This letter reports the first cloudy-sky land surface temperature (LST) retrieval from the MEdium Resolution Spectral Imager-II (MERSI-II) onboard Fengyun-3D (FY-3D). In this study, a new cloudy-sky LST retrieval algorithm was adapted for FY-3D/MERSI-II. The method consists of two key components: (1) estimating the hypothetical clear-sky LST using geographically weighted regression (GWR) downscaling and linear model correction, and (2) quantifying the temperature difference (ΔT) caused by cloud radiative effect (CRE) based on surface energy balance (SEB) theory. Validation against in situ LST measurements from the SURFRAD and HiWATER networks indicates that the retrieved cloud-sky LST exhibits a bias of 0.02 K and a root mean square error (RMSE) of 3.77 K. The results confirm that the algorithm achieves reliable retrieval of FY-3D/MERSI-II cloudy-sky LST, with the ΔT correction term making a notable contribution. This method is expected to be used to generate the operational FY-3D cloudy-sky LST product.

Satellite microwave remote sensing is acknowledged as the primary method for obtaining global-scale surface soil moisture (SSM) data. Typically, spaceborne microwave sensors aboard polar-orbiting satellites yield SSM estimates with a native spatial resolution of several tens of kilometers and a temporal resolution of about once or twice daily. This indicates considerable potential for enhancing both of their spatial and temporal resolutions. Although spatial downscaling of spaceborne microwave SSM has garnered significant attention recently, the enhancement of their temporal resolution has received less focus. This study pioneers a methodology for generating hourly-scale satellite SSM estimates. The developed approach integrates a novel blending module that combines geostationary satellite observations with a spatially downscaled SSM dataset derived from traditional fusion among microwave and optical observations on polar-orbiting platforms. This blending module leverages land surface temperature (LST) data from geostationary satellites, which effectively quantify SSM variations on an hourly interval upon the thermal inertia theory. Consequently, a comprehensive spatio-temporal integrated framework for SSM downscaling is established to produce hourly-scale SSM at a resolution of 6 km, enhancing upon the daily and 36-km resolutions of existing microwave SSM datasets. Validation of the downscaled hourly SSM estimates was conducted through an established ground soil moisture observatory network in North China, revealing an unbiased root mean square error (ubRMSE) of no higher than 0.04 cm³/cm³. This result confirms preservation of the fundamental accuracy of original microwave SSM retrievals and demonstrates the effectiveness of the developed framework in improving both spatial and temporal representativeness of SSM data.

Integrating functional subunits into a microrobot offers a promising pathway to enhance its operational capabilities. The functional integration of microrobots lies in organizing subunit distribution into a 3-D morphology while balancing the geometry formation affected by subunits and locomotion performance. Here, in this article, discrete microstructured soft-magnetic teeth (MTs) are circularly embedded into an artificial bacterial flagellum (ABF) to function as equivalent subunits, representing a good start to demonstrate the integration of subelements in microrobots through local stress regulation. Based on various substructure patterns, the controllable geometry modulation of ABF-MTs has unveiled the tunable angle-dependent deformation behavior, offering numerous possibilities for geometric morphology and propulsion extension. The outstanding kinematic performance demonstrates the seamless fusion of functionality and propulsion by maintaining locomotion speed, trajectory planning, pursuit, and step-motion-like behavior. Such a physical-forming strategy offers an avenue for incorporating subdevices in microrobot functionalization.

Field-control-based nanorobotic manipulation of ions at the single atomic level is an enabling technique for such applications as in-situ prototyping and characterization for fundamental research and rapid product development of nanoscale and quantum devices such as sensors, batteries, neuromorphic devices, and neuro/brain interfaces. Taking the motion of quantum dots (QDs) manipulated by an electrostatic field steered by a probe tip on a target surface as an example, here we show a deep-learning-based approach for their global motion tracking via the individual atoms both on the surface and inside the body. Transmission electron graphs, element analysis, and crystal topology acquired from an aberration-corrected transmission electron microscope (Cs-TEM) are used to identify the positions, types, and structures of the atoms to understand their kinematics. The results show the feasibility of multi-target tracking of homogeneous atoms by their spatial structure projection, which is very encouraging for further extension to the tracking and regulation of crystalline grains, swarms of ions, ion filaments, and single ions.

Due to the limited cargo/functional element loading and other capabilities of individual microrobots, assembling them for locomotion and disassembling them as arriving at the target is more effective. An approach called rendezvous and docking is proposed in this paper to control the assembly and disassembly of helical microrobots actuated by a uniform rotating magnetic field. Docking is realized around the intersection of their arc orbits with the assistance of a fluidic field. To adjust the distance between the adjacent helical robots suspending in solution but with a distance beyond the acceptable range of the magnetic interaction, their asynchronized velocities are achieved using the interaction between the robots and fluids. For robots rotating at different speeds around their longitudinal axes at a driving frequency lower than the cut-off frequency, different fluidic flows will be generated. Based on the interaction between the robots and the fluids, the translational trajectory paths may be tuned, causing the adjacent robots to move closer. Docking along the tangential direction of rendezvous arc trajectories avoids the instability of the helical robot rotating around the radial direction and the problem of excessive linear speed at the end during assembly so that the robot can rotate stably around its axis while completing the assembly. Besides these, assembled microrobots can also lower the requirements on the imaging resolution of motion tracking and the forces for driving; hence much lower cost for both imaging and driving equipment.

To date, untethered micro/nanorobots have attracted considerable attention in various aspects due to their unique potential for in-vivo applications such as the targeted therapy. One of the most promising types of micro/nanorobots is the class of ferromagnetic microrobots which can be efficiently actuated via gradient/rotational magnetic field generated by less costly electromagnetic coil systems. For performing successful operations, locomotion control of the magnetic microrobots is non-trivial. Modern controllers commonly require motion status-based feedback. To fully utilize those advanced approaches, motion state of one microrobot should be supplied, however it is still challenging in cases. It is noted that, during locomotion, one ferromagnetic microrobot can combine with others to form an unstructured larger one, namely growing magnetic microrobot (GMM), whose dynamic behavior keeps changing, and thus the model-based observers are never applicable. Besides, tracking and estimating states of those unstructured time-varying GMMs in complex surroundings are always challenging, especially for an uneven sampling scenario. In order to accurately estimate the GMM motion status in a complex environment via micro-vision, this study develops an indeterministic observer leveraging on the approach of discriminative correlation filter with channel/spatial reliability (CSR-DCF) and the variable-step finite-time sliding mode (FSM-V) state estimation theory. Experimental study verifies that the proposed observation scheme can effectively estimate motion states of one GMM moving in obstacle surroundings throughout.

Sub-structures such as micro-structured magnetic teeth fabricated with an artificial bacteria flagellum (ABF) are designed for achieving more motion modes, higher precision, and better controllability. To achieve these, a more precise model considering the non-circular cross-sectional features is setup without simplifying the structure as a helical filament with a circular cross-section as having been used in previous investigations, making it possible to include the effects of the substructures into the motion equation. Analyses and experiments verified the correctness. Besides of the geometric effects, our experimental observation also shows an anomalous step-out frequency appeared in an ABF. This asynchronous motion is attributed to the lag of magnetization with respect to the external rotating magnetic field due to the geometries and the soft-magnetic materials of the ribbons, which is different from the regular asynchronous motion solely caused by low Reynolds number of fluid to microscopic swimmers. While the lag of magnetization can be further attributed initiatively to the soft magnetic materials adopted, the feasibility to arrange the easy axis will enable many new possibilities, which is of particular interest in generating more modes for swarms such as cascade stepping out of ABFs with the same nominal overall sizes and for more precise positioning using stepping motion.

To date, untethered microrobots have been receiving tremendous attention for playing implacable roles of maneuverable tools in fields such as microfabrication and biomanipulation. Typical actuation of such untethered tiny robots is the magnetic field-based approaches, including gradient and rotational methods. Compared to the gradient type method, the rotational approach requires much less magnetic field strength to generate efficient actuation for magnetic microrobots. To actuate microrobots desirably, a precise periodic magnetic field should be provided. To generate precise periodic magnetic field with enhanced strength, this paper develops a prototype of 3D magnetic servoing system based on integrated solenoids, performance of which are enhanced by employing iron cores and extended number of coils. Each solenoid is equipped with a Hall sensor to provide real-time feedback signal for performing precise magnetic field control. To precisely regulate this setup, a decoupled asynchronous repetitive control (DARC) scheme is established to generate a desirable 3D periodic magnetic field with noise-level tracking error under the situation of missing execution opportunity randomly. Experimental results demonstrate the effectiveness of the proposed magnetic servoing system, which is promising for dynamic properties characterization of magnetic microrobots.

Scene generation is an important step of robotic drawing. Recent works have shown success in scene generation conditioned on text using a variety of approaches, with which the generated scenes cannot be revised after its generation. To allow modification on generated scenes, we model the scene generation process as a discrete event system. Instead of training text-to-pixel mappings using large datasets, the proposed approach uses object instances retrieved from the Internet to synthesize scenes. Evaluated on 128 experiments using MSCOCO evaluation dataset, the result shows the scene generation performance has been increased by 197%, 22.3%, and 55.7% compared with the state of the art approach on three standard metrics (CIDEr, ROUGH-L, METEOR), respectively. Human evaluation conducted on Amazon Mechanical Turk shows over 80% of generated scenes are considered to have higher recognizability and better alignment with natural language descriptions than baseline works.

Random forests (RFs), an advanced machine learning (ML) method, was used here to develop a robust and rapid quantitative precipitation estimates (QPEs) algorithm for the new-generation geostationary satellite of Himawari-8. In this algorithm, the global precipitation measurement (GPM) product has been employed to train QPE prediction model. The real-time multiband infrared brightness temperature from Himawari-8, combined with the spatiotemporally matched numerical weather prediction (NWP) data from the global forecast system, have been used as predictor variables for QPE. Among the variables used in RF learning model, total precipitable water and$K$-index from NWP data have the highest rankings, indicating the importance of atmospheric environment for QPE. To enhance the accuracy of RF models or to optimize model training, a sample-balance technique has been utilized to adjust the ratios of samples in nonprecipitation/precipitation classification and quantitative precipitation regression data sets. Further sensitivity and validation analyses help determine the optimal RF classification and regression models for predicting nonprecipitation/precipitation pixel and rain rate. The selected RF classification model is found to predict precipitation area with an accuracy of 0.87. For predicted QPE product, the mean-absolute-error and root-mean-square error of RF regression model are 0.51 and 2.0 mm/h, respectively. Overall, the RF ML algorithm has a higher detection rate over homogenous ocean surface as compared with over land. Meanwhile, this RF algorithm tends to underestimate rain rate, especially in the presence of heavy rainfall. Despite this, it still produces a reasonable pattern of rainfall area and intensity, which are highly consistent with GPM observations.

The Medium Resolution Spectral Imager (MERSI) was installed as a key payload on the FengYun-3C (FY-3C) polar-orbit meteorological satellite, which was successfully launched on September 23, 2013. We used 14 months of continuous FY-3C/MERSI Level-1B data (from November 2013 to December 2014) to evaluate the on-orbit image spatial quality. Based on a polar ice block image, a sharp target modulation transfer function (MTF) estimation method is used to quantitatively estimate the MTF value at the Nyquist frequency, which is an index for the spatial quality. The results show very good stability in the first year and a relatively lower spatial quality (MTF approximately 0.15) along the FY-3C/MERSI scan direction. This lower spatial quality is primarily attributed to the known and fixed 27% overlapped scan mode of MERSI, which can significantly reduce the image contrast. By using this fixed overlapped proportion (27%), we develop a fast and robust image restoration algorithm based on the Gaussian elimination (GE) method with lower and upper triangular matrix decomposition (LU). The speed-up ratio of this GE with LU decomposition method can attain a value of 626.30 compared with the traditional GE method when it solves linear equations with 2048 MERSI scan pixels. After the image restoration process, significant enhancement in the image spatial quality along the scan direction for every band of FY-3C/MERSI can be found with an increased MTF value of approximately 0.30. However, we evaluate the possible effect of this restoration algorithm on the original digital number (DN) and reflectance values. We find a slight decrease in the total averaged DN (0.5) and reflectance (<; 0.5%, relative bias) values. The variation in DN or reflectance after the image restoration process exhibits a positive correlation with homogeneity of the original target. Moreover, a sensitivity study on the reflectance reveals that it has a more significant impact on the inhomogeneous pixel with a low DN value.

Sliding probe methods are designed for the in situ characterization of electrical properties of individual 1-D nanostructures. The key to achieving a high resolution is to keep the contact resistance constant by controlling the contact force and area between the specimen and the sliding probe. We have developed several techniques and tools including differential sliding, flexible probes, and specimen-shape-adaptable probes using nanorobotic manipulation. Compared with conventional methods, these sliding probe methods allow in situ characterization with a higher resolution than conventional methods. Furthermore, they are superior for local property characterization, which is of particular interest for heterostructured nanomaterials and defect detection.

We report the nanorobotic in situ forming and characterization of memristors based on individual copper oxide nanowires (CuO NWs) and their potential applications as nanosensors with memory (memristic sensors or “memsensors”). A series of in situ techniques for the experimental investigations of memristors are developed including nanorobotic manipulation, electro-beam-based forming, and electron energy loss spectroscopy (EELS) enabled correlation of transport properties and carrier distribution. All experimental investigations are performed inside a transmission electron microscope (TEM). The initial CuO NW memristors are formed by localized electron-beam irradiation to generate oxygen vacancies as dopants. Current-voltage properties show distinctive hysteresis characteristics of memristors. The mechanism of such memristic behaviors is explained with an oxygen vacancy migration model. The presence and migration of the oxygen vacancies is identified with EELS. Investigations also reveal that the memristic behavior can be influenced by the deformation of the nanowire, showing that the nanowire memristor can serve as a deformation/force memorable sensor. The CuO NW-based memristors will enrich the binary transition oxide family but hold a simpler and more compact design than the conventional thin-film version. With these advantages, the CuO NW-based memristors will not only facilitate their applications in nanoelectronics but play a unique role in micro-/nano-electromechanical systems (MEMS/NEMS) as well.

Electromigration-based deposition (EMBD) is an additive nanolithography technology for the fabrication of three-dimensional (3D) nanostructures. Key techniques for extending the capability of EMBD have been tackled experimentally including the deposition against a non-conductive surface, shape control of the as-deposited nanostructure, and continuous mass feeding. The process is based on nanofluidic mass delivery at the attogram scale from metal-filled carbon nanotubes (m@CNTs) using nanorobotic manipulation inside a transmission electron microscope. By attaching a conductive probe to the sidewall of the CNT, it has been shown that mass flow can be achieved regardless of the conductivity of the object surface. Experiments have shown the influence of heat sinks on the geometries of the deposits from EMBD. By modulating the relative position between the deposit and the heat sinks using dual probes, it has been possible to reshape the deposits. The limited mass encapsulated inside a CNT requires a frequent change of them for depositing large structures. To realize continuous feeding, a reservoir will be an excellent solution. We have observed that the copper inside the neighbor CNTs to the CNT injector can be sucked into the injector. Although the mechanism is not well understood yet, electromigration and atom-by-atom wall-passing-through may be responsible to this phenomenon. This observation enabled a new path for the design of an EMBD system As a general-purposed nanofabrication process, EMBD will enable a variety of applications such as nanorobotic arc welding and assembly, nanoelectrodes direct writing, and nanoscale metallurgy.

Sliding probe methods are designed for the in situ electrical property characterization of individual one-dimensional (1D) nanostructures by eliminating the contact resistance between the fixed-end support and the specimen. The key to achieve a high resolution is to keep a constant resistance between the other end of the specimen contacting to the sliding probe. To achieve this objective, we have developed several important techniques including multipoint continuous sliding, flexible probes, and specimen-shape adapting based on nanorobotic manipulation inside a transmission electron microscope (TEM). With a copper-nanowire-tipped probe, we have shown that a flexible probe facilitates the contact force control. The adapting of the shape of a probe tip is significant for keeping a constant contact area between the probe and the specimen. This can be implemented by using a soft probe or a tip with a shape resembling the profile of the specimen. Here we show that by flowing copper from a nanotube probe against the specimen, it is possible to make a well adapted shape of the tip to the specimen after the copper cooled down. By avoiding stick-slip motion and controlling the contact force and area, it will be possible to keep a constant contact resistance between the sliding probe and the specimen, hence significantly improve the measurement resolution. Sliding probe methods are an in situ technique characterized by higher resolution and simplicity in setup as compared with conventional two- and four-terminal methods, respectively. Furthermore, it is superior for local property characterization, which is of particular interest for hetero-structured nanomaterials and defect detection.

A novel rotary nanomotor is described using two axially aligned, opposing chirality nanotube shuttles. Based on inter-shell screw-like motion of nanotubes, rotary motion is generated by electrostatically pulling the two cores together. Simulations using molecular dynamics show the generation of rotation from armchair nanotube pairs and their actuation properties. The simulation results, together with recently reported progress in realizing batch-fabricated ultra-high density nanotube shuttles, point towards the use of these motors as building blocks in nanoelectromechanical systems (NEMS) and nanorobotic systems for sensing, actuation, and computation applications.

Modes of melting and evaporation of metal at attogram level from individual carbon nanotubes (CNTs) are investigated experimentally using nanorobotic manipulation inside a transmission electron microscope. We compared the melting and evaporation induced by electric current, Joule heating, charge, and ionization. Experiments show that the most effective method is by positively ionizing the encapsulated metal, therefore, an electrostatic field can be used to guide the flow. Applications and potential applications of mass transport and deposition in nanofluidic systems have been presented including self-welding, actuation, and storage.

Artificial bacterial flagella (ABF) are swimming microrobots that mimic the swimming motion of bacteria. The helical swimmer consists of an InGaAs/GaAs/Cr helical nanobelt tail fabricated by a self-scrolling technique with dimensions similar to a natural flagellum, and a thin soft-magnetic metal ¿head¿ consisting of a Cr/Ni/Au multi-layer. The swimming locomotion of ABF is precisely controlled in 3-D by external rotating magnetic fields. Microsphere manipulation is performed by ABF, and experimental results show that both the position and the orientation of microspheres can be precisely controlled. The propelling force of ABF is in the pico-Newton range. We also describe a swarm-like behavior in which three ABF swim in a pack, indicating the potential to handle several micro objects in parallel. Self-propelled devices such as these are candidates for wireless 6-DOF micro and nanomanipulation tools for handling cellular and sub-cellular objects.

Few rotational actuators currently exist with the ability to transmit motion at different speeds, torques, and directions at the nanometer scale. We present work regarding the application of helical nanobelts as linear-to-rotary and rotary-to-linear motion converters. We discuss their ability to rectify device rotation to linear motion for untethered microrobotic applications as well as their application as rotary sample stages for nanoscale imaging.

This paper introduces the concept of nanoelectromechanical systems on a tip (NEMS-on-a-tip). As an example, force sensors based on the interlayer electromechanical coupling of individual multi-walled carbon nanotubes (MWNT) are designed with various configurations. The devices are fabricated and characterized using nanorobotic manipulation inside a scanning electron microscope (SEM). Experimental results verify that the resistance of MWNTs is highly sensitive to applied mechanical load. A further performance analysis also indicates that a force sensor configuration in which two electrodes connect to the inner and outermost shells, respectively, provides the highest sensitivity and resolution (∼1nN) in the presence of lateral forces.

To achieve ultrahigh precision dielectrophoretic (DEP) manipulation of carbon nanotubes (CNTs), a novel technique is investigated both theoretically and experimentally by shaping the local geometries of nanoelectrodes to control the electrohydrodynamic behavior of CNTs. Motion trajectories and positions of CNTs assembled on electrodes are predicted based on calculated DEP forces and torques. Both simulation and experimental results show that the geometries of two opposing electrodes significantly affect the precision and robustness with which CNTs can be deposited. Investigation of an electrode array verifies our model and demonstrates that the spacing between neighboring electrode pairs should be larger than twice the width of electrodes to avoid overlapping of electric fields and imbalance of DEP forces; otherwise unequally distributed electric fields and DEP forces induce a significant number of assembly failures in the array.

A propulsion system similar in size and motion to the helical bacterial flagella motor is presented. The system consists of a magnetic nanocoil as a propeller (27 nm thick ribbon, 3 μm in diameter, 30-40 μm long) driven by an arrangement of macro coils. The macro coils generate a rotating field that induces rotational motion in the nanocoil. Viscous forces during rotation result in a net axial propulsion force on the nanocoil. Modeling of fluid mechanics and magnetics was used to estimate the requirements for such a system. The fabrication of the magnetic nanocoils and the system setup are explained. Experimental results from electromagnetic actuation of nanocoils as well as from their propulsion in both paraffin oil and water are presented. This is the first time a propulsion system of this size and motion-type has been fabricated and experimentally verified.

Nanorobotic spot welding using single-crystalline-copper-filled carbon nanotubes (CNTs) is investigated experimentally inside a transmission electron microscope (TEM). Controlled melting and flowing of copper inside nanotube shells are realized by applying bias voltages between 1.5 V and 2.5 V. The average mass flow rate of the copper was found to be 120 ag/s according to TEM video imaging (measured visually at approximately 11.6 nm/s through the CNT). Successful soldering of a copper-filled CNT onto another CNT using a nanorobotic manipulator shows promise for nano spot welding, which can play a role similar to its macro counterpart for the interconnection of nano building blocks for the assembly of nanoelectronic circuits and nanoelectromechanical systems (NEMS).

Robotic manipulation at the nanometer scale is a promising technology for structuring, characterizing and assembling nano building blocks into nanoelectromechanical systems (NEMS). Combined with recently developed nanofabrication processes, a hybrid approach to building NEMS from SiGe/Si/Cr nanocoils and Si/Cr nanospirals is presented. Nanosensors and nanoactuators are investigated from experimental, theoretical, and design perspectives

This paper describes the characteristics of vegetation condition index (VCI), temperature condition index (TCI), normalized differential water index (NDWI) and vegetation health index (VHI), and uses the relationship between above indices and relative soil moisture to evaluate the index adaptation. The analysis means that different indices have different adaptation. NDWI is not sensitive to the drought. VCI is sensitive to the drought only in the growing time, but has a lag of 10 days. TCI is more sensitive (the max R2=0.52) to drought and can reflect drought without lag, but not stable. However, in the growing time, VHI is the most sensitive to drought (the max R2=0.56) and stable. Finally, this paper analysis such uncertain factors as measurement condition, data quality and index calculation, which affects the adaptation of index. The result shows that VHI has a good adaptation in the growing time and has a nice prospect in drought monitoring.

Nanoscale linear servomotors with integrated position sensing are investigated from experimental, theoretical, and design perspectives. Prismatic motion is realized using the interlayer motion of telescoping multiwalled carbon nanotubes (MWNTs). Position sensing can be achieved by monitoring field emission or by measuring resistance change between an MWNT and a gold substrate during sliding movement. Experimental results demonstrate resolution in the nanometer range. Actuation experiments demonstrate the feasibility of a linear nanoservomotor with integrated position sensing based on field emission. A local "kink"-like fluctuation of emission current is observed, which is caused by the change of the protruding length of the nanotube core, thus demonstrating the potential of using emission as a "linear encoder." The complete extension of the inner core is observed and the electrostatic force is calibrated to be tens of nano-Newtons for individual nanotubes-16.5 nN under a 30-V bias. These results demonstrate the possibility of fabricating linear servomotors at the nanometer scale with integrated position sensing. Note to Practitioners-Nanometer scale actuators and sensors that can provide motion and measurement with nanometer-order resolution will enable new industrial applications in which only a few atoms or molecules are measured, transported, or processed. Linear servomotors will play a significant role in such applications because they provide precision prismatic motion directly without requiring a conversion from rotary to linear motion. Nano linear servomotors are experimentally and theoretically investigated in this paper. The devices take advantage of the ultra-low interlayer friction of a multiwalled carbon nanotube (MWNT). Position sensing feedback is achieved by monitoring field emission, which depends on interelectrode distance, or by measuring resistance change between an MWNT and a gold substrate during sliding movement. Whereas this paper targets long-term nanotechnology contributions, some intermediate results are ready for applications in the near future. The interlayer sliding motion demonstrated would enable the building of devices, such as Gigahertz oscillators and attolitter nanosyringes, and the sensors used for position feedback could find applications independently in a macro or microscale machine for detecting proximity, touch, displacement, or orientation.

Nanoscale linear servomotors with integrated position sensing are investigated from experimental, theoretical, and design perspectives. Prismatic motion is realized using the interlayer motion of telescoping multi-walled carbon nanotubes (MWNTs). Position sensing can be achieved by monitoring field emission or by measuring resistance change between a MWNT and a gold substrate during sliding movement. Experimental results demonstrate resolution in the nanometer range. Actuation experiments demonstrate the feasibility of a linear nano servomotor with integrated position sensing based on field emission. A local “kink”-like fluctuation of emission current is observed, which is caused by the change of the protruding length of the nanotube core, thus demonstrating the potential of using emission as a “linear encoder”. Complete extension of the inner core is observed and the electrostatic force is calibrated to be tens of nano-Newtons for individual nanotubes— 13.3 to 23.3 nN for voltages from 20 to 30V. These results demonstrate the possibility of fabricating linear servomotors at the nanometer scale with integrated position sensing.

Linear encoders for nanoscale position sensing based on single carbon nanotube (CNT) arrays are presented. Vertically aligned single multi-walled carbon nanotubes (MWNTs) are realized using a combination of e-beam lithography and plasma-enhanced chemical vapour deposition (PECVD) growth. Electron beam lithography is used to define 50-150 nm nickel catalyst dots at precise locations on a silicon chip. Precise control of the position, density and alignment of the tubes has been achieved. Aligned nanotube arrays with spacing varying from 250 nm to 25 /spl mu/m are realized. Field emission properties of the array are investigated inside a scanning electron microscope (SEM) equipped with a 3-DOF nanorobotic manipulator with nanometer resolution functioning as a scanning anode. With this scanning anode and the single MWNT array, a nano encoder is investigated experimentally. Vertical position is detected by the change in emission current, whereas the horizontal position of the scanning anode is sensed from the emission distribution. A resolution of 98.3 nm in the vertical direction and 38.0 nm (best: 12.9 nm) in the lateral direction has been achieved.

Field emission properties of individual multi-walled carbon nanotubes (MWNT) have been investigated and applied to several nano devices. Field emission current changes with the distance between the tip of a carbon nanotube (CNT) emitter and a counterpart anode, which can be applied as the principle for an approaching sensor to detect nanometer scale distance by the observation of field emission current in real time. Higher field emission current in microampere-scale from a CNT emitter has been shown strong enough for performing electron-beam-induced deposition (EBID) without obvious degradation of emitters. EBID with CNT emitters can provide much higher specific deposition rate, potentially better productivity due to the possibility to be used in parallel, and richer metallic composition as introducing organometallic precursors such as W(CO)/sub 6/ as presented In this work. Energy dispersive X-ray spectrometry (EDS) analysis on deposits from W(CO)/sub 6/ shows that the mass of tungsten reaches up to over 80% among the compositions.

A hybrid nanorobotic manipulation system, which is integrated with a nanorobotic manipulator inside a transmission electron microscope (TEM) and nanorobotic manipulators inside a scanning electron microscope (SEM), is presented. The new type of nanomanipulation system has high enough resolution to identify nano-scale objects due to the adoption of a TEM, and efficient and rapid nanomanipulations are realized with wide enough working space of the SEM nanomanipulators. The TEM nanomanipulator has been constructed with 4 multi-layer piezoelectric actuators for driving in 3 translational degrees of freedom (DOFs) and a passively driven 3-DOF sample stage through SEM nanorobotic manipulators to perform relatively complex manipulations whereas to keep compact volume to be installed inside the narrow vacuum chamber of a TEM. To show the effectiveness of the system, the interlayer resistance of a destructively fabricated multi-walled carbon nanotube has been measured inside a SEM whereas the telescoping structure formed by pulling out inner layers from outer layers of the tube is observed inside a TEM.

Force measurement with pico-Newton (pN) order resolution using a carbon nanotube (CNT) probe, which is calibrated by the electromechanical resonance is presented. Based on the theoretical analysis, a CNT is suitable material for the sensitive force measurement. A CNT probe is constructed by attaching a CNT to the tip of the commercially available atomic force microscope (AFM) cantilever or tungsten needle probe by the electron-beam-induced deposition (EBID) though the nanorobotic manipulators inside a field-emission scanning electron microscope (FE-SEM). In order to attach a CNT quickly and correctly, CNTs are dispersed in ethanol by ultrasonic waves for several hours and oriented by electrophoresis. The elastic moduli of CNTs are calibrated from electromechanical resonance frequency by applied electrostatic forces. We measured pico-Newton order contact forces with a CNT probe, which is constructed with nanorobotic manipulators, by measuring deformation of a CNT probe from FE-SEM images.

A nano laboratory-a prototype nano manufacturing system-is presented, which is composed with a nanorobotic manipulation system with 4 units and 16 degrees-of-freedom (DOFs), a nano fabrication system based on electron-beam-induced deposition (EBID) with an internal or external precursor evaporation reservoir equipped with a thermal field emission electron source or a nanotube cold cathode, and a real-time observation and measurement system based on a field emission scanning electron microscope (FESEM) equipped with 3-4 conventional atomic force microscope (AFM) cantilevers, piezoresistive levers or nanotube probes. Nanotube devices including a mass flow sensor, a linear bearing, and nanotube scissors are fabricated in the nano laboratory.

Properties and potential applications of carbon nanotubes are summarized by emphasizing the aspects of nanoelectronics and nanoelectromechanical systems (NEMS). The main technologies for the assembly of nanodevices through nanomanipulations with scanning probe microscopes and nanorobotic manipulators are overviewed, focusing on that of nanotubes. Key techniques for nanoassembly include the preparation of nano building blocks and property characterization of them, the positioning of the building blocks with nanometer-scale resolution, and the connection of them. Nanorobotic manipulations, which are characterized by multiple degrees of freedom (DOFs) with both position and orientation control, independently actuated multiprobes, and a real-time observation system, are one of the most promising technologies for assembling complex nanodevices in three-dimensional space. With a nano laboratory, a prototype nanomanufacturing system based on a 16-DOF nanorobotic manipulation system, the assembly of nanodevices with multiwalled carbon nanotubes are presented. Nanotube-based building blocks are prepared by directly picking up, in situ property characterization, destructive fabrication, and shape modifications. Kinds of nanotube junctions, the fundamental elements for both nanoelectronics and NEMS, are constructed by positioning the building blocks together under the real-time observation with a field-emission scanning electron microscope, connecting them with naturally existing van der Waals forces, electron-beam-induced deposition, or mechanochemical bonding.

Nanoassembly of multi-walled carbon nanotubes (MWNTs) in three-dimensional space is realized by positioning these building blocks with nanometer order accuracy, joining them together through van der Waals forces, and fixing them with electron-beam-induced deposition (EBID) or chemical bonds through mechanochemical nanorobotic manipulations. MWNT I-junctions and Y-junctions are constructed. For parallel nanoassembly, the concept of parallel EBID is presented, a MWNT electron-beam emitter is prepared through nanoassembly of MWNTs onto commercially available atomic force microscope (AFM) cantilevers, and the feasibility of using them for parallel EBID is investigated.

Multi-walled carbon nanotubes (MWNTs) are manipulated in 3D space with a 10-DOF nanorobotic manipulator, which is actuated with PZTs and Picomotors/sup TM/ (New Focus Inc.) and operated inside a scanning electronic microscope (SEM). The coarse linear resolutions of the manipulator are better than 30 nm (X, Y, Z stages actuated by Picomotors) and the rotary one 2 mrad, while the resolutions of fine motions (actuated by PZTs) are within nano-order. AFM cantilevers are used as the end-effector. Several kinds of manipulations of MWNTs are performed with the developed manipulators with the assistance of dielectrophoresis and van der Waals forces. A single MWNT with estimated dimensions of /spl phi/ 40 nm /spl times/7 /spl mu/m has been picked up on an AFM cantilever. Another /spl phi/ 50 nm /spl times/6 /spl mu/m MWNT is placed between two cantilevers, and still another /spl phi/ 40 nm /spl times/8 /spl mu/m MWNT is bent between a cantilever and sample substrate. Carbon nanotube (CNT) junctions are basic building blocks for more complex devices based on CNTs. A cross-junction was constructed with two MWNTs of dimensions of /spl sim//spl phi/ 40 nm /spl times/6 /spl mu/m and /spl sim//spl phi/ 50 nm /spl times/7 /spl mu/m, and a T-junction was made of two MWNTs with the dimensions of /spl sim//spl phi/ 40 nm /spl times/3 /spl mu/m and /spl sim//spl phi/ 50 nm /spl times/2 /spl mu/m. Force measurements are performed and the flexural rigidity and Young's modulus of an /spl sim//spl phi/ 30 nm /spl times/7 /spl mu/m MWNT are estimated to be 8.641/spl times/10/sup -20/ Nm/sup 2/ and 2.17 TPa respectively. Such manipulations are essential for both the property research of CNTs and the fabrication of CNT-based NEMS.