Accurate To 50 Nm! Nano Scale Transfer Technology To Pave The Way For Wearable Textiles

With the development of flexible electronics and wearable electronic technology, smart clothing has been applied to many aspects. The usual methods of processing on smart clothing include mask spray, dip coating and inkjet printing. However, it is not easy to map and process micrometer or even nanometer level patterns on fabrics with spray and dip coating technology. Ink jet printing technology is relatively easy to process to micron scale patterning, but it can not be finished at nanometer scale. Therefore, how to develop a set of graphic methods for patterning and processing nano scale on fabric surface will be of great significance. Transfer printing methods have been reported for flexible electronics, sensors, energy harvesting devices and display devices. The usual transfer technology needs to be patterned on the donor substrate first and then transferred to the receiving substrate. However, the general transfer method usually has strict requirements for the morphology and coarse excess of the receiving substrate. Therefore, it is difficult for the transfer technology to map the nano scale structure onto the receiving substrate.

In order to solve the limitations mentioned above, Jun-Ho Jeong and Inkyu of the Korean Academy of science and technology The Park research team developed a simple transfer method: by simply depositing nanostructures on water-soluble donor substrates and then dissolving water-soluble donor substrates after transfer steps, we can simply transfer nano scale fine structure functional material nanostructures on textile material substrates. This work is entitled "Nanotransfer Printing on Textile Substrate with Water-Soluble Polymer Nanotemplat", which was published in the latest ACS Nano on January 28, 2020.

In this work, the Jun-Ho Jeong and Inkyu Park research team used hyaluronic acid with good biocompatibility and room temperature solubility as the donor substrate, while hyaluronic acid could replicate the nanostructures fabricated on silicon wafers with high accuracy. First, hyaluronic acid molds can be easily made into nanowires, nanodots and nanopores. Secondly, all kinds of metal or SiO 2 are deposited on patterned hyaluronic acid film. Finally, the film is laid on the wet textile substrate, hyaluronic acid is dissolved, and the functional material of the designed nanostructure is transferred to the surface of the textile material. With this technology, the micro / nano scale patterns of metal or non-metal can be transferred to the surface of any non planar fabric while maintaining its shape. The minimum accuracy of this method is 50 nm.

Figure 1: transfer of functional materials by the nano transfer printing process (nTP-SP) of water-soluble polymers: the mechanism and preparation process of (a) nTP-SP, (b) SEM images with a line of hyaluronic acid film, (c) SEM images of oblique deposition gold on hyaluronic acid film, (d) SEM image of raw fabric, (E) SEM image of transferring gold pattern when the hyaluronic acid is not completely dissolved, (E) SEM image: remove the hyaluronic acid from the fiber and transfer it to the Au pattern.

At present, the Pd nanowire array gas sensor has been successfully fabricated on textiles. Potential applications include hydrogen sensors with high selectivity and sensitivity. Moreover, this method is proved to be suitable for mass production of textiles because it is compatible with the fast and safe printing of complex nanostructures with photoelectric functions. This process can be used to prepare effective sensors for detecting H 2, effectively generate nano patterns with structural colors, and self cleaning. The function of transferring titanium dioxide nanostructures has been demonstrated. The proposed nanocrystallization method can provide a convenient way for the manufacture of various functions, including devices on textiles or paper substrates, including sweat sensors, environmental monitoring equipment, catalytic filters and textile based supercapacitors.

Figure two: application of nTP-SP process in the preparation of Pd nanostructures for hydrogen detection: (a) hydrogen sensing schematic, sensors using textile substrates; (b) nanostructured L/S for 200nm /200 SEM images, preparation of nanomaterials on fabric substrates; (c) response curves for H2 detection (delta R / R 0); (C) comparison of the response curves of nanoparticles and films transferred onto textile substrates; (E) the response of sensors to H2 under different relative humidity (070%); (f) selective testing of various gases (NO 2, H 2 S, CO).

The first author of this paper is Jiwoo Ko from KAIST, who is a professor of Jun-Ho Jeong and Professor Inkyu Park of KAIST. The study was funded by the Korea National Research Foundation (NRF) (MSIT; No. 2018R1A2B2004910) and the Ministry of science of Korea (CAMM-No.2014M3A6B3063707).

Source: Polymer Science Frontiers