UTILITY PATENT APPLICATION

FOR

ELASTIC CIRCUIT BY

DAVID T. MARKUS MICHAEL C. HAYES

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of US Provisional Patent Application No 62/022,197, filed on 07/08/2014, and incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

Not Applicable.

FIELD OF THE INVENTION

This invention relates generally to an elastic circuit, and more particularly, to an electronic elastic circuit adapted to stretch and contract within three dimensions.

DISCUSSION OF RELATED ART

Stretchable electronics can generally be described as electronic circuits adapted to stretch in one or two dimensions. Stretchable electronics are generally embedded on a stretchable medium and are adapted to stretch with the medium without losing electrical connectivity between electronic components. Currently, single wave patterns allow such circuits to stretch, where the wave will provide the slack necessary for the circuit to expand or contract.

While current stretchable electronic circuits are adapted to stretch in one or two dimensions, there is currently no stretchable electronic circuit adapted to provide three- dimensional elasticity. Therefore, there is a continued need for an elastic circuit adapted to provide three-dimensional elasticity. The present invention satisfies this need.

SUMMARY OF THE INVENTION

The present invention is an elastic electronic circuit adapted to provide three-dimensional elasticity. This is accomplished through implementing a first pattern, a second pattern embedded within the first pattern, and a third pattern onto a circuit. The three-dimension elastic electronic circuit is adapted to conform to a flexible substrate, such as flexible plastic substrates and the like. The resulting three-dimensional elasticity enables the use of electronic circuits on such flexible substrates.

In a first embodiment, the first pattern of the elastic circuit comprises a generally horseshoe-shaped pattern and provides elasticity along the x-axis. The second pattern of the elastic circuit is embedded within the first pattern and provides elasticity along the y- axis. The third pattern is applied to the surface of the elastic circuit and provides elasticity along the z-axis. The third pattern will further be adapted to conform to the surface of the flexible substrate.

These and other objectives of the present invention will become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiments. It is to be understood that the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a horseshoe patterned circuit in one dimension;

FIG. 2 is a diagram illustrating a horseshoe pattern in greater detail;

FIG. 3 is a diagram illustrating a horseshoe patterned circuit in two dimensions;

FIG. 4 is a diagram illustrating a horseshoe patterned circuit in three dimensions;

FIG. 5 is a diagram illustrating a planar mold;

FIG. 6 is a diagram illustrating a non-planar mold; FIG. 7 is a diagram illustrating an unfolded elastic circuit; FIG. 8 is a diagram illustrating a folded elastic circuit;

FIG. 9 is a diagram illustrating an unfolded and folded circuit with equation; and FIG. 10 is a diagram illustrating a folded structure in a flexible substrate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Illustrative embodiments of the invention are described below. The following explanation provides specific details for a thorough understanding of and enabling description for these embodiments. One skilled in the art will understand that the invention may be practiced without such details. In other instances, well-known structures and functions have not been shown or described in detail to avoid

unnecessarily obscuring the description of the embodiments.

Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise," "comprising," and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to." Words using the singular or plural number also include the plural or singular number respectively. Additionally, the words "herein," "above," "below" and words of similar import, when used in this application, shall refer to this application as a whole and not to any particular portions of this application. When the claims use the word "or" in reference to a list of two or more items, that word covers all of the following interpretations of the word: any of the items in the list, all of the items in the list and any combination of the items in the list.

The present invention discloses an elastic electronic circuit 10 adapted to provide three- dimensional elasticity, which can conform to a curved structure of a flexible substrate 20. The elastic circuit 10 comprises a first pattern 30, a second pattern embedded within the first pattern 40, and a third pattern 50 adapted to conform to a curved structure of a flexible substrate 20. The elastic circuit 10 is adapted to attach or be embedded within flexible polymers and/or non-flexible polymers, specifically plastic substrates, and is adapted to provide electrical connection on or within said substrates. Furthermore, the electronic circuit 10 must not negatively impact or adversely affect the intended purpose of the flexible substrate 20.

The first pattern 30 of the elastic circuit 10 is adapted to provide elasticity in a first dimension, or an X-dimension. The first pattern 30 is attached and/or embedded within flexible substrate polymer 20 and further comprises a pattern path 62, pattern width, an overall width, a radius of curvature 65, and a turning degree offset 63. In the preferred embodiment, the first pattern comprises semicircles which form a generally horseshoe pattern 61. The turning degree offset 63 will range between 30 and 60 degrees, as each partial circle will not share a center line 64. The horseshoe shaped pattern interconnects maintain their recurring shape by having different turning degrees at each connection point. In an alternative embodiment, the first pattern is a sine wave 71. In a further alternative embodiment, the first pattern is a square wave 72. In yet a further alternative embodiment, the first pattern is a triangle wave 73.

The second pattern 40 of the elastic circuit 10 is embedded within the first pattern 30 and is adapted to provide elasticity in a second dimension, or a Y-dimension. The second pattern 40 will follow the pattern path 62 of the first pattern 40, but provides a second pattern 40 within the first pattern 30. In the preferred embodiment, the second pattern 40 is identical to the first pattern 30, albeit smaller in scale. Specifically, the second pattern 40 comprises semicircles which form a generally horseshoe pattern 61. In an alternative embodiment, the second pattern 40 is a sine wave 71. In a further alternative

embodiment, the second pattern 40 is a square wave 72. In yet a further alternative embodiment, the second pattern 40 is a triangle wave 73.

The third pattern 50 of the elastic circuit 10 is adapted to provide elasticity in a third dimension, or a Z-dimension. The third pattern 50 is applied to the flexible substrate polymer 20 to which the elastic circuit 10 is attached/embedded and further comprises a radius of curvature 65 and a turning degree offset 63. In the preferred embodiment, the third pattern 50 comprises semicircles which form a generally horseshoe pattern 61. The turning degree offset 63 will range between 30 and 60 degrees, as each partial circle will not share a center line 64. The horseshoe shaped interconnects maintain their recurring shape by having different turning degrees at each connection point. In an alternative embodiment, the third pattern 50 is a sine wave 71. In a further alternative embodiment, the third pattern 50 is a square wave 72. In yet a further alternative embodiment, the third pattern 50 is a triangle wave 73.

The third pattern 50 is best represented by a cross-sectional view of the elastic circuit 10. Here, the third pattern 50 can be plainly seen, with the first and second patterns 30, 40 positioned at the surface of the pattern. The third pattern 50 can be further adapted to conform to a curved structure of a curved fiexible substrate 21. As such, the third pattern 50 can be adapted to not extend linearly, but rather, the third pattern 50 would follow a generally curved structure of the curved fiexible substrate 21, wherein the horseshoe patterns 61 on the convex side of the curved structure 21 are generally further apart and the horseshoe patterns 61 on the concave side of the curved structure 21 are generally closer together.

The first step when manufacturing the present invention is to create the flexible substrate 20. Here, a mold is patterned with grooves according to the third pattern 50 as shown in Figs. 5 and 6 for planar and non-planar molds, respectively. The pattern substrate is cast onto the mold by electro spray, spin on coating, or deposited by chemical vapor deposition. The mold is chemically or mechanically removed to obtain the patterned flexible substrate 20. Next, in order to fabricate the first and second patterns 30, 40, the patterned flexible substrate 20 is molded or etched away. For molding, a negative pattern is created on the mold, which is then filled with the substrate material and cured. The mold is then removed to obtain the patterned substrate 20. For etching, several methods can be used, including: direct laser etching, chemical etching, photodefinable etching by direct photo patterning, and plasma etching.

For laser etching, the pattern design is entered into a software laser controller program, where a laser head is controlled using gimbals head, xyz axis stages and rotation stages. No masking material is needed; the laser will etch along the border or perimeter of the pattern. For chemical etching, the pattern is transferred onto the substrate 20 using photoresist and photolithography. The substrate 20 is soaked into a chemical etchant that can selectively etch the substrate 20 and the photoresist at a different etch rate. The photoresist is rinsed off after the wet etching is complete.

For photodefinable etching by direct photo patterning, the substrate material 20 is photosensitive to UV light and a photomask or direct laser UV pattern is used to create the first and second patterns 30,40 in a photo developer. For plasma etching, the substrate 20 will have a thin coating of metal film ranging from 0.1 um to 10 um. The first and second patterns 30, 40 are transferred onto the substrate 20 using photoresist and photolithography, where the substrate 20 is soaked into a chemical enchant that can selectively etch the metal film and the photoresist at different etch rates or can use ion- milling or a reactive ion etcher for etching the metal. The substrate 20 with a metal mask is placed into the reactive ion etcher with a different gas such as oxygen or CF4 to etch away the substrate 20. The photoresist and metal mask are removed after the substrate 20 is patterned.

Whether using molding or etching, an alternative embodiment comprises creation of an unfolded structure having end points A and B (Fig. 9). All existing semiconductors and components can be used during fabrication, and planar photolithography and/or laser cutting can further increase cost savings during manufacture. Here, the unfolded circuit 11 is mechanically joined at points A and B through soldering, epoxy, welding, or a mechanical snap (Fig. 9). The resulting structure can be convex with a layout conformal to curved surface of a flexible substrate. Generally, the radius of the unfolded structure is larger than that of the folded structure, R(unfolded) = 1.312*R(folded). This is assuming the angle of the folded structure is 40.475 degrees. The circumference will remain the same.

Once the first, second, and third patterns 30, 40, 50 are created, the electronic circuit 10 can be completed. Here, the patterns operate as electrical interconnections and the electrical components are inserted between these electrical interconnections.

Components include resistors, capacitors, LEDs, amplifiers, transistors, and other electronic chips. Furthermore, the first, second, and third patterns 30, 40, 50 may include first and third insulating layers and a second conductive layer. Once the electronic circuit 10 is created, it is attached and/or embedded within a flexible substrate 20. The electronic circuit can be attached to the flexible substrate 20 using any conventional method, and can be attached to the flexible substrate 20 during an extrusion process, an injection molding process, or other molding process used to form the flexible substrate 20. The electronic circuit 10 can also be applied to the flexible substrate 20 after the flexible substrate 20 is formed, such as by using an adhesive and the like.

Examples of flexible substrate 20 materials include plastics such as polypropylene and the like. Non-flexible substrate materials comprise metals, ceramics, and crystals.

While the above description contains specific details regarding certain elements, sizes, and other teachings, it is understood that embodiments of the invention or any combination of them may be practiced without these specific details. Specifically, although certain materials and shapes are designated in the above embodiments, any suitable materials or shape may be used. These details should not be construed as limitations on the scope of any embodiment, but merely as exemplifications of the presently preferred embodiments. In other instances, well known structures, elements, and techniques have not been shown to clearly explain the details of the invention.

The above detailed description of the embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise form disclosed above or to the particular field of usage mentioned in this disclosure. While specific embodiments of, and examples for, the invention are described above for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. Also, the teachings of the invention provided herein can be applied to other systems, not necessarily the system described above. The elements and acts of the various embodiments described above can be combined to provide further embodiments.

Changes can be made to the invention in light of the above "Detailed Description." While the above description details certain embodiments of the invention and describes the best mode contemplated, no matter how detailed the above appears in text, the invention can be practiced in many ways. Therefore, implementation details may vary considerably while still being encompassed by the invention disclosed herein. As noted above, particular terminology used when describing certain features or aspects of the invention should not be taken to imply that the terminology is being redefined herein to be restricted to any specific characteristics, features, or aspects of the invention with which that terminology is associated.

While certain aspects of the invention are presented below in certain claim forms, the inventor contemplates the various aspects of the invention in any number of claim forms. Accordingly, the inventor reserves the right to add additional claims after filing the application to pursue such additional claim forms for other aspects of the invention.