Kudos to the team at North Carolina State University (and the National Science Foundation for sponsoring the research) for coming up with an interesting paper and an entertaining video on 3D printing with liquid metals.
The build up of the finished part is occurring through depositing of small drops of binary eutectic alloy of gallium and indium (EGaIn, 75% Ga 25% In by weight) which is conductive and liquid at room temperature (slightly below, actually ∼15.7°C) . The 3D printer is essentially a microscope positioning stage with a third axis attached, which is carrying a syringe with the liquid alloy. The alloy is being deposited through a needle approx 250um in diameter.
Each droplet is coalescing into a sphere due to surface tension and each is quickly forming a thin protective layer (only about 1nm ) of passivating skin composed of Gallium oxide.
Be sure to check out the video for the samples of the shapes that can be printed with this technique. This is an early development stage yet and I’m sure we’ll see more interesting results come out soon. Some of the improvements that are in works have to do with devising ways to prevent the spherical droplets from further coalescing into larger diameter spheres instead of staying where they’ve been deposited.
3D-printed microstructure build with liquid metal
No less intriguing are the 2D applications of the same technology – the droplets can be stretched into thin wires from 30 to 200um in diameter to build electronic circuits using CNC positioning of the depositing syringe.
Check out the 3D Printing of Free Standing Liquid Metal Microstructures paper for more details on the fascinating new technology.
On a personal note: I had no idea how affordable indium and gallium are (in quantities needed for a DIY lab, of course) – they are about $1 / gram each and eBay is full of offers. Definitely something within the reach of an adventurous DIY 3D printing enthusiast! 🙂
Interesting concept of self-folding device. I would not go as far as to call it a “robot” per se because its movement function which is enabled by the motor and the battery, all added after the fact manually, are secondary (IMHO) to the ability to fold, which is what’s cool about it. From the soundtrack to the video, the shape memory polymers are bent into final position by temperature created with appox 2A current though what looks like a graphite infused part of the polymer sheet.
I don’t know how useful the technique would be specifically in robotics but this may actually be useful for electronic devices that require an enclosure. The shape memory polymer could be made to become both the PCB for the electronics as well as the enclosure, in which the components would be mounted on the inside. A pick-n-place robot can populate the SMD parts on the inner side of the device, then, while the device is in the reflow oven, the sides will fold around to form an enclosure. Interesting… Gotta read up more on the shape memory polymers, much depends on the temperatures required for the shape recall.
Here is a detailed and well-illustrated overview of using Eclipse IDE as an AVR development platform by Sulaiman Salim Marhoun Al Habsi:
Using eclipse AVR application development plug in. at sulimanhabsi blog.
It is a second post about Eclipse on his blog and it shows a different approach to how many, if not most, DIY electronics and robotics hobbyists come to program Atmel chips – start with ATmega168 or ATmega328 in the form of an Arduino board and use Arduino IDE and Wiring version of C programming language as a starting point. Arduino IDE can be adapted for using it with other Atmel chips, such as ATMega8 which Sulaiman used as an example, and many if not most other Atmel MCU. The only ones missing Arduino IDE support (to the best of my knowledge) are the smallest of the AVRs – ATtiny12 , ATtiny10, 9, 5 and ATtiny4. I am wondering if Eclipse plugin for AVR is better it terms of the chips supported.
Anyway, if you program other things in C (or Java or whatever else for that matter that also has an Eclipse plugin) and have a need to program AVR chips, you may want to check out his blog for some useful pointers on setting Eclipse up for AVR and then using it to program the chips.