FIELD OF THE DISCLOSURE

The instant disclosure relates to materials. More specifically, this disclosure relates to piezoelectric materials, and their uses in electronic devices as input devices.

BACKGROUND

Interaction with electronic devices, such as computers, home appliances, or car consoles, has been characterized by the use of mechanical switches (keyboard, buttons, knobs, etc.) as the input mechanism for the given system to perform an action. An on/off switch in many appliances is a mechanical switch that lets current flow through it when pressed but presents a large resistance to current flow when not pressed. Switches are used in computer keyboards which users apply force to enter the desired letter. Some recent developments incorporate the use of touch sensitive technology to replace the mechanical switches. Capacitive, resistive, or optical-based proximity or touch sensors are being used to replace mechanical switches and knobs, such as found in a car's console. Touch-sensitive displays are embedded into systems like mobile phones, tablets, or even ATM machines. However, the conventional touch-sensitive technologies have a major drawback in that there is a lack of sense of touch for the user. That is, a user cannot feel operation of the device like a mechanical switch.

Piezoelectric materials are one of the recent materials being used in various applications in the area of sensors and actuators. Conventional piezoelectric materials include ferroelectric ceramics, such as Barium Titanate (BT) and Lead Zirconium Titanate (PZT). Other conventional piezoelectric materials include polymers, such as polyvinylidene fluoride (PVDF) and its copolymers. Although these conventional materials have been used in a wide range of piezoelectric applications, these materials have undesirable trade-offs. Thus, a combination of conventional materials can be required to obtain desired properties. The trade-off is between a desire for high piezoelectric activity, low density, and mechanical flexibility. High piezoelectric activity is desirable to increase the sensitivity of sensors that use a piezoelectric material, and thus improve a user's experience. Mechanical flexibility is desirable to allow construction of thin and/or wearable devices. However, with conventional materials obtaining mechanical flexibility requires trading-off piezoelectric activity.

SUMMARY

Embodiments of the disclosure provide a polyoxymethylene (POM)-based composite polymer thin film with enhanced piezoelectric performance even with a very low loading of piezoelectric additives. The composite thin film can be used in piezoelectric-based sensors. The POM-based composite can be mechanically flexible to allow for assembly of mechanically-flexible sensor modules and electronic devices. The polymer composite thin film exhibiting piezoelectric properties may include a polymer matrix, in which the polymer matrix comprises polyoxymethylene (POM); and a piezoelectric additive comprising greater than approximately five (5) percent by weight of the polymer composite thin film, between five (5) and thirty percent by weight of the polymer composite thin film, or greater than thirty (30) percent by weight of the polymer composite thin film. Below five (5) percent by weight, the value of d33 for the composite thin film is not significant enough to be of commercial value as a piezoelectric material. In some embodiments, the polymer composite thin film comprises inorganic Perovskites, processing aids, dispersing aids and heat stabilizers, antioxidants, flow modifiers and plasticizers. In some embodiments, the polymer composite thin film has a thickness of between 30 and 120 micrometers. Composites with low loading (e.g., 1-20%) of inorganic ferroelectric ceramics (e.g., BaTiO3BT, PZT, etc.) provide a molecular structure of POM in synergy with low loading of piezoelectric ceramics to provide a good combination of piezoelectric performance with mechanical flexibility that opens the scope for broadening applications of conventional piezoelectric composites.

The piezoelectric additive may be an inorganic material, such as one or more of Lithium-doped Potassium Sodium Niobate Rubidium-doped Potassium Sodium Niobate, Caesium-doped Potassium Sodium Niobate, and undoped Potassium Sodium Niobate (KNN). In some embodiments, the piezoelectric additive comprises an inorganic additive comprising of doped Potassium Sodium Niobate (KNN) or undoped Potassium Sodium Niobate (KNN) in combination with at least one of PZT-Lead Zirconium Titanate, BT-Barium Titanate, and Zinc Oxide. In some embodiments, the piezoelectric additive comprises Potassium Sodium Niobate (KNN), and wherein the piezoelectric additive comprises between thirty-five (35) and ninety-eight (98) percent by weight of the polymer composite film. In some embodiments, the piezoelectric additive comprises Potassium Sodium Niobate (KNN) in combination with Lithium, and wherein the piezoelectric additive comprises between thirty-five (35) and ninety-eight (98) percent by weight of the polymer composite film. In some embodiments, the piezoelectric additive comprises at least one of a zero-dimensional, and one-dimensional structural pattern and a two-dimensional structural pattern. Example zero-dimensional structures include quantum dots, arrays of nanoparticles, core-shell nanoparticles, hollow cubes and nanospheres, one-dimensional. Examples of two-dimensional structures include nanowires, nanorods, nanotubes, nanobelts, nanoribbons and nanoplates, nanosheets, nanowalls, and nanodisks. Example three-dimensional structures include nanoballs, nanocoils, nanocones, and nanopillars. Varying dimensional structures exhibit different properties based on surface area, interaction with materials, dispersion within the matrix, and inter-particle interaction.

Such materials, of which some embodiments are listed above, provide improvements in user interaction with electronic devices for receiving user input and user feedback. As non-limiting examples, the materials may be used in electronic devices such as light switches or consumer smartphones to interact with users. Additional uses for such materials include bio-diagnostics, nano- and micro-electromechanical systems, imaging, sensors, actuators, and electronics. When POM-based polymer composite thin films are used in piezoelectric-based sensors, the sensors may generate an analog signal proportional to an amount of deflection applied to the piezoelectric sensor by a user. In any electronic device, the thin film materials may be patterned through microfabrication techniques including electron beam lithography, ion milling, soft lithography, self-assembly, electrospinning, and contact printing.

The POM-based composite polymer thin film can be manufactured by physical mixing of polyoxymethylene (POM) powder with the piezoelectric additive in proportions w/w percentage of the piezoelectric additive to the polyoxymethylene (POM). The manufacturing may also include melt-blending in an extruder the polyoxymethylene (POM) powder with the piezoelectric additive to form pellets of a polymer composite and/or compression molding by hot-pressing the pellets to form the polymer composite thin film at a temperature exceeding 150 degrees Celsius. The manufacturing may also include physical mixing followed by a heat sintering step to form a pellet or thin film for further processing.

The piezoelectric-based sensor or apparatus may execute steps to facilitate the processing and transmission of user input received at the triboelectric-based sensor. A processor, or other logic circuitry, may be configured through hardware, software, and/or firmware to execute steps including receiving, at a triboelectric-based sensor of a touch device, an applied force; converting, at the triboelectric-based sensor of the touch device, the applied force to an electric signal; transmitting, by the triboelectric-based sensor of the touch device, the electric signal to logic circuitry, such as an application processor; generating by the logic circuitry, a haptic feedback signal in response to and/or based on the electric signal; and/or outputting the haptic feedback signal to a haptic feedback device.

The foregoing has outlined rather broadly certain features and technical advantages of embodiments of the present invention in order that the detailed description that follows may be better understood. Additional features and advantages will be described hereinafter that form the subject of the claims of the invention. It should be appreciated by those having ordinary skill in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same or similar purposes. It should also be realized by those having ordinary skill in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. Additional features will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended to limit the present invention.

