Mechanical engineers Shervin Foroughi and Mohsen Habibi were painstakingly maneuvering a tiny ultrasound wand over a pool of liquid when they first saw an icicle shape emerge and solidify.
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Most commercial forms of 3-D printing involve extruding fluid materials—plastics, ceramics, metals or even biological compounds—through a nozzle and hardening them layer-by-layer to form computer-drafted structures. That hardening step is key, and it relies on energy in the form of light or heat.
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Using ultrasound to trigger chemical reactions in room-temperature liquids isn’t new in itself. The field of sonochemistry and its applications, which matured in the 1980s at the University of Illinois Urbana-Champaign (UIUC), relies on a phenomenon called acoustic cavitation. This happens when ultrasonic vibrations create tiny bubbles, or cavities, within a fluid. When these bubbles collapse, the vapors inside them generate immense temperatures and pressures; this applies rapid heating at minuscule, localized points.
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In their experiments, which were published in Nature Communications in 2022, the researchers filled a cylindrical, opaque-shelled chamber with a common polymer (polydimethylsiloxane, or PDMS) mixed with a curing agent. They submerged the chamber in a tank of water, which served as a medium for the sound waves to propagate into the chamber (similar to the way ultrasound waves from medical imaging devices travel through gel spread on a patient’s skin). Then, using a biomedical ultrasound transducer mounted to a computer-controlled motion manipulator, the scientists traced the ultrasound beam’s focal point along a calculated path 18 millimeters deep into the liquid polymer. Tiny bubbles started to appear in the liquid along the transducer’s path, and solidified material quickly followed. After fastidiously trying many combinations of ultrasound frequencies, liquid viscosity and other parameters, the team finally succeeded in using the approach to print maple-leaf shapes, seven-toothed gears and honeycomb structures within the liquid bath. The researchers then repeated these experiments using various polymers and ceramics, and they presented their results at the Canadian Acoustical Association’s annual conference this past October.
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A crucial next step for sound-based printing would be to show how this process can function in real applications that meet the strict requirements of engineers and product designers, such as materials strength, surface finish and repeatability.
The research team will soon publish new work that discusses improvements in printing speed and, significantly, resolution. In the 2022 paper the team demonstrated the ability to print “pixels” that measure 100 microns on a side. In comparison, traditional 3-D printing can achieve pixels half that size.
Balls of human brain cells linked to a computer have been used to perform a very basic form of speech recognition. The hope is that such systems will use far less energy for AI tasks than silicon chips.
“This is just proof-of-concept to show we can do the job,” says Feng Guo at Indiana University Bloomington. “We do have a long way to go.”
Brain organoids are lumps of nerve cells that form when stem cells are grown in certain conditions. “They are like mini-brains,” says Guo.
It takes two or three months to grow the organoids, which are a few millimetres wide and consist of as many as 100 million nerve cells, he says. Human brains contain around 100 billion nerve cells.
The organoids are then placed on top of a microelectrode array, which is used both to send electrical signals to the organoid and to detect when nerve cells fire in response. The team calls its system “Brainoware”.
For the speech recognition task, the organoids had to learn to recognise the voice of one individual from a set of 240 audio clips of eight people pronouncing Japanese vowel sounds. The clips were sent to the organoids as sequences of signals arranged in spatial patterns.
The organoids’ initial responses had an accuracy of around 30 to 40 per cent, says Guo. After training sessions over two days, their accuracy rose to 70 to 80 per cent.
“We call this adaptive learning,” he says. If the organoids were exposed to a drug that stopped new connections forming between nerve cells, there was no improvement.
The training simply involved repeating the audio clips, and no form of feedback was provided to tell the organoids if they were right or wrong, says Guo. This is what is known in AI research as unsupervised learning.
There are two big challenges with conventional AI, says Guo. One is its high energy consumption. The other is the inherent limitations of silicon chips, such as their separation of information and processing.
Titouan Parcollet at the University of Cambridge, who works on conventional speech recognition, doesn’t rule out a role for biocomputing in the long run.
“However, it might also be a mistake to think that we need something like the brain to achieve what deep learning is currently doing,” says Parcollet. “Current deep-learning models are actually much better than any brain on specific and targeted tasks.”
Guo and his team’s task is so simplified that it is only identifies who is speaking, not what the speech is, he says. “The results aren’t really promising from the speech recognition perspective.”
Even if the performance of Brainoware can be improved, another major issue with it is that the organoids can only be maintained for one or two months, says Guo. His team is working on extending this.
“If we want to harness the computation power of organoids for AI computing, we really need to address those limitations,” he says.
23andMe is a terrific concept. In essence, the company takes a sample of your DNA and tells you about your genetic makeup. For some of us, this is the only way to learn about our heritage. Spotty records, diaspora, mistaken family lore and slavery can make tracing one’s roots incredibly difficult by traditional methods.
What 23andMe does is wonderful because your DNA is fixed. Your genes tell a story that supersedes any rumors that you come from a particular country or are descended from so-and-so.
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ou can replace your Social Security number, albeit with some hassle, if it is ever compromised. You can cancel your credit card with the click of a button if it is stolen. But your DNA cannot be returned for a new set — you just have what you are given. If bad actors steal or sell your genetic information, there is nothing you can do about it.
This is why 23andMe’s Oct. 6 data leak, although it reads like science fiction, is not an omen of some dark future. It is, rather, an emblem of our dangerous present.
23andMe has a very simple interface with some interesting features. “DNA Relatives” matches you with other members to whom you are related. This could be an effective, thoroughly modern way to connect with long-lost family, or to learn more about your origins.
But the Oct. 6 leak perverted this feature into something alarming. By gaining access to individual accounts through weak and recycled passwords, hackers were able to create an extensive list of people with Ashkenazi heritage. This list was then posted on forums with the names, sex and likely heritage of each member under the title “Ashkenazi DNA Data of Celebrities.”
First and foremost, collecting lists of people based on their ethnic backgrounds is a personal violation with tremendously insidious undertones. If you saw yourself and your extended family on such a list, you would not take it lightly.
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I find it troubling because, in 2018, Time reported that 23andMe had sold a $300 million stake in its business to GlaxoSmithKline, allowing the pharmaceutical giant to use users’ genetic data to develop new drugs. So because you wanted to know if your grandmother was telling the truth about your roots, you spat into a cup and paid 23andMe to give your DNA to a drug company to do with it as they please.
Although 23andMe is in the crosshairs of this particular leak, there are many companies in murky waters. Last year, Consumer Reports found that 23andMe and its competitors had decent privacy policies where DNA was involved, but that these businesses “over-collect personal information about you and overshare some of your data with third parties…CR’s privacy experts say it’s unclear why collecting and then sharing much of this data is necessary to provide you the services they offer.”
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. As it stands, your DNA can be weaponized against you by law enforcement, insurance companies, and big pharma. But this will not be limited to you. Your DNA belongs to your whole family.
Pretend that you are going up against one other candidate for a senior role at a giant corporation. If one of these genealogy companies determines that you are at an outsized risk for a debilitating disease like Parkinson’s and your rival is not, do you think that this corporation won’t take that into account?
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Insurance companies are not in the business of losing money either. If they gain access to such a thing that on your record, you can trust that they will use it to blackball you or jack up your rates.
In short, the world risks becoming like that of the film Gattaca, where the genetic elite enjoy access while those deemed genetically inferior are marginalized.
The train has left the station for a lot of these issues. That list of people from the 23andMe leak cannot put the genie back in the bottle. If your DNA is on a server for one of these companies, there is a chance that it has already been used as a reference or to help pharmaceutical companies.
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There are things they can do now to avoid further damage. The next time a company asks for something like your phone number or SSN, press them as to why they need it. Make it inconvenient for them to mine you for your Personal Identifiable Information (PII). Your PII has concrete value to these places, and they count on people to be passive, to hand it over without any fuss.
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The time to start worrying about this problem was 20 years ago, but we can still affect positive change today. This 23andMe leak is only the beginning; we must do everything possible to protect our identities and DNA while they still belong to us.
Scientific American was warning about this since at least 2013. What have we done? Nothing.:
If there’s a gene for hubris, the 23andMe crew has certainly got it. Last Friday the U.S. Food and Drug Administration (FDA) ordered the genetic-testing company immediately to stop selling its flagship product, its $99 “Personal Genome Service” kit. In response, the company cooed that its “relationship with the FDA is extremely important to us” and continued hawking its wares as if nothing had happened. Although the agency is right to sound a warning about 23andMe, it’s doing so for the wrong reasons.
Since late 2007, 23andMe has been known for offering cut-rate genetic testing. Spit in a vial, send it in, and the company will look at thousands of regions in your DNA that are known to vary from human to human—and which are responsible for some of our traits
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Everything seemed rosy until, in what a veteran Forbes reporter calls “the single dumbest regulatory strategy [he had] seen in 13 years of covering the Food and Drug Administration,” 23andMe changed its strategy. It apparently blew through its FDA deadlines, effectively annulling the clearance process, and abruptly cut off contact with the agency in May. Adding insult to injury the company started an aggressive advertising campaign (“Know more about your health!”)
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But as the FDA frets about the accuracy of 23andMe’s tests, it is missing their true function, and consequently the agency has no clue about the real dangers they pose. The Personal Genome Service isn’t primarily intended to be a medical device. It is a mechanism meant to be a front end for a massive information-gathering operation against an unwitting public.
Sound paranoid? Consider the case of Google. (One of the founders of 23andMe, Anne Wojcicki, is presently married to Sergei Brin, the founder of Google.) When it first launched, Google billed itself as a faithful servant of the consumer, a company devoted only to building the best tool to help us satisfy our cravings for information on the web. And Google’s search engine did just that. But as we now know, the fundamental purpose of the company wasn’t to help us search, but to hoard information. Every search query entered into its computers is stored indefinitely. Joined with information gleaned from cookies that Google plants in our browsers, along with personally identifiable data that dribbles from our computer hardware and from our networks, and with the amazing volumes of information that we always seem willing to share with perfect strangers—even corporate ones—that data store has become Google’s real asset
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23andMe reserves the right to use your personal information—including your genome—to inform you about events and to try to sell you products and services. There is a much more lucrative market waiting in the wings, too. One could easily imagine how insurance companies and pharmaceutical firms might be interested in getting their hands on your genetic information, the better to sell you products (or deny them to you).
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ven though 23andMe currently asks permission to use your genetic information for scientific research, the company has explicitly stated that its database-sifting scientific work “does not constitute research on human subjects,” meaning that it is not subject to the rules and regulations that are supposed to protect experimental subjects’ privacy and welfare.
Those of us who have not volunteered to be a part of the grand experiment have even less protection. Even if 23andMe keeps your genome confidential against hackers, corporate takeovers, and the temptations of filthy lucre forever and ever, there is plenty of evidence that there is no such thing as an “anonymous” genome anymore. It is possible to use the internet to identify the owner of a snippet of genetic information and it is getting easier day by day.
This becomes a particularly acute problem once you realize that every one of your relatives who spits in a 23andMe vial is giving the company a not-inconsiderable bit of your own genetic information to the company along with their own. If you have several close relatives who are already in 23andMe’s database, the company already essentially has all that it needs to know about you.
The following is an extract from our Lost in Space-Time newsletter. Each month, we hand over the keyboard to a physicist or two to tell you about fascinating ideas from their corner of the universe. You can sign up for Lost in Space-Time for free here.
Space-time is a curious thing. Look around and it’s easy enough to visualise what the space component is in the abstract. It’s three dimensions: left-right, forwards-backwards and up-down. It’s a graph with an…
x, y and z axis. Time, too, is easy enough. We’re always moving forwards in time so we might visualise it as a straight line or one big arrow. Every second is a little nudge forwards.
But space-time, well that’s a little different. Albert Einstein fused space and time together in his theories of relativity. The outcome was a new fabric of reality, a thing called space-time that permeates the universe. How gravity works popped out of the explorations of this new way of thinking. Rather than gravity being a force that somehow operates remotely through space, Einstein proposed that bodies curve space-time, and it is this curvature that causes them to be gravitationally drawn to each other. Our very best descriptions of the cosmos begin with space-time.
Yet, visualising it is next to impossible. The three dimensions of space and one of time give four dimensions in total. But space-time itself is curved, as Einstein proposed. That means to really imagine it, you need a fifth dimension to curve into.
Luckily, all is not lost. There is a mathematical trick to visualising space-time that I’ve come up with. It’s a simplified way of thinking that not only illustrates how space-time can be curved, but also how such curvature can draw bodies towards each other. It can give you new insight into how gravity works in our cosmos.
First, let’s start with a typical way to draw space-time. Pictures like the one below are meant to illustrate Einstein’s idea that gravity arises in the universe from massive objects distorting space-time. Placing a small object, say a marble, near one of these dimples would result in it rolling towards one of the larger objects, in much the same way that gravity pulls objects together.
The weight of different space objects influences the distortion of space-and-time
Manil Suri
However, the diagram is missing a lot. While the objects depicted are three dimensional, the space they’re curving is only two dimensional. Moreover, time seems to have been entirely omitted, so it’s pure space – not space-time – that’s curving.
Here’s my trick to get around this: simplify things by letting space be only one dimensional. This makes the total number of space-time dimensions a more manageable two.
Now we can represent our 1-D space by the double-arrowed horizontal line in the left panel of the diagram below. Let time be represented by the perpendicular direction, giving a two-dimensional space-time plane. This plane is then successive snapshots, stacked one on top of the other, of where objects are located in the single space dimension at each instant.
Suppose now there are objects – say particles – at points A and B in our universe. Then if these particles remained at rest, their trajectories through space-time would just be the two parallel paths AA’ and BB’ as shown. This simply represents the fact that for every time instant, the particles remain exactly where they are in 1-D space. Such behaviour is what we’d expect in the absence of gravity or any other forces.
However, if gravity came into play, we would expect the two particles to draw closer to each other as time went on. In other words, A’ would be much closer to B’ than A was to B.
Now what if gravity, as Einstein proposed, wasn’t a force in the usual sense? What if it couldn’t act directly on A and B to bring them closer, but rather, could only cause such an effect by deforming the 2-D space-time plane? Would there be a suitable such deformation that would still result in A’ getting closer to B’?
Manil Suri
The answer is yes. Were the plane drawn on a rubber sheet, you could stretch it in various ways to easily verify that many such deformations exist. The one we’ll pick (why exactly, we’ll see below) is to wrap the plane around a sphere, as shown in the middle panel. This can be mathematically accomplished by the same method used to project a rectangular map of the world onto a globe. The formula this involves (called the “equirectangular projection”) has been known for almost two millennia: vertical lines on the rectangle correspond to lines of longitude on the sphere and horizontal ones to lines of latitude. You can see from the right panel that A’ has indeed gotten closer to B’, just as we might expect under gravity.
On the plane, the particles follow the shortest paths between A and A’, and B and B’, respectively. These are just straight lines. On the sphere, the trajectories AA’ and BB’ still represent shortest distance paths. This is because the shortest distance between two points on a spherical surface is always along one of the circles of maximal radius (these include, e.g., lines of longitude and the equator). Such curves that produce the shortest distance are called geodesics. So the geodesics AA’ and BB’ on the plane get transformed to corresponding geodesics on the sphere. (This wouldn’t necessarily happen for an arbitrary deformation, which is why we chose our wrapping around the sphere.)
Einstein postulated that particles not subject to external forces will always move through space-time along such “shortest path” geodesics. In the absence of gravity, these geodesics are just straight lines. Gravity, when introduced, isn’t counted as an external force. Rather, its effect is to curve space-time, hence changing the geodesics. The particles now follow these new geodesics, causing them to draw closer.
This is the key visualisation afforded by our simplified description of space-time. We can begin to understand how gravity, rather than being a force that acts mysteriously at a distance, could really be a result of geometry. How it can act to pull objects together via curvature built into space-time.
The above insight was fundamental to Einstein’s incorporation of gravity into his general theory of relativity. The actual theory is much more complicated, since space-time only curves in the local vicinity of bodies, not globally, as in our model. Moreover, the geometry involved must also respect the fact that nothing can travel faster than the speed of light. This effectively means that the concept of “shortest distance” has to also be modified, with the time dimension having to be treated very differently from the space dimensions.
Nevertheless, Einstein’s explanation posits, for instance, that the sun’s mass curves space-time in our solar system. That is why planets revolve around the sun rather than flying off in straight lines – they are just following the curved geodesics in this deformed space-time.
This has been confirmed by measuring how light from distant astronomical sources gets distorted by massive galaxies. Space-time truly is curved in our universe, it’s not just a mathematical convenience.
There’s a classical Buddhist parable about a group of blind men relying only on touch to figure out an animal unfamiliar to them – an elephant. Space-time is our elephant here – we can never hope to see it in its full 4-D form, or watch it curve to cause gravity. But the simplified visualisation presented here can help us better understand it .
