Multi-axis strain sensor

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.