CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Applications Number 62/576,934, filed October 25, 2017, and 62/658,165, filed April 16, 2018, each entitled "Triboelectric Thin Film Transistor Based Voltage Controlled Resistor for Force Sensing and Weight Balance", the disclosure of each of which is hereby incorporated herein by reference as if reproduced in its entirety.

TECHNICAL FIELD

[0002] This disclosure relates to an electronic weight balance or 'force measuring system' that includes a triboelectric sensor in combination with a transistor.

BACKGROUND

[0003] Weight scales are of great interest due to use thereof in various applications in daily life. There are two types of weight measuring systems commercially available in the market: mechanical and electronic weight balance systems. The majority of conventional weight scales are mechanical and use metallic springs and gears, which make them bulky. These spring-based weight scales possess eccentric errors due to the fixed position of the springs. Moreover, mechanical weight scales are not capable of measuring low range weights due to the low sensitivity thereof. The repeatability performance of these weight scales is also a challenge due to the degradation of spring performance.

[0004] Commercially available electronic weight scales are classified into two types: (i) electromagnetic based, and (ii) load cell type (electrical resistance based). The electromagnetic based weight balance uses magnets and coils, and thus has a complex structure, is bulky, and consumes high power. On the other hand, an electrical resistance wire type weight balance has low accuracy and low long-term reliability due to the use of an elastic body to expand the resistance wire.

[0005] Mechanical weight scales that use springs and gears do not require electric power for operation, and can be used for heavy weights. Electromagnetic type scales use magnets and coils, provide higher accuracy, and are used for analytical balance. Load cell type scales use wire type resistance, and have a simple structure and small size.

[0006] Despite the widespread use of conventional scales, incumbent weight balances have several disadvantages. For example, mechanical weight scales tend to be bulky, heavy and inaccurate, and provide low sensitivity. Electromagnetic type scales have a complex structure, exhibit high power consumption, and tend to be difficult to downsize. Load cell type scales have limited accuracy, low long-term reliability, and are applicable for medium to heavy weights.

[0007] According to this disclosure, an electrical weight balance based on triboelectric and thin film transistors, which can be developed on a flexible substrate, can be utilized as a force measuring system.

SUMMARY

[0008] Herein disclosed is a force measuring system comprising: a triboelectric sensor; a thin film transistor (TFT) operably coupled to the triboelectric sensor such that an output voltage of the triboelectric sensor, which depends on the force applied to it, can be used as a gate voltage (V _G ) received by a gate of the TFT; and a device (e.g., a processor) configured to measure an output of the thin film transistor and calculate a force being applied to the triboelectric sensor.

[0009] Also disclosed herein is a method of measuring force applied to a triboelectric sensor, the method comprising: applying a force to a triboelectric sensor, the force generating a triboelectric output voltage; utilizing the triboelectric output voltage to control a channel resistance (R _CH ) of a thin film transistor as a voltage-controlled resistor (VCR); passing the output of the thin film transistor to a device configured to measure voltage (e.g., a voltage measuring device); and applying an algorithm to convert the voltage to a force measurement.

[0010] Also disclosed herein is an electronic force system comprising: a triboelectric sensor configured to: receive a force, and provide an output voltage based on the force; and a transistor coupled to the triboelectric sensor and comprising: a gate configured to receive the output voltage as a gate voltage (V _G ), a source configured to provide a source voltage (Vs), and a channel resistance (R _CH ) based on a gate-to-source voltage (V _GS ), wherein V _GS is a difference between V _G and Vs.

[0011] Also disclosed herein is an electronic force system comprising: a substrate layer; a transistor comprising: a gate electrode layer disposed on top of the substrate layer, a gate insulator layer disposed on top of a first portion of the gate electrode layer, a semiconductor layer disposed on top of the gate insulator layer, a source electrode layer disposed on top of a first portion of the semiconductor layer, and a drain electrode disposed on top of a second portion of the semiconductor layer; and a triboelectric layer disposed on top of a second portion of the gate electrode layer.

[0012] Other embodiments are discussed throughout this application. Any embodiment discussed with respect to one aspect or embodiment applies to other aspects of this disclosure as well and vice versa. Each embodiment described herein is understood to be an embodiment that is applicable to other aspects or embodiments. It is contemplated that any embodiment discussed herein can be implemented with respect to any method or composition of this disclosure, and vice versa. Furthermore, systems and apparatus of this disclosure can be used to achieve methods of the disclosure. [0013] The following includes definitions of various terms and phrases used throughout this specification.

[0014] The terms "about" or "approximately" are defined as being close to as understood by one of ordinary skill in the art. In one non-limiting embodiment, the terms are defined to be within 10%, within 5%, within 1%, or within 0.5%.

[0015] The terms "wt.%", "vol.%", or "mol.%" refers to a weight percentage of a component, a volume percentage of a component, or molar percentage of a component, respectively, based on the total weight, the total volume of material, or total moles, that includes the component. In a non-limiting example, 10 grams of component in 100 grams of the material is 10 wt.% of component.

[0016] The term "substantially" and its variations are defined to include ranges within 10%, within 5%, within 1%, or within 0.5%.

[0017] The terms "inhibiting" or "reducing" or "preventing" or "avoiding" or any variation of these terms, when used in the claims and/or the specification includes any measurable decrease or complete inhibition to achieve a desired result.

[0018] The term "effective," as that term is used in the specification and/or claims, means adequate to accomplish a desired, expected, or intended result.

[0019] The use of the words "a" or "an" when used in conjunction with any of the terms "comprising," "including," "containing," or "having" in the claims, or the specification, may mean "one," but it is also consistent with the meaning of "one or more," "at least one," and "one or more than one."

[0020] The words "comprising" (and any form of comprising, such as "comprise" and "comprises"), "having" (and any form of having, such as "have" and "has"), "including" (and any form of including, such as "includes" and "include") or "containing" (and any form of containing, such as "contains" and "contain") are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0021] The words "connected," "coupled," and the like include both direct (e.g., two components coupled directly, e.g., 1 to 1) or indirect (e.g., two components coupled via one or more additional components) configurations of components.

[0022] The force measuring system of the present disclosure can "comprise," "consist essentially of," or "consist of particular ingredients, components, compositions, etc. disclosed throughout the specification. For example, the force measuring system of the present disclosure can comprise a triboelectric sensor in combination with a transistor and a device configured to measure the output of the thin film transistor to determine a weight.

[0023] Other objects, features and advantages of the present disclosure will become apparent from the following figures, detailed description, and examples. It should be understood, however, that the figures, detailed description, and examples, while indicating specific embodiments, are given by way of illustration only and are not meant to be limiting. Additionally, it is contemplated that changes and modifications within the spirit and scope of this disclosure will become apparent to those skilled in the art from this detailed description. In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The following figures illustrate exemplary embodiments of the subject matter disclosed herein. The claimed subject matter may be understood by reference to the following description taken in conjunction with the accompanying figures, and in which:

[0025] FIG. 1 is a schematic of a circuit diagram of a triboelectric TFT-based electronic weight balance, according to an embodiment of this disclosure;

[0026] FIG. 2A is a cross-section view of a triboelectric (TE) sensor 20A integrated with a bottom gate TFT 30A for use in a triboelectric TFT-based electronic weight balance, according to an embodiment of this disclosure;

[0027] FIG. 2B is a cross-section view of a top gate TFT suitable for use in a voltage controlled resistor (VCR) for use in a triboelectric TFT-based electronic weight balance, according to an embodiment of this disclosure;

[0028] FIG. 2C is a plan view of the bottom gate TFT 3 OA of the voltage controlled resistor (VCR) of Figure 2A;

[0029] FIG. 3 is a schematic of a weight balance with wireless communication, according to an embodiment of this disclosure; and

[0030] FIG. 4 is a plot of the results, in Example 1, of weight measurement using a triboelectric sensor 20 as per this disclosure.

[0031] While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings. The drawings may not be to scale. DETAILED DESCRIPTION

[0032] Herein described is a thin film transistor (TFT) integrated with a triboelectric layer that can be utilized as a force sensor and electronic weight balance. The triboelectric (TE) phenomena relies on contact electrification. As the magnitude of output voltage generated from the triboelectric sensor depends on the force applied on it, different levels of voltage can be generated by applying different magnitudes of force or weight, which can be used to control the output or channel resistance of a TFT, which is known as voltage controlled resistor (VCR). The change in channel resistance RCH of the VCR can be translated to the applied force or weight applied on it and hence the integration of a thin film transistor (TFT) with a triboelectric layer, as per this disclosure, can be useful as a weight balance or 'force measuring system'. In embodiments, a weight balance utilizing this technology can be portable, seamless and/or low cost. Since this technology involves field-effect transistors, the sensitivity and accuracy of the weight balance can be high and can be used, in embodiments, for very low range weights (e.g., less than or equal to about 0.8, 0.9, or 1 kg).

[0033] In embodiments, both the TE and TFT devices can be fabricated on a flexible substrate. In embodiments, a weight scale as per this disclosure comprises no mechanical parts. Thus, in embodiments, the force sensor and weight balance using the TE/transistor technology according to this disclosure can be portable, lightweight and/or low cost. Further, as the force-sensing element comprises field effect TFTs, in embodiments, the sensitivity and accuracy of the device may be high compared to devices employing conventional technology.

[0034] As discussed in detail hereinbelow, in embodiments, a force measuring system according to this disclosure can include a triboelectric sensor, a thin film transistor operably coupled to the triboelectric sensor, and a device configured to measure the output of the thin film transistor and calculate a force being applied to the triboelectric sensor.

[0035] Also disclosed herein is a method of measuring force applied to a triboelectric sensor. The method can include applying a force to a triboelectric sensor such that the forces generates a voltage, passing the voltage through a thin film transistor, passing an output from the thin film transistor to a device configured to measure voltage, and applying an algorithm to convert the voltage to a force measurement.

[0036] Herein disclosed is an electronic force measuring system. In embodiments, the force being measured is a weight of an object. In embodiments, the force measuring system comprises: a triboelectric (TE) sensor; a thin film transistor (TFT) operably coupled to the triboelectric sensor such that an output voltage of the triboelectric sensor, which depends on the force applied to it, can be used as a gate voltage (VG) received by a gate of the TFT. In embodiments, the force measuring system further comprises a device configured to measure an output of the thin film transistor and calculate a force being applied to the triboelectric sensor. It should be understood that although described hereinbelow as a thin film transistor, a conventional (e.g., silicon-based) transistor can be employed, in embodiments.

[0037] A force measuring system of this disclosure will now be described with reference to Figure 1 , which is a schematic of a circuit diagram of a triboelectric TFT-based electronic weight balance or 'force measuring system' I, according to an embodiment of this disclosure. Force measuring system I comprises triboelectric sensor 20 and transistor 30. Transistor 30 (indicated in Figure 1 by gate voltage (VG), drain voltage (VD), and source voltage (Vs)) is coupled with TE sensor 20, such that the output voltage of the triboelectric sensor, which depends on the force applied to it, can be used as a gate voltage (VG) received by a gate of the TFT 30. Use of the output voltage of the triboelectric sensor 20 as the gate voltage (VG) of the TFT 30 enables control of the output or channel resistance (RCH) of the thin film transistor as a voltage controlled resistor (VCR) (indicated via dotted section 10 in Figure 1), wherein RCH is based on a gate-to-source voltage (VGS) which is a difference between the gate voltage (VG) and a source voltage (Vs) of the TFT 30. The VCR 10 can comprise a sensing unit 11 comprising TE sensor 20 and resistor Rl and configured to provide the output voltage utilized as the gate voltage (VG) by TFT 30 of a read-out circuit 12 comprising TFT 30 and resistor R2.

[0038] The voltage across resistor Rl depends on the force exerted on the triboelectric material of triboelectric sensor 20. By utilizing this voltage to alter the gate-to-source voltage (VGS) of transistor 30, which can detect a minor change in voltage with high sensitivity, the voltage can be scaled up or amplified. By utilizing a TFT 30, in embodiments, the voltage can be scaled up or amplified utilizing a low power supply. In embodiments, the herein-disclosed force measuring system is utilized as a weight balance or scale. The components of the TB sensor 20 (e.g., thickness and dimension of triboelectric layer 21 described hereinbelow with reference to Figure 2A) and transistor or TFT 30 (e.g., amplification of TB sensor output voltage VG provided thereby) can be adjusted to provide a weight balance or scale configured to measure weights in the range of up to (i.e., less than or equal to) about 0.8, 0.9, 1, 2, 3, 4 or 5 kilograms, in embodiments.

[0039] The device configured to measure the output of the thin film transistor 30 and calculate a force being applied to the triboelectric sensor 20 can comprise any electronic circuit or a processor coupled to the TFT and configured to determine the force based on a change in the channel resistance RCH due to application of the force to the triboelectric sensor 20. As indicated in the force measuring system I of Figure 1 , in embodiments, the device comprises a processing unit or 'processor' 40. The force measuring system can further comprise a screen display 60 and/or a power supply (e.g. battery), as indicated as V _supp i _y 50 in the embodiment of Figure 1.

[0040] Figure 2A is a cross-section view of a VCR 1 OA comprising TE sensor 20A integrated with a TFT 3 OA for use in a triboelectric TFT-based electronic weight balance, according to an embodiment of this disclosure. In embodiments, the triboelectric sensor 20 comprises an active triboelectric layer and a substrate separated by an electrode. The active triboelectric layer can be a thin film comprising a polymer exhibiting a triboelectric effect, based on contact electrification, wherein the magnitude of the output voltage generated by the triboelectric layer depends on the force applied thereto. In the embodiment of Figure 2A, TE sensor 20A comprises active triboelectric layer 21 and TE substrate 25, separated by bottom electrode 22.

[0041] In embodiments, any polymer exhibiting triboelectric effect can be used as the active layer for triboelectric voltage generation. In embodiments, a triboelectric thin film (e.g., triboelectric thin film layer 21) for the triboelectric-based sensor (e.g., TE sensor 20A) comprises a perfluorinated copolymer, or other statistical copolymer, synthesized by free radical polymerization in benzene. In embodiments, the triboelectric thin film has been modified to increase a friction coefficient, such as by forming a plurality of pillars, either similarly- or differently-sized and shapes, on the thin film. In embodiments, the perfluorinated copolymer comprises poly(methyl methacrylate)-co-poly(lH-lH-perfluoroctyl methacrylate). In embodiments, the perfluorinated copolymer has a molecular weight in the range of from about 10,000 to about 50,000 g/mol and a dispersion ratio in the range of about 1.5 to about 2.5. In embodiments, the perfluorinated copolymer has a controlling perfluoro segment in proportion by weight of more than approximately fifty percent. [0042] In embodiments, the active tnboelectric layer of the TE sensor comprises an electronegative tnboelectric layer. In embodiments, the active triboelectric layer of the TE sensor comprises an electropositive triboelectric layer. In embodiments, the active triboelectric layer of the TE sensor comprises an electronegative triboelectric layer, and the electronegative triboelectric layer comprises PVDF, a copolymer of polyvinylidene difluoride (PVDF) (e.g., polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE), Vinylidene fluoride-trifluoroethylene- chlorofluoroethylene terpolymer (PVDF-TrFE CFE), and poly(vinylidene fluoride-co- hexafluoropropylene) (PVDF-HFP)), polydimethylsiloxane (PDMS), poly(methyl methacrylate) (PMMA), polytetrafluoroethylene (Teflon), polymer foams, poly(methyl methacrylate)-co- poly(lH-lH-perfluoroctyl methacrylate), fluorinated polymers, other electronegative polymers, or combinations thereof. In embodiments, the active triboelectric layer of the TE sensor comprises an electropositive triboelectric layer, and the electropositive triboelectric layer comprises acetate, mica, nylon, other electropositive polymers, or a combination thereof.

[0043] The force measuring system of this disclosure further comprises a thin film transistor 30. In embodiments, the TFT comprises an active layer of the thin film transistor, a source electrode, a drain electrode, a gate dielectric (or 'insulator') layer, a gate electrode, and a substrate. For example, the TFT 30A of Figure 2A comprises an active layer 33 of the thin film transistor, a source electrode 32A, a drain electrode 32B; a gate dielectric layer 34, a gate electrode 32C, and a substrate 35. In the embodiment of Figure 2A, TFT 3 OA is shown as a bottom gate TFT, wherein gate electrode 32C is positioned atop the TFT substrate 35, gate insulator or 'gate dielectric' 34 is positioned atop gate electrode 32C, TFT active (or 'semiconductor') layer 33 is positioned atop gate dielectric or gate insulator 34, and source and drain electrodes 32A and 32B are positioned on opposite sides atop the active (or 'semiconductor') layer 33 to provide channel C. Alternatively, in embodiments, the TFT can be configured as a top gate TFT, as indicated in the embodiment of Figure 2B, which is a cross-section view of a top gate TFT 30B suitable for use in a triboelectric TFT-based electronic weight balance, according to an embodiment of this disclosure. In the embodiment of Figure 2B, TFT active (or 'semiconductor') layer 33 is positioned atop TFT substrate 35, source and drain electrodes 32A and 32B are positioned on opposite sides atop the active (or 'semiconductor') layer 33 to provide channel C, with gate insulator or 'gate dielectric' 34 positioned atop and between source and drain electrodes 32A and 32B, and gate electrode 32C positioned atop gate dielectric or gate insulator 34.

[0044] As indicated in Figure 2C, which is a plan view of the bottom gate TFT 3 OA of embodiment of Figure 2A, the TFT active (or 'semiconductor') layer 33 may have a width W and a length L within channel C. The width W and length L of the channel may have any suitable dimensions, for example, the micrometer size range.

[0045] In embodiments, the active layer of the thin film transistor comprises at least one organic or inorganic semiconductor thin film. Any suitable organic or inorganic semiconductor thin film can be utilized. In embodiments, the active layer of the thin film transistor comprises a thin film of pentacene, poly(3-hexylthiophene-2,5-diyl (P3HT), zinc oxide (ZnO), indium gallium zinc oxide (InGaZnO), tin dioxide (Sn0 ₂ ), tin monoxide (SnO), indium oxide (ln ₂ 0 ₃ ), indium zinc oxide (IZO), zinc tin oxide (ZTO), or a combination thereof.

[0046] In embodiments, the gate dielectric layer (or other barrier layer) comprises an insulator. Any suitable insulator can be utilized. In embodiments, the insulator is selected from aluminum oxide, (A1 ₂ 0 ₃ ), titanium dioxide (Ti0 ₂ ), hafnium oxide (Hf0 ₂ ), silicon dioxide (Si0 ₂ ), silicon nitride (SiN _x ), zirconium oxide, polymer dielectrics such as poly(vinyl pyrrolidone) (PVP), polyvinyl acetate) (PVAc), PVDF-TrFE, P(VDF-TrFE-CTFE) Polyimide, PMMA, CYTOP or combinations thereof.

[0047] In embodiments, the triboelectric sensor and the TFT of the herein-disclosed force measuring system share a common substrate, a common electrode, or both. For example, in the embodiment of Figure 2A, the TE sensor 20A and the TFT 3 OA comprise a common electrode (e.g., the bottom electrode 22 of TE sensor 20A is the same as the gate electrode 32C of TFT 30A) and a common substrate (e.g., the TE substrate 25 of TE sensor 20A is the same as the TFT substrate 35 of TFT 30A). In alternative embodiments, the triboelectric sensor and the TFT (or other, e.g. silicon, transistor) can be fabricated independently and interconnected to perform the same function.

[0048] In embodiments, the common substrate, the substrate of the TE sensor (e.g., TE substrate 25 of the embodiment of Figure 2A), the substrate of the TFT (e.g., TFT substrate 35 of the embodiment of Figures 2A and 2B), or both comprise polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), poly(methyl methacrylate) (PMMA), polyimide, parylenes (e.g., Parylene C), other thermoplastic materials, or a combination thereof. In embodiments, the common substrate, the TE sensor, the TFT, the TE substrate, the TFT substrate, or a combination thereof is flexible or rigid (e.g., glass, silicon etc.). In embodiments, the common substrate, the TE sensor, the TFT, the TE substrate, the TFT substrate, or a combination thereof is flexible (e.g., as defined by the ability of a material to deform elastically and return to its original shape when the applied stress is removed without losing the functionality of the sensor and/or transistor). In embodiments, the common substrate, the TE sensor, the TFT, the TE substrate, the TFT substrate, or a combination thereof is not flexible, i.e., is substantially rigid. In embodiments, the common substrate, the TE sensor, the TFT, the TE substrate, the TFT substrate, or a combination thereof is at least partially transparent.

[0049] In embodiments, the electrode of the triboelectric sensor (e.g., TE bottom electrode 22 of the embodiment of Figure 2A), the gate electrode of the TFT (e.g., gate electrode 32C of the embodiment of Figures 2A and/or 2B), the drain electrode of the TFT (e.g., drain electrode 32B of the embodiment of Figures 2A and/or 2B), the source electrode of the TFT (e.g., source electrode 32A of the embodiment of Figures 2A and/or 2B), the common electrode (e.g., common electrode 22/32C of the embodiment of Figure 2A), or a combination thereof comprises conducting metals or transparent conducting oxides, such as Al, Ti, Cr, Au, indium tin oxide (ITO), Al-doped ZnO (AZO), Ga-doped ZnO (GZO), F-doped tin oxide (FTO), and conducting polymers, such as poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) thin films, or combinations thereof.

[0050] In embodiments, the output voltage of the triboelectric sensor is used to control the channel resistance (RCH) of the thin film transistor according to Equation (1):

GS-VTH) (i) wherein:

RCH: channel resistance of the TFT (e.g., of TFT 30/30A/30B),

μ: mobility of the TFT,

C: capacitance of a gate dielectric (e.g., gate dielectric or gate insulator 34) of the TFT, W: width of an active layer of the TFT (e.g., width W of active layer 33 as indicated in Figure 2C),

L: length of an active layer of the TFT (e.g., length L of active layer 33 as indicated in Figure 2C),

VTH: threshold voltage of the TFT, and

VGS: gate-to-source voltage, which is a difference between the gate voltage (VG)

and a source voltage (Vs) provided by the source electrode (e.g., source electrode 32A) of the TFT.

[0051] As noted hereinabove, the device 40 for measuring the output of the thin film transistor and calculating the force being applied to the triboelectric sensor translates a change in the output resistance of the VCR into the force being applied to the triboelectric sensor. In embodiments, the device comprises a processor or other logic circuitry configured, through hardware, software, and/or firmware, to convert the output voltage of the thin film transistor to a corresponding force value being applied to the triboelectric sensor. By way of example, and without limitation, in embodiments, the application processor is wirelessly coupled with the thin film transistor. For example, as indicated in Figure 3, which is a schematic of a force measuring system II comprising a weight circuit with wireless communication, according to an embodiment of this disclosure, device 40 can comprise an oscillator module 41 , a matching network 42, and an antenna 43. In such embodiment, the oscillator module 41 can be coupled with TFT 30 of read-out circuit 12 and with power supply 50 and can be configured to matching network 42 and antenna 43. Oscillator 41, matching network 42, and antenna 43 can be wired or wireless coupled and can utilize thin film or conventional electronics, in embodiments. In such embodiments, device 40 may send a signal to a peripheral component, such as, without limitation, a cellular phone, tablet, or computer, via wire or wirelessly (e.g., via Bluetooth).

[0052] The device comprising the triboelectric sensor and TFT can be fabricated in any suitable manner. For example, in embodiments, a device comprising the triboelectric sensor 20A and TFT 3 OA can be fabricated on a rigid substrate or flexible film using thin film deposition techniques at low processing temperatures. In the case of flexible polymer films, the process temperature may be less than the glass transition temperature of the flexible film, e.g., less than about 300 °C.

[0053] Also disclosed herein is a method of measuring force applied to a triboelectric sensor, the method comprising: applying a force to a triboelectric sensor, the force generating a triboelectric output voltage, utilizing the triboelectric output voltage to control a channel resistance (R _CH ) of a thin film transistor as a voltage controlled resistor (VCR), passing the output of the thin film transistor to a device configured to measure voltage, and apply an algorithm to convert the voltage to a force measurement. In embodiments, the algorithm translates a change in the channel resistance (R _CH ) of the voltage-controlled resistor (VCR) to the force applied to the triboelectric sensor. In embodiments, the voltage is converted to the force applied to the triboelectric sensor at a location remote from the triboelectric sensor. The components of the triboelectric sensor, thin film transistor, and VCR can be as described hereinabove.

[0054] Herein disclosed is a thin film-based portable and seamless electronic weight balance combining the triboelectric phenomena and thin film transistor based voltage-controlled resistor.

[0055] In embodiments, the herein-disclosed force measuring system (electronic weight balance) provides one or more advantages, including, without limitation, providing a force measuring system that is seamless and/or light weight, has a simple structure, exhibits a high sensitivity and accuracy, provides for a new and simple method of measuring force and weight, operates with a low power consumption, or a combination thereof EXAMPLES

[0056] The embodiments having been generally described, the following examples are given as particular embodiments of the disclosure and to demonstrate the practice and advantages thereof. It is understood that the examples are given by way of illustration and are not intended to limit the specification or the claims in any manner.

Example 1: Weight Measurement Using Triboelectric Sensor

[0057] Weight measurement using a triboelectric sensor 20 as per this disclosure (without TFT 30) was performed. Figure 4 is a plot of output voltage (V) vs. mass (g). The data in Figure 4 were obtained by measuring the output voltage of the triboelectric sensor versus different masses placed on it. The triboelectric sensor was fabricated on a PEN substrate. The electrode of the triboelectric sensor was made of a bilayer of 20 nm titanium and 80 nm of gold, prepared by e- beam evaporation, onto which a P (VDF-TrFE) film was spin coated to form the active layer for the touch sensor. P (VDF-TrFE) copolymer (70/ 30 mole percent) was dissolved in dimethyl- formamide (DMF) for 8 hours to provide a 20 weight percent (wt%) solution. The solution was subsequently spin coated on the substrate at a speed of 1500 rpm, forming a uniform layer comprising about 15 μηι PVDF-TrFE. The film was then annealed in a conventional oven for 4 hours at 135°C under vacuum. The output voltage of the triboelectric sensor was measured using a system electrometer, Keithley 6514 and a load resistance of 500 ΜΩ, connected in series.

ADDITIONAL DISCLOSURE

[0058] The particular embodiments disclosed above are illustrative only, as the present disclosure may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered or modified and such variations are considered within the scope and spirit of the present disclosure. Alternative embodiments that result from combining, integrating, and/or omitting features of the embodiment(s) are also within the scope of the disclosure. While compositions and methods are described in broader terms of "having", "comprising," "containing," or "including" various components or steps, the compositions and methods can also "consist essentially of or "consist of the various components and steps. Use of the term "optionally" with respect to any element of a claim means that the element is required, or alternatively, the element is not required, both alternatives being within the scope of the claim.

[0059] Numbers and ranges disclosed above may vary by some amount. Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range is specifically disclosed. In particular, every range of values (of the form, "from about a to about b," or, equivalently, "from approximately a to b," or, equivalently, "from approximately a-b") disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Moreover, the indefinite articles "a" or "an", as used in the claims, are defined herein to mean one or more than one of the element that it introduces. If there is any conflict in the usages of a word or term in this specification and one or more patent or other documents, the definitions that are consistent with this specification should be adopted.

[0060] Embodiments disclosed herein include:

[0061] A: A force measuring system comprising: a triboelectric sensor; a thin film transistor (TFT) operably coupled to the triboelectric sensor such that an output voltage of the triboelectric sensor, which depends on the force applied to it, can be used as a gate voltage (V _G ) received by a gate of the TFT; and a device configured to measure an output of the thin film transistor and calculate a force being applied to the triboelectric sensor.

[0062] B: A method of measuring force applied to a triboelectric sensor, the method comprising: applying a force to a triboelectric sensor, the force generating a triboelectric output voltage; utilizing the triboelectric output voltage to control a channel resistance (R _CH ) of a thin film transistor as a voltage-controlled resistor (VCR); passing the output of the thin film transistor to a device configured to measure voltage; and apply an algorithm to convert the voltage to a force measurement.

[0063] C: An electronic force system comprising: a triboelectric sensor configured to: receive a force, and provide an output voltage based on the force; and a transistor coupled to the triboelectric sensor and comprising: a gate configured to receive the output voltage as a gate voltage (V _G ), a source configured to provide a source voltage (Vs), and a channel resistance (R _CH ) based on a gate-to-source voltage (V _GS ), wherein V _GS is a difference between V _G and Vs.

[0064] D: An electronic force system comprising: a substrate layer; a transistor comprising: a gate electrode layer disposed on top of the substrate layer, a gate insulator layer disposed on top of a first portion of the gate electrode layer, a semiconductor layer disposed on top of the gate insulator layer, a source electrode layer disposed on top of a first portion of the semiconductor layer, and a drain electrode disposed on top of a second portion of the semiconductor layer; and a triboelectric layer disposed on top of a second portion of the gate electrode layer.

[0065] Each of embodiments A, B, C, and D may have one or more of the following additional elements: Element 1 : wherein use of the output voltage of the triboelectric sensor as the gate voltage (V _G ) of the TFT enables control of the output or channel resistance (R _CH ) of the thin film transistor as a voltage controlled resistor (VCR), wherein RCH is based on a gate-to-source voltage (VGS) which is a difference between the gate voltage (VG) and a source voltage (Vs) of the TFT. Element 2: wherein the device comprises a processor coupled to the TFT and configured to determine the force based on a change in RCH due to application of the force to the triboelectric sensor. Element 3: wherein the triboelectric sensor comprises an active triboelectric layer and a substrate separated by an electrode. Element 4: wherein the active triboelectric layer is a thin film comprising a polymer exhibiting a triboelectric effect, based on contact electrification, wherein the magnitude of the output voltage generated by the triboelectric layer depends on the force applied thereto. Element 5 : wherein the triboelectric thin film for the triboelectric-based sensor comprises a perfluorinated copolymer, or other statistical copolymer, synthesized by free radical polymerization in benzene. Element 6: wherein the triboelectric thin film has been modified to increase a friction coefficient, such as by forming a plurality of pillars, either similarly- or differently-sized and shapes, on the thin film. Element 7: wherein the perfluorinated copolymer comprises poly(methyl methacrylate)-co-poly(lH-lH-perfluoroctyl methacrylate). Element 8: wherein the perfluorinated copolymer has a molecular weight of approximately 10,000-50,000 and a dispersion ratio of approximately 1.5-2.5. Element 9: wherein the perfluorinated copolymer has a controlling perfluoro segment in proportion by weight of more than approximately fifty percent. Element 10: wherein the active triboelectric layer comprises an electronegative triboelectric layer or an electropositive triboelectric layer. Element 11 : wherein the electronegative triboelectric layer comprises PVDF, a copolymer of polyvinylidene difluoride (PVDF) (e.g., polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE), Vinylidene fluoride-trifluoroethylene- chlorofluoroethylene terpolymer (PVDF-TrFE CFE), and poly(vinylidene fluoride-co- hexafluoropropylene) (PVDF-HFP)), polydimethylsiloxane (PDMS), poly(methyl methacrylate) (PMMA), polytetrafluoroethylene (Teflon), polymer foams, poly(methyl methacrylate)-co- poly(lH-lH-perfluoroctyl methacrylate), fluorinated polymers, other electronegative polymers, or combinations thereof. Element 12: wherein the electropositive triboelectric layer comprises acetate, mica, nylon, other electropositive polymers, or a combination thereof. Element 13: wherein the substrate comprises polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), poly(methyl methacrylate) (PMMA), polyimide, parylenes (e.g. , Parylene C), other thermoplastic materials, or a combination thereof. Element 14: wherein the triboelectric sensor, the substrate of the triboelectric sensor, or both are flexible (e.g., as defined by the ability of a material to deform elastically and return to its original shape when the applied stress is removed without losing the functionality of the sensor) or rigid. Element 15: wherein the triboelectric sensor, the substrate of the triboelectric sensor, or both are at least partially transparent. Element 16: wherein the electrode is selected from conducting metals or transparent conducting oxides, such as Al, Ti, Cr, Au, indium tin oxide (ITO), Al-doped ZnO (AZO), Ga- doped ZnO (GZO), F-doped tin oxide (FTO), and conducting polymers, such as poly(3,4- ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) thin films, or combinations thereof. Element 17: wherein the output voltage of the triboelectric sensor is used to control the channel resistance (RCH) of the thin film transistor according to the equation: wherein, RCH- channel resistance of the TFT; μ: mobility of the TFT; C: capacitance of a gate dielectric of the TFT; W: width of an active layer of the TFT; L: length of an active layer of the TFT; V H- threshold voltage of the TFT; and VQS- gate-to-source voltage, which is a difference between the gate voltage (VG) and a source voltage (Vs) provided by a source electrode of the TFT. Element 18: wherein the thin film transistor comprises: the active layer of the thin film transistor; a source electrode; a drain electrode; the gate dielectric layer; a gate electrode; and a substrate. Element 19: wherein the active layer of the thin film transistor comprises at least one organic or inorganic semiconductor thin film. Element 20: wherein the active layer of the thin film transistor comprises a thin film of pentacene, poly(3-hexylthiophene-2,5-diyl (P3HT), zinc oxide (ZnO), indium gallium zinc oxide (InGaZnO), tin dioxide (Sn0 ₂ ), tin monoxide (SnO), indium oxide (ln ₂ 0 ₃ ), indium zinc oxide (IZO), zinc tin oxide (ZTO), or a combination thereof. Element 21 : wherein the gate dielectric layer comprises an insulator. Element 22: wherein the insulator is selected from aluminum oxide, (A1 ₂ 0 ₃ ), titanium dioxide (Ti0 ₂ ), hafnium oxide (Hf0 ₂ ), silicon dioxide (Si0 ₂ ), silicon nitride (SiN _x ), zirconium oxide, polymer dielectrics such as polyvinyl pyrrolidone) (PVP), polyvinyl acetate) (PVAc), PVDF-TrFE, P(VDF-TrFE-CTFE) Polyimide, PMMA, CYTOP or combinations thereof. Element 23: wherein the triboelectric sensor and the TFT share a common substrate, a common electrode, or both. Element 24: wherein the common substrate, the substrate of the TFT, or both comprise polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), poly(methyl methacrylate) (PMMA), polyimide, parylenes (e.g., Parylene C), other thermoplastic materials, or a combination thereof. Element 25: wherein the common substrate is flexible (e.g., as defined by the ability of a material to deform elastically and return to its original shape when the applied stress is removed without losing the functionality of the sensor) or rigid. Element 26: wherein the electrode of the triboelectric sensor, the gate electrode of the TFT, the drain electrode of the TFT, the source electrode of the TFT, the common electrode, or a combination thereof comprises conducting metals or transparent conducting oxides, such as Al, Ti, Cr, Au, indium tin oxide (ITO), Al-doped ZnO (AZO), Ga-doped ZnO (GZO), F-doped tin oxide (FTO), and conducting polymers, such as poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) thin films, or combinations thereof. Element 27: wherein the device configured to measure the output of the thin film transistor and calculate the force being applied to the tnboelectric sensor translates a change in the output resistance of the VCR into the force being applied to the tnboelectric sensor. Element 28: wherein the device comprises a processor or other logic circuitry configured, through hardware, software, and/or firmware, to convert the output voltage of the thin film transistor to a corresponding force value being applied to the triboelectric sensor. Element 29: wherein the application processor is wirelessly coupled with the thin film transistor.

[0066] Element 30: wherein the algorithm translates a change in the channel resistance (RCH) of the voltage controlled resistor (VCR) to the force applied to the triboelectric sensor. Element 31 : wherein the triboelectric sensor, the substrate of the triboelectric sensor, a substrate of the TFT, or a combination thereof is flexible (e.g., as defined by the ability of a material to deform elastically and return to its original shape when the applied stress is removed without losing the functionality of the sensor) or rigid. Element 32: wherein the triboelectric sensor, the substrate of the triboelectric sensor, a substrate of the TFT, or a combination thereof is at least partially transparent. Element 33: wherein the substrate of the triboelectric sensor, the thin film transistor, or a common substrate therefor comprises polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), poly(methyl methacrylate) (PMMA), polyimide, parylenes (e.g., Parylene C), other thermoplastic materials, or a combination thereof. Element 34: wherein the substrate of the triboelectric sensor, the thin film transistor, or a common substrate therefor is flexible (e.g., as defined by the ability of a material to deform elastically and return to its original shape when the applied stress is removed without losing the functionality of the sensor) or rigid. Element 35 : wherein the voltage is converted to the force applied to the triboelectric sensor at a location remote from the triboelectric sensor.

[0067] Element 36: wherein R _CH is further based on a threshold voltage (V _TH ) of the transistor. Element 37: wherein R _CH is further based on a difference between V _GS and V _TH - Element 38: wherein R _CH is further based on a mobility (μ) of the transistor. Element 39: wherein the gate comprises a dielectric material, and wherein R _CH is further based on a capacitance (C) of the dielectric material. Element 40: wherein the transistor further comprises a semiconductor layer, and wherein R _CH is further based on a width of the semiconductor layer. Element 41 : wherein R _CH is further based on a length of the semiconductor layer. Element 42: wherein R _CH is further based on a ratio of the width to the length. Element 43 : wherein R _CH is inversely proportional to μ, C, the ratio, and the voltage difference between V _GS and V _TH - Element 44:

. Element 45 : wherein the transistor is selected from thin-film transistors, silicon-based transistors, or combinations thereof. Element 46: wherein the force is a weight of an object. Element 47: further comprising a processor coupled to the transistor and configured to determine the force based on a change in R _CH due to application of the force to the triboelectric sensor.

[0068] While certain embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the teachings of this disclosure.

[0069] Numerous other modifications, equivalents, and alternatives, will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace such modifications, equivalents, and alternatives where applicable. Accordingly, the scope of protection is not limited by the description set out above but is only limited by the claims which follow, that scope including equivalents of the subject matter of the claims.