Opportunity
The development of adaptive structures capable of holding multiple stable configurations is crucial for industries requiring morphing capabilities, such as aerospace, automotive, and robotics. Traditional bistable or multistable structures face significant limitations, including restricted configurations, weak bending stiffness, and low load-bearing capacities. For instance, conventional bistable shells (e.g., composite shells based on thermal effects or plastically bent metallic shells) are limited to cylindrical shapes and are sensitive to environmental factors like temperature and moisture. Additionally, existing multistable shells (e.g., dimpled or microlens-based designs) are unsuitable for load-bearing applications due to their ultra-thin construction (~100 μm). These shortcomings hinder their practical deployment in high-demand scenarios like morphing aircraft wings or reconfigurable robotic components. The need for a robust, design-flexible, and high-load-capacity multistable structure motivated this invention.
Technology
The patent introduces a novel method to create multistable structures by applying localized physical or chemical treatments (e.g., Surface Mechanical Attrition Treatment, or SMAT) to induce residual stress fields in specific regions of a base material. The treated portions interact with untreated areas to form a prescribed stress distribution, enabling the structure to hold multiple stable configurations without external energy input. Key innovations include:
1. Localized Stimulations: SMAT or other treatments (e.g., laser sintering, chemical oxidation) are applied to selected regions (25–53% of the total area, optimally ~50%) to create compressive stresses. The untreated regions constrain these stresses, causing the structure to buckle into stable domelike or cylindrical shapes.
2. Design Flexibility: By varying the shape (circular, elliptic, rectangular), distribution, and number of treated zones, the structure can achieve symmetric or asymmetric configurations (e.g., 7-zone multistable shells with 128 possible states).
3. Enhanced Performance: The treated regions develop nanocrystalline surfaces and nanotwins, increasing yield strength and elastic deformation capacity. For example, a 304 stainless steel bistable disk (radius: 40 mm, thickness: 0.46 mm) withstands >300 N point loads before snapping—far exceeding traditional bistable shells (20–38 N).
4. Post-Processing Adaptability: Further mechanical processes (e.g., bending, folding) can modify configurations while retaining multistability.
Advantages
- High Load-Bearing Capacity: Structures withstand forces up to 15× higher than conventional bistable shells.
- Energy-Free Stability: Maintains configurations without external power or supports.
- Material Versatility: Applicable to metals (e.g., stainless steel) and soft materials (e.g., PDMS).
- Environmental Robustness: Insensitive to temperature/moisture, unlike thermal-based composites.
- Scalability: Suitable for macro- and micro-scale applications (e.g., valves, microlenses).
Applications
- Aerospace: Morphing wings for UAVs, adaptive mirrors in optical systems.
- Robotics: Reconfigurable grippers or joints.
- Energy Harvesting: Snap-through mechanisms for vibration energy conversion.
- Automotive: Shape-changing components for aerodynamic efficiency.
- Medical Devices: Deployable stents or surgical tools.
