October 3, 2014

A better prosthesis: Sandia invents sensors to learn about fit; systems to make the fit better

A BETTER FIT FOR PROSTHETICS — Jason Wheeler (6533) demonstrates a liner aimed at helping prosthetic limbs fit better. Sandia’s Intelligent Systems, Robotics, and Cybernetics group is developing a liner with sensors that tell what’s going on in a limb and a system to automatically accommodate changes. The project has worked with several different types of prosthetic limbs. (Photo by Randy Montoya)

by Sue Major Holmes

As an amputee walks on a prosthetic leg during the day, the natural fluid in the leg shifts and muscles in the calf shrink slightly.

Now imagine the problem that can pose for the fit of the prosthesis.

There’s a growing need for a solution. The national Amputee Coalition says nearly 2 million people in the United States live with limb loss, and about two-thirds have lost a lower limb. That could double by 2050 because diabetes is increasing. Diabetes is the leading cause of limb loss, accounting for more than 65,000 amputations a year nationwide. In addition, a Congressional Research Service report in February lists 1,558 major limb amputations from US battle injuries in Iraq and Afghanistan in 2003-2013.

Sandia researcher Jason Wheeler (6533) has been studying prosthetics at the Labs for a decade. He is part of an Intelligent Systems, Robotics and Cybernetics group working to develop a sensor to tell what’s going on with a limb and a system to automatically accommodate the body’s changes. After additional testing and some refinements, he hopes to find a company that wants to market the sensor system.

The interface, or socket, between a prosthesis and a limb is custom-made, starting with a cast of the area. The socket follows that contour, and a clinician adjusts it for the best fit.

In the case of a leg, the prosthesis bears the weight of the wearer when standing or moving. But Jason says tissues in your leg, unlike tissues on the bottom of your foot, aren’t well-suited for that pressure. In addition, a limb doesn’t stay the same shape during the day because of fluid fluctuations, and, of course, people gain or lose weight. Thus, a custom-fit socket doesn’t always fit.

Detecting pressure in three directions

Robotics researchers developed a small sensor, about the size of a quarter, for inside the socket to monitor fit and detect deviations. Sandia has filed a patent application and has presented papers at conferences about the work.

Jason says Sandia’s sensor is unique because it detects pressure in three different directions: normal pressure, like when you push your finger down on your thigh, and shear forces on the skin — think of sliding your finger down and across your leg. Shear forces are important because they cause such problems as rubbing, blisters, and abrasions, but no appropriately sized commercial sensing system can monitor them, he says.

So Sandia invented the three-axis pressure sensor, incorporated into a liner that slips into the socket of a prosthesis. Sensors can be placed in various spots, measuring three directions at each site. Other designers have placed pressure sensors in sockets but those measured only normal pressure, Jason says.

“The thing that prevents people from wearing a prosthetic or being satisfied with their prosthesis is comfort,” he says. “Even if you’ve got a high-technology limb, if it’s not comfortable, people won’t wear it.”

Shear pressures in a socket haven’t been well studied, and Sandia wants to understand them better to use that information in developing systems that adjust socket shape to changes in limb shape. “This extra information gives you better ability to know when you need to make modifications because the shear pressures tend to be a little more sensitive to changes in socket shape than normal pressures,” Jason says.

Sandia’s system automatically adjusts socket shape by moving fluid into bladders inside the liners that amputees normally wear to improve a socket’s fit and comfort. Standard liners are like a stretchy, cushiony sock a few millimeters thick, made of a gel-like material that’s a bit sticky to help hold everything in place.

Since modifying a custom socket would be expensive and cumbersome and could require several fittings, Sandia adapted its technology to fit inside a liner made of elastomeric material similar in thickness to a gel liner.

“With the liner, you just take out your old one and drop in the new one and you’re good to go. That’s a very important component of this technology,” Jason says.

The system adjusts to limb changes by using bladders inside the liners, and filling the bladders using valves and pressurized liquid on the outside of the liner. Prototypes have been developed to fill and empty the bladders automatically, but Jason says more research is needed to determine when it’s best to add and remove fluid.

A liner can accommodate both sensors and bladders, depending on the need. “Sometimes you might just want to sense, sometimes you might just want to fill a bladder, sometimes you might want to do both, so the system is flexible enough you can create a liner that does any of those functions,” Jason says.

Amputees currently add special fitted socks on their limb to deal with fluid loss and shrinkage. It’s an imperfect solution, forcing them to always have socks on hand and to take off the prosthesis to change them.

It’s also imperfect because the leg loses volume in muscles but not where it’s largely bone, such as the front of the tibia. A sock adds volume everywhere, distributing pressure unevenly. In contrast, a bladder system adds volume only where needed. “Being able to put additional fluid volume locally, where you lost it, is an important component,” Jason says.

More work planned

Sandia, through a partnership with the University of Washington, has done limited testing with a prototype sensor liner. Jason also tested it, using a liner cut out at the bottom so he can slip it on his leg. Then he uses a clamp-on two-piece socket with an artificial foot so he walks on the artificial foot underneath his own foot, which shifts the load to his leg. Amputees also have tested prototype liners with the integrated bladders.

The sensor and bladder systems have not yet been tested together as a closed loop system.

“Right now, we don’t really understand the right method to control the fluid movement,” Jason says. “When you walk you have all these different signals and they’re telling you something, but due to limited research in this area it’s not entirely obvious what the signals mean. We need to do more studies to learn what those signal changes mean about how to adjust the socket shape.”

Other institutions have worked on closed loop systems, but Jason says Sandia’s development of liners with both sensors and automatic fluid adjustment is unique. “That capability to construct liners with things built right into them should be of a lot of interest to the orthotics and prosthetics community,” he says.

Sandia’s robotics group began prosthetics research more than a decade ago through DOE’s proliferation prevention programs, initially collaborating on humanitarian projects with Russian companies. Jason, who has a background in mechanical engineering and assistive robotics, worked on some of those programs when he joined Sandia in 2004. The robotics group has continued prosthetics research with funding from the Department of Defense Peer Reviewed Orthopaedic Research Program, which develops technology for veterans. “We have the expertise here and it relates to our national security missions,” Jason says. He says prosthetics research and development is an ideal way to combine his expertise in mechanical design and biomedical engineering with his desire to help injured people.

Development is continuing and more amputee testing is needed, but the technology “is getting mature enough where before too long, if we want it to be successful, we’re going to have to hand it off to a commercial entity to market it,” he says.


-- Sue Major Holmes

Back to top of page

Up, up, and away Sandia driver hits it big with balloon fiesta poster

Semiramis Novak (102641), named for an aunt and a legendary queen of Assyria, is as comfortable with a paintbrush as with the wheel of a big rig. Her painting was named the official poster of the 2014 Albuquerque International Balloon Fiesta. (Photo by Randy Montoya)

by Nancy Salem

Semiramis Novak can drive a semi tractor-trailer, run a forklift, and tame a jackhammer. She has the presence of a model and a voice bred on the streets of Philadelphia.

She’s tough, but beneath lives the soul of an artist.

Semiramis (pronounced Sim-merm’-mis), who drives heavy trucks for the Reapplication Team (102641), is one of New Mexico’s premier watercolorists. The official poster of the 2014 Albuquerque International Balloon Fiesta opening Oct. 4 is her painting, a major recognition.

“I am psyched about it,” she says. “It has given me exposure I didn’t have before.”

Semiramis loves to operate machinery but says her passion is painting. Her first artworks, at age 7, were car-sized drawings of Batman chalked on the streets. “I would come home and my mom would say, ‘Are you chalking again?’ I’d say “No, ma, not me.’ And she’d say, ‘You’re lying, your knees and elbows are black.’ So I cleaned up my knees before going home,” she says. “I could draw really well.”

Semiramis took art classes in Pittsburgh but when she needed a job found one operating a forklift. “I’ve always enjoyed driving. I drove tractors in the country, snowmobiles. Anything to drive was exciting to me,” she says. “I liked equipment and learning about it.”

A flyer changed everything

Semiramis got married and moved to Colorado. There her artwork took a back seat as she worked in the Coors brewery plant, divorced, got a job driving trucks for DOE at Rocky Flats, remarried, and had children.

 One day a small flyer came in the mail announcing a watercolor class by artist Don Cohen at Red Rock Community College. “I signed up and ended up taking four semesters,” Semiramis says. “Besides having a great teacher, there were other teachers in the class and I picked up ideas from them. They taught me a lot and I’m still friends with them today. Don Cohen is still my mentor.”

The class helped Semiramis blossom as an artist. “Prior to that I was just drawing and sketching. I never tried to exhibit or sell art,” she says. “I started entering shows and selling paintings. My art just boomed and from then on I was painting all the time.”

Semiramis works in a small studio next to her garage. She paints in layered colors in large format, with many pieces measuring 4 feet by 6 feet, from photos she draws in graphs onto sheets of watercolor paper. “Under every great painting is a great drawing,” she says.

Her subjects range from landscapes to cityscapes to close-ups of cacti and flowers. A large painting can take 100 hours to complete. She shows around the world, including exhibits of the American Watercolor Society, Rocky Mountain National Watermedia, and the MasterWorks of New Mexico. She is a member of the New Mexico Watercolor Society, and was invited to join the elite Wet Brush Group of artists who critique each other’s work.

The chosen poster

She did the balloon fiesta painting in 2004 shortly after her family moved to New Mexico from Colorado. She and her husband Frank Novak (102651) both joined Sandia within a few years of arriving in Albuquerque.

 “I loved being in the midst of all those people and balloons. I told my kids and husband to walk ahead and I took pictures,” she says. The painting, at more than 6 feet wide, was too big for shows so it moved over the years from a hotel to a restaurant.

Last year Semiramis decided to do more to promote her artwork, and thought about the balloon fiesta poster and her big painting. She called the organizers in July and was told entries were being accepted that week. “I dropped it off and a week goes by, then two, then three, then a month. I called to see when they wanted me to pick it up and they said it had been chosen as the poster,” she says.

The fiesta bought the original and sells the posters for $150 each with signature and $50 without. Semiramis will sign posters in a booth at the fiesta. It is selling well so far and is expected to sell out. “The notoriety is great,” she says. “Now friends and neighbors want to buy my originals.”

Semiramis paints every weekend and is grateful for her success. She gets to work early and walks in the Reapp yard to watch the sunrise. “It’s my walk of thanks,” she says. “I love art. My paintings are like my children. You build a relationship as you create a painting. Even when I was 7 there was something about drawing and getting it right. I put my heart and soul into it.”


-- Nancy Salem

Back to top of page

The look of a scientist - Math skill leads a cool kid to career success, HENAAC award

HENAAC award winner Edward Jimenez (9525) says applied mathematics lets him look for challenging problems in areas that don’t necessarily overlap. “The common language between them is math,” he says.

by Nancy Salem

Growing up in the southern California farming community of El Centro, the time came when Edward Jimenez had to fess up to his pals. He was good at math. Not only that, he liked it.

“I lost some friends. They said I changed, that I wasn’t the same guy anymore,” he says. “But I didn’t worry about it. You have to find what makes you happy. It sounds clichéd but it’s the absolute truth.”

And just as his high school friends were surprised, so were his peers at San Diego State University. He interviewed with the dean of the College of Sciences for a spot in the Minority Access to Research Careers, or MARC, program. At the orientation the dean walked straight past Edward and into her office.

“She said she had to ask her secretary who I was,” Edward says. “When she first interviewed me I was in a suit with my hair pulled back. At orientation I wore long hair, earrings, black shorts, and an Ozzy Osbourne T-shirt. She thought I was an academic probation student.”

But Edward knew who he was. “I can look however I want and it doesn’t mean I have to be a certain type of person,” he says. “Not a whole lot of scientists I know have the goatee, shaved head, and earrings. But I don’t feel I’m disregarded in any way. I and others know what I’m capable of.”

Edward (9525) was recently named a 2014 HENAAC Award winner as Most Promising Engineer/Advanced Degree by Great Minds in STEM. He joins other honorees at the 26th annual HENAAC conference in New Orleans Oct. 2-4.

HENAAC, formerly the Hispanic Engineering National Achievement Awards Corp., honors the best STEM minds in the country. Each winner is peer-reviewed and chosen by representatives of industry, government, military, and academic institutions. Great Minds in STEM promotes those fields to underserved and underrepresented communities.

A mother’s firm hand

The award makes Edward a role model for young people, but he says he wasn’t always a great student. “There were peaks and valleys from daycare through high school,” he says. “I didn’t do well as a freshman because I was obsessed with what my friends thought of me.”

A constant was his mother’s emphasis on science, technology, and math. “She showed me how to add and subtract before kindergarten,” he says. “I loved all the science shows like Mr. Wizard’s World and Bill Nye the Science Guy.”

He was interested in everything from biology to astronomy to physics, and wanted to be an astronaut or scientist when he grew up. But in high school, friends and girls got his attention.

His mom pulled him back.

“She was very tough on me,” Edward says. “I was grounded on a weekly basis. But what she was saying eventually stuck. I realized I wasn’t trying. I set small goals. Let’s see if I can turn in my homework for all my classes this week, then for a month. Let’s see if I can get As on the exams for all my classes. Little things like that.”

Slowly but surely he quit goofing off and focused on what he wanted to do in life. “As a senior I looked back and saw that I consistently had an A in math. It came easy to me,” he says. “When I told my pre-calculus teacher, who was in his 70s, that I had declared math as my college major, he did cartwheels he was so happy. There weren’t a lot of math majors.”

How to be a college student

Edward says he didn’t know what he was getting into and had no intention of going to graduate school. He was the first member of his family to go to college. “I had the mentality of ‘Cs get degrees,’ in college,” he says. “I thought I would just get a job after I graduated.”

But then he was contacted by the Louis Stokes Alliances for Minority Participation, a national STEM outreach program that offered him the chance to enroll in a calculus introduction course the summer before his first semester at SDSU. “They paid you to participate and gave you a graphing calculator, the most advanced technology I had ever used. That program played a huge role in putting me on the right path, to plan past a bachelor’s degree. It put me in touch with people who showed me how to be a college student.”

Edward carried a 4.0 grade-point average his first two years and caught the attention of the McNair Scholars Program, a US Department of Education initiative to increase the number of PhDs among groups historically underrepresented in graduate programs. McNair placed Edward in a summer program that allowed him to do research under faculty guidance.

“I did scientific research as an undergrad on a new way to distill petroleum to make gasoline, and had the opportunity to publish in journals and present at conferences,” he says. “It was a great experience. I was so eager to do research. It prepared me for graduate school in terms of what’s expected of a researcher and how to be a scientist.”

In 2004, Edward earned a bachelor’s degree in mathematics with an emphasis in computation science from SDSU followed in 2010 by a PhD in applied mathematics from the University of Arizona. He interned at Sandia starting in 2007 and was hired after graduation from Arizona.

“I love Sandia,” Edward says. “It’s exciting every single day. Management is supportive. The culture is just great.”

He says applied mathematics lets him look for challenging problems in many areas. “I can work in high-performance computing one day, radiography and tomography the next, and follow up with holography,” he says. “Areas like these don’t overlap, but the common language between them is mathematics.”

Edward is a team member on a Laboratory Directed Research and Development (LDRD) project in radiography, leading an effort to develop a way to identify the composition of a material from an X-ray image. The three-year project has produced several papers and patents. A previous Early Career LDRD, in which Edward was the principal investigator, developed ways to reconstruct big data using computer tomography and multiple processors, cutting a process that can take years down to less than a day, and conserving energy. The project, which has four patents pending, wrapped in 2013.

“Early Career LDRD helped me dive into the research at Sandia as an entry-level employee,” Edward says. “It let me take advantage of the skill sets I had while gaining others more in line with Sandia’s mission and values.”

A message to young people

He hopes to stay in research for at least another decade. “The type of work I do is intriguing,” he says. “I tackle problems nobody else in the world gets to do.”

Edward was nominated for the HENAAC award by Sandia President and Laboratories Director Paul Hommert, who described him as “continually demonstrating integrity, technical knowledge, innovative research, excellent communication skills, and superb leadership and teamwork, especially in nurturing the development of future scientists and engineers while making his own impressive accomplishments.”

Edward, who says winning the HENAAC was humbling and a high point in his career, reaches out to high school students in Albuquerque through programs including Sandia’s Manos. “I tell them that the fact you’re sitting here interested shows you have some level of potential, and you need to pursue that,” he says. “Yes, some of my friends didn’t want to hang with me anymore once I started doing well in school, even though nothing about me changed. But what’s more important to you, having a friend now or being successful the rest of your life?”

Edward, who is married with a 3-month-old son, found what makes him happy. “It’s science. I’m motivated by finding problems people have either never thought of or have not been able to solve. I try to instill in scientists of the next generation that to make any contribution is great. At Sandia we push boundaries, increase capacities, decrease limitations, and advance science.”


-- Nancy Salem

Back to top of page

Download Lab News October 3, 2014 (PDF, 2MB)