• Image: Dr. Szeto is pointing to a cart that has been equipped with sensors and transceivers to help a blind shopper locate specific grocery store items. Using RFID technology and a local area map, this “smart” grocery cart determines its location in the store and the location of a desired product. With those pieces of information, the cart determines the optimal path to the desired product and safely guides a blind shopper to it using headphone commands.

How did you get into electronics/ engineering and when did you start?

Believe it or not, my first exposure to electrical engineering occurred when I was in middle school almost five decades ago and assigned to do a science project. I was asked, “Why don’t you participate in the science fair at our school?” So I went to the library and checked out some books on hobbies and came across a book that showed me how to build a simple electrical motor. While reading the book, I said to myself, “This project is just right because I did not need to spend much to buy fancy parts, which I could not afford .” While searching for the necessary parts, I came across some old used dry cell batteries that a neighbor had thrown away in the trash. It was through this science project that I first learned about batteries and how to parallel them and put them in series to increase their voltage. I built my own electrical motor and thus became interested in engineering.

I was always a little bit curious about how things worked. People in my generation, in their 50s and 60s, often grew up as tinkerers. I remember taking apart my mom’s digital clock radio and trying to fix it. Back in those days, the radio had actual flaps of numbers, not LED numerals. I tried to fix it after it went bad. I did not succeed, but that experience peaked my curiosity.

In high school, I benefitted from guidance counseling. Back in those days they actually had courses called career guidance or career counseling. The teacher talked about a whole bunch of careers. Since I liked science and math and enjoyed building things, engineering was a perfect fit. I went to UCLA and majored in engineering, and everything that I expected came true.

Students at SDSU and probably most other colleges often take a circuitous varied path to their final major and career. They typically they change their major twice during their undergraduate studies. I was lucky; I never changed my major at UCLA. I found out I liked engineering although it was hard work. There were a lot of labs, homework, and class hours, but I liked it. Thus I made no academic detours during my four years at UCLA.

How did you get into Rehabilitation Electronics?

My current area of work is rehabilitation electronics, which is electronics applied to people with disabilities. We perform research in effort to determine what we can do to improve their quality of life, address some concerns they have, and so forth. How I got into rehabilitation electronics is again a bit serendipitous. When I was a graduate student at UC Berkley, I came across a newspaper article about a research project on intracochlear prosthesis being done by Dr. Michael Merzenich at the UCSF Medical Center. He was working on how to stimulate the ear, more specifically the auditory nerve in the ear, so that people who had dysfunctional hair cells could hear again. Hair cells converted mechanical vibrations in the cochlea into neural impulses that we perceive as sound. A graduate friend and I arranged to meet Dr. Merzenich and spent 3/4 of a day touring his lab to find out what he was doing and seeing what kind of research projects he might have for us. This experience got me interested in the general field of biomedical engineering or rehabilitation electronics.

During my doctoral studies at UCLA, there were two popular TV shows: “The Six Million Dollar Man” and “Bionic Woman.” Coincidently UCLA’s Biotechnology Lab at that time had a project funded by the Veterans Association to develop sensory feedback in artificial arms. Given the TV series and my natural desire to apply electronics to help human kind, I joined this project.

I have been in this general area since 1975. There have been slight detours, but nothing drastic. The projects change, the people involved change, the funding changes, but my interest in rehabilitation electronics has remained pretty constant.

What have been some of your greatest success in terms of research projects?

My biggest claim to fame was determining the best way of providing sensory feedback to the user by stimulating the user’s sense of touch. The problem with artificial arms, especially powered artificial arms (those that run on external power like batteries), is that they can do a lot of things, but controlling them and getting information back from them is difficult. The control aspect is the amputee telling the arm, “I want to do something.” The feedback is the arm confirming to the user that I am doing what you want me to do and where the arm is in 3-D space.

Our natural arm has proprioperception, which is sense of space, and kinetics, which is sense of motion. Basically we know where our hands are without having to visually monitor it. This part is missing in artificial arms. Hence one of the key challenges in upper limb prosthesis is how can we convey this information back to the user in an unobtrusive way? One possible input channel for sensory feedback is the sense of touch. For a number of years, I have quantitatively studied various ways of stimulating the sense of touch such that the amputee can decipher the sensory information being transmitted most easily and most accurately.

What type of technology have you used to do this?

Why did I choose the sense of touch? We have five senses. Taste and smell are two senses that are NOT very controllable. The sense of hearing and sight are already heavily burdened by their primary duties, thus leaving the sense of touch. Research has shown that vibratory tactile sensations can be generated by applying well-controlled electrical pulses to the skin surface.

During my doctoral studies and in subsequent projects, I have tried to determine how best to unobtrusively inform the amputee about how bent the prosthetic elbow is, how open or closed the hand is, what is the grasp force on the object being held, what is the weight of the object, etc. The central research question was, how do we encode this information in such a way that the amputee can decipher it best and most quickly? So we use electrical signals to stimulate the nerves. When I began the study in the late 1970s, I used electrical stimulation of the skin surface so that the nerves near the skin surface would be activated . The perceptions evoked by these electrical impulses felt vibratory and pain-free. We used electrical signals because they were the most power efficient because everything had to be powered by batteries. Using mechanical vibrators to stimulate the sense of touch would consume much more energy and be heavier.

Electrical impulses on the skin’s surface seemed to be a viable method of entering information for the amputee to interpret. Because of progress in biocompatibility and miniaturization, research efforts today focus on using implanted electrodes that directly stimulate sensory nerve endings. Direct nerve stimulation offers greater discrimination than stimulating on the skin’s surface although there are still potential for foreign body rejection.

When you stimulate the nerve, what is the approach?

We have not yet achieved the ability to reliably stimulate just one nerve fiber. We can certainly achieve the goal of stimulating a small group of nerve fibers that do the same thing. The research question remains about how to stimulate the nerves in such a way that the sensation evoked is the most natural, easily perceived, and understood by the amputee. One reason for optimism is the tremendous adaptability of the human being or neuroplasticity. Over time, our bodies can adapt to strange signals and reinterpret them almost automatically to mean something else. For instance, neuroplasticity underlies the recovery of many individuals of stroke, where they relearn to walk and talk. It is because another part of the body that is undamaged by the stroke learns to do the things that the damaged part of the body used to do. Our neural system has a remarkable ability to accommodate and adapt. We hope that the body of the amputee learns to reinterpret artificially generated sensory signal to mean something that is more useful.

Is it difficult to get volunteers to test this type of work?

Absolutely. Getting volunteers is difficult. Several decades back when I started with skin surface stimulation, getting volunteers for that was not hard. Getting volunteers to allow you to open them up and stick electrodes in their body and look for nerves is a little bit tougher. That is part of the challenge of studying direct neural stimulation. We need to try it on laboratory animals, treating them well of course, and make sure they do not suffer needlessly, to see how they react and learn the trick of the trade, using them as practice. Then we will move on to human subjects.

Can you provide some more details about your current project?

I am fortunate to be part of an engineering research center funded by NSF. We received final confirmation that the National Science Foundation will fund our center for the initial five years. SDSU will be a part of the Engineering Research Center on Sensori-motor Neural Engineering, led by the University of Washington in Seattle. We are a partner along with MIT and one or two smaller institutions in this effort that NSF has deemed worthy of funding and support. My involvement in this ERC is trying to provide or improve the sensory feedback available from an artificial leg.

I am much more knowledgeable with the sensory feedback from artificial arms, and less with the sensory feedback of artificial legs, though it is still important. The key issue in artificial arms is achieving exquisite control and sensory feedback in artificial arms. Trying to come up with a robotic arm that does many things well and giving the user an innate sense of what it is doing are very challenging. In artificial legs, the problem there is weight bearing and stability. The body weight and stresses when we walk, climb stairs, run, or jump on different types of surfaces have to be transferred to the skeleton of the amputee through the soft tissue of the stump.

One of the goals of the ERC is to come up with better lower limb prosthesis. I will be contributing to the clinical testing of any leg designs we come up with, as well as coming up with methods to provide efficacious sensory feedback.

What direction do you see your field in the next few years?

This is what energizes a lot of biomedical engineers. Biomedical engineering is considered one of the new hot fields in engineering. In electrical engineering we have roughly 15 percent females and 85 percent males. In biomedical engineering it is close to 50/50. It is obviously an attractive field to many, because you feel noble in your efforts trying to help human beings, trying to solve problems that are very real and practical.