University of Twente Student Theses


Control of Untethered Helical Robots at the Interface between Newtonian and Viscoelastic mediums

Venezian, Roberto (2021) Control of Untethered Helical Robots at the Interface between Newtonian and Viscoelastic mediums.

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Abstract:Biologically inspired microrobots are tetherless microdevices designed to perform nontrivial tasks under the influence of an external stimulus. They have been proposed to reach locations of the body inaccessible to flexible surgical instruments. Magnetically-actuated helical microrobots can propel themselves in fluids and soft tissues with a wide range of Reynolds numbers. However, the properties of physiological fluids vary in time and space and have a direct influence on the locomotion of microrobots along prescribed paths. Therefore, understanding the hydrodynamic response of microrobots to variations in rheological properties is an important factor for the translation of these devices into in vivo applications. In this thesis, a 6-degrees-of-freedom hydrodynamic model is developed based on the Resistive Force Theory to predict the response of helical robots during transitions from relatively low to relatively high viscous fluids. Sensitivity analysis is implemented using this hydrodynamic model to quantify the influence of the system parameters on the states of the helical robot. These analyses reveal how the states of the microrobots are selectively affected based on controlled changes in actuation and rheological properties of the environment. A magnetic-based robotic system is employed to experimentally study the motion of the helical robot between Newtonian and viscoelastic mediums in open-loop. Numerical results and experiments show that associated with the decrease in the actuation frequency and the increase in magnetic field strength, is a decrease in the sensitivity of the microrobot to physical surroundings.
Item Type:Essay (Master)
Faculty:ET: Engineering Technology
Subject:52 mechanical engineering
Programme:Biomedical Engineering MSc (66226)
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