“Microfluidics e Microactuators” Laboratory

Coordinator: Vladimir Viktorov

Objectives:

Aims of this laboratory is to study microfluidic devices, microfluidic systems and microactuators. In particular, the activities of the laboratory consist of the study of fluid mechanics at the microscale, of the design of various microfluidic devices and microfluidic systems and of their integration with opto electronic systems. Using SMA and PLZ materials, some microactuators are also studied and designed.

Some projects:

  1. Study of fluid dynamic phenomena in microfluidics
    • CFD numerical analysis and analytical modelling of microfluidic devices and systems
  2. Study and design of micromixers and microdroplets generators
    • Static micromixers
    • Batch active micromixers
    • Microdroplets generator
  3. Study and design of small oscillators and fluidic flowmeters
    • Feedback oscillator microflowmeters
    • Mini oscillators and jet flowmeters
  4. Optopneumatic systems
    • Optopneumatic interface
  5. Shape memory alloy devices (SMA)
    • Three fingered hand with virtual hinges
    • SMA actuated flexible finger
  6. PLZT materials devicesis
    • Displacement amplifier controlled with PLZT actuator

1 - Study of fluid dynamic phenomena in microfluidics

Vladimir Viktorov, Carmen Visconte

Fluid dynamic effects inside the basic elements of a microdevice, i.e. microchannels and microchambers, are studied by using CFD numerical models. Numerical CFD models of microfluidic devices (microflometers, micromixers, microfocusing devices) are also developed; results are validated by experimental tests.

Examples:

Rectangular ducts with different depth/width ratio(h/w)

Entrance length to reach fully developed laminar flow

Maximum/mean velocities ratio in case of flux with Knudsen number Kn<10-3 

and Mach numberMa<0,18

Martinelli M., Viktorov V., “Modelling of laminar flow in the inlet section of rectangular microchannels”. In: J. Micromech. Microeng, 19 (2009) 025013 (9pp)

 

2 - Study and design of micromixers and microdroplets generators

Vladimir Viktorov, Carmen Visconte

Static micromixers

Test bench  

H mixer

Nimafar M., Viktorov V., Martinelli M., “Experimental comparative mixing performance of passive micromixers with H-shaped sub-channels", Chemical Eng. Sci.. 76, (2012) 37-44

Chain, Tear-drop e H-C mixer

 Viktorov Vladimir, Mahmud Md Readul, Visconte Carmen, “Design and characterization of a new H-C passive micromixer up to Reynolds number 100”,Chemical Engineering Research and Design, 108, (2016), pp. 152-163.

Y-Y mixer

 

Viktorov Vladimir, Visconte Carmen, Mahmud Md Readul, “Analysis of a Novel Y-Y Micromixer for Mixing at a Wide Range of Reynolds Numbers”, JOURNAL OF FLUIDS ENGINEERING, 138:9, (2016).

Batch active micromixers

Active minimixers are used to mix small amounts of two or more fluids. Typical applications are batch mixing processes used in chemical, pharmaceutical, biomedical and food industry.

The minimixers designed at DIMEAS are made up of a piezoelectric lamina 2 that causes a silicone membrane 5 to vibrate.  The fluid to be mixed stays inside a mixing chamber 7, faced to the silicone membrane. 

The silicone membrane’s vibrating modes can be modified varying the pressure of the liquid placed inside the “driving chamber”, i.e the volume between the membrane itself and the piezoelectric lamina; as a consequence, fluxes inside the mixing chamber can be modified, so to optimize the mixing process.

  1. Piezoelectric membrane’s framework
  2. Piezoelectric membrane
  3. Feeding holes for the “driving chamber”
  4. Silicone membrane’s framework
  5. Silicone membrane
  6. Mixing chamber’s framework
  7. Mixing chamber
  8. Inlets for fluids to be mixed
  9. Mixture output
  10. Window for fluid visualization 

Air in Silicone Oil:

Water in Silicon Oil:

3 - Studio e realizzazione di mini oscillatori e flussimetri fluidici

Microdroplets generators

Vladimir Viktorov, Carmen Visconte, Md Readul Mahmud

Microdroplets generators are microfluidic devices applied in many chemical, pharmaceutical, biological and food processes, for the novel technologies of microencapsulation and emulsion production. They are the basic components of microfluidic systems based on microdroplets.

Examples of applications are: food gasification and emulsification, wine clarification by fottation, wine micro-oxigenation.

Novel microdroplets generators, both based on the microfocusing working principle and on the static mixers operation, have been studied and designed.

Microfocusing

3 - Study and design of small oscillators and fluidic flowmeters

Vladimir Viktorov, Carmen Visconte

Mini feedback oscillator flowmeter

Martinelli M., Viktorov V. “A mini fluidic oscillating flowmeter”. In: Flow Measurement and Instrumentation, vol. 22, (2011) p.37-543.

Mini oscillators and jet flowmeters
 
With two jets                     With three jets

4 -Optopneumatic systems

Gabriella Eula, Terenziano Raparelli, Vladimir Viktorov

Optopneumatic Interface

Using an optodetector and laminar microfluidic amplifiers connected in cascade an optopneumatic interface controlled by infrared light and visible light has been realized.

The optical signal (of 5mW) is generated by an remote LED and via fiber optic carried up to the optodetector. The interface output pneumatic signal is able to control a pneumatic valve. all’optodetector.

Belforte G; Eula G; Martinelli M; Raparelli T; Viktorov V., “Optimization of an optopneumatic interface”.In: MECHATRONICS, vol. 15, Issue 3, (2005), pp. 359-369.

5 -Shape memory alloy devices (SMA)

Daniela Maffiodo, Terenziano Raparelli

Three fingered hand with virtual hinges

Having small overall dimensions (fingers of about 30 X 30 mm) to grasp and carry little objects with cylindrical symmetry (e.g. test tubes).

Actuated by SMA wires, developing small displacements but higher forces than other actuators

SMA actuated flexible finger

 A module has cylindrical shape and small dimensions (diameter of 16 mm, length of 40 mm), with three SMA wires. The body has a central rod and four coaxial discs with holes for the SMA wires, placed at 120°. The shortening of a SMA wire causes the flexion of the whole module.

Maffiodo, D., Raparelli, T., “Three-fingered gripper with flexure hinges actuated by shape memory alloy wires”, International Journal of Automation Technology, 11 (3), (2017), pp. 355-360.

Maffiodo, D., Raparelli, T., “Design and realization of a flexible finger actuated by shape memory alloy (SMA) ires”, International Journal of Applied Engineering Research, 12 (24), (2017), pp. 15635-15643.

6. PLZT materials devices

Federico Colombo, Gabriella Eula; Carlo Ferraresi

Displacement amplifier controlled with PLZT actuator

There are PLZT materials able to be deformed, or stretched or flexed, under ultraviolet radiation, thanks to the combined action of piezoelectric and photovoltaic.
A displacement amplifier with a PLZT actuator and virtual hinges is realized.