 previous lecture we discussed some aspects of cellular microfluidics, cellular biomicrofluidics and in this particular lecture we will continue with that spirit for DNA based biomicrofluidics. So, as we all know DNA is the genetic material of most of the species and contains inheritable biological information making each species unique. Given biochemical and or biophysical stimulation DNA regenerates itself by the process called as replication and later transcribes which is called as transcription and translates which is called as translation to RNA and polypeptide respectively. So, as you all know that DNA has 4 kinds of bases, DNA is double stranded typically and it has a 1 is to 1 ratio of purine to pyrimidine bases and hydrogen bonds are formed between the different bases so that A wants to get combined with T and G wants to get combined with C. So, you have A, T, C and G these 4 bases. So, if you look into a single DNA strand, so you can see that a DNA strand has phosphate group which is shown by the yellow circles in this diagram. Then sugar which is shown by this blue region and each sugar is connected with one particular nitrogen containing base like A, C, G, T like that. So, now why is DNA based microfluidics important? Let us say that you are interested to identify whether a particular diseased condition is present which is associated with a particular DNA sequence say A, T, G, C, T, A, G, C whatever. Now what you can do is you can put the complement of that sequence which you want to interrogate in the wall of platform. So if you have a wall on the wall you have capturing DNA probes which are basically complements of what you want to interrogate because you know that if you want to interrogate A you should keep T on the wall because T wants to get combined with A. So, whatever you want to interrogate the complement of that sequence you put on the wall and then what you do? You basically start with single-stranded DNA. So you heat the double-stranded DNA and the double-stranded DNA can be broken into two single strands. So before heating the DNA basically you can break the cell and bring the DNA out of it. This is called as cell lysis. So this you can do even mechanically. Once you bring the DNA out of it then you heat the DNA sample so that the double-stranded DNA gets broken into two single strands and then each single strand will pass through the sample and if there is a complementary sequence of the base in the wall of the substrate then there will be a successful mating of these two giving rise to a double-stranded DNA formation. So a complementary, a particular DNA sequence mates with its corresponding complementary sequence and if this is a successful mating with a complementary DNA sequence of another single strand then this process is known as DNA hybridization. So in this process you can identify diseases. So nucleic acid probes can be used to identify the presence of complementary DNA in a patient sample and this binding of two strands is known as hybridization. Two DNA strands must share at least 16 to 20 consecutive bases of perfect complementary to form a stable hybrid. Now the probes are labeled with markers. How do you know that there is a successful hybridization? These markers may be radioisotopes, fruedochromes, enzymes or chemiluminescent substrates for easy detection. So what are the applications? The applications may be in forensics, food monitoring, environment monitoring, drug discovery and several other applications. Now why do you go for microfluidics based DNA hybridization? The conventional devices for DNA hybridization are of passive type. That is the DNA sample in the fluid has to move by diffusion. Now you know that diffusion is a slow process. It will take several hours if not days to complete the hybridization process and the typical diffusion coefficient is of the order of 10 to the power –11 meter square per second for oligonucleotides that are of 18 base pairs in length and then in a pure diffusive environment the DNA will reach the capture proof probes only by Brownian motion in order to hybridize. What is an alternative? You can apply electric field. Why you can apply electric field? As we have just seen the DNA has a phosphate group and the phosphate group has negative charge. Because the phosphate group has negative charge you can make the DNA move by electric field. So this is called as DNA electrophoresis. Now if you have DNA electrophoresis, the DNA electrophoresis has several advantages that means it has a large electrophoretic mobility about 15,000 micrometer square per volts again for the charge negatively charged DNA. Now one of the critical bottlenecks still is that now this sample solution which contains the DNA must be desalted to have a strong effect of this DNA electrophoresis. Because the salt the salted DNA solution essentially screens the electric field larger the salt concentration more effective is the screening of the electric field and that means the electric field acts only in a small proximity close to the electrode but not throughout the sample. On the other hand in molecular biology you require a salted solution. So there is a little bit of conflict between these two requirements and therefore instead of a transverse electric field you could possibly use an axial electric field where the combination of the transverse electric field due to the electrical double layer or any induced transverse electric field and an axial electric field can give rise to electro osmosis of DNA. It is not electrophoresis that we are talking about now. It is electro osmosis by an axial electric field but you know with anything good there is always something which is adverse. So what is adverse about it that with axial electric field and transverse electric field combined there may be a significant electric field throughout the sample which can give rise to significant heating of the sample. Because of the significant heating there may be denaturation or the breaking of the successfully hybridized double stranded DNA again back to single strands. So thermally labile samples not just DNA but any thermally labile samples are not good to handle in a situation when there is significant heating or overheating of the sample. So one has to go for some alternative techniques for DNA hybridization. Now before going into the alternative techniques of DNA hybridization I would just like to highlight that if you are interested to study this problem mathematically that DNA hybridization in an electric field in addition to the fluid flow equation you will need to solve this species conservation equation. And here you can see that we require the full species transport equation considering charge of the species. So if you look into this equation you have the unsteady term, advection term, diffusion term this is electro migration term this is because of the phosphate group in the DNA that you have the negative charge of the DNA and that makes the DNA movement possible by electric field. In addition to that because there are capturing probes on the surface there is a reactive term in the species transport equation. So like typically the homogeneous reaction of the suspended is species in the fluid which may be the single standard DNA. So the concentration of DNA as a function of time you can see that with combined pressure driven and electro osmotic flow you can have very rapid increase in the concentration and that means that you have very successful hybridization but as I told that with an electric field you also have joule heating effects and that joule heating effect has to be taken into consideration. So to obviate the joule heating effects we in collaboration with Professor Mark Mardu's group at the University of California at Irvine started to looking into a problem both computationally and later on it was validated experimentally that instead of using electric field you can use a mechanical actuator which is an oscillatory flap made of a soft material called as polypural a flexible material which is called as polypural. I will try to run this movie and if it does not run from here I will try to run it hopefully the movie runs yes so you can see that there is an oscillatory flap and with the oscillation of the flap you have so I will show you the movie again look into the movie carefully with the oscillation of the flap what is happening is that the DNA sample is being flushed towards the wall where capturing DNA probes are located. So these flaps which are oscillating on the wall are enhancing the rate of DNA hybridization by acting simultaneously as a mixer and a pump. Now the question is if there are many interrogating probes on the wall of a microfluidic channel then what do you achieve by just targeting all the DNA sample on the on one of the probes on the wall then the other probes which are located in the subsequent downstream locations will not get the DNA sample that they are looking for. So what you need to do is to you need to optimally distribute the incoming DNA sample towards the wall capturing probes where multiple probes are located so for that you require multiple oscillating flaps. So I will try to show you one such scenario where you have multiple oscillatory flaps so 2 flaps here are oscillating I will try to run the movie once more so you have multiple oscillatory flaps so that the DNA sample is targeted to various capturing probes optimally. Now look at this problem a problem is to identify a particular genetic sequence to do that you have a micro to achieve that you have a microfluidic system in which you have an oscillatory flap and to design the microfluidic system what do you require to design the microfluidic system you require a total idea of the fluid flow within the system for that you actually need to solve a fluid structure interaction problem. Because the oscillatory flap is a soft material and it is a it is essentially a structure which responds dynamically to the fluid flow and in turn gives a dynamical response to the fluid flow by virtue of which there is alteration of local pressure and stresses so that it is a coupled fluid structure interaction problem and it is one of the very interesting problems in the area of computational fluid dynamics. So the idea that what I want to impress upon you is that on one side we have an outstanding problem in biomedical applications or medical science and medical technology on the other side we have fluid mechanics and we can see that how these things are coupled and how these things should be brought in together to solve the outstanding problem. Now some new directions now we have discussed about cell on a chip but there are issues when single cell based analysis does not give good enough an indicator so one needs to go for organs on a chip. So instead of mimicking a single cell one can mimic a collection of cells which is called as organ on a chip. So it will mimic the behaviour of an organ not only that organs on a chip can be used as a new tool for drug discovery like one can study the influence of certain drugs on a particular organ by mimicking a organ like entity on a microfluidic chip and doing totally in vitro studies that is this can be used as an alternative to animal trials so that one can get a clear indicator of the behaviour. Now finally what next the ultimate concept which has been conceptually discussed in the literature is human body on a chip. Now it might appear to be a science fiction but you have to understand that by human body on a chip I do not want to mean that it is a literal human body that is built on a microfluidic chip. So what is the motivation let us say that certain drug is used to cure a certain disease but many times the effect of the side effect of the drug on other parts or other organs of the same human body can give rise to many adverse consequences it can even give rise to death. So it is important to understand that eventually one has to carefully design the treatment by a priori looking into the adverse side effects of a drug on other organs on which it is not directly targeted. So instead of making a comprehensive time consuming and otherwise ethically involved animal trials one can go for a microfluidic based system where very rapidly one can make trials with certain drugs before implementing the medical treatment. And then this can be this microfluidic system if you look into this view graph you will see that this microfluidic system essentially is a connective network which includes several essential organs in the human body not in their appropriate size but in a notional form with the with the collection of cells representing their collective behaviour of these types of organs. And then these notional organs not physical organs these notional organs are connected through a complex microfluidic network. So this is called as human body on a chip. So I think that human body on a chip is going to be one of the futuristic platforms that can replace the animal trial based drug screening systems. So to summarize the discussion so far on bio microfluidics we have discussed about cellular microfluidics and traction force microscopy and DNA based microfluidics and recent developments on organ on a chip and human body on a chip. So with this particular note we will get into the second part of our discussion on bio microfluidics and the second part of our discussion on bio microfluidics will be dictated or will be dedicated towards some specific applications which in a common umbrella I call as healthcare engineering. Now these days healthcare is of course always a professional job of a medical professional but engineering is one of the parts and parcels of addressing healthcare issues and therefore like in a common umbrella where all the engineering activities can be engulfed then related to healthcare that may be called as healthcare engineering. Now in healthcare engineering other than microfluidics there are several other branches of engineering that come into the picture but because this is a particular course on microfluidics I will discuss about some issues on bio microfluidics for healthcare engineering. So what is the motivation like as we see that in locations with limited resources it is quite difficult that one gives a good healthcare facility to an individual who is there in a rural place or a place which is not easily accessible to big or very advanced healthcare centres. So what is the consequence? Let us think about a problem in a rural underdeveloped scenario. Let us say somebody is suffering from fever now when the person is suffering from fever the person I mean usually 1 or 2 or 3 days we will just go by observing the tendency of the fever and when the fever is still not going away then the person has to be brought to a healthcare centre which is located quite a few kilometres from his or her own residence in the village then in the healthcare centre the sample is taken blood urine saliva whatever and then that will be taken further in a lab where in a costly environment because the traditional medical diagnostics will require a good amount of samples so it will require a good amount of consumables or chemicals to test the sample and then based on the results from the sophisticated lab when the answer to the test comes out and it reaches it comes back to the patient by the time a significant time has elapsed a significant cost has been incurred which the patient might not be able to bear and given the time and the cost involved the situation of the patient by that time might have deteriorated significantly. So what micro fluidics can do about it? So instead of going through this route micro fluidics can use point of care diagnostic devices so some handheld devices in which there are micro fluidic platforms and then instead of having a very sophisticated personnel I mean or a very sophisticated healthcare worker you can have a minimally trained healthcare worker who can just take say one drop of blood for example from the fingertip and then load it in a micro fluidic device what kind of micro fluidic device we will discuss it load in a micro fluidic device and then based on certain detection techniques it may be a colorimetric technique for an example. So there can be a change in color of the blood sample or there can be other diagnostic indicators by that the result will come immediately in a low cost micro fluidic environment in a rapid manner the patient need not be taken to the hospital rather it is like a mobile hospital that is taken to the patient. So it is a portable system and the answer to the test will immediately come so that the treatment can be delivered immediately in a low cost paradigm that is what micro fluidics can achieve. So the limitations of traditional diagnostics the state of the hour diagnostic technologies are lab intensive time consuming they require expensive chemicals and sophisticated instruments they require intervention of expert personnel and it is difficult to execute these protocols from places having limited resources. So with this little bit of background so one has to understand that it is not just micro fluidic as a detection tool we want to use but we can also use it as a treatment protocol and we will later on see an example where we use micro fluidics for as a protocol for treatment of say certain ailments like diabetes management for example. But first we will discuss about the disease detection like either identification or isolation or quantification. So identification of a disease will just give yes no answer the person is suffering from a disease yes or no isolation or quantification means to what extent the disease has progressed so that quantitative estimation of the test. So most of the times the common many of the common tests are based on a biosensor design so basically you rely on antigen antibody reaction. So if there is a so what you do is that if there is a successful antigen antibody reaction so if you want to interrogate a particular disease you can put the corresponding antigen or antibody on the wall of a micro fluidic channel and if the blood sample has a matching antibody or antigen there will be an antigen antibody reaction and there will be a change in color of the sample and by this colorimetric detection with proper image processing one can get an idea of the quantitative extent of the progress of the disease. So you can see that eventually you require a platform in which you are having blood urine saliva this type of sample fluid flowing through a micro fluidic system and what kind of micro fluidic system I can give a couple of examples I will not get into the details of this examples because we have already discussed this in our course and I want to relate whatever we have discussed in our course with the practical applications of medical diagnostics here. One is the lab on a CD platform so just to refresh your memory you basically make a compact disc with 5 layers in which there are micro channels in a couple of micro channels cut in a couple of layers and blood samples are loaded and then you can have reactions in this rotating platform and very quickly you can get the d-dows. So we have studied the control movement of a fluid on a compact disc and you can see here for example like how the blood samples are loaded and how they are tested on a compact disc. So you can study several reactions in a compact disc like enzymatic reaction on a CD for example and because by a single rotation you can actuate the movement of blood in many radial and cross radial channels and each channel can make one test. So it is possible that on a single CD you can make thousands of tests in thousands of channels by using just a very small volume of blood and a small volume of reactants or chemicals that will possibly react with the blood sample. You do not require separate actuations to actuate the movement of blood in different channels just by a simple single motor you can actuate the movement. So we had made several test runs on the rotating platform like for example malaria detection on a compact disc. So like this compact disc based platform or CD based platform can be well suited to be a nice point of care diagnostic platform for many places with limited resources typically rural places. We have also discussed about paper based microfluidics. So in the paper based microfluidics we make paper channels and this also we have discussed so I am going through this a little bit faster because I have already discussed most of these but I want to relate this with the medical diagnostic scenario. So you basically make microfluidic channels by inexpensive fabrication technologies. The paper has many pores so you block certain pores so that you have a specific direction in which the blood sample will flow. So basically the fluid flows through the paper matrix normally by capillary action. There are various fabrication techniques by which you can make channels on the paper. So we have discussed about the some fabrication innovations earlier by which in a low cost paradigm like for example using inkjet printing you can make very simple and cost effective micro channels on a paper matrix through which you study fluid flow. Not only that to make the blood sample move faster so that you have more rapid diagnostics you can make electrodes on a paper and apply fluid flow, apply electric field to accelerate the fluid flow and we had made an inexpensive method of or we have innovated an inexpensive method of fabricating electrodes by scratching the paper with pencil and the lead in the pencil acts like electrodes so this is called as a paper and pencil based device which is ideally suited for medical diagnostic applications because you can make in very inexpensive micro channels on paper and then you can scratch pencil on the same paper so that you get electrodes and then you can have electrokinetic flows of blood samples in a paper and pencil based microfluidic device. It requires minimal infrastructure it is very easy to fabricate and the inexpensive technique of electrode fabrication makes it ideally suited to be used in a low cost microfluidic platform. So and another interesting observation is that with electric field of course in a forward bias direction and in a reverse bias direction the capillary feeling rates are different but in either case no matter in whatever direction the electric field is applied the blood flow rate is faster as compared to that with 0 electric field and so typically with a 50 volt electric field electric voltage you can see that this is a capillary feeling characteristic with 0 volt with either forward or the reverse bias you can see that with a 50 volt you can see that the capillary gets filled up faster and therefore there will be more rapid diagnostics not only that these results with electric field are much more repeatable and therefore are much more reliable as compared to the results without electric field. Just I want to as in the previous lectures also I want to impress upon you that these studies it might appear that we are trying to innovate some technology but these technologies are strongly linked with fundamental science. So how do you link these with the capillary feeling dynamics that we have studied in one of the fundamental lectures of our microfluidics course. So you can see that you basically write reduced order model of capillary feeling you can understand various terms like this is the inertial term the left hand side and the right hand side the surface tension term the viscous term in addition to that you have an electro osmotic body force. So with this you can now address electro hydrodynamics of a capillary feeling process and instead of now you can make it more complicated by considering blood as a sample instead of like a normal Newtonian fluid as a sample. So in a porous medium which is like a paper matrix basically it may be assumed to be a bundle of capillaries and you can still use the Lucas-Warsman type of paradigm without electric field but you have to use the effective pore diameter which is like related to the hydraulic pore diameter and the capillary pore diameter. For a swelling porous medium the pore diameter is modified the porosity and the permeability change during the course of swelling. So the parameters are functions of both space and timing space and time for the swelling porous medium and for that the capillary feeling rate the capillary feeling length as a function of time is given by this formula this formula is taken from this reference which is given here. So if you are more interested in looking into the derivation of this formula you can look into this particular reference. So we have studied the transport characteristics through the paper matrix and the experimental data fits well with the Lucas-Warsman based paradigm with and without electric field depending on whether we have applied the electric field or not. Now we have used the paper based platform paper and pencil based platform for studying mixing and why mixing is important because if you have a blood sample and if you have an analyte which you want to react they must mix before they react and you can see here that this zigzag flow passages are to make sure that you actually enhance the mixing by ensuring that the fluids which pass through this passage stretch and fold. If they stretch and fold then it is possible that they mix well even in a laminar flow environment. So we had made some colorimetric detections on paper based devices. So like you have a sample pad through which the sample has to be introduced you have a hydrophilic channel through which the sample will reach the detection zone and you have a detection zone where the required reagents will be spotted. Once the sample will reach there color will be produced due to the interactions and the intensity of the pixel if it is characterized as a function of the concentration of glucose in the blood sample you can use this as a colorimetric detection platform one of course has to have a calibration the intensity as a function of concentration and one can use this calibration curve which is shown here for testing the blood glucose level of various blood samples. Not only a single test but multiple number of tests can be done on paper and pencil devices. So for example in this particular figure you see that there are several reservoirs there is a reservoir G which is a reagent for glucose detection there is a reagent reservoir B which is a reservoir for reagent for bilirubin detection and the blood sample which is a blood serum is supplied from the reservoir S. So you can see that within this platform and you apply electrical voltage in this way. So in this paper and pencil platform we have tested the blood glucose and bilirubin levels simultaneously by using a single blood sample. So this is just to demonstrate that it is possible that you can make multiple tests simultaneously using a single blood sample using the paper and pencil based microfluidics platform. Now these platforms still require chemicals can you go for medical diagnostics in a chemical free environment. What is the philosophy I will discuss more about the philosophy because this kind of works are still on the nascent stage. Now as I mentioned in my previous lecture that there are certain disease conditions which will alter the morphology of the blood sample and once the blood sample morphology is altered that means the rheology of the blood sample is also altered and that means the fluid flow conditions are altered. Therefore the fluid flow related parameters for example the burst frequency in the CD can be used as a diagnostic indicator of the possible existence of a disease. So blood rheology can be associated with a particular disease. So for example one of the important issues of blood rheology is the hematocrit or the volume percent of the red blood cells. So what we have seen that we have studied the hemo rheology that is the hematocrit variation based rheology of blood sample on a CD platform. We have seen that for a particular channel with the value of the burst frequency increases with increase of hematocrit and increase of hematocrit or decrease of hematocrit can be associated with a particular morphological condition in the blood sample. So higher the value of hematocrit we have seen that the rate of aggregation of the red blood cells is high which enhances the effective viscosity of blood. So we see that the burst frequency increases with increase of hematocrit. So the burst frequency of the CD based microfluidic platform can be taken as an indicator of the rheological aspects of the blood sample and this rheological aspect may in turn be related to certain disease conditions. Therefore by directly reading the burst frequency one may possibly think of the existence of a particular disease condition in a blood sample. Now so far in this particular lecture we have discussed about microfluidics as a diagnostic indicator but what about the medical treatment. Now there are several medical treatments which require injection and injection with standard needles. So 12 billion needle injections are performed every year for the delivery of vaccines and protein therapeutics such as insulin, growth hormones, etc. I mean there is a huge market just for drug delivery using injections. The traditional drug delivery systems require injections. So I mean these are associated with insertion pain and needle phobia from patients and typically young children. Accidental needle sticks lead to injuries and infections. Use of sharps raises concerns for device safety and safety for health and there are issues associated with HIV infection and there are actual diseases. Similarly according to WHO more than 1.3 million deaths which are attributed annually to unsafe injection practice. Now still you cannot avoid injection of drugs because many drugs they cannot actually be effective if they are orally administered because they will suffer degradation from gastrointestinal tract. So there are several existing technologies to overcome some of these limits like for example a micro jet injector in which liquid jet injectors are used as used in which compressed gas or a spring to create is used to create high pressure jets of drug solutions that deliver drugs. In pulsed micro jets it is possible to deliver protein drugs into the skin without deep penetration and one is able to deliver therapeutic doses of insulin. There are micro needles available with solid micro needles in different technologies and hollow needles where micro needles have containing hollow boards offer the possibility of transporting drugs to the interior of well defined needles by diffusion or pressure driven flow. Then there are a few other advanced technologies like ion tophoresis it refers to the delivery of drugs across the skin by means of an electric field. By having two electrodes based on the skin drugs at the electrodes will start to migrate through the screen once the voltage is applied. So it is an electrically driven drug delivery one can also have sonophoresis a method to move drugs across the screen barrier where the skin is made permeable under the influence of ultrasonic waves. So there are several limitations of these existing non-traditional technologies. In the micro jet injector spring based systems are not compatible for scaling down it cannot eliminate pain and pharmacokinetics and safety measures are not established. Many of the micro needles reported suffer from needle fracture and pressure driven flow is not an energy efficient process in microfluidic systems. In ion tophoresis there is low mass flux of intended medicines and in sonophoresis it is challenging to fabricate a scaled down sonophoretic structure with a driving circuitry and a transducer delivering an acoustic power of about 1 watt that is 120 decibel. Now to circumvent this problem one can go for an alternative technology by developing a biomimetic micro needle system. So a micro needle system that mimics a natural system of blood extraction and I will come to that in a moment but I would briefly like to discuss upon the issue of biomimetics. Now biomimetics is a heart and soul of modern day research and what it tries to do that it essentially tries to emulate certain natural living objects and make engineering devices by taking lessons from their principles of action. It is not mimicking the biological world in a true sense because biological world is very complex it is very difficult to make engineering devices exactly mimicking a biological system but basically one can take a lesson out of that here. So the whole example that I will discuss about is a research project on which we worked in collaboration with a Japanese group where I interfaced with Professor Suchiya from the University from the Tokai University at Japan located at Kanagawa. So I mean it was a wonderful experience in working in this collaborative project and because it is a collaborative project I mean it is work performed by a large number of researchers from various groups to make an integrated device and the whole idea is to design, analyze and then fabricate a microfluidic device which is like a painless micro needle for blood extraction and drug delivery. So the device is something like this it will look like a wrist watch and so the device which is the wrist watch type of device which is shown here unfortunately the movie is not working so I mean otherwise you could have seen an explored view of this. So on the back case of this wrist watch there are microfluidic needles micro needles and what these needles will do is the so basically you are wearing a wrist watch. So when there is a particular situation when you want to have your blood sample tested for the blood glucose level so what you basically do is that you actuate some mechanism in the wrist watch system I will show you the mechanism in the next slide then a small drop of blood is taken then what is the mechanism by which this is taken that is the heart and soul of this design then there is a micro there is a MOSFET based biosensor which is located in the same integrated device to which the blood sample will go and it will evaluate the amount of glucose in the extracted blood using an enzyme such as glucose oxidase. Now based on that what will happen based on that there is a smart insulin delivery system integrated with the same wrist watch type of device it will deliver insulin. Now why it is important many times actually it is very difficult for a patient to know that what is the correct amount of insulin delivery delivery necessary at that particular time based on the blood glucose level because it requires a continuous monitoring and one should not prescribe the level of insulin dosage based on some average requirement there may be significant deviation from the average requirement at different times of the day depending on the heaviness of the meals that the patient has taken and so many other things. So actually I mean if there is a over dosage of insulin there can be a critical condition when the patient can faint because of very low level of sugar in the blood sample and this hypoglycemia can be very serious and may even give rise to very critical health conditions at that condition which needs to be tackled by emergency. So in this particular device what is the advantage that you take a small drop of blood by triggering the wrist watch so basically you do not have to have a system where there is an elaborate system where blood is taken. See as a common person when I go for my blood testing and somebody comes or so called attacks me with an injection syringe that is not a very great situation that I enjoy and then we still have to live with it but here you see an example where nobody is attacking you with an injection syringe so a big part of the pain which is the psychological aspect of pain is eliminated and then there is a very rapid detection of the blood glucose level by just taking one drop of blood and then based on that there is an insulin delivery by the same wrist watch type of device so that you do not feel so much of disturbance or a perturbation going through during the blood extraction and the drug delivery process. So that is the psychological part of it but what is the engineering part of it. Let us discuss about that. So this is briefly the mechanism. So blood is extracted by the negative pressure generated in the blood extraction tank by the deflection of the biomorph PZT piezoelectric micro actuator. So you can see that there is a shape memory alloy spring and because of the deflection in the spring there is a biomorph actuator PZT actuator. If I have pointed here with the pointed you can see then this actuator gets deflected up that means a suction pressure is created and because of the suction pressure of the negative pressure the blood is sucked. So this is a beautiful mechanism by which blood is sucked by a suction pressure without necessitating a large indentation force. Then the electric current is shut off and the biospring returns the mitronitl and the pumping system to the initial position. The extracted blood is sensed by the biosensor fixed on the gold plate embedded in the lower tank of the pumping unit and the plate type working electrode is connected to the gate electrode of the MOSFET to detect the blood sugar levels from the biosensor system. So this is briefly the mechanism. Now the whole interesting story comes. Now where from we get an idea of generating a painless blood extraction and drug delivery system by creating a suction pressure. This is by drawing analogy with female mosquitos blood sampling mechanism. This is what is the bio mimetics that I talk about. So when the mosquitos sucks blood the female mosquitos labium is penetrated to the skin at the speed of 6 to 7 hertz when its head is moving like a hammer. So this is a beautiful mechanism by which the mosquitos sucks blood and many of you might argue that we never feel that it is a painless process. We feel an irritation but this irritation is more because of a chemical irritant that the mosquitos spreads on biting. It is not because of any mechanical insertion pain. So what is the mechanism that happens in the mosquitos? Just for curiosity a muscle bulb is relaxed, muscle of the mouth pump is tensed and the blood is extracted through the labium into the mouth pump. Then the muscle of the mouth pump is relaxed and the extracted blood is sent into the pharyngeal pump. Then the posterior pharyngeal bulb is loosened and the extracted blood is sent into the esophagus. So I mean if we do not want to get into the complications of this blood sampling at least we can say that the mosquitos blood pumping system is driven by negative pressure and the mechanism that I have demonstrated in the previous slide that mechanism tries to follow this principle that it tries to create a negative pressure for blood extraction or a suction pressure for blood extraction. So basically in this particular device one uses a piezoelectric micro pump for blood extraction through the negative pressure and there are the typical piezoelectricities like minus 400 or 710 picometer per volt. So in the range of 400 to 700 so about see of the order of 100s of picometer per volt that you get which is a good amount of piezoelectricity that you can essentially get. So what are the salient features of this blood extraction system? Painless operation through mimicking a female mosquitos labium for blood extraction. Now then the big question is that well the drop of blood is extracted by a painless mechanism but how is the blood transmitted through the needle? Here comes surface tension. So why do you require a microfluidic system? Because as we have started emphasizing on from our initial lectures that a microfluidic system actually will have a large surface area by volume ratio. So it has a strong surface effect and not only that that ensures that surface tension is a very significant force and nature has made things in such a way. So if you look into this diagram very interesting you look into the labium the real ACM image of a female mosquito. This is the labium of a mosquito. So this you see this is like a microchannel 30 micron dimension 30 micron diameter. So a mosquitos labium when it is mimicked in terms of fabrication not exactly but notionally in terms of the dimension what you essentially get is a system where surface tension works beautifully. So by surface tension driven capillary transport the blood is transported from one end of the channel to the other. So because of this surface tension driven flow and because of the painless mechanism of blood extraction the entire mechanism of integrated blood extraction, blood transport and drug delivery this is considered to be a painless mechanism. Of course in conjunction with the packaging in a wrist watch type of environment which makes it like a psychologically more comforting device. This is excellently biocompatible it has substantial strength to penetrate about 3 millimeter into the skin. Inventation force is in the tune of few sub Newton which may be enough to penetrate the human skin. There is a high blood extraction speed of about 5 microlitre per second typically for micro needles with inner diameters of around 50 microns. So which is close to the 30 microns of dimension of the female mosquito's labium. Now one can go for further modifications of this design one can go for even nano needles and one can use electro osmosis or electro kinetics in general in nano needles for blood extraction, drug delivery and all this. So those are emerging areas on which research is currently being devoted by several research groups and the whole target is to come up with a cost effective yet efficient and painless solution for blood extraction and drug delivery which are parts and parcels of disease detection and treatment in many of the challenging applications related to medical science and technology. So to summarize the lecture or the discussion that we had in this particular presentation the lab on a CD and paper based miniaturized device provide a new direction towards the development of inexpensive medical technologies. The high throughput screening and faster detection methodology makes it better alternative in comparison to the conventional clinical lab protocols. The frugal fabrication methodology and low volume of sample consumption and hence low cost of the devices makes it affordable towards the mass of the population. The simplicity of operation and portable nature of the devices make it functional from places having limited resources. The same devices can be used for the detection of pathogens from foods drinking water and also for the detection of heavy metal ions to monitor the quality of drinking water. So it is not just health management or the medical treatment point of view but you can also have water quality monitoring using the same technology. Alternative principles of chemicals free diagnostics can be exploited for certain diseases as I have discussed that certain diseases will alter the morphology and the rheology of the blood sample and then that will change the certain fluid flow characteristics. So fluid flow characteristics such as the burst frequency of a CD which may be obtained by having a balance of the centrifugal force and the surface tension force can be used as an indicator of the morphology may not be the detailed morphology but at least certain rheological aspects of the blood sample and if the rheological aspects as a function of the hematocrit content are giving rise to the possible indications of certain diseases then this can be used as a chemical free disease marker. Not only that one can use microfluidics not just for disease detection but also for medical treatment and we have shown that micro needles can be used for painless blood extraction and drug delivery. So to summarize I can say that bio microfluidics is a really very large area of research and it is not possible for me to discuss about bio microfluidics in just a couple of lectures. My whole idea or my whole intention was to give you some glimpse of what is bio microfluidics what are the important and outstanding research problems that people have been trying to solve using or combining microfluidics with the medical science and medical technology and what are the directions towards which we are heading in terms of research in microfluidics. Not just in fundamental in understanding the fundamental biophysics cellular bio microfluidics or DNA based bio microfluidics but also microfluidics specifically targeted towards rapid detection of certain diseases and also treatment of diseases. Thank you very much.