US-12617967-B2 - Ink composition, kit, method of manufacturing a deformable conductor utilizing the ink composition, deformable conductor, electronic device comprising the deformable conductor, method of manufacturing a conductor, conductor and electronic device comprising the conductor

US12617967B2US 12617967 B2US12617967 B2US 12617967B2US-12617967-B2

Abstract

The present invention relates to an ink composition, a kit comprising components of the ink composition, a method of manufacturing a deformable conductor utilizing the ink composition, a deformable conductor obtainable by the method, an electronic device, in particular a wearable and/or stretchable electronic device, comprising the deformable conductor, a method of manufactuing a conductor, a conductor obtainable by the method and an electronic device comprising the conductor. The ink composition comprises a source of transition metal ions, a reducing agent and a polymer and/or a polymer precursor, the polymer precursor comprising a polymerizable terminal multiple bond. The method of manufacturing a deformable conductor comprises the steps of applying the ink composition on at least a part of a surface of a deformable substrate and thermally treating and/or irradiating the ink composition.

Inventors

Thomas Griesser
Krzysztof Konrad KRAWCZYK

Assignees

Montanuniversität Leoben

Dates

Publication Date: 20260505
Application Date: 20200810
Priority Date: 20190812

Claims (7)

1 . A method of manufacturing a deformable conductor, the method comprising the steps of: (a) applying an ink composition on at least a part of a surface of a deformable substrate; (b) thermally treating and/or irradiating the ink composition; wherein the ink composition comprises: a source of transition metal ions, wherein the transition metal comprises at least one of silver and copper; a complexing agent selected from the group consisting of an alkyl amine having a primary amine functional group or a salt thereof; a reducing agent selected from the group consisting of formate, carbamate and combinations thereof; a polymer and/or a polymer precursor, the polymer precursor comprising a polymerizable terminal multiple bond; and a polymerization initiator, wherein the polymerization initiator comprises a thermal initiator.
2 . The method of manufacturing a deformable conductor according to claim 1 , wherein at least one of the following features is fulfilled: the step (a) of applying an ink composition on at least a part of a surface of a deformable substrate comprises printing the ink composition on at least a part of a surface of a deformable substrate; and/or the step (a) of applying an ink composition comprises applying the ink composition on only a part of a surface of the deformable substrate; and/or a thickness of the applied ink composition is from 5 μm to 200 μm; and/or the deformable substrate comprises at least one polymer material; and/or the step (b) of thermally treating the ink composition comprises a treatment at a temperature of from 40° C. to 300° C. and for a period of time of from 5 min to 90 min; and/or the step (b) of thermally treating and/or irradiating the ink composition comprises a heat treatment by means of near infrared (NIR) irradiation and/or an irradiation with near infrared radiation.
3 . The method of manufacturing a deformable conductor according to claim 1 , wherein the step (b) of thermally treating and/or irradiating the ink composition comprises a step (b1) of reducing transition metal ions by the reducing agent and a step (b2) of polymerizing the polymer precursor via the polymerizable terminal multiple bond.
4 . The method of manufacturing a deformable conductor according to claim 3 , wherein the step (b2) of polymerizing the polymer precursor via the polymerizable terminal multiple bond is carried out once at least 50% of the transition metal ions are reduced.
5 . The method of manufacturing a deformable conductor according to claim 1 , wherein at least one of the following features is fulfilled: the step (b) of thermally treating and/or irradiating the ink composition is carried out such that a percolated network of metal nano- or microstructure is formed; and/or the step (b) of thermally treating and/or irradiating the ink composition is carried out such that metal nanoparticles embedded in a polymer matrix are obtained; and/or a thickness of the thermally treated and/or irradiated ink after step (b) is from 100 nm to 10 μm; and/or further comprising, after a step (b) of thermally treating the ink composition, a step of irradiating at least part of the thermally treated ink with an energy-carrying activation beam.
6 . The method of manufacturing a deformable conductor according to claim 1 , wherein in step (a) the ink composition is applied on at least a part of a surface of a stretched deformable substrate.
7 . The method of manufacturing a deformable conductor according to claim 6 , wherein the step (b) of thermally treating and/or irradiating the ink composition is carried out while the deformable substrate being still in a stretched state; or further comprising, prior to step (b), a step of drying the ink composition, followed by a step of releasing the stretched deformable substrate to its original shape.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application is a U.S. national phase of International Application No. PCT/EP2020/072404 filed 10 Aug. 2020 which designated the U.S. and claims priority to British Patent Application No. 1911512.0 filed 12 Aug. 2019, the entire contents of each of which are hereby incorporated herein by reference. FIELD OF THE INVENTION The present invention relates to an ink composition, a kit comprising components of the ink composition, a method of manufacturing a deformable conductor utilizing the ink composition, a deformable conductor obtainable by the method, an electronic device, in particular a wearable and/or stretchable electronic device, comprising the deformable conductor, a method of manufacturing a conductor, a conductor obtainable by the method and an electronic device comprising the conductor. BACKGROUND The field of flexible or elastic electronics has rapidly grown over the past decade as a result of the increasing demand for real-time health monitoring, light weight mobile electronics, wearable displays etc. In the proximate future multifunctional electronic devices are going to be incorporated on the human body or clothing and a stable performance under conditions of high strain and extreme body motion such as folding, twisting and stretching will be required. The growing demand for such devices has triggered research in the design and manufacturing of stretchable elastomers and elastomer composites. Although good conductivity and high stretchability seem to be mutually exclusive features, a few approaches to combine stretchability and good electrical conductivity have been proposed to date. A common strategy is to obtain stretchable conductors from stiff, non-stretchable materials: (a) coiled metal wires, (b) meanders of metal foil, (c) thin layers of metal sputtered on prestretched or buckled/microporous substrates. These interconnects are stretchable within the boundaries imposed by geometrical features of the conductive film due to the microporosity of the surface, pattern design (e.g. meanders), pre-stretching and/or grain boundary lithography. Within these limits, excellent conductivity, speed and only little fatigue are observed. Nevertheless, above critical strain values (i.e. approx. 40% for meanders) irreversible destruction of the circuitry occurs. Additionally, the fabrication of conductive layers on prestretched substrates poses some technical challenges, which significantly increase the cost of manufacturing. Liquid metal conductors on elastomers show optimal R/R0 at almost any strain values but are difficult to manufacture industrially. In a recent publication (Hirsch, A., Michaud, H. O., Gerratt, A. P., Mulatier, S. de & Lacour, S. P. Intrinsically stretchable biphasic (solid-liquid) thin metal films. Advanced Materials 28, 4507-4512 (2016)), a thin layer of noble metal (i.e. Au) was evaporated onto an elastomer surface, followed by the evaporation of a layer of Ga. This resulted in a biphasic AuGa2/Ga layer, which showed excellent conductivity and was virtually fatigue free. The practical applicability for large-scale production is however limited by the thermal evaporation steps, which require high vacuum. High stretchability with low R/R0 was reported for stretchable inks based on PEDOT:PSS. The conductive polymer is typically used together with a fluorosurfactant and can be applied via screen printing. The advantage of the system lies inter alia in high optical transparency, which makes it a stretchable analogue to ITO films. However, for applications in stretchable interconnects, the limited conductivity of PEDOT:PSS is a disadvantage. Well resolved stretchable interconnects were manufactured by infiltration of an elastomeric substrate with Ag+ ions, followed by chemical reduction. In this approach, the high solubility of silver trifluoroacetate in organic solvents was exploited. The reduction is carried out by means of hydrazine or formaldehyde treatment. These substances are toxic or require a harsh environment, so the produced stretchable wiring boards need to be extensively rinsed. The preparation requires a multistep procedure and works well only on selected substrates, which limits its applicability in industrial processes. Despite the advantages of the systems described above, the vast majority of stretchable conductive systems are based on conductive composites, in which the polymeric part is responsible for the stretchability, while percolated conductive fillers allow efficient charge transfer. Conductive fillers may be carbon based (e.g. graphite, amorphous carbon, carbon nanotubes (CNTs), graphene, pyrolyzed bacterial cellulose) or metallic (e.g. metal nanowires, microflakes, micropowders, microflowers and nanoparticles). Combinations of different kinds of fillers were also reported. One method of fabricating conductive composites is the infiltration of a percolated filler-network with a liquid elastomer resin, which is s