Closed-Loop Control of a Magnetic Particle at the Air–Liquid Interface

One of the greatest challenges in microrobotics is the development of robotic devices for high-speed transportation and precise positioning of microcomponents. This paper proposes to use non contact magnetic actuation in which objects are placed at the air/liquid interface and are actuated through magnetic field gradients. A physical model is developed and identified to perform closed-loop control. This approach is validated through several experiments in 1-D. Precise positioning and high-speed trajectory tracking of objects smaller than 100<formula formulatype="inline"><tex Notation="TeX">$\ \mu\hbox{m}$</tex></formula> are achieved. The position error of an object of 60 <formula formulatype="inline"><tex Notation="TeX">$\times \hbox{ 50 }\times \hbox{ 25}\ \mu\hbox{m}^{3}$</tex></formula> is less than 10% of its size and the maximum velocity reached is about <formula formulatype="inline"><tex Notation="TeX">$\hbox{ 6 mm/}$</tex></formula>. The closed-loop control has been tested on objects as small as 30 <formula formulatype="inline"><tex Notation="TeX">$\times \hbox{ 20 }\times\hbox{ 25}\ \mu\hbox{m}^{3}$</tex></formula> and demonstrates its ability to perform precise positioning (the position error is less than 7% of the size of the object). This approach represents a promising solution to design devices for high throughput transportation and precise positioning of micro-objects, which will lead to magnetic smart surfaces at micrometer scale.