On the impacting dynamics of ferrofluid droplets on porous substrates in the presence of magnetic field

This article presents experimental and theoretical studies of the impacting behavior of ferrofluid droplets on porous substrates under the influence of magnetic fields. The effects of magnetic field strength and porous substrates on the falling, impacting, and spreading of the droplets are investigated. Theoretical models are successfully derived to predict the droplet impacting velocity in the presence of the magnetic field and the maximum spreading factor of the droplets on the porous substrates without considering magnetic field effects, respectively. Moreover, a universal scaling law is constructed for the maximum spreading factor of the ferrofluid droplets on both of the porous and smooth substrates in the presence of the magnetic field. The findings of this study can provide a foundation for understanding the impacting dynamics of ferrofluid droplets on the substrates and optimizing their applications in various fields, such as three-dimensional printing and microfluidic technology.