Poroelastic Foams for Simple Fabrication of Complex Soft Robots

Murray, Benjamin C. Mac; An, Xintong; Robinson, Sanlin S.; Meerbeek, Ilse M. Van; O’Brien, Kevin W.; Zhao, Huichan; Shepherd, Robert F.

doi:10.1002/adma.201503464

Cited by 114 publications

(98 citation statements)

References 35 publications

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“…Potential methods for tuning include heating (38), electrostatic charging (39), or other forms of active stimulation. Among these methods, pressurecontrolled adhesion tuning is attractive because it can be easily combined with other pneumatic elements, which already exist for actuating a soft robotic system (40). Our analysis in Fig.…”

Section: Resultsmentioning

confidence: 94%

Controllable load sharing for soft adhesive interfaces on three-dimensional surfaces

Song

Drotlef

Majidi

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

181

165

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For adhering to three-dimensional (3D) surfaces or objects, current adhesion systems are limited by a fundamental trade-off between 3D surface conformability and high adhesion strength. This limitation arises from the need for a soft, mechanically compliant interface, which enables conformability to nonflat and irregularly shaped surfaces but significantly reduces the interfacial fracture strength. In this work, we overcome this trade-off with an adhesion-based soft-gripping system that exhibits enhanced fracture strength without sacrificing conformability to nonplanar 3D surfaces. Composed of a gecko-inspired elastomeric microfibrillar adhesive membrane supported by a pressure-controlled deformable gripper body, the proposed soft-gripping system controls the bonding strength by changing its internal pressure and exploiting the mechanics of interfacial equal load sharing. The soft adhesion system can use up to ∼26% of the maximum adhesion of the fibrillar membrane, which is 14× higher than the adhering membrane without load sharing. Our proposed load-sharing method suggests a paradigm for soft adhesion-based gripping and transfer-printing systems that achieves area scaling similar to that of a natural gecko footpad.soft gripper | equal load sharing | fracture mechanics | fibrillar adhesives | gecko B y exploiting principles of equal load sharing (1) and interfacial crack pinning (2), geckos' fibrillar foot-hairs can firmly adhere to a wide range of surfaces using intermolecular interactions, such as van der Waals forces (3). Using the same attachment method, gecko-inspired synthetic elastomeric fibrillar adhesives achieve bond strengths of over 100 kPa on smooth flat surfaces (4), surpassing the performance of the gecko on such surfaces (5), and exhibit quick release through peeling (6) or buckling (7) of the microfibers. For the past decade, gecko-inspired adhesives have been applied to a variety of systems including numerous robotic applications for wall climbing (8, 9), perching devices for flyers (10), and grippers (11)(12)(13)(14). However, difficulties arise in dealing with 3D surfaces because the current gecko-inspired synthetic adhesive systems are often supported by a rigid backing, which limits their ability to conform to nonplanar surfaces. In our previous work, we created elastomeric fibrillar adhesives integrated with a soft membrane, which we named as fibrillar adhesives on a membrane (FAM), and fixed the membrane onto a 3D-printed rigid plastic body so that the system could handle various 3D objects (15). Despite demonstrating a significant improvement over an unstructured elastomeric membrane with 10× higher adhesion, the tested FAM could achieve only 2 kPa of adhesion stress, a small fraction of the 55 kPa measured with rigid-backed microfiber arrays (16). This implies that the improved conformability to 3D surfaces enabled by the more compliant membrane backing is at the expense of a 96% reduction in adhesion strength. Considering that the adhesion of a membrane scales with the circumferential ...

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Section: Resultsmentioning

confidence: 94%

Controllable load sharing for soft adhesive interfaces on three-dimensional surfaces

Song

Drotlef

Majidi

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

181

165

View full text Add to dashboard Cite

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“…The difference between input and output pressures (DP) displayed in two pressure gauges (McMaster Carr, 3847K71) along the lumens was measured, while the flow rate (Q) was gradually increased at an interval of 25.2 mL min À1 (measured using an Omega, FLDA3422G; with measurement range of 0 to 325 mL min À1 ). [43] The neat and selectively mineralized hydrogel lumen was notated as NHL and MHL in the pressure curves, respectively.…”

Section: Liquid Flow Testmentioning

confidence: 99%

Selective Mineralization of Tough Hydrogel Lumens for Simulating Arterial Plaque

et al. 2016

Self Cite

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This paper demonstrates progress of fabricating artificial arteries (phantoms) that mimic plaque buildup. Hydrogel lumens are molded using tough polyacrylamide with regions selectively mineralized with calcium phosphate. By tuning the degree of mineralization such as calcium concentration ([Ca 2þ ], 0.4-2 M), and crystallization time (t c , 1-4 weeks), the authors control the extent of lumen occlusion. These occluded lumens significantly reduce pressure (DP % 7.79 kPa) during fluid flow compared to the non-calcified lumens (DP % 1.24 kPa). Additionally, image, chemical analysis, and compressive mechanical tests are performed to determine the effect of synthesis conditions on the composite's mechanical properties. For comparison to real arteries, the authors also present dynamic mechanical analysis of human aortic tissue.

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“…Previous reports of 3D printed silicones have thus far employed PDMS materials . However, PDMS‐based materials exhibit relatively poor temperature stability beyond −50 °C due to a crystallization transition occurring at −75 °C and a melt peak occurring around −50 °C, as measured via differential scanning calorimetry .…”

mentioning

confidence: 99%

Custom 3D Printable Silicones with Tunable Stiffness

Durban

Lenhardt

et al. 2017

Macromol. Rapid Commun.

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Silicone elastomers have broad versatility within a variety of potential advanced materials applications, such as soft robotics, biomedical devices, and metamaterials. A series of custom 3D printable silicone inks with tunable stiffness is developed, formulated, and characterized. The silicone inks exhibit excellent rheological behavior for 3D printing, as observed from the printing of porous structures with controlled architectures. Herein, the capability to tune the stiffness of printable silicone materials via careful control over the chemistry, network formation, and crosslink density of the ink formulations in order to overcome the challenging interplay between ink development, post-processing, material properties, and performance is demonstrated.

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Poroelastic Foams for Simple Fabrication of Complex Soft Robots

Cited by 114 publications

References 35 publications

Controllable load sharing for soft adhesive interfaces on three-dimensional surfaces

Controllable load sharing for soft adhesive interfaces on three-dimensional surfaces

Selective Mineralization of Tough Hydrogel Lumens for Simulating Arterial Plaque

Custom 3D Printable Silicones with Tunable Stiffness

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