High internal phase emulsions have been widely used as templates for various porous materials, but special strategies are required to form, in particular, particle-covered ones that have been more ...difficult to obtain. Here, we report a versatile strategy to produce a stable high internal phase Pickering emulsion by exploiting a depletion interaction between an emulsion droplet and a particle using water-soluble polymers as a depletant. This attractive interaction facilitating the adsorption of particles onto the droplet interface and simultaneously suppressing desorption once adsorbed. This technique can be universally applied to nearly any kind of particle to stabilize an interface with the help of various non- or weakly adsorbing polymers as a depletant, which can be solidified to provide porous materials for many applications.
In this paper, a high-precision dual-servo stage with a magnetically levitated fine stage is described. For magnetic levitation, a Halbach linear active magnetic bearing (HLAMB) is used. The HLAMB ...has two functions: gravity compensation and actively control of vertical motion. To implement these functions, the HLAMB utilizes permanent magnet arrays and Lorentz coils. The fine stage has positioning capabilities with 6 DOF due to four HLAMBs and four voice coil motors (VCM). The HLAMBs control out-of-plane motions, and the VCM control in-plane motions. The fine stage achieves high-precision position feedback using laser interferometers and capacitive sensors. The coarse stage has an H-type structure that can carry the fine stage 300 mm by 300 mm along the x - and y-axes. Positioning and scanning performances are verified by the experimental results. It has ±10 and ±15 nm in-position stability in the x- and y-axes, respectively. At the scan with 10 mm/s constant velocity, ±1 nm mean tracking error and 4.7 nm jitter were obtained.
A nonresonant, fiber-optic raster scanning endomicroscope was developed using a quarter-tubular piezoelectric (PZT) actuator. A fiber lever mechanism was utilized to enhance the small actuation range ...of the tubular PZT actuator and to increase its field-of-view. Finite element method simulation of the endoscopic probe was conducted for various conditions to maximize its scanning range. After fabricating the probe using a double clad fiber, we obtained two-photon fluorescence images using raster beam scanning of the fiber. The outer diameter of the probe was 3.5 mm and its rigid distal length was 30 mm including a high numerical aperture gradient index lens. These features are sufficient for input into the instrumental channel of a commercial colonoscope or gastroscope to obtain high resolution images in vivo.
Active vibration isolation systems (AVIS) reduce the vibrations transmitted to ultraprecision mechanical systems by providing managed stiffness and damping. Many types of AVIS are used in various ...fields. In nanoprecision measuring instrument fields, such as atomic force microscopy and scanning probe microscopy, the requirement for isolation of ground vibrations has always been of great interest to researchers. Bench-top-type six-degree-of-freedom (6-DOF) AVIS have been widely used in ultraprecision measuring applications. This paper describes the design, modeling, optimization, and validation of a new 6-DOF AVIS. The unique feature of the proposed system is its voice coil motor actuator that uses a Halbach magnet array to produce a high force constant. The results obtained using the proposed AVIS show that it can serve as a bench-top device for precision measuring machines.
Time-delay control has been verified as a simple and robust controller for robot manipulators. However, time-delay estimation (TDE) error inherently exists and critically affects both the closed-loop ...stability and control performance. In this paper, we propose a remedy for the TDE error that involves a combination of a nonlinear damping component and a novel fast-convergent error dynamics. Nonlinear damping incorporated with a backstepping design is adopted to counteract TDE error and ensure closed-loop stability. The fast-convergent error dynamics, constructed by means of terminal sliding mode (TSM), is introduced to enhance the control performance degraded by the TDE error. Through a rigorous stability analysis, it is proved that the tracking error of the closed-loop system due to the proposed control scheme is globally uniformly ultimately bounded. Through simulations and experiments, it is verified that the nonlinear damping counteracts the TDE error, while the TSM speeds up the convergence of the error dynamics. Finally, these two elements together substantially enhance the control accuracy.
This paper describes the design and implementation of a novel spherical actuator that can generate two tilt-motion degrees of freedom. Voice coil motors were adopted as actuators in a spherical ...actuator to utilize their simple driving principle and constant torque coefficient characteristic. The sensing and guiding mechanism was built inside the proposed spherical actuator and enabled compactness and ease of connection to other application systems. The actuator was designed using a design optimization framework to obtain high torque. A prototype actuator was manufactured with optimally designed parameters, and its performance was evaluated.
We propose a mechanism for a single-axis flexure-based nano-positioning stage. A self-guided displacement amplification mechanism enables a large range of motion—up to a millimeter—with a compact ...stage size. Our device has a skewed double-compound parallelogram structure that acts as a motion guide and provides displacement amplification, thereby eliminating a serial connection. Its structural symmetry improves positioning accuracy by reducing parasitic motion error and thermal deformation. A millimeter-range piezo-actuated nano-positioning stage is implemented using the self-guided displacement amplification mechanism. The stage was designed using design optimization frameworks to obtain the highest fundamental resonance frequency under constraints for predetermined travel range, stress, and size. The effectiveness of the proposed mechanism is experimentally verified. Also, we demonstrate that the fabricated stage has superior volume efficency compared to other stages of similar size.
► We designed a new single-axis millimeter-range flexure-based nano-positioning stage. ► Our stage has a skewed double-compound parallelogram mechanism. ► The mechanism acts as both a motion guide and a displacement amplification mechanism. ► We designed the stage was designed using design optimization frameworks. ► The fabricated stage has superior volume efficiency compared to other similar stages.
Flexure mechanisms have been widely used for nanometer positioning systems. This article presents a novel conceptual design of an ultra-precision 3-degrees of freedom (XYθ(Z)) positioning system with ...nanometer precision. The main purpose of this novel stage design is for the application of measurement equipment, in particular biological specimens. The stage was designed as a hollow type and with a compact size for the inverted microscope. This stage includes piezoelectric transducer actuators, double compound amplification mechanisms, moving plate, and capacitor sensors. The double compound amplification mechanism was designed using a mathematical model and analyzed by the finite element method. Since the relationship between the variables of the hinge parameters and system performances are complicated, an optimization procedure was used to obtain the optimal design parameters, which maximized the system bandwidth. Based on the solution of the optimization problem, the design of the stage and FEM simulation results are presented. Finally, the stage was manufactured and tested.
Inflammation plays essential role in development of plaque disruption and coronary stent-associated complications. This study aimed to examine whether intracoronary dual-modal optical coherence ...tomography (OCT)-near-infrared fluorescence (NIRF) structural-molecular imaging with indocyanine green (ICG) can estimate inflammation in swine coronary artery.
After administration of clinically approved NIRF-enhancing ICG (2.0 mg/kg) or saline, rapid coronary imaging (20 mm/s pullback speed) using a fully integrated OCT-NIRF catheter was safely performed in 12 atheromatous Yucatan minipigs and in 7 drug-eluting stent (DES)-implanted Yorkshire pigs. Stronger NIRF activity was identified in OCT-proven high-risk plaque compared to normal or saline-injected controls (P = 0.0016), which was validated on ex vivo fluorescence reflectance imaging. In vivo plaque target-to-background ratio (pTBR) was much higher in inflamed lipid-rich plaque compared to fibrous plaque (P < 0.0001). In vivo and ex vivo peak pTBRs correlated significantly (P < 0.0022). In vitro cellular ICG uptake and histological validations corroborated the OCT-NIRF findings in vivo. Indocyanine green colocalization with macrophages and lipids of human plaques was confirmed with autopsy atheroma specimens. Two weeks after DES deployment, OCT-NIRF imaging detected strong NIRF signals along stent struts, which was significantly higher than baseline (P = 0.0156). Histologically, NIRF signals in peri-strut tissue co-localized well with macrophages.
The OCT-NIRF imaging with a clinical dose of ICG was feasible to accurately assess plaque inflammation and DES-related inflammation in a beating coronary artery. This highly translatable dual-modal molecular-structural imaging strategy could be relevant for clinical intracoronary estimation of high-risk plaques and DES biology.
This paper presents a novel XY nano-positioning stage using a compliant parallel mechanism with small crosstalk and yaw motion. A parallel mechanism can implement multi-degree-of-freedom motion with ...a small footprint. However, this implies crosstalk between the motion axes. In an effort to reduce crosstalk and yaw motion, we proposed a novel flexure guide structure. The proposed stage consists of two flexure displacement amplifiers driven by piezoelectric actuators, two combined double four-bar flexure guides, and two additional parallelogram guides. To prevent the rotational deformation of one amplifier due to the transverse force of the other, we introduce an intermediate leaf spring at the output ends of the amplifiers. This new parallel mechanism is optimally designed based on an analytical model of the stage to assure small crosstalk and yaw motion. The analytical model is verified as being well-described using a finite element analysis. An XY nano-positioning stage of size 150 × 150 × 30 mm
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is fabricated following the optimal design. Experiments are carried out to verify the static and dynamic performances of the proposed XY nano-positioning stage. The proposed stage has an X and Y directional motion range of 120 μm in closed loop. The resolution of the stage is 3 nm in both the X and Y directional motions. The actual crosstalk and yaw were limited to 0.770 μm and 13.5 μrad, while in the optimal design they were estimated at 0.5 μm and 15 μrad, respectively.
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