KR102070996B1 - Method for manufacturing flexible element including ceramic film using printing and laser sintering process - Google Patents

Abstract

According to the present invention, a manufacturing method of a flexible element including a ceramic film comprises: (a) a step of forming a sacrificial layer on a substrate; (b) a step of forming a ceramic layer on the sacrificial layer by an aerojet-printing method; (c) a step of laser-sintering the ceramic layer; (d) a step of removing the sacrificial layer to separate the ceramic layer from the substrate; and (e) a step of embedding the separated ceramic layer in a flexible material. According to the present invention, the ceramic layer is formed by aerojet-printing, and then a ceramic film with excellent electromagnetic properties is manufactured by a laser-sintering process instead of a high-temperature sintering process requiring a long period of time to realize a flexible electronic element with excellent performance while using reduced costs and a simplified process in comparison to a conventional technique.

Description

METHODS FOR MANUFACTURING FLEXIBLE ELEMENT INCLUDING CERAMIC FILM USING PRINTING AND LASER SINTERING PROCESS}

The present invention relates to a method of imparting flexibility to a ceramic film, and more particularly, to a method of manufacturing a flexible device including a ceramic film.

Recently, the demand for various flexible devices for application to wearable portable electronic devices, large area electronic devices, and the Internet of Things is rapidly increasing. As a result, various studies have been conducted to develop high-efficiency, small-capacity energy supplies with light, bendable, collapsible, and highly flexible properties. Particularly, harvesting energy at radio frequencies can be applied to multiple electronic devices simultaneously without physical contact. It is a new technology that attracts considerable attention because it can be supplied in the form of power.

This concept of wireless power transfer (WPT) represents a desirable energy supply technology for mobile electronic devices and electric vehicles because it does not limit mobility even when charging is required. According to Markets and Markets, the WPT market is expected to expand to $ 1.27 billion by 2022 due to the technical advantages of WPT in wearable / flexible electronics and electric vehicles.

The concept of WPT has a long development history. It was first demonstrated a century ago by Nikola Tesla. Recently, significant advances have been made in the field of nonradiative WPT using magnetic resonance coupling in the near field as a power transmission mechanism. The WPT module currently used in commercial mobile electronic devices consists of a receive (Rx) coil with a high permeability flexible ferrite layer that receives wireless power from an external transmit (Tx) coil. The ferrite layer is an integral component of the WPT Rx module because the WPT Rx module in mobile electronics is inevitably close to conductive objects such as battery packs and metal cases. The ferrite layer exists to prevent magnetic fields from external Tx coils from reaching the conductive material. Without the ferrite layer, eddy currents are induced in the conductor and a cancellation field is generated, which adversely affects WPT performance. Crazy

Thus, WPT modules with inductor coil / ferrite configurations have been applied to many commercial mobile electronic devices. However, a paradigm shift towards a flexible and deformable platform in mobile electronic devices requires that the materials used in the WPT modules match future flexible and deformable electronic devices. In this respect, the ferrite layer of the WPT module faces significant technical challenges due to its brittleness.

Efforts have been made to blend the ceramic powder with a polymer binder or to impart flexibility to the ceramic layer by laminating a pre-cracked ferrite sintered film between the adhesive tape and the cover layer. However, there is a problem in that the ceramic content in the ceramic-polymer composite material is limited and cracks may occur in the ferrite layer, which is inferior in magnetic performance as compared with the fully sintered hard ceramic layer.

On the other hand, the use of a fully sintered hard ceramic layer ensures good magnetic performance, but a high temperature and time-consuming furnace-based sintering process (eg 950 ° C. and 24 hours) is indispensable. Has the disadvantage of increasing.

Korean Patent Publication No. 10-2014-0124703 (Published: October 27, 2014) Korean Patent Publication No. 10-2015-0125812 (Published: November 10, 2015) Korean Patent Publication No. 10-2017-0050971 (published: May 11, 2017)

 Z.L. Wang, W. Wu, Nanotechnology-enabled energy harvesting for self-powered micro- / nanosystems, Angew. Chem. Int. Ed. 51 (2012) 11700-11721.  J. Kim, A. Banks, Z. Xie, S.Y. Heo, P. Gutruf, J.W. Lee, S. Xu, K.I. Jang, F. Liu, G. Brown, J. Choi, J.H. Kim, X. Feng, Y. Huang, U. Paik, J.A. Rogers, Miniaturized flexible electronic systems with wireless power and near-field communication capabilities, Adv. Funct. Mater. 25 (2015) 4761-4767.  A. Kurs, A. Karalis, R. Moffatt, J.D. Joannopoulos, P. Fisher, M. Soljacic, Wireless power transfer via strongly coupled magnetic resonances, Science 317 (2007) 83-86.  C.A. Stergiou, V. Zaspalis, Impact of ferrite shield properties on the low-power inductive power transfer, IEEE Trans. Magn. 52 (2016) 8401609.

The technical problem to be solved by the present invention is to provide a method for manufacturing a flexible film-containing flexible device through a significantly simplified low-cost process while maintaining the performance of the conventional flexible device containing a fully sintered ceramic film.

In order to achieve the above technical problem, the present invention (a) forming a sacrificial layer (sacrificial layer) on the substrate; (b) forming a ceramic layer on the sacrificial layer by an aerojet printing method: (c) laser sintering the ceramic layer; (d) removing the sacrificial layer to separate the ceramic layer from the substrate; And (e) embedding the separated ceramic layer in a flexible material.

In addition, the substrate proposes a method of manufacturing a flexible device including a ceramic film, characterized in that made of glass or silicon.

In addition, the material forming the ceramic layer proposes a method of manufacturing a flexible device including a ceramic film, characterized in that the ferrite (ferrite).

In addition, the ferrite is a Ni-Zn-based ferrite, Mn-Zn-based ferrite, Ni-Zn-Cu-based ferrite, Mn-Mg-based ferrite, Ba-based ferrite or Li-based ferrite flexible device comprising a ceramic film We propose a method of manufacturing.

In addition, in the step (c) it is proposed a method of manufacturing a flexible device comprising a ceramic film, characterized in that at the same time to sinter the ceramic layer through laser sintering to form a microcrack in the ceramic layer.

In addition, the step (d) proposes a method of manufacturing a flexible device comprising a ceramic film, characterized in that to remove the sacrificial layer made of a metal with an etching solution to separate the ceramic layer from the substrate.

In addition, in the step (d) it is proposed a method of manufacturing a flexible device comprising a ceramic film, characterized in that the cured after impregnating the separated ceramic layer in a solution containing a flexible material.

In another aspect, the present invention proposes a flexible device including a ceramic film manufactured by the method.

In addition, the ceramic film proposes a flexible device including a ceramic film, characterized in that made of ferrite.

In another aspect of the invention, the present invention proposes a WPT system including the flexible device.

According to the present invention, after forming the ceramic layer through aerojet printing (aerojet-printing), a ceramic film having excellent electromagnetic properties through a laser sintering (laser-sintering) process instead of a high temperature sintering process that requires a long time By manufacturing, it is possible to realize a high performance flexible electronic device having excellent electromagnetic properties while using a much lower cost and a simplified process as compared with the conventional art.

1 is a schematic diagram showing a process for manufacturing a LSNZF film (PDMS-embedded LSNZF film) embedded in PDMS according to an embodiment of the present application.
FIG. 2 (a) is the light transmittance (T) and reflectance (R) spectra at wavelengths 400-2000 nm of the aerojet printed NZF film, and FIG. 2 (b) is an aerojet printed NZF calculated from the T and R It is a graph showing the optical bandgap energy of the film.
FIG. 3 (a) shows the results of XRD analysis of LSNZF film at various laser fluence values from 32 to 96 J / cm ² , and FIG. 3 (b) shows the particle size of LSNZF film measured from XRD as a function of laser fluence value. It is a graph.
4 is a planar image (optical micrograph) and cross-sectional image (SEM photograph) of LSNZF film showing microstructural changes with laser fluence value changes (51, 64 and 96 J / cm ² ).
5 is an image analysis result of microcrack density expressed as a function of laser fluence (black and white image converted from the original color image is used to calculate the amount of microcracks; fine crack density is an image of size 567 × 424 µm) In white divided by the total number of pixels).
6 (a) is a graph of frequency-complex permeability according to the laser fluence change of the PDMS embedded LSNZF film, and FIG. 6 (b) is the MH hysteresis curve according to the laser fluence change of the PDMS embedded LSNZF film.
7 is a graph showing the real part permeability, micro crack density (%) and micro grain size measured from XRD of the PDNZ embedded LSNZF film as a function of laser fluence.
8 (a) is a graph showing the normalized real permeability real permeability (Δμ ′ / μ ′ ₀ ) according to the bending radius, and FIG. 8 (b) is normalized according to the number of bending test cycles (up to 10,000 cycles). Real part permeability real part permeability (Δμ '/ μ' ₀ ) is a graph showing, Figure 8 (c) and Figure 8 (d) is a cross-sectional photograph of the PDMS embedded LSNZF film before and after the 10,000 cycle bending test, respectively.
Figure 9 (a) is a schematic diagram showing the formation process of the Ag spiral inductor coil, Figure 9 (b) is a photograph of a flexible WPT Rx module including LSNZF film, Figure 9 (c) and Figure 9 (d) is bent and Tx This shows the WPT performance of the Rx module at 6.78MHz at a distance of 7cm.
10 is a photograph showing the WPT performance of the flexible Rx module with and without LSNZF near the Cu conduction plate, respectively.
FIG. 11 is a graph showing WPT efficiency (Rx power / Tx power) according to the distance between Rx and Tx in a flexible Rx module having LSNZF film.

In the following description of the present invention, if it is determined that detailed descriptions of related known functions or configurations may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

Embodiments according to the concepts of the present invention may be variously modified and may have various forms, and specific embodiments will be illustrated in the drawings and described in detail in the present specification or application. However, this is not intended to limit the embodiments in accordance with the concept of the present invention to a particular disclosed form, it should be understood to include all changes, equivalents, and substitutes included in the spirit and scope of the present invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. As used herein, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, action, component, part, or combination thereof that is described, and that one or more other features or numbers are present. It should be understood that it does not exclude in advance the possibility of the presence or addition of steps, actions, components, parts or combinations thereof.

Hereinafter, the present invention will be described in detail.

The present invention provides a flexible device including a ceramic film that can be used to manufacture a high performance free-standing ceramic film through a simple, low-cost process, and then give flexibility thereto to manufacture various flexible electronic devices. It is about a manufacturing method.

Specifically, the method for manufacturing a flexible device including a ceramic film according to the present invention includes: (a) forming a sacrificial layer on a substrate; (b) forming a ceramic layer on the sacrificial layer by an aerojet printing method: (c) laser sintering the ceramic layer; (d) removing the sacrificial layer to separate the ceramic layer from the substrate; And (e) embedding the separated ceramic layer in a flexible material.

In the step (a), the sacrificial layer and the ceramic layer are sequentially formed on a hard substrate made of glass, silicon (Si), or the like.

The sacrificial layer is temporarily present between the substrate and the ceramic layer until the sacrificial layer is removed in a separation step between the ceramic layer and the substrate to be described later, and then removed through physical or chemical processes after laser sintering of the ceramic layer is completed.

The sacrificial layer may be made of a metal, for example, and the sacrificial layer made of the metal may be removed using an etchant corresponding to the metal material in a separation step between the ceramic layer and the substrate below. For example, when the sacrificial layer is made of silver (Ag), it is possible to use Nital, an alcohol solution containing nitric acid, as an etching solution.

Next, in step (b), a ceramic layer is formed on the sacrificial layer by an aerojet printing method.

The ceramic layer is separated from the substrate in step (d) by laser sintering in step (c), which will be described later, and becomes a free-standing ceramic film, which is embedded in a flexible material to perform a core function of the device.

In the step (b), the ceramic layer may be formed through an aerojet printing method among printed electronics.

Aerojet printing is a non-contact patterning method in which nanoparticles are uniformly dispersed in a carrier gas and then aerodynamically focused to deposit nanoparticles on a certain portion. The process can be easily developed for various materials and the process can be performed at a high speed for a large area.

The ceramic layer may be made of a functional ceramic material having excellent electromagnetic, mechanical, and optical properties. For example, the ceramic layer may be made of a magnetic ceramic such as ferrite.

For reference, the ferrite is a general term for a ceramic magnetic material containing iron oxide (Fe ₂ O ₃ ) as a main component, bivalent, such as MO · Fe ₂ O ₃ (M: Mn, Zn, Mg, Fe, Cu, Co, etc.) Metal), and Ni-Zn-based ferrites, Mn-Zn-based ferrites, Ni-Zn-Cu-based ferrites, Mn-Mg-based ferrites, Ba-based ferrites, Li-based ferrites, and the like.

Subsequently, in step (c), the ceramic layer is laser sintered.

In the step (c), the microstructure of the ceramic layer is densified through laser sintering, and at the same time, microcrack is formed in the ceramic layer due to the rapid heating by the laser and the high porosity of the aerojet printed film. Likewise, the microcracks formed during laser sintering play an important role in imparting flexibility to the ceramic film rather than negatively affecting the ceramic film as a defect.

In the step (d), the sacrificial layer may be removed to separate the ceramic layer from the substrate. For example, as described above, the sacrificial layer made of metal may be removed with an etchant to separate the ceramic layer from the substrate.

Finally, in step (e), the process of embedding the sintered ceramic layer in the flexible material is performed, and the specific method is not particularly limited. For example, the sintered ceramic layer is impregnated in the flexible material-containing solution. It may be made through a post-curing process.

In the method of manufacturing the flexible device including the ceramic film according to the present invention described above, after the ceramic layer is formed through aerojet-printing, laser sintering is used instead of the high temperature sintering process requiring a long time. By manufacturing a ceramic film having excellent electromagnetic properties through a sintering process, it is possible to implement a flexible electronic device having excellent performance while using a much lower cost and a simplified process than in the related art.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Embodiments according to the present disclosure may be modified in many different forms, and the scope of the present disclosure is not to be construed as limited to the embodiments described below. The embodiments of the present specification are provided to more fully describe the present specification to those skilled in the art.

<Example>

1. LSNZF Film Preparation by Aerojet Printing and Infrared (IR) Laser Sintering

NZF nanoparticles (Amotech) with a composition of Ni _0.4 Zn _0.6 Fe ₂ O ₄ (average particle size: 500 nm) were added together with the dispersant (BYK111) to make printable NZF (NiZn-ferrite) inks. , Boiling point: 217 ° C., density: 0.93 g / mL at 25 ° C.). NZF solid phase content was maintained at 40% by weight throughout the experiment. Ink dispersion was obtained through mechanical homogenization and ultrasonic homogenization processes. Prior to Aerojet printing (Musashi), a 6 μm syringe filter was used to remove the aggregates remaining in the ink.

An NZF film of 46 × 46 mm size was printed on a glass substrate (50 × 50 mm). The print pitch and the number of prints were controlled to fix the NZF film thickness to 20 μm. An Ag sacrificial layer was introduced between the NZF film and the glass substrate so that the NZF film could be separated from the substrate after laser sintering. A thin Ag layer (1.5 μm) was aerojet printed onto the entire substrate using a commercial Ag ink (ie ANP). Then, a continuous-wave (CW) diode pumped IR laser (λ = 808 nm, LDC-030XTF, Losyn Yepli) was attached to the print nozzle so that laser sintering could be performed using the same printer. The entire area of the NZF film was irradiated with a scanning laser beam having an effective focusing beam size of 200 μm.

The laser power was varied in terms of fluence (J / cm ² ) to determine the optimal laser sintering conditions at a laser scan rate of 10 mm / s. The aerojet printing and laser sintering process of the NZF film is schematically illustrated in FIGS. 1 (a) and 1 (b).

In fact, laser wavelength and laser fluence should be taken into account when determining the optimal laser sintering conditions for ceramic insulating films. Laser photon absorption by ceramic films occurs primarily through interband electron transitions that require laser photon energy greater than the band gap of the film. The light bandgap ( E _g ) of the aerojet printed NZF film was derived from the light absorption coefficient (α) associated with the interband electron transition of the material based on the following equations.

Where hν is incident photon energy, A is constant, t, T and R are the thickness, transmittance and reflectance of the film, respectively. Figure 2 shows the optical transmission and reflection spectra of the Aerojet printed NZF film and the bandgap energy extraction from Eq. (1) above.

The Eg of the aerojet printed NZF film thus obtained is 1.45 eV, which is consistent with previously reported values. The photon energy of the laser (λ = 808 nm) used in this example was 1.53 eV, which is larger than the band gap of the NZF film, leading to interband electronic transition.

The absorption of photon energy by interband electron transitions is typically controversial with respect to interband electron transitions as it typically occurs within the top 10% of the film thickness. The photon energy absorption depth (or penetration depth, d), defined as the depth of laser drops to 36% of its initial intensity and is inversely proportional to α ( d = 1 / α), is 2.2 μm for NZF films with a thickness of 20 μm. Although limited, this does not mean that the entire film is not affected by the laser. It has been reported that the penetration depth increases with respect to the uneven microstructure of the film. The packing density calculations showed that the pores contained more than 50% of the pores of the printed NZF film. Similar studies showed that similar porosity was observed for the printed ceramic films. These pores allow multiple internal reflections on the surface of the nanoparticles inside the film, leading to deeper penetration of the laser. Even if the effective penetration depth is kept shorter than the film thickness, thermal diffusion plays an important role in sintering the remainder of the film beyond the penetration depth. The heat diffusion length (x) of the NZF film was determined to be 272 μm using the following equation (3).

Where k, ρ, and C _p are the thermal conductivity of NZF (6.3 W / (mK)), density (4.8 x 10 ³ kg / m ³ ), and specific heat capacity (710 J / (kgK)), respectively, τ Is the laser interaction time (beam size / scan rate = 20 ms). Analysis based on penetration depth and thermal diffusivity means that the entire aerojet printed NZF film is affected by sintering with a 808 nm laser. Since laser sintering is dependent on the amount of photon energy absorbed, laser fluence, which determines photon energy absorption, is an important parameter of laser sintering.

In order to investigate the effectiveness of laser sintering, the magnetic and structural properties of the aerojet printed NZF film were examined after the sintering process with various laser fluence values in the following Experimental Examples.

2. Preparation of LSNZF Film (PDMS-embedded LSNZF Film) Embedded in PDMS

Schematics of the process performed to insert the LSNZF film in the PDMS layer to give flexibility are shown in FIGS. 1 (c) to 1 (f).

First, the PDMS solution was poured onto the LSNZF film on the Ag / glass substrate in a Petri dish as in FIG. 1 (c). PDMS solution was prepared by mixing the curing agent and PDMS base in a ratio of 10: 1. First, the Petri dish was transferred to a vacuum desiccator to remove bubbles from the PDMS and then placed in an oven at 80 ° C. for 30 minutes to cure the PDMS. After curing, the peripheral portion of the PDMS was cut along the Ag sacrificial layer around the LSNZF film to expose the Ag sacrificial layer to the outside (FIG. 1 (d)). The entire structure on the substrate was immersed in Ag etchant (TFS, Transene) for 15 minutes to remove the Ag sacrificial layer. When the sacrificial layer was dissolved in the etchant, the LSNZF film embedded in the PDMS was separated from the glass substrate (FIG. 1 (f)). The overall thickness of PDMS including LSNZF film was fixed at 800 μm.

Experimental Example

1. Observation of structural, morphological and magnetic properties of LSNZF film embedded in PDMS

FIG. 3 (a) shows the results of XRD analysis on LSNZF films with various laser fluence values up to 96 J / cm ² before separation from the glass substrate and embedding in the PDMS layer. The diffraction pattern corresponds to a spinel ferrite structure with a preferential orientation of 311. It can be observed that the peak intensity increases with increasing laser fluence up to 64 J / cm ² . However, it was observed that the peak intensity no longer increased with higher fluence values. This was confirmed by the tendency of the fine crystallite mean size ( D _c ) of the LSNZF film as shown in FIG. 3 (b). The value of D _c was calculated using the Scherrer equation.

Λ, β, and θ, respectively, represent the wavelength, half width (FWHM) value, and diffraction angle of the peak (311) used in the XRD.

Large changes in the surface morphology of the LSNZF film were observed due to laser sintering. Not only the color of the NZF film gradually changed, but also many fine cracks occurred in the film, which increased as the laser fluence increased as shown in FIG. 4. The color change from brown to black (FIG. 1 (b)) is also commonly observed in conventional thermal sintering at optimum temperatures, indicating that the film has undergone adequate sintering.

However, it should be noted that color changes in laser sintering occur gradually with laser fluence. A complete change to black was observed at laser fluences of 64 J / cm ² or greater, indirectly indicating that at least the laser fluence is necessary for sintering the NZF film. Microcracks in LSNZF films, which can cause potential concerns with respect to the magnetic performance of ferrite films, constitute a notable change in morphology. However, in the flexible WPT module pursued by the present invention, microcracks may play an important role in providing flexibility to the ceramic film. Companies such as TDK (Japan) and W ㆌ rth Elektronik (Germany) intentionally introduce cracks into sintered ferrite sheets and then laminate them with protective films to produce flexible sintered ferrite sheets. Therefore, the laser sintering process used in the present invention is a very efficient process that simultaneously induces sintering and cracking, which is suitable for LSNZF film implementation in flexible WPT modules. Before discussing the effects of microcracks on the magnetic properties and flexibility of materials, let's first examine the effects of laser fluence on microcracks formation. These microcracks are due to localized transient heating and cooling of the laser spot irradiated to the as-printed porous film after printing. The local temperature gradient of the porous film (porosity> 50%) can cause thermal stress gradients associated with local volumetric shrinkage of the film, which can lead to microcracks. The development of microcracks by laser fluence was investigated by measuring the amount of microcracks using image analysis software (Clemex Vision-Professional Edition Version 5.0, Clemex Technology). After laser sintering at various laser fluence values, optical images of the NZF film were taken and converted to black and white images. The density of the microcracks was calculated by counting the number of white pixels and dividing by the number of pixels in the overall image. The crack density was found to increase with increasing laser fluence as shown in FIG. 5. The width of the microcracks was also observed to increase with increasing laser fluence.

Despite microcracks by laser sintering of LSNZF films, it should be ensured that these films have sufficient magnetic properties for WPT applications. The inductance of the film was measured to investigate the complex permeability ( μ ^* = μ′−μμ ″) of the LSNZF film with PDMS. For permeability measurements, LSNZF films with PDMS were laser cut into toroidal shapes with outer and inner diameters of 19.6 and 5.4 mm, respectively. Because of the possibility of deformation of LSNZF films with PDMS embedded, two hard epoxy toroid supports were used to wind a copper coil around the LSNZF toroid core. The real permeability μ ' and imaginary permeability μ ″ of the specimens were calculated using the equation

Where L _eff and R _eff correspond to the equivalent inductance and resistance of the LSNZF toroid core, respectively, and L _W and R _W represent the inductance and resistance of the toroidal coil without magnetic core, respectively , l, A, μ ₀ , N And ω (= 2πf ) are the average magnetic field path length, the cross-sectional area of the toroidal core, the magnetic permeability in vacuum, the coil rotation speed and the frequency, respectively. As in FIG. 6 (a), the complex permeability ( μ ′ and μ ″ ) of the LSNZF film embedded in PDMS was measured at a frequency of 0.5-10.0 MHz as a function of laser fluence. It can be seen that the μ 'of the specimens increases to a laser fluence of 64 J / cm ² and then decreases at higher laser fluences. The highest μ 'value of 97.6 at 6.78 MHz was observed for LSNZF films embedded in PDMS with a fluence of 64 J / cm ² , similar to previously reported values. The imaginary part of the complex permeability is very small ( μ ′ <5) for all specimens. This indicates that all PDMS embedded LSNZF films have negligibly low magnetic losses ( tanδ _μ (= μ ″ / μ ′ ) <0.044 at 6.78 MHz). In order to better understand the change in magnetic properties with laser fluence, the magnetization ( M ) of PDMS embedded LSNZF film was measured as a function of magnetic field ( H ) at room temperature. The MH curve in FIG. 6 (b) shows that all LSNZF films have a narrow hysteresis curve with small coercivity typical of soft magnetic materials. Saturation magnetization ( M _S ) of the NZF film increased to a laser fluence of 64 J / cm ² and decreased for higher laser fluences due to the change in crystal size associated with laser sintering. M _S of the NZF film laser-sintered at 64 J / cm ² was 309 emu / cm ³ (4π × 10 ⁻⁴ M _S = 0.39 T).

To understand how the structural and morphological changes due to laser sintering affect the overall magnetic properties of PDMS embedded LSNZF films, real permeability data along with fine crystallite size and fine crack density Shown as a function of laser fluence (FIG. 7). As previously discussed, the apparent color change to black occurred at a laser fluence of 64 J / cm ² . Fine crack densities continued to increase with increasing laser fluence. However, the permeability was not affected by microcracks up to the fluence value of 64 J / cm ² . This indicates that even with microcracks in the film, an increase in grain size up to 64 J / cm ² has a dominant effect. However, when the laser fluence was higher than 64 J / cm ² , the permeability of the film was lowered due to both a decrease in crystallite size and an increase in fine cracks. Specimens with a fluence of 96 J / cm ² have a larger fine grain size than specimens with a fluence of 48 J / cm ² , but have lower real permeability. These results indicate that when the laser fluence exceeds 64 J / cm ² , the fine crack density also contributes to the decrease in permeability.

2. Observation of mechanical properties (flexibility) of LSNZF film embedded in PDMS

The flexibility of the PDMS embedded LSNZF film was analyzed by monitoring the change in complex permeability after the cyclic bending test. The PDMS embedded LSNZF toroid core was inserted into a bending support plate consisting of a PI sheet of 150 μm thick and a PI tape of 70 μm thick as schematically shown in the inset of FIG. 8 (a). After each bending condition was completed, μ ′ and μ ″ of the LSNZF toroid core without the bending support plate were measured. This bending cycle test was made using LSNZF film with the highest real permeability at laser fluence of 64 J / cm ² .

8 (a) shows the change in normalized real permeability (Δμ ′ / μ ′ ₀ ) at various bending radii of 30-0.5 mm (almost folded). Where Δμ ' (= μ' ₀ -μ ' ) is the actual change in the real permeability after bending, μ' ₀ is the initial real permeability, and μ ' is the value measured after the bending test. The real part permeability values of FIG. 8 were obtained at a frequency of 6.78 MHz. The strain ε induced by bending in the specimen can be calculated using the equation

Where h _s1 , h _s2 and h _f are the thickness of the PI sheet, PI tape and PDMS embedded LSNZF film, respectively, and R is the bending radius of curvature. The total thickness ( h s ₁ + h _f + h s ₂ ) used in the bending test was 1.02 mm. The strain value ( ε ) associated with the bending radius increased from 30 mm to 0.5 mm, from 1.7% to 102%. At bending radii over 15 mm, the increase in Δ μ '/ μ' ₀ was less than 1%, with only a 4.2% increase at 0.5 mm (corresponding to strains above 100%), which was a good flexibility with PDMS embedded LSNZF films. Maintain magnetic properties. The mechanical stability associated with the flexibility of the PDMS embedded LSNZF film was examined by a cyclic bending test. 8 (b) shows the change in Δμ ′ / μ ′ ₀ after repeated bending tests of up to 10,000 cycles at bending radii of 15, 10 and 5 mm. For any bend radius up to 1000 cycles Δ μ '/ μ' ₀ it increasing was observed to be negligible. However, over 3000 cycles, there was a marked increase in Δμ '/ μ' ₀ . After 10,000 cycles Δμ '/ μ' ₀ increased by 2.3%, 7.1% and 15.1% at bending radii 15, 10 and 5 mm, respectively. These results provide important insight into the response of magnetic properties to the flexibility of PDMS embedded LSNZF films. Cross-sectional views of PDMS embedded LSNZF films before and after the 10,000 cycle bending test at a bending radius of 5 mm are shown in FIGS. 8 (c) and 8 (d), respectively. It can be seen from FIG. 8 (d) that delamination occurs at the NZF-PDMS interface to deteriorate the magnetic properties. Since the microcracks were filled with PDMS in the PDMS embedding process, no microcracks were observed in the PDMS embedded LSNZF film before the bending test (FIG. 8 (c)).

3. Demonstrate WPT with LSNZF Rx module with PDMS

(여기서, L은 인덕터 코일의 인덕턴스이고, C는 커패시터의 커패시턴스임)에 기반해 외부 커패시터를 사용하여 튜닝되었다. 도 9(c)와 도 9(d)에 확인할 수 있는 것처럼 유연성 WPT Rx는 구부러진 상태에서도 Tx로부터 7cm 거리에 있는 LED를 빛나게 하였다.In order to understand the applicability of LSNZF film with PDMS to the flexible WPT Rx module, the WPT performance of the flexible Rx module was investigated as shown in FIG. 9. In the WPT demonstration, a laser fluence of 64 J / cm ² was used for all specimens. Ag spiral inductor coils were inkjet printed onto PI tape and then attached to PDMS embedded LSNZF films as described in the above examples and FIG. 9 (a). At a resonant frequency ( f _r ) of 6.78 MHz, wireless power was transferred to the LEDs connected to the flexible Rx module with LSNZF film. f _r is an expression

Tuned using an external capacitor based on where L is the inductance of the inductor coil and C is the capacitance of the capacitor. As can be seen in Figures 9 (c) and 9 (d), the flexible WPT Rx glowed the LED at a distance of 7 cm from the Tx even when bent.

To demonstrate the LSNZF performance of the flexible Rx module with respect to shielding offset magnetic fields from the surrounding conductive environment, a WPT demonstration was conducted with a metal plate on the flexible Rx module with or without LSNZF film. For the comparison, only the Ag spiral inductor coil is introduced into the flexible Rx module without the LSNZF film. According to Figure 10 it is confirmed that the LED connected to the Rx module with LSNZF film is on even when the metal plate is close, while the other LED connected to the Rx module without the LSNZF film is turned off near the metal plate. These results indicate that the flexible LSNZF film successfully shields the offset magnetic field due to the eddy currents of the conductive object. Since inevitably there is a conductive object around the Rx module in WPT practical use, such shielding performance is very important for practical application to WPT.

The WPT efficiency of the flexible Rx module with LSNZF film was measured as the ratio of Rx power to Tx power. As shown in FIG. 11, the WPT efficiency was found to be 22% (Rx / Tx = 4.2 / 19.4 mW) when Rx and Tx were arranged together with zero distance. However, it can be seen that the WPT efficiency decreases rapidly as the distance between Rx and Tx increases. 11 shows the results of the WPT demonstration at a distance of 7 cm, in which the impedance matching circuit was not used. Disturbance of impedance matching due to the change in the distance distance between Rx and Tx can lead to a drastic decrease in WPT efficiency and at the same time, there is room for improvement in WPT efficiency.

Claims (10)

(a) forming a sacrificial layer on the substrate;
(b) forming a ceramic layer on the sacrificial layer by an aerojet printing method:
(c) laser sintering the ceramic layer;
(d) removing the sacrificial layer to separate the ceramic layer from the substrate; And
(e) embedding the separated ceramic layer in a flexible material;
In the step (c) characterized in that to sinter the ceramic layer through laser sintering and to form a microcrack in the ceramic layer,
Method of manufacturing a flexible device containing a ceramic film. The method of claim 1,
The substrate is a method of manufacturing a flexible device comprising a ceramic film, characterized in that made of glass or silicon. The method of claim 1,
The material forming the ceramic layer is a ferrite (ferrite) method of manufacturing a flexible device comprising a ceramic film. The method of claim 3,
The ferrite is Ni-Zn-based ferrite, Mn-Zn-based ferrite, Ni-Zn-Cu-based ferrite, Mn-Mg-based ferrite, Ba-based ferrite or Li-based ferrite manufacturing a flexible device comprising a ceramic film Way. delete The method of claim 1,
And removing the ceramic layer from the substrate by removing the sacrificial layer made of a metal with an etching solution in the step (d). The method of claim 1,
The method of manufacturing a flexible device comprising a ceramic film, characterized in that the step of (d) the separated ceramic layer is impregnated in a solution containing a flexible material and then cured. A flexible device comprising a ceramic film produced by the method according to any one of claims 1 to 4, 6 and 7. The method of claim 8,
The ceramic film is a flexible device comprising a ceramic film, characterized in that made of ferrite. A WPT system comprising the flexible element of claim 9.

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