Optimizing Bio-Inspired and Implantable Batteries for Next-Generation Medical Devices

 

Chemie  |  Biochemie  |  Medizin

 

Darius Müller, 2007 | Villars-sur-Glâne, FR

 

Compared to conventional lithium batteries, bio-inspired artificial electric organs, or gel batteries offer a soft, flexible, transparent and biocompatible alternative for implantable medical devices. Currently, their main limitations are relatively low power density and open-circuit potential (Voc). This work explores polyelectrolyte doping to increase fixed charges and thus enhance gel battery performance regarding its open-circuit potential. Experiments with 2 cationic and 3 anionic polyelectrolytes revealed an increase of up to 35 mV in open circuit voltage but accompanied by higher internal resistant compared to the control. To optimize gel stability and performance, dopant characeristics such as concentration, molecular weight, pKa and structure should be systematically optimized in future studies.

Introduction

How does a set of positively and negatively charged polyelectrolytes added to the ion-exchange gels at varying concentrations affect the gel battery performance metrics, such as internal resistance, open-circuit potential, and power density?

Methods

Batteries were fabricated by combining reagents with water, and selected polyelectrolytes for ion-exchange gels, then UV-curing the solutions into five gels per battery, and sandwiching the gels by self-fabricated silver electrodes. 10 variations of batteries with either doped CEM or AEM or both were then connected to circuit to measure the open-circuit potential, internal resistance, and power density.

Results

The initial concentration of polyelectrolyte doping caused severe performance degradation with four-fold lower open-circuit potential and near-zero power density. Reducing dopant concentrations yielded substantial improvements, resulting in open circuit voltage improvements of up to 35 mV (about 20%). However, internal resistance remained higher than the control gel (2-3 fold higher), offsetting power density gains.

Discussion

Dopants are incorporated by physically mixing them into the gel matrix without covalent bonding. Uniform mixing and distribution are crucial for the anticipated increase in fixed charges. Polyelectrolyte properties such as size (molecular weight) and structure (linear vs branched) affect the mobility, and indeed we have observed better performance for larger polyelectrolytes. Additionally, dopants are incorporated via physical entrapment rather than covalent bonding to the gel network. Covalent integration may reduce obstruction of ion transport pathways and consequently lower internal resistance.

Conclusions

This work achieved unprecedented open-circuit voltages in gel batteries—critical for energy-dense medical implants. Single-unit gel-batteries produced ~200–230 mV; stacking multiple units in series could achieve the ~3V required for cardiac pacemakers while maintaining the soft, flexible, biocompatible advantages of these systems. However, long-term stability and biocompatibility testing, such as evaluating dopant retention, voltage stability, and biological response over weeks to months remains essential for translating these systems toward real-world implantable applications. Further optimization of dopant concentrations and covalent incorporation strategies could unlock the full potential of these bio-inspired systems for sustainable, biocompatible medical devices that enhance human well-being.

 

 

Würdigung durch die Expertin

Sina Saxer

Im Rahmen des Schweizer Jugend forscht Wettbewerbs 2026 würdigen wir die Maturaarbeit von Darius Müller („Optimizing Bio-Inspired and Implantable Batteries for Next-Generation Medical Devices“). Die Arbeit behandelt die Optimierung implantierbarer Batterien und damit ein hochaktuelles Forschungsthema. In zwei Wochen entwickelte und testete er zwölf Gelbatterien mit unterschiedlichen Dotierungen und charakterisierte diese systematisch. Die Arbeit überzeugt durch einen ausgeprägten experimentellen Zugang, Eigenständigkeit und eine reflektierte Diskussion der Ergebnisse.

Prädikat:

Gold

Sonderpreis «London International Youth Science Forum (LIYSF)» gestiftet von der Metrohm Stiftung

 

 

 

Kollegium St. Michael, Fribourg
Lehrer: Tobias Fuhrer