Biocompatible nanotransfer printing using water soluble nanotemplate towards wearable application

Abstract

Wearable devices are used for observing vital signs, drug delivery, and disease treatment, and these devices are commonly manufactured through micro/nanopatterning. This patterning process enables performance improvement, miniaturization, and mechanical flexibility. However, the conventional patterning process is limited to the condition that the surface of the substrate must be smooth, and it is not suitable for the manufacture of wearable devices that require a biocompatible process in that toxic chemicals are used during the patterning process. To overcome these limitations, a nanotransfer process using hyaluronic acid, which is a biocompatible water-soluble polymer is proposed. The proposed process exploits the hyaluronic acid nanotemplate dissolving so that the pattern on the template can be transferred to the substrate, effectively transferring the pattern to well-wet textiles and lenses containing moisture surfaces. First, two methods of fabricating hyaluronic acid nanotemplates are proposed, one is obtained by pouring a hyaluronic acid solution into a replicated film and drying it, and the other is a method of transferring using a water bridge that is generated when hyaluronic acid meets water. Depending on the purpose of use, smart textile and smart lens are fabricated by transferring a pattern to the textile and lens using an appropriate method among the two methods to give a function. First, smart textile is fabricated by transferring various materials and nanostructures from a minimum line width of 50 nm to microscale patterns. Smart textile has been validated in three applications. A hydrogen sensor fabricated by transferring the palladium nanoline has improved performance by about 2.5 times compared to the sample transferred thin film. It was applied to the security pattern using the electrical/optical properties of the nanostructure, and finally, the self-cleaning function was verified by decomposing about 40% of methylene blue due to the photocatalytic effect of Ag/TiO2. In addition, the applicability as a wearable device was verified through a mechanical performance test. Next, a smart lens utilizing the optical properties of nanopatterns was fabricated and applied to two optical applications. First, it was applied to a stereoscopic lens through binocular parallax via the polarization of aluminum nanolines, and a depth map was introduced and verified. The other application is a specific wavelength blocking filter, and the two cases of vision impairments were targeted according to the wavelength width to be blocked. A lens that blocks light in a specific wavelength band was manufactured using an array of Ag nanodots for Irlen syndrome, a type of dyslexia caused by hypersensitivity to the light of a specific wavelength. The blocking performance was visually verified using LEDs. In addition, a smart lens for color vision deficiency was fabricated based on a high refractive index notch filter using TiO2 to effectively and narrowly block the causative wavelength to create a boundary between the two colors, thereby helping color weakness patients to distinguish colors.