Improved electron paramagnetic resonance spectroscopy sensitivity for aqueous biological samples using low-volume multi-channel cells and dielectric resonators. Rev Sci Instrum 2026 Feb 01;97(2)
Date
02/05/2026Pubmed ID
41642074DOI
10.1063/5.0285590Scopus ID
2-s2.0-105029613844 (requires institutional sign-in at Scopus site)Abstract
Reducing sample volumes for electron paramagnetic resonance (EPR) spectroscopy applications places increasing demands on hardware design to preserve or enhance EPR signal intensity. This work presents the design, fabrication, and testing of dielectric resonators and multi-channel aqueous sample cells for applications in X-band (nominally 9.5 GHz) EPR. Our aim was to maximize the EPR signal intensity for sample sizes of 3-4 μl and 200 nl. These advances are summarized as follows: single-crystal sapphire and rutile dielectric resonators with very low loss tangent and high resonator efficiency; minimum dielectric resonator coupling to radiation shield to reduce ohmic losses; 3D-printed aqueous sample cells with thin multi-channel construction to minimize radio frequency dissipation in the sample; and a Gordon coupler for maximum coupling range and minimum stored energy to eliminate frequency shifts during tuning. Sample tube cross sections were designed by leveraging insights gained from analytic theory to inform finite-element modeling of electromagnetic fields. Experimental comparisons of multi-channel sample cells using a sapphire resonator exhibited a 2.2-fold increase in EPR signal intensity compared with a standard capillary at 3-4 μl, while simulations predict an additional 23% improvement with further 3D printing advances. For samples at 200 nl, a rutile dielectric resonator with a multi-channel sample cell was simulated to improve EPR sensitivity by a 2.7-fold increase compared with a capillary at the same volume.
Author List
Mett RR, Anilkumar A, Garces AM, Wehrley JT, Lerch MT, Klug CS, Sidabras JWAuthors
Alexander M. Garces Postdoctoral Researcher 1 in the Biophysics department at Medical College of WisconsinCandice S. Klug PhD Interim Executive Vice Chair, Professor in the Biophysics department at Medical College of Wisconsin
Michael Lerch PhD Associate Professor in the Biophysics department at Medical College of Wisconsin
MESH terms used to index this publication - Major topics in bold
Electron Spin Resonance SpectroscopyEquipment Design
Water
