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MIT researchers have invented a way to fabricate nanoscale 3-D objects of nearly any shape. They can also pattern the objects with a variety of useful materials, including metals, quantum dots, and DNA.
“It’s a way of putting nearly any kind of material into a 3-D pattern with nanoscale precision,” says Edward Boyden, an associate professor of biological engineering and of brain and cognitive sciences at MIT.
Using the new technique, the researchers can create any shape and structure they want by patterning a polymer scaffold with a laser. After attaching other useful materials to the scaffold, they shrink it, generating structures one thousandth the volume of the original.
These tiny structures could have applications in many fields, from optics to medicine to robotics, the researchers say. The technique uses equipment that many biology and materials science labs already have, making it widely accessible for researchers who want to try it.
Boyden, who is also a member of MIT’s Media Lab, McGovern Institute for Brain Research, and Koch Institute for Integrative Cancer Research, is one of the senior authors of the paper, which appears in the Dec. 13 issue of Science. The other senior author is Adam Marblestone, a Media Lab research affiliate, and the paper’s lead authors are graduate students Daniel Oran and Samuel Rodriques.
Implosion fabrication
Existing techniques for creating nanostructures are limited in what they can accomplish. Etching patterns onto a surface with light can produce 2-D nanostructures but doesn’t work for 3-D structures. It is possible to make 3-D nanostructures by gradually adding layers on top of each other, but this process is slow and challenging. And, while methods exist that can directly 3-D print nanoscale objects, they are restricted to specialized materials like polymers and plastics, which lack the functional properties necessary for many applications. Furthermore, they can only generate self-supporting structures. (The technique can yield a solid pyramid, for example, but not a linked chain or a hollow sphere.)
To overcome these limitations, Boyden and his students decided to adapt a technique that his lab developed a few years ago for high-resolution imaging of brain tissue. This technique, known as expansion microscopy, involves embedding tissue into a hydrogel and then expanding it, allowing for high resolution imaging with a regular microscope. Hundreds of research groups in biology and medicine are now using expansion microscopy, since it enables 3-D visualization of cells and tissues with ordinary hardware.
By reversing this process, the researchers found that they could create large-scale objects embedded in expanded hydrogels and then shrink them to the nanoscale, an approach that they call “implosion fabrication.”
As they did for expansion microscopy, the researchers used a very absorbent material made of polyacrylate, commonly found in diapers, as the scaffold for their nanofabrication process. The scaffold is bathed in a solution that contains molecules of fluorescein, which attach to the scaffold when they are activated by laser light.
Using two-photon microscopy, which allows for precise targeting of points deep within a structure, the researchers attach fluorescein molecules to specific locations within the gel. The fluorescein molecules act as anchors that can bind to other types of molecules that the researchers add.
“You attach the anchors where you want with light, and later you can attach whatever you want to the anchors,” Boyden says. “It could be a quantum dot, it could be a piece of DNA, it could be a gold nanoparticle.”
“It’s a bit like film photography—a latent image is formed by exposing a sensitive material in a gel to light. Then, you can develop that latent image into a real image by attaching another material, silver, afterwards. In this way implosion fabrication can create all sorts of structures, including gradients, unconnected structures, and multimaterial patterns,” Oran says.
Once the desired molecules are attached in the right locations, the researchers shrink the entire structure by adding an acid. The acid blocks the negative charges in the polyacrylate gel so that they no longer repel each other, causing the gel to contract. Using this technique, the researchers can shrink the objects 10-fold in each dimension (for an overall 1,000-fold reduction in volume). This ability to shrink not only allows for increased resolution, but also makes it possible to assemble materials in a low-density scaffold. This enables easy access for modification, and later the material becomes a dense solid when it is shrunk.
“People have been trying to invent better equipment to make smaller nanomaterials for years, but we realized that if you just use existing systems and embed your materials in this gel, you can shrink them down to the nanoscale, without distorting the patterns,” Rodriques says.
Currently, the researchers can create objects that are around 1 cubic millimeter, patterned with a resolution of 50 nanometers. There is a tradeoff between size and resolution: If the researchers want to make larger objects, about 1 cubic centimeter, they can achieve a resolution of about 500 nanometers. However, that resolution could be improved with further refinement of the process, the researchers say.
Another day, another tech company being disingenuous about its privacy practices. This time it’s Microsoft, after it was discovered that Windows 10 continues to track users’ activity even after they’ve disabled the activity-tracking option in their Windows 10 settings.
You can try it yourself. Pull up Windows 10’s Settings, go to the Privacy section, and disable everything in your Activity History. Give it a few days. Visit the Windows Privacy Dashboard online, and you’ll find that some applications, media, and even browsing history still shows up.
Application data found on the Windows Privacy Dashboard website
Screenshot: Brendan Hesse
Sure, this data can be manually deleted, but the fact that it’s being tracked at all is not a good look for Microsoft, and plenty of users have expressed their frustration online since the oversight was discovered. Luckily, Reddit user a_potato_is_missing found a workaround that blocks Windows and the Windows Store from tracking your PC activity, which comes from a tutorial originally posted by Tenforums user Shawn Brink.
We gave Brink’s strategy a shot and found it to be an effective workaround worth sharing for those who want to limit Microsoft’s activity-tracking for good. It’s a simple process that only requires you to download and open some files, but we’ll guide you through the steps since there a few caveats you’ll want to know.
How to disable the activity tracker in Windows 10
Brink’s method works by editing values in your Window Registry to block the Activity Tracker (via a .REG file). For transparency, here’s what changes the file makes:
These changes only apply to Activity Tracking and shouldn’t affect your operating system in any other way. Still, if something does go wrong, you can reverse this process, which is explained in step 7. To get started with Brink’s alterations:
Download the “Disable_Activity_history.reg” file from Brink’s tutorial to any folder you want.
Double-click on the .REG file to open it, and then click “Run” to begin applying the changes to your registry.
You will get the usual Window UAC notification to allow the file to make changes to your computer. Click “Yes.”
A warning box will pop up alerting you that making changes to your registry can result in applications and features not working, or cause system errors—all of which is true, but we haven’t run into any issues from applying this fix. If you’re cool with that, click “Yes” to apply the changes. The process should happen immediately, after which you’ll get one final dialogue box informing you of the information added to the registry. Click “OK” to close the file and wrap up the registry change.
After the registry edit is complete, you’ll need to sign out of Windows (press Windows Key+X then Shut down or Sign out>Sign out) then sign back in to apply the registry changes.
When you sign back in, your activity will no longer be tracked by Windows, even the stuff that was slipping through before.
To reverse the registry changes and re-enable the Activity Tracker, download the “Enable_Activity_history.reg” file also found on the Tenforums tutorial, then follow the same steps above.
Update 12/13/2018 at 12:30pm PT: Microsoft has released a statement to Neowin about the aforementioned “Activity History.” Here’s the statement from Windows & devices group privacy officer Marisa Rogers:
“Microsoft is committed to customer privacy, being transparent about the data we collect and use for your benefit, and we give you controls to manage your data. In this case, the same term ‘Activity History’ is used in both Windows 10 and the Microsoft Privacy Dashboard. Windows 10 Activity History data is only a subset of the data displayed in the Microsoft Privacy Dashboard. We are working to address this naming issue in a future update.”
As Neowin notes, Microsoft says there are two settings you should look into if you want to keep your PC from uploading your activity data:
“One is to go to Settings -> Privacy -> Activity history, and make sure that ‘Let Windows sync my activities from this PC to the cloud’ is unchecked. Also, you can go to Settings -> Privacy -> Diagnostics & feedback, and make sure that it’s set to basic.”
