Multi-axis strain sensor
Provided is a strain sensor. The strain sensor according to embodiments of the inventive concept includes a flexible substrate, rigid patterns on the flexible substrate, the rigid patterns including a first pattern and a second pattern spaced apart from the first pattern in a first direction, a first electrode on the first pattern, a second electrode on the second pattern, the second electrode being spaced apart from the first electrode, and a piezoresistive layer connecting the first electrode and the second electrode. Here, each of the rigid patterns may have a stiffness greater than that of the flexible substrate.
1. A strain sensor comprising:
a flexible substrate;
an upper capping layer on the flexible substrate;
rigid patterns on the flexible substrate, the rigid patterns comprising a first pattern and a second pattern spaced apart from the first pattern in a first direction;
a first electrode on the first pattern;
a second electrode on the second pattern, the second electrode being spaced apart from the first electrode; and
a piezoresistive layer connecting the first electrode and the second electrode, wherein
each of the rigid patterns has a stiffness greater than that of the flexible substrate,
the first pattern has a first thickness in a second direction perpendicular to the first direction,
the piezoresistive layer has a second thickness in the second direction,
the first thickness is greater than the second thickness,
the rigid patterns have side surfs that face each other,
the piezoresistive layer vertically overlaps the side surfaces of rigid patterns that face each other,
the upper capping layer contacts with a side the piezoresistive layer, side surfaces of the first and second electrodes, and at least part of upper surfaces of the first and second electrodes, and
a width of the first pattern in the first direction is the same as a width of the first electrode in the first direction.
2. The strain sensor of claim 1 , wherein each of the rigid patterns has a stiffness greater than that of the piezoresistive layer.
3. The strain sensor of claim 1 , wherein a distance between the first pattern and the second pattern is greater than a thickness of the first pattern.
4. The strain sensor of claim 1 , wherein the first pattern has a first side surface that faces the second pattern, and
the second pattern has a second side surface that faces the first side surface and is parallel to the first side surface.
5. The strain sensor of claim 1 , wherein the first pattern has a first side surface that faces the second pattern, and the second pattern has a second side surface that faces the first side surface, and
a distance between the first side surface and the second side surface is constant along a second direction perpendicular to the first direction.
6. The strain sensor of claim 5 , wherein each of the rigid patterns has a stiffness greater than that of an upper capping layer.
7. The strain sensor of claim 1 , further comprising a first pad electrically connected to the first electrode and a second pad electrically connected to the second electrode, which are disposed on the flexible substrate.
8. The strain sensor of claim 1 , further comprising a wire connected to the first electrode,
wherein the wire has a serpentine-pattern shape.