A printable ink for use in an analog worm memory device and an analog worm memory device comprising such an ink

Abstract

The present invention relates to a printable ink (3) for use in manufacturing of an analog WORM (write once read many) memory device (10), the printable ink (3) comprising a solvent, a binder and a monomer being convertible to an electrically conducting polymer (4) through electrically induced polymerization. The present invention further relates to an analog WORM memory device (10) comprising such an ink (3).

Description

[0001] A PRINTABLE INK FOR USE IN AN ANALOG WORM MEMORY DEVICE AND AN

[0002] ANALOG WORM MEMORY DEVICE COMPRISING SUCH AN INK

[0003] TECHNICAL FIELD

[0004] The present invention relates to a printable ink for use in manufacturing of an analog WORM (write once read many) memory device, to an analog WORM memory device comprising such an ink, and a method for programming such a memory device.

[0005] BACKGROUND OF THE INVENTION

[0006] The adoption of artificial intelligence (Al) is in the process of transforming several high-value industries, including healthcare, manufacturing, and agriculture. However, the cost of the integrated circuits required to deploy pre-trained machine learning (ML) models remains a bottleneck to the practicality of applying Al to many areas, especially those of consumable and disposable goods, which would greatly benefit from local decision-making capabilities.

[0007] In parallel to the rapid advances in Al, printing technologies are making great strides in reducing the development and manufacturing costs of electronic components. In fact, the monetary and time investments into generating new circuitry are now low enough to allow for the development of bespoke circuits that are optimized for a given application, leading to a dramatic reduction in the circuit’s cost, footprint, and power consumption. However, despite significant advances, there exist no technologies that fulfill the need for programmable, non-volatile analog memory devices to serve as the synaptic element in printed neuromorphic circuits.

[0008] In particular, it is desirable to provide a non-volatile multi-state memory device that can be printed using either conventional printing or 3D printing technologies. Such a memory device may be used to store a continuum of synaptic values and may thus be used in printed neuromorphic circuits used for inference.

[0009] In view of the above, there is a need to provide a printable ink for use in manufacturing of a programmable, non-volatile analog memory device. Further, it is desirable to provide a programmable, non-volatile analog memory device to serve as the synaptic element in printed neuromorphic circuits. SUMMARY OF THE INVENTION

[0010] In view of the above, the present invention aims to solve the problems of the prior art. To this end, the present invention relates to a printable ink for use in manufacturing of an analog WORM (write once read many) memory device. The printable ink comprising a solvent and a binder. The amount of the components mentioned above may be varied depending on the binder material. According to the present invention, the printable ink further comprises a monomer being convertible to an electrically conducting polymer through electrically induced polymerization.

[0011] The electrically induced polymerization may be an oxidative polymerization.

[0012] If the monomer and its corresponding counter-ion are present in sufficient concentration, these components may function as electrolyte. Otherwise, the printable ink further comprises an electrolyte that is added as a separate component. The electrolyte may be an inorganic salt, an organic salts or mixture thereof. In particular, the cation may be selected from the group consisting of Na+, K+, Mg2+, Ca2+, NHY, H+. The anion may be selected from the group consisting of Cl Br, OH CH3COO; F; CO32; SO42’.

[0013] The binder may be a polymeric binder, such as cellulose or derivatives thereof, such as methylcellulose, hydroxypropyl cellulose, and carboxymethyl cellulose (CMC). Further, the binder may be any other suitable material, e.g. hydrocarbon resins, acrylic, and polyamide binders.

[0014] The monomer may be selected from the group consisting of soluble derivatives of thiophene, aniline, ethylenedioxythiophene, pyrrole or mixtures thereof.

[0015] The printable ink according to the present invention may further comprise at least one additive selected from thickeners, additional solvents, surfactants and viscoelastic modulators. Such additives may be used in order to adjust the viscoelastic properties of the printable ink to assist in printability.

[0016] The solvent used in the printable ink according to the present invention may be any suitable solvent. In particular, the solvent may be water or ionic liquid. The embodiment wherein the solvent is an ionic liquid offers the advantage of eliminating the need for an additional electrolyte. The present invention further relates to an analog WORM memory device comprising a non-conductive support substrate having a top surface. The support substrate is arranged for providing structural integrity to the memory device. The support substrate may be manufactured of paper, rubber, silicone-based substrates or organic polymers.

[0017] The analog WORM memory device further comprises a set of at least two electrodes printed on the top surface of the support substrate.

[0018] The analog WORM memory device further comprises a printable ink being arranged in contact with the at least two electrodes, wherein the printable ink comprises a solvent, a binder and a monomer being convertible to an electrically conducting polymer through electrically induced polymerization. The aspects of the printable ink have been described in great detail above.

[0019] The memory device according to the present invention may comprise a redox species for providing a counter-reaction for polymerization. The redox species may be comprised in the printable ink. Alternatively, the redox species may be printed in the form of a redox electrode, e.g. AgCI, being arranged in contact with the printable ink.

[0020] The memory device according to the present invention may be comprise a programming state and a programmed state. In the programming state, the amount of the solvent in the printable ink is above a solvent content threshold.

[0021] The present invention further relates to a method for programming an analog WORM memory device described above. The method comprises the steps of: a) applying a voltage being above a polymerization threshold to the electrodes being in contact with the printable ink. b) allowing formation and accumulation of an electrically conducting polymer in the printable ink between the at least two electrodes due to the electropolymerization of the monomer embedded in the printable ink.

[0022] Step a) may be performed by applying a current that causes the voltage to rise above the polymerization threshold. Normally, steps a) and b) occur simultaneously. The voltage in step a) may be applied continuously or not continuously. For instance, the voltage may be applied once for e.g. 10 seconds. Alternatively, voltage may be applied 10 times for one second. In such a way, it is possible to control the written state by changing either the duration of the writing event or the number of writing events.

[0023] The voltage applied in step a) may be in the range from 0.05 V to 10 V.

[0024] Step a) may be performed during a time period of from 10 ns to 360 min.

[0025] The memory device according to the present invention is programmed in the following way. A voltage being above the polymerization threshold is applied between the electrodes. If the amount of the solvent in the printable ink is above a solvent content threshold, the monomer is converted to a conducting polymer. The accumulation of the conducting polymer between the electrodes allows the formation of a conductive path between the electrodes, which results in the reduction in the resistance between the electrodes, hence providing for a non-volatile change in states in the analog memory device.

[0026] The resistance between the two electrodes of the memory device can thus be modified in a controllable manner. In other words, the resistance between the electrodes may be decreased by the application of voltage above the polymerization threshold only when the amount of the solvent is above the solvent content threshold.

[0027] The memory device according to the present invention may comprise two states — a programming state and a programmed state. Memory switching can proceed when the amount of solvent, e.g. measured in weight percentage, in the printable ink is above a given threshold (solvent content threshold) but not below the solvent content threshold.

[0028] In the programming state, when the amount of the solvent is above the solvent content threshold, memory state switching is induced by the application of a voltage above the polymerization threshold to the electrodes that are in contact with the printable ink, which leads to the formation and accumulation of the conducting polymer in the ink between the two electrodes due to the electropolymerization of the monomer embedded in the ink, hence reducing the resistance between the electrodes. In the programmed state, when the amount of the solvent is below the solvent content threshold, it is possible to apply voltage between the two electrodes being above the polymerization threshold without the modification of the resistance between the two electrodes.

[0029] The present invention thus provides a multi-state memory device that can serve as a synaptic element to be used in printed neuromorphic circuits designed for inference. For example, a printed neuromorphic circuit could be programmed to locally classify inputs from a panel of medical, chemical, or environmental sensors, which would provide benefits in cost, specificity, and data security.

[0030] BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, of which:

[0032] Fig. 1a shows an analog WORM memory device according to the present invention in programmable state;

[0033] Fig. 1 b shows an analog WORM memory device according to the present invention in programmed state;

[0034] Fig. 2 illustrates programming conditions for the analog WORM memory device according to the present invention.

[0035] DETAILED DESCRIPTION OF THE INVENTION

[0036] Figs. 1a and 1b provide an analog WORM memory device 10 comprising a non-conductive support substrate 1 having a top surface 1a. The support substrate 1 is arranged for providing structural integrity to the memory device 10.

[0037] The analog WORM memory device further comprises a set of two electrodes 2 printed on the top surface 1a of the support substrate 1 .

[0038] The analog WORM memory device 10 further comprises a printable ink 3 being arranged in contact with the two electrodes 2. As mentioned above, the printable ink comprises a solvent, a binder and a monomer being convertible to an electrically conducting polymer through electrically induced polymerization. The aspects of the printable ink have been described in great detail above. The memory device 10 in Figs. 1a and 1b comprises a programming state and a programmed state. In the programming state, shown in Fig. 1a, the amount of the solvent in the printable ink 3 is above a solvent content threshold.

[0039] A voltage V being above the polymerization threshold is applied between the electrodes 2. If the amount of the solvent in the printable ink is above a solvent content threshold, as is the case in the embodiment shown in Fig. 1a, the monomer is converted to a conducting polymer 4, shown in Fig. 1b. The accumulation of the conducting polymer 4 between the electrodes 2 results in the reduction in the resistance between the electrodes 2, hence providing for a non-volatile change in states in the analog memory device 10.

[0040] The resistance between the two electrodes of the memory device can thus be modified in a controllable manner. In other words, the resistance between the electrodes may be decreased by the application of voltage above the polymerization threshold only when the amount of the solvent is above the solvent content threshold, as shown in Fig. 2.

[0041] Although the present invention has been described with reference to various embodiments, those skilled in the art will recognize that changes may be made without departing from the scope of the invention. It is intended that the detailed description be regarded as illustrative and that the appended claims including all the equivalents are intended to define the scope of the invention.

Claims

CLAIMS1. A printable ink (3) for use in manufacturing of an analog WORM (write once read many) memory device (10), said printable ink (3) comprising a solvent and a binder, characterized in that said printable ink (3) further comprises a monomer being convertible to an electrically conducting polymer (4) through electrically induced polymerization.

2. The printable ink (3) according to claim 1, wherein said binder is a polymeric binder.

3. The printable ink (3) according to claim 2, wherein said polymeric binder is cellulose or a derivative thereof.

4. The printable ink (3) according to any one of the preceding claims, where said monomer is selected from the group consisting of soluble derivatives of thiophene, aniline, ethylenedioxythiophene , pyrrole or mixtures thereof.

5. The printable ink (3) according to any one of the preceding claims, said printable ink (3) further comprising an electrolyte.

6. The printable ink (3) according to any one of the preceding claims, said printable ink (3) further comprising at least one additive selected from thickeners, additional solvents, surfactants and viscoelastic modulators.

7. The printable ink (3) according to any one of the preceding claims, wherein said solvent is water or ionic liquid.

8. An analog WORM memory device (10) comprising a non-conductive support substrate (1) having a top surface (1a); a set of at least two electrodes (2) printed on said top surface (1a) of said support substrate (1); and a printable ink (3) being arranged in contact with said at least two electrodes (2), said printable ink (3) comprising a solvent and a binder,characterized in that said printable ink (3) further comprises a monomer being convertible to an electrically conducting polymer (4) through electrically induced polymerization.

9. The memory device (10) according to claim 8, said memory device (10) further comprising a redox species for providing a counter-reaction for polymerization.

10. The memory device (10) according to claim 9 wherein said redox species is comprised in said printable ink (3).

11. The memory device (10) according to claim 9 wherein said redox species is printed in the form of a redox electrode being arranged in contact with said printable ink (3).

12. The memory device (10) according to any one of claims 8-11 , wherein said memory device (10) has a programming state and a programmed state, wherein in said programming state the amount of said solvent in said printable ink (3) is above a solvent content threshold.

13. A method for programming an analog WORM memory device (10) comprising a non-conductive support substrate (1) having a top surface(la); a set of at least two electrodes (2) printed on said top surface (1a) of said support substrate (1); and a printable ink (3) being arranged in contact with said at least two electrodes (2), said printable ink (3) comprising a solvent and a binder, said printable ink (3) further comprising a monomer being convertible to an electrically conducting polymer (4) through electrically induced polymerization, wherein the amount of said solvent in said printable ink (3) is above a solvent content threshold; said method comprising the steps of: a) applying a voltage being above a polymerization threshold to the electrodes (2) being in contact with said printable ink (3); b) allowing formation and accumulation of an electrically conducting polymer (4) in said printable ink (3) between said at least two electrodes (2) due to the electropolymerization of said monomer embedded in said printable ink (3).

14. The method according to claim 13, wherein said voltage in step a) is in the range from 0.05 V to 10 V.

15. The method according to any one of claim 13 or 14, wherein step a) is performed during a time period of from 10 ns to 360 min.

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