Block Phase Correlation-Based Automatic Drift Compensation for Atomic Force Microscopes

Automatic nanomanipulation and nanofabrication with an Atomic Force Microscope (AFM) is a precursor for nanomanufacturing. In ambient conditions without stringent environmental controls, nanomanipulation tasks require extensive human intervention to compensate for the many spatial uncertainties of the AFM. Among these uncertainties, thermal drift is especially hard to solve because it tends to increase with time and cannot be compensated simultaneously by feedback. In this paper, an automatic compensation scheme is introduced to measure and estimate drift. This information can be subsequently utilized to compensate for the thermal drift so that a real-time controller for nanomanipulation can be designed as if drift does not exist. Experimental results show that the proposed compensation scheme can predict drift with a small error. Future work is aimed at reducing the error even further through temperature feedback. Keywords - nanomanipulation, Atomic Force microscope, drift, Phase-Correlation Method, Neural Networ

Automatic Drift Compensation Using Phase Correlation Method for Nanomanipulation

Nanomanipulation and nanofabrication with an atomic force microscope (AFM) or other scanning probe microscope (SPM) are a precursor for nanomanufacturing. It is still a challenging task to accomplish nanomanipulation automatically. In ambient conditions without stringent environmental controls, the task of nanomanipulation requires extensive human intervention to compensate for the spatial uncertainties of the SPM. Among these uncertainties, the thermal drift, which affects spatial resolution, is especially hard to solve because it tends to increase with time, and cannot be compensated simultaneously by feedback from the instrument. In this paper, a novel automatic compensation scheme is introduced to measure and estimate the drift one-step ahead. The scheme can be subsequently utilized to compensate for the thermal drift so that a real-time controller for nanomanipulation can be designed, as if the drift did not exist. Experimental results show that the proposed compensation scheme can predict drift with a small error, and therefore, can be embedded in the controller for manipulation tasks

MICROCANTILEVER-BASED FORCE SENSING, CONTROL AND IMAGING

This dissertation presents a distributed-parameters base modeling framework for microcantilever (MC)-based force sensing and control with applications to nanomanipulation and imaging. Due to the widespread applications of MCs in nanoscale force sensing or atomic force microscopy with nano-Newton to pico-Newton force measurement requirements, precise modeling of the involved MCs is essential. Along this line, a distributed-parameters modeling framework is proposed which is followed by a modified robust controller with perturbation estimation to target the problem of delay in nanoscale imaging and manipulation. It is shown that the proposed nonlinear model-based controller can stabilize such nanomanipulation process in a very short time compared to available conventional methods. Such modeling and control development could pave the pathway towards MC-based manipulation and positioning. The first application of the MC-based (a piezoresistive MC) force sensors in this dissertation includes MC-based mass sensing with applications to biological species detection. MC-based sensing has recently attracted extensive interest in many chemical and biological applications due to its sensitivity, extreme applicability and low cost. By measuring the stiffness of MCs experimentally, the effect of adsorption of target molecules can be quantified. To measure MC\u27s stiffness, an in-house nanoscale force sensing setup is designed and fabricated which utilizes a piezoresistive MC to measure the force acting on the MC\u27s tip with nano-Newton resolution. In the second application, the proposed MC-based force sensor is utilized to achieve a fast-scan laser-free Atomic Force Microscopy (AFM). Tracking control of piezoelectric actuators in various applications including scanning probe microscopes is limited by sudden step discontinuities within time-varying continuous trajectories. For this, a switching control strategy is proposed for effective tracking of such discontinuous trajectories. A new spiral path planning is also proposed here which improves scanning rate of the AFM. Implementation of the proposed modeling and controller in a laser-free AFM setup yields high quality image of surfaces with stepped topographies at frequencies up to 30 Hz. As the last application of the MC-based force sensors, a nanomanipulator named here MM3A® is utilized for nanomanipulation purposes. The area of control and manipulation at the nanoscale has recently received widespread attention in different technologies such as fabricating electronic chipsets, testing and assembly of MEMS and NEMS, micro-injection and manipulation of chromosomes and genes. To overcome the lack of position sensor on this particular manipulator, a fused vision force feedback robust controller is proposed. The effects of utilization of the image and force feedbacks are individually discussed and analyzed for use in the developed fused vision force feedback control framework in order to achieve ultra precise positioning and optimal performance

Adaptive Critic Neural Network Force Controller for Atomic Force Microscope-Based Nanomanipulation

Automating the task of nanomanipulation is extremely important since it is tedious for humans. This paper proposes an atomic force microscope (AFM) based force controller to push nano particles on the substrates. A block phase correlation-based algorithm is embedded into the controller for the compensation of the thermal drift which is considered as the main external uncertainty during nanomanipulation. Then, the interactive forces and dynamics between the tip and the particle, particle and the substrate are modeled and analyzed. Further, an adaptive critic NN controller based on adaptive dynamic programming algorithm is designed and the task of pushing nano particles is demonstrated. This adaptive critic NN position/force controller utilizes a single NN in order to approximate the cost functional and subsequently the optimal control input is calculated. Finally, the convergence of the states, NN weight estimates and force errors are shown

Calibration and Nonlinearity Compensation for Force Application in AFM based Nanomanipulation

Abstract — Both the extent and accuracy of force application in atomic force microscope (AFM) nanomanipulation are significantly limited by the nonlinearity of the commonly used optical lever with a nonlinear position-sensitive detector (PSD). In order to compensate the nonlinearity of the optical lever, a nonlinear calibration method is presented. This method applies the nonlinear curve fit to a full-range position-voltage response of the photodiode, obtaining a continuous function of its voltagerelated sensitivity. Thus, Interaction forces can be defined as integrals of this sensitivity function between any two responses of photodiode voltage outputs, instead of rough transformation with a single conversion factor. The lateral position-voltage response of the photodiode, a universally acknowledged puzzle, was directly characterized by an accurately calibrated force sensor composed of a tippless piezoresistive force sensor, regardless of any knowledge of the cantilevers and laser measuring system. Experiments using a rectangular cantilever (normal force constant 0.24 N/m) demonstrated that the proposed nonlinear calibration method restrained the sensitivity error of normal position-voltage responses to 3.6 % and extended the force application range. Index Terms — Atomic force microscope, nanomanipulation, force calibration, nonlinearity compensation. I

Atomic Force Microscopy Tip-enhanced Laser Ablation

In the present work, an apertureless atomic force microscope (AFM) tip-enhanced laser ablation (TELA) system was developed and investigated. An AFM was coupled to an optical parametric oscillator (OPO) wavelength tunable laser for sample ablation with a submicron sampling size. The AFM was used to image the surface and hold the AFM tip 10 nm above the sample surface. The AFM tip is coated with a layer of gold with a thickness of 35 nm. The incident laser wavelength was tuned in the visible and near-infrared (IR) region and focused on the AFM tip. With the tip-enhancement effect, ablation craters on the surface with a submicron size were obtained. The mechanism of TELA was investigated using anthracene and three laser dyes: rhodamine B, methylene blue, and IR 797 chloride. All samples were prepared in thin films and the laser energy was set just below their far-field ablation threshold. The wavelength was tuned from 450 to 1100 nm to cover the visible and near-IR range. It was found that ablation is independent of the absorption of the compounds. The ablation crater volume was measured and found to have a maximum at 500 nm and an approximately linear drop to 800 nm. Craters could not be produced between 800 and 1200 nm and were slightly smaller at 450 nm compared to 500 nm. Apertureless TELA was then performed to sample plasmid DNA with 532 nm, which resulted in a sampling volume of 0.14 μm3 with 12% in variation. The captured DNA was amplified and the amount of sample transferred from each ablation crater was quantitated at 20 ag/spot

NANOSCALE DEVICES CONSISTING OF HETEROSTRUCTURES OF CARBON NANOTUBES AND TWO-DIMENSIONAL LAYERED MATERIALS

One dimensional carbon nanotubes (CNTs) and two-dimensional layered materials like graphene, MoS2, hexagonal boron nitride (hBN), etc. with different electrical and mechanical properties are great candidates for many applications in the future. In this study the synthesis and growth of carbon nanotubes on both conducting graphene and graphite substrates as well as insulating hBN substrate with precise crystallographic orientation is achieved. We show that the nanotubes have a clear preference to align to specific crystal directions of the underlying graphene or hBN substrate. On thicker flakes of graphite, the edges of these 2D materials can control the orientation of these carbon nanotubes. This integrated aligned growth of materials with similar lattices provides a promising route to achieving intricate nanoscale electrical circuits. Furthermore, short channel nanoscale devices consisting of the heterostructure of 1D and 2D materials are fabricated. In these nanoscale devices the nanogap is created due to etching of few layer graphene flake through hydrogenation and the channel is either carbon nanotubes or 2D materials like graphene and MoS2. Finally the transport properties of these nanoscale devices is studied

Multi-Sensorial Interface for 3D Teleoperation at Micro and Nanoscale

International audienceThis paper presents the design of a new tool for 3D manipulations at micro and nanoscale based on the coupling between a high performance haptic system (the ERGOS system) and two Atomic Force Microscope (AFM) probes mounted on quartz tuning fork resonators, acting as a nano tweezers. This unique combination provides new characteristics and possibilities for the localization and manipulation of (sub)micronic objects in 3 dimensions. The nano robot is controlled through a dual sensorial interface including 3D haptic and visual rendering, it is capable of performing a number of real-time tasks on different samples in order to analyse their dynamic effects when interacting with the AFM tips. The goal is then to be able to compare mechanical properties of different matters (stiffness of soft or hard matter) and to handle submicronic objects in 3 dimensions