4D printing is more real than you can think

3D printing is the current hype in the tech world. People are amazed with the ability to print their imagination in 3D and do all kind of stuff with it. Its a boon for artists and innovators. While the world is looking to expand the horizon of 3D printing, there is a group of people who are thinking about 4D printing.
4D printings adds the dimension of time to materials i.e. programmable materials which can self assemble or disassemble in real time depending on the type of stimuli. The idea of 4D printing comes from shape memory alloys which used thermoelastic displacive transformation like thermoelastic martensitic transformation to change shape with stimuli.
But advances in 4D printing is going to herald a new era of materials that can build themselves. The MIT's Self Assembly lab is working on the technology of 4D printing. They are currently printing interwoven materials with different thermal properties thus on exposing to temperature change they tend to behave similar to shape memory alloys.

Graphene - the new kevlar?

A team of researchers working at Rice University in the U.S. has demonstrated that graphene is better able to withstand the impact of a bullet than either steel or Kevlar. In their paper published in the journal Science, the team describes how they set up a miniature firing range in their laboratory and used it to test the strength of graphene sheets.It has always been known that graphene sheets are tough and stronger than conventional materials like Steel. But we have only able to produce very small quantity of graphene. Thus, to check its strength as a armour the researcher either had to produce large amount of graphene or scale down the bullets. They did the late, that to at a very small scale.
They use a laser to vapourise gold particles which acted as the gunpowder and used micro bullets of the size of a few microns and fired in on 10-100 sheets of Graphene stacked as a mat.
The whole experiment was recorded in slow motion and the bullets travelled at a speed of 6750 mph.
 Graphene dissipated the energy just like a trampoline by stretching back, and absorbed 0.92MJ/kg as compared to 0.08MJ/kg for Steel.
This might prove that Graphene is better at the small scale but what about the defects and dislocations introduced as you increase in volume. All materials tend to weaken out when compared with their whiskers or samples at nano or micrometer sizes. 

3D Carbon Goes Metallic

New metallic structure may be stable at ambient temperature and pressure with potential applications in science and technology.

A theoretical, three-dimensional (3D) form of carbon that is metallic under ambient temperature and pressure has been discovered by an international research team.

The findings, which may significantly advance carbon science, are published online this week in the Early Edition of the Proceedings of the National Academy of Sciences.

Carbon science is a field of intense research. Not only does carbon form the chemical basis of life, but it has rich chemistry and physics, making it a target of interest to material scientists. From graphite to diamond to Buckminster fullerenes, nanotubes and graphene, carbon can display in a range of structures.

But the search for a stable three-dimensional form of carbon that is metallic under ambient conditions, including temperature and pressure, has remained an ongoing challenge for scientists in the field.

Researchers from Peking University, Virginia Commonwealth University and Shanghai Institute of Technical Physics employed state-of-the-art theoretical methods to show that it is possible to manipulate carbon to form a three-dimensional metallic phase with interlocking hexagons.

“The interlocking of hexagons provides two unique features – hexagonal arrangement introduces metallic character, and the interlocking form with tetrahedral bonding guarantees stability,” said co-lead investigator Puru Jena, Ph.D., distinguished professor of physics in the VCU College of Humanities and Sciences.

The right combination of these properties could one day be applied to a variety of technologies.

“Unlike high-pressure techniques that require three terapascals of pressure to make carbon metallic, the studied structures are stable at ambient conditions and may be synthesized using benzene or polyacenes molecules,” said co-lead investigator Qian Wang, Ph.D., who holds a professor position at Peking University and an adjunct faculty position at VCU.

“The new metallic carbon structures may have important applications in lightweight metals for space applications, catalysis and in devices showing negative differential resistance or superconductivity,” Wang said.

According to Jena, the team is still early in its discovery process, but hope that these findings may move the work from theory to the experimental phase