Highly conductive and flexible fiber for textile electronics obtained by extremely low-temperature atomic layer deposition of Pt

Abstract

Thermal atomic layer deposition (ALD) of metal has generally been achieved at high temperatures of around 300 °C or at relatively low temperatures with highly reactive counter reactants, including plasma radicals and O3, which can induce severe damage to substrates. Here, the growth of metallic Pt layers by ALD at a low temperature of 80 °C is achieved by using [(1,2,5,6-η)-1,5-hexadiene]-dimethyl-platinum(II) (HDMP) and O2 as the Pt precursor and counter reactant, respectively. ALD results in the successful growth of continuous Pt layers at the low temperature without any reactive reactants owing to the low activation energy of the HDMP precursor for surface reactions. Because of the high reactivity of the precursor, the growth of a pure Pt layer is achieved on various thermally weak substrates, leading to the fabrication of high-performance conductive cotton fibers by ALD. A capacitive-type textile pressure sensor is successfully demonstrated by stacking elastomeric rubber-coated conductive cotton fibers perpendicularly and integrating them onto a fabric with a 7 × 8 array configuration to identify the features of the applied pressure, which can be effectively utilized as a new platform for future wearable and textile electronics. Normally fragile cotton fibres can be transformed into conductive fabric sensors using a low-temperature platinum deposition technology. The complex shapes and thermal instability of textiles make them hard to use as substrates for electronic devices. Now, Han-Bo-Ram Lee from Incheon National University in South Korea and co-workers have overcome this issue by developing an approach based on atomic-layer deposition. They exposed surfaces such as strands of hair and cotton threads sequentially to a precursor gas made from organoplatinum molecules, and to oxygen. The parachute-like structure of the precursor's molecules aided the continuous growth of nanometre-thin platinum films at temperatures as low as 80 degrees Celsius. By covering two platinum-coated fibres with an insulating polymer and then crossing them perpendicularly, the researchers produced a capacitive sensor capable of detecting small pressure variations for over 10,000 cycles. A highly conductive fibers and sensitive textile pressure sensors are developed by extremely low-temperature atomic layer deposition (ALD) of Pt. The low-temperature Pt ALD is achieved under 100 °C without any reactive reactant, enabling cotton fibers to have excellent electrical properties. The pressure sensors fabricated using the conductive fibers exhibit high performances, and can be applied to smart fabrics which can distinguish features of occupants.