Design guidelines of laser reduced graphene oxide conformal thermistor for IoT applications

https://doi.org/10.1016/j.sna.2018.03.014Get rights and content

Highlights

  • A flexible laser-lithographed reduced-graphene thermistor is proposed in this paper.

  • An IoT sensing system to monitor the ambient temperature in real-time is presented.

  • The conditioning electronics is fully based on a reconfigurable platform.

Abstract

This work presents a complete temperature sensing solution based on a conformal laser-reduced graphene-oxide temperature transducer acting as thermistor. The process to implement the temperature-sensitive element is described in detail; from the raw material to the optimum laser scribing conditions used to define the resistive component. The final transducer is fabricated on a flexible plastic substrate and can be attached to any surface as a conformal patch. To provide a full demonstrator of the potential of this technology, the thermistor is integrated in an IoT sensing platform with wireless data transmission capability using a reconfigurable ultra-low power System-on-Chip.

Introduction

Since in 2010 the Nobel Prize was awarded to A. Geim and K. Noveselov “for the groundbreaking experiments regarding the two-dimensional material”, graphene has become one of the most studied materials in all the fields of technology [1]. Its unique properties combining outstanding electrical conductivity, transparency, toughness and biochemical functionalization capabilities have exponentially attracted the interest of not only fundamental research fields, such as Physics or Chemistry, but also more applied lines, like energy storage or transducers [2]. However, despite graphene’s potential is undeniable, the actual end-user applications are still far from achieving the aroused expectations, mostly due to the difficulties associated with the mass production of high quality graphene sheets capable of matching its theoretical properties.

The broad spectrum of production approaches has opened the term graphene to a set of materials including not only the ideal sp2 honey-comb and monoatomic carbon structure, but also multilayer polycrystalline graphene aggregates. One of these graphene-like materials is the so called reduced-graphene-oxide (rGO) [3]. Notwithstanding that rGO does not feature the superlative properties of monolayer crystalline graphene, it capitalizes part of its unique features (e.g. flexibility, electrical and thermal conductivity), with the great advantage of a much easier and technologically simpler synthesis process. In addition, rGO’s conductivity presents a very linear dependence with temperature above 200 K as a consequence of its polycrystalline structure [4]. This latter physical characteristic is exploited in this work to develop a temperature transducer (thermistor), taking advantage of the pliancy and low thermal inertia of the rGO [5] and incorporating an application oriented photo-thermal reduction technique [6]. Some of these properties, such as its ductility, make this kind of sensors a pertinent choice for Internet of Things (IoT) applications or even healthcare implantable systems. In this way, the use of graphene or graphene-like based sensors and devices aims to facilitate the interconnectivity that the future Internet of Everything (IoE) environment will need, such as flexible and pervasive devices that shrink the power consumption and enable faster data transmission [7]. In this context, this work presents as a final outcome, a full custom wearable temperature measurement system that illustrates the advantages that this technology brings up to the IoT ecosystem.

The manuscript is divided in five parts. After this introduction, Section 2 introduces the production of rGO from the raw GO colloid. Section 3 provides guidelines for the design of the transducers based on the laser assisted photothermal lithography, and results from their electrothermal characterization. Section 4 describes a complete sensor application adopting the rGO transducer in an ultra-low power platform based on Cypress® 5LP System-on-Chip (SoC). Finally, the main conclusions are drawn in Section 5.

Section snippets

Laser scribing of reduced-graphene oxide

The starting point for the proposed rGO-based thermistors is the production of the raw material: the Graphene Oxide colloid (GOc). The GOc is synthesized by oxidation and sonic exfoliation of graphite powder. In our samples, we follow a modified version of Hummers and Offerman method [8], schematized in Fig. 1. For about two hours Graphite is oxidized, in an ice bath, using strong oxidizing reagents like concentrated sulfuric acid (H2SO4); sodium nitrate (NaNO3); and potassium permanganate (KMnO

Design of rGO thermal transducers

The conductivity of single GO/rGO flakes has been already studied in detail [14]; however, the number of works which exploit the conduction mechanism in large deposited polycrystalline films of rGO is more reduced. In this regard, we have focused our attention on studying the behavior of the conductivity with respect to temperature, rather than analyzing the ultimate physical mechanisms responsible for its conduction. The design of the transducer is dimension-based being its total resistance (R

Ultra-low power sensor application

The use of any temperature sensor prototype is intimately related to the design of the conditioning interface that provides its information to the final user. Furthermore, in the IoT era [20], the electronic instrumentation designed for an emerging sensor prototype must underline the advantages of this technology and envision the myriads of environments where this device could be employed, especially enhancing the sensor-instrumentation symbiosis inside the IoT context. The main characteristics

Conclusions

Graphene Oxide has been suited as a sensing platform ready to be exported to certain end-user applications. We have presented a prototype of temperature monitoring solution, covering aspects from the production of the raw material to the design and integration on a SoC. Once the GO is deposited on the supporting substrate, a simple process is followed to create the transducer: a CNC-laser scribes the desired pattern, yielding a conductivity that can be easily predicted and controlled by the

Acknowledgements

This work has been partially supported by the Spanish Ministry of Education, Culture and Sport (MECD), the European Union and the University of Granada through the project TEC2017-89955-P, the pre-doctoral grant FPU16/01451, the fellowship H2020-MSCA-IF-2017 794885-SELFSENS and the grant “Initiation to Research”.

The authors would like to thank Prof. Alberto J. Palma for the climate chamber support.

Francisco J. Romero received the B.Eng. with valedictorian mention in Telecommunications Engineering from the University of Granada (Spain) in 2016. In 2015, he joined the Department of Electronics and Computer Technology at the University of Granada as a Junior Researcher, and in 2017 became a PhD Candidate with a national predoctoral scholarship. His current research interests are related to IoT embedded systems and 2D-materials-based sensors.

References (29)

  • E. Alahi et al.

    A temperature-compensated graphene sensor for nitrate monitoring in real-time application

    Sens. Actuators A

    (2018)
  • W.S. Hummers Jr et al.

    Preparation of graphitic oxide

    J. Am. Chem. Soc.

    (1958)
  • D.R. Dreyer et al.

    The chemistry of graphene oxide

    Chem. Soc. Rev.

    (2010)
  • F. Tuinstra et al.

    Raman spectrum of graphite

    J. Chem. Phys.

    (1970)
  • Cited by (34)

    • High-performance flexible electrothermal Joule heaters from laser reduced F-N Co-doped graphene oxide with extended Sp<sup>2</sup> networks

      2022, FlatChem
      Citation Excerpt :

      There has been a growing interest in the application of flexible electrothermal materials for smart clothing and other wearable electronics [2-5]. Flexible heaters have also been applied in sensors [6], thermistors [7], thermotherapy patches [8], and automobile defoggers [9]. For efficient energy transduction and overall good performance, electrothermal heaters require high electrical conductivity for large heat generations, as well as good thermal conductivity to facilitate heat propagation.

    • Multiple dispensing and photo-thermal reduction of graphene oxide solution for line patterning

      2022, Chemical Physics Letters
      Citation Excerpt :

      Recently graphene and graphene-based materials have been studied for its high electrical conductivity and transparency [1–4]. Reduced graphene oxide (rGO) has high conductivity and low production cost, so it is highly likely to be applied to commercial products [5–10]. In particular, graphene oxide (GO) with fine line electrodes have been used in many applications such as micro sensors and supercapacitors [11–14].

    • Facile fabrication of a fast-response flexible temperature sensor via laser reduced graphene oxide for contactless human-machine interface

      2022, Carbon
      Citation Excerpt :

      The aqueous GO solution used in the study contained a single-layer of GO powder (Nanjing XFNANO Materials Tech Co., Ltd., China) dispersed uniformly in deionized water. We prepared six different concentrations from 1 mg/mL to 6 mg/mL with a step of 1 mg/mL on the basis of the GO concentration range used in previous studies [14,22,24,25]. Silver paste (SPI Supplies® 05002-AB, China) was utilized to connect the copper wire and gold electrodes of the sensor.

    • Recent progress in the synthesis of graphene and derived materials for next generation electrodes of high performance lithium ion batteries

      2019, Progress in Energy and Combustion Science
      Citation Excerpt :

      Recently, several groups have demonstrated that GO can be reduced by photo-irradiation using several types of lasers. The process was mentioned in the literature as “photo-thermal reduction using laser”, “selective reduction by direct laser writing”, and “laser conversion” of GO/graphite oxide to rGO [396–404]. One of the main advantages of reduction by laser is that the photo-irradiation process does not need any chemicals or high temperature.

    View all citing articles on Scopus

    Francisco J. Romero received the B.Eng. with valedictorian mention in Telecommunications Engineering from the University of Granada (Spain) in 2016. In 2015, he joined the Department of Electronics and Computer Technology at the University of Granada as a Junior Researcher, and in 2017 became a PhD Candidate with a national predoctoral scholarship. His current research interests are related to IoT embedded systems and 2D-materials-based sensors.

    Almudena Rivadeneyra completed her master’s degrees in telecommunication engineering (2009), environmental sciences (2009) and electronics engineering (2012), at the University of Granada (Spain). In 2014, she received her PhD in design and development of environmental sensors at the same Institution. Since 2015, she belongs to the Institute for Nanoelectronics (Technical University of Munich) where her work is centered in printed and flexible electronics. She is co-author of more than 40 scientific contributions.

    Victor Toral received the B.Eng. in Electronics Engineering from the University of Granada (Spain) in 2017. In 2016, he joined the Department of Electronics and Computer Technology of the University of Granada as a Junior Researcher. He is pursuing a master’s degree in power electronics at the University Polytechnic of Madrid (Spain). His main research interests are related to power electronics and electronic instrumentation.

    Encarnación Castillo received the degree in Electronic Engineering and PhD “Summa cum Laude” from the University of Granada (Spain) in 2002 and 2008, respectively. From 2003 to 2005 she has been PhD student and from 2006 she is an Assistant Professor, both at the Department of Electronics and Computer Technology at the University of Granada. As part of the thesis research, she made two short stays during at the FAMU-FSU, College of Engineering in Tallahassee. Her research interests include the protection of IP Core Protection as well as RNS arithmetic, high-performance digital signal processing and VLSI and FPL signal processing systems.

    Francisco García-Ruiz received his Telecommunication engineering degree from the University of Málaga in 2002 and his PhD in electromagnetism from the University of Granada in 2005. He has been a visiting researcher at IRCTR - TU Delft, IMEC, UCL (Louvain-la-Neuve) and the Group of Graphene-based Nanotechnology - University of Siegen. He is currently with the Pervasive Electronics Advanced Research Laboratory (PEARL), Department of Electronics, University of Granada. His main research interests are simulation, modeling and characterization of electron devices, in particular 2D-materials-based devices and sensors.

    Diego P. Morales received the M.Sc. degree in Electronics Engineering and the PhD degree in Electronic Engineering from the University of Granada (Granada, Spain) in 2001 and 2011, respectively. He was an Associate Professor at the Department of Computer Architecture and Electronics, University of Almería (Almería, Spain) before joining the Department of Electronics and Computer Technology at the University of Granada, where he currently serves as an Associate Professor. His current research is devoted to developing reconfigurable applications.

    Noel Rodriguez received the B.Eng. with a first national award and M.Eng. in Electronics Engineering from the University of Granada, Spain, in 2004 and 2006 respectively. In 2008, he received a double Ph.D. from the University of Granada and the Institute National Polytechnique of Grenoble. During his Ph.D., he was awarded a grant inside the EDITH Marie Curie program allowing him to spend one year at the IMEP-Minatec facilities (France) where he worked on electrical characterization techniques. He is currently Tenured Professor at the University of Granada and co-founder of the Pervasive Electronics Advanced Research Laboratory. His research interest includes the development of new technologies for ubiquitous electronics and the simulation, modeling and characterization of memory devices with the emphasis in memristive systems and neuromorphic applications. Dr. Noel Rodriguez is co-holder of 9 patents related to the A-RAM memory technology, and he is author or co-author of 8 book chapters and more than 100 scientific contributions.

    View full text