An AFM tip replacement system compatible with all ambient media and operation modalities

Replacement of an atomic force microscope (AFM) probe is an unavoidable aspect of the instrument's use, since its tip gets blunted or contaminated with use. Here, we propose a technique to replace only the tip of the AFM probe. Significantly, the technique is compatible with all the conventional modalities and media in which AFM is operated. The proposed technique employs a paraffin wax micro-particle as an integrated adhesive microgripper. By suitably controlling the phase of this material, it is employed to pick up and detach tips, and to grip them firmly while interacting with samples. The strategy has been experimentally demonstrated to work under conditions that are most likely to affect the microgripper integrity, namely, during contact mode imaging and in water. Despite this, the obtained images are shown to be identical to that obtained in air and with conventional probes. Further, reliability studies on the microgripper revealed that its lifetime is significantly higher than that of the probe-tip. Finally, the gripper has also been demonstrated to enable detachment of the AFM tip

An out-of-plane linear motion measurement system based on optical beam deflection

Measurement of out-of-plane linear motion with high precision and bandwidth is indispensable for development of precision motion stages and for dynamic characterization of mechanical structures. This paper presents an optical beam deflection (OBD) based system for measurement of out-of-plane linear motion for fully reflective samples. The system also achieves nearly zero cross-sensitivity to angular motion, and a large working distance. The sensitivities to linear and angular motion are analytically obtained and employed to optimize the system design. The optimal shot-noise limited resolution is shown to be less than one angstrom over a bandwidth in excess of 1 kHz. Subsequently, the system is experimentally realized and the sensitivities to out-of-plane motions are calibrated using a novel strategy. The linear sensitivity is found to be in agreement with theory. The angular sensitivity is shown to be over 7.5-times smaller than that of conventional OBD. Finally, the measurement system is employed to measure the transient response of a piezo-positioner, and, with the aid of an open-loop controller, reduce the settling time by about 90%. It is also employed to operate the positioner in closed-loop and demonstrate significant minimization of hysteresis and positioning error

A magnetic micro-manipulator for application of three dimensional forces

Magnetic manipulation finds diverse applications in actuation, characterization, and manipulation of micro-and nano-scale samples. This paper presents the design and development of a novel magnetic micro-manipulator for application of three-dimensional forces on a magnetic micro-bead. A simple analytical model is proposed to obtain the forces of interaction between the magnetic micromanipulator and a magnetic micro-bead. Subsequently, guidelines are proposed to perform systematic design and analysis of the micro-manipulator. The designed micro-manipulator is fabricated and evaluated. The manipulator is experimentally demonstrated to possess an electrical bandwidth of about 1 MHz. The ability of the micro-manipulator to apply both in-plane and out-of-plane forces is demonstrated by actuating permanent-magnet micro-beads attached to micro-cantilever beams. The deformations of the micro-cantilevers are also employed to calibrate the dependence of in-plane and out-of-plane forces on the position of the micro-bead relative to the micro-manipulator. The experimentally obtained dependences are found to agree well with theory. (C) 2015 AIP Publishing LLC

An Integrated Magnetic Actuation System for High-Speed Atomic Force Microscopy

High-speed atomic force microscopy enables in situ studies of dynamic phenomena at the nanometer-scale. This paper presents the design, fabrication, and evaluation of an integrated magnetic actuation system for high-speed atomic force microscopy. The proposed system consists of a microcantilever probe with an attached permanent magnet particle and a microactuator for generation of magnetic field. Novel geometries are proposed for the probe, the magnetic particle, and the actuator that together result in a high bandwidth and adequate actuation gain. A lumped parameter model is developed for the probe's dynamics and employed to optimize its design. Subsequently the integrated actuation system has been fabricated and evaluated. The actuator has been shown to generate actuation fields as high as 216 G with associated temperature rise of less than 8 degrees C. The probe has been evaluated to have an Eigen-frequency of 104 kHz with an actuation gain of 1 nm/G in air. Characterization of the probe in water reveals the reduction in Eigen-frequency to be merely 23%, which is nearly 3-fold less than that of a conventional probe. Finally, the developed actuation system has been employed to perform high-speed dynamic mode imaging of a grating inside aqueous medium at various imaging rates up to 1.25 frames/s

Tip Motion Control and Scanning of a Reorientable Micromanipulator With Axially Located Tip

Two-axis micromanipulators, whose tip orientation and position can be controlled in real time in the scanning plane, enable versatile probing systems for 2.5-D nanometrology. The key to achieve high-precision probing systems is to accurately control the interaction point of the manipulator tip when its orientation is changed. This paper presents the development of a probing system wherein the deviation in the end point due to large orientation changes is controlled to within 10 nm. To achieve this, a novel micromanipulator design is first proposed, wherein the end point of the tip is located on the axis of rotation. Next, the residual tip motion caused by fabrication error and actuation crosstalk is modeled and a systematic method to compensate it is presented. The manipulator is fabricated and the performance of the developed scheme to control tip position during orientation change is experimentally validated. Subsequently, the two-axis probing system is demonstrated to scan the full top surface of a micropipette down to a diameter of 300 nm

Design and Modeling of an Active Five-Axis Compliant Micromanipulator

This paper presents the design and modeling of an active five-axis compliant micromanipulator whose tip orientation can be independently controlled by large angles about two axes and the tip-position can be controlled in three dimensions. These features enable precise control of the contact point of the tip and the tip-sample interaction forces with three-dimensional nanoscale objects, including those features that are conventionally inaccessible. Control of the tip-motion is realized by means of electromagnetic actuation combined with a novel kinematic and structural design of the micromanipulator, which, in addition, also ensures compatibility with existing high-resolution motion-measurement systems. The design and analysis of the manipulator structure and those of the actuation system are first presented. Quasi-static and dynamic lumped-parameter (LP) models are then derived for the five-axis compliant micromanipulator. Finite element (FE) analysis is employed to validate these models, which are subsequently used to study the effects of tip orientation on the mechanical characteristics of the five-axis micromanipulator. Finally, a prototype of the designed five-axis manipulator is fabricated by means of focused ion-beam milling (FIB)

Design and Evaluation of Torsional Probes for Multifrequency Atomic Force Microscopy

Multifrequency atomic force microscopy is a powerful nanoscale imaging and characterization technique that involves excitation of the atomic force microscope (AFM) probe and measurement of its response at multiple frequencies. This paper reports the design, fabrication, and evaluation of AFM probes with a specified set of torsional eigen-frequencies that facilitate enhancement of sensitivity in multifrequency AFM. A general approach is proposed to design the probes, which includes the design of their generic geometry, adoption of a simple lumped-parameter model, guidelines for determination of the initial dimensions, and an iterative scheme to obtain a probe with the specified eigen-frequencies. The proposed approach is employed to design a harmonic probe wherein the second and the third eigen-frequencies are the corresponding harmonics of the first eigen-frequency. The probe is subsequently fabricated and evaluated. The experimentally evaluated eigen-frequencies and associated mode shapes are shown to closely match the theoretical results. Finally, a simulation study is performed to demonstrate significant improvements in sensitivity to the second-and the third-harmonic spectral components of the tip-sample interaction force with the harmonic probe compared to that of a conventional probe

Two-axis force sensing and control of a Reorientable scanning probe

This paper presents the design and implementation of a reorientable scanning probe that is capable of two-axis force sensing and control in the 2-D scanning (X-Z) plane. The probe is comprised of three major components, namely a compliant manipulator, laser measurement system, and magnetic actuation system. Control of the position and orientation of the probe tip is realized by means of magnetic actuation combined with a novel structural design. The design of the manipulator's compliance and that of the optical path of the laser measurement system together enable achieving sensitivity to lateral (X) forces that is nearly identical to that of normal (Z) forces. The achieved sensitivity ratio, of about 0.6, is significantly higher than that of conventional scanning probe systems. The theoretical bases for the structural design and the sensitivity of the two-axis force sensing system are presented. Subsequently, fabrication of the manipulator is described and the result of experimental evaluation of the scanning probe's features is discussed. The scanning probe is used to access the vertical and re-entrant features on the two sides of a cylindrical micropipette, which are subsequently scanned by regulating the lateral force of tip-sample interaction

A System for Replacement and Reuse of Tips in Atomic Force Microscopy

The ability to replace and reuse only the tip of the probe in an atomic force microscope (AFM) enables employing a greater variety of probes, enhancing their functionalities, and simplifying their use for imaging, metrology, and manipulation. This paper presents the development and evaluation of a system that employs a liquid meniscus at the end of an AFM probe as amicrogripper to pick up tips, hold them during use, and subsequently drop them off. The system also comprises a tip supply station and a tip holder that supply new tips and preserve used tips for potential future reuse. The designs of the tip supply station and the tip holder are discussed, and the stiffness of the liquid meniscus is analyzed. Subsequently, a prototype of the system is fabricated. It is demonstrated to pick up a new AFM tip and image a calibration grating without any artifacts. The image is shown to be identical to that obtained by a conventional AFM probe. Likewise, tip detachment and reuse are also experimentally demonstrated. The reused tip is shown to image a calibration grating without artifacts, thereby demonstrating that the detachment and pick-up process does not deteriorate the quality of the replaceable AFM tip

Design and Evaluation of a Robust Optical Beam-Interruption-Based Vehicle Classifier System

This paper presents the design and development of a novel optical vehicle classifier system, which is based on interruption of laser beams, that is suitable for use in places with poor transportation infrastructure. The system can estimate the speed, axle count, wheelbase, tire diameter, and the lane of motion of a vehicle. The design of the system eliminates the need for careful optical alignment, whereas the proposed estimation strategies render the estimates insensitive to angular mounting errors and to unevenness of the road. Strategies to estimate vehicular parameters are described along with the optimization of the geometry of the system to minimize estimation errors due to quantization. The system is subsequently fabricated, and the proposed features of the system are experimentally demonstrated. The relative errors in the estimation of velocity and tire diameter are shown to be within 0.5% and to change by less than 17% for angular mounting errors up to 30 degrees. In the field, the classifier demonstrates accuracy better than 97.5% and 94%, respectively, in the estimation of the wheelbase and lane of motion and can classify vehicles with an average accuracy of over 89.5%