Biomechanics of adhesion in wet and structured environments

A daunting challenge for technology is gripping in complex environments, such as the inside of the human body or crop fields in agriculture. These environments consist of soft tissues, thin membranes, brittle bones, textured surfaces, and non-Newtonian fluids, whose physical properties differ significantly from the materials traditionally encountered in engineering applications. However, through millions of years of evolution and adaptation, biological organisms have developed a variety of grippers that successfully interface with such complex materials. In this research, we aim to uncover the physical working principles underlying biological gripping, with a particular focus on ‘smooth’ and non-fibrous grippers.

PI: Johan van Leeuwen

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‘Smooth’ adhesive surfaces are present on the appendages of various organisms, including stick insects, cuttlefish, and tree frogs. Remarkably, while these organisms are evolutionarily and ecologically diverse, they possess similar structures on their grippers that are covered in oily fluids. Microscopic hexagonal papillae are present on the surfaces used to create intimate contact and generate gripping forces. Does this structure facilitate intimate contact in fluid-filled environments? Are there any morphological similarities across species? Additionally, the role of oily fluids in gripping is still poorly understood. Do organisms exploit these fluids to generate capillary forces? Do the fluids help grip surfaces contaminated with dust or other fine particles?

In order to gain insights, we make use of quantitative methods, specifically to characterize morphology, mechanical properties, and appendage kinematics. Through these methods, we hope to understand how organisms achieve reversible gripping and if their solutions converged independently. Finally, could we learn from biology to develop smarter gripping technologies for medical devices and agricultural robotics?

Collaborations for this research will be pursued with Dr. Julian Langowski (EZO WUR), Dr. Joshua Dijksman (PCC WUR), Prof. Marleen Kamperman (RUG), ), Dr. Aimee Sakes (TUD), Prof. Stanislav Gorb (Kiel University, Germany), Prof. Metin Sitti (Max Planck Institute for Intelligent Systems, Germany), and Prof. David Hu (Georgia Institute of Technology, USA). Additionally, this research is part of the 4TU Federation’s consortium on Soft Robotics, which provides access to experts in robotics and manufacturing.