Biological and artificial microswimmers often encounter fluid media with non-Newtonian rheological properties. In particular, many biological fluids such as blood and mucus are shear-thinning. Recent studies have demonstrated how shear-thinning rheology can impact substantially the propulsion performance in different manners. In this work, we examine the effect of geometrical shape upon locomotion in a shear-thinning fluid using a prolate spheroidal squirmer model. We use a combination of asymptotic analysis and numerical simulations to quantify how particle geometry impacts the speed and the energetic cost of swimming. The results demonstrate the advantages of spheroidal over spherical swimmers in terms of both swimming speed and energetic efficiency when squirming through a shear-thinning fluid. More generally, the findings suggest the possibility of tuning the swimmer geometry to better exploit non-Newtonian rheological behaviours for more effective locomotion in complex fluids.

A modeling approach is developed to better describe the relation between input electrical power and the physical reaction of the bonding system during ultrasonic bonding. The major distinction between this analysis and previously published works is to attempt to eliminate empirically driven correlations between the input power and the kinetics of the bonding process. Two models, a piezoelectric model and an ultrasonic bonding model, are combined in order to reach this goal. The piezoelectric model is used to calculate the desired forcing, amplitude, and frequency that is created by the piezoelectric transducer during the actual ultrasonic bonding process. For this process, a lumped parameter model, taken from literature, is used, that converts input current and voltage to velocity and position of the bonding tooltip, respectively. This model is then combined with an updated model of the relative amplitude between the bonding material and substrate as the ultrasonic bond is being formed. Our model differs from existing friction power models by utilizing the Archard Equation to account for the removal of the natural oxide film. The integrated model provides a relationship between the bond growth and the driving power. The analysis enables comparison between the transverse force on the bond tool and amplitude of the bond tool’s motion for different electrical input powers.