E-Textile by Printing an All-through Penetrating Copper Complex Ink.

Wearable electronics is an emerging field in academics and industry, in which electronic devices, such as smartwatches and sensors, are printed or embedded within textiles. The electrical circuits in electronics textile (e-textile) should withstand many cycles of bending and stretching. Direct printing of conductive inks enables the patterning of electrical circuits; however, while using conventional nanoparticle-based inks, printing onto the fabric results in a thin layer of a conductor, which is not sufficiently robust and impairs the reliability required for practical applications. Here, we present a new process for fabricating robust stretchable e-textile using a thermodynamically stable, solution-based copper complex ink, which is capable of full penetrating the fabric. After printing on knitted stretchable fabrics, they were heated, and the complex underwent an intermolecular self-reduction reaction. The continuously formed metallic copper was used as a seed layer for electroless plating (EP) to form highly conductive circuits. It was found that the stretching direction has a significant role in resistivity. This new approach enables fabricating e-textiles with high stretchability and durability, as demonstrated for wearable gloves, toward printing functional e-textile.

Measuring pupil size and light response through closed eyelids.

Monitoring pupillary size and light-reactivity is a key component of the neurologic assessment in comatose patients after stroke or brain trauma. Currently, pupillary evaluation is performed manually at a frequency often too low to ensure timely alert for irreversible brain damage. We present a novel method for monitoring pupillary size and reactivity through closed eyelids. Our method is based on side illuminating in near-IR through the temple and imaging through the closed eyelid. Successfully tested in a clinical trial, this technology can be implemented as an automated device for continuous pupillary monitoring, which may save staff resources and provide earlier alert to potential brain damage in comatose patients.

Plasma-Induced Decomposition of Copper Complex Ink for the Formation of Highly Conductive Copper Tracks on Heat-Sensitive Substrates.

The use of Cu-formate-2-amino-2-methyl-1-propanol ink and low-pressure plasma for the formation of highly conductive patterns on heat sensitive plastic substrates was studied. It was found that plasma results in decomposition of copper complex to form metallic copper without heating at high temperatures. Ink composition and plasma parameters (predrying conditions, plasma treatment duration, gas type, and flow rate) were optimized to obtain uniform conductive metallic films. The morphology and electrical characteristics of these films were evaluated. Exposing the printed copper metallo-organic decomposition (MOD) ink to 160 W plasma for 8 min yielded resistivity as low as 7.3 ± 0.2 µΩ cm, which corresponds to 23% bulk copper conductivity. These results demonstrate the applicability of MOD inks and plasma treatment to obtain highly conductive printed patterns on low-cost plastic substrates and 3D printed polymers.

Self-reduction of a copper complex MOD ink for inkjet printing conductive patterns on plastics.

Highly conductive copper patterns on low-cost flexible substrates are obtained by inkjet printing a metal complex based ink. Upon heating the ink, the soluble complex, which is composed of copper formate and 2-amino-2-methyl-1-propanol, decomposes under nitrogen at 140 °C and is converted to pure metallic copper. The decomposition process of the complex is investigated and a suggested mechanism is presented. The ink is stable in air for prolonged periods, with no sedimentation or oxidation problems, which are usually encountered in copper nanoparticle based inks.