Variable Stiffness SMP Membrane Gripper for 3D Object Handling

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Solution Overview

Problem

Existing dry adhesion-based grippers face challenges in achieving high system stiffness and large contact area simultaneously, limiting their load capacity and adaptability to complex 3D objects.

Innovation Solution

A dry adhesion-based gripper utilizing an unstructured flat variable stiffness SMP membrane that can switch between a soft and stiff state in response to temperature changes, allowing for conformal contact with complex surfaces and high load capacity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If a planar rigid backing is used to support SMP adhesive, then structural stability is improved, but compliance and conformability to complex surfaces deteriorate

Engineering Contradiction:

Improvestructural stabilityVSAvoidcompliance and conformability

Core Design Contradiction:

Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

The rigid backing is segmented into multiple discrete support points (feet) rather than a continuous planar structure. This segmentation allows the membrane to conform to complex surfaces while maintaining structural stability through the distributed support points, resolving the contradiction between rigidity and conformability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A thin flexible membrane is used instead of a rigid planar backing. The membrane can deform and conform to complex 3D surfaces while the SMP material provides variable stiffness control. This flexible thin film approach maintains adaptability while the SMP's ability to switch between soft and stiff states provides structural stability when needed.

Inventive Principle:

Principle #30Flexible shells and thin films

2Force

If high system stiffness is achieved, then load capacity is improved, but contact area with complex surfaces deteriorates

Engineering Contradiction:

Improveload capacityVSAvoidcontact area

Core Design Contradiction:

ForceVSArea of stationary object

Solution Approach 1:

The system uses dynamic stiffness control through SMP material that can switch between soft and stiff states in response to thermal stimuli. When soft, the membrane maximizes contact area with complex surfaces; when stiff, the load capacity increases. This dynamic adaptation resolves the contradiction between maintaining large contact area and achieving high load capacity.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The stiffness parameter of the SMP material is changed in response to thermal conditions. The material transitions between soft and stiff states based on temperature, allowing the system to optimize both contact area (when soft) and load capacity (when stiff). This parameter change resolves the contradiction by making stiffness adaptive rather than fixed.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The gripper achieves high load capacity and adaptability to various 3D shapes, with a high adhesion switching ratio, enabling efficient pick-and-place operations without the need for continuous power to maintain attachment.

Implementation Method 1

the flexible membrane being in a first state and having a first state modulus when at a first temperature (optionally an ambient temperature) being in a second state and having a second state modulus when at an elevated temperature

Methodology Applied

Scientific EffectShape memory polymer phase transition: Shape Memory Polymer

Implementation Method 2

the conversion optionally being effected by application of heat

Methodology Applied

Scientific EffectThermal heating: Heating

Data Source

PatentUS20250144814A1Versatile adhesion-based gripping via an unstructured variable stiffness membrane

Publication Date: 2025.05.08 THE TRUSTEES OF THE UNIV OF PENNSYLVANIA

AI summary

Variable stiffness materials with a modulus that can be tuned via an external stimulus offer a unique approach to realize dynamic control of adhesion. Here, an unstructured shape memory polymer (SMP) membrane with variable stiffness is used to pick-and-place of 3D objects. The variable stiffness of the SMP allows the membrane to conform to and make good contact with objects of various shapes in its soft state and then achieve high adhesive load capacity by switching to the stiff state. Release of objects is realized by switching to the soft state. The ratio between the high-adhesion and low-adhesion state is demonstrated (in non limiting embodiments) to be >2000 on a curved substrate and ˜115 on a flat substrate. This gripper exhibits no adhesion in non-actuated state and maintains adhesion passively once actuation is complete.