US-12624938-B2 - Method for manufacturing strain sensor by control of thin-film crack using stress concentration structure and strain sensor manufactured using same

US12624938B2US 12624938 B2US12624938 B2US 12624938B2US-12624938-B2

Abstract

A method for manufacturing a strain sensor comprises the steps of: preparing a solution to be used as a conductive thin-film material and a flexible substrate; forming, on the flexible substrate, a stress concentration structure by repeatedly depositing a micro notch formed to have a structure having a boundary on a two-dimensional plane (the xy plane) or have a three-dimensional structure having a boundary in a direction perpendicular to the plane (the z direction); and forming a strain sensor by depositing a conductive thin film on the flexible substrate in such a way that the conductive thin film overlaps at least a portion of the stress concentration structure. Accordingly, the stress concentration structure can be manufactured at a desired location through patterning, and can be applied for various purposes by controlling the sensitivity and linearity by adjusting the arrangement of the structure and the thickness of the conductive thin film.

Inventors

Yongtaek Hong
Taehoon Kim
Daesik Kim

Assignees

SEOUL NATIONAL UNIVERSITY R&DB FOUNDATION

Dates

Publication Date: 20260512
Application Date: 20220118
Priority Date: 20210118

Claims (13)

1 . A method of manufacturing a strain sensor by control of thin-film crack using a stress concentration structure, the method comprising: preparing a solution to be used as a conductive thin-film material for the strain sensor and a flexible substrate to form the strain sensor; forming the stress concentration structure on the flexible substrate by repeatedly depositing a micro notch (MN), which is formed to have a structure having a boundary in a two-dimensional plane (xy-plane) or a three-dimensional structure having a tapered boundary in a direction (z-direction) perpendicular to the two-dimensional plane; and forming the strain sensor by depositing the conductive thin-film on the flexible substrate so as to overlap at least a portion of the micro-notch (MN), wherein in the forming of the stress concentration structure, a conduction path of current flowing through the flexible substrate is controlled by controlling a crack that is formed on the flexible substrate through an arrangement of micro notches.
2 . The method of claim 1 , wherein in the forming of the stress concentration structure, the stress concentration structure is patterned into an array structure that has a predetermined spacing in a form of a bar.
3 . The method of claim 1 , wherein in the forming of the stress concentration structure, as a spacing between micro notches gets closer, cracks at the boundary of the stress concentration structure merge together to determine a growth length of the crack, and the crack blocks the conduction path to reduce a current flow.
4 . The method of claim 1 , wherein in the forming of the stress concentration structure, the micro notch having a sharp boundary is formed using at least one of processes of printing, molding, deposition, and photolithography.
5 . The method of claim 1 , wherein in the forming of the strain sensor by depositing the conductive thin-film, a change in resistance in response to stress in the conductive thin-film is controlled.
6 . The method of claim 5 , wherein in the forming of the strain sensor by depositing the conductive thin-film, a length and growth rate of the crack on the conductive thin-film is controlled by adjusting a number and length of micro notches and a thickness of the conductive thin-film.
7 . The method of claim 6 , wherein in the forming of the strain sensor by depositing the conductive thin-film, a conduction path of the conductive thin-film is controlled by controlling the length and growth rate of the crack in the conductive thin-film.
8 . The method of claim 1 , further comprising: rinsing with deionized water; and drying with a hot plate, when a single-walled carbon nanotube ink (SWCNT ink) is used.
9 . The method of claim 1 , wherein the conductive thin-film material comprises at least one of silver nanowires (AgNWs), a single-walled carbon nanotube (SWCNT), a multi-walled carbon nanotube (MWCNT), zinc-oxide nanowires (ZnONWs), silver, aluminum, or copper.
10 . The method of claim 1 , wherein the flexible substrate comprises at least one of PDMS, silicone rubber, poly-urethane, ecoflex, Dragon-Skin, or stretchable tape.
11 . A strain sensor manufactured using the method of manufacturing the strain sensor by control of the thin-film crack using the stress concentration structure according to claim 1 .
12 . A method of manufacturing a strain sensor by control of thin-film crack using a stress concentration structure, the method comprising: preparing a solution to be used as a conductive thin-film material for the strain sensor and a flexible substrate to form the strain sensor; forming the stress concentration structure on the flexible substrate by repeatedly depositing a micro notch (MN), which is formed to have a structure having a boundary in a two-dimensional plane (xy-plane) or a three-dimensional structure having a tapered boundary in a direction (z-direction) perpendicular to the two-dimensional plane; and forming the strain sensor by depositing the conductive thin-film on the flexible substrate so as to overlap at least a portion of the micro notch (MN), wherein in the forming of the strain sensor by depositing the conductive thin-film, a change in resistance in response to stress in the conductive thin-film is controlled, and wherein in the forming of the strain sensor by depositing the conductive thin-film, a length and growth rate of the crack on the conductive thin-film is controlled by adjusting a number and length of micro notches and a thickness of the conductive thin-film.
13 . The method of claim 12 , wherein in the forming of the strain sensor by depositing the conductive thin-film, a conduction path of the conductive thin-film is controlled by controlling the length and growth rate of the crack in the conductive thin-film.

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a strain sensor by control of thin-film crack using a stress concentration structure and a strain sensor manufactured using the same, and more particularly, to manufacturing a sensitive sensor by controlling a crack in a conductive thin-film on a flexible substrate through a stress concentration structure and applying the crack control. BACKGROUND ART A flexible, stretchable pressure/strain sensor is a sensor that is capable of detecting physical deformation caused by an external force, and a resistance-based sensor has been widely developed, generally using a property of increase in resistance of a metal conductor due to external deformation. A previously invented resistance-based sensor is broadly classified as either (1) a sensor based on a deposited metal thin-film or (2) a sensor based on a conductive nanomaterial with good mechanical properties, such as a carbon nanotube, graphene, or silver nanowire, and a polymer composite. In general, in case of the former, high sensitivity is shown due to a greater change in resistance even for small deformation, but there is a disadvantage of only being able to be used in a very limited tensile environment. In case of the latter, it is possible to operate in a wide range of tensile environments due to the good mechanical properties of the material, but there is a problem of low sensitivity due to an insignificant change in resistance. DISCLOSURE Technical Problem Accordingly, the present invention is directed to solving the technical problem in this regard, and an object of the present invention is to provide a method of manufacturing a strain sensor by control of thin-film crack using a stress concentration structure. Another object of the present invention is to provide a strain sensor manufactured using a method of manufacturing a strain sensor by control of thin-film crack using the stress concentration structure. Technical Solution A method of manufacturing a strain sensor by control of thin-film crack using a stress concentration structure, according to an embodiment for achieving the object of the present invention described above, the method includes: preparing a solution to be used as a conductive thin-film material for a strain sensor and a flexible substrate to form the strain sensor; forming a stress concentration structure on the flexible substrate by repeatedly depositing a micro notch (MN), which is formed to have a structure having a boundary in a two-dimensional plane (xy plane) or a three-dimensional structure having a boundary in a direction perpendicular to the plane (z direction); and forming a strain sensor by depositing a conductive thin-film on the flexible substrate so as to overlap at least a portion of the stress concentration structure. In an embodiment of the present invention, in the forming of the stress concentration structure, the stress concentration structure may be patterned into an array structure that has a predetermined spacing in the form of a bar. In an embodiment of the present invention, in the forming of the stress concentration structure, a conduction path of current flowing through the flexible substrate may be controlled by controlling a crack that is formed on the flexible substrate through an arrangement of micro notches. In an embodiment of the present invention, in the forming of the stress concentration structure, as a spacing between the micro notches gets closer, cracks at the boundary of the stress concentration structure may merge together to determine a growth length of the crack, and the crack may block the conduction path to reduce a current flow. In an embodiment of the present invention, in the forming of the stress concentration structure, the micro notch having a sharp boundary may be formed using at least one of the processes of printing, molding, deposition, and photolithography. In an embodiment of the present invention, in the forming of the strain sensor by depositing the conductive thin-film, a change in resistance in response to stress in the conductive thin-film may be controlled. In an embodiment of the present invention, in the forming of the strain sensor by depositing the conductive thin-film, a length and growth rate of the crack on the conductive thin-film may be controlled by adjusting the number and length of micro notches and a thickness of the conductive thin-film. In an embodiment of the present invention, in the forming of the strain sensor by depositing the conductive thin-film, a conduction path of the conductive thin-film may be controlled by controlling the length and growth rate of the crack in the conductive thin-film. In an embodiment of the present invention, the method of manufacturing a strain sensor by control of thin-film crack using a stress concentration structure may further include rinsing with deionized water; and drying with a hot plate, when a single-walled carbon nanotube ink (SWCNT ink)