Advancing Microneedle Sensors
From Measurement Scope to Fabrication Architecture
Time: Thu 2026-12-10 10.00
Location: Kollegiesalen, Brinellvägen 8, Stockholm
Language: English
Subject area: Chemistry
Doctoral student: Qikun Wei , Tillämpad fysikalisk kemi
Opponent: Professor Agustín González Crevillén, Universidad Nacional de Educación a Distancia, Spanien
Supervisor: Universitetslektor Maria Cuartero, Tillämpad fysikalisk kemi; Professor Gaston A. Crespo, Tillämpad fysikalisk kemi; Professor Christofer Lendel, Tillämpad fysikalisk kemi
QC 20261105
Abstract
Continuous monitoring of biomarkers in dermal interstitial fluid (ISF) could bring clinically relevant information out of the laboratory and into daily life. Microneedles (MNs) offer a minimally invasive route to ISF. However, most MN sensors target a narrow set of chemical analytes, and their accuracy and reproducibility remain limited. This thesis examines three aspects of MN sensing that go beyond the sensing chemistry: the range of parameters that can be measured, the physical conditions at the sensing site, and the way the sensor is fabricated.
The work begins by extending MN electrochemical sensing to dissolved oxygen. A sensor based on platinum nanoparticles on stainless-steel MNs measured ISF oxygen in live rats. This study also revealed two limitations that shaped the rest of the thesis. The sensor response depended on temperature, and manual modification of microneedles caused device-to-device variation.
Each limitation was then addressed. A conducting polymer-based temperature sensor was built using 3D-printed hollow MN (HMN) to measure temperature directly at the sensing site. In parallel, a modular fabrication strategy was developed. It separates skin insertion from sensing: a printed HMN shell provides the mechanical skin penetration function, and a printed conductive pillar carries the sensing membrane. This design moves functionalization away from the fragile microneedle tip and yields potentiometric MN sensors with low device-to-device variation.
The two strategies finally converge in a single MN patch for potassium sensing, which combines a potassium-selective HMN, a solid-state reference HMN, and a temperature MN. This platform showed that temperature affects the formal potential as well as the Nernstian slope. It also showed that the reference electrode drifts to a degree comparable to that of the indicator electrode. Compensating the complete cell with the co-located temperature sensor significantly reduced measurement error in vitro.
Overall, the thesis moves from extending what MN sensors can measure to the architecture that makes such measurements reproducible. Reliability emerges as a system-level property, set collectively by sensing chemistry, physical context, and fabrication architecture. The modular, 3D-printed approach developed here provides a practical basis for reproducible and multimodal MN sensors.