Selecting silicone raw materials for robotics requires comprehensive consideration of four key dimensions: application scenario, material properties, process compatibility, cost, and sustainability. The specific selection strategy and analysis are as follows:
1. Determine Core Requirements Based on the Application Scenario
Tactile Sensor Integration
Requirement: Embedding a conductive material (such as silver paste or carbon nanotubes) or a microneedle array structure is required to achieve tactile feedback.
Example: A silicone-based soft sensor developed by a UBC team uses a weak electric field to sense force, enabling precise grasping of eggs. This requires a silicone material with excellent conductivity and flexibility (such as a graphene/silicone composite with an elongation greater than 500%).
Adaptability to Extreme Environments
Requirement: High temperature resistance (-50°C to 250°C) and chemical resistance (such as in oily environments).
Solution: Applying a hydrophobic nanocoating (contact angle greater than 150°) extends the sensor's lifespan to 100,000 cycles; selecting a high-temperature-resistant silicone (such as LSR liquid silicone rubber, which can withstand temperatures exceeding 200°C). Medical Robotics
Requirements: Biocompatibility (ISO 10993 certified), biodegradability (such as chitosan-based electronic skin).
Example: The DIGIT sensor reduces costs to one-fifth of traditional solutions through optimized silicone formulation (hardness 25 Shore A) and automated manufacturing processes, while also meeting medical-grade safety standards.
II. Matching Performance Requirements Based on Material Properties
Hardness and Elasticity
Robot joints require a medium hardness (20-30 Shore A) to balance flexibility and support, preventing excessive deformation that affects motion accuracy.
Bionic skin: An ultra-soft hardness (0-18 Shore A) is required to simulate the touch of human tissue. For example, the biomimetic tactile sensor developed by Pan Lijia's team at Nanjing University uses a multi-layer silicone structure to simultaneously detect normal force (0.1-10N) and shear force (±50°).
Tensile Strength and Tear Strength
For long-term mechanical motion scenarios: Tensile strength ≥ 5MPa and tear strength ≥ 14kN/m to withstand repeated bending and stretching. For static display scenarios, the strength requirement can be appropriately lowered, prioritizing lower-cost precipitated silicone (which offers a high cost-effectiveness but slightly lower transparency than fumed silicone).
Conductivity and Signal Stability
Triboelectric Sensors: Highly conductive silicone (such as those incorporating carbon nanotubes) should be selected, combined with a dynamic magnetic field compensation algorithm to address signal drift.
Visual Tactile Sensors: Highly transparent silicone (such as silicone reinforced with fumed silica, which offers higher transparency) should be selected, along with a multi-directional micro-camera to capture deformation.
III. Process Compatibility: Ensuring Production Feasibility
Molding Process
Injection Molding: Suitable for large-scale production, low-viscosity LSR liquid silicone rubber should be selected, which can be automatically and continuously fed to the injection molding machine.
3D Printing: Suitable for customized complex structures (such as bionic bone designs), printable silicone materials should be selected (for example, 3D printing technology based on digital twins can reduce customization cycles from 2 weeks to 48 hours).
Mold Quality: Silicone products are typically molded, and mold accuracy directly affects yield. High-precision molds (such as CNC-machined molds) should be selected to avoid burrs and deformation. Vulcanization Process
High-temperature vulcanization: Suitable for thick-walled products (such as robot housings), requiring strict control of temperature (150-200°C) and curing time (10-30 minutes).
Room-temperature vulcanization: Suitable for thin-walled products (such as sensor skins), requiring the addition of a catalyst (such as a platinum catalyst) to accelerate curing.
IV. Cost and Sustainability: Balancing Performance and Affordability
Cost Structure
Silicone for robotics: Unit price is approximately 80-120 yuan/kg, with higher costs after integrating sensors. Large-scale production (such as 3D printing technology based on digital twins) can reduce costs by 60%.
Medical-grade silicone: Expensive (approximately 150-300 yuan/kg), but standardized production (such as the DIGIT sensor automation process) can lower prices.
Sustainability
Environmentally friendly materials: Choose biodegradable silicone (such as chitosan-based electronic skin) to reduce environmental pollution.
Energy-saving processes: Use low-temperature vulcanization technology (such as room-temperature vulcanization) to reduce energy consumption. V. Recommended Selection Process
Requirements Analysis: Identify the robot's application scenarios (e.g., industrial, medical, service), functional requirements (e.g., tactile feedback, environmental adaptability), and safety standards (e.g., ISO 10993, FDA).
Material Screening: Select the silicone type (e.g., LSR, compounded rubber), hardness (0-50 Shore A), and conductivity (whether conductive material embedding is required) based on the requirements.
Process Validation: Produce samples to test performance (e.g., tensile strength, tear strength, signal stability), and assess production costs and feasibility.
Mass Production: Strictly control raw material ratios, vulcanization temperature, and mold precision to ensure product consistency.