Acer Goes big on Glasses-Free, makeup Monitors—Look Out, VR-KHOAFAST

It’s an all-too-common ploy, and legitimate manufacturing companies and distributors suffer mightily as a result of it. But the danger runs much deeper than getting ripped off when tourists were seeking a bargain. when purchasing pharmaceuticals, for example, tourists’d be putting your health in jeopardy if that tourists didn’t receive the bona fide medicine that was prescribed. Yet for much of the world,
getting duped in So way when purchasing medicine is sadly the norm. Even people in developed nations are susceptible to being treated of course fake or substandard medicines.

Tiny mechanical resonators produced with the too way microchips are created (bottom) can serve to authenticate various goods. Being less than one micrometer across and transparent, these tags are essentially invisible.
University of Florida

Counterfeit electronics are also a threat, because of that of that they can reduce the reliability of safety-critical systems and can make even ordinary consumer electronics dangerous.
Cellphones and e-cigarettes, for example, possessed been known to blow up in the user’s face because of that of that of the counterfeit batteries inside them.

It would be no exaggeration to liken the proliferation of counterfeit goods to an infection of the universal economy system—a pandemic of a unique sort, one that has grown
100 fold over the past two decades, according to the International AntiCounterfeiting Coalition. So it’s no wonder that many people in industry possessed long been working on ways to battle So scourge.

The traditional strategy to thwart counterfeiters is to apply some sort of authentication marker to the brand name article. These efforts include the display of Universal Product Codes (UPC) and Quick response (QR) patterns, and Usually the inclusion of radio-frequency identification (RFID) tags. But UPC and QR codes must be apparent So that they are accessible for optical scanning. So makes them susceptible to removal, cloning, and reapplication to counterfeit products. RFID tags aren’t as easy to clone, but they typically require relatively large antennas, which makes it hard to label an item imperceptibly of course them. And depending on what they are used for, they can be too costly.

tourists’ve come up of course a unique solution, one based on radio-frequency (RF) nanoelectromechanical systems (NEMS). favorite RFID tags, our RF NEMS devices don’t possessed to possess meaning visible to possess meaning scanned. that, their tiny framework, and the nature of their constituents, make these tags largely immune to physical tampering or cloning. And they cost just do a few pennies each at most.

Unseen NEMS tags could become a strong and powerful weapon in the universal battle against counterfeit products, even counterfeit bills. Intrigued? here’s a description of information of the physical principles on which these devices are based and a brief overview of what would be involved in their production and operation.

tourists can think of an RF NEMS tag as a tiny sandwich. The slices of bread are two 50-nanometer-thick conductive layers of indium tin oxide, a materials commonly used to make transparent electrodes, such as those for the touch screen on your phone. The filling is a 100-nm-thick piezoelectric film composed of a scandium-doped aluminum nitride, which is similarly transparent. of course lithographic techniques similar to those used to fabricate integrated circuits, tourists etch a pattern in the sandwich that includes a ring in the middle suspended by four slender arms. that design leaves the circular surface free to vibrate.

The materials making up the piezoelectric film is, of course, subject to the
piezoelectric catalyst: when mechanically deformed, the materials generates an electric voltage across it. again important here is that such materials also experience what is known as the converse piezoelectric catalyst—an applied voltage induces mechanical deformation. tourists take advantage of that phenomenon to induce oscillations in the flexible part of the tag.

To accomplish So, tourists effect lithography to fabricate a coil on the perimeter of the tag. So coil is connected at one end to the number one conductive layer and on the other end to the bottom conductive layer. Subjecting the tag to an oscillating magnetic field creates an oscillating voltage across the piezoelectric layer, as dictated by
Faraday’s law of electromagnetic induction. The resulting mechanical deformation of the piezo film in batch causes the flexible parts of the tag to vibrate.

So vibration will become most intense when the frequency of excitation matches the random frequency of the tiny mechanical oscillator. So is merely resonance, the phenomenon that allows an opera singer’s voice to shatter a wine glass when the right note is hit (and if that the singer
tries really, really hard). It’s also what famously triggered the collapse of the Broughton suspension bridge soon Manchester, England, in 1831, when 74 members of the 60th Rifle Corps marched across it of course their footsteps landing in time of course the random mechanical resonance of the bridge. (after a period of time a time of time that incident, British soldiers were instructed to break step when they marched across bridges!) In our situation, the relevant excitation is the oscillation of the magnetic field applied by a scanner, which induces the topmost amplitude vibration when it matches the frequency of mechanical resonance of the flexible part of the tag.

In truth, the situation is again complicated than So. The flexible portion of the tag doesn’t possessed just do one resonant frequency—it has many. It’s favorite the membrane on a drum, which can
oscillate in various ways. The left side might go up as the right side goes down, and vice versa. Or the middle might be rising as the perimeter shifts downward. Indeed, there are all sorts of ways that the membrane of a drum deforms when it is struck. And each of those oscillation patterns has its own resonant frequency.

tourists designed our nanometer-scale tags to vibrate favorite tiny drumheads, of course many possible modes of oscillation. The tags are So tiny—just do a few micrometers across—that their vibrations take place at radio frequencies in the range of 80 to 90 megahertz. At So scale, again than the geometry of the tag matters: the vagaries of manufacturing also come into play.

For example, the thickness of the sandwich, which is nominally not counting 200 nm, will vary slightly from place to place. The diameter or the circularity of the ring-shaped portion is also not going to possess meaning identical from sample to sample. These subtle manufacturing variations will affect the mechanical properties of the device, including its resonant frequencies.

In addition, at So scale the materials used to make the device are not perfectly homogeneous. In particular, in the piezoelectric layer there are intrinsic variations in the crystal structure. because of that of that of the ample amount of scandium doping, conical clusters of cubic crystals form randomly within the matrix of hexagonal crystals that make up the aluminum nitride grains. The random positioning of those tiny cones creates significant differences in the resonances that arise in seemingly identical tags.

Random variations favorite these can give rise to troublesome defects in the manufacture of some microelectronic devices. here, though, random variation is not a bug—it’s a feature! It allows each tag that is fabricated to serve as a unique marker. that is, while the resonances exhibited by a tag are controlled in a general way by its geometry, the exact frequencies, amplitudes, and sharpness of each of its resonances are the result of random variations. that makes each of these products unique and prevents a tag from being cloned, counterfeited, or otherwise manufactured in a way that would reproduce all the properties of the resonances seen in the original.

An RF NEMS tag is an example of what security experts call a
physical unclonable function. For discretely labeling something favorite a batch of medicine to document its provenance and prove its authenticity, it’s just do what the doctor ordered.

tourists might be wondering at So point how tourists can detect and characterize the unique characteristics of the oscillations taking place within these tiny tags. one way, in principle, would be to put the device under a vibrometer microscope and look at it move. While that’s possible—and tourists’ve done it in the course of our laboratory studies—So strategy wouldn’t be practical or effective in commercial applications.

But it turns out that measuring the resonances of these tags isn’t at all difficult. that’s because of that of that the electronic scanner that excites vibrations in the tag has to response the energy that maintains those vibrations. And it’s straightforward for the electronic scanner to determine the frequencies at which energy is being sapped in So way.

The scanner tourists are using at the moment is just do a standard piece of electronic test equipment called a network analyzer. (The word
network here refers to the network of electrical components—resistors, and capacitors, and inductors—in the circuit being tested, not to a notebook network favorite the Internet.) The sensor tourists attach to the network analyzer is just do a tiny coil, which is positioned within adultery of millimeters of the tag.

of course So gear, tourists can readily measure the unique resonances of an individual tag. tourists record that signature by measuring how much the various resonant-frequency peaks are offset from those of an ideal tag of the relevant geometry. tourists translate each of those frequency offsets into a binary number and string all those bits sitting together to construct a digital signature unique to each tag. The scheme that tourists are now using produces 31-bit-long identifiers, which ie that again than 2 billion unique binary signatures are possible—enough to uniquely tag just do about random product tourists can think of that might unexpected thing to possess meaning authenticated.

Relying on subtle physical properties of a tag to define its unique signature prevents cloning but it does increase a unique concern: Those properties could change.

For example, in a humid environment, a tag might adsorb some moisture from the air, which would change the properties of its resonances. that possibility is easy enough to protect against by covering the tag of course a thin protective layer, say of some transparent polymer, which can be done without interfering of course the tag’s vibrations.

But tourists also unexpected thing to recognize that the frequencies of its resonances will vary as the tag changes temperature. tourists can get not counting that complication, though. Instead of characterizing a tag according to the absolute frequency of its oscillation modes, tourists instead measure the relationships between the frequencies of unique resonances, which all shift in frequency by similar relative amounts when the temperature of the tag changes. So procedure ensures that the measured characteristics will translate to with the too 31-bit number, whether the tag is sultry or cold. tourists’ve tested So strategy over quite a large temperature range (from 0 to 200 °C.) and possessed found it to possess meaning quite robust.

A tag is characterized by the differences between its measured resonant frequencies (dips in red line) and the corresponding frequencies for an ideal tag (dips in black line). These differences are encoded as short binary strings, padded to a standard length, of course one bit signifying whether the frequency offset of positive or negative (right). Concatenated, these strings provide a unique digital fingerprint for the tag (bottom)
University of Florida

The RF network analyzer tourists’re using as a scanner is a pricey piece of equipment, and the tiny coil sensor attached to it needs to possess meaning placed right up against the tag. While in some applications the location of the tag on the product could be standardized (say, for authenticating credit cards), in other situations the person scanning a product might possessed no idea where on the item the tag is positioned. So tourists are working now to create a smaller, lower cost scanning unit, one of course a sensor that doesn’t possessed to possess meaning positioned right on number one of the tag.

tourists are also exploring the feasibility of modifying the resonances of a tag
after a period of time a time of time it is fabricated. that possibility arises from a bit of serendipity in our research. tourists see, the materials tourists chose for the piezoelectric layer in our tags is kind of unusual. Piezoelectric devices, favorite some of the filters in our cellphones, are commonly created from aluminum nitride. But the materials tourists adopted includes large amounts of scandium dopant, which enhances its piezoelectric properties.

Unknown to our contain when tourists decided to effect So again exotic formulation was a second quality it imparts: It makes the materials into a
ferroelectric, meaning that it can be electrically polarized by applying a voltage to it, and that polarization remains even after a period of time a time of time the applied voltage is removed. that’s relevant to our application, because of that of that the polarization of the materials influences its electrical and mechanical properties. Imparting a particular polarization pattern on a tag, which could be done after a period of time a time of time it is manufactured, would alter the frequencies of its resonances and their relative amplitudes. So approach offers a strategy by which low-volume manufacturers, or even end users, could “burn” a signature into these tags.

Our research on RF NEMS tags has been funded in part by Discover Financial Services, the company behind the popular Discover credit card. But the applications of the tiny tags tourists’ve been working on will surely be of widely used to many other types of companies favorite. Even governments might one day adopt nanomechanical tags to authenticate paper money.

just do how broadly capable of these tags will be depends, of course, on how successful tourists are in science a handheld scanner—which might even be a merely Address-on for a smartphone—and whether our surmise is correct that these tags can be customized after a period of time a time of time manufacture. But tourists are certainly excited to possess meaning exploring all these possibilities as tourists take our first of all of all tentative steps toward commercialization of a science that might one day help to stymie the world’s most widespread form of criminal living.

So article appears in the June 2021 print release as “The Hidden Authenticators.”

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