Temporary tattoo as unconventional substrate for conformable and transferable electronics on skin and beyond

Abstract

In the growing field of conformable electronics, among the various approaches so far, tattoo technology has emerged. Here temporary tattoo paper is adopted as unconventional substrate to build up transferable body compliant devices, which establish a stable and long-lasting interface with the skin. Tattoo-based devices have shown their capabilities in multiple fields, with main application in human health biomonitoring. Such approach is advancing the state-of-the-art, overcoming some limits of existing technologies, as in the case of skin-contact electrodes and sweat analysis. Temporary tattoo has also been adopted in other fields as in organic electronics, within the development of organic solar cells and transferable edible transistors. Multiple and complementary fabrication approaches on temporary tattoos have been demonstrated, spanning from traditional vacuum-based deposition methods to various printing technologies. In this review, together with reporting and discussing the main fabrication methods and applications of tattoo technology, we describe the main features of the tattoo substrate. New insights on its material composition and properties are given, discussing the pros and cons in comparison with other approaches adopted in conformable electronics. Together with providing a comprehensive and up to date review of advancements in tattoo technology, this review aims to contribute to ain a better understanding of the capabilities offered by such low cost and versatile substrate. This can help in opening up new research for emerging applications, like in the relevant field of sustainable electronics.

Toward the Use of Temporary Tattoo Electrodes for Impedancemetric Respiration Monitoring and Other Electrophysiological Recordings on Skin

“…It is worth noting that strongly shaking the forearm without contracting the muscles resulted in a low background signal, comparable with the one produced at rest (see Figure 4 c and Supporting Video SV3 ), thus demonstrating that the system (thanks to the magneto-electric connections and smart data acquisition) is quite robust against motion artefacts, also in “real world” conditions. The EMG BT device could find application as muscle-controlled wireless interface in several interesting scenarios, including prosthetic control [ 12 ] or interface for entertainment and gaming. As an example, muscle activated remote control of toy car was also demonstrated (see Supporting Video SV4 ).…”

“…In particular, we used a commercial decal transfer paper as the substrate for TTEs’ fabrication, with improved mechanical performances compared to the one used elsewhere [ 14 ]. A detailed description of this and other decal transfer paper compositions is reported in [ 12 ] and in the Materials and Methods section (see also Supporting Information SI.1 ). The thickness of the supporting tattoo layer, which is released on the skin after the dissolution of the water-soluble sacrificial layer and the removal of the supporting paper, was measured to be ~1.7 µm.…”

“…These structures are subsequently laminated onto the epidermis, conformally adhering to it. Recently, commercially available temporary tattoo paper has attracted the attention of many researchers as a platform for device integration [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. Epidermal electronics fabricated on top of decal transfer paper enable an easy manipulation and reliable release/transfer on the skin (or other target surfaces), which are crucial from an end-user standpoint.…”

Ultrathin, Ultra‐Conformable, and Free‐Standing Tattooable Organic Light‐Emitting Diodes

“…[ 4,5,27,28 ] A more detailed description of the TT paper structure and of the main characteristics of the WR layer can be found in the review by Ferrari et al. [ 24 ]…”

“…This strategy has been adopted for various tattoo‐like devices. [ 24 ] All of these “Tattoo Electronics” (TE) applications make use of a commercial temporary “tattoo‐paper” substrate which enables an easy water‐assisted transfer directly onto skin and other surfaces, and provides stable and conformal adhesion to the target surfaces. Zucca et al.…”