Xianping Liu

• BEng, MSc, PhD
• Professor at University of Warwick

Liver cells are the basic functional unit of the liver. However, repeated or sustained injury leads to structural disorders of liver lobules, proliferation of fibrous tissue and changes in structure, thus increasing scar tissue. Cellular fibrosis affects tissue stiffness, shear force, and other cellular mechanical forces. Mechanical force character...

The viscoelasticity of cells serves as a biomarker that reveals changes induced by malignant transformation, which aids the cytological examinations. However, differences in the measurement methods and parameters have prevented the consistent and effective characterization of the viscoelastic phenotype of cells. To address this issue, nanomechanica...

Hepatocellular carcinoma is a high‐risk malignant tumor. Hepatoma cells are transformed from normal cells and have unique surface nanofeatures in addition to the characteristics of the original cells. In this paper, atomic force microscopy was used to extract the three‐dimensional morphology and mechanical information of HL‐7702 human hepatocytes a...

In this paper, the differences and similarities between two-layer and three-layer self-piercing riveting (SPR) joints were systematically analysed by combining experimental tests and a finite element (FE) model. The influences of top-to-middle sheet thickness ratio (r1) on the joining results of three-layer joints were also numerically investigated...

This study presents a dynamic modeling and analysis methodology for the 3-PRS parallel mechanism. First, an improved reduced dynamic model of component substructures is proposed using the dynamic condensation technique and the rigid multipoint constraints at the joint/interface level, leading to a minimum set of generalized coordinates for external...

This study proposes an improved semi-analytical approach for contact stiffness modeling of bolted joints in a machine tool system. First, nonlinear contact stress distribution within a single-bolted joint is obtained from the simulation results of finite element analysis software. Second, employing the Hertz contact theory and fractal theory, the c...

In this study, experimental and numerical investigations were carried out to achieve a comprehensive understanding of the impact of surface conditions on self-piercing riveting (SPR) joint quality. Oil lubrication and sandpaper grinding were employed in experimental tests to change surface conditions at rivet/top sheet, top/bottom sheets and bottom...

This study addresses a dynamic modeling and design methodology for machine tools based on parallel artificial neural networks and genetic algorithms. Firstly, subjected to geometrical and static stiffness constraints, a machine tool optimization problem is proposed by minimizing the weighted functions of lower-order natural frequencies and frequenc...

This study presents a rapid predicting method for lower-order dynamic performances of machine tools. Firstly, the governing equation of motion of the component substructure is obtained drawing on the dynamic condensation from the finite element analysis. Secondly, employing the rigid multipoint constraints at the joint and interface level, the impr...

Lay description Atomic force microscope (AFM) provides a direct method to measure the morphological and mechanical properties of cells in real time at the atomic scale with high force sensitivity and precise spatial resolution. In addition, the AFM‐based indentation method has unique advantages of small deformation and less damage to living cells....

Density and Young’s modulus are critical parameters in biological research, which can be used to characterize molecules, cells, or tissues in the diagnosis of severe diseases. Microcantilever resonators are ideal tools to measure the physical parameters of small objects at the micro/nanoscale. In this study, a mathematical model was built based on...

Self-piercing riveting (SPR) is one of the major joining processes in the automotive industry. However, the frequently used design method for multiple SPR joints is still time-consuming, and relies heavily on engineers’ experience and experimental SPR tests. This research focuses on simplifying the joint design process and improving the design robu...

By taking a Stewart platform as an example, this paper presents a novel calibration method by designing a robust joint compensator based on artificial neural networks. In this method, the pose error arising from various time-independent error sources is treated as that produced only by configuration-dependent joint motion errors equivalently, thus...

Cancer is now responsible for the major leading cause of death worldwide. It is noteworthy that lung cancer has been recognized as the highest incidence (11.6%) and mortality (18.4%) for combined sexes among a variety of cancer diseases. Therefore, it is of great value to investigate the mechanical properties of lung cancerous cells for early diagn...

When a three-dimensional (3D)-vision sensor is adopted to achieve high-precision measurement-assisted robotic machining, hand–eye calibration is necessary to determine the position and orientation between the 3D-vision sensor and the robot end-effector. However, errors exist in hand–eye calibration data, including robot poses and sensor measurement...

By combining experimental SPR tests with a finite element (FE) model, the influences of top sheet thickness (Tt), bottom sheet thickness (Tb) and rivet length (L) on the joint formation mechanisms were systematically investigated in this study. Single factor experiments were firstly conducted to uncover the three joining parameters' effects on the...

Interrupted experimental tests were carried out to investigate the impacts of adhesive layer on the Riv(et)-Bonding processes with different die types. The adhesive layer’s influences on the quality of Riv-Bonded joints with different top sheet thickness (Tt) were also studied. It was found that the distribution of trapped adhesive was significantl...

Cancer is currently drawing more and more attention as the leading factor in death worldwide. However, little research has been directed towards investigating the micro/nanoscale mechanical properties of cancer cells treated by targeted drugs to evaluate the model systems of targeted drugs using atomic force microscopy (AFM) nano-indentation, espec...

In this study, artificial neural network (ANN) was adopted to predict the quality of SPR joints. Three ANN models were developed respectively for the key joint quality indicators: the interlock, the remaining bottom sheet thickness at the joint center (Tcen) and under the rivet tip (Ttip). Experimental SPR tests were performed and the results verif...

Self-pierce riveting (SPR) is a major joining method used in the automotive industry. However, there still lacks a fast and easy-to-use joint quality prediction tool available for the automotive engineers. In this study, the simple but effective regression analysis method was applied to quickly predict the SPR joint quality. Two regression models w...

Nowadays, the Riv(et)-Bonding technique has become a major joining approach in the automotive industry. It effectively incorporates the benefits of the adhesive bonding and the self-pierce riveting (SPR), but overcomes their individual drawbacks. Finite element (FE) simulation of the SPR process now plays a very important role during the product de...

This study systematically investigated the influences of cutting positions on the measurement accuracy of the self-piercing riveted joint quality indicators. Evaluation and correction methods were proposed for the first time to estimate and compensate the interlock error caused by improper cutting positions. It was found that the measurement accura...

Detection sensitivity is one of the essential indices for nano-resonator-based sensing. Multiple mechanisms, such as the counteractive effects of mass and stiffness, have been revealed to contribute to the detection sensitivity, making the sensitivity analysis a complex and under-explored issue. In this study, we develop an analytical frequency mod...

Hand-eye calibration is a fundamental step for a robot equipped with vision systems. However, this problem usually interacts with robot calibration because robot geometric parameters are not very precise. In this article, a new calibration method considering the rotation parameters of the robot pose is proposed. First, a constraint least square mod...

The high demand of efficient large-scale machining operations by concurrently decreasing operating time and costs has led to an increasing usage of mobile robotic systems. This paper introduces a mobile robotic system which is consisted of a hybrid robot named TriMule on an automated guided vehicle, and a fringe-projection-based measurement system....

Super-hydrophobicity is attractive due to their special functions. Fluoride reagents are widely used to fabricate super-hydrophobic coatings by reducing surface free energy. Previous papers have been extensively investigated the chemical stability of such super-hydrophobic coatings in acid, salt and alkaline solutions. However, they just described...

Stearic acid and fluoroalkylsilane are widely used chemical modification to fabricate super-hydrophobic surface in corrosion resistant exploration. However, extensive works have just severally explored their anticorrosive performance in salt solution. Very rare work has focus on comparing their corrosion resistant performance in corrosive solution...

Comparing with laser irradiation only, the laser ablation combined with chemical modification process is a widely used technique to obtain bio-inspired super-hydrophobic surface. However, the as-prepared surfaces may be polluted by toxic substance during chemical modification such as fluoroalkyl silane and stearic acid. The side effect of polluted...

Vascular endothelial cells form a barrier that blocks the delivery of drugs entering into brain tissue for central nervous system disease treatment. The mechanical responses of vascular endothelial cells play a key role in the progress of drugs passing through the blood–brain barrier. Although nanoindentation experiment by using AFM (Atomic Force M...

Transient dynamics of tapping mode atomic force microscope (AFM) for critical dimension measurement are analyzed. A simplified nonlinear model of AFM is presented to describe the forced vibration of the micro cantilever-tip system with consideration of both contact and non-contact transient behavior for critical dimension measurement. The governing...

Mechanobiology analysis has been considered one of the important parameters to explore the physiological behavior inside cells. However, the morphology and mechanical characterization of live cells by employing atomic force acoustic microscopy (AFAM) has rarely been investigated to date. In this paper, the morphological and mechanical properties of...

This work aims to propose a newly-emerged method using laser irradiation in liquid for the fabrication of metal-organic highly hydrophobic aluminum surface with excellent corrosion resistant performance. The corrosion results revealed that the laser-induced porous structure with ovoid-like particles, and simultaneously integration of low-free-energ...

Extensive studies have been carried out to investigate the stability of super-hydrophobic surfaces under acid, alkali and salt solutions. It is noted that the previous literature just demonstrated a variety of experimental phenomena. However, very rare work has focused on the protection mechanism or failure mechanism of fluorinated super-hydrophobi...

To facilitate the die selection for new self-piercing riveting (SPR) joint configurations, it is necessary to find out how the critical die geometric parameters influence the SPR process. In this study, a two-dimensional (2D) axisymmetric simulation model was developed to numerically study the riveting process. The influences of the die type, the d...

A method to enhance the harmonics of tapping mode atomic force microscopy is proposed in this study through an attached mass with finite size. It is demonstrated that ratios between higher-order natural frequencies and the fundamental one can be tuned to be specified integers with this method. The first three eigenmodes could be excited simultaneou...

Nature inspired super-hydrophobic surface has aroused extensive attention on corrosion prevention. More works have investigated the instant corrosion resistance of fresh super-hydrophobic surface, but less research focused on its stability when immersed into corrosive solution for long time. Recently, another bio-mimic surface with slippery coating...

Tubule epithelial cell is a complex element that not only exhibits elasticity behaviour, but also presents nonlinear and time-dependent behaviour during any stage of its life cycle. Responses of tubule epithelial cells to physical stimuli are influenced by their mechanical properties. However, accurately constitution of their mechanical properties...

In the manufacturing process of sophisticated and individualized large components, classical solutions to build large machine tools cannot meet the demand. A hybrid robot, which is made up of a 3 degree-of-freedom (3-DOF) parallel manipulator and a 2-DOF serial manipulator, has been developed as a plug-and-play robotized module that can be rapidly...

Atomic force microscopy (AFM) is one of the useful tools in the fields of nanoscale measurement and manipulation. High speed scanning is one of the crucial requirements for live cell imaging and soft matter characterization. The scanning speed is limited by the bandwidth of the AFM’s detection and actuation components. Generally, the bandwidth of a...

Laser interference lithography is attracting increasing interest among researchers because of its high-efficiency and low-cost in fabrication of patterns. However, there are always operational errors in the setup of interference systems, which have a significant effect on the finally produced interference pattern. This paper has systematically inve...

Nanoindentation test performed by atomic force microscopy is highly recommended for the characterisation of soft materials at nanoscale. The assumption proposed in the characterisation is that the material is pure elastic with no viscosity. However, this assumption does not represent the real characteristics of soft materials such as bio tissue or...

In this paper, superhydrophobic surfaces were fabricated on nitinol alloy by utilizing nanosecond laser and silanization process. Grid pattern surfaces are obtained by adjusting the adjacent scanning path from 60 μm to 100 μm and increasing 10 μm by step, which named g60, g70, g80, g90 and g100 respectively. Silanization process is performed to ach...

Two of the key issues to meet the requirements of micro/nano manipulation in some complex cases are the adequate workspace and payload capacity of the moving platform. This paper presents the development and control methodologies for a 2 degrees of freedom (DOF) flexure-based micro/nano positioning stage with the capabilities of decoupling motion a...

A super-hydrophobic aluminum alloy surface with decorated pillar arrays was obtained by hybrid laser ablation and further silanization process. The as-prepared surface showed a high apparent contact angle of 158.2 ± 2.0° and low sliding angle of 3 ± 1°. Surface morphologies and surface chemistry were explored to obtain insights into the generation...

In this study, finite element analysis and nano-indentation experiments were carried out to investigate the effect of surface tilt on the nanoindentation test results. This paper revealed that standard Oliver–Pharr method underestimated the contact area due to the influence of the tilt condition. Consequently, it is necessary to compensate this dif...

In recent years, hydrophobic surfaces have attracted more and more attentions from many researchers. In this paper, we comprehensively discussed the effects of specific parameters of microstructures on the wetting properties by using the theoretical models, the effects of microstructures on two-dimensional anisotropic properties and the water dropl...

Although laser ablation is considered as a facile technique to fabricate bio-inspired super-hydrophobic surfaces, the issue is that the initial laser treated metallic surfaces show super-hydrophilic property. It will take a long period to reach super-hydrophobic state under ambient air. It is reported that these super-hydrophobic surfaces could be...

In recent years, the fabrication of hydrophobic and super-hydrophobic surfaces has been a hotspots in research field. In this study, we proposed a novel method by combining the laser ablation technology and chemical salinization process to obtain the hydrophobic and even the super-hydrophobic silicon surfaces. Three different types of patterns (lin...

To reduce the resistance and energy consumption of disc furrow openers, biomimetic coupling disc furrow openers (BCDFOs) that were inspired by digging animals (e.g., the convex hull of a dung beetle pronotum and the back-ridge scales of a pangolin) were designed as biomimetic coupling elements. The resistance of BCDFOs, analyzed by the discrete ele...

A one-step lithography method based on a superlens is proposed to fabricate diffraction-unlimited metallic patterns. By controlling the material parameters and the distribution of the impinging energy, various phenomena, such as periodic nanonetworks, ultrathin nanowires (sub-50-nm feature size), and variable-sized nanoparticles (ranging from sub-1...

Increasing usage of carbon fiber-reinforced polymer (CFRP) components in the airplane industry has led to higher demand in the machining quality of CFRP. In order to meet the quality requirements of final assembly, the signal monitoring of various processing parameters can be used to ensure the machining setup in perfect order. In the present work,...

Inspired by the famous “lotus effect”, we have fabricated the super-hydrophobic surfaces with nickel film on copper substrates using a one-step electrodeposition method. By adjusting processing time, water contact angle of as-prepared surfaces can reach as high as 160.3 ± 1.5° with small rolling angle of 3.0 ± 0.5°, showing excellent super-hydropho...

Atomic force microscopy (AFM) is a useful tool in nanoscale measurement. However, conventional AFM suffers from slow scan speed, limiting the use for biological detection or nanofabrication, due to the limited bandwidth of AFM components. In which the resonant frequency of the AFM scanner is usually too low to achieve high-speed scanning. In this p...

Atomic force microscopy (AFM) is a widely used tool in nano measurement and manipulation techniques. However, a traditional AFM system suffers from the limitation of slow scanning rate, due to the low dynamic performance of piezoelectric positioners. As an important part of AFM system, scanner will have a significant impact the result of the scanni...

A key hurdle to meet the needs of micro/nano manipulation in some complex cases is the inadequate workspace and flexibility of the operation ends. This paper presents a 6-degree of freedom (DOF) serial-parallel precision positioning system, which consists of two compact type 3-DOF parallel mechanisms. Each parallel mechanism is driven by three piez...

A novel multi-function stylus profiling system has been developed for characterizing surface properties at micro/nanometer scales. The multi-function stylus profiling system provides, within one set-up arrangement, measurements of topography, friction, Young’s modulus and hardness of a surface. The measurement is based on point-by-point scanning so...

Bacterial adhesion has become a significant problem in many industries causing billions of dollars for its complicated removal treatment and maintenance. In this study, metal surfaces undergone treatment with ultrafast laser with varies power. The microstructure produced on its original surfaces were expected to prevent the adhesion of Escherichia...

Nanoindentation technology has proven to be an effective method to investigate the viscoelastic properties of biological cells. The experimental data obtained by nanoindentation are frequently interpreted by Hertz contact model. However, in order to validate Hertz contact model, some studies assume that cells have infinite thickness which does not...

This paper presented ultrasonic embossing using metal molds to replicate microstructures on polyethylene terephthalate (PET) films. The metal molds used in this study were fabricated by laser ablation processing technology. Aluminum 6061 was adopted to be mold material because of its better machinability and the optimized laser processing parameter...

A XYθz stage is designed and experimentally tested. This developed stage is driven by three piezoelectric actuators (PZTs) and guided by a flexure hinge based mechanism with three symmetric T-shape hinges. It was manufactured monolithically by using wire electrical discharge machining technology. In addition, considering the both electrical and mec...

Based on the self-developed three dimensional micro/nano machining system, the effects of machining parameters and sample material on micro/nano machining are investigated. The micro/nano machining system is mainly composed of the probe system and micro/nano positioning stage. The former is applied to control the normal load and the latter is utili...

Cellular elasticity is frequently measured to investigate the biomechanical effects of drug treatment, diseases, and aging. In light of the cellular viscosity property exhibited by filament actin networks, this study investigates the viscoelasticity alterations of the human hepatocellular carcinoma (SMMC-7721) cell subjected to fullerenol treatment...

This paper presents the design and testing methodologies for a probe system used in a tip-based three dimensional micro/nano scratching machine. The probe system is one of the most important components of the scratching machine, including an electromagnetic device and a probe suspension mechanism. The electromagnetic device is used to generate elec...

This paper presents the design and test of a 6-degree-of-freedom(DOF) precision positioning system, which is assembled by two different 3-DOF precision positioning stages each driven by three piezoelectric actuators (PEAs). Based on the precision PEAs and flexure hinge mechanisms, high precision motion is obtained. The design methodology and kinema...

A comparison between the geometry of the helical milling specialized tool and conventional end mill was firstly introduced. Furthermore, a mathematical model, in which the cutting area was divided into different cutting zones, was established to simulate the cutting depths and volume of the different cutting edges (three kinds) on specialized tool....

This paper presents the design and test of a 6-degree-of-freedom(DOF) precision positioning system, which is assembled by two different 3-DOF precision positioning stages each driven by three piezoelectric actuators (PEAs). Based on the precision PEAs and flexure hinge mechanisms, high precision motion is obtained. The design methodology and kinema...

Topographic and wetting properties of Inconel 718 (IN718) surfaces were modified via nanosecond laser treatment. In order to investigate surface wetting behavior without additional post treatment, three kinds of microstructures were created on IN718 surfaces, including line pattern, grid pattern and spot pattern. From the viewpoint of surface morph...

This paper presents the theoretical modeling and numerical simulation of the probe tip based nanochannel scratching. According to the scratching depth, the probe tip is modeled as a spherical capped conical tip or a spherical capped regular three side pyramid tip to calculate the normal force needed for the nanochannel scratching. In order to furth...

This paper proposes a novel 3-DOF suspension mechanism for multi-function stylus profiling systems. Incorporating an electromagnetic force actuator, the 3-DOF suspension mechanism provides a controlled loading force. For reasons of the thermal and mechanical stability, a triangular flexure structure is utilized to support the stylus. The stiffness...

In order to understand the influence of picosecond laser parameter variation on laser-induced changes of titanium, the sheet surfaces of titanium were irradiated by picosecond laser pulses with different average laser power in this work. Then X-ray photoelectron spectroscopy (XPS) and transmission electron microscope (TEM) were used to analyze the...

Elastic properties of carcinoma cells are frequently measured from which malignant cells could be distinguished from their benign counterparts. However, the viscoelastic properties of cancerous cells do not receive their deserved attention since biological cells are more or less viscous. In this regard, the goal of this study is to explore, verify...

In this study, we presented an investigation of mechanical properties by AFM nanoindentation on human hepatocellular carcinoma cells treated with fullerenol for 24, 48 and 72 h. AFM nanoindentation was routinely applied to investigate the morphology and biomechanical properties of living carcinoma cells, and adhesion phenomena (negative force) were...

Bovine horns are durable that they can withstand an extreme loading force which with special structures and mechanical properties. In this study, the authors apply quasi-static nanoindentation and modulus mapping techniques to research the nanomechanical properties of bovine horn in the transverse direction (TD) and longitudinal direction (LD). In...

Hertz contact theory has been widely used for the determination of cell elasticity based on AFM indentation experiments. In light of the adhesive contact between AFM tip and cell, this study applied Johnson-Kendall-Roberts (JKR) model to fit the indentation force-displacement (F-D) curves reported previously. A MIN6 cell has been modeled as first a...

In this study, we presented human hepatocellular carcinoma treated with fullerenol for 24, 48 and 72 hours. Atomic force microscope was routinely used to investigate the morphology and biomechanical properties of living carcinoma, and adhesion phenomenon (negative force) was detected in the obtained force-displacement curve. Conventionally, Hertz c...

This paper describes an investigation into a new design of friction test apparatus with an artificial fingertip. In order to mimic a human finger stroking on surfaces, this special friction apparatus consists of an artificial fingertip, a linear flexure mechanism and a reciprocal stage. The contact force and friction force are measured simultaneous...

Topographic and wetting properties of Ti-6Al-4V were modified by nanosecond laser irradiation. Three types of microstructures were created after the laser processing, the irradiated samples initially showed hydrophilic behavior, however, over time, these surfaces became hydrophobic with contact angles above 90°, and the maximum contact angle could...

Mimicking insect flights were used to design and develop new engineering materials. Although extensive research was done to study various aspects of flying insects. Because the detailed mechanics and underlying principles involved in insect flights remain largely unknown. A systematic study was carried on insect flights by using a combination of se...

A modified Prandtl–Ishlinskii (P–I) hysteresis model is developed to form the feedforward controller for a 3-DOF flexure-based mechanism. To improve the control accuracy of the P–I hysteresis model, a hybrid structure that includes backlash operators, dead-zone operators and a cubic polynomial function is proposed. Both the rate-dependent hysteresi...