MICROFLUIDICS and Nanofluidics

Presented bySaakre ManjeshManglam Arya

Introduction Fluid is a substance that continually flows under an

applied shear stress

Fluidics: handling of liquids and/or gases

Micro: has at least one of the following features:• Small volumes• Small size• Low energy consumption• Use of special phenomena

What is a micro-fluidic system?

• A system manipulating fluids in channels having cross section dimension on less than 100 micro-meters– Smallest micro-channel: Nano-tube

Micro-channels Nano-tubes

Microfluidics

A microfluidic channel is about thesame width as a human hair, 70 μm

The objectives of micro-fluidic systems

• Micro-Total-Analysis-Systems (mTAS)– One system to provide all of

the possible required analyses for a given type problem

– All processing steps are performed on the chip

– No user interaction required except for initialization

• Lab-on-a-chip• Micro-fluidics in nature

– Alveoli (Lung bubbles)

Advantages of Microfluidics• Low sample and reagent consumption; fluid volumes (μl; nl;

pl; fl)• Small physical and economic footprint• Parallelization and high throughput experimentation• Unique physical phenomena: use of effects in the micro-

domain: Laminar flow Capillary forces Diffusion

Fluid Mechanics• Law: Conservation of mass• Law: Conservation of

momentum• Assumption:

Incompressibility• Assumption: No-slip

boundary• condition, i.e. velocity of

the fluid flow at a surface is zero

Basic PropertiesTypes of fluids:• Newtonian fluids• Non-Newtonian fluids

Types of fluid flow:• Laminar• Turbulent

Newtonian FluidsLinear relationship between stress and strain, i.e. viscosity is independent of stress and velocity

Rate of shearing strain, dv/dy

Non-Newtonian Fluids• Non-linear relationship between shear stress and shear strain• Examples: paint, blood, ketchup, cornstarch solution

Viscosity

• Viscosity is a measure of internal friction (resistance) to flow

Laminar and Turbulent Flow

Laminar flow:• Fluid particles move along smooth paths in layers• Most of energy losses are due to viscous effects• Viscous forces are the key players and inertial forces are negligible

Turbulent flow:• An unsteady flow where fluid particles move along irregular paths• Inertial forces are the key players and viscous forces are negligible

Laminar and Turbulent Flow

Reynolds number• Measure of flow turbulence• Used to help predict similar flow patterns in different

fluid flow situations. • Re < 2000 for laminar• Due to small dimensions• Re < 1 in microfluidic systems

Couette Flow (Laminar)Couette flow:• One of the plates moves parallel to the other• Steady flow between plates• No-slip condition applies

• Gives the pressure drop in an incompressible and newtonian fluid in laminar flow flowing through a long cylindrical pipe of constant section.

• Pressure-driven flow• No-slip condition( A solid boundary, the fluid will have zero

velocity relative to boundary) applies

Poiseuille Flow (Laminar)

Diffusion• Diffusion is the transport of particles from a

region of higher concentration to one of lower concentration by random motion.

Surface Tension• Surface tension is a property of cohesion (the attraction of

molecules to like molecules)• When an interface is created, the distribution of cohesive

forces is asymmetric• Molecules at the surface may be pulled on more strongly by

bulk molecules

Wettability-degree of wetting • wettability is determined by a force balance between adhesive

and cohesive forces.• Adhesion vs. cohesion• Contact angles are a way to measure liquid-surface

interactions

Hydrophobic Hydrophilic

Surface energy

Sample Loading And Injection

SubatmosphericPressure Chamber

Electro-OsmoticPump

Electro-PneumaticDistributor

Small Volume Transport

MicrofluidicDevices

Micro-scale Handling System

Components of Microfludic Device

A microfluidic system for DNA separation

Allow to characterize DNA Fragments with excellent Resolution, and in a small time

DNA micrototal analysis systems (mTAS)have been made through the integration of different processes, such as PCR, separation and detection on a microscale.

Entropy recoiling Entropy trap

Continuous flow microfluidicsDroplet based Microfluidics Digital microfluidicsDNA chips (microarrays) Molecular biology Evolutionary biologyCell behaviorCellular biophysics Optics Acoustic droplet ejection (ADE)Fuel cells A tool for cell biological research Future Directions

Key application areas

Nanofluidics Study of the behavior, manipulation, and control of fluids that are

confined to structures of nanometer

Nanofluids are suspensions of nanoparticles in a base fluid, typically water

Emphasis is put on the very diverse background of nanofluidics in biology, chemistry, physics and engineering and the valuable knowledge available in these disciplines

Classical disciplines related to Nanofluidics and some of the relevant subjects studied

Significant reduction in sample volumes required for analyses

Enables experiments to be carried out that take advantage of laminar flow conditions

High surface to volume ratios

Low concentrations, molecular confinement, and low heat capacity

Advantages of nanofluidics

Manofluidics V/S NanofluidicsMicrofluidics Nano fluidics

Size- micrometer Size- Nanometer

Low Density high Density

LowSurface area to volume ratio

HighSurface area to volume ratio

Low thermal conductivity High thermal conductivity

High particle clogging and sedimentation

Low particle clogging and sedimentation

Stability- Comparatively less Stability- High

Nanoscale forces• Forces will govern the behaviour of the molecules or particles in

nanostructures

• Give rise both to equilibrium phenomena, like differences in ionic distribution, or kinetic phenomena, like (macroscopic) viscosity

• In the 1940s, Derjaguin,Verwey, Landau and Overbeek developed the DLVO theory

• Two major forces acting in the nanometre range between surfaces, namely, electrostatic forces and van der Waals forces

• Very successful in providing the theoretical framework for observed behaviour of colloid interaction and stability

• Electrostatic forces act as far as the electrical double layer extends, which is typically from 1 nm to 100 nm

• depending on the electrolyte concentration, and are either repulsive or attractive

•  van der Waals forces predominantly act at distances smaller than 2 nm and are always attractive

•  In 1954, Derjaguin devised a surface forces apparatus (SFA) to measure the forces acting at nano scale

• Capillary force originates in the adhesion between the liquid and the solid surface molecules, and the cohesion between the liquid molecules

• Atomic force microscopy (AFM) has recently become the most outstanding method for measuring surface forces

Cont……

Phanomena in nanofluidics

• Surface-energy-related phenomena• Shear-related phenomena• Electrical double-layer-related phenomena• Size-related phenomena• Entropy-related phenomena• Molecular-structure-related phenomena

Application• Transport Phenomena• Chemical Analysis• Study of Gene Expression• Water Purification

Transport Phenomena

Chemical Analysis Add functionality for sample manipulations in analytical chemistry, such as

sample injections, separation, purifications, and preconcentration for quantitative and qualitative identification

NCAMs functioning as controllable molecular gates can mediate digital transfer of fluid from one microfluidic channel to another

This capability has consequently found use in a miniaturized lead sensor that uses DNAzyme and for preparative post-separationmprocessing for mass limited samples

Nano Capillary Array Membrane

One system to provide all of the possible required analyses for a given type of problem

All processing steps are performed on the “chip”

No user interaction required except for initialization

High throughput screening (HTS) and diagnostics are two major applications for Lab-on-a-chip

Partitioning of functions between disposable and instrument is very different for HTS and Molecular Diagnostics

Lab-on-chip

Gene Expression Studies• Nanofluidic system to monitor gene expression continually, a

so-called dynamic study. • Altering the genes to express fluorescent proteins and exposing

the cells to different conditions • Measure the effects on gene expression as a change in

fluorescence

Problems•Detectability

concern chemical or physical analysis detection will become very problematic when low concentrations are present

together with small detection volumes

•Fouling and stability

Thank you…..