Flexible skin sweat electrochemical sensing utilising laser induced graphene

  • Robert Barber

Student thesis: Doctoral Thesis


Rapid electrochemical detection methods promise the translation of traditionally lab–based analytical technologies into clinical and industrial applications, thereby facilitating the detection of a multitude of biomarkers at a fraction of the cost. This is expected to have a particular impact in the development of novel point of care (POC) and wearable biosensors. Disposable screen-printed electrodes are usually employed as the sensing platform but the conventional electrode materials (e.g., noble metals and graphitic inks) impose a restriction on the sensitivity due to their limited conductivity and porosity. In contrast, Laser Induced Graphene (LIG) electrodes are simply fabricated on flexible substrates with complex geometry and have been shown to achieve superior electrochemical performance. This thesis demonstrates the development of several electrode functionalisation protocols, which were successful in imparting outstanding sensitivity and selectivity towards a range of biomarkers, even when challenged in chemically complex matrices.

Initially, this focused on the endowment of pH sensitive redox moieties to LIG, enabling solid-state measurement of solution pH by square wave voltammetry. Preliminary studies revealed a near Nernstian response to pH was achieved by LIG electrodes modified by simple anodisation and again with an adsorbed riboflavin coating. A more robust approach was demonstrated by the immobilisation of an amino-naphthoquinone species, electrogenerated from an inactive nitro-aphthoquinone precursor. The thiol selectivity of this novel quinone species was further exploited to enable the highly selective detection of cysteine at a negative potential, achieving a limit of detection (LOD) of 13.11 μM. Thiol modified naphthoquinone was further shown to have a unique voltammetric profile, thereby tuning the response of the coating. LIG modified in this manner enabled interference-free measurement of pH in human sweat.

Hydrogen peroxide (H2O2) was targeted as a ubiquitous biomarker by the addition of a composite Prussian blue and chitosan coating to a LIG working electrode. Further, an integrated LIG electrode enabled the amperometric detection of hydrogen peroxide, at near 0 V and showed a LOD of 6.31 μM. The small working volume required by the integrated electrode allowed the recovery of H2O2 from human sweat and was also applied to the measurement of H2O2 produced by a culture of Lactobacillus johnsonii, despite both presenting a complex milieu of interferents.

Ultimately, the sensing systems presented here have real potential to bridge the gap between concept electrochemical sensors and devices that are suitable for industrial manufacture. These low-cost electrodes, sensitive to a range of biomarkers could aid in the decentralisation of clinical testing and allow the implementation of biosensors into new domains.
Date of AwardMay 2023
Original languageEnglish
SponsorsAbbott Diabetes Care
SupervisorPagona Papakonstantinou (Supervisor) & James Davis (Supervisor)


  • Flexible sensors
  • Electrodeposition
  • Quinone
  • Thiol

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