The February 2023 issue of IEEE Spectrum is here!

Close bar

Wearable Sensors Spot Lyme Disease

A Stanford researcher didn’t notice a rash—or yet have a fever—but his wearables prompted him to seek early treatment for Lyme disease

3 min read
Stanford research Michael Snyder poses laden with the wearable gadgets that recently helped him realize he'd been infected by Lyme disease before he showed symptoms
Photo: Steve Fisch/Stanford

Stanford professor Michael Snyder was flying to Norway for a family vacation last year, wearing a Basis smart watch (since discontinued), a RadTarge radiation monitor, and iHealth, Scanadu, and Masimo oximeters. He was also using the MOVES app on his smart phone. Together, all this gear collects data on heart rate, blood oxygen, skin temperature, and activity, including sleep; steps; walking, biking, and running; calories expended; acceleration; and exposure to gamma rays and X-rays.

Snyder hadn’t loaded up on wearables just for this flight; he wore this gear regularly for two years as part of a study of 60 people, and frequently calibrated it with more standard medical tests. The goal? Try to figure out just how useful wearables can be in early disease diagnosis. The results of that study were published last week.

But there was something different about that plane ride. Snyder noticed that his oxygen levels—which he’d previously realized dropped during an airplane flight but returned quickly after landing—didn’t return to his baseline as expected. And his heart rate—that usually increased at the beginning of a flight but again quickly returned to baseline—didn’t come down as it normally would. Something was not right.

Snyder considered what, if anything, he’d been doing differently. Two weeks earlier, he’d been building a fence in rural Massachusetts—could he have been bitten by a tick and contracted Lyme disease? After his wearables also started recording a fever, he was able to convince a local doctor to treat him with antibiotics. Later blood tests for Lyme disease proved his hunch had been correct.

“The fact that you can pick up infections by monitoring before they happen is very provocative,” said high-tech health expert Eric Topol, professor of genomics at the Scripps Research Institute, in a statement.

It turns out, as noted by Snyder and the other researchers who worked on the study, that Lyme disease triggers particularly strong changes in heart rate, so was easy to detect.

The research team included Gao Zhou, Wenyu Zhou, Sophia Miryam Schüssler-Fiorenza Rose, Dalia Perelman, Ryan Runge, Shannon Rego, Somalee Datta, and Tracey McLaughlin, from Stanford; Elizabeth Colbert, from the Veterans Affairs Palo Alto Health Care System; and high school student Ria Sonecha.

The team also suggested that wearables can identify insulin resistance, a precursor for Type 2 diabetes, using an algorithm that examines steps and differences between daytime and nighttime heart rates. Researchers also attribute the fatigue experienced by air travelers to a drop in blood oxygen that comes with flying—it’s likely why so many people doze during flight. Interestingly, they noted that during long flights oxygen levels improve as the body adjusts.

Are we really all going to strap on multiple gadgets, and wear them all the time? Snyder says that’s not really necessary, the Basis smart watch and the iHealth oximeter pretty much did the job. Oxygen sensors will likely migrate into wrist wearables. And then, with the proper algorithms, your smart watch could just alert you with a light or buzzer when it detects something off, like a prolonged elevated heart rate while you’re inactive. With an early warning of incoming illness you might be inclined rest a little more, or take various supplements intended to help you fight off viruses.

The researchers noted in their report that, of course, “It is possible that the use of wearables will lead to false alarms and overdiagnosis of disease. The number of false alarms will depend upon the threshold that is set, which can be personalized.”

“Overall,” they wrote, “we envision that these devices could be particularly powerful for individuals who are responsible for the health of others (parents and caregivers), and perhaps also for those who have historically limited health care access, including groups with low income and/or remote geography.”

The Conversation (0)

The Inner Beauty of Basic Electronics

Open Circuits showcases the surprising complexity of passive components

5 min read
A photo of a high-stability film resistor with the letters "MIS" in yellow.
All photos by Eric Schlaepfer & Windell H. Oskay

Eric Schlaepfer was trying to fix a broken piece of test equipment when he came across the cause of the problem—a troubled tantalum capacitor. The component had somehow shorted out, and he wanted to know why. So he polished it down for a look inside. He never found the source of the short, but he and his collaborator, Windell H. Oskay, discovered something even better: a breathtaking hidden world inside electronics. What followed were hours and hours of polishing, cleaning, and photography that resulted in Open Circuits: The Inner Beauty of Electronic Components (No Starch Press, 2022), an excerpt of which follows. As the authors write, everything about these components is deliberately designed to meet specific technical needs, but that design leads to “accidental beauty: the emergent aesthetics of things you were never expected to see.”

From a book that spans the wide world of electronics, what we at IEEE Spectrum found surprisingly compelling were the insides of things we don’t spend much time thinking about, passive components. Transistors, LEDs, and other semiconductors may be where the action is, but the simple physics of resistors, capacitors, and inductors have their own sort of splendor.

High-Stability Film Resistor

A photo of a high-stability film resistor with the letters "MIS" in yellow.

All photos by Eric Schlaepfer & Windell H. Oskay

This high-stability film resistor, about 4 millimeters in diameter, is made in much the same way as its inexpensive carbon-film cousin, but with exacting precision. A ceramic rod is coated with a fine layer of resistive film (thin metal, metal oxide, or carbon) and then a perfectly uniform helical groove is machined into the film.

Instead of coating the resistor with an epoxy, it’s hermetically sealed in a lustrous little glass envelope. This makes the resistor more robust, ideal for specialized cases such as precision reference instrumentation, where long-term stability of the resistor is critical. The glass envelope provides better isolation against moisture and other environmental changes than standard coatings like epoxy.

15-Turn Trimmer Potentiometer

A photo of a blue chip
A photo of a blue chip on a circuit board.

It takes 15 rotations of an adjustment screw to move a 15-turn trimmer potentiometer from one end of its resistive range to the other. Circuits that need to be adjusted with fine resolution control use this type of trimmer pot instead of the single-turn variety.

The resistive element in this trimmer is a strip of cermet—a composite of ceramic and metal—silk-screened on a white ceramic substrate. Screen-printed metal links each end of the strip to the connecting wires. It’s a flattened, linear version of the horseshoe-shaped resistive element in single-turn trimmers.

Turning the adjustment screw moves a plastic slider along a track. The wiper is a spring finger, a spring-loaded metal contact, attached to the slider. It makes contact between a metal strip and the selected point on the strip of resistive film.

Ceramic Disc Capacitor

A cutaway of a Ceramic Disc Capacitor
A photo of a Ceramic Disc Capacitor

Capacitors are fundamental electronic components that store energy in the form of static electricity. They’re used in countless ways, including for bulk energy storage, to smooth out electronic signals, and as computer memory cells. The simplest capacitor consists of two parallel metal plates with a gap between them, but capacitors can take many forms so long as there are two conductive surfaces, called electrodes, separated by an insulator.

A ceramic disc capacitor is a low-cost capacitor that is frequently found in appliances and toys. Its insulator is a ceramic disc, and its two parallel plates are extremely thin metal coatings that are evaporated or sputtered onto the disc’s outer surfaces. Connecting wires are attached using solder, and the whole assembly is dipped into a porous coating material that dries hard and protects the capacitor from damage.

Film Capacitor

An image of a cut away of a capacitor
A photo of a green capacitor.

Film capacitors are frequently found in high-quality audio equipment, such as headphone amplifiers, record players, graphic equalizers, and radio tuners. Their key feature is that the dielectric material is a plastic film, such as polyester or polypropylene.

The metal electrodes of this film capacitor are vacuum-deposited on the surfaces of long strips of plastic film. After the leads are attached, the films are rolled up and dipped into an epoxy that binds the assembly together. Then the completed assembly is dipped in a tough outer coating and marked with its value.

Other types of film capacitors are made by stacking flat layers of metallized plastic film, rather than rolling up layers of film.

Dipped Tantalum Capacitor

A photo of a cutaway of a Dipped Tantalum Capacitor

At the core of this capacitor is a porous pellet of tantalum metal. The pellet is made from tantalum powder and sintered, or compressed at a high temperature, into a dense, spongelike solid.

Just like a kitchen sponge, the resulting pellet has a high surface area per unit volume. The pellet is then anodized, creating an insulating oxide layer with an equally high surface area. This process packs a lot of capacitance into a compact device, using spongelike geometry rather than the stacked or rolled layers that most other capacitors use.

The device’s positive terminal, or anode, is connected directly to the tantalum metal. The negative terminal, or cathode, is formed by a thin layer of conductive manganese dioxide coating the pellet.

Axial Inductor

An image of a cutaway of a Axial Inductor
A photo of a collection of cut wires

Inductors are fundamental electronic components that store energy in the form of a magnetic field. They’re used, for example, in some types of power supplies to convert between voltages by alternately storing and releasing energy. This energy-efficient design helps maximize the battery life of cellphones and other portable electronics.

Inductors typically consist of a coil of insulated wire wrapped around a core of magnetic material like iron or ferrite, a ceramic filled with iron oxide. Current flowing around the core produces a magnetic field that acts as a sort of flywheel for current, smoothing out changes in the current as it flows through the inductor.

This axial inductor has a number of turns of varnished copper wire wrapped around a ferrite form and soldered to copper leads on its two ends. It has several layers of protection: a clear varnish over the windings, a light-green coating around the solder joints, and a striking green outer coating to protect the whole component and provide a surface for the colorful stripes that indicate its inductance value.

Power Supply Transformer

A photo of a collection of cut wires
A photo of a yellow element on a circuit board.

This transformer has multiple sets of windings and is used in a power supply to create multiple output AC voltages from a single AC input such as a wall outlet.

The small wires nearer the center are “high impedance” turns of magnet wire. These windings carry a higher voltage but a lower current. They’re protected by several layers of tape, a copper-foil electrostatic shield, and more tape.

The outer “low impedance” windings are made with thicker insulated wire and fewer turns. They handle a lower voltage but a higher current.

All of the windings are wrapped around a black plastic bobbin. Two pieces of ferrite ceramic are bonded together to form the magnetic core at the heart of the transformer.

This article appears in the February 2023 print issue.