# Bioinspired Kirigami Structure for Efficient Anchoring of Soft Robots via Optimization Analysis
## 2 Design, Composer, and Experimental Setup
### Composer of the Kirigami-Skinned Crawlers for Parameters Analysis  
To systematically evaluate the functional impact of kirigami structures on locomotion, a modular soft robotic crawler was composed, integrating mechanical, structural, and electronic subsystems. The crawler comprises a permanent magnet (PM) linear actuator, a kirigami-skinned silicone body, and a microcontroller-based control unit, designed to enable precise and repeatable testing under varied experimental conditions. The PM linear actuator (Model: LA-T8, GoMotorWorld, Shenzhen, China; 12 V, 60 N thrust, 15 mm/s rated speed, 30 mm strokewas selected for its compactness, silent operation, and higher precision compared to traditional pneumatic actuators [23; 27]. The actuator provides a maximum stroke length of 30 mm, sufficient for evaluating different deformation regimes and crawling behaviors (Figure 2a). It is mechanically coupled to a compliant soft body formed from Ecoflex 00-30, silicone elastomer ((Smooth-On, Inc., Macungie, PA, USA; shear modulus \(\mu_{a}\approx\) 30 kPa), cast into a 1-millimeter-thick sheet, and degassed to eliminate voids. This flexible substrate offers low stiffness and high stretchability, allowing seamless integration with kirigami layers. The kirigami skin is fabricated from PET sheets (Changzhou Huisu Qinye Plastic Group, China) with kirigami cut patterns and is firmly bonded to the silicone layer from both sides, which ensures consistent attachment and mechanical transfer (Figure 2b). Upon actuation, the sheet undergoes buckling-induced pop-up deformation, translating the actuator's linear motion into anisotropic surface contact and friction-driven propulsion. The closed configuration of the actuator maintains tension on the skin, which rebounds during retraction, facilitating the cyclic crawling motion. A microcontroller-based control circuit governs the actuation cycle of the composed crawler. The control system features an Arduino and an LN298 motor driver, powered by dual 12 V lithium batteries (Kuongshun Electronic Limited, Guangzhou, China), delivering both driving power and regulated logic voltage. The actuator's bidirectional movement is controlled via a polarity-switching algorithm, enabling fine-tuned extension and retraction sequences. A standard test consisted of five actuation cycles at 15 mm/s extension speed, unless otherwise varied, with displacement tracked across a polyurethane (PU) foam substrate that simulates compliant terrain (Figure 2c,d). To further understand frictional dynamics during locomotion, forward and backward friction forces were independently measured using a J14014 mechanical sensor (Model: Phyphox, Xiangsheng Science and Education Equipment Co., Ltd., Guang'an, China). In a separate experimental setup, the crawler was placed on PU foam while the sensor recorded resistance during controlled to-and-from motion (Figure 2e,f). This allowed for the quantification of anisotropic friction generated by various kirigami configurations, critical for optimizing propulsion mechanics. To systematically optimize the locomotion efficiency of the kirigami-based soft robotic crawler, a series of controlled experiments were conducted. Each test was designed to evaluate the influence of specific structural or actuation parameters on crawling performance. Each experiment was repeated five times to ensure repeatability, and the mean crawling distance along with standard deviation was recorded to quantify the effect of pattern geometry on traction, deformation behavior, and net displacement. The overarching objective was to understand the complex interplay between kirigami mechanics, surface interaction, and actuation dynamics. The following subsections describe each experiment and its purpose:  
1. Kirigami Structure Type vs. Crawling Distance: This experiment investigates how different kirigami geometries affect anisotropic friction and locomotion.