Context :

1. In biosensing for environment or health applications, microelectrode flexible sensors are
still very challenging depending on the application target. Several designs are commonly
used (either single electrodes or InterDigitated Electrodes), requiring different interface
solutions (resistive or capacitive impedance leading to potentiometric or amperometric
outputs). The challenges are the sensitivity and selectivity, stability and life time,
compatibility with heterogeneous and aggressive environment (in case of biological
tissues or polluted water/soils in agrifood). TiN which is bio-compatible, has shown
promising properties in case of well controlled surface porosity obtained with specific
etching [S. Paul Shylendra, et al, ―Titanium Nitride Thin Film Based Low-Redox-
Interference Potentiometric pH Sensing Electrodes,‖ Sensors, vol. 21,(1), 2020 ; M. Liu,
et al, ―A titanium nitride nanotube array for potentiometric sensing of pH,‖ The Analyst,
vol. 141, (5), 2016 N. Sun et al., Sputtered titanium nitride films with finely tailored
surface activity and porosity for high performance on-chip micro-supercapacitors, Journal
of Power Sources 489 (2021) 229406].

2. The thesis in proposed in continuity with a previous phD work (Thuy Nguyen,
defense in 2023) on flexible smart sensors dedicated to healthcare, and in relation with
expertise developed on TiN material within the ERC Neurodiam of L Rousseau. A first
proof of concept has been demonstrated on the interest of TiN material for pH sensor
electrodes [Porous Titanium Nitride Electrodes on Miniaturised pH Sensor for Foetal
Health Monitoring Application, T. Nguyen, B. Journet, H. Takhedmit, G. Lissorgues,
DTIP2022]. But deep material characterization is required to understand the
sensitivity/accuracy improvement in regard to the porosity control in case of porous TiN
versus flat TiN. And the bibliography on this material is showing an increasing
interest on several domains: optics, thermo-optics, electronics [. M. Reed, M. R.
Ferdinandus, N. Kinsey, C. DeVault, U. Guler, V. M. Shalaev, A. Boltasseva, and A. Urbas,
« Transient Nonlinear Refraction Measurements of Titanium Nitride Thin Films, » in
Conference on Lasers and Electro-Optics, OSA Technical Digest (online) (Optica
Publishing Group, 2016), paper FTu1A.6; A. Calzolari and A. Catellani, « Controlling the
TiN Electrode Work Function at the Atomistic Level: A First Principles Investigation, » in
IEEE Access, vol. 8, pp. 156308-156313, 2020, doi: 10.1109/ACCESS.2020.3017726.]. In
addition, we have the clean room facilities in ESYCOM allowing working on the
optimization process for porous TiN.

Thesis topic :

1. As explained in the context above, there is an increasing interest in the TiN material
which was initially only used for thin film coatings. The first target application is pH
measurement because the induced porosity of etched TiN, presenting a specific columnar
structure, will accelerate H+ ions migration and interaction with the surface at the
electrode/electrolyte interface and increase the sensitivity. Other applications can be
explored outside electrochemical sensors, in neurosciences for new microelectrode arrays
[Ryynänen, T., et al. « Ion beam assisted E-beam deposited TiN microelectrodes – applied
to neuronal cell culture medium evaluation.‖, Front. Neurosci. 12:882. 2018.], or
in energy storage though supercapacitor concepts [Grigoras, K., et al. ―Conformal
titanium nitride in a porous silicon matrix: a nanomaterial for in-chip supercapacitors.‖,
Nano Energy 26, 340–345, 2016]. If thermo-optic properties appear to be original (to be
checked in this thesis), it will also extend the interest of porous TiN towards
metamaterial applications.

2. The project will be to develop new TiN samples with controlled porosity and to
implement such a material on microelectrodes for sensing performance assessment.
The solution can be easily transferred on flexible substrates based on Esycom previous
experience on soft implants. An option will be to add the wireless transmission to
these sensors for remote monitoring, considering a resonant RFID like circuit [P.
Marsh et al., « Flexible Iridium Oxide Based pH Sensor Integrated With Inductively
Coupled Wireless Transmission System for Wearable Applications, » in IEEE Sensors
Journal, vol. 20, no. 10, pp. 5130-5138, 15 May15, 2020, doi:
10.1109/JSEN.2020.2970926; M. Smalley, K. Anderson and N. McFarlane, « Towards a
Wireless pH-Impedance Sensor System for IoT Applications, » 2022 IEEE 65th
International Midwest Symposium on Circuits and Systems (MWSCAS), Fukuoka, Japan,
2022, pp. 1-4, doi: 10.1109/MWSCAS54063.2022.9859313]. Several applications can
be chosen for the final demonstration: healthcare pH blood/sweat/urine monitoring; pH
acidity levels in food; pH monitoring in polluted soils or water… depending on the
existing collaborations.

3. Expected publications in IEEE Sensors or IEEE J. of Microelectromechanical Systems and
patent.

Expected planned work :

The work will be divided into several parts corresponding to the main issues :
– Material sample fabrication (optimization process for the porosity control) and full
characterization (electrical, optical, chemical composition, electrochemical, thermal…) –
mainly Year 1
– Material integration into a biosensing unit (based on existing know-how) – half of Year 2
– Implementation of the biosensor with a wireless transmission module – half of Year 2
– Sensor characterization to demonstrate its functionality and performances – Year 3
– Writing the manuscript & journal paper – half of Year 3

Curriculum :

The phD candidate should have a multidisciplinary background with special focus on :
Material sciences, applied physics, micro-technology and electronics.
A personal interest in biosensors will be appreciated.

Contact :

Supervision : Pr Gaëlle LISSORGUES
Email : gaelle.lissorgues@esiee.fr

Le laboratoire ESYCOM s’inscrit dans les domaines de l’ingénierie des systèmes de communication, des
capteurs et des microsystèmes pour la ville, l’environnement et la personne.
Les thèmes abordés sont plus spécifiquement :
– les antennes et propagation en milieux complexes, les composants photoniques – micro-ondes ;
– les microsystèmes pour l’analyse de l’environnement et la dépollution, pour la santé et l’interface avec le
vivant ;
– les micro-dispositifs de récupération d’énergie ambiante mécanique, thermique ou électromagnétique.