ETE444 :: Lecture 7

Dr. Mashiur Rahman

Application of Nanotechnology

• Microfluidics and their Applications

– Lab-on-a-Chip

– Materials for Microfluidic Devices

– Biochemical Analysis

– Active Microfluidic Devices

• Single electron transistors

Microfluidics and Their Applications

• Microfluidics covers the science of fluidic behaviors on the micro/nanoscales and the engineering of design, simulation, and fabrication of the fluidic devices for the transport, delivery, and handling of fluids on the order of microliters or smaller volumes.– BioMEMS (Biological or Biomedical

Microelectromechanical Systems)

– Lab-on-a-chip (μTAS : Micro-Total Analysis Systems)

Applications

• Inkjet printing

• Blood analysis

• Biochemical detection

• Chemical synthesis

• Drug screening/delivery

• Protein analysis

• DNA sequencing

Inkjet printing

An inkjet printer is any printer that places extremely small droplets of ink onto paper to create an image.

• The dots are extremely small (usually between 50 and 60 microns in diameter), so small that they are tinier than the diameter of a human hair (70 microns)!

• The dots are positioned very precisely, with resolutions of up to 1440x720 dots per inch (dpi).

• The dots can have different colors combined together to create photo-quality images.

thermal bubble inkjet printer

• Used by manufacturers such as Canon and Hewlett Packard, this method is commonly referred to as bubble jet.

• In a thermal inkjet printer, tiny resistors create heat, and this heat vaporizes ink to create a bubble. As the bubble expands, some of the ink is pushed out of a nozzle onto the paper.

• When the bubble "pops" (collapses), a vacuum is created. This pulls more ink into the print head from the cartridge. A typical bubble jet print head has 300 or 600 tiny nozzles, and all of them can fire a droplet simultaneously.

Picture: howstuffworks.com

PiezoelectricPatented by Epson, this technology uses piezo crystals. A crystal is located at the back of the ink reservoir of each nozzle. The crystal receives a tiny electric charge that causes it to vibrate. When the crystal vibrates inward, it forces a tiny amount of ink out of the nozzle. When it vibrates out, it pulls some more ink into the reservoir to replace the ink sprayed out. Picture: howstuffworks.com

Blood analysis

• A blood test is a laboratory analysis performed on a blood sample that is usually extracted from a vein in the arm using a needle, or via fingerprick.

• Blood tests are used to determine physiological and biochemical states, such as disease, mineral content, drug effectiveness, and organ function. Although the term blood test is used, most routine tests (except for most haematology) are done on plasma or serum, instead of blood cells.

Biochemical detection

• The study of the chemical substances and vital processes occurring in living organisms; biological chemistry; physiological chemistry.

Chemical synthesis

• In chemistry, chemical synthesis is purposeful execution of chemical reactions in order to get a product, or several products. This happens by physical and chemical manipulations usually involving one or more reactions. In modern laboratory usage, this tends to imply that the process is reproducible, reliable, and established to work in multiple laboratories.

• A chemical synthesis begins by selection of compounds that are known as reagents or reactants. Various reaction types can be applied to these to synthesize the product, or an intermediate product. This requires mixing the compounds in a reaction vessel such as a chemical reactor or a simple round-bottom flask. Many reactions require some form of work-up procedure before the final product is isolated. The amount of product in a chemical synthesis is the reaction yield.

Drug screening/delivery

• Drug delivery is the method or process of administering a pharmaceutical compound to achieve a therapeutic effect in humans or animals.

• Drug delivery technologies are patent protected formulation technologies that modify drug release profile, absorption, distribution and elimination for the benefit of improving product efficacy and safety, as well as patient convenience and compliance.

• Most common methods of delivery include the preferred non-invasive peroral (through the mouth), topical (skin), transmucosal (nasal, buccal/sublingual, vaginal, ocular and rectal) and inhalation routes.

• Current efforts in the area of drug delivery include the development of targeted delivery in which the drug is only active in the target area of the body (for example, in cancerous tissues) and sustained release formulations in which the drug is released over a period of time in a controlled manner from a formulation. Types of sustained release formulations include liposomes, drug loaded biodegradable microspheres and drug polymer conjugates.

Protein analysis

• Proteins (also known as polypeptides) are organic compounds made of amino acids arranged in a linear chain. The amino acids in a polymer chain are joined together by the peptide bonds between the carboxyl and amino groups of adjacent amino acid residues. The sequence of amino acids in a protein is defined by the sequence of a gene, which is encoded in the genetic code.

Synthesis

DNA sequencing

• The term DNA sequencing refers to methods for determining the order of the nucleotide bases, adenine, guanine, cytosine, and thymine, in a molecule of DNA. The first DNA sequences were obtained by academic researchers, using laborious methods based on 2-dimensional chromatography in the early 1970s. Following the development of dye-based sequencing methods with automated analysis, DNA sequencing has become easier and orders of magnitude faster. Knowledge of DNA sequences of genes and other parts of the genome of organisms has become indispensable for basic research studying biological processes, as well as in applied fields such as diagnostic or forensic research. The advent of DNA sequencing has significantly accelerated biological research and discovery. The rapid speed of sequencing attained with modern DNA sequencing technology has been instrumental in the sequencing of the human genome, in the Human Genome Project. Related projects, often by scientific collaboration across continents, have generated the complete DNA sequences of many animal, plant, and microbial genomes.

DNA Sequence Trace

Microfluidic system

• consist of microfluidic platforms or devices for – Fluidic sampling

– Control

– Monitoring

– Transport

– Mixing

– Reaction

– Incubation

– Analysis

Lab-on-a-chip

• Lab-on-a-chip is becoming a revolutionary tool for many different applications in chemical and biological analyses due to its fascinating advantages (fast and low cost) over conventional chemical or biological laboratories.

• Furthermore, the simplicity of lab-on-a-chip systems will enable self-testing capability for patients or health consumers overcoming space limitation.

• The idea of lab-on-a-chip is basically to reduce biological or chemical laboratories to a microscalesystem, hand-held size or smaller.

Advantages

• Low cost: Many reagents and chemicals used in biological and chemical reactions are expensive, so the prospect of using very small amounts (in micro- to nanoliter range) of reagents and chemicals for an application is very appealing.

• Requires very small amounts of reagents/chemicals:– enables rapid mixing and reaction: biochemical reaction is mainly

involved in the diffusion of two chemical or biological reagents – microscale fluidics reduces diffusion time as it increases reaction

probabilities– practical terms, reaction products can be produced in a matter of

seconds/minutes, whereas laboratory scale can take hours, or even days.

• Minimize harmful by-products: since their volume is so small

Materials for Microfluidic Devices

• Silicon

• Glass

• Polymer

Silicon

• Microfluidic channels on silicon substrates are usually formed either by wet (chemical) etching or by dry (plasma) etching.

Glass• Excellent optical transparency

• Ease of electro-osmotic flow (EOF).

Fabrication techniques

1. Chemical wet etching

• hydrofluoric acid (HF)

• buffered hydrofluoric acid

• a mixture of hydrofluoric acid, nitric acid, and deionized water (HF, HNO3,H2O)

• 2. Thermal fusion bonding

Polymer

Reasons• Low cost• Ease-of-fabrication• Favorable biochemical

reliability • Compatibility• mass production: using

– Casting– Hot embossing– Injection molding

• successful commercialization

Materials

• Polyimide

• PMMA

• PDMS (Polydimethylsiloxane)

• Polyethylene or polycarbonate

PDMS

• (H3C)3SiO[Si(CH3)2O]nSi(CH3)3 where n is the number of repeating monomer [SiO(CH3)2] units.

polymer micro/nano fabrication techniques

• Casting

• Hot embossing

• Injection molding

CastingCasting is a manufacturing process by which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process. Casting materials are usually metals or various cold setting materials that cure after mixing two or more components together; examples are epoxy, concrete, plaster and clay. Casting is most often used for making complex shapes that would be otherwise difficult or uneconomical to make by other methods.

Casting is a 6000 year old process.[2] The oldest surviving casting is a copper frog from 3200 BC.

Hot embossingHot embossing is essentially the stamping of a pattern into a polymer softened by raising the temperature of the polymer just above its glass transition temperature. The stamp used to define the pattern in the polymer may be made in a variety of ways including micromachining from silicon, LIGA, and machining using a CNC tool (for making large features). A wide variety of polymers have been successfully hot embossed with micron-scale (and below) size features, including polycarbonate and PMMA. This technique is used primarily for defining micro-channels and wells for fluidic devices. The benefits of this approach are the ability to take advantage of the wide range of properties of polymers, as well as the potential to economically mass produce parts with micron-scale features.

Injection moldingInjection molding (British English: moulding) is a manufacturing process for producing parts from both thermoplastic and thermosetting plastic materials. Material is fed into a heated barrel, mixed, and forced into a mold cavity where it cools and hardens to the configuration of the mold cavity. After a product is designed, usually by an industrial designer or an engineer, molds are made by a moldmaker (or toolmaker) from metal, usually either steel or aluminium, and precision-machined to form the features of the desired part. Injection molding is widely used for manufacturing a variety of parts, from the smallest component to entire body panels of cars.

Disposable Smart Lab-on-a-Chip for Blood Analysis

The disposable lab-on-a-chip cartridge has been fabricated using plastic micro-injection molding and plastic-to-plastic direct bonding techniques. The biochip cartridge consists of a fixed volume microdispenser based on the sPROMs (structurally programmable microfluidicsystem) technique, an air-bursting, on-chip pressure source, and electrochemical biosensors.

Microchip PCR

• The PCR reaction is a thermal cycling procedure for amplifying a nucleic acid target. PCR is used to amplify DNA targets and a reverse transcriptase-PCR (RT-PCR) is used for RNA targets.

• PCR is a three step process in which each step is performed at a different temperature.

– 1. In the first step, double-stranded DNA is denatured at a temperature of approximately 95 °C.

– 2. Next, each of the two single strands of DNA are hybridized (annealed) to pairs of oligonucleotide primers at approximately 55 °C.

– 3. In the final step, a thermostable magnesium ion-dependent polymerase derived from Thermophilus aquaticus (Taq polymerase) synthesizes complementary DNA in the region flanked by the primers using added deoxynucleotide triphosphates (dNTP) at approximately 72 °C (extension).

Microchip PCR

Schematic of a flow-through-type of PCR microchip. The serpentine reaction microchannelcrosses each of three zones (T1, T2, T3) each of which is set at a different temperature

Microchip PCR Products

• However, despite strong indications that the development of microchip-based PCR analyzers are nearing completion, few have been commercialized. One example of a PCR microchip-based device is the miniature analytical thermal cycling instrument (MATCHI) system (Smart Cycler see www.cepheid.com). This is a battery-powered portable, real-time, integrated analytical system based on PCR performed in an array of silicon microchambers [52, 59, 61]. The entire system fits inside a briefcase for ease of transport. Applications identified for this nucleic acid analysis device include forensic, environmental and agricultural analyses and detecting biowarfare agents [62, 63, 64].

Commercial products

Lab-on-a-chip :: Diseases & Devices

Optical detection of proteins

Optical detection of proteins and reagent storage and delivery. (i) Schematic representation of the POCKET immunoassay powered by a 9 V battery. (ii) Actual device. (iii) Apparent silver absorbance values of anti-HIV-1 antibodies from HIV-positive patients and control patients. (iv) Schematic representation of reagent-loaded cartridges. (v) Overlay of fluorescence and brightfield images of the immunoreaction area, with fluorescent signal corresponding to presence of labeled detection antibodies on antigen stripes. The concentrations indicated above the picture refer to the concentration of sample tested in each microchannel.

Optical detection of proteins

Immunomagnetic separation and detection of proteins with CMOS Hall sensors. (i) Schematic representation with inset showing actual chip. (ii) Comparison of the outputs of CMOS chip and ELISA

detecting nucleic acids

Integrated nanolitre DNA analysis device. (i) Schematic representation with two liquid samples and electrophoresis gel present. (ii) Optical micrograph of device.