Stylianos Vasileios Kontomaris
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Stylianos Vasileios Kontomaris has a total of 54 co-authors. Here are the top co-authors by number of shared publications:
- Anna Malamou
School of Electrical and Computer Engineering, National Technical University of Athens, 9, Iroon Polytechniou St., 15780 Athens, Greece
63 shared publications - Andreas Stylianou
Cancer Mechanobiology and Applied Biophysics Group, School of Sciences, European University Cyprus, 2404 Nicosia, Cyprus
43 shared publications - Georgios Chliveros
Department of Engineering and Construction, Metropolitan College, Athens, Greece
11 shared publications - Ioannis Psychogios
Department of Engineering and Construction, Metropolitan College, 15125 Athens, Greece
11 shared publications - Gamal Mohamed Ismail
Department of Mathematics, Faculty of Science, Islamic University of Madinah, Madinah, Saudi Arabia
7 shared publications Dido Yova
Biomedical Optics and Applied Biophysics Laboratory, School of Electrical and Computer Engineering, National Technical University of Athens, Greece
6 shared publications
Latest Publications
- 1 November 2026
- Published by IOP Publishing in Engineering Research Express
- Vol. 8  (21) , 215525
Power-law and Chebyshev–Duffing–Helmholtz reformulations for the analytical approximation of nonlinear MEMS oscillations
This paper presents two complementary analytical surrogate formulations for the nonlinear dynamics of a magnetically actuated microelectromechanical system governed by an inverse-distance restoring force. Since the governing equation does not admit an exact analytical solution, two surrogate models are developed. The first reformulates the nonlinear restoring force using a power-law approximation, leading to closed-form expressions for the system response and oscillation period through energy-based analysis and special-function representations. The second employs a Chebyshev polynomial approximation, transforming the original equation into a cubic Duffing–Helmholtz oscillator that admits an exact solution in terms of Weierstrass elliptic functions. Both formulations are validated against direct numerical simulations of the original nonlinear equation and are further compared with a first-order Harmonic Balance method applied to the quadratic Taylor-reduced model, as well as with an existing analytical approximation reported in the literature. The results demonstrate that the proposed power-law approximation provides accurate analytical predictions, while the Chebyshev–Duffing–Helmholtz surrogate further improves the accuracy, particularly near the pull-in instability, outperforming classical analytical techniques in the moderately and strongly nonlinear regimes. The proposed analytical framework therefore provides two complementary surrogate formulations that balance analytical simplicity and approximation accuracy. The results suggest that, for the magnetic-MEMS system considered here, an analytically intractable nonlinear equation can be effectively transformed into analytically tractable surrogate models.
- 1 November 2026
- Published by IOP Publishing in Engineering Research Express
- Vol. 8  (21) , 215525
Power-law and Chebyshev–Duffing–Helmholtz reformulations for the analytical approximation of nonlinear MEMS oscillations
This paper presents two complementary analytical surrogate formulations for the nonlinear dynamics of a magnetically actuated microelectromechanical system governed by an inverse-distance restoring force. Since the governing equation does not admit an exact analytical solution, two surrogate models are developed. The first reformulates the nonlinear restoring force using a power-law approximation, leading to closed-form expressions for the system response and oscillation period through energy-based analysis and special-function representations. The second employs a Chebyshev polynomial approximation, transforming the original equation into a cubic Duffing–Helmholtz oscillator that admits an exact solution in terms of Weierstrass elliptic functions. Both formulations are validated against direct numerical simulations of the original nonlinear equation and are further compared with a first-order Harmonic Balance method applied to the quadratic Taylor-reduced model, as well as with an existing analytical approximation reported in the literature. The results demonstrate that the proposed power-law approximation provides accurate analytical predictions, while the Chebyshev–Duffing–Helmholtz surrogate further improves the accuracy, particularly near the pull-in instability, outperforming classical analytical techniques in the moderately and strongly nonlinear regimes. The proposed analytical framework therefore provides two complementary surrogate formulations that balance analytical simplicity and approximation accuracy. The results suggest that, for the magnetic-MEMS system considered here, an analytically intractable nonlinear equation can be effectively transformed into analytically tractable surrogate models.
- 6 October 2026
- Published by Springer Nature in Journal of Vibration Engineering & Technologies
- Vol. 14  (8) , 560
Nonlinear Dynamics of Forced and Damped Oscillators with Hertzian Contact Interaction
- 6 October 2026
- Published by Springer Nature in Journal of Vibration Engineering & Technologies
- Vol. 14  (8) , 560
Nonlinear Dynamics of Forced and Damped Oscillators with Hertzian Contact Interaction
- Open Access
- 23 September 2026
- Published by Elsevier in Materials & Design
- Vol. 271
A robust indentation framework for accurate Young’s modulus determination and uncertainty quantification in soft materials
- 23 September 2026
- Published by Elsevier in Materials & Design
- Vol. 271
Open AccessA robust indentation framework for accurate Young’s modulus determination and uncertainty quantification in soft materials
- Open Access
An Approximate Force–Indentation Equation for n-Sided Blunt Pyramidal Indenters
Accurate AFM nanoindentation analysis requires models that account for the rounded apex of real pyramidal indenters. Although exact force-indentation equations for n-sided blunt pyramids exist, their numerical complexity limits routine use. In this work, a simple closed-form analytical approximation is developed that directly relates force to indentation depth for blunt pyramidal indenters. The method employs first-order Maclaurin series expansions of the geometric terms and the generic indentation differential equation, yielding a closed-form second-degree polynomial expression that is readily implemented in AFM data analysis. Comparison with the exact solutions showed that the approximation error decreases with indentation depth and is governed by the pyramid geometry rather than the tip radius. Simulated and experimental AFM data confirmed accurate Young’s modulus estimation above a geometry-dependent validity threshold. For a four-sided blunt pyramidal indenter, the proposed criterion predicts minimum indentation depths ranging from approximately for θ = 15° to 2.4 for θ = 45° where is the tip radius and θ is the pyramid’s semi-included angle. Application of the model to simulated AFM datasets yielded Young’s modulus values between 18.5 and 19.8 kPa for a true modulus of 20 kPa, corresponding to errors below 8% in all examined cases. Furthermore, the closed-form equation provided very good agreement with AFM nanoindentation data obtained from human prostate cancer cells. It is also shown that the generic derived equation includes the case of a spheroconical indenter as a limiting case. Young’s modulus is obtained directly from the quadratic coefficient, eliminating the need for tip-radius calibration. In addition, the formulation is applicable to heterogeneous materials, providing an effective local modulus through the weighted mean value theorem for integrals. The approach offers a practical and computationally efficient alternative for AFM data processing, improving the robustness of modulus estimation for soft biological materials.Open AccessAn Approximate Force–Indentation Equation for n-Sided Blunt Pyramidal Indenters
Accurate AFM nanoindentation analysis requires models that account for the rounded apex of real pyramidal indenters. Although exact force-indentation equations for n-sided blunt pyramids exist, their numerical complexity limits routine use. In this work, a simple closed-form analytical approximation is developed that directly relates force to indentation depth for blunt pyramidal indenters. The method employs first-order Maclaurin series expansions of the geometric terms and the generic indentation differential equation, yielding a closed-form second-degree polynomial expression that is readily implemented in AFM data analysis. Comparison with the exact solutions showed that the approximation error decreases with indentation depth and is governed by the pyramid geometry rather than the tip radius. Simulated and experimental AFM data confirmed accurate Young’s modulus estimation above a geometry-dependent validity threshold. For a four-sided blunt pyramidal indenter, the proposed criterion predicts minimum indentation depths ranging from approximately for θ = 15° to 2.4 for θ = 45° where is the tip radius and θ is the pyramid’s semi-included angle. Application of the model to simulated AFM datasets yielded Young’s modulus values between 18.5 and 19.8 kPa for a true modulus of 20 kPa, corresponding to errors below 8% in all examined cases. Furthermore, the closed-form equation provided very good agreement with AFM nanoindentation data obtained from human prostate cancer cells. It is also shown that the generic derived equation includes the case of a spheroconical indenter as a limiting case. Young’s modulus is obtained directly from the quadratic coefficient, eliminating the need for tip-radius calibration. In addition, the formulation is applicable to heterogeneous materials, providing an effective local modulus through the weighted mean value theorem for integrals. The approach offers a practical and computationally efficient alternative for AFM data processing, improving the robustness of modulus estimation for soft biological materials. - Open Access
- 1 July 2026
- Published by Elsevier in Results in Engineering
- Vol. 32
A Novel Engineering-Based C¹ Piecewise Model for Wound-Healing Dynamics
- 1 July 2026
- Published by Elsevier in Results in Engineering
- Vol. 32
Open AccessA Novel Engineering-Based C¹ Piecewise Model for Wound-Healing Dynamics
- Open Access
- 1 June 2026
- Published by MDPI AG in Journal of Interdisciplinary Research Applied to Medicine
- Vol. 6  (2) , 10
Nonlinear Modeling and Perturbation Analysis of Cell Population Dynamics Under External Factors—A Pilot Study of Low-Level Red Laser Irradiation on Lung Cancer Cells
The development of precise quantitative metrics is essential for characterizing the response of biological systems to external perturbations, enabling a transition from qualitative observation to predictive modeling. In this context, mathematical frameworks can provide insight into the dynamic behavior of cell populations under external stimuli. In this study, a logistic-type growth model was employed to describe wound healing dynamics. A scratch assay protocol was applied to lung cancer cells, and a perturbation-based analytical framework was developed to quantify the influence of external factors. Novel metrics were introduced, including the percentage difference in wound closure at specific time points, the shift in inflection time, and the Average Difference in Wound Closure (ADWC). A pilot experimental study was conducted to evaluate the effect of Low-Level Laser Therapy (LLLT) on cell migration. The proposed model successfully captured the nonlinear dynamics of wound closure and enabled quantitative comparison between control and treated groups. The analysis demonstrated that LLLT enhances cellular activity, leading to a shift in the inflection time by approximately 7.6 h and an increase of 25.4% in wound closure at 24 h compared to the control group. The ADWC metric further confirmed a systematic difference in the overall healing dynamics between conditions. The presented perturbation-based framework provides a rigorous and interpretable tool for quantifying the effects of external stimuli on biological systems. These findings suggest a light-dependent modulation of tumor cell migration in an in vitro model, indicating that light exposure may influence cellular behavior under certain conditions. This observation may be relevant for clinical applications involving light, such as photodynamic therapy, particularly in cases of incomplete drug delivery.
- 1 June 2026
- Published by MDPI AG in Journal of Interdisciplinary Research Applied to Medicine
- Vol. 6  (2) , 10
Open AccessNonlinear Modeling and Perturbation Analysis of Cell Population Dynamics Under External Factors—A Pilot Study of Low-Level Red Laser Irradiation on Lung Cancer Cells
The development of precise quantitative metrics is essential for characterizing the response of biological systems to external perturbations, enabling a transition from qualitative observation to predictive modeling. In this context, mathematical frameworks can provide insight into the dynamic behavior of cell populations under external stimuli. In this study, a logistic-type growth model was employed to describe wound healing dynamics. A scratch assay protocol was applied to lung cancer cells, and a perturbation-based analytical framework was developed to quantify the influence of external factors. Novel metrics were introduced, including the percentage difference in wound closure at specific time points, the shift in inflection time, and the Average Difference in Wound Closure (ADWC). A pilot experimental study was conducted to evaluate the effect of Low-Level Laser Therapy (LLLT) on cell migration. The proposed model successfully captured the nonlinear dynamics of wound closure and enabled quantitative comparison between control and treated groups. The analysis demonstrated that LLLT enhances cellular activity, leading to a shift in the inflection time by approximately 7.6 h and an increase of 25.4% in wound closure at 24 h compared to the control group. The ADWC metric further confirmed a systematic difference in the overall healing dynamics between conditions. The presented perturbation-based framework provides a rigorous and interpretable tool for quantifying the effects of external stimuli on biological systems. These findings suggest a light-dependent modulation of tumor cell migration in an in vitro model, indicating that light exposure may influence cellular behavior under certain conditions. This observation may be relevant for clinical applications involving light, such as photodynamic therapy, particularly in cases of incomplete drug delivery.
- Open Access
- 10 February 2026
- Published by Elsevier in Journal of the Mechanical Behavior of Biomedical Materials
- Vol. 177, 107371
A review on the identification of the mechanical properties of soft tissues and tissue-mimicking phantoms
- 10 February 2026
- Published by Elsevier in Journal of the Mechanical Behavior of Biomedical Materials
- Vol. 177, 107371
Open AccessA review on the identification of the mechanical properties of soft tissues and tissue-mimicking phantoms
- Open Access
A Practical Approach for Determining Depth-Dependent Mechanical Properties of Soft Materials in AFM Indentation via Polynomial Fitting and a New Model for Cellular Mechanics
In most AFM nanoindentation experiments on soft biological samples, classical contact mechanics models, such as Hertz or Sneddon’s equations, are commonly employed to determine the Young’s modulus. However, biological materials are inherently heterogeneous, and their mechanical properties often depend on the indentation depth. In this work, we present a novel and simple approach to quantify how the apparent modulus varies with increasing indentation depth. The method is based on the general indentation equation for axisymmetric indenters combined with a straightforward polynomial fitting of the force–indentation data. The proposed approach offers significant advantages, as it greatly simplifies the fitting process without requiring any advanced algorithms, while maintaining high accuracy. In addition, it is shown that the depth-dependent mechanical properties of cells can be described by a simple law, , where is the limiting value of the apparent modulus at large indentations, and represents the depth-dependent contribution dominant at the initial stages of the indentation process. Here, is a positive stiffness coefficient, and is the indentation depth. This is a very important result, indicating that by using the pair of coefficients and , we can fully describe the mechanical properties of cells, capturing their depth-dependent mechanical behavior. Experiments on fibroblasts and H4 human glioma cells confirm the accuracy of this equation. The proposed methods provide an accessible and reliable framework for nanoscale mechanical characterization, offering insights into the depth-dependent elasticity of heterogeneous soft materials and revealing mechanical patterns in biological samples.Open AccessA Practical Approach for Determining Depth-Dependent Mechanical Properties of Soft Materials in AFM Indentation via Polynomial Fitting and a New Model for Cellular Mechanics
In most AFM nanoindentation experiments on soft biological samples, classical contact mechanics models, such as Hertz or Sneddon’s equations, are commonly employed to determine the Young’s modulus. However, biological materials are inherently heterogeneous, and their mechanical properties often depend on the indentation depth. In this work, we present a novel and simple approach to quantify how the apparent modulus varies with increasing indentation depth. The method is based on the general indentation equation for axisymmetric indenters combined with a straightforward polynomial fitting of the force–indentation data. The proposed approach offers significant advantages, as it greatly simplifies the fitting process without requiring any advanced algorithms, while maintaining high accuracy. In addition, it is shown that the depth-dependent mechanical properties of cells can be described by a simple law, , where is the limiting value of the apparent modulus at large indentations, and represents the depth-dependent contribution dominant at the initial stages of the indentation process. Here, is a positive stiffness coefficient, and is the indentation depth. This is a very important result, indicating that by using the pair of coefficients and , we can fully describe the mechanical properties of cells, capturing their depth-dependent mechanical behavior. Experiments on fibroblasts and H4 human glioma cells confirm the accuracy of this equation. The proposed methods provide an accessible and reliable framework for nanoscale mechanical characterization, offering insights into the depth-dependent elasticity of heterogeneous soft materials and revealing mechanical patterns in biological samples. - Open Access
- 13 January 2026
- Published by Elsevier in Next Nanotechnology
- Vol. 9
Mathematical modeling of tumor nanomechanical fingerprints: A weighted skew-normal distribution approach for cancer diagnosis and treatment monitoring
- 13 January 2026
- Published by Elsevier in Next Nanotechnology
- Vol. 9
Open AccessMathematical modeling of tumor nanomechanical fingerprints: A weighted skew-normal distribution approach for cancer diagnosis and treatment monitoring