Nanocomposite surfaces with electrically switchable adhesion

#In many manufacturing processes, pick-and-place operations are often used in handling parts, components, and products. The most common approach for pick-and-place operations is to use mechanical grippers having multi-fingered robotic hands and vacuum-based systems, also referred to as the grasping approach. However, it is usually challenging to use the same gripper to handle objects having different sizes, shapes, orientations, and brittleness. In addition, mechanical grippers typically involve high precision control of the robotic hand, especially in electronics manufacturing where the products are fabricated and assembled in microscales and nanoscales.

#Another approach for pick-and-place operations uses devices with tunable surface adhesion. This approach is attractive for pick-and-place operation in small scale because it can achieve high precision with less complicated control compared to the grippers. Viscoelasticity is usually used to achieve tunable surface adhesion. In this technique, the adhesion of elastomers can be tuned by controlling the contact/detach speed between the device and the target object. Elastomers can also have good mechanical compliance, thereby allowing soft contact with the object without damaging the object surface. However, the rate dependency of adhesion control often limits the operation speed and eventually the production throughput. Moreover, the lowest adhesion of elastomers may still be too high to release objects onto some desired substrates, in which case complicated surface structures or additional chemical treatments are employed to decrease the adhesion.

#Embodiments of the present technology generally relate to methods, apparatus, and systems for object manipulation via electrically controlled adhesion. In one example, an apparatus for manipulating an object includes a substrate, an electrically conductive layer disposed on the substrate, and a porous medium including an electrically conductive material. The apparatus also includes a dielectric layer conformally disposed on the porous medium to insulate the porous medium from the object during use. The porosity of the porous medium is about 90% or greater, the adhesive strength of the porous medium is about 1 kPa or lower, and the modulus of the porous medium is about 1 GPa or lower.

#The skilled artisan will understand that the drawings primarily are for illustrative purposes and are not intended to limit the scope of the inventive subject matter described herein. The drawings are not necessarily to scale; in some instances, various aspects of the inventive subject matter disclosed herein may be shown exaggerated or enlarged in the drawings to facilitate an understanding of different features. In the drawings, like reference characters generally refer to like features (e.g., functionally similar and/or structurally similar elements).

#FIGS. 1A and 1B show schematics of apparatus for object manipulation using electrically switchable adhesion.

#FIGS. 2A-2G illustrate a method 200 of fabricating a nanocomposite foamed surface that can be used in the apparatus shown in FIGS. 1A and 1B for object manipulation.

#Nanocomposite Foamed Surfaces for Object Manipulation

#The drawbacks of elastomer-based and velocity controlled pick-and-place operations (e.g., low adhesion on/off ratio and rate-dependent adhesion control) can be addressed by electrostatic adhesion, i.e. adhesion based on electrostatic force. In one implementation discussed in detail below, an example apparatus for object manipulation (also referred to herein as a “nanoporous electrostatic tool” or simply “tool”) is configured to provide for tunable adhesion by inducing charge difference between the tool and the object, or between different areas within the tool (e.g., adjacent electrodes embedded in the tool).

#In some examples of adhesion facilitated by electrostatic force, relatively stiff and planar electrostatic chucks can be used to grip semiconductor wafers in process tools. Electrostatic gripping tools generally include an electrically conductive (mostly metal) surface covered with a thin dielectric layer (e.g., ceramic or polymer). In one example, the conductive surface has a planar shape and can be mechanically stiff. This configuration can be used to handle objects that also have planar surfaces. However, the planar configuration may have less satisfactory contact against objects with rough surface or having complex shapes and may also cause damages on delicate objects when compressed with high pressure. In addition, solid surfaces usually have a low on/off adhesion ratio as the mechanical adhesion is comparable to the maximum electrostatic adhesion.