Stretchable structure comprising a conductive path and a method for manufacturing the structure

#This application is a U.S national application of the international application number PCT/F12017/050670 filed on Sep. 25, 2017 and claiming priority of Finnish national application 20165724 filed on Sep. 27, 2016 the contents of all of which are incorporated herein by reference.

#The invention relates to a stretchable structure comprising or configured to receive a conductor, advantageously a conductive path and in particularly a stretchable conductive path, and a component, where the component and the conductive path are physically coupled with each other. Especially the invention relates to the stretchable structure having an interface region for receiving and introducing said stretchable conductive path with the component in a manner to prevent any enormous or significant damages induced for the conductive path due to the stretching or twisting of the stretchable structure. In addition the invention relates to a method for manufacturing the stretchable structure.

#Current conductive materials used in stretchable electronics and structures allow some stretching, e.g. 30% stretching in length. However, when the stretchable conductive materials are used in connection with more rigid components provided on the stretchable structure, forces induced to the entity (e.g. due to stretching or twisting of the structure) are not spread uniformly, which induces some challenges. For example, controlling of the local tensions and forces, especially in an interconnection region near the rigid component and less rigid stretchable electronics and structure, are very challenging task.

#Next the invention will be described in greater detail with reference to exemplary embodiments in accordance with the accompanying drawings, in which:

#FIGS. 1A-B illustrate a principle of an exemplary prior art solutions for coupling a stretchable conductive path with a component,

#FIG. 2 illustrates an exemplary principle for coupling a stretchable conductive path with a component via an interface region according to an advantageous embodiment of the invention, and

#FIGS. 1A-B illustrate principles of an exemplary prior art solutions, where a stretchable structure 101 carries a rigid device 109 and a conductive path 102, which is coupled with the rigid device 109. In FIG. 1A mechanical interface between the conductive path 102 and the rigid device 109 is very sharp and the forces induced to the conductive path 102 in the vicinity of the rigid device 109 can be enormous and discontinuous and thereby cause easily breakage through mechanical cracking to the conductive path 102.

#FIG. 1B illustrates a prior art teardrop structure 110 used to spread the structural stress induced to the conductive path 102 more smoothly and more larger area to other portions of the stretchable structure 101 especially in the vicinity of the non-stretchable component 109 in order to reduce the structural stress induced into the conductive path 102 in the vicinity of the rigid device 109. However, also this solution has drawbacks, namely the teardrop structure 110 does not protect the conductive path 102 in the lateral direction, so when the stretchable structure 101 is e.g. twisted or stretched in the direction more or less perpendicular to the travel direction of the conductive path 102, whereupon the conductive path 102 will easily get broken or cracked due to lateral stress.

#FIG. 2 illustrates an exemplary principle for coupling a conductive path 102 with an interface region 105 in a stretchable structure 101 according to an advantageous embodiment of the invention, where the inwardly curved portion 106 surrounded and formed by the interface region 105 can be clearly seen. The form of the inwardly curved portion 106 is advantageously the form of an “inverted teardrop” or a fjord like recess pointing towards the center area of the interface region 105 even though also other forms can be applied, as described in this document. The opening angle α of the inwardly curved portion is advantageously less than 180°, or more advantageously less than 130°, or even less than 90°, so to apply the protective effect e.g. against the later stretching or twisting.