A single-probe capillary microgripper induced by dropwise condensation and inertial release

Abstract

A micromanipulation method based on liquid droplets is widely used as a non-destructive technology to pick-and-place micrometer-scale objects. We focus on the development of a single-probe capillary microgripper to execute reliable micromanipulation tasks. By controlling dropwise condensation on a probe tip, the water droplet volume on the hydrophobic tip surface can be varied dynamically, which helps establish appropriate capillary lifting forces during capturing tasks. An inertia-releasing strategy was utilized to implement a piezoelectric actuator integrated with the capillary microgripper and to address release problems caused by adhesion force action. The influence of droplet formation and the capillary lifting force generated during the manipulation process were characterized experimentally. Micromanipulation tests were conducted using a customized motion platform with viewing microscopes to verify the performance potential of the capillary microgripping tool. Experimental results indicated that polystyrene microspheres with 20–100 μm radii and micro-silicon chips (1.63–12.1 μN) were grasped reliably, and that adhered micro-objects could be placed on a target using the proposed microhandling technique of inertial release in ambient conditions.

Capillary Forces between Concave Gripper and Spherical Particle for Micro-Objects Gripping

“…The shape of the liquid droplet was changed by adjusting the relative position of each needle, resulting in the micro-components tilting and their rotation. Fan et al [ 8 , 9 ] proposed a capillary gripping method based on dropwise condensation to guarantee real-time droplet formation. Microspheres with 40–200 μm diameter were grasped reliably using a single-probe capillary microgripper with hydrophobicity.…”

A release method of micro-objects based on the liquid bridge configuration

“…Vasudev et al [8] changed the wetting property of the solidliquid interface by electrowetting to achieve the release of microspheres with diameters of 250-500 µm. Fan et al [9] controlled the liquid bridge volume by adjusting the temperature of liquid solidification to change the wetting contact area and release microspheres. Walle et al [10] realized the release of a 600 × 600 × 100 µm 3 silicon object with a submerged freezing gripper by changing the liquid medium phase.…”

Pick and release of micro-objects: An actuation-free method to change the conformity of a capillary contact

“…The additional force can also be developed by inertia, e.g. in [10] where a large vertical deceleration is applied to the gripper, or in [11] and [12] where vibrations are used. The rupture of the meniscus has also been achieved by generating a higher attraction force on the substrate where the release is expected, e.g.…”