Duke Research Blog

Following the people and events that make up the research community at Duke.

Author: Anika Radiya-Dixit Page 1 of 2

Trapping Light to Enhance Material Properties

Professor Mikkelsen is the Nortel Networks Assistant Professor of Electrical and Computer Engineering and Assistant Professor of Physics at Duke University.

A version of this article appeared in Pratt’s 2017 DukEngineer magazine.

Professor Maiken H. Mikkelsen uses optics to tailor the properties of materials, making them stronger and lighter than anything found in nature. This distinguished researcher also teaches my ECE 340: Optics and Photonics course, giving me a wonderful opportunity to ask about her research and experience at the Photonics Asia conference held in China in October 2016.

Below is an edited transcript of our interview.

Q: What sparked your interest in optics and photonics?
I was really excited about doing hands-on research where you could actually probe nanoscale and quantum phenomena from optical experiments. I started out looking into condensed matter and quantum information science and currently observe delicately designed nanostructures. Optics is, to some extent, a tool to modify the properties of materials.

Q: What does your lab do and how do students contribute?
During the last few years, my students and I have been structuring materials on the nanoscale to modify the local electromagnetic environment, which makes these materials behave in new ways. Students play a key role in all aspects of the research, from nanofabrication to performing optical experiments and presenting the results to the scientific community at conferences all over the world. The lab uses tiny metal structures to concentrate the incoming electromagnetic field of light to very small volumes — a research area known as plasmonics. Placing other materials in the near field of this modified environment causes the electrons to behave completely differently.

Platform based on metal nanostructures that allows the lab to dramatically enhance the radiative properties of emitters and other materials.

By controlling how these electrons behave and modifying the geometry of the material, we can gain a deeper understanding of the light-matter interactions. Combining these techniques with our optical experiments shows modifications to material properties that are much stronger than has been seen before. It’s been very exciting!

Q: And this research is what you presented at the Photonics Asia conference?
Yes. With this knowledge, we can enhance the properties of materials significantly, which in the future could lead to ultra-fast and much better LEDs, more efficient photodetectors, or more efficient solar cells and sensors. In Beijing, China, I gave an overview of this research at the leading meeting for the photonics and optics industries in Asia, as well as several other conferences and universities. It was very fulfilling to see how the research I do in a dark lab actually gets noticed around the world. It is always deeply inspiring to learn about recent research breakthroughs from other research groups.

Q: What is the main purpose of trying to find these improved materials?
I am motivated by furthering our fundamental understanding, such as how do light and matter interact when we get to really small scales and how this interaction can be leveraged to achieve useful properties. I believe you often achieve the biggest technological breakthroughs when you’re not trying to solve one particular problem, but creating new materials that could lay the groundwork for a wide range of new technologies. For example, semiconductor materials, with a set of properties that are found naturally, are the cornerstone of most modern technologies. But if you imagine that you now have an entirely new set of building blocks with tailored properties instead, we could revolutionize a lot of different technologies down the road.

The Mikkelsen Research Group. Back row, left to right: Qixin Shen, Andrew Traverso, Maiken Mikkelsen, Guoce Yang, Jon Stewart, Andrew Boyce. Front row, left to right: Wade Wilson, Daniela Cruz, Jiani Huang, Tamra Nebabu.

By improving or completely changing the fabrication technique of these light-matter interactions, new properties begin to emerge. Generally, there’s always a big desire to have something that’s lighter, smaller, more efficient and more flexible. One of the applications we’re targeting with this research is ultrafast LEDs. While future devices might not use this exact approach, the underlying physics will be crucial.

About a year ago, Facebook contacted me and was interested in utilizing our research for omnidirectional detectors that could be ultrafast and detect signals from a large range of incidence angles. This has led to a fruitful collaboration and is one example of how fundamental research can have applications in a wide range of areas — some that you may not even have imagined when you started!


Q: What would be your advice to young researchers still trying to decide a career path for themselves or those interested in optics and photonics?
What really helped me was starting to do undergraduate research. I listened to talks by different faculty, asked them to do undergraduate research, and worked on a volunteer basis in their labs. I think that’s really a great way to see if you’re interested in research — use the amazing opportunities both at Duke and around the country. Doing research requires a lot of patience, but I think no two days are the same; there’s always a lot of creativity involved while troubleshooting new problems. After all, if it was easy or if we knew how to do it, it would have already been done. But it hasn’t, so we have to figure it out — I think that is a lot of fun. Doing internships in optics and photonics companies is also another option to learn more about research and development in the industry. Get as many experiences as possible and give things a chance!

Professor Mikkelsen is best known for the first demonstration of nondestructive readout of a single electron spin, ultrafast manipulation of a single spin using all-optical techniques, and extreme radiative decay engineering using nanoantennas.

Mikkelsen has received numerous accolades, including the Cottrell Scholar Award, the Maria Goeppert Mayer Award, and a “triple crown” of Young Investigator Awards from the Air Force, Army and Navy. Her work has been published in the journals Science, Nature Photonics, and Nature Physics, to name a few. Professor Mikkelsen enjoys hiking, gardening, playing tennis, and traveling in her free time.

Learn more at mikkelsen.pratt.duke.edu.

Written by Anika Radiya-Dixit

Visualizing the Fourth Dimension

Living in a 3-dimensional world, we can easily visualize objects in 2 and 3 dimensions. But as a mathematician, playing with only 3 dimensions is limiting, Dr. Henry Segerman laments.  An Assistant Professor in Mathematics at Oklahoma State University, Segerman spoke to Duke students and faculty on visualizing 4-dimensional space as part of the PLUM lecture series on April 18.

What exactly is the 4th dimension?

Let’s break down spatial dimensions into what we know. We can describe a point in 2-dimensional space with two numbers x and y, visualizing an object in the xy plane, and a point in 3D space with 3 numbers in the xyz coordinate system.

Plotting three dimensions in the xyz coordinate system.

While the green right-angle markers are not actually 90 degrees, we are able to infer the 3-dimensional geometry as shown on a 2-dimensional screen.

Likewise, we can describe a point in 4-dimensional space with four numbers – x, y, z, and w – where the purple w-axis is at a right angle to the other regions; in other words, we can visualize 4 dimensions by squishing it down to three.

Plotting four dimensions in the xyzw coordinate system.

One commonly explored 4D object we can attempt to visualize is known as a hypercube. A hypercube is analogous to a cube in 3 dimensions, just as a cube is to a square.

How do we make a hypercube?

To create a 1D line, we take a point, make a copy, move the copied point parallely to some distance away, and then connect the two points with a line.

Similarly, a square can be formed by making a copy of a line and connecting them to add the second dimension.

So, to create a hypercube, we move identical 3D cubes parallel to each other, and then connect them with four lines, as depicted in the image below.

To create an n–dimensional cube, we take 2 copies of the (n−1)–dimensional cube and connecting corresponding corners.

Even with a 3D-printed model, trying to visualize the hypercube can get confusing. 

How can we make a better picture of a hypercube? “You sort of cheat,” Dr. Segerman explained. One way to cheat is by casting shadows.

Parallel projection shadows, depicted in the figure below, are caused by rays of light falling at a  right angle to the plane of the table. We can see that some of the edges of the shadow are parallel, which is also true of the physical object. However, some of the edges that collide in the 2D cast don’t actually collide in the 3D object, making the projection more complicated to map back to the 3D object.

Parallel projection of a cube on a transparent sheet of plastic above the table.

One way to cast shadows with no collisions is through stereographic projection as depicted below.

The stereographic projection is a mapping (function) that projects a sphere onto a plane. The projection is defined on the entire sphere, except the point at the top of the sphere.

For the object below, the curves on the sphere cast shadows, mapping them to a straight line grid on the plane. With stereographic projection, each side of the 3D object maps to a different point on the plane so that we can view all sides of the original object.

Stereographic projection of a grid pattern onto the plane. 3D print the model at Duke’s Co-Lab!

Just as shadows of 3D objects are images formed on a 2D surface, our retina has only a 2D surface area to detect light entering the eye, so we actually see a 2D projection of our 3D world. Our minds are computationally able to reconstruct the 3D world around us by using previous experience and information from the 2D images such as light, shade, and parallax.

Projection of a 3D object on a 2D surface.

Projection of a 4D object on a 3D world

How can we visualize the 4-dimensional hypercube?

To use stereographic projection, we radially project the edges of a 3D cube (left of the image below) to the surface of a sphere to form a “beach ball cube” (right).

The faces of the cube radially projected onto the sphere.

Placing a point light source at the north pole of the bloated cube, we can obtain the projection onto a 2D plane as shown below.

Stereographic projection of the “beach ball cube” pattern to the plane. View the 3D model here.

Applied to one dimension higher, we can theoretically blow a 4-dimensional shape up into a ball, and then place a light at the top of the object, and project the image down into 3 dimensions.

Left: 3D print of the stereographic projection of a “beach ball hypercube” to 3-dimensional space. Right: computer render of the same, including the 2-dimensional square faces.

Forming n–dimensional cubes from (n−1)–dimensional renderings.

Thus, the constructed 3D model of the “beach ball cube” shadow is the projection of the hypercube into 3-dimensional space. Here the 4-dimensional edges of the hypercube become distorted cubes instead of strips.

Just as the edges of the top object in the figure can be connected together by folding the squares through the 3rd dimension to form a cube, the edges of the bottom object can be connected through the 4th dimension

Why are we trying to understand things in 4 dimensions?

As far as we know, the space around us consists of only 3 dimensions. Mathematically, however, there is no reason to limit our understanding of higher-dimensional geometry and space to only 3, since there is nothing special about the number 3 that makes it the only possible number of dimensions space can have.

From a physics perspective, Einstein’s theory of Special Relativity suggests a connection between space and time, so the space-time continuum consists of 3 spatial dimensions and 1 temporal dimension. For example, consider a blooming flower. The flower’s position it not changing: it is not moving up or sideways. Yet, we can observe the transformation, which is proof that an additional dimension exists. Equating time with the 4th dimension is one example, but the 4th dimension can also be positional like the first 3. While it is possible to visualize space-time by examining snapshots of the flower with time as a constant, it is also useful to understand how space and time interrelate geometrically.

Explore more in the 4th dimension with Hypernom or Dr. Segerman’s book “Visualizing Mathematics with 3D Printing“!

Post by Anika Radiya-Dixit.



Creating Technology That Understands Human Emotions

“If you – as a human – want to know how somebody feels, for what might you look?” Professor Shaundra Daily asked the audience during an ECE seminar last week.

“Facial expressions.”
“Body Language.”
“Tone of voice.”
“They could tell you!”

Over 50 students and faculty gathered over cookies and fruits for Dr. Daily’s talk on designing applications to support personal growth. Dr. Daily is an Associate Professor in the Department of Computer and Information Science and Engineering at the University of Florida interested in affective computing and STEM education.

Dr. Daily explaining the various types of devices used to analyze people’s feelings and emotions. For example, pressure sensors on a computer mouse helped measure the frustration of participants as they filled out an online form.

Affective Computing

The visual and auditory cues proposed above give a human clues about the emotions of another human. Can we use technology to better understand our mental state? Is it possible to develop software applications that can play a role in supporting emotional self-awareness and empathy development?

Until recently, technologists have largely ignored emotion in understanding human learning and communication processes, partly because it has been misunderstood and hard to measure. Asking the questions above, affective computing researchers use pattern analysis, signal processing, and machine learning to extract affective information from signals that human beings express. This is integral to restore a proper balance between emotion and cognition in designing technologies to address human needs.

Dr. Daily and her group of researchers used skin conductance as a measure of engagement and memory stimulation. Changes in skin conductance, or the measure of sweat secretion from sweat gland, are triggered by arousal. For example, a nervous person produces more sweat than a sleeping or calm individual, resulting in an increase in skin conductance.

Galvactivators, devices that sense and communicate skin conductivity, are often placed on the palms, which have a high density of the eccrine sweat glands.

Applying this knowledge to the field of education, can we give a teacher physiologically-based information on student engagement during class lectures? Dr. Daily initiated Project EngageMe by placing galvactivators like the one in the picture above on the palms of students in a college classroom. Professors were able to use the results chart to reflect on different parts and types of lectures based on the responses from the class as a whole, as well as analyze specific students to better understand the effects of their teaching methods.

Project EngageMe: Screenshot of digital prototype of the reading from the galvactivator of an individual student.

The project ended up causing quite a bit of controversy, however, due to privacy issues as well our understanding of skin conductance. Skin conductance can increase due to a variety of reasons – a student watching a funny video on Facebook might display similar levels of conductance as an attentive student. Thus, the results on the graph are not necessarily correlated with events in the classroom.

Educational Research

Daily’s research blends computational learning with social and emotional learning. Her projects encourage students to develop computational thinking through reflecting on the community with digital storytelling in MIT’s Scratch, learning to use 3D printers and laser cutters, and expressing ideas using robotics and sensors attached to their body.

VENVI, Dr. Daily’s latest research, uses dance to teach basic computational concepts. By allowing users to program a 3D virtual character that follows dance movements, VENVI reinforces important programming concepts such as step sequences, ‘for’ and ‘while’ loops of repeated moves, and functions with conditions for which the character can do the steps created!



Dr. Daily and her research group observed increased interest from students in pursuing STEM fields as well as a shift in their opinion of computer science. Drawings from Dr. Daily’s Women in STEM camp completed on the first day consisted of computer scientist representations as primarily frazzled males coding in a small office, while those drawn after learning with VENVI included more females and engagement in collaborative activities.

VENVI is a programming software that allows users to program a virtual character to perform a sequence of steps in a 3D virtual environment!

In human-to-human interactions, we are able draw on our experiences to connect and empathize with each other. As robots and virtual machines grow to take increasing roles in our daily lives, it’s time to start designing emotionally intelligent devices that can learn to empathize with us as well.

Post by Anika Radiya-Dixit

Starting Your Own Business in Social Entrepreneurship? Lessons from Four Founders

Interested in starting your own jazz festival? Or creating hydrogen-rich water to boost your circulation and improve muscle recovery?

These are the accomplishments of Cicely Mitchell and Gail Levy, who were among four inspiring leaders at the evening panel discussion in the Fuqua School of Business this past Wednesday. Excited students and faculty gathered in the Kirby Reading room to learn about the leaders’ unique perspectives as founders of non-profit and for-profit solutions to various social impact and sustainability issues.


Students and faculty gathered for dinner and networking before the panel discussion.

Organized by the Duke Innovation & Entrepreneurship Initiative and the Center for the Advancement of Social Entrepreneurship (CASE), the panel served to enlighten the audience about the challenges the women have faced and the lessons they learned in starting and scaling their social ventures. Panel moderator Erin Worsham, the Executive Director of CASE, opened the discussion with a few statistics.

In the non-profit sector, women make up 75% of the workforce, but in leadership positions, this ratio drops to 45%. As of 2013 in the for-profit sector, only 2.7% of venture capital investments went to fund companies with a female CEO. While black women own 1.5 million businesses in the U.S., they receive only 0.2% of venture funding. Undoubtedly, Worsham concluded, there is a lot of work to do in terms of women getting funded and represented as leaders.

Erin Worsham opened up the panel with statistics about women in the workforce. Worsham is the Executive Director of the award-winning CASE based at Duke University’s Fuqua School of Business

To commence the discussion, Worsham asked the panelists to speak about the gender discrimination they faced while starting their own companies. Gail Levy, founder of H Factor Water, a health-focused company producing hydrogen-infused water in environmentally friendly packaging, answered with a time she was challenged to a drinking match in order to close a deal. “The lesson I learned is to not go and drink your way into making a deal,” Levy joked. “But more importantly, you need to have grit and tenacity. Let our presence be known, because eventually we will be heard.”


Gail Levy was the founder of the White House Millennium Green Committee under the Clinton Administration in 1999. She is passionate about advocating for women worldwide and is also the founder of H Factor Water.

Founder of The Art of Cool, a Durham nonprofit promoting music education to Durham-area youth, Cecily Mitchell remarked that she would be charged significantly more money than a male counterpart to work with the same artist.

Cicely Mitchell is co-founder of The Art of Cool, a Durham nonprofit promoting music education to Durham-area youth

Cicely Mitchell is co-founder of The Art of Cool, a Durham nonprofit promoting music education to Durham-area youth

Rebecca Ballard, lawyer and founder of Maven Women, a sustainability-focused fashion company dedicated to making professional wear for women, noted that “we live in a visual world, but we need to start looking at a person’s character rather than solely focusing on how they look.” Based on her experience with her medical real estate development company ACCESS Medical Development, angel investor Stephanie Wilson expanded on the comment, adding that the best thing to do about the prejudice against women is to know that it’s there and fight for it.


Rebecca Ballard told the audience, “The most challenging thing about being a working woman is that appearance is considered ‘relevant.’” She started her career as a public interest lawyer and was previously the Executive Director of Social Impact 360.

I asked the founders to share their experiences in building a successful customer base. Wilson noted that to institute her company, she “determined who was the top real estate agent in our area and sought them out. I discussed my idea with them and asked for their advice on segueing into the market.” She suggested sending handwritten thank you notes to build relationships with your customers.

Stephanie Wilson founded ACCESS Medical Development and is also the co-founder of MillennialsMovingMillions.org.

Stephanie Wilson founded ACCESS Medical Development and is also the co-founder of MillennialsMovingMillions.org.

Mitchell added that The Art of Cool held the first few concerts for relatives and friends, and later partnered up with other small entrepreneurs. “Make sure what you do connects with people enough that they want to go and tell other people about what you’re doing,” she advised.

Cecily Mitchell talked about her experience with The Art of Cool. She handles the booking, contracts, networking, pitching for sponsorships and assisting in writing grants for the company.

Maven Woman founder Rebecca Ballard commented on the importance getting support from women in other sustainable industries, since “you are all driven by the same mission in the social entrepreneurship space.”


Rebecca Ballard is the founder of Maven Women, a sustainability-focused fashion company dedicated on making professional wear for women.

Worsham’s final question for the panel asked for any last pieces of advice. Ballard concluded the conversation with a reason why she started her company: “Social entrepreneurship exists because the status quo is not okay. There are externalities happening and people being treated badly; the status quo doesn’t have to be the way it is.”

From left to right:

Posing with the panelists! From left to right: Anika Radiya-Dixit (author), Gail Levy, Cecily Mitchell, Rebecca Ballard, and Stephanie Wilson.

By Anika Radiya-Dixit


Finding other Earths: the Chemistry of Star and Planet Formation

In the last two decades, humanity has discovered thousands of extrasolar planetary systems. Recent studies of star- and planet-formation have shown that chemistry plays a pivotal role in both shaping these systems and delivering water and organic species to the surfaces of nascent terrestrial planets. Professor Geoffrey A. Blake in Chemistry at the California Institute of Technology talked to Duke faculty and students over late-afternoon pizza in the Physics building on the role of chemistry in star and planet formation and finding other Earth-like planets.

milky way

The Milky Way rising above the Pacific Ocean and McKay Cove off the central California coast.

In the late 18th century, French scholar Pierre-Simon Laplace analyzed what our solar system could tell us about the formation & evolution of planetary systems. Since then, scientists have used the combination our knowledge for small bodies like asteroids, large bodies such as planets, and studies of extrasolar planetary systems to figure out how solar systems and planets are formed.

The "Astronomer's periodic table," showing the relative contents of the various elements present in stars.

The “Astronomer’s periodic table,” showing the relative contents of the various elements present in stars like the sun.

In 2015, Professor Blake and other researchers investigated more into ingredients in planets necessary for the development of life. Using the Earth and our solar system as the basis for their data, they explored the relative disposition of carbon and nitrogen in each stage of star and planet formation to learn more about core formation and atmospheric escape. Analyzing the carbon-silicon atomic ratio in planets and comets, Professor Blake discovered that rocky bodies in the solar system are generally carbon-poor. Since carbon is essential for our survival, however, Blake and his colleagues would like to determine the range of carbon content that terrestrial planets can have and still have active biosystem.

Analysis of C/Si ratios in extraterrestrial bodies revealed low carbon content in the formation of Earth-like planets.

Analysis of C/Si ratios in extraterrestrial bodies revealed low carbon content in the formation of Earth-like planets.

With the Kepler mission, scientists have detected a variety of planetary objects in the universe. How many of these star-planet systems – based on measured distributions – have ‘solar system’ like outcomes? A “solar system” like planetary system has at least one Earth-like planet at approximately 1 astronomical unit (AU) from the star – where more ideal conditions for life can develop – and at least one ice giant or gas giant like Jupiter at 3-5 AU in order to keep away comets from the Earth-like planet. In our galaxy alone, there are around 100 billion stars and at least as many planets. For those stars similar to our sun, there exist over 4 million planetary systems similar to our solar system, with the closest Earth-like planet at least 20 light years away. With the rapid improvement of scientific knowledge and technology, Professor Blake estimates that we would be able to collect evidence within next 5-6 years of planets within 40-50 light years to determine if they have a habitable atmosphere.


Graph displaying the locations of Earth-like planets found at 0.01-1 AU from a star, and Jupiter-like planets at 0.01-50 AU from a star.

How does an Earth and a Jupiter form at their ideal distances from a star? Let’s take a closer look at how stars and planets are created – via the astrochemical cycle. Essentially, dense clouds of gas and dust become so opaque and cold that they collapse into a disk. The disk, rotating around a to-be star, begins to transport mass in toward the center and angular momentum outward. Then, approximately 1% of the star mass is left over from the process, which is enough to form planets. This is also why planets around stars are ubiquitous.


The Astrochemical Cycle: how solar systems are formed.

The Astrochemical Cycle: how solar systems are formed.

How are the planets formed? The dust grains unused by the star collide and grow, forming larger particles at specific distances from the star – called snowlines – where water vapor turns into ice and solidifies. These “dust bunnies” grow into planetesimals (~10-50 km diameter), such as asteroids and comets. If the force of gravity is large enough, the planetesimals increase further in size to form oligarchs (~0.1-10 times the mass of the Earth), that then become the large planets of the solar system.


Depiction of the snow line for planet formation.

In our solar system, a process called dynamic reorganization is thought to have occurred that restructured the order of our planets, putting Uranus before Neptune. This means that if other solar systems did not undergo such dynamic reorganization at an early point in formation of solar system, then other Earths may have lower organic and water content than our Earth. In that case, what constraints do we need to apply to determine if a water/organic delivery mechanism exists for exo-Earths? Although we do not currently have the scientific knowledge to answer this, with ALMA and the next generation of optical/IR telescopes, we will be able image the birth of solar systems directly and better understand how our universe came to be.

To the chemistry students at Duke, Professor Blake relayed an important message: learn chemistry fundamentals very carefully while in college. Over the next 40-50 years, your interests will change gears many times. Strong fundamentals, however, will serve you well, since you are now equipped to learn in many different areas and careers.

Professor Blake and the team of former and current Caltech researchers.

Professor Blake and the team of former and current Caltech researchers.

Learn more about the Blake research group or their work.


By Anika Radiya-Dixit.


The Future of 3D Printing in Medicine

While 3D printers were once huge, expensive devices only available to the industrial elite, they have rapidly gained popularity over the last decade with everyday consumers. I enjoy printing a myriad of objects at the Duke Colab ranging from the Elder Wand to laptop stands.

One of the most important recent applications of 3D printing is in the medical industry. Customized implants and prosthetics, medical models and equipment, and synthetic skin are just a few of the prints that have begun to revolutionize health care.

3D printed prosthetic leg: “customizable, affordable and beautiful.”

Katie Albanese is a student in the Medical Physics Graduate Program who has been 3D printing breasts, abdominal skeletons, and lungs to test the coherent scatter x-ray imaging system she developed. Over spring break, I had the opportunity to talk with Katie about her work and experience. She uses the scatter x-ray imaging system to identify the different kinds of tissue, including tumors, within the breast. When she isn’t busy printing 3D human-sized breasts to determine if the system works within the confines of normal breast geometries, Katie enjoys tennis, running, napping and watching documentaries in her spare time. Below is the transcript of the interview.

How did you get interested in your project?

When I came to Duke in 2014, I had no idea what research lab I wanted to join within the Medical Physics program. After hearing a lot of research talks from faculty within my program, I ultimately chose my lab based on how well I got along with my current advisor, Anuj Kapadia in the Radiology department. He had an x-ray project in the works with the hope of using coherent scatter in tissue imaging, but the system had yet to be used on human-sized objects.

Could you tell me more about the scatter x-ray imaging system you’ve developed?

Normally, scatter in a medical image is actively removed because it doesn’t contribute to diagnostic image quality in conventional x-ray. However, due to the unique inter-atomic spacing of every material – and Bragg’s law – every material has a unique scatter signature. So, using the scattered radiation from a sample (instead of the primary x-ray beam that is transmitted through the sample), we can identify the inter-atomic spacing of that material and trace that back to what the material actually is to a library of known inter-atomic spacings.

Bragg diffraction: Two beams with identical wavelength and phase approach a crystalline solid and are scattered off two different atoms within it.

How do you use this method with the 3D printed body parts?

One of the first things we did with the system was see if it could identify the different types of human tissue (ex. fat, muscle, tumor). The breast has all of these tissues within a relatively small piece of anatomy, so that is where the focus began. We were able to show that the system could discern different tissue types within a small sample, such as a piece of excised human tissue. However, in order to use any system in-vivo, which is ideally the aim, you have to determine whether or not it works on a normal human geometry. Another professor in our department built a dedicated breast CT system, so we used patient scans from that machine to model and print an accurate breast, both in anatomy and physical size.


What are the three biggest benefits of the x-ray imaging system for future research? 

Main breast phantom used and a mammogram of that phantom with tissue samples in it

Main breast phantom used and a mammogram of that phantom with tissue samples in it

Coherent scatter imaging is gaining momentum as an imaging field. At the SPIE Medical Imaging Conference a few weeks ago in San Diego, there was a dedicated section on the use of scatter imaging (and our group had 3 out of 5 talks on the topic!). One major benefit is that it is noninvasive. There is always a need for a noninvasive diagnostic step in the medical field. One thing we foresee this technology being used for could be a replacement for certain biopsy procedures. For instance, if a radiologist finds something suspicious in a mammogram, a repeat scan of that area could be taken on a scatter imaging system to determine whether or not the suspicious lesion is malignant or not. It has the potential to reduce the number of unnecessary invasive (and painful!) biopsies done in cancer diagnosis.

Another thing we envision, and work has been done on this in our group, is using this imaging technique for intra-operative margin detection. When a patient gets a lumpectomy or mastectomy, the excised tissue is sent to pathology to make sure all the cancer has been removed from the patient. This is done by assessing whether or not there is cancer on the outer margins of the sample and can often take several days. If there is cancerous tissue in the margin, then it is likely that the extent of the cancer was not removed from the patient and a repeat surgery is required. Our imaging system has the potential to scan the entirety of the tissue sample while the patient is still open in the operating room. With further refinement of system parameters and scanning technique, this could be a reality and help to prevent additional surgeries and the complications that could arise from that.

What was the hardest or most frustrating part of working on the project? 

We use a coded aperture within the x-ray beam, which is basically a mask that allows us to have a depth-resolved image. The aperture is what tells us where the source of the scatter came from so that we can reconstruct. The location of this aperture relative to the other apparatus within our setup is carefully calibrated, down to the sub-millimeter range. If any part of the system is moved, everything must be recalibrated within the code, which is very time-consuming and frustrating. So basically every time we wanted to move something in our setup to make things better or more efficient, it was like we were redesigning the system from scratch.

 What is your workspace like?

Katie and the team at the AAPM (American Association of Physicists in Medicine) conference from this past summer in Anaheim, CA where she presented in a special session on breast imaging. From left to right: Robert Morris (also in the research lab and getting his degree in MedPhys), Katie, Dr. James Dobbins III (former program director and current Associate Vice Provost for DKU) and Dr. Anuj Kapadia, my advisor and current director of graduate studies in the program

Katie presented in a special session on breast imaging at the American Association of Physicists in Medicine conference this past summer in Anaheim, CA. From left to right: Robert Morris, also working in the lab; Katie; Dr. James Dobbins III, former program director and current Associate Vice Provost for Duke-Kunshan University; and Dr. Anuj Kapadia, Katie’s advisor and current director of graduate studies.

We have a working experimental lab within the hospital. It looks like any other physics lab you might come across- messy, full of wires and strange electronics. It is unique from other labs within the Medical Physics department because a lot of research that is done there focuses on image processing or radiation therapy treatment planning and can be done on just a computer. This lab is very hands-on in that we need to engineer the system ourselves. It is not uncommon for us to be using power tools or soldering or welding.

What do you like best about 3D printing? 

3D printing has become such a great community for creativity. One of my favorite websites now, called Thingiverse, is basically a haven for 3D printable files of anything you could ever dream of, with comments on the best printing settings, printers and inks. You can really print anything you want — I’ve printed everything from breasts, lungs and spines to small animal models and even Harry Potter memorabilia to add to my collection. If you can dream it, you can print it in three dimensions, and I think that’s amazing.


Anika_RD_hed100_2By Anika Radiya-Dixit


Why care about the gender gap in science and tech?

A day on the job for Christine McKinley

A day on the job for Christine McKinley

Scenes like the one above are engineer Christine McKinley’s favorite views of the construction sites where she manages building designs and contracts with other engineers. McKinley, a mechanical engineer, musician, and author, enjoys the complexities, high stakes and surprises of her job. Engineers, she says, “design against [surprises] but live for surprises.”

One of these surprises, McKinley told an audience last Thursday Feb. 25 in the Nelson Music Room at Duke, was a talk she had with the director of a community college district. He told her “women aren’t as good as math and science.” Shocked and disappointed that a man in charge of the education of the young students would believe this, McKinley pointed out that several of her accomplished colleagues were women. McKinley, like many other women, was frustrated that she has to work harder than men to get a promotion.

Is this changing? Are women today more prevalent in engineering fields than they were twenty to thirty years ago?

The chart below depicts the distribution of engineers in 1989: only 15 percent are women.

Distribution of Engineering Graduates in 1989

Of course, 1989 was 27 years ago and a different cultural time, with Nintendo’s Game Boy and Prince William’s seventh birthday. But the chart below shows how little those numbers have changed.

Distribution of Engineering Graduates in 2015

For mechanical engineers, the gap is much larger: only 7 percent are women (yellow faces), while the blue faces represent men, with the some frowning ones unhappy to be working with the women.

Percent of female mechanical engineers

Percent of female mechanical engineers

When the workers are broken down into teams, according to McKinley, the image below is what it actually feels like to be working as a female mechanical engineer.

What it actually feels like to be a female mechanical engineer

What it actually feels like to be a female mechanical engineer

Let’s start with the most troubling issue regarding the lack of diversity in engineering. If women and people of color are told that we are not good at math and science, and we believe it, then we are choosing a form of helplessness. Specifically, if we don’t pick apart the data and challenge those who made up this story, then it sticks, and the “rumor” becomes a narrative – and that’s dangerous, McKinley said. However, everyone needs to know basic chemistry, math, and physics to participate in conversations about topics such as medicine, NASA, one’s cholesterol level, and energy conservation as a knowledgeable adult. People need to be STEM-literate to be able to analyze this data, and men, especially in the 1950s, didn’t want women to research the facts and prove a competition.

Why should we care about women choosing careers in STEM fields?

Reason 1: Gender financial inequity: STEM grads make more than non-STEM grads

If we care about the gender pay gap, and only 19 percent of engineering graduates are women, then that aggravates the situation. This gender inequity can be addressed – partly – by women choosing to study engineering, McKinley said.

Of course, money is not the only thing in life; we want jobs with meaning, she added. However, even civil engineers understand that they are in a helping profession, always excited to build a new bridge, for example, to help people cross a flooded river. At the same time, money gives one the ability to leave a spouse, to take care of a disabled child, to find a better job, to afford healthier food; making real money gives one a way to become independent and make better choices. Working a job, however, does not imply that we must “sacrifice [our] life and fun.” McKinley enjoys what she does and has a lot of fun on the job; studying math and science, she says, is not that complex with the right motivation and support.

Reason 2: Humanity’s Survival

A coronal mass ejection (CME) is an enormous eruption of gas and magnetic field that launches billions of tons of plasma from the sun’s surface into space. Such an event occurred in 1859. As a result, farmers plowing field with horses noticed a bright flash of light, steam engines continued to run on schedule, and telegraph operators were confused when their telegraph batteries stopped working. Overall, there were few problems due to the limited technology at the time.

Imagine a CME happening today. All our large pieces of equipment – power stations, transformers, and transmission lines – would get fried.

Equipment involved in the transportation of energy from power plants to users

If these power houses blow up, what are we going to do? With three-year lead-time and $2 trillion cost, they will not be repaired in time for us to continue our daily functions. We now have a civilization-changing event on our hands – what Hurricane Katrina gave us, but now, for entire countries. We are in a time where our dependence on technology is constantly rising – until it’s not. In such a disastrous scenario, we will need more engineers. At this time, everyone – men and women – will come together to work on simple, elegant solutions to make the world better.

Currently, we have a mass shortage of engineers, so those today are overbooked with work. If these engineers are unable to find time to think through the entire solution and review all possible sources of error, then it creates a problem not only for engineering but also for the entire world in general. We are in need of good engineers and a diverse workforce to bring together all our ideas for a better world.

McKinley notes that she finds herself more comfortable when there are other women in the room. As a result, the whole team gets more relaxed, “elevating everyone’s game,” and people get more creative and feel more secure in sharing their ideas.

Grace Hopper created the computers advertised in this flyer.

Grace Hopper created the computers advertised in this flyer.


Reason 3: The third reason we care about this view about engineering is the history of STEM achievements by women being ignored or the credit being taken by men.

Women who became mathematicians in the 1900s had to fight hard to have their contributions to the field recognized. The world misses out significantly if the achievements of half of humanity are ignored.

Hertha Aryton was a brilliant mathematician who had been elected the first female member of the Institution of Electrical Engineers in 1899. In 1902, she became the first woman nominated a Fellow of the Royal Society of London. “Because she was married, however,” McKinley quoted, “legal counsel advised that the charter of the Royal Society did not allow the Society to elect her to this distinction.”

Amalie Noether was another incredible mathematician who invented a theorem that united symmetry in nature and the universal laws of conservation. Some consider Noether’s theorem, as it is now called, to be as important as Albert Einstein’s theory of relativity. Einstein himself regarded her as most “significant” and “creative” female mathematician of all time. However, McKinley tells the audience, she was denied a working position at universities simply because they did not hire female professors.

In the 1900’s, more than 1000 women joined an organization called Women Airforce Service Pilots. They transported newly-made planes to the fighter pilots; however, many of the planes were untested, causing 38 of them to die in service. While they went through intense military training and had prior experience, the women were considered “civilian volunteers” and had to fight to be recognized. Further, most of the accepted women to the organization were white, and the only African American applicant was asked to withdraw her application.

Nancy Fitzroy was American engineer and heat transfer expert in the 1900s. She received plenty of criticism as well, but she said it didn’t affect her: “The reaction I pretty much have gotten most of my life is ‘little girl, what are you doing here?’ but I was a good engineer. That’s what made all the difference.”


Curiosity, inventiveness, and the urge to improve are not male traits. They are human traits. Women are half of humanity; they are not the spectators. Women must step up and contribute even if it is more difficult. Constantly underestimated as a female mechanical engineer, McKinley says she uses this underestimation as fuel to work harder and become better.

Being an engineer is worth it. Ask great questions, and be really good.

Remember, McKinley told her audience, that engineering is full of surprises. And for people who underestimate you, you’ll be that surprise.




Christine McKinley gave her talk in the Nelson Music Building at Duke last Thursday for Feminist/Women’s month.

Christine McKinley is a mechanical engineer, musician, and author. Her musical Gracie and the Atom, won a Portland Drammy for Original Score. Her book Physics for Rock Stars was published in 2014 by Penguin Random House. Christine hosted Brad Meltzer’s Decoded on History Channel and Under New York on Discovery Channel.

You can view her website, read her book, or contact her via email.


Anika_RD_hed100_2 By Anika Radiya-Dixit



What Came Before the Big Bang?

The Big Bang Theory: Origins of the universe.

Students and faculty gathered in the Physics building over coffee last Friday to understand the theory and mathematics behind a fundamental question: how did our universe start and what came before it?

Cosmologist and theoretical physicist Laura Mersini-Houghton, associate professor at UNC, is a proponent of the idea that our universe is one of many.

Cosmologist and theoretical physicist Laura Mersini-Houghton, associate professor at UNC, is a proponent of the idea that our universe is one of many.

Laura Mersini-Houghton, associate professor of theoretical physics and cosmology at the University of North Carolina at Chapel Hill, has appeared on various TV and radio stations to discuss her theories on black holes and the origins of the universe.

With the rise of technology in the twentieth century, we now know more about the Big Bang and the dark energy that makes up approximately 70 percent of the universe. With the expansion of universe, all other matter — everything we have observed on Earth and through instruments — will dilute, while dark energy, which has constant density, will expand, thereby “pushing the universe apart.”

Expansion of the universe due to dark energy.

What has bothered scientists since the early 1970’s are the questions: what exactly selected the initial conditions of the universe? What determined the arrow of time? Why did we have to start with these very special conditions?

What brings these issues to the forefront of research today is that fact that dark energy will be the only thing remaining in the present timeline of our universe. In other words, we are going towards another big bang explosion. In order to predict how the future of the universe will evolve, we must first understand the mystery behind dark energy.

Dr. Mersini-Houghton says that the chances of a Big Bang happening by chance are 1 / 10^{10^123}, which is infinitely impossible. What selected this initial condition?

Illustration of the string theory landscape of multiple universes.

She proposes wave functions. When the energy of each wave function is at a tipping point, a new big bang occurs and with it another universe is created. With the support of the string theory, using one-dimensional strings in place of the particles of quantum physics, we calculate a landscape of 10^500 possible universes. The hypothesis that there exist other universes then raises the question: why did we start with this universe? Our universe is no longer at the center of the Cosmos as we previously believed; rather it is a humble member in a vastness.

Even if there are multiple universes, their entanglement with us is so tiny that they are nearly impossible to detect. However, the Planck satellite has found concrete scientific evidence of changes in energy due to other universes. According to Dr. Mersini-Houghton, atypical observations made about galaxies moving in the wrong direction and the unexplained “Cold Spot” in the cosmic microwave background are effects are due to the presence of neighboring universes.

In short, nature is a lot more complicated than we think it is, and simply looking at it and simplifying the problem to solely our world will not help us understand what is truly happening. To address the problem of our origins, perhaps we need to extend our paradigm of space-time and look for observational tests of a multiverse framework.

Stephen Hawking’s take on parallel universes in an interview.


Learn more about Mersini-Houghton’s multiverse theory and her latest research on Hawking radiation and black holes. To view a list of her talks, visit her webpage or send her an email at mersini@physics.unc.edu.

By Anika Radiya-Dixit.






Geography and the Web: A new frontier for data vizualization

A GIS Day earth cake made by the Collegiate Baker

You might be forgiven if you missed GIS Day at The Levine Science Research Center Nov. 18, but it was your loss. Students and faculty enjoyed a delightful geography-themed afternoon of professional panels, lightning talks, and even a geospatial research-themed cake contest.

What is GIS and why is it important?

Geographic information systems (GIS) give us the power to visualize, question, analyze, and interpret data to understand relationships, patterns, and trends in the world around us. Those who work with data and analytics have a responsibility to contribute to this change by helping us make the right decisions for our future. As noted during ESRI’s 2015 User Conference in the video below, “We have a unique ability to impact and shape the world around us. [Yet] for all of our wisdom, our vast intellectual marvels, we still choose a path of unsustainability and continue to make decisions that negatively impact the Earth and ourselves. […]We must accept our responsibility as stewards of the Earth. […] We must apply our best technology, our best thinking, our best values. Now is the time to act. Now is the time for change.”


How does GIS help?

Doreen Whitley Rogers, Geospatial Information Officer for the National Audubon Society, led a lively discussion about GIS and the World Wide Web at Duke’s GIS Day. She said GIS is essential to understand what is happening in the geographic space around us. As GIS becomes increasingly web-based, efficiently distributing the system to other people is crucial in a time when new data about the environment is being created every second.

3D map displaying the height of buildings that birds hit windows

3D map displaying the height of buildings at which birds fly into windows in Charlotte, NC

Rogers and her team are aiming to move authoritative GIS data to web for visualizations and create a centralized system with the potential to change our culture and transform the world. As the technology manager, she is working on bringing the information to people with proper security and integrity.

In order to get people to use GIS data in a generalized way, Rogers needed to implement several core capabilities to assist those integrating GIS into their workflow. These include socializing GIS as a technology to everybody, creating mobile apps to work with data in real time, and 3D maps such as this one of bird-strikes in downtown Charlotte.

Case Studies

ClimateWatch helps us predict the seasonal behaviour plants and animals.

Mobile apps connecting to the GIS platform promise a strong “return on mission” due to the vast number of people using maps on phones. By mobilizing everyone to use GIS and input data about birds and geography in their area, the platform quickly scales over millions of acres. In the Bahamas, an  app allows users to take pictures to support bird protection programs.

ClimateWatch is an app that gives us a better understanding of how bird habitats are affected during temperature and rainfall variations – motivating people to speak up and act towards minimizing anthropogenic climate change. Developed by Earthwatch with the Bureau of Meteorology and The University of Melbourne, the app enables every Australian to be involved in collecting and recording data to help shape the country’s scientific response to climate change.

Virtual simulation of scenic flights as an endangered bird.

Virtual simulation of scenic flights from the perspective of an endangered bird.

Apps such as the 3-D flight map give users the vicarious thrill of cruising through nature landscapes from the view of endangered birds.

With the movements toward cleaning air and water in our communities, our planet’s birds will once again live in healthier habitats. As the Audubon Society likes to say: “Where birds thrive, people prosper.”




For more information about bird-friendly community programs, you can visit Audubon‘s site or send them a message.

Doreen Rogers after her presentation on National GIS day.



To learn more about data visualization in GIS, you can contact Doreen Whitley Rogers via email here.


Post by Anika Radiya-Dixit

Iridescent Beauty: Development, function and evolution of plant nanostructures that influence animal behavior

Iridescent wings of a Morpho butterfly

Iridescent wings of a Morpho butterfly

Creatures like the Morpho butterfly on the leaf above appear to be covered in shimmering blue and green metallic colors. This phenomenon is called “iridescence,” meaning that color appears to change as the angle changes, much like soap bubbles and sea shells.

Iridescent behavior of a soap bubble

Iridescent behavior of a soap bubble

In animals, the physical mechanisms and function of structural color have been studied significantly as a signal for recognition or mate choice.

On the other hand, Beverley Glover believes that such shimmering in plants can actually influence animal behavior by attracting pollinators better than their non-iridescent counterparts. Glover,Director of Cambridge University Botanic Garden,  presented her study during the Biology Seminar Series in the French Family Science Center on Monday earlier this week.

Hibiscus Trionum

Hibiscus Trionum

The metallic property of flowers like the Hibiscus Trionum above are generated by diffraction grating – similar to the way CD shines – to create color from transparent material.

In order to observe the effects of the iridescence on pollinators like bees, Glover created artificial materials with a surface structure of nanoscale ridges, similar to the microscopic view of a petal’s epidermal surface below.

Nanoscale ridges on a petal's epidermal surface.

Nanoscale ridges on a petal’s epidermal surface.

In the first set of experiments, Glover and her team marked bees with paint to follow their behavior as they set the insects to explore iridescent flowers. Some were covered in a red grating – containing a sweet solution as a reward – and others with a blue iridescent grating – containing a sour solution as deterrent. The experiment demonstrated that the bees were able to detect the iridescent signal produced by the petal’s nanoridges, and – as a result – correctly identified the rewarding flowers.

Bees pollinating iridescent "flowers"

Bees pollinating iridescent “flowers”

With the evidence that the bees were able to see iridescence, Glover set out for the second experiment: once the bees find a specific type of flower, how long does it take them to find the same flower in a different location? Using the triangular arrangement of shimmering surfaces as shown below, Glover observed that iridescence produced by a diffraction grating leads to significant increase in foraging speed as compared to non-iridescent flowers.

Triangular formation of iridescent disks used for experimentation on bees

Triangular formation of iridescent disks used for experimentation on bees

While iridescence in plants is difficult to spot by a casual stroll through the garden, pollinators such as bees definitely can see it, and scientists have recently realized that insect vision and flower colors have co-evolved.

In order to ensure that pollen is transferred between flowers of the same species, these flowers have developed a unique structure of iridescence. As scientists work on understanding which plants produce these beautiful colors and how the nanoscale structure is passed down through reproduction, we can only look at our gardens in wonder at the vast amount of nature that still remains to be explored and learned.

Wonder of nature

Wonders of nature in an everyday garden



Beverley Glover is the Director of Cambridge University Botanic Garden and is currently accepting applications for PhD students






Post written by Anika Radiya-Dixit


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