Phenotypic and genetic dissection of water stress adaptations in pearl millet...ICRISAT
Crop yield is a consequence of several plant biological functions and its interactions with environment. Here we focus on some of basic plant functions related to i) water-use ii) canopy development and iii) agronomic traits and investigate on the relationship of these traits for crop production in different water-stress scenarios using the QTL co-localization approach.
Accelerated ageing of newsprint paper: Changes in swelling ability, WRV and e...Michal Jablonsky
The present paper deals with the effect of accelerated ageing on the ability of fibres to undergo saturation with water and the corresponding swelling kinetics. Changes in the surface charge of aged paper fibres were also investigated. Accelerated ageing was performed with newsprint paper at 98 °C and 50% RH during 0, 3, 5,7, 10, 15, 20 and 30 days. The rate and maximum swelling of accelerated aged paper in water were obtained with a modified monitoring unit measuring wood swelling ability. Since paper swells extremely fast in water, even at 30 °C, this apparatus made it possible for the first time to obtain accurate kinetic data on aged paper swelling in water. The polyelectrolyte titration technique was used to investigate changes in the surface charge on fibres from accelerated aged paper.
Phenotypic and genetic dissection of water stress adaptations in pearl millet...ICRISAT
Crop yield is a consequence of several plant biological functions and its interactions with environment. Here we focus on some of basic plant functions related to i) water-use ii) canopy development and iii) agronomic traits and investigate on the relationship of these traits for crop production in different water-stress scenarios using the QTL co-localization approach.
Accelerated ageing of newsprint paper: Changes in swelling ability, WRV and e...Michal Jablonsky
The present paper deals with the effect of accelerated ageing on the ability of fibres to undergo saturation with water and the corresponding swelling kinetics. Changes in the surface charge of aged paper fibres were also investigated. Accelerated ageing was performed with newsprint paper at 98 °C and 50% RH during 0, 3, 5,7, 10, 15, 20 and 30 days. The rate and maximum swelling of accelerated aged paper in water were obtained with a modified monitoring unit measuring wood swelling ability. Since paper swells extremely fast in water, even at 30 °C, this apparatus made it possible for the first time to obtain accurate kinetic data on aged paper swelling in water. The polyelectrolyte titration technique was used to investigate changes in the surface charge on fibres from accelerated aged paper.
Pore scale dynamics and the interpretation of flow processes - Martin Blunt, Imperial College London, at UKCCSRC specialist meeting Flow and Transport for CO2 Storage, 29-30 October 2015
High-resolution phenotyping Water flow dynamics Chloroplast movementCIMMYT
Remote sensing – Beyond images
Mexico 14-15 December 2013
The workshop was organized by CIMMYT Global Conservation Agriculture Program (GCAP) and funded by the Bill & Melinda Gates Foundation (BMGF), the Mexican Secretariat of Agriculture, Livestock, Rural Development, Fisheries and Food (SAGARPA), the International Maize and Wheat Improvement Center (CIMMYT), CGIAR Research Program on Maize, the Cereal System Initiative for South Asia (CSISA) and the Sustainable Modernization of the Traditional Agriculture (MasAgro)
Landslides of any type, and particularly soil slips, pose a great threat in mountainous and steep terrain environ- ments. One of the major triggering mechanisms for slope failures in shallow soils is the build-up of soil pore water pressure resulting in a decrease of effective stress. However, infiltration may have other effects both before and after slope failure. Especially, on steep slopes in shallow soils, soil slips can be triggered by a rapid drop in the apparent cohesion following a decrease in matric suction when a wetting front penetrates into the soil without generating positive pore pressures. These types of failures are very frequent in pre-alpine and alpine landscapes. The key factor for a realistic prediction of rainfall-induced landslides are the interdependence of shear strength and suction and the monitoring of suction changes during the cyclic wetting (due to infiltration) and drying (due to percolation and evaporation) processes. The non-unique relationship between suction and water content, expressed by the Soil Water Retention Curve, results in different values of suction and, therefore, of soil shear strength for the same water content, depending on whether the soil is being wetted (during storms) or dried (during inter-storm periods). We developed a physically based distributed in space and continuous in time model for the simulation of the hydrological triggering of shallow landslides at scales larger than a single slope. In this modeling effort particular weight is given to the modeling of hydrological processes in order to investigate the role of hydrologi- cal triggering mechanisms on soil changes leading to slip occurrences. Specifically, the 3D flow of water and the resulting water balance in the unsaturated and saturated zone is modeled using a Cellular Automata framework. The infinite slope analysis is coupled to the hydrological component of the model for the computation of slope stability. For the computation of the Factor of Safety a unified concept for effective stress under both saturated and unsaturated conditions has been used (Lu Ning and Godt Jonathan, WRR, 2010). A test case of a serious landslide event in Switzerland is investigated to assess the plausibility of the model and to verify its perfomance.
Micro piv measurements for hydrodynamic characterizations of microfluidic flowsSadiq Rahim
The application presented here is based on a non-invasive method for velocity measurements in micro channels.
A micro PIV measurement system is used to obtain velocity profile distributions in primary flow domain and in vortex zone.
Experimental data is compared to data from numerical simulations.
If both data are consistent to each other, it gives information about vortical structures.
Size segregation of Mono and Bi disperse suspensions in a 2D Lid driven cavityVISHNU RAJA REDDY PALLETI
Studied Shear-induced particle migration and size segregation for Mono-disperse and Bi-disperse with the help of the OpenFOAM toolbox.
Geometry: Lid driven cavity
Effective Viscosity of Actively Swimming Algae Suspensionslucascaretta
As the demand for energy soars, the introduction of algae biofuels as a renewable source of energy is receiving much attention. Suspensions of these actively swimming microorganisms exhibit an effective viscosity that may depend on volume fraction, cell shape, and the nature of locomotion (e.g. ``pushers\'\' vs. ``pullers\'\'). Here we report experimental measurements of shear viscosity for suspensions of unicellular green algae (Dunaliella primolecta, a biflagellated ``puller\'\'). We use a cone-and-plate rheometer to measure the dynamic shear viscosity for both motile and non-motile suspensions of D. primolecta at concentrations ranging from 0.1% to 10% of volume fraction. Viscosity increases with concentration for both cases, but the active suspensions of ``pullers\'\' have a comparatively higher effective viscosity than passive suspensions. This observation confirms recently proposed theories that predict higher effective viscosity for ``puller\'\' suspensions compared to non-motile suspensions. Our locomotion study reveals that motile algal cells prefer to align and migrate in the direction of positive shear flow vorticity. It is our belief that such a shear-induced response of the algal cells impacts the resulting effective shear viscosity.
We developed an open microfluidic system to dispense and manipulate discrete droplets on planar plastic sheets. Here, a superhydrophobic material is spray-coated on commercially-available plastic sheets followed by the printing of hydrophilic symbols using an inkjet printer. The patterned plastic sheets are taped to a two-axis tilting platform, powered by stepper motors, that provides mechanical agitation for droplet transport. We demonstrate the following droplet operations: transport of droplets of different sizes, parallel transport of multiple droplets, merging and mixing of multiple droplets, dispensing of smaller droplets from a large droplet or a fluid reservoir, and one-directional transport of droplets. As a proof-of-concept, a colorimetric assay is implemented to measure the glucose concentration in sheep serum. Compared to silicon-based digital microfluidic devices, we believe that the presented system is appealing for various biological experiments because of the ease of altering design layouts of hydrophilic symbols, relatively faster turnaround time in printing plastic sheets, larger area to accommodate more tests, and lower operational costs by using off-the-shelf products.
Pore scale dynamics and the interpretation of flow processes - Martin Blunt, Imperial College London, at UKCCSRC specialist meeting Flow and Transport for CO2 Storage, 29-30 October 2015
High-resolution phenotyping Water flow dynamics Chloroplast movementCIMMYT
Remote sensing – Beyond images
Mexico 14-15 December 2013
The workshop was organized by CIMMYT Global Conservation Agriculture Program (GCAP) and funded by the Bill & Melinda Gates Foundation (BMGF), the Mexican Secretariat of Agriculture, Livestock, Rural Development, Fisheries and Food (SAGARPA), the International Maize and Wheat Improvement Center (CIMMYT), CGIAR Research Program on Maize, the Cereal System Initiative for South Asia (CSISA) and the Sustainable Modernization of the Traditional Agriculture (MasAgro)
Landslides of any type, and particularly soil slips, pose a great threat in mountainous and steep terrain environ- ments. One of the major triggering mechanisms for slope failures in shallow soils is the build-up of soil pore water pressure resulting in a decrease of effective stress. However, infiltration may have other effects both before and after slope failure. Especially, on steep slopes in shallow soils, soil slips can be triggered by a rapid drop in the apparent cohesion following a decrease in matric suction when a wetting front penetrates into the soil without generating positive pore pressures. These types of failures are very frequent in pre-alpine and alpine landscapes. The key factor for a realistic prediction of rainfall-induced landslides are the interdependence of shear strength and suction and the monitoring of suction changes during the cyclic wetting (due to infiltration) and drying (due to percolation and evaporation) processes. The non-unique relationship between suction and water content, expressed by the Soil Water Retention Curve, results in different values of suction and, therefore, of soil shear strength for the same water content, depending on whether the soil is being wetted (during storms) or dried (during inter-storm periods). We developed a physically based distributed in space and continuous in time model for the simulation of the hydrological triggering of shallow landslides at scales larger than a single slope. In this modeling effort particular weight is given to the modeling of hydrological processes in order to investigate the role of hydrologi- cal triggering mechanisms on soil changes leading to slip occurrences. Specifically, the 3D flow of water and the resulting water balance in the unsaturated and saturated zone is modeled using a Cellular Automata framework. The infinite slope analysis is coupled to the hydrological component of the model for the computation of slope stability. For the computation of the Factor of Safety a unified concept for effective stress under both saturated and unsaturated conditions has been used (Lu Ning and Godt Jonathan, WRR, 2010). A test case of a serious landslide event in Switzerland is investigated to assess the plausibility of the model and to verify its perfomance.
Micro piv measurements for hydrodynamic characterizations of microfluidic flowsSadiq Rahim
The application presented here is based on a non-invasive method for velocity measurements in micro channels.
A micro PIV measurement system is used to obtain velocity profile distributions in primary flow domain and in vortex zone.
Experimental data is compared to data from numerical simulations.
If both data are consistent to each other, it gives information about vortical structures.
Size segregation of Mono and Bi disperse suspensions in a 2D Lid driven cavityVISHNU RAJA REDDY PALLETI
Studied Shear-induced particle migration and size segregation for Mono-disperse and Bi-disperse with the help of the OpenFOAM toolbox.
Geometry: Lid driven cavity
Effective Viscosity of Actively Swimming Algae Suspensionslucascaretta
As the demand for energy soars, the introduction of algae biofuels as a renewable source of energy is receiving much attention. Suspensions of these actively swimming microorganisms exhibit an effective viscosity that may depend on volume fraction, cell shape, and the nature of locomotion (e.g. ``pushers\'\' vs. ``pullers\'\'). Here we report experimental measurements of shear viscosity for suspensions of unicellular green algae (Dunaliella primolecta, a biflagellated ``puller\'\'). We use a cone-and-plate rheometer to measure the dynamic shear viscosity for both motile and non-motile suspensions of D. primolecta at concentrations ranging from 0.1% to 10% of volume fraction. Viscosity increases with concentration for both cases, but the active suspensions of ``pullers\'\' have a comparatively higher effective viscosity than passive suspensions. This observation confirms recently proposed theories that predict higher effective viscosity for ``puller\'\' suspensions compared to non-motile suspensions. Our locomotion study reveals that motile algal cells prefer to align and migrate in the direction of positive shear flow vorticity. It is our belief that such a shear-induced response of the algal cells impacts the resulting effective shear viscosity.
We developed an open microfluidic system to dispense and manipulate discrete droplets on planar plastic sheets. Here, a superhydrophobic material is spray-coated on commercially-available plastic sheets followed by the printing of hydrophilic symbols using an inkjet printer. The patterned plastic sheets are taped to a two-axis tilting platform, powered by stepper motors, that provides mechanical agitation for droplet transport. We demonstrate the following droplet operations: transport of droplets of different sizes, parallel transport of multiple droplets, merging and mixing of multiple droplets, dispensing of smaller droplets from a large droplet or a fluid reservoir, and one-directional transport of droplets. As a proof-of-concept, a colorimetric assay is implemented to measure the glucose concentration in sheep serum. Compared to silicon-based digital microfluidic devices, we believe that the presented system is appealing for various biological experiments because of the ease of altering design layouts of hydrophilic symbols, relatively faster turnaround time in printing plastic sheets, larger area to accommodate more tests, and lower operational costs by using off-the-shelf products.
Similar to CDAC 2018 Dubini microfluidic technologies for single cell manipulation (20)
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
CDAC 2018 Dubini microfluidic technologies for single cell manipulation
1. Microfluidic Technologies
for Single Cell Manipulation
Como, 23 May 2018
Gabriele Dubini
Department of Chemistry, Materials and Chemical Engineering
‘Giulio Natta’
3. Microfluidics is the science of designing, manufacturing, and formulating devices
and processes that deal with volumes of fluid on the order of nanoliters or
picoliters.
What is microfluidics?
4. • Sample and medium - and waste handling - savings: e.g. nL of enzyme,
not mL
• Faster - and cheaper - analyses: can heat, cool small volumes quickly
• Integration: combine lots of steps onto a single device (including
parallelization)
• Automated processes
• Novel physics: diffusion, surface tension, and surface effects dominate
- This can actually lead to faster reactions!
• New functionalities, often impossible at the macroscopic level
Why use microfluidics?
5. van Duinen, Trietsch, Joore, Vulto, Hankemeier. Microfluidic 3D cell culture: from tools to tissue models.
Current Opinion in Biotechnology, 2015; 35: 118-126.
Why use microfluidics?
6. Several reasons make microfluidic devices and systems
interesting also for cell manipulation:
• The increasing interest for living cells
• The integration of several standard analytical
operations
• The possibility to manipulate large numbers of cells
simultaneously
• The possibility of manipulate single objects with cellular
dimension by micromechanics device
http://yoon.eecs.umich.edu/microfluidics.html
Motivation for microfluidics in cell biology
10. An early-concept for an integrated device with two liquid samples
and electrophoresis gel present
Burns et al., Science, 1998
Blue, liquid sample (ready for
metering)
Green, hydrophobic surfaces
Purple, polyacrylamide gel
11. Zhang and Nagrath. Microfluidics and Cancer: Are we there yet? Biomed. Microdevices 2013
13. Laminar and turbulent flow: the Reynolds number
water
ink
µ
ρ
= cLw
Re
x
y
z
wx
τy+dy
τy
dxdydz
x
w
wdxdydz
Dt
Dw x
x
∂
∂
ρ=ρ=forces(inertial)convective
( ) dxdydz
y
w
dxdzdy
y
w
y
dxdzdy
y
dxdz xx
ydyy 2
2
forcesviscous
∂
∂
µ=
∂
∂
µ
∂
∂
=
∂
τ∂
=τ−τ= +
carat
x
L
w
x
w
∝
∂
∂
22
2
caratt
x
L
w
y
w
∝
∂
∂
conduitsindiameterhydraulic
4
lengthsticcharacteri ==== h
t
c D
P
A
L
wwx ∝
16. 0=⋅∇ w
( ) gwww
w
ρ+∇µ+−∇=
∇⋅+
∂
∂
ρ 2
p
t
(mass conservation)
(momentum conservation)
Hypotheses: incompressible, homogeneous, Newtonian fluid
Incompressible, Newtonian fluids:
the Navier-Stokes equations
17. A particular case: 2-D Navier-Stokes equations for steady-state flow
𝜌
𝜕𝑤 𝑥
𝜕𝜕
+ 𝑤 𝑥
𝜕𝑤 𝑥
𝜕𝑥
+ 𝑤𝑧
𝜕𝑤 𝑥
𝜕𝑧
= −
𝜕𝜕
𝜕𝜕
+ 𝜇
𝜕2 𝑤 𝑥
𝜕𝑥2 +
𝜕2 𝑤 𝑥
𝜕𝑧2
𝜌
𝜕𝑤𝑧
𝜕𝜕
+ 𝑤 𝑥
𝜕𝑤𝑧
𝜕𝑥
+ 𝑤𝑧
𝜕𝑤𝑧
𝜕𝑧
= −
𝜕𝜕
𝜕𝜕
+ 𝜇
𝜕2
𝑤𝑧
𝜕𝑥2
+
𝜕2
𝑤𝑧
𝜕𝑧2
𝜕𝑤 𝑥
𝜕𝜕
+
𝜕𝑤𝑧
𝜕𝑧
= 0
𝜕𝜕
𝜕𝜕
= 𝜇
𝜕2
𝑤 𝑥
𝜕𝑧2
and, if the pressure gradient ∂P/∂x is constant and equal to ∆P/L:
𝑤 𝑥 𝑧 =
∆𝑃ℎ2
8𝜇𝜇
1 −
4𝑧2
ℎ2
= 𝑣 𝑚𝑚𝑚 1 −
4𝑧2
ℎ2
−
ℎ
2
≤ 𝑧 ≤ +
ℎ
2
for
x
y
z
L
w
h
h « L
h « w
𝑤 𝑥 =
1
𝐴 𝑡
� 𝑤 𝑥 𝑧 𝑑𝑑
+
ℎ
2
−
ℎ
2
=
2
3
∆𝑃ℎ2
8𝜇𝜇
18. Pressure (P) and shear stress (τ) are different:
• Pressure is the force per unit area acting in the normal direction to an (ideal)
surface within a fluid.
• Shear stress is the force per unit area acting in the tangential direction to an
(ideal) surface within a moving fluid.
Under steady-state conditions, force equilibrium in the longitudinal direction for
the yellow volume of fluid yields:
𝑃𝜋𝑟2
− 𝑃 − ∆𝑃 𝜋𝑟2
= 𝜏 2𝜋𝜋𝜋
∆𝑃
𝑙
=
2𝜏
𝑟
→ 𝜏 𝑟 =
∆𝑃
𝑙
∙
𝑟
2
Pressure and shear stress in a steadily moving fluid
19. Height of the channel (mm)
Pressure and shear stress in a steadily moving fluid
23. Comparison between volume densities of culture conditions in
traditional, macroscale culture in 6-well plates and in microscale,
microchannel culture (750 µm wide, 5 mm long, and 250 µm tall).
Paguirigan and Beebe, BioEssays, 2008
Scale effects
28. Effects of micro domain
– laminar flow
– surface tension
– surface effect
– electrowetting
– diffusion
The behavior of fluids at the microscale
29. Active flow mixers
Laminar flow
Cortelezzi, Ferrari and Dubini. A scalable active micro-
mixer for biomedical applications. Microfluidics and
Nanofluidics 2017; 21(3): article no. 31.
31. Cell responses on surface chemistry of channel walls:
1) surface hydrophobicity
2) protein adsorption
3) surface charge
4) surface roughness
5) surface softness and stiffness
Pinning fluid–fluid interfaces by chemically
inhomogeneous surfaces in static (c) and
flowing systems (d). Altering the wetting
properties using chemically homogeneous,
micro- and nanostructured surfaces: (e, f ).
(Gűnther and Jensen, Lab on a Chip, 2006)
Surface effects
32. Driving force for fluid
motion and the
channel
characteristics can
be chosen
independently
A flow driven by either a pressure
gradient, an electric field, or a
surface tension gradient.
A surface modified chemically in stripes. A surface modified with topography.
Stone et al. Annu. Rev. Fluid Mech., 2004
Surface effects
33. Electrical modulation of the solid-liquid interfacial tension
No Potential
A droplet on a hydrophobic
surface originally has a
large contact angle.
Applied Potential
The droplet’s surface
energy increases, which
results in a reduced contact
angle. The droplet now
wets the surface.
Electrowetting
34. Analyte D (m2/s) Pe
Na+ (100 pm) 10-9 10
Glucose 6×10-10 17
Albumine (BSA, 10 nm) 10-11 103
Viron (100 nm) 10-12 104
Bacterial Cell (1 µm) 10-13 105
Erythrocyte (10 µm) 10-14 106
Polystyrene Bead (100 µm) 10-15 107
Diffusivities and representative Péclet numbers for dilute analytes
in water at 25 °C (100 mm wide channel, 100 mm/s mean velocity)
Smith et al., Electrophoresis, 2012
Diffusion
35. Continuous-flow : Permanently etched microchannels, micropumps and
microvalves
Digital microfluidic : Manipulation of liquids as discrete droplets
Biosensors:
Optical: SPR, Fluorescence, etc.
Electrochemical: Amperometric,
Potentiometric, Impedence-based, etc.
Mixing: Static,
Diffusion Limited
Multiplexing
Microfluidic platforms
37. 𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷 𝐷 =
𝑘 𝐵 𝑇
6𝜋𝜋𝜋
𝑃𝑃𝑃𝑃𝑃𝑃 𝑁𝑁𝑁𝑁𝑁𝑁 𝑃𝑃 =
𝑈𝐷ℎ
𝐷
𝑆ℎ𝑒𝑒𝑒𝑒𝑒𝑒 𝑁𝑁𝑁𝑁𝑁𝑁 𝑆ℎ =
ℎ𝐷ℎ
𝐷
Diffusivity characteristic time vs
convective characteristic time
Convective mass flux vs
diffusive mass flux
Parameters from ‘macroscopic’ transport phenomena - 2
38. (a)-(d) Contours of fluorescent light intensity (FLI), which indicate bacterial
concentration, plotted for RP437 E. coli at different time snapshots.
(e)-(h) Bacteria collect in the vortex pair as shown by FLI contours overlaid on the
flow streamlines (solid blue lines) (Yazdi and Ardekani, Biomicrofluidics, 2012).
Local fluid dynamics and cell adhesion
39. Smith et al., Electrophoresis, 2012
𝑆𝑆𝑆𝑆𝑆𝑆 𝑁𝑁𝑁𝑁𝑁𝑁 𝑆𝑆 =
𝜌 𝑝 𝐷 𝑝
2 𝑈
18𝜇𝐷ℎ
Particle time scale vs
flow time scale
PCTC: prostate circulating tumor cell
Local fluid dynamics and cell displacement
40. Smith et al., Electrophoresis, 2012
Local fluid dynamics and cell displacement
41. • rely on a diffusive process to cause cells to randomly move
transverse to streamlines,
• apply a body force (e.g., gravity or dielectrophoresis) to move the
cells transverse to streamlines,
• create geometries in the flow so that flow is accelerated,
streamlines are compressed and the cells are effectively brought in
proximity to the wall by motion along a streamline,
• make the wall permeable and allow the streamlines to cross the
interface.
Possible ways to bring cells in contact to a wall
42. 𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶 𝑁𝑁𝑁𝑁𝑁𝑁 𝐶𝐶 =
𝜇𝑈 𝑑
𝜎
𝐵𝐵𝐵𝐵 𝑁𝑁𝑁𝑁𝑁𝑁 𝐵𝐵 =
∆𝜌 𝑔𝐷ℎ
2
𝜎
𝑊𝑊𝑊𝑊𝑊 𝑁𝑁𝑁𝑁𝑁𝑁 𝑊𝑊 =
𝜇𝑈 𝑑
2
𝐷ℎ
𝜎
Gravity vs interfacial forces
Viscous vs interfacial forces
Inertial vs interfacial forces
Presence of suspended cells multiphase flows
Parameters from ‘macroscopic’ transport phenomena - 3
43. Inertial, viscous and gravitational body forces, relative to interfacial forces,
as a function of the channel size and characteristic velocity in microfluidic
multiphase systems
Gűnther and Jensen, Lab on a Chip, 2006
Parameters from ‘macroscopic’ transport phenomena - 4
44. Strain rates can be large in the microflows.
In the simplest case, τ ≈ U/h, which can yield 103 - 104 s−1.
Such values are sufficiently large to cause non-Newtonian
rheological effects, if suspended deformable objects are
present.
𝐷𝐷𝐷𝐷𝐷𝐷ℎ 𝑁𝑁𝑁𝑁𝑁𝑁 𝐷𝐷 =
𝑡 𝑐
𝑡 𝑝
Material stress relaxation time vs
characteristic time scale
Presence of suspended cells non-Newtonian fluids
A well known effect - since 1929 - is the Fåhraeus effect for
blood flowing in small tubes (I.D. < 0,3 mm).
Parameters from ‘macroscopic’ transport phenomena – 5
45. Bianchi et al. Journal of Biomechanics, 2012
Example 1:
Shear-stress dependent leukocyte adhesion assays
46. mediators
Ronen Alon , Immunity ,2007
Blood flow
Particles interactions
(platelets –
erithrocytes)
τω
Fdragτm
Normal and shear
stresses on the
cell membrane
Normal and shear
stresses on the
endothelial wall
Multiple steps cascades controlled by
integrated chemoattractant-dependent
signals and adhesive events
Endothelial ligands involved in that second step
of firm adhesion are intercellular adhesion
molecules (ICAMs) and vascular cell
adhesion molecules (VCAMs).
inflammation
Leukocyte Shear dependent adhesion and
transmigration across vessel wall in
inflammation
Example 1:
Shear-stress dependent leukocyte adhesion assays
53. Material for the fabrication
of microfluidic channels
Silicon / Si compounds
Classical MEMS approach
Etching involved
Polymers / plastics
New methods
Easy fabrication
57. There are two types of photoresist:
• Positive: Exposure to UV light removes resist
• Negative: Exposure to UV light maintains resist
Mask
Positive Resist Negative Resist
Photolithography
60. Polymethyl methacrylate (PMMA)
• Often used as an alternative to glass
• Easily scratched
• Not malleable
• It can come in the form of a powder mixed
with liquid methyl methacrylate, which is an
irritant and possible carcinogen
64. • Access for colture medium (nutrients, GFs, etc.)
• Access for drug adminstration
• Compatible with robotic system access
• Compatible with micropipetting access
• Suitable for incubator use
• Pressurized vs. open wells
Design requirements
68. PDMS bonded on glass
many valves and tubings
280 wells - up to 600 cells/well
Provides nutrients through lateral
channels and sieves/valves
Up to 5 wells in series
Wells are not accessible with a
pipetting manual/robotic system
Unsuitable for incubator
70. 48 single-cell processing units
Fully automated, including:
• Cell selection and isolation
• Cell culture
• Imaging
• Exposure to drug
• Cell lysis and generation of
cDNA from mRNA
• PCR and cDNA harvesting
https://www.fluidigm.com/products/polaris#components