The research plan within this project addresses three particular objectives:

O1. the first objective refers to the fabrication of flexible nanostructured electrodes;

O2. the second to the production of sensors for ionic solutes such as Na⁺ and Cl^-;

O3. the third objective is related to the fabrication of biosensors for electrochemical quantification of glucose, uric acid and urea.

The project is carried out by the group of Functional Nanostructures at National Institute of Materials Physics

2017

- flexible electrodes were fabricated on polyethylene terephthalate (PET) substrate with  metalized micro-sized electrospun polymeric fibres or with metalized fibrous proteic membranes (FPM) mechanically extracted from  egg shells;

Photographs of FPM electrodes coated with gold and carbon

- polyacrilamide and agarose hydrogel to be used as contacting layer between electrode surface and epiderm were obtained and characterized;

A) Cyclic voltammograms, B,C) electrochemical impedance spectra in B) NYQUIST and C) BODE representations, and
D) amperometric response recorded at -0.20V at successive injections of hydrogen peroxide, of gold-coated FPM electrodes

- flexible electrodes coated with gold, palladium, silver and carbon were characterized by scanning electron microscopy and by electrochemical methods such cyclic voltammetry and electrochemical impedance spectroscopy. Also, their response to hydrogen peroxide, a product of enzymatic reactions catalyzed by oxidase enzymes, was investigated.

2018

Flexible electrodes on polyethylene terephthalate (PET) substrate nanostructured with  metalized electrospun polymeric fibres were fabricated for quantification of electrolytes in sweat.

- polymeric membranes were used as immobilization matrix for ionophores in order to create pores specific to different electrolytes such as Ca²⁺, H⁺, NH₄⁺ si Cl^-;

- among the immobilization matrices, liposomes, supported bilayer lipidic membranes, polyacrylamide hydrogel and nafion were investigated;

- electrodes/sensors surfaces were characterized by cyclic voltammetry, electrochemical impedance spectroscopy, Fourier-transformed  infra-red spectroscopy and scanning electron microscopy;

SEM image, chemical composition map and typical response of a ionophore-based sensor
at successive additions of an electrolyte

- sensors response to successive additions of ions specific to each ionophore was  investigated by measuring the open circuit potential values.

2019

Flexible electrodes on polyethylene terephthalate (PET) substrate nanostructured with  metalized electrospun polymeric fibres were fabricated for quantification of electrolytes in sweat. Ca2+ ionophore V and Cl- ionophore II in nafion matrix were used and characterized. Immobilization in polyacrylamide gel is under investigation.

Paper-based microfluidic devices were developed.

Photographs of the paper-based microfluidic devices before and after attachment of the electrodes.
Cyclic voltammograms at the paper-based microfluidic device in the absence and the presence of H2O2.

The microfluidic device was used for investigating the redox processes of H2O2 as the oxidation product of glucose.

Glucose-oxidase was immobilized within cellulose matrix.

1. A. Aldea, E. Matei, A. Evanghelidis, I. Enculescu, V.C. Diculescu, Gold coated submicrometer electrospun polymeric fibres as new electrode platform for oxidase enzymes activity, Biosens. Bioelectron., submitted.
2. A. Aldea, E. Matei, R.J. Branco Leote, I. Enculescu, V.C. Diculescu, Ionophore-nafion modified gold-coated electrospun polymeric fibers as flexible sensors for determination of electrolytes in sweat, Sens. Actuat. B, submitted.
3. A. Serban, A. Evanghelidis, M. Onea, V.C. Diculescu, I. Enculescu, M.M Barsan, Electrospun conductive gold covered polycaprolactone fibers as electrochemical sensors for O₂ monitoring in cell culture media, Electrochem. Commun., submitted.
4. R.J. Branco Leote, N. Apostol, Elena Matei, I. Enculescu, V.C. Diculescu, Nanostructured samarium oxide electrodes for biosensing applications, Electrochim. Acta, in preparation.
5. D. Botta, A. Aldea, I. Enculescu, E. Matei, V. Diculescu, Enzyme-modified paper-based microfluidic device for glucose biosensing, Electrochem. Commun., in preparation.

The results were disseminated through scientific conferences :

1. Victor C. Diculescu, Mihaela Beregoi, Alexandru Evanghelidis, Ionut M. Enculescu, Fabrication of flexible nanostructured electrodes for Wearable sensors development, 8th International Workshop on Biosensors for Food Safety and Eenvironmental Monitoring, Rabat, Maroc, 12-14 October 2017.
2. Anca Aldea, Mihaela Beregoi, Alexandru Evanghelidis, Ileana Rau, Victor C. Diculescu, "New Flexible Materials for Wearable Biosensors", ESEAC 2018-17th International Conference of Electroanalysis, 3-7 June, Rodos, Greece
3. Anca Aldea, Victor C. Diculescu, Ionut Enculescu, Mihaela Beregoi, Alexandru Evanghelidis, Ileana Rau, "High Surface Flexible Electrodes for Biomedical Applications", ISE 2018-69th Annual Meeting of the International Society of Electrochemistry, 2-7 September 2018, Bologna, Italy
4. Victor C. Diculescu, Anca Aldea, Mihaela Beregoi, Alexandru Evanghelidis, Ionut Enculescu, "High Surface Area Flexible Electrodes for Wearable Devices and Actuators", The Fifth Edition of International Conference on Analytical and Nanoanalytical Methods for Biomedical and Environmental Sciences. IC-ANMBES 2018, 23-25 Mai 2018, Brasov, Romania.
5. Anca Aldea, Elena Matei, Victor C. Diculescu, “Flexible Ionophore-Based Sensors for Continuous Monitoring of Electrolytes”, XXV International Symposium on Bioelectrochemistry and Bioenergetics, 26-30 May, Limerick, Ireland.
6. Anca Aldea, Victor Diculescu, Alexandru Evanghelidis, Elena Matei, Ionut Enculescu, “Flexible Electrodes Based on Electrospun Metallized Fibers for Biomarkers Detection in Sweat”, ISE 2019 – 70^th Annual Meeting of the International Society of Electrochemistry, 4-9 August, Durban, South Africa.