface system100and any other suitable method for determining the location of the user input129may be used. The processor may also compare the outputs of any number and/or combination of pressure sensors within the user interface system100.

The pressure sensors150,160and the processor170may also enhance the performance of the user interface system100or the electronic device210in which the user interface system100is implemented. For example, the processor170may determine that the detected pressure within the fluid channel132is lower than a predetermined threshold (such as for more than a threshold period of time) and may actuate the displacement device140to displace additional fluid into the fluid channel132. Alternatively, the pressure sensors150,160may detect the ambient air temperature; the processor170may, in turn, determine that the ambient temperature has decreased and thus actuate the displacement device140to displace fluid out of the fluid channel132to decrease the fluid pressure within the fluid channel132in order to protect the user interface system100from damage, such as from excessive internal pressures. However, the pressure sensors150,160and processor170may alternatively cooperate to perform any other suitable function.

11. The Method

As shown inFIG. 14, the method S100of the preferred embodiment functions to determine an input location on a tactile surface of the user interface system100. The steps include: displacing fluid through a fluid channel and a series of fluid ports to outwardly deform a plurality of deformable regions of a tactile layer S110; detecting a change in fluid pressure at a first location within the fluid channel due to an input force applied to the tactile surface at a particular deformable region S120; detecting a change in fluid pressure at a second location within the fluid channel due to the input force applied to the tactile surface S130; and selecting the particular deformable region, from the plurality of deformable regions, as the input location based upon a comparison of the changes in fluid pressure detected at the first and second locations within the fluid channel S140. The step of displacing the fluid through the fluid channel S110is preferably performed by a displacement device, as described above. The steps of detecting the fluid pressure changes at the first and second locations within the fluid channel S120, S130are preferably performed by the first and second pressure sensors described above. The step of selecting the particular deformable region S140is preferably performed, by the processor, via the methods describes above.