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Printed, Flexible, and Organic Wearable Sensors Worth $244 Million in 10 Years

A new generation of electronic sensors could revolutionize wearable gadgets and smart retail packaging

2 min read
Printed, Flexible, and Organic Wearable Sensors Worth $244 Million in 10 Years
Photo-illustration: Maciej Frolow/Getty Images

Wearable sensors capable of checking someone's heart rate or breathing may not rely on traditional microchip technology in the near future. Instead, the next generation of printed, flexible, and organic electronic sensors could enable new medical and athletic wearable devices in a market worth an estimated $244 million within a decade, according to market analysis firm Lux Research.

The forecast comes from a new report by Lux that envisions how such printed, flexible, and organic electronic (PFOE, they call it) sensors can best fit a future where tens of billions of wirelessly-connected devices form an "Internet of Things" that include smart building thermostats, smart cars, and wearable devices. The report identifies a $400 million market for PFOE sensors by 2024 in the likeliest scenario, but other scenarios have projections ranging from $96 million to $1 billion.

Such a market includes the estimated $244 million for wearables used by athletes and medical patients—the likeliest area for new PFOE sensors to gain traction over traditional CMOS sensors. 

In both wearable cases, the sensors could monitor vital signs such as body temperature, heart rate, and respiration. Pressure sensors could even help develop proper balance in a golf swing or monitor elderly patients' walking patterns for signs of Parkinson's or multiple sclerosis.

Retail sector applications such as smart food packaging or monitoring store inventory represent the second largest opportunity for PFOE sensors, according to Lux, with an estimated market of $117 million by 2024. Printed electronics could provide a lower-cost option for flashy promotional product packaging, such as the light-up Cheerio box developed by Fulton Innovation in 2011. More critically, temperature sensors could monitor perishable foods and medical vaccines in storage. Chemical sensors might even sniff for signs of food gone bad and provide up-to-date information that beats static expiration dates.

Store managers might also be eager to take advantage of disposable, lower-cost PFOE sensors to track items on store shelves and see when they need to restock. Such item-level tracking of purchases might even enable customers to wheel a cart of goods directly to their car without stopping by the cashier. The PFOE sensors could also make large pressure sensor mats viable as a means of tracking customer shopping patterns within the store. Lux Research expects such retail sector opportunities to grow even faster than the wearable applications.

Smaller market opportunities exist for PFOE sensors in the transportation and building sectors with estimated markets worth $28 million and $11 million by 2024. Traditional CMOS sensors still have an advantage here because of their higher accuracy and reliability—traits that people generally want in their cars and buildings. But that has not stopped development of printed sensors that provide touch-based technologies for cabin control systems inside cars such as the Ford Fusion.

Overall, PFOE sensors look ready to compete against CMOS sensors based on their  larger area coverage, lower cost, lower power needs, and disposability, says Lux. Organic sensors could gain an edge over silicon or metal-based sensors as countries increasingly worry about the problem of e-waste cluttering landfills.

But Lux Research expects power consumption to play a decisive role in differentiating "winners" from "losers" among the competing sensors: It will be more decisive than sensor accuracy, precision, or size. After all, the need to frequently change or charge batteries can lead to higher labor costs for building maintenance and annoy owners of individual wearable devices. The expense of the power component in disposable applications—such as smart food packaging—will also determine the economic viability of such applications.

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The Inner Beauty of Basic Electronics

Open Circuits showcases the surprising complexity of passive components

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

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