Dhatuki Issue 7

Dhatuki Ed. 7

April 2011

i

Dhatuki Team

Editors : Darsh Maheshwari Rahil Bharani Sourabh V. Jha

Design : Hardik Sanghavi Animesh Jayant

Inside...

Prof. R. O. Dusane HOD Dear readers, Let me wish you all a very happy 2011!

Once again we have come up with an exciting collection of articles for your reading in the form of the 7th issue of Dhatuki. This issue revolves around the very important technology demand for smart and functional materials leading to what we generally term as SENSORS. Sensing is a round the clock activity of the human body which is smart enough to respond appropriately to all sorts of stimuli as and when required. This is essentially the concept behind an intelligent and functional device. Smart materials are an inherent component of this technology and there is a huge effort across the globe to enhance the smartness and functionality of materials leading to their effective utilization in devices. Building memory into such devices is an additional feature being pursued.

In this issue we also present the excerpts of our conversation with Dr. Pravin Narwankar, our alumnus who is at Applied Materials Inc. And finally we give you a glimpse of the efforts going on in the MEMS department at IIT Bombay towards furthering the development of sensor technology. I am confident that just like the previous issues this edition of Dhatuki will also be an enjoyable read.

Interview with Applied Materials CTO Evolution of Sensor Technology Mechanical Sensors Piezoelectric Materials and Sensors Chandrayaan - I Nanosensors Research in the department Interview with our newest faculty Between the lines THIS IS A NON-PROFIT PUBLICATION. ALL ARTICLES HAVE BEEN CONTRIBUTED BY STUDENTS OF THE MEMS DEPARTMENT, IIT BOMBAY.

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Dhatuki Ed. 7 1

One-on-one with Dr. Pravin Narwankar -Geeta Monpara & Rahil Bharani A

fter you finished your B.Tech what prompted you to pursue further studies in material science?

One half of our class went for an MBA, while the other half of us who were interested in research did our masters. I had initially intended to pursue my PhD in India but my experience doing my masters wasn’t all that great. At that time I was working on High Temperature Super Conductors and there wasn’t good characterization equipment available. I had to go to TIFR to get an XRD done. We had an SEM with EDX which worked well for steel and non-ferrous metals, but wasn’t very helpful for semiconductors and ceramics. So I decided to go abroad for my doctoral studies.

Who is Dr. Narwankar?

Indian Institute of Technology, Bombay B.Tech and M.Tech Metallurgy and Materials Technology 1983 – 1989 University of California, Berkeley Ph.D. Material Science and Engineering 1989 – 1992 UC Santa Barbara Post Doctoral Researcher, Department of Materials, Research industry 1992 – 1994 (2 years) Harvard Business School Executive Education PE-VC Investing 2006 – 2006

Applied Materials Why Applied Materials?

I was interested in academics but Member of Technical Staff what I found while working at UC, Public Company; AMAT; Renewables & Environment industry Santa Barbara, was that although 1994 – 2004 (10 years) the materials science department was young, quite a few faculty Applied Materials members had a few years of indusEngineering Technology Director trial exposure and they were able to Semiconductors industry hold the class and keep the students 2004 – 2006 (2 years) interested much better than the other professors by presenting real life case studies which they come Applied Materials across during their work. They Regional CTO and Investment Manager, Applied Ventures, India Region made the course work interestPublic Company; AMAT; Renewables & Environment industry ing and motivated the students to March 2006 – Present carry out research in specific areas as required by the industries. So I thought that before going into academics I should have some industrial experience. The industry which had the best job prospects on the west coast at that time was the semiconductor Industry. I was interested in materials in general and specifically in ceramics. I realized that at Applied Materials, I would get a chance to see both sides of the world- I would get to work on developing technologies for semiconductor equipment manufacturers and also interface with semiconductor giants such as Intel and IBM and learn about electronic devices from them. Working at applied materials has given me a much broader perspective because this job requires more expertise in material science and technology than just manufacturing electronic devices.

2 Dhatuki Ed. 7 What is Applied Materials’ vision?

Whenever applied material has entered a country it has done so because it believes that in the future there is going to be a significant amount of consumer penetration in semiconductor manufacturing or solar photovoltaic manufacturing.

In order to support advanced manufacturing techniques, such as those required for semiconductors, an eco-system has to be developed, especially in countries where such manufacturing facilities do not exist. Applied Materials strongly believes in setting up this eco-system.

My specific objective for the company has been to set up research capabilities that would complement design capabilities in India. The way I’ve been trying to achieve this is by partnering with universities and research centers in India. The primary reason for this is to train man power and to develop the eco-system. IIT Bombay and IISc Bangalore were chosen by the government of India to set up two national centers for nano-electronics, and Applied Materials was invited to help set up these facilities. Applied Material donated the semiconductor manufacturing equipments for the development of these centers.

As an Applied Materials CTO what do you expect from IIT in general, and specifically from the MEMS department?

Nowadays, there are fantastic opportunities for students after their B.Tech, and for quite a few of them the family background they have and the fact that they have stayed away from home steers them towards taking up wellpaying jobs. I don’t think there is anything wrong in that.

There has been a boom in the IT industry over the last 1015 years which, fortunately or unfortunately, has attracted youngsters to join it just after their bachelors .They end up getting very good salaries, especially when they are from very good engineering colleges like IIT. I don’t expect them to join us just after their B.Tech program. Every society goes through a transition If you look around the devices that you see are made of microprocessors, flash memory devices etc., which have advanced materials in them. All these technologies have been developed by people in Ap-

plied Materials or Intel, or groups within these organizations who managed to integrate these advanced materials and extract performance. As newer such devices get manufactured there is a need for students with an engineering background.

I would encourage the students of the MEMS department, Chemical Engineering department or any other department at IIT Bombay to pursue advanced research if they are interested in contributing to the next i-Phone, or i-pod or the next big application. People can take up a job after their bachelors, do it for a few years and then they can join a master’s program for research in a particular field.

The key thing for the younger generation to understand and realize is that if you want to contribute to the advancement of new technologies, you can’t just restrict yourself to one field. Engineering and science has become more and more interdisciplinary. Students should broaden their horizons by learning about electrical or electronic devices, or chemical reactors and so on. To add value to any group or a company, you have to have interdisciplinary experience. One thing I would really recommend is that they get in touch with other faculty, which would help them understand and realize the potential of the faculty’s branch/ course. They can find out how exactly knowing a little bit of electronics or flow dynamics etc. can help them.

A message for the students.

At this time you guys have the right environment to grow. Students, who are doing their bachelors, should try and do courses outside of their core area. If you are not getting any exposure to biotechnology or energy science, or any other field which you like, you should try and do an internship or some laboratory work in that field. One of the differences I found between the US and India is that some students take jobs, make money and then join a master’s or a PhD programs. They put themselves in an area where they can actually see growth for themselves. And of course, the education system in the US allows one to do a master’s or research in any field irrespective of their bachelors.

So my message to students is to look for facilities available within IIT or outside, which can help them figure out what exactly they want to do for their masters or PhD.

Dhatuki Ed. 7 3

Evolution of Sensor Technology -Bhavna Gupta & Rishi Kumar

T

he human mind is a notoriously poor gauge of such things as weight, distance, temperature, and humidity. From time immemorial, we have been devising tools to help us obtain more accurate measurements. For example, when Noah was building his ark, the cubit (the length of the arm from the tip of the middle finger to the elbow) was a standard measurement of length, whereas present-day measurement instruments can be represented by a triptych. Any measurement requires an input transducer that converts a non-electrical signal into an electrical signal, referred to as a Sensor. These are electrical or mechanical components that are used to measure a property or behaviour of an object or system. Some sensors measure properties directly, other sensors measure properties indirectly, using conversions or calculations to determine results.

Sensors and transducers have paved the way for human development and are so deeply ingrained in our lives that we barely realize their presence. It is not possible to imagine our lives without a cell phone, speakers, and our biological sensors - smell, sound, and sight. Their evolution has been characterized by diversities both in inventions and usability. But the path of their development and evolution has never been smooth, and is marked by gruelling and ardours work done by people all over the globe. We have tried to track the evolution of sensors and transducers over the past 200 years.

The Beginning (19th century):The 1800’s saw the discovery of materials that could transduce both electric and magnetic field. Pyroelectric and piezoelectric effects were the major breakthroughs.

T.J. Seebeck developed For the next few decades, piezoelectricity remained something of a laborathe principle of a ther- tory curiosity. Tremendous work was done to explore and define the crystal mocouple structures that exhibited piezoelectricity. From the Curies’ initial discovery in 1880; it took until the 1950s before the piezoelectric effect was used for 18th century E.H. Hall discovered industrial sensing applications. Since then, the utilization of this measuring the effect in thin gold principle has experienced a constant growth and can be regarded as a mature foils Discovery of pizeoelec- technology with outstanding inherent reliability. It has been successfully used in various applications such as medical, aerospace, nuclear instrumentation, tricity took place in mobiles’ touch key pad for pressure sensing, internal combustion engines Many of these effects were later etc. The century also saw development in pressure sensors and thermocouused to generate energy, as well as ples.

in the construction of sensors

The Development Era (20th century): The development in sensors was rapid and highly diversified. Almost everything needed sensors or transducers of some sort. During World War II, the dominant transduction material was nickel. Known piezoelectric ceramic strain was relatively insignificant until around 1946, when it was discovered that barium-titanate could be electrically “poled,” a process similar to magnetizing a permanent magnet. Within the next decade, lead

1940 - 1970

1915-Paul Langevin invented the first active sonartype device for detecting submarines in water 1916-First audio speaker was deviced At the University of California, a combination of piezoelectric materials such as CdS, CdSe, and ZnO, with FET structures was engineered for detecting surface-acoustic waves 1930-First fluid analyzers was built

1954-Electroacoustic transducers 1965-First integrated silicon pressure sensor was deviced at at Bell Laboratories. The first Japanese pressure sensor was produced ,the original device being made of germanium.

Early 1970s-Capacitive pressure sensors were fabricated.

1900 - 1940

zirconate-titanate was found to have properties superior to nickel and therefore, largely replaced it in sonar and most other applications.

Modern development and future expectations: Sensor technology has evolved from the humble thermocouple to complex devices that we cannot do without. Now that the sensors find application in cameras, watches, satellite, laptops - pretty much everything, we wonder how our lives would have been without them.

4 Dhatuki Ed. 7 If you have seen “Minority Report”, you would have noticed Tom Cruise’s character controlling a computer by simply moving his hands in front of the monitor. Recently, scientists announced that they have managed to create an image sensor that would allow users to interact with various devices a similar way and track movements throughout 3D space and see pictures as 3D objects.

1975- Smart pressure sensors which had the sensor and the circuits located on the same chip were introduced in Russia 1975 -First ever accelometer(device used 1970 - 2010 to measure acceleration )was fabricated

by Vaganov. Many of the airbag sensors used in today’s cars have crash sensors based on this early device by Vaganov 2001-A laser micromachined vibrational to electrical power transducer for wireless sensing systems was developed 2005-Split core transducers.

Software giant, Microsoft, has already made a step towards the no-touch interface with its “Project Natal”.

Canestra is a company that has presented a somewhat similar technology, allowing users to change channels and adjust the volume on their TV by simply waving their hands. 3D sensors could replace ultrasonic sensors that some carmakers place in the rear bumpers to alert drivers when they are close to hitting an object or a person. Canestra also believes that the sensors could be placed inside a vehicle, replacing weight detectors when identifying whether a child is in a seat, and if an air bag should deploy. Besides this, the sensors could also detect when there is someone unauthorised in the vehicle.

We might not be around to witness the zenith of human accomplishments, but we can be sure that sensor technology will play a key role in helping us reach those heights.

Sensors to keep you awake in a car

Mercedes have developed their “Attention Assist” system which constantlty monitors the way the driver is driving. During every journey Attention Assist continuously observes the driver’s typical behaviour patterns and uses these to create an individual driver profile which serves as a basis for recognising the symptoms of tiredness. The values recorded by the tiredness recognition system not only include the speed and the longitudinal and lateral acceleration but also the angle of the steering wheel, the way that the indicators and pedals are used, certain driver control actions and various external influences such as a side wind or an uneven road surface. Once the system recognises drowsiness in the driver, a warning is sounded and a “coffe cup” symbol lights up in the instrumentation panel!!

Mechanical Sensors

Dhatuki Ed. 7 5

-Darsh Maheshwari

M

echanical sensors measure physical quantities, which need not be mechanical in nature, but the process to measure them is mechanical. For example, temperature measurement can be done by measuring changes in volume of a confined gas.

Mechanical sensors mainly include the following: • force sensors • accelerometers • pressure sensors • gyroscopes Force sensors: Strain can be related to stress, force, torque and a host of other stimuli including displacement, acceleration or position. Strain gauges are often used for bending strain, twisting (torsional and shear strain) and longitudinal tensioning/ deformation (axial strain) of structures (engine shafts, bridge loading, truck weighing and many many others). Any material, combination of materials or physical configuration that changes its resistance due to strain constitutes a strain gauge.

Metallic strain gauge: consists of a wire stretched. When a force is applied, its length increases proportionately, the increase in length and decrease in cross sectional area causes the resistance to increase.

Semiconductor strain gauge: Semiconductors show a Googled Web Image

larger change in resistivity for the same strain. Hence, they can be smaller and more accurate. Their use is limited to low temperatures. These can be much less expensive than metal strain gauges.

One of the important differences between conductor and semiconductor strain gauges is that semiconductor strain gauges are essentially nonlinear devices with typically a quadratic transfer function. ∂R∕R = S1e + S1e2

Tactile sensors: The definition of “tactile” action is broader, the sensors are also more diverse. One view is that tactile action as simply sensing the presence of force. Then: • A simple switch is a tactile sensor • This approach is commonly used in keyboards • Membrane or resistive pads are used • The force is applied against the membrane or a silicon rubber layer.

• These are usually made from piezoelectric films which respond with an electrical signal in response to deformation The simplest tactile sensors are made of conductive

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polymers or elastomers or with semiconductive polymers called piezoresistive sensors or force sensitive resistive (FSR) sensors. The resistance of the material is pressure dependent.

Accelerometers: Magnetic methods and electrostatic (capacitive) methods are quite commonly used. The distance between the mass and a fixed surface, which depends on acceleration can be made into a capacitor. Capacitance increases (or decreases) with acceleration. A magnetic sensor can be used for measuring the field of a magnetic mass. The higher the acceleration, the closer (or farther) the magnet is from a fixed surface and hence larger (or lower) is the magnetic field.Methods of acceleration sensing start with the mechanical model of a mass. The mass, moves under the influence of forces, has a restoring force (spring) and a damping force (which essentially prevents it from oscillating).

The uses of accelerometers are vast and include air bag deploying sensors, door unlocking, weapons guidance systems, vibration and shock measurement, satellites, intru-

6 Dhatuki Ed. 7 Googled Web Image

sion alarms (by detecting motion), and control and other similar applications.

Pressure sensors: These sensors are used either in their own right, (to measure pressure), or to sense secondary quantities such as force, power, temperature and the like. One of the reasons for their prominence is that in sensing gases and fluids, force is not an option – only pressure can be measured and related to properties of these substances.

The Bourdon Tube: The Bourdon tube is in the shape of the letter “C” and is welded or silver-brazed to the stationary base. The free end of the tube is connected to the indicating mechanism by a linkage assembly. The threaded socket, welded to the stationary base, is the pressure connection.

When pressure enters the Bourdon tube, the tube tends to straighten out. The tube movement through linkage causes the pointer to move proportionally to the pressure applied to the tube. The simplex gauge is used for measuring the pressure of steam, air, water, oil, and similar fluids or gases.

Diaphragm: One side is held fixed (in this case by the small screw which also serves to adjust, or calibrate it). The other moves in response to pressure. The device is hermetically sealed at a given pressure. Any pressure below the internal pressure will force the diaphragm to expand

• •

(like a baloon). Any higher pressure will force it to contract. Very simple and trivially inexpensive, but: • Possibility of leakage • Dependence on temperature.

Pressure sensors come in four basic types: • Absolute pressure sensors (PSIA): pressure sensed relative to absolute vacuum.

• Differential pressure sensors (PSID): the difference between two pressures on two ports of the sensor is sensed. t sensors (PSIG): the pressure relative to ambient pressure is sensed.

Sealed gage pressure sensor (PSIS): the pressure relative to a sealed pressure chamber (usually 1 atm at sea level or 14.7 psi) is sensed.

If the cavity under the diaphragm is hermetically closed and the pressure in it is P0 , the sensor becomes a sealed gage pressure sensor sensing the pressure P-P0 . A differenGoogled Web Image

tial sensor is produced by placing the diaphragm between two chambers, each vented through a port. The deflection of the diaphragm constitutes a capacitor in which the distance between the plates is pressure sensitive.

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Gyroscope: Used as stabilizing devices in aircraft and spacecraft, and in such applications as auto-pilot. They are much more common than one can imagine. The gyroscope is a navigational tool. Its purpose is to keep the direction of a device or vehicle constant. They are used in all satellites, in smart weapons and in all other applications that require attitude and position stabilization.

They have already found their ways into toys. The basic principle involved is the principle of conserva-

Dhatuki Ed. 7 7 tion of angular momentum: “In any system of bodies or particles, the total angular momentum relative to any point in space is constant, provided no external forces act on the system”

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It consists of a rotating mass (heavy wheel) on an axis in a frame which provides the angular momentum. If one tries to change the direction of the axis, by applying a torque to it, a torque is developed in directions perpendicular to the axis of rotation. This forces a precession motion proportional to the torque applied to its frame. Coriolis acceleration has been used to devise much smaller and more cost effective gyroscopic sensors. These are built in silicon by standard etching methods. The rotating mass is replaced by a vibrating body The coriolis acceleration is used for sensing.

Piezoelectric materials and -Sneh Vaswani sensors I

ntroduction : Piezoelectricity - etymologically, it comes from the greek “piezo” meaning to press or squeeze. Piezoelectric materials are those which produce a potential difference or electric field on application of mechanical stress.It is seen mainly in polar materials and is related to polarization density in the material.The effect is reversible,in the sense that these materials change shape when exposed to electric potential The mechanism behind this effect is the change in polarization vector P, due to the reorientation of molecular dipole moments when stress is applied.The change in P results in change in surface charge density and hence electric field on crystal faces .

Structual Properties of Piezo Crystals • Polar crystal classes: 1, 2, m, mm2, 4, 4 mm, 3, 3m, 6, 6 mm.

• Piezoelectric crystal classes: 1, 2, m, 222, mm2, 4, 4, 422, 4 mm, 42m, 3, 32, 3m, 6, 6, 622, 6 mm, 62m, 23, 43m.

• Polar classes already have a dipole moment when stress is zero,but this is changed on application of stress.The others show dipole moment only on application of stress.

Piezo Materials : Perovskites such as BaTiO3, PbTiO3 and others like LiTaO3 are ceramic piezoelectrics. Natural materials such as bones, tooth enamel, tendons, silk etc. also show this effect, and so do topaz and quartz.

Application in sensors: Though the piezoelectric effect was discovered in 1880,it wasn’t before 1950 that it was used in sensor technology.

The main application lies in measurement of pressure,force and acceleration. Since the voltage difference generated in piezoelectric materials is very small, it is amplified, using operational amplifiers or other amplifier circuits, to show the final sensor output.

Some advantages of piezoelectric sensors are that they are rugged, have an extremely high natural frequency and an excellent linearity over a wide amplitude range. Additionally, piezoelectric technology is insensitive to electromagnetic fields and radiation, enabling measurements under harsh conditions. Some materials used (especially gallium phosphate or tourmaline) have stability over extreme temperatures, enabling sensors to have a working range of up to 1000°C. Pressure sensors: Here, the “crystal” is generally a piezoelectric quartz element. These crystals generate an electrical charge when they are strained. Piezoelectric pressure

8 Dhatuki Ed. 7 Googled Web Image

acceleration (y’’). This makes it uniquely insensitive to the earth’s gravitational field, thus simplifying installation by avoiding precise alignment usually needed for other acceleration (y’’) based transducers. The electronics contained in it integrates the jerk (y’’’) signal and generates the desired velocity (y’ ) or displacement (y) output as a 4-20mA signal. The 4-20mA signal can be monitored externally with any computer monitoring system, chart recorder, or by an optional stand alone threshold detector.

sensors do not require an external excitation source and are very rugged. The sensors however, do require charge amplification circuitry and very susceptible to shock and vibration. Also piezoelectric sensors are not suitable for detecting static loads as the voltage induced decays off very quickly in that case.

Their main applications: • Dynamic strain gauges • Vibration sensors for alarms, switches, speakers, and contact microphones • A robust, versatile vibration sensor for continuous monitoring of rotating equipment such as large motors, fans, conveyors, etc

Embedded Systems : A crystal oscillator is a passive electronic device used in many microcontroller based applications to provide a stable and precise clock signal. It uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a very precise frequency. This is also used in quartz wristwatches and to stabilize frequencies for radio transmitters and receivers. Quartz is the most common material used here. It is way more accurate than a ceramic oscillator and is very resistant to temperature changes. The accuracy is of prime importance, especially when we have very high performance computing applications.

A unique and important feature of the vibration sensor is that it responds to “jerk” - technically the third derivative of displacement with respect to time (y’’’) - rather than

Piezoelectric sensors have become ubiquitous, and serve a wide range of applications including nuclear, aerospace and medical technologies.

10 Dhatuki Ed. 7

The Chandrayaan - I Moon Impact Probe

Sub KeV Active Reflecting Analyser (SARA) SARA will image the Moon surface using low energy neutral atoms as diagnostics in the energy range 10 eV - 3.2 keV. It will Image the Moon’s surface composition including the permanently shadowed areas and volatile rich areas and it will solar wind- surface interaction as well as surface magnetic anomalies. The SARA instrument consists of neutral atom sensor CENA (Chandrayaan-1 Energetic Neutrals Analyzer), solar wind monitor SWIM, etc

The primary objective of MIP was to demonstrate the technologies required for landing a probe at the desired location on the moon. Through this probe, it was also intended to qualify some of the technologies related to future soft landing missions. This apart, scientific exploration of the moon at close distance was also intended using MIP. MIP consists of 3 instruments radar altimeter, Video imaging system and Mass spectrometer based payload (CHACE).

High Energy X-ray Spectrometer (HEX) High energy X-ray spectrometer-It is designed to help explore the possibility of identifying Polar Regions covered by thick water-ice deposits as well as in identifying regions of high Uranium and Thorium concentrations. HEX uses Cadmium Zinc Telluride (CZT) detectors. CdZnTe (CZT) is a room temperature semiconductor that directly converts X-ray or Gamma-ray photons into electrons. CZT is a unique semiconductor compared with Silicon and Germanium detectors, in that CZT operates at room temperature and can process >10 million photons / second /mm^2. Additionally, CZT’s spectroscopic resolution clearly out performs any commercially available Scintallator.

HySI (Hyper Spectral Imager) It has a CCD camera designed to obtain spectroscopic data. HySI combines information coming from a digital picture with that of a spectrophotometer to give a hyper-spectral cube. It is used for mapping minerals on the surface and for understanding the mineralogical composition of moons interior

Miniature Synthetic Aperture Radar (Mini-SAR) To detect water ice in the permanently shadowed regions on the Lunar poles, upto a depth of a few meters. An onboard SAR at suitable incidence would allow viewing of all permanently shadowed areas on the Moon, regardless of whether sunlight is available or the angle is not satisfactory.

The radar would observe these areas at incidence angle near 45 degrees, recording echoes in both orthogonal senses of received polarization, allowing ice to be optimally distinguished from dry lunar surface.

Spacecraft

Dhatuki Ed. 7 11 It is India’s first unmanned lunar probe. The Chandrayaan-1 mission is aimed at highresolutiton remote sensing of the moon in visible, near infrared (NIR), low energy X-rays and high-energy X-ray regions.

-Sourabh V. Jha & Rahil Bharani

RADOM (Radiation Dose Monitor)

RADOM is a miniature spectrometer-dosimeter containing one semiconductor detector of 0.3 mm thickness, one charge-sensitive preamplifier and two micro controllers. The detector weighs 139.8 mg.

Pulse analysis technique is used for obtaining the deposited energy spectrum, which is further converted to the deposited dose and flux in the silicon detector. The exposure time for one spectrum is fixed at 30s. The RADOM spectrometer will measure the spectrum of the deposited energy from primary and secondary particles in 256 channels.

Smart Near Infrared Spectrometer (SIR-2) Smart Near Infrared Spectrometer (SIR-2), aims to study the lunar surface to explore the mineral resources and the formation of its surface features.

It is an Indium Gallium Arsenide photo diode. SIR-2 collects the sunlight reflected by the Moon with the help of a main and secondary mirror. This light is led through an optical fiber to the instrument’s sensor head where it hits a grating. The light dispersed by the grating ultimately reaches a detector which consists of a row of photosensitive pixels which measure the intensity of the dispersed light at the different wavelengths and produces an electronic signal which is read out and processed by the experiment’s electronics. SIR-2 will attempt to improve upon SIR, mainly by using a detector with an embedded thermoelectric cooler and a digital controller to keep the detector temperature stable. This will stabilize the dark current noise, making it simple to subtract it since it will have an almost constant level.

Terrain Mapping Camera (TMC)

M3 Moon Mineralogy Mapper The primary scientific goal of M3 is to characterize and map lunar surface mineralogy in the context of lunar geologic evolution.

This translates into several sub-topics relating to understanding the highland crust, basaltic volcanism, impact craters, and potential volatiles. It measures solar reflected energy, using a two-dimensional HgCdTe detector array.

It’s main objective is to map topography with high spatial and elevation resolution. The main component is CCD. This is a semiconductor device with epitaxial layer of silicon, doping of boron and phosphorous done by ion implantation, poly-silicon gates instead of aluminum, deposited by CVD. This is because aluminum gate would limit the array size and polysilicon is transparent to incoming wavelength allowing front side illumination. It has a higher Quantum Efficiency compared to photographic media.

PRIME OBJECTIVES

Search for water-ice

Chemical Mapping

Mineralogical Mapping Topography Mapping Radiation Environment Magnetic Field Mapping Volatile Transport

Lunar Atmospheric constituent

PAYLOAD MiniSAR, HEX, SARA C1XS, HEX HySI, SIR-2, M3 LLRI,TMC RADOM, HEX, C1XS SARA HEX MIP

12 Dhatuki Ed. 7

Nanosensors -Sourabh V. Jha

A

lthough they are invisible to the naked eye, engineered nano scaled material made for such common substance as metal-oxide, polymers, ceramics and novel carbon derivatives (e.g. carbon nanotubes) demonstrate many desirable physical properties. For example, compared to their macro-scaled counterparts nanomaterials may offer greater reactivity, optical absorption and catalytic efficiency; increased electrical conductivity, hardness, wear resistance, strength and retardancy; and improved barrier and magnetic properties. These unique properties confer performance advantages in a wide range of sensing application.

With their small size, light weight and large surface area, such engineered structures have been shown to improveby orders of magnitude- the sensitivity, selectivity and response time of sensor technology. This provides an advantage over slower, more costly, laboratory-based analytical methods. It also dramatically reduces the size, weight and power requirements of the resulting monitoring device compared to conventional, micro-scaled alternatives.

These unique properties of nano-material can be used to make various nano-sized sensors such as Biosensors, chemical sensor, peizosensors, etc. Few examples of nano sensor used in different field are mentioned below.

Bio Nanosensors • Nanosensors in virology: Quantum dots encapsulated in the protein of a virus can enter the mammalian cells in the same way as the complete virus offering better understanding of pathogen host interaction.

• A special tattoo ink that changes colour based on glucose levels inside the skin is under development by Massachusetts-based Draper Laboratories. The injectable nanotech ink could eventually free diabetics from painful blood glu-

cose tests.

• Fast and efficient way to detect bacteria in the body: The nano-sensor used is a hairpin-shaped strand of DNA, complementary to the genetic sequence being targeted, that is fixed on a gold film. Gold quenches the glow of a fluorescent molecule (Quantum dot) attached to one end of the DNA. The DNA stays folded over until a target genetic sequence links to it. Its unfolding results in the fluorescent molecule moving away from the gold film and glowing, which can be seen under a fluorescent microscope.

• Improved magneto-nano sensor chips are up to 1,000 times more sensitive than current methods of cancer detection - can scan any bodily fluid with high accuracy and search for up to 64 different cancer-associated proteins simultaneously.

Chemical & Mechanical Nanosensors (peizo nanosensors) At a nano scale Nanosensors uses mechanicals properties to detect chemicals. These are based on micro and nano cantilevers which look like tiny beams or diving boards with one side coated with chemical to attract and bind the target molecule. When molecule of interest bind to them these small structure deflect and deflection are detected either by laser light correlated to detectable shifts in other physical properties of the beam. For example Piezoelectric crystals produce electrical signals(voltages) when sublected to mechanical stresses. Nanomechanical sensors have been considered an ideal platform for detection of explosives.Molecular adsorption of vapour on the surface of the cantilever, results in bending of cantilever structure, which is used to detect the presence of explosives.

A sensor to sniff out dangerous gases: A tiny carbonnanotube-based chemical sensor can detect low parts-

What are Quantum Dots?

They are florescent semiconductor nano crystals(~100nm) They are generally made of materials: CdSe, CdS, CdTe and InGaP Their general property is emission of light of different colours on electrical excitation depending upon their size Applications: colour coding and tracking different cell process, providing high resolution cellular imaging, observation of individual molecule and the ability to track different stages of cancer labels for detection of DNA immunosensing of disease biomarker, detection of bio-warfare agent

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Researchers at Purdue University have shown that common bacteria can deliver a valuable cargo of “small nanoparticales� into a cell to precisely positioned sensors, drugs or DNA for the early diagnosis and treatment of various diseases.

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per-billion concentrations of gases. It can also go from detecting one gas to another within half a minute. Typically, carbon-nanotube- or -nano based sensors, which can be extremely sensitive in detecting gases, take hours to recover and be reused. Various gases are separated using a gas chromatograph (channels etched out on a silicon chip).

Different gasses pass at different rate in the chromatograph, on the other side is a carbon nano tube on which the gases are absorbed changing its conductivity.

nano piezoelectric crystals powering nano components for sensors. Most macro chemical sensors are optimized for the detection of a single chemical species. By comparison, many nanosensor designs are able, not only to detect the target chemical but also distinguish between different chemicals in a single stream. This multiplexing capability offers a vast improvement for real time chemical exposure monitoring and disease identification. Each nanosensor is tuned for a different agent-using a mix of nanowires or tubes that contain different chemical coatings or function Most nano sensors derive their power from macro al groups, as a result of chemical or physical differences. power sources. A breakthrough project aims at having Among the many challenges is the need to perfect cost effective, reResearchers at Stanford have created producible Googled Web Image a kind of inexpensive sensor based on fabrication method that carbon nanotubes (these things are so can ensure handy!) that can detect the traces of TNT the desired and the nerve agent Sarin in water. This composition, can be useful to detect terrorist attacks structure and on the water supply or leaching from purity, lower munition making or storage facilities, the cost of enthis type of sensor could also be used to gineered nano detect other kinds of toxins and help us materials and track down polluters. increase the production

14 Dhatuki Ed. 7

Tactile Sensor

Assembly

Encoder

Virtual CNT Arrays

Manipulation

Robotics Measurement

Solid State Physics

Science Molecular Biology

MechanoChemistry

NEMS

Lateral Emitter Arrays Nano Linear Servo Motor

Lateral CNT Arrays

Force Sensor

Nano Spring Nano Electromagnet

Nanocoils Nano Coils

Telescoping CNTs Googled Web Image Googled Web Image

yield in order to drive down cost. For some classes of nano sensors, scale-up of production remains a major issue.

So far, nanosensors have been an evolution, not a revolution. Let us see what the future has in store for us.

Potential applications for nanosensors in oil and gas industry NANOSENSORS FOR OCEAN MONITORING To address the growing need for comprehensive information about our marine environments the Wealth from Oceans Flagship is exploring the development of new nanochemical hydrocarbon sensor technologies to detect and discriminate between different hydrocarbons. A key application for this technology is the detection of hydrocarbon seeps which may indicate as yet untapped hydrocarbon resources, such as oil and gas, beneath the sea floor.

Dhatuki Ed. 7 15

Research in the Department...

Currently our Department’s research related to sensor materials are as follows:

Thin film neutron Sensors: Currently Prof. R.O. Dusane is working on the development of HW- CVD Boron Carbide thin film from orthocarborane for neutron detection application. Thin film neutron detectors are composed of a series of silicon based semiconductor diodes with a thin contact layer, upon which Neutron sensitive material (10B) is deposited, where neutrons are absorbed releasing charged particle reaction products in the opposite directions. One of these enters the semiconductor diode detector leading to measurement of neutron amount.

Conducting Polymer based Ammonia Sensors: Prof. Ajit Kulkarni and Prof. Srinivasa have worked on a conducting polymer based ammonia sensor. The material used was a polymer blend. Polymer blend is a class of material analogous to metal alloys, in which two or more polymers are blended together to provide a material with different physical properties. These are generally conducting, producing Sodium ions. It senses change in Thin film coated semiconductor neutron ammonia concen detector tration. This technology was transferred to Technovation Analytical Equipment.

Ltd.,Thane.

Megnetronic Sensors: Prof. N. Venkataramani is involved in the development and study of various ferrimagnetic and electronic materials, and has found various structure property correlations in nanocrystalline Gas sensor calibration set up systems.

Prototype Ammonia Sensors On the basis of these studies, the goal is to shift research from these basic materials to the application of these materials to advanced devices like sensors. These materials are generally ferrites (ferrimagnetic ceramic material) and Barium Titanate (ferroelectric ceramics), having piezoelectric properties. These sensors sense electric and magnetic fields and are made by magnetic thin film deposition. The thin film deposition process of piezoelelctric ceramics is generally done by tape casting.

MEMS Research @ME&MS Cantilever type MEMS device development, particularly the materials with the desired properties for such devices has been carried out to a large extent in the ME&MS dept. Materials required to make sensors for sensing very small forces have been developed successfully. These consist of the high gauge factor piezoresistive thin film and the structural material required for the fabrication of thin film MEMS devices.

Piezoresistive Âľc-Si:H Thinstresses films on silicon Piezoresistance is defined as the fractional change in bulk resistance induced by small mechanical applied to a

16 Dhatuki Ed. 7 material and is quantified in terms of gauge factor, which is defined as the fractional change (R/R0 ) in the resistance per unit strain (e), G = (R/R0) / e This change in resistance arises from two effects: 1. The change in the dimension of the resistor, and 2. The change in the resistivity of the material itself In semiconductors, the resistivity change is larger than the dimensional change by about a factor of 50. This change in resistivity is due to the change of the energy gap though to a very small extent. The number of carriers and hence the resistivity, therefore changes. Crystalline silicon and poly-crystalline Si made by conventional CVD show large gauge factors.

However there is a need for developing thin films with high gauge factor at low processing temperature. There has been a lot of work done in this direction by employing both conventional PECVD as well as the HWCVD deposition technique.

Gauge factors of the order of 25 have been achieved in HWCVD p-type Âľc-Si:H films. However there is a lot yet to be done in terms of getting higher gauge factors and lower substrate temperatures.

Set up fabricated for gauge factor measurement

Dhatuki Ed. 7 17

People Face-to-face with our -Rahil Bharani faculty & Sourabh V. Jha Professor M. P. Gururajan Guru sir as he is fondly called, spent a year teaching at IIT Delhi and 2 yrs at northwestern University, Il. Guru sir did his PhD. on problems of elastic stress effects on microstructural evolution (growth kinetics, thin films, rafting, and phase inversion), grain growth, and point defects in B2 ordered alloys. Here’s what he has to say...

What are your research interests? What motivated you to get into research?

My research interests are in theelastic stress effects on microstructures. My future research plans include research on solidification microstructures of magnetic materials. My getting into research was accidental, I wanted to do a B.E. but didn’t’. I got an offer from IISc to do an M.Sc. (engineering). After my M.Sc., I wanted to do a PhD. After my PhD I was pretty sure what I wanted to do.

What difference do you see between engineering undergraduates and students who are pursuing pure sciences?

Pure science students are only concerned about the “what”. Engineering students worry about – ‘why’ something happen, ‘how’ it happens and what the best way of doing things is. Some students in my class are more interested in ‘why?’. Engineering students have to go beyond just the curiosity. They need to be innovative and more creative. This is generally not there in our system. We don’t work with our hands, so we don’t think. We need to do things ourselves, and until we don’t, things will not change.

How has the experience been with the students the rest of the faculty? What expectations do you have from the students and the department?

I came because the social life here is better - both technically and non-technically. Technically because, in IITDelhi I was in the Department Applied Mechanics, while now I am in a Materials Science department. Whenever I talk to people here they are genuinely interested, and likewise for me when they have something to say. Socially, this place is very good. I have friends and few colleagues who have all joined at the same time. I have known Professor Preeta Pant from when she had come to give a talk while I

was still a student.

You have been at the Department of Materials Science and Engineering, Northwestern University. How do the students at IIT (here and in Delhi) compare with those there?

I don’t see any difference in the students except for attitude, and that is because over there they pay for their education through their noses. If you pay that kind of money, you would be very conscious of what you get in return.

This brings about seriousness. If they come to class but don’t learn anything worth their while, they will get terribly upset. There are a lot of things to do outside, and if they are forgoing those things for sitting in a class, they expect something in return which is equally exciting. Our students do not realize this. Our students over there perform equally well and develop the same attitude.

What is your view on the mandatory attendance requirements?

The attitude is the other way around. The students should demand that the faculty come for all classes and don’t miss lectures. Abroad, the money you earn or the job that you get is not related to what you study. An education degree is not a passport to life, but here it is.

18 Dhatuki Ed. 7 People abroad have freedom to learn whatever they choose and it gives them a broader overview. A very few here people actually follow what they wish to do because they are too worried about the branch they are in. Abroad when people move from their field of study to their eventual profession they carry forward their knowledge and apply it where they go. This does not happen here. We don’t carry forward anything with us.

You did your PhD from IISc. What made you come to IITs? Because I wanted to teach.

What message would you like to give to the students of MEMS? Everyone should enjoy what they are doing, and they should do it sincerely.

Professor Ajay Singh Panwar Professor Panwar graduated from our MEMS dept in 2000.

After doing his PhD from the University of Minnesota, and postdoctoral studies from University of Massachusetts, Amherst, he returned to IITB to teach.

How does it feel being a colleague of the professors who once taught you?

There is a lot of familiarity because I was coming back to the same department and all the people here received me really well. Everyone here made me feel very comfortable, especially from the faculty’s side. It’s nice when you find that the professors still remember you.

What differences do you see in IITB and its students from nine years ago? How has becoming a professor after being a student changed your perspective?

On the surface there’s a lot of change - new construction and infrastructure, the numbers have grown. The strength of the class at our time (only a B.Tech program) was 42 students.

This brings in a lot of challenges in terms of delivering your course material. One aims to reach out to as many students as one can. From our side the emphasis is on delivering concepts and making sure everyone understands them. As a student, I always asked myself if what I was studying was going to be useful to me in the future or not.

And the answer is, probably no. There may be no direct application (if you don’t take up a core job), but there are other things that you learn in the class, for example sincerity and teamwork.

What made you pursue a career in teaching?

I have always been excited by technology. I am interested in research and I feel that being in an academic environment is the best way to do research. It gives you a certain amount of freedom over what you want to work on. At the same time we are also teaching students. There’s a big advantage in teaching because your concepts are constantly

refreshed and you are able to motivate a new generation of researchers.

What interested you in your specialization?

I was interested in understanding the different materials and the principles behind the way they behave.

We study a lot of hard materials (meta l s , ceramics) in our curriculum here. Polymers always interested me. They show different kinds of behavior. The kind of problem I was working on had applications in biotechnology. It is booming commercially, and at the same time people are applying all knowledge which exists on advancing this field. It offers a lot of avenues for research and growth.

How has the experience of teaching the students been?

How do they compare to those you encountered abroad?

The class has been good, and has been challenge at the same time. It is given that IIT students are good, and there is no denying that. In terms of student response, I feel that the challenge is to get them more interested. With the kind of curriculum we have, we are in a very good position having done a wide variety of subjects - both in terms of engineering and science.

You were a student not very long ago. How has teaching changed?

Multimedia has become an important part of the classroom experience. The class has to be made more interac-

Dhatuki Ed. 7 19 tive. There needs to be a balanced delivery of knowledge in a traditional, conceptual way. At the same time get the class needs to be made more excited about the applications of engineering.

Professor Sudhanshu Mallick Prof Mallick did his B.Tech from IITB in 2000. He did his Masters and PhD from Purdue and then worked at Intel.

What are your research interests?

I am working on piezoelectric ceramic processing. My work is mainly experimental.

You worked at Intel for four and a half years. What made you switch to teaching here at IIT? Family was one of the big reasons. I did my Masters and PhD in USA, and then I was at Intel for about 5 years. So, I have been abroad for around 10 years. I figured it was time to come back. I just wanted to go back to research and explore more, and IIT seemed to be the right place.

How different is the work at Intel from research at IIT? Intel has segregated their research component and their manufacturing unit. The place where I was working had high volume manufacturing. The research done there is also a part of troubleshooting and how one process interacts with another. It is completely different from what we do here. Both IIT and Intel have their unique features.

How is being a professor different from being a student?

It is a different kind of feeling to be on the other side of table. I think when you start doing your Masters and PhD you start to develop a different approach towards tackling a problem. That is the time you get a bit serious. It doesn’t mean that students here are not serious - they are fun lov-

ing, they enjoy life and they enjoy academics How has the teaching experience been?

It has been a really good experience interacting with the students; they are very knowledgeable and enthusiastic.

What message would you like to give to the students of MEMS, IIT? Guys, work hard and be good at whatever you do. There is no limit to what you can achieve.

20 Dhatuki Ed. 7

Between the lines ...

Darsh Maheshwari & Animesh Jayant

The Department Trip Murphy’s law in action

Anatomy of a Tutorial Group

By Kumar Kislay The Maggu

The Slogger

The Scavenger

The Freeloader

Padarth ‘11 -Akarsh Rai

Overall Co-ordinator - PADARTH 2011 Padarth is the technical festival of The Metallurgical Engineering and Materials Science Department. The theme for this year’s Padarth was “Go Green!” and a variety of events, from “Make your colours, colour your T-shirt”, to lectures on ocean energy and an exhibit by Thunk in India on making useable products out of waste brought this out.

A special “Chai and Why?” session was conducted by Prof Arnab Bhattacharya from TIFR with cool facts and demos which showed the journey of artificial lighting with advances in materials, from kerosene lamps to ultra-bright LEDs. This year, Padarth saw a plethora of lectures on a wide variety of subjects: Smart materials, Mathematical modelling among others, gripping workshops on Forensic sciences, non-newtonian fluids and a series of riveting competitions varying from Business Plans to Materials Quiz. These workshops provided a whole new insight into some commonly observed events and made the participants see the logic and reasoning behind it all. The subsequent hands-on session made the whole experience even more rewarding.

Padarth 2011 was held on the 5th & 6th of March. A series of pre-Padarth online quizzes were held as a prequel to the main event and witnessed huge participation by students of both IIT Bombay and outside. Innovative publicity, excellent visibility and tempting cash prizes meant that there was a buzz around the institute even before the commencement of Padarth 2011. Newspapers carried articles on the various exhibits on display attracting huge crouds from outside the campus too.

We had a story about materials to tell and there was something fascinating for everyone here. Bike enthusiasts went crazy with the legendry Harley Davidson motorcycles on display and true blue Royal Enfield fans were treated to an inside view of the parts of the bike.

Kids had a day out at the walk on water exhibit as volunteers explained how the amazing phenomenon worked. The competitions witnessed a huge turnout with students; be it UGs, PGs or PhDs participating enthusiastically. All the competitions, be it MetaEntrepreneur – Materials B-Plan Competition, MetalliQa-The materials Quiz, The Perfect Pitch and Junkyard Wars saw the competitors fighting tooth & nail to impress the judges and the audience alike. The Materials Quiz has traditionally been the major attraction at Padarth and the excitement and participation was no less this time. More than 80 students participated in teams of 2 in the elimination round out of which the top 6 teams were selected for the finals. A brand new format and some interesting rounds made sure that the finals were keenly contested and enjoyed by the finalists with the result going down to the wire.

In addition to these traditional competitions, this year Padarth 2011 included a couple of informal events. The Materials Scavenger Hunt was a unique all-night Scavenger Hunt with “materials” as the underlying theme. In keeping with tradition, this year’s departmental panel debate saw an animated debate amongst the faculty and the student panellists.

ONGC was the title sponsor with Canara Bank as the associate sponsor. Events were sponsored by the Standard Group and Bombay 76 with Freecharge as the online partner. Padarth 2011 has been a huge success. The participation, organization of the events, enthusiasm and the level of competitions was better than the previous editions of Padarth. A solid platform has been laid for the future editions of the event. We eagerly await Padarth 2012 and hope that it is bigger and better than ever before.