Activities: Over the two-year duration, the project focused on the design, fabrication, and validation of flexible PHE sensors. Key activities included sputtering deposition of bi-layer (e.g. NiFe/IrMn) and tri-layer (e.g. NiFe/Cu/IrMn thin films on polyimide substrates, incorporating elliptical and meander geometries to enhance magnetic anisotropy and signal linearity. An ultralow-noise measurement setup was built from scratch, integrating lock-in amplification and frequency mixing for noise decomposition, achieving sub-nT resolution below 10 Hz in unshielded environments.
Main achievements encompassed the successful fabrication of prototypes that demonstrated over 95% signal retention after 10,000 bending cycles (radii down to 5 mm) and sensitivities up to 500 mV/T. Sensors were validated in forced-MMG experiments on human subjects, tracking skeletal muscle contractions (e.g. forearm) with high spatial resolution. Collaborations led to biodegradable variants using cellulose-based substrates and printable sensors via conductive inks, applied to magnetic particle tracking with <1 mm accuracy. Noise models based on Hooge's parameter were optimized to reduce 1/f noise using capping layers. The project resulted in five peer-reviewed publications, four conference presentations (such as INTERMAG 2024, JEMS 2025), and leadership in IEEE standardization (P3599 working group chair). Technology transfer discussions with industry partners (Foerster, Bosch) explored scalability for non-destructive testing (NDT).
Achievements:
The project combined thin-film device engineering, low-noise electronics, mechanical characterisation, and application-level validation:
a) Device engineering — Reproducible fabrication flows for flexible bi-layer and tri-layer PHE sensors on polymer substrates were established. Two complementary geometries (elliptical for high linearity and meander for enhanced sensitivity) were developed and optimised, with stack-level interventions (spacer/capping layers and exchange bias, where applicable) to stabilise magnetisation under flex.
b) Low-noise instrumentation — A customized ultralow-noise measurement platform and data pipeline were designed and constructed to quantify device transfer curves and noise spectra down to the sub-nT regime (notably below 10 Hz). Frequency-mixing and readout optimisation reduced effective 1/f contributions, enabling robust comparison between flexible prototypes and rigid references.
c)Mechanical and magnetic characterisation — Systematic bending and cyclic-flex tests were performed to map sensitivity, offset drift, and 1/f noise as functions of curvature and cycle number. The best prototypes showed improved sensitivity, enhanced linearity across the operational range, and mechanical resilience suitable for wearable applications.
d)Application validation — Flexible sensors were integrated into a pilot forced-MMG measurement chain and captured biomagnetic signatures above the laboratory noise floor; analysis and manuscript preparation are ongoing. Devices were also trialled in magnetic-particle tracking experiments, demonstrating multi-use applicability.
e)Dissemination & translation — The project led to multiple conference presentations, invited talks, and active industrial discussions to evaluate technology transfer. Standardisation momentum was initiated through leadership roles in planar-Hall sensor characterisation working groups (standard development ongoing).
Collectively, these activities delivered prototype sensors, a validated low-noise testbed, and initial application evidence in MMG and particle tracking.
