By integrating piezoelectric actuation directly with structural elements in a unified laminated composite, this new approach eliminates the need for traditional assembly while delivering high-speed, multi-environment mobility.
A recent study published in Microsystems & Nanoengineering (Nature Portfolio) introduces a 1.2 g parallel-legged insect-scale origami robot, known as PLioBot.
Fabricated through an integrated lamination process, the robot achieves forward, backward, and turning motions at speeds up to 44.6 cm/second. It can navigate confined spaces, climb 12° slopes, traverse complex terrains such as grass and sand, and even operate in water (either submerged or on the surface).
Background
Insect-scale micro-crawling robots that work on the centimeter scale tend to be well-suited for confined or hard-to-reach environments, including caves, disaster zones, and extraterrestrial terrains. These robots often rely on piezoelectric actuators due to their precision, responsiveness, and compact form factor.
Previous developments, such as the smart composite microstructure (SCM) process and Harvard ambulatory micro robots (HAMRs), have advanced both design and fabrication. However, these systems still depend on separately manufactured components followed by manual assembly. This not only increases fabrication complexity but can also introduce alignment errors and limit scalability.
To overcome these limitations, the researchers developed PLioBot, which integrates actuators and structural components into a single origami-inspired composite using an improved lamination process. The result is a streamlined, assembly-free fabrication method that enhances both performance and manufacturing efficiency.
Modeling and Optimization
The study presents a detailed modeling and optimization framework for PLioBot’s parallel-legged mechanism. The kinematic analysis is divided into three modules:
- Modules 1 and 2 establish the relationship between actuator displacement and driving angles.
- Module 3 maps these driving angles to the foot trajectory.
Together, these modules provide a complete kinematic pathway from actuator input to foot movement.
The piezoelectric actuator is modeled as a three-layer cantilever beam composed of piezoelectric ceramic–carbon fiber–piezoelectric ceramic. Under ideal conditions, displacement is shown to scale with driving voltage amplitude, which is typically limited to around 150–200 V to avoid actuator failure.
To maximize locomotion efficiency, the researchers applied a genetic algorithm (GA) to optimize stride length under consistent driving signals. With constraints on size and weight, the optimized design achieved a modeled maximum step length of 4.4 cm, supporting efficient movement within the tight limits of an insect-scale system.
Materials, Fabrication, and Performance Characterization
PLioBot’s integrated origami mechanism combines multiple materials, each serving a specific function:
- Glass fiber provides structural rigidity
- Carbon fiber prepreg acts as both adhesive and electrode
- Polyimide film forms flexible hinges
- Piezoelectric ceramics enable actuation
All components are embedded within a single five-layer laminated composite, eliminating the need for manual assembly.
Performance testing shows that locomotion depends on driving frequency, phase difference, and voltage amplitude. The robot reaches a peak speed of 44.6 cm/second (17.84 body lengths per second) at 60 Hz with a 100° phase difference. It can also carry payloads up to 1.4 g while maintaining mobility.
Environmental adaptability tests demonstrate movement across a wide range of surfaces, including glass, acrylic, and sponge, along with the ability to climb slopes up to 12°. The robot navigates confined tunnels and L-shaped paths while carrying a load. Interchangeable foot mats extend its versatility: spherical designs improve traction on uneven terrain, while fin-shaped attachments enable swimming.
Notably, the robot can move along submerged surfaces at depths up to 7 cm and also travel across the water surface. Its performance is influenced by resonance effects, with peak efficiency around 60 Hz. At higher speeds, stability challenges arise due to increased impact forces and trajectory deviations.
Compared to existing piezoelectric micro-robots, PLioBot achieves a strong balance between speed, payload capacity, and environmental adaptability.
Origami-Based Structural Realization
PLioBot measures just 2.5 cm in each dimension and is built around an origami-inspired design. The structure integrates four combined piezoelectric actuators and four parallel-legged mechanisms into a single folded form.
Each actuator consists of two independently controlled piezoelectric elements, allowing precise conversion of electrical signals into mechanical motion. The parallel-legged configuration uses two actuators per leg, providing two degrees of freedom for both vertical and horizontal movement.
Locomotion is achieved using a trot gait, where diagonal leg pairs move together to maintain stability and forward motion.
The robot begins as a flat, two-dimensional laminated composite that includes all structural and actuation components. Through a six-step folding process along flexible hinges, it transitions into its final three-dimensional form without the need for any additional assembly. As folding progresses, the number of active links and joints is reduced, resulting in a mechanism with eight degrees of freedom.
The hinge design is carefully balanced to allow sufficient flexibility for motion while maintaining structural integrity and preventing failure.
Conclusion
This study introduces PLioBot, a 1.2 g insect-scale robot that integrates actuation and structure into a single laminated origami mechanism. By eliminating the need for assembly, the design simplifies fabrication while improving precision and performance.
The robot demonstrates high-speed locomotion, multi-terrain adaptability, and amphibious capability, all within a compact footprint.
While the current design relies on external power, future work will focus on integrating onboard electronics to enable fully untethered operation.
Journal Reference
Zhu, Q., Jiang, T., Luo, Z., Zhu, Y., & Huang, G. (2026). A parallel-legged insect-scale robot based on actuation-structure integrated origami mechanism. Microsystems & Nanoengineering, 12(1). DOI:10.1038/s41378-026-01205-4. https://www.nature.com/articles/s41378-026-01205-4
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