Origami-patterned capacitor with programmed strain sensitivity

Abstract

Origami patterns have previously been investigated for novel mechanical properties and applications to soft and deployable robotics. This work models and characterizes the mechanical and electrical properties of origami-patterned capacitive strain sensors. Miura-patterned capacitors with different fold angles are fabricated with a silicone body and foil electrodes. The planar strain sensitivity ratio is tunable from 0.2 to 0.5 with fold angles, while all-soft patterns demonstrate low mechanical tunability through fold angle. We conclude by offering recommendations for designing and modeling future origami-patterned soft material sensors.

Controlling the fold: proprioceptive feedback in a soft origami robot

“… Shih et al (2020) offer a comprehensive review of the state of soft robotic shape estimation, perception, and efforts towards closed loop control. Here, we highlight recent efforts in soft material sensors for actuator shape or force estimation using flexible circuit components such as capacitors ( Kim et al, 2021 ; Dorsey et al, 2022 ), resistors ( Sun et al, 2022b ; Dong et al, 2022 ; Thuruthel et al, 2019 ), or inductors ( Huang et al, 2022 ; Wang et al, 2022 ) fixed to the robot body. Detecting the angle between two actuator faces has also been well reported ( Mori and Onoe, 2021 ; Wang et al, 2022 ), with angle accuracies ranging from 12° ( Mori and Onoe, 2021 ) for a piezoresistive sensor to ±1° for an inductive sensor ( Wang et al, 2022 ).…”

“…Additionally, range sensing on deformable objects is subject to interference and misalignments between sensors as the actuators deform. Soft mechanical sensors can both be integrated directly into the robot body and provide accurate force and shape estimations ( Kim et al, 2021 ; Dorsey et al, 2022 ; Sun et al, 2022b ; Dong et al, 2022 ; Thuruthel et al, 2019 ; Huang et al, 2022 ; Wang et al, 2022 ). Improving mechanical sensor performance to achieve closed-loop control will be critical to meet future soft robotics sensing and control needs.…”

High-stretchability and low-hysteresis strain sensors using origami-inspired 3D mesostructures

“…As an alternative approach, structure designs capable of mechanical stretching can provide means of achieving stretchable strain sensing without relying on stretchable conductive materials. These designs include wavy structures, fractal designs, twisted or helical structures, open-mesh structures, and origami-and kirigami-inspired structures (15)(16)(17)(18)(19)(20)(21)(22)(23). For example, parallel-plate capacitive strain sensors using wrinkled ultrathin gold film electrodes exhibit high sensitivity and linearity with small hysteresis, but with limited stretchability (140%) (18).…”

“…Auxetic structures with engineered cuts can provide stretchability for parallel-plate capacitive sensors but with limited stretchability (50%) ( 20 ). Miura-patterned, foil-based sensors are capable of measuring capacitance changes during folding and unfolding with a low strain range (20%) ( 21 ). Stretchable strain sensors with large strain range, low hysteresis, and fast response are highly desirable, especially for accurate measurement of large and dynamic deformations.…”