Wearable Tech can be made using Inkjet printers

Researchers have found a new way to use inkjet printing technology to produce electronic circuits made of liquid metal alloys for soft robots and flexible electronics. However, new manufacturing techniques must be developed before soft machines become commercially feasible, said Rebecca Kramer, an assistant professor of mechanical engineering at Purdue University. 

"We want to create stretchable electronics that might be compatible with soft machines, such as robots that need to squeeze through small spaces, or wearable technologies that aren't restrictive of motion," she said. 

A new manufacturing approach focuses on using inkjet printing to create devices made of liquid alloys. "This process now allows us to print flexible and stretchable conductors onto anything, including elastic materials and fabrics," Kramer said.

WORKING

 Ultrasound is used to make the printable ink by dispersing the liquid metal in a non-metallic solvent, the ultrasound breaks up the bulk liquid metal into nanoparticles and this nanoparticle-filled ink is compatible with inkjet printing. 

"Liquid metal in its native form is not inkjetable," Kramer said. "So what we do is create liquid metal nanoparticles that are small enough to pass through an inkjet nozzle. Sonicating liquid metal in a carrier solvent, such as ethanol, both creates the nanoparticles and disperses them in the solvent. Then we can print the ink onto any substrate. The ethanol evaporates away so we are just left with liquid metal nanoparticles on a surface." 

The nanoparticles must be rejoined after printing and this is achieved by applying light pressure, which renders the material conductive. This step is necessary because the liquid metal nanoparticles are initially coated with oxidised gallium, which acts as a skin that prevents electrical conductivity. 

"But it's fragile, so when you apply pressure it breaks the skin and everything coalesces into one uniform film," Kramer said. "We can do this either by stamping or by dragging something across the surface, such as the sharp edge of a silicon tip" she added.

The process could make it possible to rapidly mass-produce large quantities of the film. Future research will explore how the interaction between the ink and the surface being printed on might be instrumental in the production of specific types of devices. 

"For example, how do the nanoparticles orient themselves on hydrophobic versus hydrophilic surfaces? How can we formulate the ink and exploit its interaction with a surface to enable self-assembly of the particles?" Kramer said. 

The researchers will also study and model how individual particles rupture when pressure is applied, providing information that could allow the manufacture of ultrathin traces and new types of sensors.

Source: Mumbai Mirror