AC 2012-3392: DEVELOPMENT AND GROWTH OF AN UNDERGRAD-UATE MICRO/NANO ENGINEERING LABORATORY COURSE

Dr. Benita M. Comeau, Massachusetts Institute of Technology

Benita Comeau is a Technical Instructor in the Department of Mechanical Engineering at the Mas-sachusetts Institute of Technology, where she teaches a laboratory course on nano/micro engineering.She is a Chemical Engineer and received her B.S.E. from the University of Michigan and her Ph.D. fromthe Georgia Institute of Technology. She was an NSF Research Fellow and a member of the GeorgiaTech Student and Teacher Enhancement Partnership (STEP) GK-12 program. Before graduate school,she worked as a Product Engineer for Procter & Gamble and Agere Systems. Her interests include fabri-cation and materials at small scales, product design and development, and exploring ways to enhance howstudents experience and learn engineering and science.

Prof. Rohit Karnik, Massachusetts Institute of Technology

Rohit Karnik is d’Arbeloff Assistant Professor of mechanical engineering at the Massachusetts Institute ofTechnology, where he leads the Microfluidics and Nanofluidics Research Group. He obtained his B.Tech.degree from the Indian Institute of Technology, Bombay, in 2002, and his Ph.D. from the University ofCalifornia, Berkeley in 2006 under the guidance of Prof. Arun Majumdar. After postdoctoral work withProf. Robert Langer at MIT, he joined the Department of Mechanical Engineering at MIT in 2007 asAssistant Professor. His research focuses on the physics of micro- and nanofluidic flows and design ofmicro- and nanofluidic devices for applications in healthcare, energy systems, and biochemical separationand analysis. Among other honors, he is a recipient of the NSF Career Award (2010), Institute SilverMedal (IIT Bombay, 2002), and Keenan Award for Innovation in Undergraduate Education (2011).

Prof. Sang-Gook Kim, Massachusetts Institute of Technology

Sang-Gook Kim received his B.S. degree from Seoul National University, Korea, M.S. from KAIST, andPh.D. from MIT. He held positions at Axiomatics Co. and Korea Institute of Science and Technology from1986-1991. He joined Daewoo Corporation, Korea, in 1991, as a General Manager and then directed theCentral Research Institute of Daewoo Electronics Co. as a Corporate Executive Drector before he joinedMIT in 2000. His research and teaching at MIT has addressed the issues in bridging the gap betweenscientific findings and engineering innovations, developing novel manufacturing processes for newly-developed materials, and designing and realizing new products at micro- and nano-scales.

c©American Society for Engineering Education, 2012

Development and Growth of an Undergraduate Micro/Nano Engineering Laboratory Course

Abstract Manufacturing and innovating at the micro/nano scale is a major trend in technology development. Whether in the traditional submicron manufacturing systems associated with electronic devices or in emerging areas such as biotechnology and energy harvesting, micro/nano systems are becoming increasingly important and prevalent.1-2 This paper describes how engineering at micro and nano length scales was brought to mechanical engineering undergraduates through the Micro/Nano Engineering Laboratory (2.674/2.675) at the Massachusetts Institute of Technology (MIT). This class is a hands-on laboratory designed to inspire interest and excitement about engineering at the small scale through building, observing and manipulating micro/nano structures and devices. We present the course design and implementation, discuss the challenges inherent in starting a new lab course, and review the student outcomes as tracked via post-course surveys. Introduction This laboratory was first offered in the spring of 2008 to 6 students and expanded significantly to become a mechanical engineering core course in 2010, with over 50 students participating every year. The course offers an overview of micro/nano technology in three main topic areas: MEMS, microfluidics, and nanomaterials. It is an intensive laboratory course where students experience building, observation, and design of micro and nano scale structures while using advanced imaging equipment such as scanning electron microscope (SEM), scanning tunneling microscope (STM), and atomic force microscope (AFM). Each week, the students attend one lecture (1 hour) and one lab session (3 hours). There are six lab modules covering photolithography and micromolding, microfluidic fluid forces, surface patterning, carbon nanotubes, SEM and STM, and AFM imaging and cantilever characterization. Students work in small groups, prepare lab reports for each module, and also learn to maintain a lab notebook. The main educational outcomes are to develop an understanding and familiarity with micro/nano system behavior and the capabilities of characterization tools at this size scale, while appreciating the connectivity of micro/nano scale systems to the broader mechanical engineering field. The student response to the micro/nano lab has been highly positive. The positive word-of-mouth coupled with increases in the number of mechanical engineering undergraduates has led to a rapid growth in enrollment for this course. Thus, our future plans involve continued streamlining to make a more efficient laboratory experience, and developing more transparent teaching materials so that the course may be easily transferrable to additional engineering instructors. Course Objectives As this course was developed, there were a number of course objectives and learning outcomes

that were desired. Overall, the course is meant to introduce concepts of nano/micro science and engineering while showcasing real-world applications and the relation of nano/microscale systems to mechanical engineering. The table below describes the more detailed course objectives, in terms of subject matter and learning outcomes. Table 1: Subject educational objectives and learning outcomes

Subject Educational Objectives Learning Outcomes • To introduce basic concepts of

nano/micro science and engineering and real-world applications of micro/nano systems

• To apply fundamental principles of science and engineering to understand the behavior and design of micro/nano systems

• To develop familiarity and basic

understanding of experimental methods and instruments used for investigating micro/nano systems

• To develop communication experience in small groups in the laboratory environment

• To provide exposure to multi-scale and multi-disciplinary problems

• To appreciate connectivity of mechanical engineering to micro/nano systems

• Ability to specify standard manufacturing techniques at small scales including lithography, micromolding, and microcontact printing

• Ability to identify capabilities of characterization techniques including scanning and transmission electron microscopy, scanning tunneling microscopy, atomic force microscopy, optical microscopy, and fluorescence microscopy.

• Knowledge of design and fabrication of

microfluidic devices, and physics of laminar pressure-driven and electrokinetic flows

• Knowledge of basic structural mechanics, sensing

and actuation principles, fabrication methods, and thermal noise in microelectromechanical systems (MEMS) with AFM cantilever as an example

• Appreciation of the importance of surfaces and

surface engineering for micro/nano systems • Knowledge of methods to grow and characterize

carbon nanotubes (CNTs) • Appreciation of macroscopic effects of microscale

and nanoscale phenomena • Ability to communicate effectively in laboratory

teams and in the reporting of results Course Design This course is a 6-unit class (1 hour lecture, 3 hours lab, 2 hours homework), divided into several modular sections. Each section has its own lab manual and experiments. Most modules are self-contained, with a few cases where something made in a lab session is used in a later module. There is also a graduate student option for this course (a 12-unit class) that requires the student to prepare an additional term paper and presentation, individually or in small groups. The term paper may be a review and literature critique on a selected micro/nano technology topic, or a

project/experiment that can be carried out using the available lab resources (including $500 allowance per team). A typical course schedule is presented below, for a 15 week semester. Table 2: Typical course schedule

Weeks Lecture Material Lab Module 1 Introduction & Lab Safety No lab 2 Introduction to MEMS and

microfabrication Benchtop photolithography and millifluidics

3 Introduction to microfluidics and soft lithography

Micromolding

4 No lecture- President’s day Microfluidic device fabrication 5 Microfluidic hydrodynamics: viscous flow,

surface tension, mixing Microfluidic hydrodynamics: droplets and diffusion

6 Microfluidics: electrokinetic flows Microfluidic hydrodynamics: electrokinetics 7 Engineering surfaces in micro/nano

devices Microcontact printing

8 No lecture – spring break No lab – spring break 9 Nanomaterials Growing and touching carbon nanotubes 10 Introduction to nanoscale imaging Nanoscale imaging: SEM, STM, TEM 11 Nanoscale imaging Nanoscale imaging: SEM, STM, TEM 12 No lecture – Patriot’s day AFM: setup and imaging 13 MEMS fabrication: AFM cantilever AFM: thermal noise of cantilever 14 Nanomaterials and devices No lab 15 Presentations by graduate students &

epilogue No lab

Module 1: Photolithography and micromolding The photolithography and micromolding module serves as an introduction to microfabrication. Students are exposed to the standard microfabrication techniques employed at semiconductor foundries and for MEMS devices during the lecture period. There are two portions to this lab module. In the first, the objective is to explore benchtop UV photolithography by building millimeter-scale fluidic devices and using them to observe flow and diffusive mixing. The second part of the module involves molding micro and nano-sized structures with polydimethylsiloxane (PDMS)4-11. As the teaching space is not a cleanroom, true photolithographic patterning with traditional resist material is not possible. Instead, a commercially available, UV-curable epoxy (Loctite 3108) is used as a one-step photo-definable polymer. Students dispense the epoxy on glass slides, place a transparency mask on top of the liquid pre-polymer, expose the stack under a UV lamp, peel off the mask, and wash off unexposed areas with acetone, and dry with an air gun. At this stage, the epoxy is under-exposed, meaning only a short exposure dose is used to define the pattern and allow the mask to be easily removed. A typical mask pattern has one channel and 4 connection ports (Figure 1).

Figure 1: Transparency mask examples for millifluidic devices The cap plate for the devices is fabricated next. Plastic slides with 4 pre-drilled holes are provided for the students, who attach Luer adapters to each hole using the UV epoxy. The assembled cap plate is then aligned to the device on the glass slide, and the whole assembly is fully cured under the UV lamp to seal the device. The testing phase for this module uses colored water and hand-driven syringe flow. The students record the time for the flow, and observe and sketch the flow patterns. Due to the small lengths the Reynolds number is low, which results in laminar flow with little mixing. The students then experiment with other geometries by drawing their own transparency masks, and are challenged with building a flow channel where diffusive mixing can occur at this length scale. Figure 2: Example devices illustrating laminar flow with little mixing and a student-designed mixer (each slide is 75 mm x 25 mm) In part two of this module the students develop protocols for preparing the PDMS elastomer (Dow Corning Sylgard 184) and fabricate structures from natural materials and everyday objects. The molded structures include lotus and oak leaves, and compact disks. The students image these samples under a light microscope to gain an appreciation for the size of structures that can be replica molded. Some of these molds will also be used for characterization in the AFM lab module. Students prepare the Sylgard 184 by weighing and mixing the base polymer with crosslinking agent, pouring the mixture, degassing the samples, and curing in an oven. They investigate what happens with and without degassing, and the effect of varying the crosslinker concentration. The cured samples are then placed in an air plasma, and students examine the change in surface energy by comparing the contact angles and swelling due to absorption when water and oil droplets are placed on treated and un-treated PDMS surfaces. Module 2: Microfluidic Hydrodynamics In this module, the students progress to building and testing devices to explore microfluidic transport phenomena. The devices are fabricated using PDMS micro-molding techniques from the previous module with silicon molds, which are patterned at MIT’s microfabrication center and provided to the students. Once the PDMS devices are released from the molds, access ports to the channels must be punched, and the devices are bonded to glass slides using gentle pressure

2.3” 0.6”

immediately after air plasma treatment. Three types of devices are made and tested in this module: droplet-generating devices, diffusion and mixing devices, and electrokinetics devices. The devices are made in one lab session, and subsequent weeks are devoted to experimentation. The diffusion, mixing, and droplet devices are tested using pressure-driven flows. Using colored water, the students first investigate mixing and diffusion in single-phase flows with co-laminar streams of water (one stream with food dye). The pressure of each stream is varied and the flows under various Reynolds numbers are observed. One of the devices has straight channels, while the other features channels with 90º bends. At low Reynolds numbers, the dye does not mix; however, at moderate Reynolds numbers, weak inertial effects cause significant folding at the bends, resulting in complete mixing. A simple device with a long observation channel allows students to quantify diffusive mixing. The droplet devices allow students to investigate the formation of droplets using viscous shear to emulsify the non-continuous (aqueous) phase. The students also introduce fluorescent microbeads into the aqueous stream and observe the circulating flow patterns within the droplets. The droplet size can be controlled by regulating the pressures of the two fluids. These devices allow students to observe and manipulate fluid flows and create emulsions that are prevalent in many applications, such as cosmetics, food processing and lubricant development, but difficult to visualize in macro-scale systems12-13. Figure 3: a) Single-phase mixing device b) droplet-generating device. There are three experiments in the electrokinetics section. One experiment examines the effect of buffer pH and microbead surface charge on its electrokinetic mobility, one observes electrokinetic flow profiles with varying device material, and the last one separates food dyes using electrophoresis14-15. For the first experiment, students use devices where the channels and bottom are all made of PDMS. This means that the devices must be bonded to PDMS-coated glass slides, not just plain glass, which allows for easier analysis as the channel is formed from one material. The students then study voltage-driven flow micron-sized fluorescent beads with either a surface carboxylate or amine group suspended in buffers at two different pH values, and measure the flow speeds using streak velocimetry on an inverted epi-fluorescence microscope. The students then proceed to the second objective, investigating device material. For this portion, devices are made using plain glass slides. The students choose one solution from the first part, and run that solution in a PDMS-glass device. The flow behavior in this device is more difficult to analyze as the fluid contacts two different materials, but bi-directional flow with non-uniform velocities is observed instead of the plug flow in the former case.

100  µm  200  µm  

a   b  

For the electrophoresis device, the flow is electrically driven through an agarose gel resulting in electrophoretic separation. The students fill the channels with agarose gel before injecting a mixture of amaranth and blue V calcium salt into one of the inlet ports for the short channel (Figure 4). Wire electrodes are placed into the proper wells (positive to outlet well of short channel, negative to inlet well) and a voltage is applied. After the dye mixture is driven across the short channel, the electrodes are moved so that the dye moves along the length of the long separation channel. After the dyes are separated, the applied voltage is switched off and the time and migrated distance are recorded to calculate the electrophoretic mobilities of the two dyes. Figure 4: Electrophoresis gel separation (long channel is 29 mm long, 325 µm wide, and 200 µm tall) Module 3: Surface engineering using soft materials This module examines the techniques of microcontact printing and self-assembly using PDMS stamps16-20. Students print three types of patterns: proteins on glass, self-assembled patterns using streptavidin-biotin binding, and self-assembled monolayers (SAMs) of alkanethiols on gold. The stamp masters are fabricated in silicon in the cleanroom, and PDMS stamps are cast on the masters. The stamp masters are on the same wafers as the microfluidics devices, so the students cast the PDMS stamps in the previous module. To print proteins on glass, the students coat the PDMS stamps with fluorescein-labled bovine serum albumin (FITC-BSA). The patterns are made on clean glass slides and then visualized under fluorescent microscopes. The condensation of water on the stamped patterns is observed under bright field illumination to probe the change in surface energy. In the streptavidin-biotin experiment, biotin-conjugated BSA is first stamped onto a clean glass surface. The remaining surface is then filled with FITC-BSA. This blocks the non-patterned surface and allows the pattern to be visualized under the fluorescent microscope. The last step is exposing the surface to streptavidin-coated microspheres and allowing the streptavidin-biotin linkage to form. The patterning of SAMs involves stamping of PDMS inked with mercaptohexanoic acid (MHA) on gold-coated glass slides. The pattern is observed on the surface by placing a drop of water on the slide or exhaling on the slide while it is under bright-field illumination. The patterned SAMs are then used as a mask during a gold wet-etch. The patterns of remaining gold can be observed under the microscope.

Figure 4: a) Patterned FTIC-BSA, b) streptavidin beads on patterned BSA, c) patterned gold after etch Module 4: Nanomaterials and Imaging with SEM & STM Module 4 is divided into several parts due to equipment limitations. The students form small groups and rotate through the different parts each week. The first part of this lab is growing and examining carbon nanotubes (CNTs)21-23. CNT forests are grown on catalyst-coated silicon substrates using thermal chemical-vapor deposition (CVD). The catalytic layers of iron coated on aluminum oxide are deposited by electron-beam evaporation in the cleanroom by teaching assistants (TAs)24. The coated substrates are provided for the students. The substrates are placed in the CVD furnace and the students operate the furnace (set temperature and run time, control gas flow rates of helium, hydrogen and ethylene) using the optimal conditions provided for them by the teaching staff. The furnace (available commercially from SabreTube)25 uses resistive heating of a silicon wafer and temperature monitoring using an infrared camera to locally achieve high temperatures required for CVD. Once the CNTs are grown, the students observe the super-hydrophobic nature of CNTs with water droplets and a high speed camera (Casio Exilim Pro EX-F1). The water contact angle is measured using a static drop, and then the high speed camera is used to record a droplet of water bouncing off the CNT forest26-28. Students then compare the contact angle and drop dynamics on the CNT forest with that on bare silicon and lotus leaves, a natural material that exhibits super-hydrophobicity. Figure 5: ~500 µm diameter water droplets on a) CNT forest, b) silicon wafer, c) lotus leaf The second part of this module involves understanding and using the SEM and STM imaging instruments. Students are first asked to calculate the theoretical limit of the optical microscope to prepare them for imaging beyond the visible light wavelengths. The SEM work is done on a Tescan Vega-3 machine which is ideal for this teaching setting: The machine has relatively quick pump down times and a multiple sample chuck, making it possible

a   b   c  

100  µm  100  µm  100  µm  

a   b   c  

for different groups of students to load, unload, and image multiple samples in one 3-hour lab period. Students image AFM tips, lotus leaves and the PDMS lotus leaf imprints (from Module 1), STM tips, mouse embryos, and the CNTs that were grown in the first part. Figure 7: Student images of a) lotus leaf, b) PDMS imprint of lotus leaf, c) mouse embryo, d) carbon nanotubes grown in lab The Nanosurf easyScan 2 STM is used for imaging down to the atomic level. Graphite samples are provided to the students. Although the machine is delicate and must be handled gently, students are able to generate nice images of the hexagonal graphite lattice structure. Figure 6: Student scans of graphite with student drawn overlays to visualize lattice and calculate angle of inclination Module 5: AFM imaging and cantilever characterization The last module is a more detailed study of an AFM imaging system, which also introduces to the students the importance and effect of noise in MEMS devices. The students use home-built AFM systems that were originally developed for a Biological Instrumentation and Measurement Laboratory (MIT class 20.309/2.673)29. These teaching AFMs are designed to be transparent in

20µm   20µm  

1  mm   50µm  

a   b  

c   d  

operation so the students can observe and experience how an AFM truly works. They utilize three interdigitated (ID) cantilever beams to minimize the sensitivity to external vibrations. The students begin by calibrating the AFM. For this system, the laser spot is centered on the ID portion of the beam. Thus the reflected laser beam is not a focused spot, but rather a diffraction pattern. The laser and detector positions must be adjusted so that a single mode (preferably 0th mode) passes through the detector’s slit. Next, the students mount a sample and bring the tip into contact. They must bias their system so that the z-displacement is centered around zero and the AFM is at its point of maximum sensitivity when the cantilever tip just comes into contact. The system is calibrated by applying a cyclic z-input with the piezo stage and observing the resulting signal. The signal for a linear input is the square of the sine due to constructive and destructive interference of light on the ID. Knowing the wavelength of the laser light, the students deduce the relationship between the input displacement and the photodiode output voltage. After setting up the system properly, the students may image their chosen samples. Figure 7: a) ID cantilever beam b) Student scan of compact disk surface showing data bumps and grooves After learning how to operate and image with the AFM, the students experiment with different AFM cantilevers to explore the effect of thermal noise on cantilever vibration. The thermal noise has a white (flat) power spectrum, but the cantilever has a first-order resonant frequency and higher-order resonances. First, the students review the fabrication process used to make these ID cantilever beams; the cantilevers are microfabricated out of silicon nitride and each die contains four cantilevers with three different dimensions (one is repeated). They calculate theoretical values of the spring constant and resonant frequency from the cantilever material properties and nominal geometry. Next, the students measure the power spectral density of the cantilever while it is freely suspended in air and apply the fluctuation-dissipation theorem to extract the cantilever properties and compare them with the theoretical values. The measurements and calculations are repeated for another cantilever on the same die. The students then postulate fabrication error mechanisms to explain the differences between observed and theoretical values. Student outcomes Generally, the student response has been highly positive. The enrollment history for the course is shown below in Figure 8, and it clearly indicates a large increase in the number of students participating.

a   b  

Figure 8: Student enrollment history for course 2.674/2.675. Student surveys have been collected, and are summarized for the Spring 2010 and 2011 semesters when there were more students participating, and the lab became a core course. The subject evaluation scores are shown in Figure 9. Each question has a maximum score of 7 and error bars show +/- one standard deviation.

Figure 9: Summary of survey results, error bars show +/- 1 standard deviation It is noted that for most questions, the rating from 2010 to 2011 decreased by a slight amount or stayed the same. The only areas that improved were the problem sets and feedback from the assignments. Although the decline in student survey results is small and well within a standard deviation, the slight downward trend in learning quality was also noticed by the teaching staff. In 2011 the growth of the course to 50+ students was felt as lab preparation and operation became difficult to maintain with the same resources. This led to the streamlining of the lab modules and course, to give a better experience and learning environment.

For the most part, the students enjoyed the course material and instructors, and gave positive evaluations. Many students expressed how the course addressed an emerging area that is not covered in other Mechanical Engineering courses. Some representative positive comments are quoted below.

“Really informative class. I think we focus on a lot of large systems in [Mechanical Engineering]. It is good to focus on micro and nano scale systems because this is state of the art right now.” “Great subject that exposed me to concepts that I have always heard of, but never got to see – now I have practice working with cutting edge nano processes! EXCELLENT CLASS- should be mandatory…” “…I really enjoyed the material taught (or introduced) in this class… I thought the lectures slides were great. They expressed the essence of the material…” “This subject really stimulated a new interest in me-- I came into the class with little enthusiasm, but I generally enjoyed the labs and lectures, and exited the class wanted [wanting?] to learn more.”

There were also more critical comments. Several students complained that there was too much chemistry in this course, that the lab reports took too long to prepare, and that time was wasted in lab waiting for equipment.

“It was really hard to answer questions about chemistry on the labs because meche students have very little knowledge on chemistry.” “Very simply, this course demands vastly more time than is suggested by its 6 unit (undergrad)/12 unit (grad) rating.” “Much of the time in lab involved waiting around, usually for equipment to become available.” “The lectures were rather boring, and I did not see how they prepared me for the labs until way later, when I was writing the lab report.” “The overall subject was too focused on microfluidic.”

Start-up and Operating Costs Starting a new lab course involves some new expenses. This is especially true for a course in nano/micro engineering, as one is not able to work at and observe small length scales without specific equipment. However, this course was designed to minimize the high costs associated with a cleanroom and traditional microfabrication equipment. For instance, the students learn about MEMS through milli and microfluidics, which do not require significant equipment

expenses. Also, future projects aim to further student interaction and learning without relying on a cleanroom facility. The table below shows the major equipment used by module and approximate cost. Table 3: Major Equipment used in 2.674/2.675

Equipment Modules Approximate Cost per instrument

SEM 4 $60000 STM 4 $20000 Tube furnace 4 $17000 AFM (homemade) 5 $12000 Inverted light and epi-fluorescent microscope, camera and computer

2, 3 $12000

Plasma cleaner/etcher 2 $7500 Curing oven 2, 3 $2000 Voltage source 2 $1000 Cleanroom costs 2, 3, 4 $1000 Pressure driven flow station (1 station, 3 flows) 2 $800

The on-going operating costs are not much different than a typical wet lab. Consumables must be ordered periodically, and most labs use standard reagents and materials. Challenges and future work The main challenge of this course is also what makes it so exciting: the lab modules at this small size scale are outside the realm of the standard mechanical engineering (ME) curriculum. As such, the course is not easily taught by all the ME faculty; and to date, the lab has been taught exclusively by the faculty who first designed the course. This makes it difficult to staff the course as it gains popularity, and to sustain the course long-term. Each lab module has “finicky” elements, requiring small tweaks during each semester. For instance, in the modules using UV curing, the intensity of the lamps varies as the bulbs age and the UV glue may vary slightly batch to batch. This means that at the beginning of each semester, the instructor and/or TA must test run the lab with the current resources to determine the optimal exposure times. Also, the labs are sometimes very material sensitive. One example is that the concentration of food dyes used to visualize water flow in many experiments needs to be optimized. A very concentrated solution is necessary to see color in such small volumes, but high dye loading also affects fluid properties and any crystallization out of solution can clog the fluidic channels. Currently an instructor manual is being written to address these types of issues, so that a new instructor could walk into the course and be aware of the many small details. Also, a dedicated lab instructor has been assigned to the course to maintain continuity, facilitate the lab operations, and enhance the learning experience. During this next year, some portions of the lab will be re-designed to make it more streamlined and teachable with less TA support. The electrokinetics section will be trimmed back. The

experiments using beads with surface charges will be phased out, due to difficulties in getting consistent fluid behavior and quality student analysis. To simplify fabrication and yield more reliable devices, the PDMS-PDMS electrokinetics devices will be replaced by PDMS-glass devices coated with high molecular weight polyvinylpyrrolidone (PVP) to quench electroosmotic flow30. The electrophoresis experiment will be slightly expanded as it is more reliable, and the students can obtain more quantifiable results. Other materials will be investigated for making the electrokinetics devices. Glass is the standard material for electrokinetics experiments, but it is costly and not easily manipulated in the lab. Instead we will look at molding with polystyrene, which is a relatively straightforward process and may yield a better, more uniform surface for fluid experiments31. Of course, the modules will also continue to be updated and improved. For instance, the STM machine is currently only being used to image samples. However, the machine can function in writing mode as well, and one of our goals is to produce a STM lithography experiment. Currently, there is a strong microfluidics emphasis in the course, and it would be nice to include other types of MEMS devices such as an actuator or sensor. However, without student access to a cleanroom, making more complex devices would require more reliance on TA fabrication skills and time. One idea being investigated is the use of Shrinky Dink microfluidics to enable rapid and cost effective student design, with the possibility of introducing 3-dimensional flows32-33. Another module in development uses a home-built microstereolithography apparatus for making polyethylene glycol (PEG) hydrogel structures. In conclusion we are pleased that most students find the course interesting and useful, as we feel that nano/micro scale manufacturing does have an important place in the ME curriculum. We will continue to update the course to keep it novel and relevant as this field is still rapidly changing. Our main goal for the short term is to make the course transparent and teachable by a wider range of faculty so we can maintain a good learning experience as the course continues to grow. Acknowledgements This course would not have been possible without the generous support of the Lufkin Foundation, the MIT Department of Mechanical Engineering, and the individuals who contributed their time, ideas, and energies. We would like to specifically thank Mary Boyce, John Leinhard, Todd Thorsen, Carol Livermore, Marco Cartas Ayala, Raymond Lam, Heonju Lee, Steven Wasserman, Steven Nagle, Steve Bathurst, and Wei Li. Bibliography

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