Our contribution to the book:

Chapter 15 – Ultraconformable Organic Electronics

L. M. Ferrari, S. Taccola, J. Barsotti, V. Mattoli,  F. Greco
in Organic Flexible Electronics, Eds. P. Cosseddu, M. Caironi, Elsevier 2021, pages 437-478
Publication Date: October 5, 2020
Link to the Chapter on Science Direct – Elsevier

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

Laura M. Ferrari, Kirill Keller, Bernhard Burtscher, Francesco Greco*
Multifunctional Materials, 2020, 3 3.
Published online on July 16, 2020
DOI: 10.1088/2399-7532/aba6e3

Alexander Dallinger, Kirill Keller, Harald Fitzek, Francesco Greco
ACS Appl. Mater. Interfaces, 19855-19865
Publication Date: April 6, 2020
https://doi.org/10.1021/acsami.0c03148

Abstract

The conversion of various polymer substrates into laser-induced graphene (LIG) with a CO₂ laser in ambient condition is recently emerging as a simple method for obtaining patterned porous graphene conductors, with a myriad of applications in sensing, actuation, and energy. In this paper, a method is presented for embedding porous LIG (LIG-P) or LIG fibers (LIG-F) into a thin (about 50 μm) and soft medical grade polyurethane (MPU) providing excellent conformal adhesion on skin, stretchability, and maximum breathability to boost the development of various unperceivable monitoring systems on skin. The effect of varying laser fluence and geometry of the laser scribing on the LIG micro–nanostructure morphology and on the electrical and electromechanical properties of LIG/MPU composites is investigated. A peculiar and distinct behavior is observed for either LIG-P or LIG-F. Excellent stretchability without permanent impairment of conductive properties is revealed up to 100% strain and retained after hundreds of cycles of stretching tests. A distinct piezoresistive behavior, with an average gauge factor of 40, opens the way to various potential strain/pressure sensing applications. A novel method based on laser scribing is then introduced for providing vertical interconnect access (VIA) into LIG/MPU conformable epidermal sensors. Such VIA enables stable connections to an external measurement device, as this represents a typical weakness of many epidermal devices so far. Three examples of minimally invasive LIG/MPU epidermal sensing proof of concepts are presented: as electrodes for electromyographic recording on limb and as piezoresistive sensors for touch and respiration detection on skin. Long-term wearability and functioning up to several days and under repeated stretching tests is demonstrated.

Kirill Keller, the PhD student from LAMPSe, was awarded with the grant with a project “Functionalization of Laser-induced graphene by Atomic layer deposition for lithium-ion batteries“.

Since renewable energy sources are actively developed today, it is necessary to find a way to store this energy. The supercapacitors and lithium-ion batteries are common in modern research work and provide big perspectives for application.

Lithium-ion batteries  are of a great interest due to their high energy density and low self-discharge rate. Constantly increasing demands for high capacity, safe and reliable batteries stimulate the search and development of alternative materials for lithium-ion batteries, which is a big challenge in modern materials science.

Our group at the Institute of Solid State Physics has recently started the research of pyrolysis of commercial polymers. This technique is used for producing Laser-induced graphene (LIG), the material possessing unique physical properties.

The goal of the project is investigation of ALD processes on a complex surface of LIG that could open new applications including solid state lithium-ion batteries which could be used for powering of miniaturized, autonomous,  wearable devices and sensors.

During the stay from January 28^th to February 6^th at St. Petersburg, Kirill worked with a group of Maxim Maximov at Institute of Mechanical Engineering, Materials and Transport. There several syntheses of thin layers of transition metal oxides  on LIG were performed by atomic layer deposition The first results showed that modification of a graphene material is possible by ALD and it looks as a promising material for lithium-ion batteries electrodes with extended charging capacity.