Cell Deformability Studies for Clinical Diagnostics: Tests with Blood

Analogue Fluids using a Drop based Microfluidic Device

A. S. Moita

, C. Caldeira

, F. Jacinto

, R. Lima

2,3

, E. J. Vega

and A. L. N. Moreira

Center for Innovation, Technology and Policy Research, Instituto Superior Técnico, Universidade de Lisboa,

Av. Rovisco Pais, 1049-001, Lisboa, Portugal

CEFT, Faculdade de Engenharia da Universidade do Porto (FEUP), R. Dr. Roberto Frias, 4200-465, Porto, Portugal

Metrics, Mechanical Engineering Department, University of Minho, Campus de Azurém, 4800-058, Guimarães, Portugal

Área de Mecánica de Fluidos, Dpto. de Ingeniería Mecánica, Energética y de los Materiales, Escuela de Ingenierias

Industriales, Universidade de Extremadura, Campus Universitario, Av. de Elvas, s/n, 06006, Badajoz, Spain

rl@dem.uminho.pt, ejvega@unex.es

Keywords: Lab-on-a-chip, Droplet based Microfluidics, Clinical Diagnostics, Cell Deformability, Bioanalogue Fluid.

Abstract: The present paper addresses the final tests (concerning the transport section) of a microfluidic device to be

used in cancer diagnostics, based on the mechanical properties of the cells and particularly on deformability.

Following the previous work, which established the materials to be used, according to the wetting properties

and their influence on the dynamic response of the droplets (which are electrostatically actuated) this paper

presents the final simulations to optimize the thickness and material of the dielectric coating, always as a

function of the dynamic response of the droplets. Then, to avoid contamination issues, a number of analogue

fluids are proposed, in a new approach, which are characterized and tested in the second part of the work.

Regarding the characterization of these new fluids, preliminary results suggest a great potential of a

surfactant solution to be used as an analogue. The addition of the surfactant results in the formation of semi-

rigid particles with a size distribution and deformation characteristics compatible with those of the

biosamples to be studied. The surfactant solution also shows a swift response to electrostatic actuation.

1 INTRODUCTION

Lab-on-chip devices are pointed as strongly

effective tools to perform a number of complex

sample manipulation operations, biochemical

analysis and immunoassay tests (e.g. Takahashi et

al., 2004, Gossett et al., 2010, Shields et al., 2015,

Chim, 2015). Besides allowing a significant

reduction of the samples and of the reagents as well

as a better control of the reactions, due to the small

characteristic time and length scales, the

microfluidic devices offer a significant energy

reduction, are easy to use and portable. Furthermore,

errors and contamination issues are precluded, since

the manual handling is marginal (Lin et al., 2010).

Sample transport in continuous medium using

microchannels is probably the most common

microfluidic design, but addresses a number of

inconveniencies such as the need for auxiliary

systems, which are still very ineffective from the

energetic point of view, clogging, difficulties in

accessing the samples, among others (Geng et al.,

2017). In this context, droplet-based microfluidics is

considered by several authors as an effective

alternative (e.g. Pollack et al., 2011, Dance, 2017).

Droplet handling can be performed using different

kinds of external actuation, (e.g. Zeggari et al.,

2014) although electrowetting is amongst the most

popular and well grounded. However, although

theoretical background on electrowetting is already

well recognized, as revised for instance in Mugele

and Baret (2005) and more recently in Nelson et al.

(2012) the details required for an effective design

and assembly of the chips is scarcely reported in the

literature (e.g. Li et al., 2012). Hence, optimization

of the chip design requires a deep knowledge on the

wetting properties of the materials used (e.g. Chim,

2015, Vieira et al., 2017), as well as an accurate

description of biosamples fluid dynamics and respon-

se under external actuation (e.g. Moita et al., 2016).

Microfluidic devices are also suitable to take

advantage of particular properties of the biosamples,

towards the development of label free diagnostic

approaches. In this context, mechanical properties of

Moita, A., Caldeira, C., Jacinto, F., Lima, R., Vega, E. and Moreira, A.

Cell Deformability Studies for Clinical Diagnostics: Tests with Blood Analogue Fluids using a Drop based Microﬂuidic Device.

DOI: 10.5220/0007578100990107

In Proceedings of the 12th International Joint Conference on Biomedical Engineering Systems and Technologies (BIOSTEC 2019), pages 99-107

ISBN: 978-989-758-353-7

the cells and particularly their deformability are a

hallmark to identify several diseases, such as cancer.

Characterizing cancer cell deformation can provide

useful information on the process of metastasis,

particularly for large deformability regimes, which

are rarely described in the literature (Hu et al.,

2018). Furthermore, a few authors have drafted

preliminary correlations between the deformability

ratio of the cells and the stage of malignancy (e.g.

Tse et al., 2013). At the microscale, it is also

expected that droplet dynamics can be sensitive to

the rheological variations caused by different

degrees of cell stiffness/deformability, so droplet

dynamics could be eventually correlated with cell

stiffness for early stage cancer diagnostics (e.g.

Vieira et al., 2017).

Following our previous work (Jacinto et al.,

2018), the present paper focuses on the development

of a droplet based microfluidic system, intended to

be used in clinical diagnostics (lung cancer) based

on cell deformability and its possible correlation

with the fluid dynamics of the droplets used for the

sample handling. The paper is organized in two main

sections: the first summarizes the process of design

and optimization of the lab-on-chip device, whose

configuration (electrodes dimensioning and

positioning, materials and wetting properties) were

optimized based on the dynamic behavior

(spreading, contact diameter and velocity) of the

biosample droplets. Then, following an original

approach, a brief description is made on the

procedure which will be used to infer on a possible

correlation between the cells deformability and

different stages of malignancy, following the work

of Tse et al. (2013). It is worth mentioning that at

this stage of the work, analogue fluids are proposed

to be used in the preliminary assays, to overcome

contamination issues, among others. Within this

scope, different approaches are considered in the

present work, to devise the analogue fluids, namely,

using xanthan gum solutions and suspensions of

polymers and surfactants solved on water, giving

rise to small semi-rigid particles. The main physical

properties of the fluids are accessed and they are

characterized in terms of the resulting particle size

distribution, evaluated based on Laser Scanning

Fluorescence Confocal Microscopy. The size and

deformability of the resulting particles is then tested

to check on their feasibility to mimic cell

deformability in the context of the current main goal

of this work (malignancy diagnostics). The dynamic

response of the analogue fluids is also tested to

check on the feasibility of their handling in the

microfluidic device.

2 MATERIALS AND METHODS

2.1 Numerical Method

In our previous work, the materials used to assemble

the microfluidic device were carefully selected,

based on their wetting properties and on an intensive

analysis to minimize adsorption issues, which were

affecting sample handling, besides being an obvious

source of contamination (Vieira, et al., 2017, Moita

et al., 2018). A numerical approach was then

followed to predict the motion of the sample

microdroplets, optimizing the chip configuration to

promote droplet motion (Jacinto et al., 2018).

Following these steps, a final numerical optimization

was performed to check on the correct selection of

the dielectric materials which are used to coat the

electrodes. Their thickness is also optimized, to

maximize the resulting electrostatic force, the

distance travelled by the droplet and the velocity of

the moving droplets. These parameters were

optimized for the lowest possible applied voltage.

The numerical study was performed using

COMSOL Multiphysics 4.3b. The electrostatic forces

actuating on the droplets were determined using

Maxwell stress tensor, integrated on droplets’ surface.

Droplet motion was simulated using an

incompressible formulation of Navier-Stokes

equations for a laminar flow. Phase Field User

Interface was used to track the liquid-air interface.

The complete model formulation together with the

detailed description of the computational domain

and boundary conditions used can be found in

Jacinto et al. (2018).

2.2 Experimental Method

An experimental approach, as proposed in the

present work, was followed to characterize the

analogue fluids and check on their suitability to infer

on possible correlations between the deformability

of the cells and different stages of malignancy. The

analogue fluids were characterized in terms of their

main physico-chemical properties and on the size

distribution of the particles mimicking the cells, as

described in the following sub-sections. The

electrostatic response of the various analogue fluids

tested here was also inferred, using the experimental

arrangement detailed below.

2.2.1 Experimental Arrangement

The dynamic response of the analogue fluids

wasevaluated on a simplified arrangement. In this

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100

arrangement, a 25μm diameter tungsten wire

(Goodfellow Cambridge Ltd), acting as an electrode,

was dipped inside the droplet to be tested. The

counter electrode on which the droplet was

deposited was a copper cylinder with 19mm of

diameter and 20mm height. A 10μm Teflon film

(Goodfellow Cambridge Ltd) was used as the

dielectric layer. As recommended by Restolho et al.

(2009), a very thin film of sodium chloride was

placed between the counter electrode and the

dielectric to avoid the presence of an air gap. Both

electrodes were connected to a Sorensen DCR600-

.75B power supply and DC voltage was applied. The

tests were performed inside a Perspex chamber with

quartz windows to avoid optical distortion, under

continuously controlled temperature and relative

humidity conditions. The chamber was previously

saturated with the working fluid, for each fluid used.

Relative humidity measurements were taken at a

sample rate of 0.5Hz, with an accuracy of 2-5%.

Temperature measurements were taken also at a

sample rate of 0.5Hz, within ±0.5°C accuracy.

Measurements were performed using a DHT 22

Humidity & Temperature Sensor. The temperature

was observed to be constant within T=20±3ºC and

relative humidity was kept constant between 75%

and 78%. This entire set-up was directly mounted on

an optical tensiometer THETA, from Attention.

Using the sessile drop method, the equilibrium

contact angle (the angle formed in equilibrium,

between the surface line and a tangent line touching

droplet edge) was evaluated as a function of the

applied voltage, for a range between 0-230V in 25V

increments. The final curves presented and discussed

here were averaged from at least six assays, obtained

under similar conditions. Droplet volume was kept

constant and equal to 3μl.

The detailed description of the set-up (with the

appropriate schematics) and experimental procedu-

res which were used here to access the dynamic

response of the analogue fluids under electrostatic

actuation can be found in Moita et al. (2016).

2.2.2 Preparation of the Analogue Fluids

and Characterization of their

Physico-chemical Properties

Analogue fluids were prepared following three

different strategies, namely using xanthan gum,

using a suspension of polymeric particles in water

DD and mixing water DD with a small quantity of

surfactant which results in the formation of semi-

rigid surfactant particles.

The xanthan gum solutions were prepared with

the concentrations of 0.05wt% and 0.35wt%. As

these solutions have a shear thinning behaviour, the

viscosity vs shear rate curves were fitted using the

Cross model (Cross, 1965), following the procedure

described in Moita et al. (2015). Rheological data

were measured under controlled temperature

conditions, at ATS RheoSystems (a division of

CANNON® Instruments, Co). The accuracy of the

measurements is within ±5%. The suspensions with

polymeric particles were prepared with PMMA -

Poly(methyl methacrylate) dissolved in water DD

(1wt%). Different concentrations are expected to be

tested in the near future. Seeking at appropriate

characteristic spatial scales that could be used to

mimic the cells, different particle diameters were

tested here, namely 5μm, 10μm and 20μm. Finally,

the third approach consisted in adding a surfactant

Brij40 (a nonionic polyoxyethylene surfactant from

Thermo Fisher) which results in the formation of

semi-rigid micro-particles suspended in the water.

Surface tension

was measured using the

optical tensiometer (THETA from Attention). The

final surface tension values were averaged from 15

measurements taken under controlled temperature

conditions (20±3ºC). Measurements have standard

mean errors always lower than 0.35. Density

was

measured with a pycnometer for liquids and

concentrations were checked by basic concentration

calculations. The detailed description of the

measurement procedures can be found in Moita et

al. (2018). Table 1 summarizes the main physico-

chemical properties of the various fluids tested here.

It is worth mentioning that varying the diameters

of the PMMA particles did not produce any

significantly quantifiable modification in the density

or in the surface tension of the fluids tested here.

Table 1: Density and surface tension (measured at room

temperature 20±3ºC) of the analogue fluids tested in the

present work.

Solution Density

ρ [kg/m

]

Surface

tension

[mN/m]

Xanthan

gum

0.05wt%

997 72.0

Xanthan

gum

0.35wt%

997 72.95

Water DD

+ PMMA

particles

(1wt%)

999 58.65

Water DD

+ Brij40

999 21.10

Cell Deformability Studies for Clinical Diagnostics: Tests with Blood Analogue Fluids using a Drop based Microﬂuidic Device

101

2.2.3 Characterization of Particles Sizes and

Deformability using Laser Scanning

Fluorescent Confocal Microscopy

Analogue fluids were further characterized in terms

of the size distribution of their particles and of their

deformability capability (to mimic the various

degrees of cell deformability associated to the

different stages of malignancy). The analysis of the

size distribution was performed based on extensive

post-processing of images taken with a Laser

Scanning Confocal Microscope (SP8 from Leica),

using an in-house code developed in MATLAB. The

images were taken using Rhodamine B (Sigma

Aldrich) as fluorophore in a concentration of

3.968x10

-6

g/ml, which does not alter the physico-

chemical properties of the analogue fluids. A laser

with 552 nm wavelength, was used. The power of

the laser was set to 10.50 mW (3.00% of its

maximum power) and the gain of the

photomultiplier was fixed at 550V. These values

were chosen after a sensitivity analysis on the

contrast of the image (before the post-processing)

and on the Signal to Noise Ratio (SNR). The images

were recorded in the format 1024x1024pixels

and

the scanning frequency was set to 400 Hz. For the

optical arrangement used, the lateral and axial

resolutions for most of the measurements are R

0.375μm and R

= 1.4μm, while the optical slice

thickness was 2.2μm.

The deformability of the particles in the fluids

was assessed by using a 2D microfluidic device

(made of PDMS) composed of a microchannel with

a hyperbolic shaped contraction, measuring at the

end of this contraction (around the smallest cross-

section) and visualizing the particles with a high-

speed video microscopy system (high-speed camera

connected to an inverted microscope), as in Pinho

(2018).

3 RESULTS AND DISCUSSION

3.1 Design and Optimization of the

Microfluidic Device

In Vieira et al. (2017) and later in Moita et al.

(2018) a careful selection of the materials to

assemble the microfluidic device was performed,

addressing the wetting properties of the dielectric

coating. This analysis, which was performed as a

function of the dynamic response of the biofluid

droplet under electrostatic actuation revealed the

paramount role of the wetting properties of the

dielectric in allowing an efficient handling of the

biosamples. Hence, besides the hydrophobicity, the

reduced hysteresis to minimize energy dissipation at

the droplet surface contact line showed to be a factor

of major importance. Furthermore, minimizing

adsorption was also shown to be relevant, not only

to reduce contamination issues, but also to promote

droplet motion. Indeed, Moita et al. (2018) clearly

showed that the adsorption of the biocomponents

(e.g. proteins) could lead to a local increase of

the wettability, which would promote droplet

spreading and energy dissipation at the contact line,

thus limiting droplet continuous motion. In line with

this and combining the electrical properties with

the aforementioned wetting issues, Moita et al.

(2018) recommend the use of PDMS

(Polydimethylsiloxane) or Teflon coated with a

commercial compound called Glaco©, a

perfluoroalkyltrichlorosilane combined with

perfluoropolyether carboxylic acid and a fluorinated

solvent (Kato et al., 2008), to promote the

superhydrophobicity of the dielectric, while

reducing the adsorption of the biocomponents.

However, when designing the optimized

electrodes configuration, also as a function of the

dynamic response of the biosample droplets, Jacinto

et al. (2018) noticed that the negative effect of an

excessive increase of the thickness of the dielectric,

according to Young-Lippmann equation, would

reduce droplet motion, compromising the efficacy of

the microfluidic chip. It is worth mentioning that the

Young-Lippman equation states that the contact

angle of the droplet under electrostatic actuation is

proportional to the applied voltage and inversely

proportional to the thickness of the dielectric. The

detailed theoretical analysis on this and other basic

principles of electrowetting is revised in Mugele and

Baret (2005) and in Nelson and Kim (2012), for

instance.

In line with this, for the specified dielectrics, an

additional simulation was performed to optimize the

thickness of the dielectric, maximizing the resulting

electrostatic force, the distance travelled by the

droplet and its velocity. Hence, Figure 1 depicts the

numerical results on the maximum velocity of a

droplet while moving on the chip for a time interval

of 10ms, as a function of the thickness of the

dielectric, for a fixed imposed voltage of 90V.

Following the previous simulations (Jacinto et al.,

2018), the droplet is a biofluid (a solution of GFP –

Green Fluorescent Protein, produced and purified in

house, with 1.71x10

-3

mM concentration) with an

initial diameter of 1.3mm.

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102

Figure 1: Maximum droplet velocity, as a function of the

dielectric thickness, for different dielectric materials, and a

fixed imposed voltage of 90V. The GFP droplet with

1.71x10

-3

mM concentration has an initial diameter of

1.3mm.

The Figure clearly shows the maximization of

droplet velocity, for a fixed reduced value of the

imposed voltage, for a dielectric thickness of the

order of 1-6μm. For thicker values, the droplet

velocity becomes very low, as shown in the Figure

and eventually the motion of the droplet is totally

precluded. On the other hand, the thickness can be

further tuned and eventually reduced within the

nanometric scale, although in this case, the eventual

benefits arriving for droplet transport are probably

overcome by the difficulty and costs of the

manufacturing process. Furthermore, for sub-

micrometer thickness values, dielectric breakdown is

more likely to occur, leading to the occurrence of

droplet hydrolysis, which, besides destroying the

sample droplets, can cause substantial damages in

the microfluidic chip.

Based on these final simulations and following

the previous recommendations of Vieira et al.,

(2017), Moita et al. (2018) and Jacinto et al.

(2018), the final microfluidic chips should be

coated with Teflon with a thickness between 1 and

6μm, which allows an efficient droplet motion with

velocities up to 75mm/s, for a low applied voltage

(bellow 90V) and low frequencies (9Hz). A

simplified version of the device is schematically

represented in Figure 2.

Figure 2: Simplified schematic of the microfluidic chip.

Currently only the basic chips with the optimized

electrodes size and configuration are being fabricated.

3.2 Analysis of the Suitability of the

Analogue Fluids

The analogue fluids tested here are intended to

mimic the actual biofluids to be assayed, namely in

terms of the rheological properties, deformability

and size of the particles. Despite having a shear-

thinning behaviour, close to that of blood, the

xanthan gum solutions cannot mimic the potential

rheological modifications caused by cells

deformation. In this context the polymeric

suspensions provide a much more realistic approach.

However, looking at the particles distribution within

the fluid, with the confocal microscope, the images

show a strong trend for the PMMA particles to

agglomerate forming large rigid clusters, as

illustrated in Figure 3.

Figure 3: Illustrative image of the PMMA solution (with

particles of characteristic size of 5μm) taken with the

Laser Scanning Confocal Microscope (Leica SP8). The

images were taken with an objective with 20X

magnification and with a numerical aperture of 0.75.

Cell Deformability Studies for Clinical Diagnostics: Tests with Blood Analogue Fluids using a Drop based Microﬂuidic Device

103

For instance in the case illustrated in Figure 3,

the characteristic size of the resulting particles is

5.46±0.38μm, but the agglomerates can be larger

than 40μm. Also, the particles are approximately

spherical, but the resulting agglomerates can depict

quite irregular shapes.

On the other hand, the analogue fluid resulting

from the addition of the surfactant is much more

interesting in terms of the particles distribution,

showing no evident agglomeration of the particles

(Figure 4a), which also depict a spherical shape. The

particle size distribution (which was evaluated for a

sample of 170 particles) is slightly heterogeneous, as

Figure 4: a) Representative image of the analogue fluid

prepared with the surfactant Brij40, obtained by Laser

Scanning Fluorescent Confocal Microscopy (objective of

20x magnification and 0.75x numerical aperture). b) Size

distribution of the semi-rigid particles obtained by image

post-processing.

depicted in Figure 4b), but a simple filtering of the

solution seems to considerably narrow the size

distribution, homogenising the solution (Figure 5).

It is worth mentioning that having a particle size

distribution more heterogeneous is in fact an

advantage for the current study, since the pleural

fluid samples may have different cells, with different

morphologies, being the size distribution obtained

here, similar to that reported by Tse et al. (2013)

using pleural effusions.

The complete characterization of this kind of

solutions is out of the scope of the present study and

will be presented in a future work.

Figure 5: Representative image of the analogue fluid

prepared with the surfactant, obtained by Laser Scanning

Fluorescent Confocal Microscopy (objective of 20x

magnification and 0.75x numerical aperture) after filtering

the solution with a 10μm filter.

After this brief analysis of the particles

morphology and size distribution, it is now relevant

to briefly check on their deformability, as they

should be able to present similar stages of

deformability, comparable to those of the sample

cells. The deformation index DI, as initially defined

in Pinho et al. (2013):

DI =

major

- L

minor

major

+ L

minor

(1)

where, L

major

and L

minor

refer to major and minor

axis lengths of the cell was used to assess the

deformability of the particles.

The range of maximum DI obtained with

different particles is represented in Figure 6, which

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104

includes results gathered from the work of Pinho

(2018). The Figure shows a significant range of the

deformation index, up to 0.5, particularly for semi-

rigid particles, such as those obtained with the

surfactant solution. As reported by Pinho et al.

(2018) one may notice that the deformability of the

rigid particles such as PMMA is lower than that of

other analogues, including the semi-rigid particles

obtained with the surfactant solution. Although the

sizes of the particles used here are relatively narrow,

the analogue solution with the surfactant can provide

a wider range of particle diameters, as shown in

Figure 4b). The detailed study of the particles

deformability is out of the scope of the present work

and will be presented in a different work.

Figure 6: Deformation index DI as a function of the initial

(averaged) particles diameter for the particles used in

different analogue fluids.

The methodology used by Tse et al. (2013) for

malignant diagnostics is quite complex and requires

the establishment of different profiles, which are

mainly different distributions of the deformability

(which Tse et al., 2013 defined as the ration

major

minor

), which is represented as a function of

the initial diameter of the cells. Overall, considering

that cell diameters in Tse et al. (2013) were ranging

between 1 and 25μm, this range of diameters is

covered with our analogues, which show

deformability ranges of the order of 1.25 or higher.

This analysis must be adapted for our case study and

for the various strategies that will be used to deform

the cells, but these preliminary results suggest a

good potential of these analogue fluids, and

particularly the Brij40 solution to be used in our

deformability studies.

Finally, given that our microfluidic device works

under electrostatic actuation it is worth to analyse

the electrostatic response of the analogue fluids. In

this context Figure 7 depicts the variation of the

equilibrium contact angle under actuation, as a

function of the applied voltage. The measurements

were performed on a Teflon substrate, as described

in section 2.2.1.

Figure 7 shows a clear response of all the

analogue fluids tested here, under electrostatic

actuation, as the contact angle decreases with the

applied voltage, according to Young-Lippmann

equation. The curves obtained here do not follow

exactly Young-Lippmann equation since this classic

theory does not take into account various

phenomena such as energy dissipation and contact

line saturation. These curves are in good qualitative

agreement with those reported by Moita et al. (2016)

taken with biofluids at similar experimental

conditions.

Figure 7: Electrostatic response of the analogue fluids:

contact angle of an actuated droplet (3μl of volume)

deposited on a Teflon substrate, as a function of the

applied voltage.

It is worth mentioning that the surfactant Brij40

solved in water significantly decreases the surface

tension of the solution (Table 1), so the contact

angles are much lower than those obtained with the

other analogue fluids, which have surface tension

values much closer to that of water. However, the

dynamic response of the Brij40 solution to the

electrostatic actuation is similar in magnitude to that

depicted by the other analogue fluids, showing no

evident signs of contact angle saturation for the

highest applied voltages, contrarily to what is

observed for instance in the xanthan gum solutions.

Following these previous results, the Brij40 solution

shows a high potential to be used as an analogue

fluid in our study.

4 CONCLUSIONS

Following our previous work, this paper addresses

the various steps required in the development of a

Cell Deformability Studies for Clinical Diagnostics: Tests with Blood Analogue Fluids using a Drop based Microﬂuidic Device

105

droplet based microfluidic device (based on

electrostatic actuation) for early staged cancer

diagnostics. The first part of the paper summarizes

the steps followed up to now, towards the design and

test of the microfluidic chip and discusses the final

tests on the optimization of the materials, namely of

the dielectric to be used as a coating material to our

chip. Adsorption of the biomaterials has shown to be

a relevant issue in our previous work. So, to

overcome this problem, several analogue fluids are

proposed and tested here, in an original approach, to

infer on their suitability to be used in the test of the

microfluidic device. The analogue fluids are

characterized in terms of their main physico-

chemical properties, the size distribution of the

particles (mimicking the cells) and on their

deformability, since the microfluidic device under

development will explore the potential use of cell

deformability to cancer diagnostics. The preliminary

results discussed here suggest that a surfactant

solution can be used as an analogue. The addition of

the surfactant leads to the formation of semi-rigid

particles with a size distribution (obtained by post-

processing of images taken using Laser Scanning

Fluorescent Confocal Microscopy), and

deformability characteristics compatible with those

of the biosamples to be studied.

ACKNOWLEDGEMENTS

The authors are grateful to Fundação para a Ciência

e a Tecnologia (FCT) for financing the contract of

A.S. Moita through the IF 2015 recruitment program

(IF 00810-2015) and for partially financing this

research through the exploratory project associated

to this contract.

REFERENCES

Chim, J. C. R. M., 2015. Capillary biochip for point of use

biomedical application, MSc Thesis, Instituto Superior

Técnico, Universidade de Lisboa.

Cross, M. M., 1965. Rheology of non-Newtonian fluids: a

new flow equation for pseudoplastic systems, J.

Colloid Sci., 20:417-437.

Dance, A., 2017. The making of a medical microchip.

Nature, 545:512-514.

Geng, Hongyao, Feng, J., Stabryl, L. M., Cho, S. K., 2017

Dielectroetting manipulation for digital microfluidics:

creating, transporting, splitting, and merging droplets.

Lab-on-Chip, 17:1060-1068.

Gossett, D., Weaver, W., Mach, A., Hur, S., Tse, H., Lee,

W., Amini H., Carlo, D., 2010. Label-free cell

separation and sorting in microfluidic systems,

Analytical and Bioanalytical Chemistry, 397:3249-

3267.

Hu, S., Wang, R., Tsang, C. M., Tsao, S. W., Sun, D.,

Lam, H. W., 2018. Revealing elasticity of largely

deformed cells flowing along confining

microchannels. RSC Adv., 8:1030-1038.

Jacinto, F., Moita, A.S., Moreira, A.L.N., 2018. Design,

test and fabrication of a droplet based microfluidic

device for clinical diagnostics. In: Proceedings of the

International Conference on Biomedical

Electronics and Devices – Volume 1: BIODEVICES

2018, 19 – 21 January, Funchal, Madeira, pp. 88-95.

ISBN 978-989-758-277-6.

Kato, M., Tanaka, A., Sasagawa, M., Adachi, H, 2008.

Durable automotive windshield coating and the use

thereof. US Patent, 8043421 B2.

Li, Y., Fu, Y. Q., Brodie, S. D., Alghane, M., Walton, A.

J., 2012. Integrated microfluidics system using surface

acoustic wave and electrowetting on dielectrics

technology. Biomicrofluidics, 6:012812.

Lin, C. C., Wang, J. H., Wu, H. W., Lee, G. B., 2010.

Microfluidic immunoassays. JALA - J. Assoc. Lab.

Autom., 15(3):253–274.

Moita, A. S., Herrmann, D, Moreira, A. L. N., 2015. Fluid

dynamic and heat transfer processes between solid

surfaces and non-Newtonian liquid droplets. Applied

Thermal Engineering, 88:33-46.

Moita, A. S., Laurência, C., Ramos, J.A., Prazeres, D. M.

F., Moreira, A. L. N., 2016. Dynamics of droplets of

biological fluids on smooth superhydrophobic surfaces

under electrostatic actuation, J. Bionic Eng., 13:220-

234.

Moita, A.S., Vieira, D., Mata, F., Moreira, A.L.N., 2018.

Microfluidic devices integrating alternative clinical

diagnostic techniques based on cell mechanical

properties. Biomedical Engineering Systems and

Technologies. Series: Communications in Computer

and Information Science, Chapter 4: Microfluidic

Devices Integrating Clinical Alternative Diagnostic

Techniques Based on Cell Mechanical Properties, N.

Peixoto et al. (Eds.), Springer International

Publishing AG, part of Springer Nature, 881, pp. 74-

93.

Mugele, F, Baret, J.C., 2005. Electrowetting: From basics

to applications. J. Phys. Condensed Mat., 17:R705–

R774.

Nelson, W.C., Kim, C.-j., 2012. Droplet actuation by

Electrowetting-on-Dielectric (EWOD): A review. J.

Adhesion Sci. Tech., 26, 1747-1771.

Pinho, D. M. D., 2018. Blood rheology and red blood cell

migration in microchannel flow. PhD Thesis.

Faculdade de Engenharia da Universidade do Porto.

Pinho, D., Yaginuma, T., Lima, R., 2013. A microfluidic

device for partial cell separation and deformability

assessment. BioChip Journal, 7(4):pp 367-374.

Pollack, M. G., Pamula, V.K., Srinivasan, V., Eckhardt,

A.E., 2011. Applications of electrowetting-based

digital microfluidics in clinical diagnostics, Expert

Ver. Molecular Diagnostics, 11(4):397-407.

BIODEVICES 2019 - 12th International Conference on Biomedical Electronics and Devices

106

Restolho, J., Mata, J. L., Saramago, B., 2009.

Electrowetting of ionic liquids: contact angle

saturation and irreversibility. J. Phys. Chem C, 113:

9321–9327.

Shields I. V., Reyes, C. D., López, G. P., 2015.

Microfluidic cell sorting: A review of the advances in

the separation of cells from debulking to rare cell

isolation, Lab on a Chip, 16:1230–1249.

Takahashi, K., Hattori, A., Suzuki, I., Ichiki, T., 2004.

Non-destructive on-chip cell sorting system with real-

time microscopic image processing, Journal of

Nanobiotechnology, 2:1-8.

Tse, H. T. K., Gossett, D. R., Moon, Y. S., Masaeli, M.,

Sohsman, M., Ying, Y., Mislick, K., Adam, R. P.,

Rao, J. Di Carlo, D., 2013. Quantitative diagnosis of

malignant pleural effusions by single-cell

mechanophenotyping, Science Translational

Medicine, 5(212): 212ra163.

Vieira, D. Mata, F., Moita, A.S., Moreira, A.L.N., 2017.

Microfluidic Prototype of a Lab-on-Chip Device for

Lung Cancer Diagnostics. Proceedings of the 10th

International Joint Conference on Biomedical

Engineering Systems and Technologies - Volume 1:

BIODEVICES, 63-68, 2017, Porto, Portugal, 21-13

February 2017. DOI: 10.5220/0006252700630068,

ISBN: 978-989-758-216-5.

Zeggari, R., Manceau, J. F., Aybeke, E. N., Yahiaoui, E.,

Boireau, E. L., 2014. Design and fabrication of an

acoustic micromixer for biological media activation,

Procedia Engineering, 87:935-938.

Cell Deformability Studies for Clinical Diagnostics: Tests with Blood Analogue Fluids using a Drop based Microﬂuidic Device

107