Manipulation of swarm ferrofluid droplets on liquid surface

Abstract

• The high-resolution manipulation based on the fixed module on the liquid surface . Limited the high remanence and the size of the permanent magnet, the high resolution manipulation ferrofluid droplets is difficult to achieve. In this paper, we utilized the simple method to obtain the micro magnetic field to obtain the delicacy control for the microscale ferrofluid. Furthermore, we utilize the fixed module to build the high resolution magnetic field to achieve the letter writing in a small region on the liquid surface. • The low resolution flexible magnetic control based on the digital magnetic control platform. Based on your comments, we design a digital magnetic field-controlled platform to achieve the ability of the digital encode. In this platform, we design two kinds of experiment. The first kind of experiments is the static number/geometry shapes display. Through on and off of the electromagnet in different positions, we obtain the different number or geometry shapes on the liquid surface. The second kind of experiment are the dynamic motion trajectory experiments. We use the digital controlled platform to dynamical letter writing different trajectory/characters. • Sum up, the highlights of the paper are the high-resolution manipulation ferrofluid based on the fixed module and flexible magnetic control based on the digital magnetic control platform. Manipulation of small liquid droplets is critical for many types of research and applications in the field of chemistry, biology, etc. Many methods based on different working principles were proposed to manipulate liquid droplets. Among them, magnetic manipulation is widely used because of its safety and contactless feature. However, current control strategies mainly focus on hydrophobic or superhydrophobic solid surfaces requiring costly special treatments and being vulnerable to external pollution, which is an obstacle for surface reusing. Besides, the existing technologies are difficult to balance size and quantity of liquid droplets. Here, we propose high precision, resolution and the manipulation control methods for achieving manipulation of both single and swarm ferrofluid droplets. Utilizing the proposed methods, we can achieve the letter writing on the liquid surface. The proposed method offers an efficient strategy for manipulation of ferrofluid droplets.