Finger Displacement Research Articles

Phase diagram of invasion patterns in «capillary number, wetting angle, disorder» coordinates: A lattice Boltzmann study

Pore space heterogeneity, numerically described by the disorder parameter, is a factor that strongly influences the displacement mechanics in porous media. This paper presents a systematic study of the simultaneous effects of capillary number, wetting angle, and pore space disorder on the invasion patterns of immiscible displacement: viscous and capillary fingering, compact displacement, and various crossover regimes. The results are based on lattice Boltzmann simulations performed on synthetic micromodels and natural X-ray computed tomography models of natural sandstones. This paper addresses two objectives. The first is to present for the first time a three-dimensional phase diagram in «capillary number, wetting angle, disorder» coordinates, which accurately indicates the regions of invasion patterns. The identification is based on a number of displacement characteristics, such as sweep efficiency map, fractal dimension, and the dynamics of the leading front movement. Based on the phase diagram, the critical wetting angles, which define the boundary of the viscous fingering, capillary fingering, and compact displacement regimes, shift towards imbibition with increasing disorder. A decrease in capillary number shifts the critical wetting angles for the viscous fingering and compact displacement modes towards drainage, and for the capillary fingering mode towards imbibition. The second goal is to identify the maximum effect of pore space disorder on sweep efficiency as a function of capillary number and wetting angle. It has been found that at high capillary numbers the disorder effect is independent of the wetting angle. A decrease in capillary number enhances the maximum disorder effect on sweep efficiency and it becomes strongly dependent on the wetting angle. With increased capillary forces the transition from deep imbibition and drainage regimes to the mode with neutral wettability greatly enhances the effect of disorder. The extremum point of wetting angle, at which the effect of disorder is maximum, shifts towards drainage with decreasing capillary number.

Paired nerve stimulation with selective compensation effect.

In this study we investigate the selective compensation of paired peripheral nerves in healthy humans, focusing on distinct axonal conduction velocities in different fibre types. Using paired associative stimulation (PAS) with adjustable parameters, we aimed to modulate and compensate for neuronal activity along the median nerve. Six healthy volunteers (3 male, 3 female, aged: 22-49) participated in the current study. We conducted 30 experiments with the following protocol. A pair of pulses with the following parameters were applied to each volunteer: amplitude, pulse width and inter-pulse delay was generated by the dual-core programmed microcontroller STM32H745xI/G while values were set by one-board computer Jetson Nano. The microcontroller provided a pair of pulses to the DAC that applied it to nerve stimulation sites via a stimulator. During experiments, we used the following ranges: (a) current amplitudes [0-20mA], (b) pulse width [250-500 μs] and (c) delays [50-250 μs]. As the measurement of the stimulation effectiveness, we used the finger's contraction angles. Our findings reveal a significant selective compensation (inhibitory) effect over the motor responses, demonstrated through variations in finger displacement angles. By optimizing individual parameters-pulse width, inter-pulse delay, and compensatory currents-we successfully induced motor response compensation effects. Notably, consistent compensatory effects were observed across all volunteers using a pulse width of (250 μs) and an inter-pulse delay of (50 μs). These results highlight PAS's potential for developing non-invasive neuromodulation devices. However, further research is required to evaluate its efficacy in individuals with spasticity and upper motor neuron deficits.

Characterization of dynamic interplay among different channels during immiscible displacement in porous media under different flow rates.

Although immiscible displacement in porous media has been extensively studied, a more comprehensive analysis of the underlying dynamic behaviors is still necessary. In this work, we conducted experimental and theoretical analyses on the dynamic interplay among channels during immiscible displacement under varying flow rates. In a rock-structured microfluidic chip, we observed typical displacement patterns, including viscous fingering and capillary fingering, and analyzed their frontiers and efficiencies. Interestingly, we discovered a novel 'V'-shaped recovery rate pattern, which differs from the monotonic curve considered in previous research. The recovery rate reaches its lowest point at an injection rate of 1 μL/min (42%), increasing to 55 and 65% at rates of 16 and 0.1 μL/min, respectively. This increase may attribute to all-directional displacement at lower rates and multi-fingering displacement at higher rates, contrasting with primary fingering displacement observed at intermediate rates. Furthermore, we developed a dual-tube model to investigate the dynamic mechanisms between adjacent channels during the displacement process. At high injection rates, an increase in low-viscosity fluid rapidly reduces overall average viscosity of the channels, accelerating displacement while hindering the displacement process in neighboring channels. Conversely, at low injection rates, increased capillary forces at pore-throat junctions delay breakthrough in one channel, promoting simultaneous displacement in parallel channels and ensuring stability. These findings significantly enhance our understanding of the interplay between viscous and capillary forces in porous media during displacement processes.

Influence of binder content on gas-water two-phase flow and displacement phase diagram in the gas diffusion layer of PEMFC: A pore network view

Understanding the gas-water flow dynamics in the gas diffusion layer (GDL) is one of the keys to improving the proton exchange membrane fuel cell's (PEMFC) overall performance and avoiding water flooding. Yet, the relationship between the two-phase flow and micro-scale GDL structures (including binder, PTFE, and fiber skeleton) is not well understood. In this study, three-dimensional GDL structures with different fractions of binder contents (φb=0%∼50%) and a fixed porosity of 75.6 % are confidently reconstructed based on high-resolution images from the confocal microscope, implying that the addition of binder will increase the number of large pores and cause a bimodal throat size distribution through morphology analysis. Thereafter, drainage simulations are performed under a wide range of capillary number (−9 < log Ca <0) and viscosity ratio (−3 < log M < 2) by the pore network model (PNM), which robustly predicts the displacement phase diagram of viscous fingering, capillary fingering, stable displacement, and transitional regime. In the viscous fingering and stable displacement regime, the nonwetting phase saturation (Snw) is nearly the same for different φb, implying the fluid invading pathway does not change much with the addition of binder. However, in the capillary fingering regime (refer to the actual operating conditions), Snw increases rapidly with φbat the breakthrough time and its transient value continues to increase until the steady state, which may be attributed to the increased fractions of pores above the capillary threshold attributed by the bimodal throat size distribution. In addition, the effective water permeability increases sharply with φb, whereas the gas permeability remains almost constant, which means such pore structure alteration by adding the binder is beneficial to water disposal in PEMFC. This research provides insights into delineating the effect of pore and throat size distribution alteration by adding binder on two-phase dynamics in GDL.

Dynamics of hydrogen storage in subsurface saline aquifers: A computational and experimental pore-scale displacement study

The catastrophic effects of climate change can be mitigated by transitioning to renewable energy sources such as wind, solar, and hydropower while utilizing hydrogen (H2) as an energy carrier. As renewable fuel sources are intermittent and location-specific, large-scale, long-term storage options for H2 must be explored with high necessity. Subsurface hydrogen storage in saline aquifers provides a vital scope to store H2 gas in available pore voids with minimal environmental risk. In this work, a highly heterogeneous porous micromodel was used to study the immiscible two-phase dynamics at high-temperature, high-pressure saline aquifer conditions using computational fluid dynamics (CFD) simulation based on volume of fluid (VOF) method. A set of microfluidic experiments were carried out under atmospheric conditions to validate the numerical model. The VOF model was observed to show good agreement with microfluidic experiments. An unstable displacement pattern with viscous fingering was observed during various flow conditions that captured high pressure (15 and 25 MPa) and temperature conditions (323 and 343 K). It was observed that fingering displacement of brine limits the storage spaces for hydrogen, which consequently follows the high permeable path. As a result, only 0.272 fraction of brine was invaded by the H2 at a temperature of 323 K and pressure of 15 MPa. A comparison between H2-brine and nitrogen (N2)-brine flow dynamics revealed a 46% less storage capacity of porous media for H2. Formations bearing high temperature (343 K) showed an 11.27% increase in H2 storage capacity, while pressure increase had negligible effect. At low capillary number (Ca), more snap-off effects resulted in higher trapping of H2 gas. This study aims to provide meaningful insights into the complexities of flow dynamics and displacement patterns that are crucial for optimizing hydrogen storage efficiency in saline aquifers and for potential ‘white’ hydrogen production.

Dynamic simulation of immiscible displacement in fractured porous media

Investigating immiscible displacement in fractured porous media is essential for understanding the two-phase flow behavior within pores and fractures. In this work, a three-dimensional pore-fracture network model was developed to address the influence of fracture on flow patterns and to characterize fracture-matrix crossflow under different flow conditions. Sensitivity studies at a wide range of viscosity ratios and capillary numbers underscored that fracture significantly influenced flow patterns in the capillary fingering zone. Fracture with an advantageous path effect in the displacement direction caused a shift in the boundary of capillary fingering zone toward an increase in capillary numbers. As fracture aperture decreased and aspect ratio increased, there was a discernible decline in the crossflow rate. When fracture aperture equaled average matrix throat diameter, fracture lose advantageous path effect in compact displacement zone but retained it in viscous fingering and capillary fingering zones. Distinct matrix-fracture crossflow development processes were observed in different zones: in cross zone, following displacement breakthrough, the crossflow underwent a “long-term” process to attain stability. Viscous fingering zone promptly achieved stability post-breakthrough, whereas both capillary fingering and compact displacement zones had already reached a stable state before breakthrough. Nonlinear variations in breakthrough saturation were observed in the cross zone between compact displacement and capillary fingering zones. The control process of immiscible displacement exhibited variability under different flow conditions: compact displacement zone was characterized by matrix dominance, viscous fingering zone was jointly controlled by matrix displacement and fracture-matrix crossflow, and capillary fingering zone was primarily governed by fracture-matrix crossflow. These findings enhance scholarly comprehension of immiscible displacement behavior in fractured porous media.

Numerical study on the characteristics of viscous fingering during the displacement process of non-Newtonian fluid.

This study uses numerical methods (ANSYS-Fluent) to investigate the viscous fingering of the displaced phase as a shear-thinning fluid in the classic three-dimensional Hele-Shaw cell. Comparing the behavior of fingerings with different properties on the upper and lower surfaces of a three-dimensional model, it was found that when the upper and lower surfaces are walls, under the combined action of moving contact lines and Saffman-Taylor instability, fingering splitting occurs at the tip, resulting in the appearance of two fingers at the interface. In addition, we have found that interfacial tension has a suppressive effect on short waves. As the interfacial tension increases, the velocity at the advancing tip decreases. Therefore, when the interface tension is 0, viscous fingering displacement reaches the farthest distance. We have also conducted research on the viscous fingering at different temperatures. The results indicate that increasing the temperature leads to a decrease in the viscosity of the displaced phase, making the flow more stable. As the temperature rises, the pressure gradient inside the flow path increases, pushing the viscous fingering further.

Dynamic monitoring of saturation profiles during two phase immiscible displacements in confined sand packs using time-domain analysis of the frequency domain electromagnetic sweeps

Water saturation 1D spatial profiles were monitored using real-time domain analysis of the measured frequency domain complex reflection coefficients of electromagnetic sweeps during oil and deionized water flood experiments at ambient conditions. Gravity and viscous induced fingering and piston-like displacement scenarios were explored. A patented coaxial transmission line core holder was designed to host saturated sand packs compressed in their axial and radial dimensions. An inverse chirp z-transform algorithm was used to convert the measured responses from frequency to time domain. An optimization routine was developed to convert the resulting time domain step responses to water saturation profiles at every pore volume fraction of fluids injected. Advancing and trailing fronts and their breakthrough times were detected. Darcy's flow analysis was performed to extract 1D pressure distribution spatial profiles and dynamic capillary pressure curves for 3 drainage floods. The oil ganglia flow and gravity fluid separation were detected in water floods.

THE MODULARITY OF THE FINGERS AS A SOURCE OF MORPHOLOGICAL VARIATIONS OF THE HUMAN HAND'S SHAPE DEPENDING ON SEX

According to the latest achievements in animal morphology and paleo-morphology, the phenomena of modularity and integration are quite closely interconnected, while morphological integration describes the extent to which various structural features are related to each other in the process of morphogenesis, while modularity reflects the rate of evolutionary transformation, which determines the degree of this conjugation. One of the classical objects of study of modularity and integration in morphology is regularly segmented skeletal structures, in particular, the hand. In humans, the hand is characterized mainly by the ratio of the lengths of the index and ring fingers, while their position and the value that determines the structure of the hand as a whole in the space of its shape has not yet been studied. In this paper, the influence of the modules of the fingers on the shape of the hand in the framework of their morphological integration was determined, which became the main goal of the study. The method of geometric morphometry of digital images of radiographs of the right hands of 100 people was used, on which the coordinates of 16 landmarks of the phalanges of the II-V fingers were determined, followed by a study of the shape, covariance and modularity. The results showed that changes in the shape of the hand are due to the position of the II-V fingers in space, with the ulnar type of the hand (2d&lt;4d) there is a displacement of the II-III fingers in space in the distal direction and IV-V fingers in the proximal direction, with the radial type of the hand (2d&gt;4d) reverse transformations in space are observed. The position of the second finger in space largely affects the shape of the hand as a whole. An analysis of the modularity of the fingers indicates a significant integration between them, compared with the integration of other modules of the hand. The high values of covariance revealed as a result of the study in pairwise comparison of the modules of the fingers and lower values of covariance in the multiple comparison between the modules of the hand indicate a different degree of local influence of morphogenetic factors on the structural features and shape of the hand in people of different sexes.

Representative elementary volumes for various characteristics of two-phase flows in porous media: A statistical approach

This article presents a systematic study of the influence of two-phase flowpatterns on the representative elementary volume for various displacement characteristics. This paper considers both drainage and imbibition regimes and related patterns such as compact displacement, viscous, and capillary fingering. As two-phase flow characteristics, the displacement efficiency and interfacial contact areas between the invaded fluid and the displaced fluid, as well as between the invaded fluid and solid particles, are considered. Not limited to displacement patterns, we study the effect of capillary number on the minimum REV size. The findings of this paper are based on numerical simulations performed in two-dimensional artificially created porous structures using the Monte-Carlo movement algorithm. The main conclusions are validated on 3D X-ray computed tomography images of natural sandstones. Two-phase immiscible displacement in a porous medium is modeled using the lattice Boltzmann equations with the multi-relaxation time collision operator in combination with the color-gradient method describing interfacial phenomena and wetting effects. Minimum REV sizes have been identified using statistical data collected from a large number of numerical simulations in two-dimensional samples. Coefficient of variation and average value of the investigated property have been used to identify REV. The results show that REV for two-phase flow in porous media depends on the displacement pattern. Minimum REV sizes for viscous fingering and compact displacement are close. The accuracy of predicting the displacement efficiency for viscous fingering and compact displacement modes is much higher than for capillary fingering. Minimum REV sizes for interfacial contacts are lower than for displacement efficiency.

Impact of wettability on immiscible displacement in water saturated thin porous media

The characterization of immiscible displacement processes at the pore scale is crucial in order to understand macroscopic behaviors of fluids for efficient use of multiphase transport in various applications. In this study, the impact of porous material wetting properties on gas invasion behavior at various gas injection rates was investigated for thin hydrophilic porous media. An experimentally validated two-phase computational fluid dynamics model was employed to simulate the dynamic fluid–fluid displacement process of oxygen gas injection into liquid water saturated thin porous media. A phase diagram was developed through a parametric characterization of the thin porous media in terms of the material hydrophobicity and gas flow rates. In addition to calculating the saturation of the invading gas, gas pressure variations were calculated and used to identify the locations of phase diagram boundaries. Non-wetting phase streamlines resolved at the microscale were visualized and presented as a novel indicator for identifying displacement regimes and phase diagram boundaries. It was observed that the crossover from the capillary fingering regime to the stable displacement regime occurred between contact angles of 60° and 80°. By increasing the gas injection rate, due to viscous instabilities, flow patterns transitioned from the capillary fingering and stable displacement regimes to viscous fingering regime.

Effect of Microscopic Pore Throat Structure on Displacement Characteristics of Lacustrine Low Permeability Sandstone: A Case Study of Chang 6 Reservoir in Wuqi Oilfield, Ordos Basin

Pore throat structure is the key factor affecting displacement efficiency in low permeability reservoirs. In this paper, the pore throat structure and displacement characteristics of Chang 6 low permeability sandstone reservoir in Wuqi area of Ordos Basin were studied by casting thin section analysis, scanning electron microscopy, XRD, high-pressure mercury injection, and microscopic displacement model of real sandstone test. The results show that the size and homogeneity of the pore throat structure deteriorate gradually from type I to type IV reservoir, and the corresponding displacement efficiency also decreases gradually. The type I reservoir is dominated by uniform displacement, and residual oil is dominated by oil film. Type II reservoir is dominated by mesh and finger displacement, while type III reservoir is dominated by finger displacement, and continuous remaining oil distribution is easy to be formed after water flooding. Pore throat size and homogeneity are important factors affecting oil displacement efficiency. The larger the pore throat size, the more homogeneous the structure, and the stronger the seepage capacity, the higher the oil displacement efficiency. With the increase of volume displacement multiple, the displacement efficiency growth rate of the type I reservoir changes little, while the displacement efficiency growth rate of the type II and type III reservoir decreases gradually. In actual production and development, reasonable control of pressure is the key to dependable production.

Hydrodynamics of gas-liquid displacement in porous media: Fingering pattern evolution at the breakthrough moment and the stable state

Gas-liquid displacement in porous media widely exists in many terrestrial/extraterrestrial subsurface resource extraction and utilization applications. The typical fingering displacement during gas invading has been well identified through extensive research efforts. Yet, the evolution of fingering structures after invading breakthrough is rarely reported. Herein, through a joint approach of experimental flow imaging and digital image processing, we investigated the gas-liquid fingering displacement in a porous-patterned microfluidic chip from the breakthrough moment until reaching the steady state. With a wide range of capillary number Ca and viscosity ratio M, we visualized the evolution of finger morphologies in different flow regimes including capillary fingering (CF), viscous fingering (VF), and crossover zone (CZ). Interestingly, we found that finger structures of CF regime remain the same after the breakthrough, whereas fingers of VF regime keep expanding until almost all the pore space is invaded and eventually reaches to steady state. Followed with experimental observations, a comparative quantification of fingering patterns was also conducted in terms of invasion velocity, phase saturation and fractal dimension. A dramatic increase of gas saturation, from 0.15 to 0.60 at the case of Log10Ca=-5.17 and Log10M=-2.78, is obtained in the VF regime when the steady state is reached, so is the fractal dimension (from 0.14 to 0.16, even higher than one of CF). The underlying mechanism of such fingering expansion in VF is further revealed from the time evolution of fingering after breakthrough. A previously unobserved fingering cycle, consisting of new finger forming, cap invading, breakthrough and finger vanishing, keeps repeating until the saturation reaches the maximum. We believe that these findings are of significance in evaluating extraction effectiveness, economic benefits and storage safety for subsurface applications.

Study on Micropore Throat Fluid Seepage Characteristics and Oil Displacement Efficiency in Tight Reservoir

In order to overcome the problems including complicated pore throat structure, changeable seepage characteristics, and difficulty to find seepage law in the tight reservoir, this study simulated the water flooding development process of oilfield reservoir, and the water flooding seepage experiment of real sandstone microscopic model was carried out in a laboratory. Thin slice identification, constant velocity mercury injection, physical property analysis, scanning electron microscope, and other test data were combined to study the reservoir microscopic water flooding characteristics. The relationships between physical properties, water displacement efficiency, displacement pressure, pore structure, wettability, and water injection ratio are discussed. The study showed that the tight reservoir fluids were uniform displacement and reticular displacement seepage that occurred more than finger-reticular displacement. Meanwhile, displacement types affected oil displacement efficiency. Specifically, the uniform displacement type displayed the highest oil displacement efficiency, whose average value was 62.15%. The lowest oil displacement efficiency was finger displacement type, which is 26.89%. Additionally, 79% of the residual oil was cluster and film, and the corner and isolated distribution are less; the change of permeability has a greater effect on oil displacement efficiency than porosity. With the increase of water injection ratio, the oil displacement efficiency was improved. The oil displacement efficiency increases greatly and tended to be smooth and stable, when the water injection increased by 3 PV. There is an exponential relationship between throat radius and oil displacement efficiency.

Effect of the infill density on the performance of a 3D-printed compliant finger

Recent advances in additive manufacturing and soft robotics have enabled the production of compliant fingers and grippers using 3D printing techniques. For instance, the fused deposition modeling (FDM) method allows users to print flexible filaments with pre-specified infill densities. In order to investigate the effect of the infill density on the performance of a 3D-printed compliant finger, this study performs experimental and numerical investigations in order to develop empirical equations for estimating the output force, the output displacement, and the input force corresponding to given values of the input displacement and infill density of the compliant finger. A commercially available thermoplastic elastomer (TPE) filament, Filastic™, manufactured by BotFeeder is used in this study. Prototypes of four compliant fingers with infill densities of 40%, 60%, 80%, and 100% are produced. A two-fingered gripper is also developed and the relationship between the infill density and the maximum payload is investigated. In addition, a finite element model taking into consideration the hyperelasticity of the TPE is developed to analyze the behavior of compliant fingers with different infill densities. The numerical results show good agreement with the experimental data and with the curves for the empirical equations.

Subsurface multiphase reactive flow in geologic CO2 storage: Key impact factors and characterization approaches

Subsurface multiphase reactive flow in geologic CO2 storage: Key impact factors and characterization approaches

Mechanisms of Friction Reduction in Longitudinal Ultrasonic Surface Haptic Devices With Non-Collinear Vibrations and Finger Displacement.

Friction reduction using ultrasonic longitudinal surface vibration can modify the user perception of the touched surface and induce the perception of textured materials. In the current paper, the mechanisms of friction reduction using longitudinal vibration are analyzed at different finger exploration velocities and directions over a plate. The development of a non-Coulombic adhesion theory based on experimental results is evaluated as a possible explanation for friction reduction with vibrations that are non-collinear with the finger displacement. Comparison with experimental data shows that the model adequately describes the reduction in friction, although it is less accurate for low finger velocities and depends on motion direction.

Wettability effect on the invasion patterns during immiscible displacement in heterogeneous porous media under dynamic conditions: A numerical study

This paper investigates the wettability effect on the characteristics of two-phase immiscible flows in porous media at different capillary numbers. This issue presents both applied results useful to engineering disciplines and explores the fundamentals of displacement mechanisms, especially in the mode of compact displacement. The main findings of this study are based on numerical flow simulations in a digital model of heterogeneous porous structure, for which the lattice Boltzmann equations are used in combination with the multi-relaxation time and color-gradient models. This work is one of the few which studies the wettability effect in porous structures with a random arrangement of particles. The influence of the contact angle and the capillary number is presented in the form of images of the fluid distribution at various contact angles and capillary numbers, which were associated with the phase-diagrams for displacement efficiency and fractal dimension, as well as fluid-fluid interfacial length and finger width. It was found that increasing capillary number suppresses the wettability effect on displacement characteristics. This article first identifies four crossover zones between capillary and viscous fingering and compact displacement. It was shown that the critical contact angle, which determines the appearance of compact displacement, increases with the capillary number. Particular attention is paid to the displacement mechanisms for compact displacement. Analysis of the pressure signature at various contact angles and capillary numbers clarifies the role of touches and overlaps that stabilize interfacial front during compact displacement and determines the real driving force for this invasion pattern. This article is the first to establish a relationship between pore-filling events and fluctuations in the pressure signature during compact displacement. It was found that an increase in the pressure signature is characterized by a uniform displacement of all menisci along with the entire fluid-fluid interface, while invasion with a sharp decrease in pressure is determined by the burst-like displacement of a concave meniscus in narrowly localized areas of the pore space.

Inertia Effects in the Dynamics of Viscous Fingering of Miscible Fluids in Porous Media: Circular Hele-Shaw Cell Configuration

We present a numerical study of viscous fingering occurring during the displacement of a high viscosity fluid by low viscosity fluid in a circular Hele-Shaw cell. This study assumes that the fluids are miscible and considers the effects of inertial forces on fingering morphology, mixing, and displacement efficiency. This study shows that inertia has stabilizing effects on the fingering instability and improves the displacement efficiency at a high log-mobility-viscosity ratio between displacing and displaced fluids. Under certain conditions, inertia slightly reduces the finger-split phenomenon and the mixing between the two fluids.

Accurate recognition of object contour based on flexible piezoelectric and piezoresistive dual mode strain sensors

The application of flexible wearable sensors in the grasping process of robot hand can recognize the contour, soft and hard, material, surface temperature and other information of the grasping object, which can effectively improve the intelligent level of the robot. In this work, a method of object contour recognition is proposed by combining the flexible PVDF polymer piezoelectric sensor and high conductivity hydrogel piezoresistive sensor aiming at the problem of profile recognition for objects of the same or similar material. The response of flexible piezoresistive sensor to the static strain is used to sense the angular displacement of robot fingers, and then the shape and size of the object is recognized indirectly. At the same time, the flexible piezoelectric sensor is used as the fingertip tactile sensor to reflect the surface morphology of the object through the dynamic strain information when touching the object. In the whole process of grasping the object, the dual-mode strain information is fully used to realize the recognition of the shape, size and surface morphology of the object. Combining these information, the accurate recognition of the object contour can be further realized. In the experiments, six objects with different shape and four objects with different surface morphology are recognized to verify the feasibility of piezoresistive sensors and piezoelectric sensors respectively. In a comprehensive experiment, eight objects made of the same rubber material with different shape, size and surface morphology are recognized, and the average recognition rate is about 84%, which shows good classification advantages for the objects with similar shape, size and material.