Mechanical Metamaterials on the Way from Laboratory Scale to Industrial Applications: Challenges for Characterization and Scalability

Fischer, Sarah C. L.; Hillen, Leonie; Eberl, C.

doi:10.3390/ma13163605

Cited by 53 publications

(38 citation statements)

References 99 publications

(225 reference statements)

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“…Hence, in combination with the PEU actuator, the switched through the state could be reached at elevated temperature. Basically, such unit cells can be employed to reversibly absorb energy [58] or to implement mechanical memory behavior in materials [3].…”

Section: Resultsmentioning

confidence: 99%

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Actuating Shape Memory Polymer for Thermoresponsive Soft Robotic Gripper and Programmable Materials

et al. 2021

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For soft robotics and programmable metamaterials, novel approaches are required enabling the design of highly integrated thermoresponsive actuating systems. In the concept presented here, the necessary functional component was obtained by polymer syntheses. First, poly(1,10-decylene adipate) diol (PDA) with a number average molecular weight Mn of 3290 g·mol−1 was synthesized from 1,10-decanediol and adipic acid. Afterward, the PDA was brought to reaction with 4,4′-diphenylmethane diisocyanate and 1,4-butanediol. The resulting polyester urethane (PEU) was processed to the filament, and samples were additively manufactured by fused-filament fabrication. After thermomechanical treatment, the PEU reliably actuated under stress-free conditions by expanding on cooling and shrinking on heating with a maximum thermoreversible strain of 16.1%. Actuation stabilized at 12.2%, as verified in a measurement comprising 100 heating-cooling cycles. By adding an actuator element to a gripper system, a hen’s egg could be picked up, safely transported and deposited. Finally, one actuator element each was built into two types of unit cells for programmable materials, thus enabling the design of temperature-dependent behavior. The approaches are expected to open up new opportunities, e.g., in the fields of soft robotics and shape morphing.

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Section: Resultsmentioning

confidence: 99%

“…Soft robotics, as well as the still novel metamaterials [1,2] or programmable materials [3], require compliant actuator materials. Shape memory polymers (SMPs) perfectly fulfill this criterion.…”

Section: Introductionmentioning

confidence: 99%

Actuating Shape Memory Polymer for Thermoresponsive Soft Robotic Gripper and Programmable Materials

et al. 2021

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“…Metamaterials have been explored with feature sizes from the nanometer range up to the millimeter range. [ 29 ] The millimeter scale range is chosen for the unit cells of the metamaterial capacitive sensor array to provide negative Poisson's ratio property to curve surfaces expanding or contracting by more than a few millimeters as shown in Figure B,C. A soft auxetic metamaterial array with sinusoidal segments consisting of electrically conductive PI–ETPU electrodes of width 0.8 mm and insulative TPU dielectric layer of thickness 0.7 mm is designed in Figure 1A and detects capacitive changes under a normal force or proximity stimuli.…”

Section: Resultsmentioning

confidence: 99%

3D Printed Metamaterial Capacitive Sensing Array for Universal Jamming Gripper and Human Joint Wearables

et al. 2021

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Existing stretchable capacitive sensor arrays face challenges in decoupling normal forces and stretch stimuli which restrict its applications into soft robotics. Herein, a metamaterial capacitive sensor array with 6 × 6 sensors is developed for the detection of normal forces on curved deforming surfaces common to both the soft universal jamming gripper and human elbow. The fabrication process involves the 3D printing of carbon black thermoplastic polyurethane (PI–ETPU) electrodes and thermoplastic polyurethane (TPU) insulation based on commercially available multimaterial fused deposition modeling (FDM). This metamaterial capacitive sensor array is unaffected by a uniaxial stretch of up to 21.6% and remains capable of detecting normal forces. The sensor array structure possesses a negative Poisson's ratio which is desirable for improving compliance and conformability to adhered expanding surfaces. Consequently, normal force‐distribution and proximity detection capabilities on curved deforming surfaces are demonstrated on a soft universal jamming gripper for measuring gripping forces and identifying object shapes. Conformal force‐sensing joint wearable on a human elbow with an individualized Poisson's ratio is explored as another application. The possibility of programming Poisson's ratio of a metamaterial capacitive sensing array opens new avenues for potential sensing applications into soft robotics and personalized wearables.

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“…Metamaterials can be seen as another class of modular assembly when made of active repeated cells. Passive auxetic structures and metamaterials have been widely studied and reviewed [191][192][193]. However, few works on active materials have been reported.…”

Section: Modularitymentioning

confidence: 99%

Programmable Stimuli-Responsive Actuators for Complex Motions in Soft Robotics: Concept, Design and Challenges

et al. 2020

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During the last years, great progress was made in material science in terms of concept, design and fabrication of new composite materials with conferred properties and desired functionalities. The scientific community paid particular interest to active soft materials, such as soft actuators, for their potential as transducers responding to various stimuli aiming to produce mechanical work. Inspired by this, materials engineers today are developing multidisciplinary approaches to produce new active matters, focusing on the kinematics allowed by the material itself more than on the possibilities offered by its design. Traditionally, more complex motions beyond pure elongation and bending are addressed by the robotics community. The present review targets encompassing and rationalizing a framework which will help a wider scientific audience to understand, sort and design future soft actuators and methods enabling complex motions. Special attention is devoted to recent progress in developing innovative stimulus-responsive materials and approaches for complex motion programming for soft robotics. In this context, a challenging overview of the new materials as well as their classification and comparison (performances and characteristics) are proposed. In addition, the great potential of soft transducers are outlined in terms of kinematic capabilities, illustrated by the related application. Guidelines are provided to design actuators and to integrate asymmetry enabling motions along any of the six basic degrees of freedom (translations and rotations), and strategies towards the programming of more complex motions are discussed. As a final note, a series of manufacturing methods are described and compared, from molding to 3D and 4D printing. The review ends with a Perspectives section, from material science and microrobotic points of view, on the soft materials’ future and close future challenges to be overcome.

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Mechanical Metamaterials on the Way from Laboratory Scale to Industrial Applications: Challenges for Characterization and Scalability

Cited by 53 publications

References 99 publications

Actuating Shape Memory Polymer for Thermoresponsive Soft Robotic Gripper and Programmable Materials

Actuating Shape Memory Polymer for Thermoresponsive Soft Robotic Gripper and Programmable Materials

3D Printed Metamaterial Capacitive Sensing Array for Universal Jamming Gripper and Human Joint Wearables

Programmable Stimuli-Responsive Actuators for Complex Motions in Soft Robotics: Concept, Design and Challenges

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