Piezoelectric film-based tactile perception feedback device and method

Abstract

The invention relates to the technical field of man-machine interaction and intelligent sensing, and discloses a tactile perception feedback device and method based on a piezoelectric film, the tactile perception feedback device based on the piezoelectric film comprises an elastic metal strip, two ends of the metal strip are fixed to form a simply supported beam or cantilever beam structure; the piezoelectric unit comprises a first chip and a second chip, the first chip and the second chip are arranged at the two ends of the metal strip respectively, the first chip and the second chip both have a direct piezoelectric effect and an inverse piezoelectric effect, and a first working mode and a second working mode exist between the metal strip and the first chip and between the metal strip and the second chip; according to the invention, high-sensitivity perception and effective stress feedback can be carried out while miniaturization is realized, and the naturalness and reality sense of tactile interaction are improved.

Description

Technical Field

[0001] This invention relates to the field of human-computer interaction and intelligent sensing technology, specifically to a tactile sensing feedback device and method based on piezoelectric thin films. Background Technology

[0002] Haptic technology is key to achieving natural human-computer interaction. In terms of tactile perception, existing technologies are mainly based on resistive, capacitive, piezoelectric, optical, and magnetic principles. In terms of tactile feedback, technologies such as eccentric rotor motors (ERM), linear resonant actuators (LRA), piezoelectric actuators, and ultrasonic tactile technologies are commonly used.

[0003] Among them, the piezoelectric technology of transparent conductive thin film materials is unique due to the positive and negative piezoelectric effects. It can simultaneously realize sensing (converting mechanical force into electrical signals) and feedback (converting electrical signals into mechanical motion), and has potential advantages such as direct physical relationship and fast response speed.

[0004] However, existing piezoelectric devices struggle to provide effective force feedback while maintaining both good piezoelectric properties and flexibility. They are also difficult to miniaturize and flexibly fabricate, which limits their application in compact, integrable tactile devices. Summary of the Invention

[0005] This invention provides a tactile sensing feedback device based on piezoelectric thin film. A bidirectional transducer unit is constructed by combining PZT thin film material with a common metal elastic strip. By utilizing the piezoelectric effect, structure, and mechanical properties of the transparent conductive thin film material, the sensing and feedback functions are integrated into one. The structure is simpler, the data processing volume is smaller, and the spatial and functional separation between the sensing module and the feedback module is eliminated. This improves the naturalness and realism of tactile interaction and solves the problems mentioned in the background art of balancing piezoelectric characteristics with flexibility, effective force feedback, and miniaturization and flexible processing.

[0006] This invention provides the following technical solution: A tactile feedback device based on a piezoelectric thin film includes: an elastic metal strip, the two ends of which are fixed to form a simply supported beam or a cantilever beam structure; a piezoelectric unit, including a first chip and a second chip, the first chip and the second chip being respectively disposed at both ends of the metal strip, and both the first chip and the second chip having a positive piezoelectric effect and an inverse piezoelectric effect; the metal strip and the first chip and the second chip having a first working mode and a second working mode; wherein, in the first working mode, external pressure is applied to any position of the metal strip, causing the metal strip to bend and deform, and the first chip and the second chip generate a first electrical signal and a second electrical signal proportional to the applied force through the positive piezoelectric effect; by collecting and comparing the first electrical signal and the second electrical signal, the magnitude of the pressure and the position of the point of application can be determined; in the second working mode, at least one driving voltage is applied to the first chip or the second chip, and the first chip and the second chip generate expansion and contraction deformation through the inverse piezoelectric effect, and transmit the expansion and contraction deformation to the metal strip, so that the metal strip generates tactile feedback.

[0007] As a preferred embodiment of the present invention, both the first chip and the second chip are PZT piezoelectric films, and the thickness of the PZT piezoelectric film is 1μm-1mm.

[0008] As a preferred embodiment of the present invention, the first chip and the second chip are mechanically and electrically connected to the metal strip by conductive adhesive or solder, and the polarization directions of the first chip and the second chip are perpendicular to the surface of the metal strip.

[0009] As a preferred embodiment of the present invention, the first chip and the second chip are symmetrically distributed along the center of the metal strip, and the electrodes of the first chip and the second chip are independently led out for acquiring signals or independently applying driving voltage.

[0010] As a preferred embodiment of the present invention, the first working mode is a sensing working mode, and the external pressure includes touch or pressing.

[0011] As a preferred embodiment of the present invention, the first electrical signal and the second electrical signal are voltage signals, charge signals or current signals. The first electrical signal and the second electrical signal are acquired by a signal processing circuit or control unit, and analyzed by calculating the difference, ratio or phase comparison of the first electrical signal and the second electrical signal.

[0012] As a preferred embodiment of the present invention, the second working mode is a feedback working mode, and the driving voltage is an AC voltage or a pulse voltage.

[0013] As a preferred embodiment of the present invention, the tactile feedback includes tactile effects that simulate button clicks, vibrations, or textures.

[0014] As a preferred technical solution of the present invention, the metal strip, the first chip and the second chip form a single basic module, which can be arranged and integrated in the form of a one-dimensional or two-dimensional array. The basic module performs tactile feedback on the surface tactile information by independent addressing and signal processing, and provides programmable tactile feedback.

[0015] One method includes the following steps: Step 1: Deposit a stack of PZT piezoelectric thin films on a silicon substrate. The stack of PZT piezoelectric thin films, from bottom to top, consists of a silicon substrate, a bottom electrode, a PZT piezoelectric thin film, and a top electrode. Step 2: Perform photolithography or etching on the top electrode, PZT piezoelectric film and bottom electrode sequentially from top to bottom, and deposit, photolithography or etch on the silicon substrate, so that the dimensions of the top electrode, PZT piezoelectric film, bottom electrode and silicon substrate are in an increasing order. Step 3: Perform photolithography, deposition, or stripping on the leads of the bottom and top electrodes; Step 4: Thin the side of the silicon substrate away from the bottom electrode.

[0016] Compared with the prior art, the present invention provides a tactile sensing feedback device and method based on piezoelectric thin film, which has the following beneficial effects: 1. In this tactile sensing feedback device based on piezoelectric thin film, a bidirectional transducer unit is constructed by using PZT thin film material and metal strip. By utilizing the piezoelectric effect of transparent conductive thin film material and the mechanical properties of the structure, the sensing and feedback functions are integrated. The tactile position signal is calculated by using the signal difference between the separated first chip and the second chip, realizing the sensing of continuous position in one dimension. Moreover, the structure is simpler and the data processing volume is smaller.

[0017] 2. In this tactile feedback device based on piezoelectric thin film, the transparency, conductivity and ultrathinness of PZT thin film material make the whole device more compact and small, overcoming the problem of difficulty in miniaturization. At the same time, the whole device is easy to expand into an array, which is convenient for developing thin, flexible and high-performance large-area electronic skin or tactile interaction interface.

[0018] The parts of this device not covered herein are the same as or can be implemented using existing technologies. This invention can achieve miniaturization while providing high sensitivity and effective stress feedback, thereby improving the naturalness and realism of tactile interaction. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, the elements or parts are not necessarily drawn to actual scale.

[0020] Figure 1 This is a schematic diagram of the main structure of the present invention; Figure 2 This is a schematic diagram showing the deformation of the first chip when the force of the present invention is applied; Figure 3 This is a schematic diagram showing the deformation of the second chip when the force of the present invention is applied; Figure 4 This is a schematic diagram showing the signal output sensed by the first chip and the second chip when the force is applied to different positions according to the present invention; Figure 5 This is a schematic diagram of the PZT piezoelectric thin film stack in this invention; Figure 6 This is a schematic diagram of the top electrode photolithography or etching in this invention; Figure 7 This is a schematic diagram of photolithography or etching of the PZT piezoelectric thin film in this invention; Figure 8 This is a schematic diagram of photolithography or etching of the bottom electrode in this invention; Figure 9 This is a schematic diagram of silicon substrate deposition, photolithography, or etching in this invention; Figure 10 This is a schematic diagram of the photolithography, deposition, or stripping of the top and bottom electrodes in this invention; Figure 11 This is a schematic diagram of silicon substrate thinning in this invention.

[0021] In the diagram: 1. Metal strip; 2. First chip; 3. Second chip. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1: Reference Figures 1-4A tactile feedback device based on a piezoelectric thin film includes: an elastic metal strip 1, with both ends of the metal strip 1 fixed to form a simply supported beam or cantilever beam structure. The metal strip 1 serves as the mechanical skeleton and force transmission medium of the entire device, possessing both elastic deformation and mechanical support functions. The fixed ends form specific mechanical boundary conditions, constituting a physical platform for macroscopic force-to-electric conversion. The two ends are mechanically constrained to an external substrate or frame. When an external force is applied to any position of the metal strip 1, the metal strip 1 undergoes elastic bending deformation. The amount of deformation is related to the magnitude of the external force, the position of application, the elastic modulus of the material, and the moment of inertia of the cross section. The fixed constraints at both ends ensure that the deformation energy is effectively transferred to the piezoelectric unit at the end, providing sufficient mechanical excitation for subsequent piezoelectric conversion. The elastic characteristics ensure that the device can respond repeatedly, realizing dynamic tactile interaction, and causing stress concentration at the end, thus optimizing the signal acquisition efficiency of the piezoelectric unit.

[0024] The piezoelectric unit includes a first chip 2 and a second chip 3. The first chip 2 and the second chip 3 are respectively disposed at both ends of the metal strip 1. The first chip 2 and the second chip 3 are attached to the surfaces of both ends of the metal strip 1 in a discrete unit structure. The first chip 2 and the second chip 3 both contain a microstructure of electrode-piezoelectric layer-electrode and have independent electrical ports. Different points of action lead to differences in strain distribution at both ends. Position information can be deduced by comparing signals. Simultaneous driving at both ends can generate a larger feedback force, while driving on one side can form an asymmetrical tactile effect.

[0025] Both the first chip 2 and the second chip 3 have positive and inverse piezoelectric effects. The metal strip 1 and the first chip 2 and the second chip 3 have a first working mode and a second working mode. When in the first working mode, external pressure is applied to any position of the metal strip 1, causing the metal strip 1 to bend and deform. The first chip 2 and the second chip 3 generate a first electrical signal and a second electrical signal that are proportional to the force through the positive piezoelectric effect. By collecting and comparing the first electrical signal and the second electrical signal, the magnitude of the pressure and the position of the point of application can be determined.

[0026] When a user presses their finger at any point on metal strip 1, the force is transmitted along the normal direction, metal strip 1 bends and redistributes, and strains of equal or opposite or proportional magnitude are generated at both ends. The strain acts on the first chip 2 and the second chip 3, the vector sum of the electric dipole moments changes, the surface bound charges are released, and the electrodes capture electrical signals. The ability to sense any position eliminates the need for precise alignment of the device, improving the user experience. The dual signal output contains both force magnitude and position information, enabling multi-dimensional information capture. The positive piezoelectric effect has an extremely fast response speed, supporting high-frequency dynamic force detection. The magnitude of the force is obtained by comparing the vector sum of the first and second electrical signals with the calibration curve. Continuous position detection can be achieved using only the first chip 2 and the second chip 3. Compared with traditional array sensor solutions, this significantly reduces hardware complexity and manufacturing costs, and requires less computation, enabling on-chip real-time processing, making it suitable for embedded applications.

[0027] When in the second working mode, at least one driving voltage is applied to the first chip 2 or the second chip 3. The first chip 2 and the second chip 3 generate expansion and contraction deformation through the inverse piezoelectric effect and transmit the expansion and contraction deformation to the metal strip 1, so that the metal strip 1 generates tactile feedback. The driving voltage causes the dipole orientation in the first chip 2 and the second chip 3 to change the macroscopic size. The first chip 2 and the second chip 3 and the metal strip 1 form a composite beam structure. The micro-strain of the piezoelectric layer is amplified into the macroscopic deflection of the overall structure through the elastic constraint of the metal strip 1. The feedback generation method is direct and efficient, without the need for additional mass blocks or complex transmission mechanisms. Programmable electrical signals can generate arbitrary waveforms, thereby simulating diverse tactile textures.

[0028] Reference Figure 1 Both the first chip 2 and the second chip 3 are PZT piezoelectric films. PZT piezoelectric films are transparent conductive film materials. Their high transparency makes them more sensitive in tactile feedback (such as mobile phone and car touch screens, generating vibration feedback at the fingertips). The thickness of the PZT piezoelectric film is 1μm-1mm, and the optimal thickness is 50μm. While ensuring that the PZT piezoelectric film has good capacitance characteristics, the rigidity of the PZT piezoelectric film is reduced, so that it can withstand bending deformation without breaking. Under the same force, it generates greater strain, improves sensing sensitivity, and is suitable for integration into devices. At the same time, it maintains sufficient mechanical reliability and avoids operational damage caused by excessive thinness.

[0029] The first chip 2 and the second chip 3 are mechanically and electrically connected to the metal strip 1 through conductive adhesive or solder. The polarization direction of the first chip 2 and the second chip 3 is perpendicular to the surface of the metal strip 1. The first chip 2 and the second chip 3 are symmetrically distributed along the center of the metal strip 1. The electrodes of the first chip 2 and the second chip 3 are independently led out for signal acquisition or independent application of driving voltage.

[0030] The conductive adhesive process is simple and cures at low temperatures, making it suitable for flexible substrates and transparent conductive film materials, avoiding high-temperature damage. The solder connection has high strength and low resistance, making it suitable for high-power drive scenarios. The dual-function integration simplifies the structure and improves reliability. The symmetrical structure ensures that the initial signals of the first chip 2 and the second chip 3 are consistent under zero load. Zero bias in the differential signal is automatically eliminated. When an external force is applied to the midpoint, the two signals have equal amplitude and phase, serving as the reference origin for position calculation. Symmetry ensures linearity and repeatability, simplifies the signal processing algorithm, eliminates the need for complex calibration, and the symmetrical structure provides balanced force, resulting in high long-term stability. Independent drive allows the generation of asymmetric vibration modes, such as unilateral click sensation, directional texture simulation, and other complex tactile expressions. Signal path separation improves measurement accuracy and enables high-resolution tactile perception.

[0031] Reference Figures 1-3 The first working mode is the perception working mode, which includes external pressure such as touch or press. It covers the main input methods of human-computer interaction, such as complete gesture recognition of click, drag, slide, long press, etc., and expands the application scenarios from button replacement to complex interfaces such as touchpad and virtual keyboard.

[0032] The first and second electrical signals can be voltage, charge, or current signals. They are acquired by a signal processing circuit or control unit, and analyzed by calculating the difference, ratio, or phase comparison between the first and second electrical signals. Charge signals are proportional to strain and are suitable for high-precision measurement; voltage signals are easy to transmit and process; current signals have a fast response speed; difference calculation highlights position information; ratio calculation eliminates the influence of force magnitude; phase analysis determines the direction of force application; the signal form is flexible and can be connected to different processing architectures; multiple algorithms provide redundant information; phase analysis expands the sensing dimension and supports multi-directional force detection.

[0033] Reference Figure 1 and Figure 4 The second working mode is a feedback working mode, with the driving voltage being AC voltage or pulse voltage. Tactile feedback includes simulating the tactile effects of button clicks, vibrations, or textures. AC voltage drives the PZT piezoelectric film into steady-state vibration. When the frequency approaches the structural resonance point, the amplitude amplifies, generating a strong vibration sensation. Pulse voltage excites transient responses, rapidly expanding and contracting to simulate the abrupt jump of a mechanical switch. AC voltage is suitable for simulating continuous textures (such as sandpaper, fabric textures, etc.), while pulse voltage is suitable for simulating discrete events (such as button presses, collisions, etc.). The voltage waveform is programmable, and complex tactile experiences are synthesized by modulating the frequency, amplitude, and phase. The confirmation feel of mechanical buttons is reproduced on a flat, featureless touchscreen, facilitating blind operation. Vibration warning provides a non-visual information channel. Textures give virtual objects material recognition, enhancing the immersive experience of virtual reality.

[0034] Reference Figure 1Metal strip 1, first chip 2 and second chip 3 form a single basic module, which can be arranged and integrated in the form of a one-dimensional or two-dimensional array. The basic module can perceive surface tactile information at high resolution and large area through independent addressing and signal processing, and provide partitioned and programmable tactile feedback.

[0035] Each basic module independently senses local force information, scans and reads signals from each unit, the central processing unit fuses data from multiple units, reconstructs the multi-point touch distribution and force field map, and drives the corresponding units to generate feedback. The array spacing design ensures no blind spots. Independent addressing is based on a row and column selection mechanism to avoid complex wiring. The array covers a large surface area, meeting the application needs of tablets, automotive central control screens, and robot electronic skins. Partitioned feedback enables precise interaction. Independent addressing is switched through a multiplexer, activating one or a row of basic modules at a time. Signal processing includes parallel sampling, analog-to-digital conversion, and digital filtering. Programmable feedback is achieved through stored waveforms, enabling real-time recall. High resolution supports detailed force distribution measurement, such as fingerprint pattern recognition. Large-area sensing adapts to ergonomic curved surfaces. Programmability allows the same hardware platform to achieve different interaction paradigms through software updates, extending the product lifecycle.

[0036] Example 2: Reference Figures 5-10 Based on Embodiment 1, a method is proposed for fabricating the first chip 2 and the second chip 3, comprising the following steps: Step 1: Deposit a stack of PZT piezoelectric thin films on a silicon substrate. The stack of PZT piezoelectric thin films, from bottom to top, consists of a silicon substrate, a bottom electrode, a PZT piezoelectric thin film, and a top electrode. A four-level stacked structure is formed, with the silicon substrate providing mechanical support and a process platform. The silicon substrate is matched with the PZT piezoelectric film, and the process is compatible with integrated circuit manufacturing. It supports wafer-level mass production, has controllable costs, and the PZT piezoelectric film has good quality uniformity and high device consistency.

[0037] Step 2: Perform photolithography or etching on the top electrode, PZT piezoelectric film and bottom electrode sequentially from top to bottom, and deposit, photolithography or etch on the silicon substrate, so that the dimensions of the top electrode, PZT piezoelectric film, bottom electrode and silicon substrate are in an increasing order. The top electrode has the smallest area, completely covering the effective area of ​​the PZT piezoelectric film; the PZT piezoelectric film is slightly larger than the top electrode; the bottom electrode is even larger, extending into the lead area; the silicon substrate has the largest size, providing complete support. The increasing size prevents short circuits between the top and bottom electrodes on the sidewalls, ensuring electrical isolation. The stepped structure improves the uniformity of the sidewall passivation layer coverage, preventing electrode corrosion and ion contamination. The self-alignment process simplifies alignment difficulty and improves yield. The three-dimensional steps enhance device reliability and prevent electrical breakdown during operation.

[0038] Step 3: Perform photolithography, deposition, or stripping on the leads of the bottom and top electrodes; The stripping process utilizes the slope structure of the photoresist to break the metal at the edge of the photoresist, achieving selective metal patterning; deposited metal serves as a conductive path, connecting the electrodes and package pins, separating the lead area from the functional area process, avoiding damage to the functional area from the lead process, and the large pad area can reduce contact resistance, improve the reliability of electrical connections, and support multiple packaging forms.

[0039] Step 4: Thin the side of the silicon substrate away from the bottom electrode.

[0040] After thinning, the thickness of the silicon substrate is reduced from hundreds of micrometers to tens of micrometers, forming a thin film that can be bent without breaking. Thinning reduces the bending stiffness of the silicon substrate, allowing it to fit curved surfaces. At the same time, it reduces the overall thickness, reduces stress concentration after mounting, and also improves thermal response speed and temperature characteristics. It combines high performance and flexibility, reduces mass, improves vibration efficiency, and can withstand greater strain without failure.

[0041] Components not described in detail in this article are existing technologies.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A tactile feedback device based on a piezoelectric thin film, characterized in that, include: A flexible metal strip (1) with both ends fixed to form a simply supported beam or cantilever beam structure; The piezoelectric unit includes a first chip (2) and a second chip (3), the first chip (2) and the second chip (3) are respectively disposed at both ends of a metal strip (1), and the first chip (2) and the second chip (3) both have positive piezoelectric effect and inverse piezoelectric effect. The metal strip (1) and the first chip (2) and the second chip (3) have a first working mode and a second working mode. When in the first working mode, external pressure is applied to any position of the metal strip (1), causing the metal strip (1) to bend and deform. The first chip (2) and the second chip (3) generate a first electrical signal and a second electrical signal that are proportional to the force through the positive piezoelectric effect. By collecting and comparing the first electrical signal and the second electrical signal, the magnitude of the pressure and the position of the point of application can be determined. When in the second working mode, at least one driving voltage is applied to the first chip (2) or the second chip (3). The first chip (2) and the second chip (3) generate stretching deformation through the inverse piezoelectric effect and transmit the stretching deformation to the metal strip (1) so that the metal strip (1) generates tactile feedback.

2. The tactile feedback device based on a piezoelectric thin film according to claim 1, characterized in that, The first chip (2) and the second chip (3) are both PZT piezoelectric films with a thickness of 1μm-1mm.

3. The tactile feedback device based on a piezoelectric thin film according to claim 1, characterized in that, The first chip (2) and the second chip (3) are mechanically and electrically connected to the metal strip (1) through conductive adhesive or solder, and the polarization direction of the first chip (2) and the second chip (3) is perpendicular to the surface of the metal strip (1).

4. A tactile feedback device based on a piezoelectric thin film according to claim 1, characterized in that, The first chip (2) and the second chip (3) are symmetrically distributed along the center of the metal strip (1), and the electrodes of the first chip (2) and the second chip (3) are independently led out for acquiring signals or independently applying driving voltage.

5. A tactile feedback device based on a piezoelectric thin film according to claim 1, characterized in that, The first working mode is a sensing working mode, and the external pressure includes touch or pressing.

6. A tactile feedback device based on a piezoelectric thin film according to claim 1, characterized in that, The first electrical signal and the second electrical signal are voltage signals, charge signals, or current signals. The first electrical signal and the second electrical signal are acquired by a signal processing circuit or control unit, and analyzed by calculating the difference, ratio, or phase comparison between the first electrical signal and the second electrical signal.

7. A tactile feedback device based on a piezoelectric thin film according to claim 1, characterized in that, The second operating mode is a feedback operating mode, and the driving voltage is an AC voltage or a pulse voltage.

8. A tactile feedback device based on a piezoelectric thin film according to claim 1, characterized in that, The haptic feedback includes tactile effects that simulate button clicks, vibrations, or textures.

9. A tactile feedback device based on a piezoelectric thin film according to claim 8, characterized in that, The metal strip (1), the first chip (2), and the second chip (3) form a single basic module, which can be arranged and integrated in the form of a one-dimensional or two-dimensional array. The basic module performs tactile feedback on the surface through independent addressing and signal processing, and partitions the surface tactile information.

10. A method for fabricating a piezoelectric unit according to any one of claims 1-9, comprising the following steps: Step 1: Deposit a stack of PZT piezoelectric thin films on a silicon substrate. The stack of PZT piezoelectric thin films, from bottom to top, consists of a silicon substrate, a bottom electrode, a PZT piezoelectric thin film, and a top electrode. Step 2: Perform photolithography or etching on the top electrode, PZT piezoelectric film and bottom electrode sequentially from top to bottom, and deposit, photolithography or etch on the silicon substrate, so that the dimensions of the top electrode, PZT piezoelectric film, bottom electrode and silicon substrate are in an increasing order. Step 3: Perform photolithography, deposition, or stripping on the leads of the bottom and top electrodes; Step 4: Thin the side of the silicon substrate away from the bottom electrode.

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