Lefeng Wang

Harbin Institute of Technology | HIT

Docking is a common step in magnetic helical microrobot operations. However, the boundary effect causes helical microrobots to drift laterally near the container bottom. The mismatch between orientation and movement direction further complicates manual steering. In this paper, an automatic control method for on-plane docking of magnetic helical mic...

Liquid bridges formation and rupture between solid surfaces have widespread applications in micro gripping, self-alignment, particles wetting. In the present study, an investigation of the axisymmetric liquid bridge rupture between a sphere and a spherical concave was performed systematically. Detailed analysis was conducted on the influence of the...

Faced with complex and diverse tasks, researchers seek to introduce stimuli-responsive materials into the field of microrobots. Magnetic helical microrobots based on shape-memory polymers demonstrate excellent locomotion capability and programmable shape transformations. However, the stimulation method of shape changes is still dependent on the ris...

The magnetically driven micro soft robot is a hot research topic in the field of micro robotics. The magnetic torque of each part of the robot rotates with its deformation, so the magnetic torque and magnetic force to which the robot is subjected are difficult to be calculated directly. The lack of physical interfaces for torque distribution in man...

In recent years, soft microrobots based on flexible materials have received increasing attention. Most of the current studies on soft microrobots have implemented only one motion mode, and because the motion environment is often set inside liquid, the strategies of multimodal motion control near the solid–liquid interface are insufficient. In this...

Diversified complex tasks put forward higher requirements on shape transformation abilities of magnetic microrobots. Shape memory polymers (SMPs) with desirable properties are ideal options for the development of microrobots. However, programming shape transformations for such small SMP robotic structures is still difficult. Here, a parametric desi...

Microrobots working at liquid surfaces have immense potential for micromanipulation in tight and enclosed spaces, whereas constructing agile and functional microrobots with simple structures at liquid surfaces is a great challenge. Herein, a pair of magnetic circular microdisks working as partners at ethylene glycol (EG) surfaces are proposed in or...

Inspired by bacterial flagella in nature, magnetic helical microswimmer is an ideal model to perform complex task in a low Reynolds number environments. Shape Memory Polymers (SMPs) with desirable properties are considered as one of the most preferred options for the development of small-scale robots. However, fabricating and programming strategies...

The micro soft robot which mimics the movement of microorganisms is one of the important research directions in the field of robotics. This study proposes a programmable 3D printing method for magnetically driven micro soft robots based on surface tension. High-performance surfactant was used to reduce the surface free energy of the printing substr...

Vertical data collected by Scanning Electron Microscopy (SEM) are important for sample characterization, 3D reconstruction, and flex manipulation. Traditional methods are limited by the extent to which the probe obstructs the view of the sample along the vertical axis. Herein, we propose a novel SEM microprobe for measuring the vertical distance be...

Liquid metal shows great potential in the fields of consumer electronics, wearable devices, and electronic skin, etc. At the same time, the liquid metal of the micro-Nano structure can also be used to obtain structures such as nanowires. However, traditional direct writing methods are difficult to achieve high precision due to the nozzle diameter,...

Micromotors are key devices for various micromanipulation systems for potential scientific and industrial applications. In this study, a magnetic micromotor consisting of an 800 μmdiameter plate supported by a single droplet on a hydrophobic substrate is constructed. It is actuated by external uniform magnetic fields generated by three-dimensional...

Functionalized microrobots have various potential applications in aquatic missions depending on their locomotion and manipulation capabilities. In this study, a novel star-shaped magnetic microrobot capable of locomotion and manipulating microobjects at water surfaces is reported. The aquatic microrobot, a 40 μm-thick star-shaped sheet, could not o...

This note proposes a novel linear-rotary piezoelectric positioning stage which utilizes a double octagon driving module to produce rectangular driving trajectories of a surface. A rotational pair is embedded into a translational pair to constitute the 2-DOF output end (mover/rotor). With the circulating driving trajectories, the device can deliver...

The conventional methods to measure the force output of piezoelectric ceramic are imprecise. This article proposes an instrument based on a piezoelectric actuator to study the force output of piezoelectric ceramic. This instrument mainly consists of a flexible hinge structure based on a piezoelectric actuator, a pair of support structures, and a pr...

This paper proposes a novel stepping type piezoelectric motor that can perform long range rotational motion with high resolution. Pseudo-rigid-body method is used to establish the kinematics model of the driving mechanism and analyze the motion trajectory of the driving foot. The static deformation of the driving mechanism is simulated by finite el...

The capillary force of the axisymmetric liquid bridge between two continuously fully wet disks is investigated. The energy minimization method shows excellent consistency with the method based on the Young–Laplace equation. The capillary force between two disks is typically repulsive at small distances, and becomes attractive with increasing separa...

A novel inchworm type piezoelectric rotary actuator based on wedge block clamping is presented in this paper. With the help of only one piezo-stack and two clamping blocks, the proposed actuator can imitate the walking mode of inchworm to deliver stable long range rotary motion accompanying with high driving resolution. Owing to the advantages of t...

This article presents the piezoelectric ultrasonic linear actuator based on binate feet driving. The actuator is equipped with a rhombus binate feet mechanism to generate two synchronous rectangle driving trajectories. With the help of the two synchronous trajectories, the proposed actuator can deliver stable long-range motion (the designed maximum...

This study proposes a piezoelectric rotary actuator based on compliant foot driving. With the help of driving modules which are composed of four compliant feet and four piezo-stacks, the designed actuator can produce large range rotary motions in both forward and backward directions with a high resolution. The mechanical structure and the moving pr...

This study proposes a novel piezoelectric rotary motor which can output long range continuous motion. With the help of two piezo-stacks which are located at a 90° included angle, the motor can achieve circular motion trajectory of a cylindrical driving surface and the rotor can be driven by the cylindrical surface to deliver long range continuous r...

A novel stick-slip type piezoelectric rotary actuator is proposed in this paper. The actuator equips with a parallelogram driving mechanism to generate a pair of variable force couple to drive the rotor. Two piezo-stacks are used to deform the parallelogram driving mechanism to realize large range motions with high resolution in both forward and ba...

The capillary force of a liquid bridge with a pinned contact line between a small disk and a parallel plate is investigated by simulation and experiments. The numerical minimization simulation method is utilized to calculate the capillary force. The results show excellent agreement with the Young–Laplace equation method. An experimental setup is bu...

This study presents a piezoelectric rotary actuator which is equipped with a bionic driving mechanism imitating the centipede foot. The configuration and the operational principle are introduced in detail. The movement model is established to analyze the motion of the actuator. We establish a set of experimental system and corresponding experiments...

This paper reports a direct-write strategy that rapidly produces rounded cross-sectional molds for casting of microfluidic channels in polydimethylsiloxane (PDMS). Robotically controlled microextrusion of a thixotropic ink through a micronozzle onto a substrate surface generates user-defined positive relief structures that serve as molds. Printed l...

Bacteria with helical flagella show an ideal mechanism to swim at low Reynolds number. For application of artificial microswimmers, it is desirable to identify effects of structural and geometrical parameters on the swimming performance. In this study, a double-end helical swimmer is proposed based on the usual single-end helical one to improve the...

To satisfy the manipulation requirement of auxiliary droplets release aiming at micro-objects, a droplet dispensing method based on piezoelectric drive is presented. The dispenser of piezoelectric micro-jet, which employs piezoelectric actuator to achieve non-contact dispensing, is designed. Accordingly, the formation condition of single droplet is...

A stepping type piezoelectric linear actuator based on compliant foot driving is proposed in this paper. With the help of four piezo-stacks and four compliant feet, the designed actuator can produce large range linear motions in both positive and negative directions with high accuracy. The mechanical structure and the operating principle are discus...

This paper presents the design, fabrication and calibration of a novel two-dimension microforce sensor with nano-Newton resolution. The sensor, mainly composed of a clamped–clamped beam (horizontal detecting beam), an overhanging beam (vertical detecting beam) and a half-folded beam, is highly sensitive to microforces in the horizontal (parallel to...

In this paper, we present an extrusion printing technique for producing spherical and cylindrical plano-convex microlens arrays with controllable feature dimensions. This technique employs a robotic adhesive dispenser for robotically controlled microextrusion of ultraviolet (UV) curable polymer onto a glass substrate surface to directly deposit the...

In the paper, we present a single-step lithography system whereby the robotically controlled micro-extrusion of resist adhesive onto a substrate surface to directly create resist adhesive patterns of interest. This system is modified from a robotic adhesive dispenser by shrinking the aperture of the nozzle to a few micrometers aiming to realize pat...

A microdroplet distribution method based on water condensation on hydrophobic surface is presented to obtain micromanipulation droplet for capillary gripping. Accordingly, the droplet condition required in micro-objects transfer (pick-and-place) is investigated. Model of liquid bridge stretching is established during microdroplet dispensing. Two co...

A continuous flow ink etching (CFIE) method is presented to directly create micropatterns on a 60 nm thick silicon dioxide (SiO2) layer. This technique employs a micropipette filled with potassium bifluoride (KHF2) aqueous solution to localize SiO2 dissolution in the vicinity of the micropipette tip. Both dot and line features with well-defined edg...

Stick-slip accurate manipulator (composed of piezo and slider) is widely applied in scanning electron microscope (SEM). However, for its positioning control in SEM, conventional displacement sensors are hard to be used because of their big physical dimensions or magnetic working principles. To solve these problems, this paper proposes to use strain...

OBJECTIVE: To explore the significance of resection margin and tumor number on survival of patients with small liver cancer after hepatectomy.

A micromanipulation method based on liquid droplets is widely used as a non-destructive technology to pick-and-place micrometer-scale objects. We focus on the development of a single-probe capillary microgripper to execute reliable micromanipulation tasks. By controlling dropwise condensation on a probe tip, the water droplet volume on the hydropho...

The forces acting on submillimeter spheres at the air-water interface are investigated theoretically and experimentally. To calculate the capillary force acting on the sphere, an iterative method is used to determine the immersing position of the liquid interface on the sphere for a given distance. Then the total forces acting on the sphere are con...

On the basis of the presented micromanipulation method of condensation on hydrophobic surface, the volume of the water droplet on the hydrophobic tip surface can be dynamically varied which helps to obtain appropriate capillary lifting forces using the designed droplet micromanipulator. The single droplet growth model is established to analyze the...

Capillary interactions are fundamentally important in many scientific and industrial fields. However, most existing models of the capillary bridges and capillary forces between two solids with a mediated liquid, are based on extremely simple geometrical configurations, such as sphere-plate, sphere-sphere, and plate-plate. The capillary bridge and c...

According to the problem of drawing force control in the fused biconical tapering process of polarization maintaining fiber (PMF) coupler, an online computer control method of drawing force is presented, which includes the computer, drawing mechanism, rotary position encoders and a control circuit. By detecting the rotation angle of fiber clamp, th...

Fused biconical tapering (FBT) is an important method of manufacturing polarization-maintaining fiber (PMF) couplers. However, the tension on the ends of the fibers can affect the performance of the coupler. In this paper, a computer-based method of controlling the drawing force was presented. The system includes a drawing mechanism, rotary positio...

The heating temperature is one of the key factors in the fiber fused biconical taper manufacture, which can affect the component performance. In order to improve the temperature stability and controllability in the heating region, the high-voltage arc heating device is presented and arc heating, heating region temperature and fiber preheating are s...

A capillary-gripping method that enables micro-objects to be picked up flexibly and reliably is described. By controlling the dropwise condensation on a probe tip, the volume of the water droplet on the hydrophobic tip surface can be dynamically varied, which helps to establish appropriate capillary lifting forces during micromanipulation tasks. Dr...

The capillary interaction between a sphere and a flat substrate has been widely investigated. Considering the complex shape of single asperities in real configurations, a more general model of capillary adhesion force including a power law shape index of asperities is developed. For the interaction between a single asperity with any axisymmetric po...

This paper presents a method to exactly calculate the capillary bridge profile and capillary force between a probe tip with a power-law profile and a surface or nanoparticle at various humidities. The shape of the probe tip is denoted by a power-law profile including a shape index, which is a general extension of the usual parabolids. The accuracy...

Pick-and-place of micro-objects is a basic task in various micromanipulation demands. Reliable releasing of micro-objects is usually disturbed due to strong scale effects. This paper focuses on a vacuum micro-gripper with vibration releasing functionality, which was designed and assembled for reliable micromanipulation tasks. Accordingly, a vibrati...

Microdroplet dispensing has numerous applications in biotechnology, microelectronic packaging and microassembly. The rapid developments of these fields tend to demand smaller and smaller microdroplets. In order to achieve single picoliter-volume droplets, a piezoelectric micro-dispensing system is developed in this paper. The factors affecting the...

Microparts transfer plays an important role in various micromanipulation and microassembly tasks. One typical way of microparts transfer is based on the pick-and-place method with a microgripper. Microparts have the potential risks to be damaged due to the local stress concentration when they are gripped and it is a great challenge to release them...

Research and development of nano/micro-sized objects and systems have received considerable interest in the last few decades and were accelerated in the last decade due to the emergence of nanotechnology. Compliant mechanisms have made an enormous contribution in the design process of various fields such as for adaptive structures, hand-held tools,...

Compliant mechanisms have made an enormous contribution in the design process of various fields such as for adaptive structures, hand-held tools, components in transportations, electronics, and surgical tools. The use of compliant mechanisms will help in reducing the number of components, which therefore decrease manufacturing cost and additionally...

Magnetic microrobots have a wide variety of applications in micro/nano-manipulation, micro/nano sensing and biomedical fields. Untethered magnetic microrobots are usually driven by a group of electromagnetic coils. To control the magnetic microrobots trajectory it is of utmost importance to know the magnitude of the magnetic force applied on them....

Flexible and reliable gripping is a fundamental task in various micromanipulation and microassembly fields. Shape-controllable menisci based on pressure adjustment were proposed to pick up microobjects. Lifting force is provided by a controllable liquid bridge which is formed between the capillary tube and the microobject. The volume and the shape...

The extinction ratio is the characteristic parameter of polarization-maintaining (PM) fiber couplers. The detection accuracy of polarization angle is related to the extinction ratio, and affects the thin-diameter PM fiber coupler performances greatly. A series of image processing steps including median filtering, adaptive image morphology, and maxi...

In this study, porous architectures with controllable morphologies on Aluminum foils were fabricated by a simple solution method using zinc nitrate hexahydrate and hexamethylenetetramine as reactants. Unlike works reported previously, we show that the porous architectures on the surface of Aluminum foils can be adjusted by controlling the molar rat...

This paper presents the dynamic dimensional synthesis of a 6-degree-of-freedom (6-DOF) precision parallel manipulator with 3 inextensible links. The dynamic model of the parallel manipulator is provided in detail based on the inverse kinematics. A novel global dynamic performance index of parallel manipulator defined by the maximum driving torque o...

The contact model for rough surfaces with power-law axisymmetric asperities in the presence of adhesion is developed. The extended JKR adhesive contact model for power-law axisymmetric asperities, denoted as JKR-n, developed by Zheng and Yu (2007, "Using the Dugdale Approximation to Match a Specific Interaction in the Adhesive Contact of Elastic Ob...

Influence of the Tabor parameter on the roughness-induced adhesion hysteresis was investigated. To achieve this, the adhesive contact model of single asperities was considered by incorporating the Maugis-dugdale model and its corresponding extension firstly. Further more, the load-approach relationship of adhesive contact between a rough surface an...

This paper presents a new structure of slip-stick positioner with a high bearing capacity, which is designed according to the requirement of nano-manipulation in the Scanning Electron Microscope (SEM). In addition, to analyze the performance of the slip-stick positioner, a dynamic model is developed in MATLAB/Simulink. The experimental results demo...

The dynamic separation of two parallel microplates with an intervening liquid meniscus is studied theoretically. The dynamic model considering the meniscus force and the viscous force between the plates in the separation process was developed. With typical simulation parameters, the magnitudes of various forces were compared before the separation o...

The meniscus force between nanoobjects with a mediated liquid bridge plays an important role in many applications due to scale effects. As an typical configuration, the meniscus force between two spherical nanoparticles at various humidities is studied theoretically. The numerical method and the usual approximation method of calculating the meniscu...

In order to achieve the requirement of measuring forces during micromanipulation, a cantilever-based sensor using optical laser and position sensitive device (PSD) to monitor cantilever deflection is designed. To increase the resolution of the sensor at the specified measurement range, mechanical analysis and noise analysis are adopted to optimize...

The presence of a liquid meniscus between solids can greatly affect the adhesion. A mathematical model is presented to investigate the dynamic separation process of a sphere from a flat or sphere with an intervening liquid meniscus under a constant applied force. For each case, the meniscus and viscous force are considered to account for the adhesi...

Adhesion of solid surfaces plays a significant role in many technical fields especially at micro and nano scale. The effect of asperity shape on the adhesion hysteresis originated from surface roughness has been investigated theoretically in this paper. Based on the adhesive contact model of single asperities with axisymmetric power-law shapes, the...

To utilize the adhesion forces and avoid the design complexity derived from the electrochemical treatment of operating tools, a method for micro-objects manipulation based on the capillary force is presented. The pickup and release model of micromanipulation were established. The manipulation scheme was performed by mechanical motion to change the...

Nanomanipulation is a key enabling technology for many nanometer scale applications. To realize the full 6-DOF nanomanipulation, parallel micromanipulators have manys advantages comparing to the serial ones. Due to the machining and assembly errors, kinematic calibration is necessary to improve the accuracy further. For the 3-limb 6-dof manipulator...

We investigate the capillary forces between submillimeter spheres and flat surfaces at constant liquid volumes theoretically and experimentally. An iterative method is used to estimate the capillary force with contact angles as the boundary conditions and the constant volume as a constraint. The theoretical analysis shows that the maximum capillary...

A 3-PPTRR parallel mechanism is presented in this paper. Six high resolution ceramic motors have been used as actuators in the parallel robot for precise manipulation applications. The inverse kinematics of the robot is analysed based on the geometrical restriction, in addition the Jacobian matrix is deduced with the vector method. A global perform...

To understand capillary interactions between probe tips and nanoparticles under ambient conditions, a theoretical model of capillary forces between them is developed based on the geometric relations. It is found that the contribution of surface tension force to the total capillary force attains to similar order of magnitude as the capillary pressur...

To understand capillary interactions between probe tips and nanoparticles under ambient conditions, a theoretical model of capillary forces between them is developed based on the geometric relations. It is found that the contribution of surface tension force to the total capillary force attains to similar order of magnitude as the capillary pressur...

The elastic-plastic adhesive contact model of microparts surfaces with low adhesion parameters is developed based on the fractal rough surfaces description. The critical transition area from elastic to plastic deformation of single asperity contact is determined by the plastic deformation condition. Based on this, the relation between the applied l...

A 3-PPSR parallel micromanipulator with 6-DOF driven by piezoelectric actuators is presented to avoid the complex structure and reduce the assembly error of the usual 6-limed ones. It is very compact and helpful to improve the accuracy using the monolithic bottom stage and only three fixed-length rods with flexure hinges at the two ends. To analyze...

Van der Waals interactions are always present in handling micro objects and will influence the whole manipulation process. This paper investigates the effects of van der Waals forces on the design and planning of micromanipulation. Origins of van der Waals interactions are shown first. Van der Waals forces between micro objects of several typical c...

A novel three-limb six degree-of-freedom (DOF) parallel micromanipulator with flexure hinges driven by piezoelectric actuators is presented. Its uniqueness lies in three inextensible limbs with specified flexure hinges and driving its input motions from a monolithic base plate that consists of three 2-DOF compliant mechanisms, unlike of the most si...

This paper presents a multi-sensor system for optical precise assembly. The system utilizes macro-micro robot for high precision assembly, which consists of a 6-DOF parallel robot for coarse positioning, a 5-DOF stage driven by piezoelectric actuators for fine positioning, a gripper, a multi-sensor system, and an optical system. Mechanism design an...

Objective: To evaluate the clinical characteristics and different therapeutic methods for treating cholangiocellular carcinoma and to examine the factors correlated with outcome in order to guide clinical treatment and improve prognosis. Methods: Clinical data of 41 cases with cholangiocellular carcinoma from the Chinese Academy of Medical Science...