Functional devices can be directly assembled using microgrippers with an in situ electron microscope. Two simple and compact silicon microgripper designs are investigated here. These are operated by electrothermal actuation, and are used to transfer a catalytically grown multi-walled carbon nanofibre from a fixed position on a substrate to the tip of an atomic force microscope cantilever, inside a scanning electron microscope. Scanning of high aspect ratio trenches using the nanofibre supertip shows a significantly better performance than that with standard pyramidal silicon tips. Based on manipulation experiments as well as a simple analysis, we show that shear pulling (lateral movement of the gripper) is far more effective than tensile pulling (vertical movement of gripper) for the mechanical removal of carbon nanotubes from a substrate.

Nanorobotic handling of carbon nanotubes (CNTs) using microgrippers is one of the most promising approaches for the rapid characterization of the CNTs and also for the assembly of prototypic nanotube-based devices. In this paper, we present pick-and-place nanomanipulation of multi-walled CNTs in a rapid and a reproducible manner. We placed CNTs on copper TEM grids for structural analysis and on AFM probes for the assembly of AFM super-tips. We used electrothermally actuated polysilicon microgrippers designed using topology optimization in the experiments. The microgrippers are able to open as well as close. Topology optimization leads to a 10-100 times improvement of the gripping force compared to conventional designs of similar size. Furthermore, we improved our nanorobotic system to offer more degrees of freedom. TEM investigation of the CNTs shows that the multi-walled tubes are coated with an amorphous carbon layer, which is locally removed at the contact points with the microgripper. The assembled AFM super-tips are used for AFM measurements of microstructures with high aspect ratios.

Abstract-Microgrippers that are able to manipulate nanoobjects reproducibly are key components in 3-D nanomanipulation systems. We present here a monolithic electrothermal microgripper prepared by silicon microfabrication, and demonstrate pickand-place of an as-grown carbon nanotube from a 2-D array onto a transmission electron microscopy grid, as a first step toward a reliable and precise pick-and-place process for carbon nanotubes.

Current research work on the development of different depth-detection methods for supporting pick-andplace manipulations of carbon nanotubes (CNTs) in a scanning electron microscope (SEM) is presented. A nanorobot station capable of performing this manipulation task in the SEM's vacuum chamber has been developed, consisting of two cooperating nanorobots. One robot carries an electrothermal microgripper and also performs the coarse approach between microgripper and CNT. The second robot serves as sample holder and realizes the fine positioning of the CNT sample. For a reliable fine approach between microgripper and CNT as well as an intended future automation of handling tasks, depth-detection methods are required in order to precisely measure and align the zposition of microgripper and CNT. Two different methods for z-position estimation are proposed. The depth from focus method uses the focusing information of SEM images whereas the touchdown sensor concept relies on a bimorph piezo bending actuator. The feasibility of both approaches is shown and first experimental results are discussed. Future work has to show how the proposed methods will increase the efficiency of nanorobotic manipulation and how these methods can advance the automation of nanohandling tasks.