Design and fabrication of a piezoelectrically driven microfluidic cell sorter
File(s)
Author(s)
Merdan, Hakan
Type
Thesis
Abstract
In this thesis, a new fabrication method for a polydimethylsiloxane (PDMS) microfluidic
cell sorter chip using piezoelectric actuators is presented. Suggested device performance
was simulated in COMSOL Multiphysics 5.4, and 2-dimensional (2D) hydrodynamic
focusing was investigated. The deflection forces applied by the PZT (lead zirconate
titanate) actuators on the main stream to sort the particles were defined in terms of
incoming side flows. An optimum velocity for these deflective flows to change the
trajectory of the particles moving with the main stream was established. As PZT actuators
are used as the source of the deflection force, the relationship between deflective flow
velocity and the displacement of the PZT discs was investigated.
In the fabrication of the proposed device, a deep reactive ion etched silicon wafer was
used for pattern transfer in the PDMS soft lithography process instead of commonly used
SU-8 mould in the literature. Piezoelectric ceramic (PZT) discs are recessed into the
PDMS layer and isolated from the actuation chambers by a thin PDMS membrane
(0.36 mm thick); this facilitates assembly of a leak-free device. The actuation chambers,
just under piezoelectric discs, have a low volume (9.42mm3 with 30μm height). With this
approach, a small dead volume has been achieved, and the volume of sheath flow
consumption is minimised. The design also facilitates insertion and removal of the PZT
discs since they are not glued but recessed. In the proposed device, air-filled cavities were
created near the fluid channels to minimise the acoustic interference by the PZT disc
vibrations.
Challenges of the suggested fabrication process, calibration of process recipes and
experimental results of the fabricated device are presented. The efficiency of a coil type
magnetic actuator, as an alternative to PZT actuators, is presented. Fabricated devices
were tested with 10 μm polystyrene beads and 6 μm fluorescent beads with a 488 nmwavelength laser diode excitation. Simulation results were verified experimentally and
2D hydrodynamic focusing and deflection results are given. The performance of the
membrane structure, which makes the device completely sealed and leak-free, allowing
easy insertion and removal of the actuators, was critically assessed. Improvements for thev
fabrication to make the device completely leak-free and integrated miniature detection
system are presented as future work.
cell sorter chip using piezoelectric actuators is presented. Suggested device performance
was simulated in COMSOL Multiphysics 5.4, and 2-dimensional (2D) hydrodynamic
focusing was investigated. The deflection forces applied by the PZT (lead zirconate
titanate) actuators on the main stream to sort the particles were defined in terms of
incoming side flows. An optimum velocity for these deflective flows to change the
trajectory of the particles moving with the main stream was established. As PZT actuators
are used as the source of the deflection force, the relationship between deflective flow
velocity and the displacement of the PZT discs was investigated.
In the fabrication of the proposed device, a deep reactive ion etched silicon wafer was
used for pattern transfer in the PDMS soft lithography process instead of commonly used
SU-8 mould in the literature. Piezoelectric ceramic (PZT) discs are recessed into the
PDMS layer and isolated from the actuation chambers by a thin PDMS membrane
(0.36 mm thick); this facilitates assembly of a leak-free device. The actuation chambers,
just under piezoelectric discs, have a low volume (9.42mm3 with 30μm height). With this
approach, a small dead volume has been achieved, and the volume of sheath flow
consumption is minimised. The design also facilitates insertion and removal of the PZT
discs since they are not glued but recessed. In the proposed device, air-filled cavities were
created near the fluid channels to minimise the acoustic interference by the PZT disc
vibrations.
Challenges of the suggested fabrication process, calibration of process recipes and
experimental results of the fabricated device are presented. The efficiency of a coil type
magnetic actuator, as an alternative to PZT actuators, is presented. Fabricated devices
were tested with 10 μm polystyrene beads and 6 μm fluorescent beads with a 488 nmwavelength laser diode excitation. Simulation results were verified experimentally and
2D hydrodynamic focusing and deflection results are given. The performance of the
membrane structure, which makes the device completely sealed and leak-free, allowing
easy insertion and removal of the actuators, was critically assessed. Improvements for thev
fabrication to make the device completely leak-free and integrated miniature detection
system are presented as future work.
Version
Open Access
Date Issued
2023-03
Date Awarded
2023-12
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Holmes, Andrew S.
Sponsor
Turkey. Millî Eğitim Bakanlığı
Publisher Department
Electrical and Electronic Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)