Author: Alexander Dallinger

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News Publications

Different Roles of Surface Chemistry and Roughness of Laser-Induced Graphene: Implications for Tunable Wettability

“Different Roles of Surface Chemistry and Roughness of Laser-Induced Graphene: Implications for Tunable Wettability”

Dallinger, Alexander, Felix Steinwender, Matthias Gritzner, and Francesco Greco
Publication Date: July 10, 2023
https://doi.org/10.1021/acsanm.3c02066

Abstract

The control of surface wettability is a technological key aspect and usually poses considerable challenges connected to high cost, nanostructure, and durability, especially when aiming at surface patterning with high and extreme wettability contrast. This work shows a simple and scalable approach by using laser-induced graphene (LIG) and a locally inert atmosphere to continuously tune the wettability of a polyimide/LIG surface from hydrophilic to superhydrophobic (Φ ∼ 160°). This is related to the reduced amount of oxygen on the LIG surface, influenced by the local atmosphere. Furthermore, the influence of the roughness pattern of LIG on the wettability is investigated. Both approaches are combined, and the influence of surface chemistry and roughness is discussed. Measurements of the roll-off angle show that LIG scribed in an inert atmosphere with a low roughness has the highest droplet mobility with a roll-off angle of ΦRO = (1.7 ± 0.3)°. The superhydrophobic properties of the samples were maintained for over a year and showed no degradation after multiple uses. Applications of surfaces with extreme wettability contrast in millifluidics and fog basking are demonstrated. Overall, the proposed processing allows for the continuous tuning and patterning of the surface properties of LIG in a very accessible fashion useful for “lab-on-chip” applications.

 

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News Publications

Sweat analysis with a wearable sensing platform based on laser-induced graphene

“Sweat analysis with a wearable sensing platform based on laser-induced graphene”

Vivaldi, F., A. Dallinger, N. Poma, A. Bonini, D. Biagini, P. Salvo, F. Borghi, A. Tavanti, F. Greco, and F. Di Francesco
Publication Date: 19 September 2022
https://doi.org/10.1063/5.0093301

Abstract

The scientific community has shown increasing interest in laser scribing for the direct fabrication of conductive graphene-based tracks on different substrates. This can enable novel routes for the noninvasive analysis of biofluids (such as sweat or other noninvasive matrices), whose results can provide the rapid evaluation of a person’s health status. Here, we present a wearable sensing platform based on laser induced graphene (LIG) porous electrodes scribed on a flexible polyimide sheet, which samples sweat through a paper sampler. The device is fully laser manufactured and features a two layer design with LIG-based vertical interconnect accesses. A detailed characterization of the LIG electrodes including pore size, surface groups, surface area in comparison to electroactive surface area, and the reduction behavior of different LIG types was performed. The bare LIG electrodes can detect the electrochemical oxidation of both uric acid and tyrosine. Further modification of the surface of the LIG working electrode with an indoaniline derivative [4-((4-aminophenyl)imino)-2,6-dimethoxycyclohexa-2,5-dien-1-one] enables the voltammetric measurement of pH with an almost ideal sensitivity and without interference from other analytes. Finally, electrochemical impedance spectroscopy was used to measure the concentrations of ions through the analysis of the sweat impedance. The device was successfully tested in a real case scenario, worn on the skin during a sports session. In vitro tests proved the non-cytotoxic effect of the device on the A549 cell line.

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News Publications

Published chapter in Nanoporous Carbons for Soft and Flexible Energy Devices

LAMPSe was invited to contribute a chapter to the book “Nanoporous Carbons for Soft and Flexible Energy Devices“.

The chapter with the name “Laser-Induced Graphene and Its Applications in Soft (Bio)Sensors” features an overview from formation of LIG, properties to the application in soft (bio)sensors.

Abstract

In recent years the technological importance of graphene increased significantly also in the field of soft, flexible and wearable electronics. In this chapter a simple one step process to create 3D porous graphene structures into flexible polymer films is highlighted. By laser scribing polymer precursor substrates with commercially available laser scribing setups the polymer is converted into so-called Laser-Induced Graphene (LIG) via a photothermal conversion. The properties of this material and the influence of different processing parameters on its composition and structure are introduced. Different transfer methods for stretchable applications are discussed. Three main application fields of LIG for soft (bio)sensors are identified: piezoresistive, electrophysiological and electrochemical sensors. Each of the application fields is highlighted more in detail and an overview of recent publications is given. Concluding with an outlook on the future of LIG – including improvement of patterning resolution and the use of renewable, bio-derived precursors – this chapter provides a broad overview of LIG for soft and flexible sensor devices.

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News

Smart tattoos are keeping tabs on our health – chemistryworld.com

Francesco Greco, Head of LAMPSe, recently was interviewed by Nina Notman for a feature article on smart tattoos for the UK Royal Society of Chemistry’s Chemistry World magazine www.chemistryworld.com.

The article features the newest developments on smart tattoos, discussing blood-analysing patches, sweat sensors, color changing – UV detecting tattoos and electrophysiological sensing tattoos, like the ones developed at LAMPSe.

picture of a tattoo electrode

Here the link to the article available on chemistryworld.com:

Smart tattoos are keeping tabs on our health chemistryworld.com
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Conferences & Posters News Publications

Paper on Multiresponse Soft Acutators published in ACS Applied Polymers

“Multiresponsive Soft Actuators based on Thermoresponsive Hydrogel and embedded Laser-Induced Graphene”

Alexander Dallinger, Paul Kindlhofer, Francesco Greco and Anna Maria Coclite
Publication Date: March 9, 2021
https://doi.org/10.1021/acsapm.0c01385

Short presentation of the multiresponsive actuators

Abstract

The method of converting insulating polymers into conducting 3D porous graphene structures, so called laser-induced graphene (LIG) with a commercially available CO2 laser engraving system in an ambient atmosphere, resulted in several applications in sensing, actuation and energy. In this paper we demonstrate a combination of LIG and a smart hydrogel (poly(N-vinylcaprolactam) – pNVCL) for multiresponsive actuation in a humid environment. Initiated chemical vapor deposition (iCVD) was used to deposit a thin layer of smart hydrogel onto a matrix of PDMS and embedded LIG tracks. An intriguing property of smart hydrogels, such as pNVCL, is that the change of an external stimulus (temperature, pH, magnetic/electric fields) induces a reversible phase transition from a swollen to a collapsed state. While the active smart hydrogel layer had a thickness of only 300 nm (compared to the 500 times thicker actuator matrix), it was possible to induce a reversible bending of over 30° in the humid environment triggered by joule heating. The properties of each material were investigated by means of scanning electron microscope (SEM), Raman spectroscopy, tensile testing and ellipsometry. The actuation performances of single-responsive versions were investigated by creating a thermoresponsive PDMS/LIG actuator and a humidityresponsive PDMS/pNVCL actuator. These results were used to tune the properties of the multiresponsive PDMS/LIG/pNVCL actuator. Furthermore, the capabilities of self-sensing were investigated. By getting a feedback from the piezoresistive change of the PMDS/LIG composite the bending angle could be tracked by measuring the change in resistance. To highlight the possibilities of the processing techniques and the combination of materials, a demonstrator in the shape of an octopus with four independently controllable arms was produced.

Video showing the octopus demonstrator in action by rectracting two feet through joule heating in a humid environment.

Presentation @ DocDay 2021

Poster on Multiresponsive Actuators
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News

LAMPSe and Tattoo Electrodes on Ö1 Radio – DIGITAL.LEBEN

In Summer LAMPSe was interviewed by Ö1, one of Austria’s public radio stations. The interview was broadcasted on October 21st and can now be accessed online. Listen to Alexander Dallinger and Francesco Greco talking about the innovative tattoo electrodes.

picture of a tattoo electrode

Here the link to the interview available on Ö1 – DIGITAL.LEBEN:

Ö1 – digital.leben:
Elektroden-Tattoo misst Körpersignale

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Conferences & Posters News

Advanced Materials Day 2020

At the Advanced Materials Day 2020 hold at TU Graz, LAMPSe presented a poster on its research.

The Field-of-Expertise Advanced Materials Science is an interdisciplinary network of researchers at the TU Graz in chemistry, physics, architecture, mechanical engineering, civil engineering, electrical engineering and geodesy who discover, characterize and model materials, functional coatings and components.

You can listen to a short presentation of the poster in this video recorded for the virtual AMD2020.

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News

5D Nanoprinting Kick-Off

LAMPSe is proud to announce that it is part of the exciting EU project “5D Nanoprinting“.

The 5D NanoPrinting project aims to set a new paradigm in the 3D printing technology of micro and nano machines.  

By developing innovative smart/functional materials with tailorable properties and novel fabrication methodologies, it aims to propel forward the current state-of-the-art micro(nano)printing technologies, allowing faster prototyping and designing of micro-electromechanical systems (MEMS).

The part of LAMPSe is the investigation of methods to create conformal conductive paths complementing the two-photon polymerization process.
Our approach is conversion of polymers to conductive carbon via laser carbonization. By investigating different laser sources and precursor materials we aim to find a method which is easy to implement in the project.

Another partner in the consortium of TU Graz is the group of Anna Maria Coclite, who will be investigating Stimuli Responsive Materials for Sensing.

On September 21st the Kick-Off meeting for the project took place. Due to the current COVID-19 situation the consortium was meeting online.