Optically Induced Dielectrophoresis (ODEP) has been widely used in biomedical applications such as cell sorting and cell capture because of its operational flexibility and low cellular damage. However, existing automated ODEP methods often lack effective control of non-target cells, which may reduce manipulation performance in multicellular environments. To address this problem, this study proposes an automated cell manipulation method integrating ODEP, image processing, static optical traps and the A-star algorithm. Cells are first identified and localized from microscopic images. Non-target cells are then constrained by static optical traps and treated as static obstacles during path planning. Based on the detected cell positions, obstacle avoiding paths are generated and converted into executable optical patterns. Experiments were performed using yeast cells under a frequency of 1 kHz, a voltage of 2 V, and a light spot velocity of 5 μm/s. The results showed that the target cells followed the planned obstacle-avoiding paths and reached the designated destinations, while the non-target cells remained confined within their corresponding static optical-trap regions. The success rates of repeated single-cell directed transport and two-cell convergence experiments were approximately 90

Determining the monomolecular structure of lectins, such as concanavalin A (Con A), is crucial for understanding immune recognition mechanisms. However, most current studies focus on the cellular effects of Con A, leaving a gap in the understanding of its individual protein structure. This study uses tapping-mode atomic force microscopy (AFM) to directly visualize individual Con A proteins on mica surfaces. This approach overcomes the limitations of previous cellular-level studies and provides a new method to explore protein substructures at the single-molecule level. We also investigate how varying concentrations of Ni2+ (5 mM to 50 mM) influence the surface roughness and protein morphology. Results show that increasing the Ni2+ concentration leads to higher roughness and changes in the arrangement of Con A proteins. At 50 mM Ni2+, Con A proteins adopt four orientations: tiled, inverted triangular pyramid, vertical, and upright triangular pyramid. In contrast, at 5 mM Ni2+, the proteins are primarily arranged in two orientations: tiled and vertical. This work provides an AFM-based imaging method that enables the visualization of individual Con A proteins, offering insights into protein-surface interactions and its applications in protein-based assays.

This study proposes a size-based yeast cells sorting method utilizing optically induced dielectrophoresis (ODEP) virtual channel. By dynamically modulating light patterns ($3 \text{kHz}, 3 ~\mathrm{V}$) and leveraging the differences in dielectrophoretic forces experienced by cells of varying sizes, non-contact virtual channels were constructed on-chip to achieve label-free and precise yeast cells sorting. Experimental results demonstrated that larger cells (average equivalent spherical diameter, ESD $8.45 \mu ~\mathrm{m}$) experienced stronger dielectrophoretic forces. After being captured by the light patterns, they were able to move following the displacement of the light patterns. In contrast, smaller cells (ESD $6.72 \mu ~\mathrm{m}$) experienced weaker dielectrophoretic forces. After being captured by the light patterns, their movement speed lagged behind the moving speed of the light patterns. Ultimately, the differing dielectrophoretic forces resulted in the gradual separation of cells by size. Compared to traditional physical channels or fluorescence labeling methods, this approach avoids chemical damage and allows real-time adjustment of channel parameters. The study confirms the high sensitivity and reliability of ODEP virtual channel technology in eukaryotic microorganism sorting, providing a versatile platform for single-cell analysis.

Liver cancer is prevalent with the third highest mortality rate globally. The biomechanical properties of cancer cells play a crucial role in their proliferation and differentiation. Studying the morphological and mechanical properties of individual living cells can be helpful for early diagnosis of cancers. Herein, atomic force microscopy (AFM) was used to investigate the effects of Phellinus linteus on hepatocyte cells (HL-7702) and hepatocellular carcinoma cells (SMCC-7721) in terms of morphological and mechanical changes at the nanoscale. The water extract of Phellinus linteus (PLWE) resulted in increased height and surface roughness of SMCC-7721 cells. Also, the PLWE-treated showed that the average adhesion decreased by 1.69 nN and the average Young's modulus increased by 0.379 kPa. Additionally, the SMCC-7721 cells treated with PLWE showed clearly reduced activity compared with HL-7702 cells. This study suggested that Phellinus Linteus could be a potential candidate for selective anti-cancer therapy, providing a new avenue for the treatment of hepatocellular carcinoma.

The viscoelasticity of DNA molecules in the air were investigated using atomic force microscopy (AFM). For the individual DNA, compared to the randomly-coiled DNA, the stretched DNA showed smaller viscoelasticity, measured in the AFM quantitative imaging (QI) mode. The manipulation of DNA was performed, and it was influenced by its viscoelasticity. Compared to the stretched DNA, significant highlighted accumulations of DNA and lateral dragging tails were more obvious for the randomly-coiled DNA, which was caused by the elastic recoil and adhesion effects. In addition, the viscoelasticity of DNA aggregates composed of multiple DNA strands were measured. Compared to the individual DNA, they showed larger viscoelasticity. This study serves as a reference for the studies of DNA viscoelasticity-related behaviors in the air and has potential in gene knockout and targeted gene editing.

Facing the challenge of expensive photoresist and complex process flow for the fabrication of submicron structures based on laser interference lithography, we propose a low-cost fabrication method for submicron periodic structures with isooctyl acrylate by laser interference photocuring, which simplifies more processes and reduces costs. Results showed that the period of the grating structures is approximately 0.97 ± 0.01 µm, and the minimum feature size can reach 0.24 ± 0.02 µm. The period of the dot array is approximately 0.98 ± 0.01 µm for dx and 1.97 ± 0.01 µm for dy, and the minimum feature size is 0.64 ± 0.01 µm. In addition, we demonstrate the diffraction properties of the grating structures. In conclusion, we propose a new method for fabricating submicron grating structures with high efficiency and low cost.

The use of atomic force microscopy (AFM) for nanoscale surface characterization and mechanical property measurement has attracted considerable interest. At the level of single-molecule mechanical measurement, AFM is a powerful tool for both surface morphology analysis and mechanical assessment. However, its effectiveness is limited by dynamic displacement deviation during precise nanoscale positioning of surface target points, an essential factor in accurately determining surface mechanical properties. This study addresses this limitation by proposing an integrated enhanced A-star (A*) framework for contour-aware motion trajectory planning, ensuring nanometer-level target localization accuracy during AFM measurements on complex surface morphologies. The method employs AFM tip repositioning using prior topographic data and enables trajectory path planning on biological cell surfaces with both high and low topographical undulations. Experimental evaluations using Manhattan, Chebyshev, and Euclidean heuristic metrics in AFM grid modeling demonstrated that the Manhattan approach achieved a heuristic accuracy of 96% ± 4%, significantly outperforming Euclidean (70% ± 4%) and Chebyshev (56% ± 8%) methods (p < 0.001). In constrained environments, the Manhattan heuristic reduced target localization errors by 30% by alleviating path cost overestimation and resolved the long-standing trade-off between path smoothness (coefficient of variation, CV = 0.28) and positioning precision through adaptive cost-weighting mechanisms. The proposed approach supports precise nanoscale positioning necessary to capture ultramicroscopic topography and physical characteristics, providing a robust framework for quantitative nanomechanical characterization of heterogeneous materials.

As a flexible biomolecule, the spatial structure of DNA is variable. The effects of concentration, metal cations, and low pH on DNA morphology were studied. For the high concentration of DNA, the cross-linked branch-like or network structures were formed. For the low concentration of DNA, isolated, random and freely loose linear DNA chains were presented. These phenomena were related to the intermolecular interactions. Branch-like DNA structures were reformed with the addition of metal cations to the low concentration of DNA at pH 7-4, suggesting the negative charges of DNA were neutralized, thus transforming the spatial structure of DNA into a low charge density morphology and presenting the hypochromic effect. Compared to the monovalent alkaline metal cations, more negative charges of DNA were screened by the alkaline-earth metal cations. Distinct DNA morphologies were observed for pH 3. The linear and condensed DNA structures were simultaneously observed, which was met regardless of the solution with or without the addition of metal cations. This was further confirmed by the absorbance of DNA. Compared to the pure DNA, bulky and aggregated DNA collapsed structures were formed when the sodium and magnesium cations were added to the reaction solution. In addition, it was verified that the condensed DNA structures failed to revert back to the chain structure by neutralizing acidic solutions with alkali, but the compacted DNA spheres became loose. The conductivities of various DNA morphologies were measured. They were morphology-dependent. This study provides guidance for the behavior of DNA in the acidic solutions and further promotes the application of DNA in DNA-based nano-optoelectronic devices.

Mitochondria are emerging as potential targets for the cancer treatment. In this study, the effects of curcumin on the activity, migration, and mitochondrial membrane potential (MMP) of malignant hepatocytes (SMMC-7721 cells) were determined using cell viability, migration, and MMP assays. Changes in the morphology and biomechanics of SMMC-7721 cells and their mitochondria were studied using both optical microscopy and atomic force microscopy (AFM). The cell survival rate, migration and MMP depended on the concentration of curcumin. Optical microscopy studies showed that curcumin altered the cell morphology. AFM studies showed that the changes in the morphology and nanomechanics of SMMC-7721 cells and their mitochondria, were induced by curcumin. As the concentration of curcumin increased, the cell length, width, and adhesion decreased, but the height, roughness and Young's modulus increased. In contrast, the mitochondrial length, width, height and roughness increased, but the adhesion and Young's modulus decreased. There was a close relationship between mitochondria and cells in terms of function, morphology and biomechanics. This study shows the effects of curcumin on SMMC-7721 cells and their mitochondria from biology and biophysics perspectives. The findings aid in comprehensively understanding the interactions between mitochondria and malignant hepatocytes.

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, nanomechanical indentation experiments were conducted using an atomic force microscope (AFM). Multiple indentation methods were applied, and the indentation parameters were gradually varied to measure the viscoelasticity of normal liver cells and cancerous liver cells to create a database. This database was employed to train machine-learning algorithms in order to analyze the differences in the viscoelasticity of different types of cells and as well as to identify the optimal measurement methods and parameters. These findings indicated that the measurement speed significantly influenced viscoelasticity and that the classification difference between the two cell types was most evident at 5 mu m/s. In addition, the precision and the area under the receiver operating characteristic curve were comparatively analyzed for various widely employed machine-learning algorithms. Unlike previous studies, this research validated the effectiveness of measurement parameters and methods with the assistance of machine-learning algorithms. Furthermore, the results confirmed that the viscoelasticity obtained from the multiparameter indentation measurement could be effectively used for cell classification.Research Highlights This study aimed to analyze the viscoelasticity of liver cancer cells and liver cells. Different nano-indentation methods and parameters were used to measure the viscoelasticity of the two kinds of cells. The neural network algorithm was used to reverse analyze the dataset, and the methods and parameters for accurate classification and identification of cells are successfully found. The morphology of cells was obtained by atomic force microscopy, and the viscoelastic characteristics of cells were obtained by indentation experiments of relaxation and creep. image

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 characteristics can serve as important indicators of cell damage and cirrhosis. Atomic force microscopy (AFM) has been widely used to study cell surface mechanics. However, characterization of the deep mechanical properties inside liver cells remains an underdeveloped field. In this work, cell nanoindentation was combined with finite element analysis to simulate and analyze the mechanical responses of liver cells at different depths in vitro and their internal responses and stress diffusion distributions after being subjected to normal stress. The sensitivities of the visco-hyperelastic parameters of the finite element model to the effects of the peak force and equilibrium force were compared. The force curves of alcohol-damaged liver cells at different depths were measured and compared with those of undamaged liver cells. The inverse analysis method was used to simulate the finite element model in vitro. Changes in the parameters of the cell model after injury were explored and analyzed, and their potential for characterizing hepatocellular injury and related treatments was evaluated.Research Highlights This study aims to establish an in vitro hyperelastic model of liver cells and analyze the mechanical changes of cells in vitro. An analysis method combining finite element analysis model and nanoindentation was used to obtain the key parameters of the model. The multi-depth mechanical differences and internal structural changes of injured liver cells were analyzed. The algorithm is used to optimize the viscoelastic parameters of the model to minimize the error between the results of atomic force microscopy nanoindentation test and the results of finite element analysis. Through this optimization process, the optimal cell viscosity-hyperelastic parameters, which minimize the difference between them are obtained.image

In this work, an optically induced dielectrophoretic force field was used in manipulating deoxyribonucleic acid (DNA), and a DNA network was formed at the position of virtual electrode which was observed by atomic force microscope (AFM). The amorphous hydrogenated silicon (a-Si:H) film was used to structure the virtual electrodes when a beam of light from a projector was illuminated into it and the illuminated area became conductive. The mica was used as the substrate of DNA and placed between the two ITO electrodes. An AC electric field of 2 V peakto-peak at 50 kHz was used across the electrodes. The mica substrate with DNA solution was naturally air dry after functioned with the optically induced dielectrophoresis (ODEP) force and scanned by AFM. The results show that DNA was attracted by positive dielectrophoretic force and converged at the position of virtual electrode, and the overall shape and the specific position of DNA network on substrate could be controlled by changing the virtual electrode shape and position. The average height of the DNA networks was close to the real height of DNA, which was helpful for analyzing the DNA network electrical conductivity. This work has proven that the ODEP can be used as the tool to manipulate DNA and structure DNA molecular devices.

Calceolarioside A is a phenylethyl glycoside compound, originally isolated from the bark of Fraxinus mandshurica Rupr. In this work, the protective effect of Calceolarioside A on beta Amyloid protein induced toxicity in SH-SY5Y cells was studied. DPPH experiment, MTT assay, SEM, Atomic force microscopy and Colony formation were used to study the activity of Calceolarioside A. The results in this article show that the survival rate of the cells with Calceolarioside A (20-40 mg/mL) was significantly higher than that of the model cells without Calceolarioside A. Calceolarioside A could protect SH-SY5Y cells by improving some parameters in cells, such as the cell height, Young's modulus, adhesion and branch. In summary, Calceolarioside A can reduce Aβ25-35 -induced damage in SH-SY5Y cells. It can be a potential medicine to treatment with AD.

Magnetic nanoparticles (MNPs) are often used as drug-carrying particles for targeted therapy of tumors. Studying their effects on cell activity and mechanical properties is of great significance for the targeted treatment of tumors. In this paper, we used a combination of atomic force microscopy (AFM) and fluorescent labeling to study the mechanical properties of cells after the endocytosis of MNPs. Colon cancer cells SW480 were selected to co-culture with MNPs with a particle size of 50 nm, and the cell viability was measured and systematically analyzed under different conditions. The results showed that the safe dose of MNPs to colon cancer cells SW480 was 50 µg/mL, and when the amount exceeded 50 µg/mL, the cell viability decreased significantly. Increase the concentration of MNPs step by step within the safe dose of 0-50 µg/mL. Through the analysis of a large number of data measured by AFM, the results show that the mechanical properties of cells change significantly with the increase of MNPs concentration. In this paper, the experimental results are analyzed by comparing concentration gradients. The concentrations are set to 0, 30, and 50 µg/mL , respectively, to verify the influence of MNPs on the mechanical properties of cells.

Cell viability detection plays a crucial role in apoptosis and anticancer drug research.

The physical properties of tumor-derived exosomes have gained much attention because they are helpful to better understand the exosomes in biomedicine. In this study, the conductive atomic force microscopy (C-AFM) was employed to perform the electrical characterizations of exosomes, and it obtained the topography and current images of samples simultaneously. The exosomes were absorbed onto the mica substrates coated with a gold film of 20 nm thick for obtaining the current images of samples by C-AFM in air. The results showed that the single exosomes had the weak conductivity. Furthermore, the currents on exosomes were measured at different bias voltages and pH conditions. It illustrated that the conductivity of exosomes was affected by external factors such as bias voltages and solutions with different pH values. In addition, the electrical responses of low and high metastatic potential cell-derived exosomes were also compared under different voltages and pH conditions. This work is important for better understanding the physical properties of tumor-derived exosomes and promoting the clinical applications of tumor-derived exosomes.

This paper presents laser interference induced dielectrophoresis (LIIDEP) for cell manipulation and three-dimensional array assembly. In this study, two-beam and three-beam interference systems were built to manipulate yeast cells in deionized water. The feature size of laser interference pattern can be adjusted to the microscale, which effectively improves the precision of operation. When the power of both laser beams was 60 μW, the effective voltage of sine wave was 6 V and the frequency was 10 kHz, the two-beam interference pattern manipulated the cells into a single-row array distribution. For three-beam interference, when all three laser beams had the power of 35 μW and the frequency of 10 kH, the voltage of 5 V enabled each light spot to control one cell, and 8 V enabled the most light spots to control multiple cells. When the cell concentration was as high as 2 x 107 cells/mL, the cells were assembled into a three-dimensional columnar array. It was found that the aberration of the image observed by CCD was significantly small, which improved the quality of cell observation. Compared to the optically-induced dielectrophoresis with a projector or a laser as the light source, LIIDEP has the advantages of high manipulation resolution, good contrast and large dielectrophoretic force. This study provides an effective way for high resolution three-dimensional array manipulation and assembly of a large number of living cells on the microscale in liquid environments.

The effects of buffer solution and concentration on atomic force microscope (AFM) imaging of DNA molecules were investigated. It was found that the buffer solution type and the DNA solution concentration affected the DNA topological conformations, and had distinct AFM imaging results. Moreover, DNA molecules diluted with the TE buffer under the DC electric field present stretching topological conformations. This study contributes to the understanding of formation factors of various DNA topological conformations and further promotes the application of DNA in nanotechnology and biology.

In recent years, the field of micro and nano technologies has witnessed rapid development. Atomic Force Microscope (AFM) has become one of the main scanning imaging tools in the field due to its characteristics such as extremely high resolution and not being limited by the surface conductivity of the sample. In this paper, a prediction model is proposed to establish the Scanner of the AFM by obtaining the Z-direction motion data of the Scanner from the scanned data of grating of rigid samples. The Radial Basis neural network prediction model is optimized by using Screening Particle Swarm Optimization (SPSO) using Python programming language. The results are combined with the standardized data to achieve the prediction from the Z-directional motion data of the Scanner.

The nanoprobe is a powerful tool in scanning probe microscopy (SPM) that is used to explore various fields of nanoscience. However, the tips can wear out very fast due to the low stability of conventional probes, especially after the measurement of high currents or lateral friction, which results in image distortion and test imprecision. Herein, a novel functional nanoprobe is presented using graphene sheets in a high-quality graphene solution wrapped round a plasma-treated conventional Pt-Ir coated nanoprobe, which shows highly stability and resistance to degradation, leading to a significantly increased lifetime. Furthermore, we show that the graphene-wrapped nanoprobes have the advantages of enhanced electrical conductivity and reduced tip-sample friction, compared with Pt-Ir coated nanoprobes. The simplicity and low cost of this method make it valuable to various functional graphene-wrapped nanoprobes and applications.