Engineered brain tissue
Borrowing from microfabrication techniques used in the semiconductor industry, MIT and Harvard Medical School (HMS) engineers have developed what they say is a simple and inexpensive way to create three-dimensional brain tissues in a lab dish.
The technique yields tissue constructs that closely mimic the cellular composition of those in the living brain, the researchers said, which allows scientists to study how neurons form connections and to predict how cells from individual patients might respond to different drugs and paves the way for developing bioengineered implants to replace damaged tissue for organ systems.
Although researchers have had some success growing artificial tissues such as liver or kidney, the brain presents some unique challenges such as the spatial heterogeneity — there are so many kinds of cells, and they have intricate wiring.
Brain tissue includes many types of neurons, including inhibitory and excitatory neurons, as well as supportive cells such as glial cells. All of these cells occur at specific ratios and in specific locations. To mimic this architectural complexity in their engineered tissues, the researchers embedded a mixture of brain cells taken from the primary cortex of rats into sheets of hydrogel. They also included components of the extracellular matrix, which provides structural support and helps regulate cell behavior.
Those sheets were then stacked in layers, which can be sealed together using light to crosslink hydrogels. By covering layers of gels with plastic photomasks of varying shapes, the researchers could control how much of the gel was exposed to light, thus controlling the 3-D shape of the multilayer tissue construct.
This type of photolithography is also used to build integrated circuits onto semiconductors — a process that requires a photomask aligner machine, which costs tens of thousands of dollars. However, the team developed a much less expensive way to assemble tissues using masks made from sheets of plastic, similar to overhead transparencies, held in place with alignment pins.
The researchers believe this system is the first that includes all of the necessary features for building useful 3-D tissues: It is inexpensive, precise, and allows complex patterns to be generated. Many people could easily use this method for creating heterogeneous, complex gel structures.
Subatomic breakthrough for quantum computing
In what they say is a key step toward building a machine that promises to revolutionize computing, Princeton researchers have developed a method that they say could quickly and reliably transmit information through a computer using the power of subatomic particles. The finding could eventually allow engineers to build a working quantum computer. By using principles radically different from classical physics, quantum computers would allow mathematicians to solve problems impossible to approach with standard computers: factoring immense numbers, cracking codes or simulating molecular behavior.
Quantum computers take advantage of the strange behaviors of subatomic particles like electrons. By harnessing electrons as they spin, scientists could use the particles to form the basis for a new type of computing. The problem, though, is that these incredibly tiny electrons are hard to control. So far, scientists have only been able to harness extremely small numbers of them. But in a recent series of experiments, the Princeton team demonstrated a new approach that could eventually allow engineers to build quantum computers consisting of millions of quantum bits, or qubits.
The quest in quantum computing today is trying to build a larger system. To transfer information, the researchers used a stream of microwave photons to analyze a pair of electrons trapped in a tiny cage called a quantum dot. The “spin state” of the electrons — information about how they are spinning — serves as the qubit, a basic unit of information. The microwave stream allows the scientists to read that information.
Diamonds for nanomanufacturing
One of the most promising innovations of nanotechnology has been the ability to perform rapid nanofabrication using nanometer-scale tips and heating those tips can increase fabrication speeds. At the same time, high speed and high temperature have been known to blunt their atomically sharp points. However, research conducted by the University of Illinois, the University of Pennsylvania and Advanced Diamond Technologies has created a new type of nano-tip for thermal processing, made entirely made out of diamond.
Researchers have been imaging nanoscale objects with atomic force microscopes for two decades, which use nanometer-scale tips to feel the push and pull of individual atomic forces. Researchers have also been interested in using these tips to etch surfaces or deposit materials in nano-manufacturing processes, but one of the key challenges has been the reliability of the tips, especially with performing nano-writing on hard, semiconductor surfaces.
Using a process known as reactive ion etching, the researchers were able to create a new kind of diamond tip that is much more resistant to wear and heat than its silicon counterparts.
The robustness of these diamond-based probes under such harsh conditions — high temperatures and stresses in an oxidizing environment — exceeds anything the researchers had seen with other atomic force microscope probes. Being able to heat the tips without their degrading opens up the possibility for using them in new manufacturing processes.
To prove its robustness, the researchers scanned the 10-nanometer diamond tip over a surface for a distance of more than 1.2 meters and showed that it experienced essentially no wear over that distance. The scan distance is equal to 100 million times the size of the tip, which is equivalent of a person walking around the circumference of the earth four times, and doing so with no measurable wear.
The researchers believe that the new tip’s durability combined with the multifunctionality of a thermal probe will open up new applications for atomic force microscopes.
–Ann Steffora Mutschler