By Josh Perry, Editor
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Scientists at Imperial College London (U.K.) developed a new technique for printing metals, including silver, gold, and platinum, onto natural fabrics, which could be used to add batteries, wireless receivers, or sensors onto materials such as cotton or paper.

Gold deposited onto paper using the new method. (Imperial College London)

The breakthrough, according to a report from the college, is that the process allows the metal inks to cover the entire fiber rather than just coating the fabric.

“To coat the fibers, the researchers first covered them in microscopic particles of silicon, and then submerged the material into a solution containing metal ions,” the report said. “This preparatory process, known as SIAM (Si ink-enabled autocatalytic metallization), allows metals to ‘grow’ throughout the material as the ions are deposited on the silicon particles.”

By spreading the metal coating throughout the material, the fabric or paper maintains its flexibility and its ability to absorb water but increases the metallic surface area. The initial experiments were done by hand, but researchers believe that it can be adapted for large-scale printers.

“They created silver coil antennas on paper, which can be used for data and power transmission in wireless devices such as Oyster cards and contactless payment systems,” the article continued. “The team also used the method to deposit silver onto paper and then added zinc onto the same paper to form a battery.”

Researchers developed several sensors on paper and other natural fabrics, and they are excited by the cost-effective solution for building sensors for complex processes. For instance, a coil antenna cost as little as $0.001 to manufacture (compared to $0.05 with previous methods), according to the article.

The research was recently published in Advanced Materials. The abstract stated:

“Commercially available metal inks are mainly designed for planar substrates (for example, polyethylene terephthalate foils or ceramics), and they contain hydrophobic polymer binders that fill the pores in fabrics when printed, thus resulting in hydrophobic electrodes.

“Here, a low?cost binder?free method for the metallization of woven and nonwoven fabrics is presented that preserves the 3D structure and hydrophilicity of the substrate. Metals such as Au, Ag, and Pt are grown autocatalytically, using metal salts, inside the fibrous network of fabrics at room temperature in a two?step process, with a water?based silicon particle ink acting as precursor.

“Using this method, (patterned) metallized fabrics are being enabled to be produced with low electrical resistance (less than 3.5 Ω sq⁻¹). In addition to fabrics, the method is also compatible with other 3D hydrophilic substrates such as nitrocellulose membranes.

“The versatility of this method is demonstrated by producing coil antennas for wireless energy harvesting, Ag–Zn batteries for energy storage, electrochemical biosensors for the detection of DNA/proteins, and as a substrate for optical sensing by surface enhanced Raman spectroscopy.

“In the future, this method of metallization may pave the way for new classes of high?performance devices using low?cost fabrics.”

See the new method in action in the video below: