Flexible electronics

Abstract

The disclosure relates to a wearable flexible electronics device which comprises a first layer with a first film, a second layer with a second film, and an electronics circuit in-between the first and the second layer, wherein the first film and the second film are disintegrable in a liquid formulation comprising water. An advantage of this arrangement is that the first and the second layer may be easily dissolved and / or dispersed in water comprising liquid formulation and the remaining electronics circuit may be recycled as a neat e-waste stream.

Description

[0001] FLEXIBLE ELECTRONICS

[0002] FIELD OF THE DISCLOSURE

[0003] The disclosure relates to a flexible electronics device, more specifically to wearable electronics.

[0004] BACKGROUND OF THE DISCLOSURE

[0005] Flexible electronics, as Figure 1 illustrates, traditionally comprises a substrate 101 with an electronics circuit 102 on a top surface of the substrate, and an encapsulation layer 103 on covering the electronics circuit in order to protect it from delamination and losing mechanical and electrical contact. Traditionally, the encapsulation layer 103 covering the electronics circuit is, for example, an epoxy thin film. The problem with such arrangement is that it limits flexibility due to mismatch of mechanical properties of the substrate and the epoxy layer. In addition, the recyclability of such device is limited since separation of the electronics circuit and components from the epoxy thin film is complicated. Improved recyclability of electronic devices is pushed forward in EU legislation, and it remains a keystone challenge in building circularity in the electronics industry. Thus, a solution for an electronics device which can be easily recycled by separating electronics components from flexible material, while maintaining the device performance, is desired.

[0006] BRIEF DESCRIPTION OF THE DISCLOSURE

[0007] An object of the present disclosure is to provide a flexible electronics device so as to solve the above problems.

[0008] The object of the disclosure is achieved by an arrangement characterized by what is stated in the independent claims. The preferred embodiments of the disclosure are disclosed in the dependent claims.

[0009] The disclosure is based on the idea of using a first layer, an electronics circuit and a second layer in the structure of the flexible electronics device, wherein the first layer and the second layer are disintegrable in liquid formulation comprising water. An advantage of this arrangement is that the first and the second layer may be easily dissolved and / or dispersed in water comprising liquid formulation and the remaining electronics circuit may be recycled as a neat e-waste stream.

[0010] BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In the following the disclosure will be described in greater detail by means of preferred embodiments with reference to the accompanying drawings, in which:

[0012] Figure 1 illustrates a prior art electronics device with an electronics circuit embedded into an epoxy-based layer;

[0013] Figure 2 illustrates an electronics device of this disclosure comprising a first layer, an electronics circuit and a second layer;

[0014] Figure 3a illustrates one example of the electronics device with the second layer surrounding the electronics circuit;

[0015] Figure 3b illustrates another example of the electronics device with the electronics circuit embedded into the second layer;

[0016] Figure 4a illustrates a method of fabrication the electronics device with the second layer surrounding the electronics circuit;

[0017] Figure 4b illustrates the method of fabricating the electronics device with the electronics circuit embedded into the second layer.

[0018] DETAILED DESCRIPTION OF THE DISCLOSURE

[0019] This disclosure describes a wearable flexible electronics device. The term “wearable” implies that the electronics device is configured to be applied and attached to a skin, or piece of clothing, and worn for a certain period of time. The term “flexible” refers to mechanical properties of the electronics device and implies that the device can be bent to a certain degree without breaking while wearing. The term “electronics” implies that the device comprises an electronic circuit. The wearable flexible electronics device may also be called “the electronics device” in any part of this disclosure.

[0020] A wearable flexible electronics device comprising a first layer comprising a first film, wherein the first film is formed of a first material, and wherein the first layer comprises a top surface, an electronics circuit, wherein the electronics circuit is at the top surface of the first layer, characterized by that it further comprises a second layer comprising a second film, wherein the second film is formed of a second material, and wherein the second film is at the top surface of the first layer in contact with the electronics circuit, and wherein the at least first film and the second film are disintegrable in a liquid formulation, wherein the liquid formulation comprises water.

[0021] The wearable flexible electronics device 200 is illustrated in Figure 2. A first layer 201 of the electronics device 200 of this disclosure may comprise a first film 202. The first layer 201 may also be called a substrate. A material of the first film 202 may be called a first material. Alternatively, the material of the first film 202 may comprise more than one material. In other words, the first film 202 may comprise the first material and at least one additional material. The first layer 201 may comprise a top surface and a bottom surface. The bottom surface of the first layer 201 may be configured to attach to the skin. The first film 202 may also comprise a top surface and a bottom surface. The top surface of the first layer 201 may correspond to the top surface of the first film 202. The bottom surface of the first layer 201 may correspond to the bottom surface of the first film 202. Thus, the bottom surface of the first film 202 may be configured to attach to the skin.

[0022] The first layer 201 may comprise additional structures such as an integral local region (not illustrated). The integral local region, may have greater elastic moduli than, for example, the first film, meaning that it may withstand applied mechanical stress without breaking or plastic deformation better than bulk substrate regions of the first film. In other words, the first film of the first layer may be reinforced with the integral local region integrated into it.

[0023] The first layer 201 may comprise additional structures such as at least one measurement electrode at the bottom surface (not illustrated). The measurement electrode may be configured to attach to skin. The measurement electrode may extend from the bottom surface to the top surface of the first layer 201 .

[0024] The thickness of the first layer 201 may be equal to the thickness of the first film 202. Alternatively, the thickness of the first layer 201 may be greater than the thickness of the first film 202. Alternatively, the thickness of the first layer 201 may be variable and vary over the length of the layer. For example, in some portions of the first layer 201 , the thickness may be equal to the thickness of the first film 202, and in other portions of the first layer 201 the thickness may be greater than of the first film 202. In all cases, thickness of the first layer 201 may be 10 - 100 urn. Thickness of the first layer 201 may be more than 10 um, more than 30 um, more than 50 urn, more than 70 urn, more than 90 urn. Thickness of the first layer 201 may be less than 100 um, less than 80 um, less than 60 um, less than 40 um, less than 20 um. Such thickness ensures flexibility of the structure and its attachment to the skin.

[0025] An electronics circuit 203 is at the top surface of the first layer 201 . The electronics circuit

[0026] 203 may be attached to the first layer 201 . Specifically, the electronics circuit 203 may be attached to the first film 202.

[0027] The electronics circuit may comprise a number of electronics components such as 204. In other words, the electronics circuit 203 may be formed from the number of electronics components 204. The electronics circuit 203 may comprise more than one electronics component. The electronics components 204 may, for example be, one or more diode, transistor, capacitor, microprocessor, or a combination of them. The electronics components 204 may be surface-mounted device (SMD) electronics components.

[0028] The electronics circuit 203 may comprise a conductive pattern 205. The conductive pattern 205 may be at the top surface of the first layer 201. The conductive pattern 205 may be under some of the electronics components 204. The purpose of the conductive pattern 205 may be to provide electrical contacts for the electronics components 204. The thickness of the conductive pattern 205 may be 10 - 300 um. The electronics components

[0029] 204 may be attached to the conductive pattern 205. In cases when the electronics components 204 are attached to the conductive pattern 205, the electronics components 204 may also be in contact with the first layer 201 . The conductive pattern 205, if present, may provide electronic connection with the electronics components 204, while mechanical connection of the electronics components 204 with the first layer 201 may be limited. Thus, additional layer for mechanical fixation of the electronics components 204 to the first layer 201 , such as a second layer described below, is needed.

[0030] The electronics circuit 203 may occupy part of the top surface of the first layer 201 . Specifically, the electronics circuit 203 may occupy 10 - 90 % of the top surface of the first layer 201 . The electronics circuit 203 may occupy more than 10%, more than 30%, more than 50%, more than 70% of the top surface of the first layer 201 . The electronics circuit 203 may occupy less than 90% of the top surface of the first layer 201 .

[0031] The components of the electronics circuit 203 may be reusable. In this case, the electronics circuit 203 may be water-resistant. A second layer 206 of the electronics device 200 comprises a second film 207. Both the second layer 206 and the second film 207 may comprise a top surface and a bottom surface. The material of the second film 207 may be called a second material. The bottom surface of the second layer 206 may be attached to the top surface of the first layer 201 . Specifically, the second film 207 may be attached to the first film 202. In addition, the second film 207 is in contact with the electronics circuit 203.

[0032] The second film 207 may be deposited to the first layer 201 in a liquid form prior to its solidification. In other words, the second film 207 may be casted onto the first layer 201 prior to its solidification on the top surface of the first layer 201 .

[0033] The second layer 206 of the electronics device may comprise other structures than the second film 207. If the second layer 206 of the electronics device comprises only the second film 207, the second layer may be referred to as the “second film”.

[0034] The second layer 206 may occupy part of the top surface of the first layer 201 which is free from electronics circuit 203. Specifically, if the electronics circuit 203 may occupy 10 - 90 %, the second layer 206 may also occupy 10 - 90 % of the top surface of the first layer 201 . The second layer 206 may occupy more than 10%, more than 30%, more than 50%, more than 70% of the top surface of the first layer 201 . The second layer 206 may occupy less than 90% of the top surface of the first layer 201 . The width and the length of the second layer 206 may be smaller than those of the first layer 201 . The width and the length of the second layer 206 may be equal to those of the first layer 201 . Alternatively, the thickness of the second layer 206 may be variable and vary over the length of the layer. The thickness of the second layer 206 may be 10 - 100 urn. Thickness of the second layer 206 may be more than 10 urn, more than 30 urn, more than 50 urn, more than 70 urn, more than 90 urn. Thickness of the second layer 206 may be less than 100 urn, less than 80 urn, less than 60 urn, less than 40 urn, less than 20 urn.

[0035] The first layer 201 of the electronics device 200 of this disclosure may comprise an additional first film (not illustrated). The additional first film may comprise a top surface and a bottom surface. The bottom surface of the additional first film may be attached to the top surface of the first film. The bottom surface of additional first film may be configured to be removed from the first film before attaching the first film to the skin. In this configuration, the top surface of the additional first film may correspond to the top surface of the first layer 201. The first layer 201 may be attached to the second layer 206 by attaching the first film 202 to the second film 207. Thus, there may be no additional intermediate layer, such as glue or adhesive, which would attach the first film 202 and the second film 207 together. In other words, the first film and the second film 207 may be directly in contact with each other.

[0036] In this disclosure, both the first and the second materials of the first film 202 and the second film 207 may be disintegrable in a liquid formulation comprising water. In other words, at least the first film 202 and the second film 207 may be disintegrable in the liquid formulation comprising water. Alternatively, the entire first layer 201 and the second layer 206 may be disintegrable in the liquid formulation comprising water. The liquid formulation may alternatively be called “a liquid”. The liquid formulation may alternatively be called “a liquid”. A liquid formulation comprising water may alternatively be called “an aqueous solution”.

[0037] The term “disintegrable” may define the material capable of being broken down into simpler individual components such us two or more fragments, particles, molecules or atoms. Disintegration of the materials of this disclosure may occur by means of “dissolution” or “dispersion”. In other words, both the first and the second materials of the first film 202 and the second film 207 may be dissolvable and / or dispersible in the liquid formulation comprising water. When term “disintegrable” is used in this disclosure, it implies using terms “dissolvable” and / or “dispersible”.

[0038] The term “dissolvable” may mean being able to mix two phases with the formation of one new homogeneous phase. In other words, the material is dissolvable if it may be mixed with the liquid formulation and become incorporated into the liquid formulation.

[0039] The term “dispersible” may mean being able to dilute a first phase by spreading into a second phase by diffusion or turbulent motion. In other words, the material is dispersible if it its individual particles may separate from each other and evenly distribute and completely mix with the liquid formulation. The material may be heterodispersed, meaning that the material and the liquid formulation form a colloidal system in which all the particles are of different sizes. In dispersion, the individual particles may separate from each other using mechanical forces, and in some cases, with the aid of chemical additives such as surfactants or polyelectrolytes. The electronics circuit 203 may be between the first layer 201 and the second layer 206. Specifically, the electronics circuit 203 may be between the first film 202 and the second film 207. In other words, the first film 202 and the second film 207 may be fused to form a unified structure with the electronics circuit 203 in-between. When both the first film 202 and the second film 207 are dissolved or dispersed, the electronics circuit 203 may be released from in-between.

[0040] Embodiments of the electronics device

[0041] The flexible electronics device, wherein the electronics circuit may comprise number of electronics components, and each electronics component may be surrounded by the second film.

[0042] In one embodiment of this disclosure illustrated in Figure 3a, the second film 207 may be at the top surface of the first layer 201 and in contact with the electronics circuit 203. Specifically, the second film 207 may be around the sides of each of the electronics components 204, but not on top of them. In other words, the electronics components 204 may be partially embedded into the second film 207. This example of the electronics device may further comprise the conductive pattern (not illustrated in Figure 3a).

[0043] The flexible electronics device, wherein the electronics circuit may be embedded into the second film.

[0044] In another embodiment of the disclosure illustrated in Figure 3b, the second film 207 may be at the top surface of the first layer 201 and entirely encapsulate the electronics circuit 203. The second film may surround the circuit on all sides and also on top. In other words, each of the electronics components 204 may be embedded into the second layer 206. In addition, Figure 3b illustrates the conductive pattern 205, which is also embedded into the second layer 206.

[0045] Materials and properties

[0046] The flexible electronics device, wherein the second material may be a cellulosic composition. The flexible electronics device, wherein the first material and the second material may be the same. The first material of the first film 202 may be cellulosic composition. Specifically, it may be a nanocomposite of cellulose nanofibril (CNF) and hydroxyethyl cellulose (HEC). A non- exhaustive list of examples of other applicable materials that can be deposited in fluidic form and cured into a solid film include cellulose fibers, dissolved cellulose, microf ibrillated cellulose (MFC), nanofibrillated cellulose (NFC), cellulose nanocrystals (CNC), bacterial cellulose (BC), cellulose derivatives like (but not limited to) carboxymethyl cellulose (CMC), hydroxypropyl cellulose (HPC), hydroxypropylmethyl cellulose (HPMC), methyl cellulose (MC), and non-cellulosic materials like chitin, chitosan, lignin, suberin, cutin, alginate, hemicelluloses, modified and native starch, proteins, polyhydroxyalkanoates (PHAs), polybutylene succinate (PBS), polybutylene succinate-co-adipate (PBSA), polylactic acid (PLA) and its copolymers, etc.

[0047] The material of the conductive pattern 205, if present, may be an electrically conductive adhesive. Specifically, the material of the conductive pattern may be a composite of an adhesive component such as a varnish, synthetic resin, or silicone, and a conductive component such as silver, nickel, copper or graphite. Alternatively, the material of the conductive pattern may be a conductive polymer such as PEDOT or polypyrrole. The material of the conductive pattern may be dissolvable and / or dispersible in the liquid formulation comprising water. Alternatively, the material of the conductive pattern may be non-dissolvable and / or non-dispersible and non-biodegradable.

[0048] The second material of the second film 207 may be any of the material listed above as material options for the first film. The second material may be the same as the first material. In other words, the chemical composition of the first material may be the same as the chemical composition of the second material. Alternatively, the second and the first materials may be different. In other words, the chemical composition of the first material may be different from the chemical composition of the second material. However, even if the second and the first materials are different, they both may be disintegrable in the liquid formulation comprising water.

[0049] The first and the second materials may alternatively comprise more than one material composition. In that case, the first and the second materials may be called a first material formulation and a second material formulation. Specifically, material formulations may be a mixture of a precursor and a photocurable agent. For example, the photocurable agent may be modified lignin, acrylates, methacrylates, epoxies, urethanes, vanillin, rosin, and terpenes. The material formulations with the photocurable agents may be cured by exposing it to a light source.

[0050] The flexible electronics device, wherein concentration of water in the liquid formulation may be 1 - 100%.

[0051] The first and the second materials may be dissolvable and / or dispersible in the liquid formulation. The liquid formulation may comprise water. The water concentration in the liquid formulation may be 1 - 100%. The water concentration in the liquid formulation may be more than 1%, more than 10%, more than 25%, more than 50%, more than 65%, more than 80%, more than 90%. The water concentration in the liquid formulation may be less than 100%, less than 95%, less than 75%, less than 55%, less than 35%, less than 15%, less than 5%. The liquid formulation may comprise other liquids such as (but not limited to) acids, bases, or organic solvents like (but not limited to) acetone, ethanol, isopropanol, toluene, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO). The concentration of liquids from the list above in the liquid formulation may be 0 - 99%. The concentration of liquids other than water in the liquid formulation may be more than 0%, more than 1%, more than 5%, more than 20%, more than 50%, more than 75%. The concentration of liquids from the list above in the liquid formulation may be less than 99%, less than 80%, less than 60%, less than 40%, less than 25%, less than 10%, less than 3%.

[0052] The liquid formulation may comprise more than two liquids with different chemical composition. For example, the liquid formulation may comprise water and at least two different liquids other than water. The at least two different liquids other than water may have different chemical compositions.

[0053] The first and the second materials may be disintegrable in soil. “Disintegration in soil” may refer to the at least partial physical breakdown or fragmentation of a material when exposed to soil. It may not necessarily involve the complete breakdown of the material into its basic components. Some materials may disintegrate into smaller pieces without undergoing significant chemical changes. The first and the second materials may be biodegradable. The term “biodegradable” may refer to material that may be broken down into simpler compounds by the action of microorganisms such as bacteria, fungi, or other living organisms. Biodegradable materials may be broken down into natural substances like water, carbon dioxide, and biomass or mineral salts through biological processes in the presence of oxygen. Alternatively, at least the first material may be biocompatible. Alternatively, at least the second material may be biocompatible. The biocompatible second material is needed to ensure that the wearable flexible electronics device is safe to be applied to the skin. The term “biocompatibility” may refer to the ability of a material or substance to coexist with living tissues or biological systems without causing harm or undesirable reactions. Biocompatible materials are designed to perform with an appropriate host response in a specific application. Specifically, biocompatible materials are designed to interact with biological systems in a way that is well-tolerated by the body without triggering adverse reactions, inflammation, or immune responses.

[0054] The first layer 201 and the second layer 206 may comprise elements which are not disintegrable in the liquid formulation comprising water.

[0055] The first and second materials may have mechanical properties suitable for being applied to the skin. Specifically, the first and second materials may be flexible in order to follow the natural curvature of the skin in different locations on the body and stay attached to skin without delaminating during movement.

[0056] The following examples describe some combinations of the first and the second materials in the flexible electronics device:

[0057] Example 1

[0058] The first material may be paper. The second material may be nanocellulose. Both the first and the second materials may be dispersible in the liquid formulation comprising water.

[0059] Example 2

[0060] The first material may be paper. The second material may be carboxymethyl cellulose. The first material may be dispersible in the liquid formulation comprising water. The second material may be dissolvable in the liquid formulation comprising water. Example 3

[0061] The first material may be carboxymethyl cellulose. The second material may be carboxymethyl cellulose. Both the first and the second materials may be dissolvable in the liquid formulation comprising water.

[0062] Fabrication method of the electronics device

[0063] A method of fabricating the wearable flexible electronics device may comprise the steps of forming a first layer by depositing a first film of a first material in liquid state on a support surface, and curing the first film, placing an electronics circuit into an electronics region on a top surface of the first layer, forming a second layer by depositing a second film of a second material in liquid state on the top surface of the first layer in contact with the electronics circuit, and curing the second film, and wherein the first film and the second film may be disintegrable in a liquid formulation, wherein the liquid formulation may comprise water.

[0064] The first film 202 may be formed by casting the first material in liquid form on a support surface 401 as step a) of Figure 4a illustrates. Alternatively, the first film may be formed by spraying the liquid of the first material on a support surface 401 . The deposited first material may be distributed into a layer of even thickness. Alternatively, the deposited first material may be mechanically distributed into a layer of even thickness. The support surface 401 may, for example, be a wafer or any other planar structure which can hold the deposited material.

[0065] The deposited liquid of the first material may be solidified by drying in order to form the solid first film 202. The drying may be done, for example, under ambient conditions, or by using heating or vacuum. Alternatively, depending on the chemical composition of the first material, the drying may be done by curing under the light source. After drying, the first film 202 of the first material is formed.

[0066] The electronics circuit 203 may be attached to the top surface of the first layer 202 as in step b) in Figure 4a. The electronics circuit 203 may comprise number of separate electronics components 204. Thus, each electronics component 204 may be place to a dedicated place on the top surface of the first layer 202. The second film 207 may be formed by depositing the second material in liquid form on a top surface of the first layer 201 as in step c) of Figure 4a. The liquid of the second material may be deposited by, for example, dispensing or spray coating. The second material may be deposited so that it encloses the electronics circuit 203 as was explained above with reference to Figure 3b. Alternatively, the second material may be deposited so that it surrounds each electronics component 204 of the electronics circuit 203 as was explained above with reference to Figure 3a. In other words, the second material may be in contact with at least the top surface of the first layer 201 and some parts of the each of the electronics components 204.

[0067] The second material in liquid form may be solidified by drying in order to form the solid second film 207. The drying may be done by, for example, under ambient conditions, or by using heating or vacuum. Alternatively, depending on the chemical composition of the second material, the drying may be done by curing under the light source. After drying, the second film 207 of the second material is formed.

[0068] Another example of fabrication method is illustrated in Figure 4b. Step a) corresponds to step a) of the method of Figure 4a, in which the first film 202 may be formed by casting the liquid of the first material on a support surface 401 . In step b) of Figure 4b, the conductive pattern 205 may be deposited on the top surface of the first film. The conductive pattern may be deposited by, for example, printing, chemical and physical vapor deposition, electroplating, direct writing or dispensing. Depending on the material, the conductive pattern may be deposited in liquid phase and then cured into solid phase by, for example, drying or exposing to the light source. The dedicated place of each of the electronics components 204 may thus be at the specific place of the conductive pattern 205 as in step c). The conductive pattern provides electronic connection with the electronics circuit, but the strength of the mechanical connection between the conductive pattern and the electronics components may be limited. Thus, additional layer for mechanical fixation of the electronics circuit, such as the second layer 206 with the second film 207, may be needed.

[0069] The deposition of the second film 207 is illustrated in step d) of Figure 4b. The second film 207 may be formed by depositing the second material in liquid form on a top surface of the first layer 201 as in step c) of Figure 4a. The step d) of Figure 4b may correspond to the step c) of Figure 4a as described above.

[0070] After the whole fabrication process is completed, the wearable flexible electronics device may be detached from the support surface and attached to, for example, skin or a piece of clothing.

[0071] Recycling of the electronics device

[0072] One advantage of the disclosed electronics device is that the first and the second films may be recycled by dispersion, dissolution or biodegradation, while electronics circuit may be directly reused or recycled together with, for example, electronic waste.

[0073] The electronics device of this disclosure may be disassembled. The disassembly process may include the following steps:

[0074] 1 ) Place the electronics device into a volume of liquid formulation comprising water so that the whole electronics device is immersed.

[0075] 2) Wait until at least the first film and the second film disintegrate in liquid formulation comprising water. This process is assisted via mechanical shearing. After disintegration of the first and the second films, the electronics circuit detaches and may be reused (if appropriate) or recycled.

[0076] The wating time for complete disintegration of the first and the second films may be 5 - 200 min. In order to accelerate the disintegration, the volume of liquid formulation with the electronics device may be mechanically stirred.

[0077] Example of the flexible electronics device preparation and recycling

[0078] 1 ) The first film may be formed of a first material whose composition is given as: cellulose nanofibrils 50 parts per hundred (pph), hydroxyethyl cellulose (HEC) 50 pph, D-sorbitol 20 pph, alkyl ketene dimer 2 pph.

[0079] 2) The first film may then be screen printed on the top surface with conductive tracks using an ink composed of carbon black and a latex binder. 3) The electronics components may then be placed at the top surface of the first film aligned according to the printed circuit layout. The components may be capacitors, resistors, microprocessors, LEDs, and transistors. The electrical contact between the components and the printed conductive tracks is ensured by applying a small amount of conductive adhesive to the bottom of the component before placing it on the first film. Alternatively, a small amount of conductive adhesive may be applied to the printed conductive tracks in places where the components are placed.

[0080] 4) The second film may be formed of a second material whose composition is given as: cellulose nanofibrils 100 parts per hundred (pph), carboxymethyl cellulose (CMC) 5 pph, alkyl ketene dimer 2 pph.

[0081] 5) The second film may be formed at the top surface of the first film and over the electronics circuits, in order to encapsulate and protect the circuit. The second film may be formed using a wet-on-dry approach where the second material formulation is sprayed over a dried first film carrying the electronics circuit, and the sprayed liquid is dried using heat to form a film.

[0082] 6) Both the first and the second films may be disintegrated in the liquid formulation comprising water by submerging the electronics device in the liquid formulation and soaking for 10 min. Thereafter, mechanical shearing may be applied using a mixer which disintegrates both films and releases the encapsulated electronic components which may be reused or recycled.

[0083] Alternatively, in the example of the electronics device preparation and recycling detailed above, the first material may have composition of: cellulose nanofibrils 60 pph, hydroxypropyl cellulose (HPC) 40 pph, glycerol 10 pph, alkyl ketene dimer 2 pph. The second material may have composition of: carboxymethyl cellulose (Finnfix 4000, Nouryon) 100 pph, alkyl ketene dimer 2 pph.

[0084] In the example of the electronics device preparation and recycling above, the nanocellulose fibres of the first material under the ink of the printed conductive track may be adhered to the ink strongly and may need chemical assistance in separation from the ink. Acetone dissolves a variety of binders and hence weakens the bonding between the fibres and the ink, so the presence of acetone in the liquid formulation may help with separation and recycling. Step 6) of the example of electronics device preparation and recycling may thus be modified as follows: 6.1 ) Both the first and the second films may be disintegrated by submerging the electronics device in a liquid formulation comprising water and acetone (80:20 ratio by mass) and soaking for 10 min. Thereafter, mechanical shearing may be applied using a mixer which disintegrates both films and releases the encapsulated electronic components which may be reused or recycled. The presence of acetone in the liquid may allow easier recycling without damaging the electronic components.

[0085] 6.2) Both the first and the second films may be disintegrated by submerging the electronics device in a liquid formulation comprising water and sodium hydroxide (95:5 ratio by mass) and soaking for 10 min. Thereafter, mechanical shearing may be applied using a mixer which disintegrates both films and releases the encapsulated electronic components which may be reused or recycled. The presence of sodium hydroxide in the liquid may soften the cellulose fibers which help in easier separation from the ink- containing areas of the electronics device.

Claims

CLAIMS1 . A wearable flexible electronics device comprising:• a first layer comprising a first film, wherein the first film is formed of a first material, and wherein the first layer comprises a top surface,• an electronics circuit, wherein the electronics circuit is at the top surface of the first layer, characterized by that it further comprises:• a second layer comprising a second film, wherein the second film is formed of a second material, and wherein the second film is at the top surface of the first layer in contact with the electronics circuit, and wherein the first film and the second film are disintegrable in a liquid formulation, wherein the liquid formulation comprises water.

2. The wearable flexible electronics device of claim 1 , wherein the electronics circuit comprises a number of electronics components, and each electronics component is surrounded by the second film.

3. The wearable flexible electronics device of claim 1 or 2, wherein the electronics circuit is embedded into the second film.

4. The wearable flexible electronics device according to any preceding claim, wherein the second material is a cellulosic composition.

5. The wearable flexible electronics device according to any preceding claim, wherein the first material and the second material are the same.

6. The wearable flexible electronics device according to any preceding claim, wherein concentration of water in the liquid formulation is 1 - 100%.

7. A method of fabricating the wearable flexible electronics device, comprising the steps of:• forming a first layer by depositing a first film of a first material in liquid state on a support surface, and curing the first film,• placing an electronics circuit into an electronics region on a top surface of the first layer, • forming a second layer by depositing a second film of a second material in liquid state on the top surface of the first layer in contact with the electronics circuit, and curing the second film, and wherein the first film and the second film are disintegrable in a liquid formulation, wherein the liquid formulation comprises water.

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