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Project Goal:
Project Goal:
Design, fabricate, and experimentally evaluate a soft pneumatic robotic gripper for compliant grasping of delicate and irregular objects. The project focused on understanding how geometric scaling and actuation pressure influence grasping performance, repeatability, and robustness.
My role:
My role:
Fabrication and Assembly Lead
Led end-to-end fabrication of the soft gripper, including CAD for mold design (with partner), silicone casting, curing, and assembly.
Defined experimental protocols for pressure and finger-length scaling studies.
Supported testing, data collection, and iteration based on performance outcomes.
Technical Skills: Non-technical Skills:
Technical Skills: Non-technical Skills:
Soft Robotics Design Experimental Planning
Pneumatic Actuation Systems Tradeoff Analysis
Silicone Casting & Mold Design Workflow Management
Rapid Prototyping (3D Printing) Partner Collaboration
Performance Evaluation Presentation & PublicSpeakin
Results & Insights:
Results & Insights:
Improved grasp success to ~70% at medium–high pressures by optimizing pneumatic actuation levels
Increased surface conformity and object adaptability through longer finger geometries, with higher pressure requirements for stability
Identified optimal pressure ranges that balanced compliance and control, reducing slippage during grasping
Demonstrated high tolerance to object shape variation and positioning error inherent to the soft architecture
These outcomes were achieved through iterative design–test–refine cycles across finger geometry and pressure conditions.
Specifications
Specifications
Actuation: Pneumatic
Finger Material: Dragon Skin 30 silicone elastomer
Mold Design: Custom CAD-designed, modular 3D-printed molds (Onshape)
Geometry Scaling: 100%, 150%, 200%, 250% finger length variants
Project Overview:
Project Overview:
The gripper consists of two pneumatically actuated silicone fingers mounted to a rigid top plate with integrated air tubing. Each finger features internal chamber geometry optimized for bending under pressure, enabling adaptive, low-force grasping suitable for fragile objects.
Mechanical Design:
Mechanical Design:
Soft Fingers
Soft Fingers
Elastomeric fingers cast from silicone using custom CAD-designed modular molds created in Onshape
Internal chamber geometry designed to induce controlled bending under pneumatic actuation
Mold geometry scaled (100%, 150%, 200%, 250%) to evaluate the effect of finger length on deformation behavior and gripping performance
Rigid Interface
Rigid Interface
Custom brackets designed to mount and align the silicone fingers during assembly
Integrated pneumatic connections using 4 mm soft PVC tubing and one-touch fittings
Modular interface enabling repeatable assembly and future end-effector integration
Manufacturing & Assembly:
Manufacturing & Assembly:
The soft pneumatic gripper was fabricated using FDM 3D-printed molds and silicone casting to enable rapid iteration of geometry and fit. Dragon Skin 30 silicone (1:1 Part A/B) was cast in-house to form compliant fingers.
After filling, molds were wrapped in plastic film and secured with rubber bands to maintain alignment and prevent leakage, then cured at room temperature for 16 hours. Hollow finger sections were bonded using the mold geometry for alignment and cured under compression for ~5 hours. Final assembly integrated rigid mounting hardware and pneumatic tubing, followed by leak checks and fit validation.
Processes included:
Processes included:
CAD-driven mold design and iterative FDM 3D printing
Silicone mixing, casting, room-temperature curing, and post-processing
Mold alignment using plastic wrap and elastic constraint during cure
Bonding and assembly of hollow silicone structures
Integration of pneumatic tubing and rigid mounting interfaces
Leak inspection and validation through repeated assembly cycles
All the materials used to produce the fingers.
The bottom 3D-printed molds were placed over the finger halves to ensure proper bonding during curing.
Plastic wrap and rubber bands were used to maintain alignment and ensure consistent curing.
Selected and installed the successfully cured soft fingers onto the rigid interface
Testing:
Testing:
Performance was evaluated using systematic pass/fail testing across multiple configurations to assess grasp reliability, compliance, and repeatability.
Key testing steps included:
Key testing steps included:
Object-based pass/fail tests: Assessed the ability to lift common objects (e.g., PVC components, 3D-printed parts, small wheels, threaded elements) without slippage
Pressure variation: Evaluated bending response and grasp reliability under standardized low, medium, and high pressure levels
Finger length scaling: Compared grasp stability and curvature across different finger geometries
Repeatability: Examined deformation consistency and object retention over repeated actuation cycles
Metrics were primarily qualitative due to the absence of force sensors and included grasp success rate, deformation consistency, and object conformity.
The test objects used to evaluate the soft gripper.
IMG_9235.movOne of the test runs at high pressure.
Future Plan:
Future Plan:
Future efforts will integrate closed-loop pressure or curvature sensing, explore alternative silicone formulations for improved durability, and expand the design to multi-finger and task-specific geometries. The gripper will also be mounted on a robotic arm for task-level performance evaluation.
A more detailed account of this project can be found here:
Evaluating_the_Replicability_of_Soft_Robotic_Gripper_with_Tunable_Finger_Lengths.docx.pdfPage updated
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