Leeches as a model

Schmalz found what he was looking for in leeches. With their two suction organs at the front and rear ends, they have the ability to cling to different surfaces. Whether slimy or porous, under or above water - thanks to the combination of suction adhesion and mechanical gripping or clinging, they can attach themselves securely to their hosts. Together with the University of Freiburg, Schmalz started a project to better understand the biological adhesion systems. ‘We investigated the functional morphology and biomechanics of leeches,’ explains Prof Dr Thomas Speck. He heads the ‘Botany - Functional Morphology and Bionics’ working group at the University of Freiburg.

After manual removal tests, the researchers built rotating systems and determined the centrifugal force at which the leeches detach from the respective surface. ‘We broke new ground and developed special test setups to measure the adhesive forces of the leeches,’ explains Thomas Speck. In a current research project, the team is investigating the anatomy of the sucking organ, which consists of muscle-controlled sucking, sealing and grasping lips. ‘Understanding the form-structure-function relationship of the sucking organ is essential for further abstraction and implementation steps for new, bionically optimised systems of Schmalz,’ explains Dr Simon Poppinga, who is in charge of basic biological research on the model organism at TU Darmstadt.

Harald Kuolt: ‘Our pre-development department then produced a prototype that differs from our standard range.’ Firstly, the sealing lip runs in a different direction to that of standard suction cups. Secondly, Schmalz adapted the radii of curvature and combined hard and soft materials. ‘We were able to reduce the dead volume and thus evacuate much faster,’ says the research manager happily. "Our aim is for the new suction cup to perform better than conventional models in terms of holding and shear forces as well as sealing behaviour. It should also be suitable for industrial production." And its carbon footprint must also measure up to previous suction cups.

Schmalz is currently focusing on further optimising two variants. The new models save energy thanks to their short evacuation times. They seal better on rough surfaces and impress with their long service life. Thanks to the new structure of the seal, they should also ensure a secure hold on uneven or sensitive surfaces. ‘The suction cups must function reliably in standard applications; we don't want to develop a solution for a few special cases,’ emphasises Harald Kuolt.