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Rarefied Gas Flows in Microfluidic Systems

National Science Fund (NSF) – “Competition for financial support of basic research projects – 2025”

1) Administrative description (Art. 53(2))

  • Call title: Call for Funding Fundamental Scientific Research – 2025
  • Main scientific field: Mathematical Sciences and Informatics
  • Additional scientific fields: Physical Sciences; Engineering/Technical Sciences
  • Keywords: microfluidics; rarefied gas flows; MEMS
  • Type of research: Fundamental scientific research
  • Project: No. KP-06-N92/4; SUNI No. BG-175467353-2025-08-0132
  • Duration: 36 months (Stage 1: 18 months; Stage 2: 18 months)
  • Host organization: Institute of Mechanics – Bulgarian Academy of Sciences (IMech–BAS)
  • Partners: none
  • Principal Investigator (PI): Assoc. Prof. Kiril Stoyanov Shterev, PhD
  • Correspondence address: Acad. Georgi Bonchev Str., Bl. 4, 1113 Sofia, Bulgaria; e-mail: kshterev at imbm.bas.bg
  • Budget: 255,000 BGN (180,000 BGN core budget + 75,000 BGN equipment/intangibles)

Research team

  • Assoc. Prof. Kiril Stoyanov Shterev, PhD – Principal Investigator
  • Prof. Emil Samuil Manoach, PhD – team member
  • Chief Assist. Prof. Simona Nikolaeva Doneva, PhD – team member (postdoctoral researcher)
  • Assist. Prof. Pavel Hristov Venev – team member (early-career researcher)
  • PhD student Maria Ivanova Vilani – team member (PhD student, SENEI–BAS)
  • Physicist Asen Asenov Shulev – team member
  • Physicist Alexander Asenov Iliev – team member (student, Technical University of Munich – remote)

2) Abstract

In recent decades, Micro-Electro-Mechanical Systems (MEMS) have made significant advances. A major driving force behind their development is fundamental scientific research (both theoretical and experimental), which contributes to new knowledge and ideas related to the physical processes in MEMS.

Rarefied gas flows in MEMS can be highly non-equilibrium, with discontinuities caused by the discrete nature of molecular flows. In this project proposal, we intend to investigate a wide range of phenomena and processes in rarefied gases at the micro and nano levels, as well as their interaction with solid and elastic structures. We are the first in the world to use a molecular model (Direct Simulation Monte Carlo, DSMC) to simulate rarefied gas in Fluid Structure Interaction (FSI) between an elastic body and rarefied gas. In this project, we will continue our research in this direction. We will analyze the influence of various parameters in three-dimensional cases and compare the results with experimental data.

The main objective of the present project is to advance the understanding of three-dimensional rarefied gas flows in microfluidic systems and their associated phenomena. A further aim is to establish a clear correlation between theoretical and experimental investigations.

To achieve this main goal, the following objectives are necessary:

  • • Development of innovative three-dimensional hybrid mathematical models of the coupled interaction of rarefied gas flows in microfluidic systems with rigid and elastic elements.
  • • Design and prototyping of complex microfluidic systems with integrated elastic and/or rigid elements, with parameters closely matching the models.
  • • Construction of a comprehensive experimental setup for measuring processes in the prototyped complex microfluidic systems; in the case of integrated elastic elements, their displacements and oscillations will be measured.
  • • Processing of theoretical and experimental results, with their overlap being identified and analyzed.
  • • Investigation of nonlinear phenomena arising in microfluidic flows and their interaction with elastic obstacles.

For gas flow modeling, we will use both the molecular DSMC method and the continuum model. The elastic element will be modeled as a vibrating elastic beam or an elastic rectangular plate. In both cases, geometrically nonlinear versions of beam or plate theory will be used (Euler-Bernoulli or Timoshenko in the case of beams, and Kirchhoff or Reissner-Mindlin in the case of plates). The numerical implementation of the tasks in the project requires substantial computational resources, and therefore, they will be executed and calculated on the Hemus supercomputer and the cluster of the Institute of Mechanics - BAS.

In the experiments, we will apply similarity theory and study similar processes – a widely used approach in fluid mechanics. In this case, we will scale up the dimensions and slow down the microprocesses to observe and measure them with the available equipment.

Our available experimental laboratory infrastructure offers a significant range of modern methods and tools for prototyping and studying micro-objects and systems. These include additive methods of micro/nano-production (3D nano-printing), subtractive methods of micro-manufacturing (femtosecond laser micromachining), and confocal laser scanning and microscopy methods for micro-inspection, measurement, and analysis of micro-objects, systems, and materials. By combining the available methods, we have the ability to prototype, manipulate, modify, and inspect a wide range of micro-objects, structures, and systems.

The successful implementation of the project proposal will lend credibility and substantial scientific weight to the innovative theoretical approach we have proposed. We expect the results of the research to make a significant contribution to the development of microfluidic systems.

3) Expected results (Art. 90(2), item 1)

  • New/extended 3D algorithms and high-performance implementations for DSMC in complex geometries and for moving/deforming surfaces.
  • Original 3D results for the coupled interaction “rarefied gas – elastic element” and reference cases with rigid walls (microchannels/cavities).
  • Prototyping and an experimental setup for studying rarefied gas flows in microfluidic systems; theory–experiment comparison.
  • Planned scientific publications and presentations (see by stages).

4) Work plan and stages (brief)

The project is implemented in two 18-month stages, with work packages:

WP1 Project management;

WP2 Theoretical research on three-dimensional rarefied gas flows with solid and elastic elements;

WP3 Experimental studies on rarefied gas flows with solid andelastic elements;

WP4 Dissemination of results.

5) Achieved results by stages (Art. 90(2), item 2)

Stage 1 (months 1–18)

  • To be completed/updated during implementation.

Stage 2 (months 19–36)

  • To be completed/updated after acceptance of the Stage 1 report and the start of Stage 2.

6) Project publications

  1. No publications have been added so far.

Contact

Assoc. Prof. Kiril Stoyanov Shterev, PhD

Institute of Mechanics – BAS, Sofia 1113, Acad. G. Bonchev Str., Bl. 4

http://www.imbm.bas.bg/index.php/en_EN/kiril-stoyanov-shterev

E-mail: kshterev at imbm.bas.bg


Modified date:17-02-2026