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Self-Destructing Gadgets Made Not So Mission Impossible

New self-destruct mechanism that works within 10 seconds could protect laptops and other devices from theft or espionage

3 min read
A self-destruct mechanism based on an expanding polymer layer can destroy a silicon chip within 10 seconds
Gif: Muhammad Hussain/KAUST

Self-destruct options from the Mission: Impossible movies could become a reality for even the most common smartphones and laptops used by government officials or corporate employees. A new self-destruct mechanism can destroy electronics within 10 seconds through wireless commands or the triggering of certain sensors.

Many government agencies and corporations would value such an extra layer of security for computing devices that might get lost or stolen. But past experiments with self-destructing electronics have either relied on new specialized chip designs or have taken far longer than 10 seconds. By comparison, the new self-destruct mechanism proposed by researchers at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia can work swiftly and is compatible with the common semiconductor technology found in most electronic devices.

“The first customers would be the ones who need data protection: Intelligence communities, corporations, banks, hedge funds, social security administrations, collectors who handle massive data,” says Muhammad Mustafa Hussain, an electrical engineer at KAUST.

The self-destruct mechanism relies on an expandable polymer layer that can rapidly expand to around seven times its original volume when heated to temperatures above 80 degrees C. The heat that triggers the polymer expansion comes from heater electrodes that could draw power from the battery of a smartphone or laptop. Full details of the study will be published in an upcoming issue of the journal Advanced Materials Technologies.

Roughly 500 to 600 milliwatts supplied to the heater electrodes enables the polymer to expand and crumple the chip within 10 to 15 seconds, but even lower power values of around 300 milliwatts could do the job in just over a minute. Several experiments showed that the polymer’s rapid expansion can destroy an adjacent silicon chip up to 90 micrometers thick

“The expandable polymer expands much more and causes sufficient tension in the thin silicon—which is sitting on top of the polymer—so it simply crumples and then breaks,” Hussain says. 

The temperature needed to activate the self-destruct mechanism could even be tuned between 80-  and 250 degrees C by using different polymeric materials. This is because the polymer layer consists of polymeric microspheres holding small amounts of liquid hydrocarbon. The thermoplastic shells of the microspheres soften when heated beyond a critical temperature, and release the liquid hydrocarbon. The released hydrocarbon undergoes phase change from liquid to gas and leads to the rapid polymer layer expansion.

The KAUST researchers tested several different Mission: Impossible–style scenarios that could autonomously trigger the self-destruct mechanism as a matter of security. One experiment showed how a GPS sensor could trigger it if the device is moved more than 50 meters away from its starting point.

A second experiment automatically triggered the self-destruct mechanism with a light sensor that was illuminated by a desk lamp. That test mimicked a security scenario where the top secret device was moved out of a box and exposed to light. And a third experiment used a pressure sensor to mimic an event where the chip self-destructs because the device casing is forced open.

The fourth scenario tested the ability for an agent or some other person to remotely trigger the self-destruct command by using a smartphone app. When the researchers entered a password into the app, the chip was destroyed on demand.

Despite the promising early results, Hussain and his colleagues have much more testing in mind. For example, they plan to try out the self-destruct mechanism on printed circuit boards and magnetic hard drives. They also envision testing the expandable polymer’s capability to destroy multiple levels of stacked silicon wafers, or even just select layers.

The KAUST team also wants to demonstrate more localized self-destruct options. Careful positioning of the internal components, adjustment of the thickness values for the polymer layers, and different heater locations could restrict the destruction to specific device components such as a laptop’s memory chips.

Such a self-destruct mechanism could even potentially be retrofitted to existing laptop or desktop computers, Hussain says. He added that the overall cost of adding the self-destruct security mechanism would likely be about $15 or less, depending on volume.

Creating a self-destruct option that works quickly and is compatible with today’s semiconductor chips is no small trick. In 2015, Xerox PARC showed off a self-destructing chip made on strained glass that could shatter within 10 seconds when triggered by a laser. That was developed as part of the U.S. Defense Advanced Research Projects Agency’s (Darpa’s) Vanishing Programmable Resources program. But the downside of that approach is that it relies on a specialized chip design rather than being readily compatible with modern semiconductor chips.

The same DARPA program has also considered but not yet demonstrated using small etchant liquids stored in tiny microcavities that could dissolve device components. The University of Illinois lab of John Rogers has also tested the ability to dissolve chips with chemicals contained in microfluidic channels, but this self-destruct mechanism works more slowly than the rapidly expanding polymer approach.

The need to protect sensitive data from falling into the wrong hands will likely only continue to grow—and not just for the fictional character Ethan Hunt or real-life intelligence agencies. So even a self-destruct option that needs 10 seconds instead of five seconds should be welcome news.

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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.