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3D printing, printable circuits and wireless sensors

August 11, 2015

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3D printing has recently registered a surge in the constant attention it meets on the Internet.
Also called addictive manufacturing, the technique that has become viral implies sequential depositing of a material onto a powder bed via inkjet printer heads. Extrusion and sintering are more recent variations of the same concept that have broadened the sense of 3D printing.

A bit of 3D printing history

AM started in the 80s, when the STL (stereolithography) process was established, first by Hideo Kodama, then by Chuck Hull. The most common procedure, employed up to these days, was fused deposition modeling (a specialized application of plastic extrusion). Selective laser sintering, direct metal laser sintering and selective laser melting are methods used in metalworking, which also exist since the 80s, but transitioned into 3D printing in the first decade of the 2000s.

As for 3D printing in particular, a Massachusetts Institute of Technology team led by Emanuel Sachs developed it in the late 1980s. Also known as binder jetting, from the liquid binder used on the solidifiable areas, the technique seems to have waited for compatible procedures in order to attain its 2000s fame.

The most common material for 3D printing was plastic, but soon metal, sand, ceramics or even organic materials found their way into this process. There are currently 6 types of additive processes, the most expensive of them being those which work directly with metal alloys, using a mold to shape the metal parts.

Vehicle parts, construction models, medical implants and devices, tissue engineering, clothes, robotics and hardware – these are just the main categories where 3D experimentation evolved into industrial applications. Microscale and nanoscale 3D structures have also been produced.

In 2013, the German company Nanoscribe introduced the fastest commercial 3D printer. The same company installed a Nanoscribe 3D printer, the most precise printer yet for micro and nano-structures, at the Swiss Binnig and Rohrer Nanotechnology Center (BRNC), in July 2015.

The latest developments in 3D printing

Also in July 2015, the UC Berkley engineers, in collaboration with Taiwan’s National Chiao Tung University, came public with their proof-of-concept study for a milk container smart cap – claiming that the commercial barrier may soon be broken. In their vision, people will be able to download 3D printing files and use them for producing their own devices at home. The culminating point of this project consists in being able to print “basic electrical components, as well as a working wireless sensor”. Injected with silver particles and solidified to form metallic elements and interconnectors, these structures take the form of 3D resistors, capacitors or inductors, including circuits and passive wireless sensors.
Fitted with a capacitor and an inductor, the Berkley printed “smart cap” was able to form a resonant circuit. The smart milk cap wirelessly transmits shifts in frequency once the milk’s bacteria levels change, which warn consumers about their food deterioration levels.

The schematic diagrams may be visualized here, as well as other details.

Earlier projects

Thinfilm is another printed electronics company from Norway that unveiled a smart prototype whiskey bottle cap, using its new OpenSense technology. They pioneered in printing integrated circuits that would relieve the pressure for the industrial manufacturing of such circuits. Products tracking and information could be delivered via 3D printed circuits.

Since we are talking about modern electronics of extremely small size, the printing-at-home idea is still in its early stages. The process used by Thinfilm involves many moving parts, done on a single, multi-stage press at InkTec, in Korea (at their partner’s production site).

Future expectations in 3D printing

Metal parts are considered the only way to unlock the real capacities of 3D printing. Its productivity would expand if titanium, cobalt, nickel or aluminum alloys would involve less expensive processing methods. So far only the biomedical and aerospace industries have approached the AM techniques. Jewellery also uses selective laser melting (SLM).

An IDTechEx report lists pricing, properties and projections for the 3D printing of metals 2015-2025.

The goal seems to be 3D printed electronics, which could move the custom-tailored manufacturing process, selectively available now, straight into customers’ homes. Although it may seem like a long way to go from UC Berkley’s announcement a month ago, since such concepts bode well for IoT, the distance may be shorter than we imagine.

The smart cap proof-of-concept created such a buzz because it was deemed “the world’s first working electronic components to be 3-D printed”.

Exploring the implications of large-scale 3D printing, a 2011/2012 exhaustive article mentions the perspective of technical disciplines converging into the so-called NBIC – nanotechnology, biotechnology, information technology, and cognitive sciences. We are now 4 years later and the smart cap may not seem much in the eyes of the public, but it shows that the specialists are progressing towards their goals.

Another recent development consists of 3D printing of nanoscale objects using DNA strands. The goal here is creating DNA-sized structures capable of interacting with human molecules. The Swedish researchers used the DNA’s tendency of mimicking the polygonal 3D shapes, utilized so far in computer-designed 3D models.

The projects mentioned are important because they all point to the expected next industrial revolution, the IoT, AI and/or other projections for the future of industry and humanity.