In a new type of 3D printing researchers at NIST (the US National Institute of Standards and Technology) have developed a method to use beams of electrons or X-rays to grow gels in a liquid.
What does it mean?
3D printing is better described as additive manufacturing, as contrasted with subtractive manufacturing. In subtractive manufacturing a large piece of material is whittled away and reduced to the desired shape, inevitably resulting in wasted material. In additive manufacturing the desired object is built up by adding material exactly where it is needed; some waste may still result due to, for example, the need for scaffolding to support the object as it is created, but usually additive manufacturing enables the creation of objects we can’t make with subtractive manufacturing.
Two major processes for additive manufacturing are extrusion or jetting, where a substance, usually heated to make it flow, is deposited into the desired share, and solidification, where radiation is used to selectively solidify a liquid or powder material.
This new solidification method uses a liquid of polymers and results in a gel, which is a soft solid. Such methods for creating gels have been used before, but this new method uses X-rays, rather than ultraviolet or visible laser light and does not require the addition of special molecules in the liquid to initiate the formation of gels.
Types of engineering can be roughly distinguished by the branch of physics they rely on: for example, mechanical engineering on mechanics, civil engineering on statics, and electrical engineering on electricity. Chemical engineering is unique in relying on chemistry. Increasingly, however, all engineering areas, not just biological engineering, are realizing that biology is an important science, whether as a source of ideas through biomimicry or as an important area of application.
This new method of solidification relies on physics, especially the physics of electromagnetic radiation. Such radiation varies from the longest wavelength radiation used for radio transmission to the shortest wavelength radiation called gamma rays. Visible light is about in the middle of that spectrum, with ultraviolet and X-ray moving toward shorter wavelength. The important fact from physics for this new NIST method is that the shorter wavelength of X-ray radiation means that it can be focused more accurately and thus can create finer structures than those created using visible or ultraviolet radiation.
However, the use of such short wavelength radiation requires a vacuum, and the liquid of polymers would evaporate. The researchers applied their knowledge of chemistry to add an ultrathin barrier of silicon nitride, a compound of silicon and nitrogen with a very high melting point, making it useful in this application. The NIST article states: “The method enabled the team to use the 3D-printing approach to create gels with structures as small as 100 nanometers (nm) — about 1,000 times thinner than a human hair. By refining their method, the researchers expect to imprint structures on the gels as small as 50 nm, the size of a small virus.”
Finally, biology is the expected application area for this new technique. The NIST article concludes: “Some future structures made with this approach could include flexible injectable electrodes to monitor brain activity, biosensors for virus detection, soft micro-robots, and structures that can emulate and interact with living cells and provide a medium for their growth.”
Our human fascination for robots began with envisioning creations using mechanical and electronic components, based on physics. Think of real applications in prosthetic limbs and pacemakers and think of science fiction creations such as cyborgs in movies. This brief look at cyborgs in film argues that the Tin Man in the movie The Wizard of Oz was the first film cyborg.
But that article points out that the Tin Man wanted that softer piece of human anatomy, a heart. That desire points to the new frontier in human-machine creations. Beyond the notions of wetware (the human body is like computer software) or liveware (you need a human to run any software) lie the frontiers of transhumanism (we should consciously use technology to evolve new humans) and extreme forms of biohacking (you can change your body now to extend its capabilities).
What does it mean for you?
Physics plus chemistry plus biology equals exciting new developments that will eventually create new forms of robots and cyborgs. The new process NIST creates a gel, a soft solid, and such gels have many applications. New structures (for example sol-gel derived products, made from a solution and a gel) are being developed that combine hardness and porosity, stiffness and flexibility, and inertness and reactivity. Sensor and battery technology will benefit but so will the detection and cure of human ailments and frailties.
Another lesson for us all is that progress often occurs at the interfaces between fields. If I were starting over my career as an engineer, I would learn more chemistry and biology. In your career and in the people you hire, look for those who can span fields.
Where can you learn more?
I often recommend the magazine New Scientist if you want to follow developments in science, but NIST newsletters are also exciting ways to learn about these new frontiers. Unfortunately NIST doesn’t seem to have one place listing all its blogs and newsletters, but almost every topic area seems to have some subscription service, from forensic science to weights and measures.
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