How Inkjet Printing Can Boost Smart Packaging and Wearable Electronics

Looking for cost-effective and eco-friendly ways to produce flexible circuits, scientist from the University of Barcelona came up with a new bonding technique using an inkjet printer with silver nanoparticles ink.

Smart Packaging Ink

With the growing demand for mobile devices, smart packaging, and wearable electronics, it sometimes seems as if new solutions in this field are popping up daily. But have you ever wondered why? Whilst customers want the necessary chips to be thinner, more flexible and efficient, industry and research are looking for ways to reduce costs and the environmental impact of the circuit fabrication processes. This is exactly what scientists from the University of Barcelona had in mind when coming up with their new bonding technique.

Killing Two Birds with One Stone Called Inkjet Printing

To put their method in a nutshell: They built intelligent flexible hybrid circuits from silver nanoparticles ink using an inkjet. But why did they choose an ink containing nanoparticles of silver? First of all, silver is a widely available material for industrial purposes. Plus, it is quite simple to reproduce nanoparticles into a stable ink that can easily be sintered. As the amount of silver used for the bonding technique was low enough, the researchers were able to lower the costs for the process.

The biggest goal of this project was to kill two birds with one stone. Precisely: The same equipment should be used for two purposes. By using inkjet printing for the circuitry AND bonding of the chips they aimed to improve the performance of standard silicon-based manufacturing:

“We developed several electronics circuits with inkjet printing, and many times we had to insert a surface mounted device (SMD) chip to reach the objectives. Our approach was to use the same machine for bonding that was used for the printed circuit”

– says Javier Arrese, one of the Spanish scientists.

When an Interface Absorbs Liquid like a Sponge

This is how they managed to achieve their aim: The researchers deposited silver ink droplets close to the overlapping area between the SMD device pads and the printed bottom conductive paths. The thin interface acted like the small voids of a sponge and absorbed the liquid. This, in turn, allowed the fluid to be drawn up from a surface. Then, the ink was able to flow through the interface.

Ink incorporating silver nanoparticles has a high electrical conductivity after the thermal process at very low temperatures. This is why the scientists could form an electrically conductive interconnection during the process. The biggest challenge, however, was obtaining high electrical contact values for all the SMD sizes. Finally, they succeeded in creating an intelligent flexible hybrid circuit on paper where different SMDs were assembled by silver nanoparticle ink.

When it comes to the effects of their invention, Arrese states:

“We believe that our work will improve the existing RF [radio frequency] tags, boost and promote smart packaging, enhance wearable electronics, flexible electronics, paper electronics…our results make us believe that everything is possible.”

Even besides this, the printing industry increasingly uses silver. Some weeks ago, we already reported about scientists from Michigan State University, who recognized the benefits of silver ink for the production von touchscreen displays .

What are your experiences with silver ink? Please leave us your comment in the section on the right.

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