Tonsillectomy is one of the most common procedures in otolaryngology, routinely performed for recurrent acute tonsillitis, peritonsillar abscesses, and obstructive sleep apnea caused by tonsillar hypertrophy. Yet despite its familiarity, the procedure presents a persistent surgical challenge: how to remove tissue efficiently while controlling bleeding and minimizing collateral injury.
Conventional cold dissection provides direct mechanical cutting but offers limited inherent hemostasis and can be associated with postoperative pain and bleeding. High-frequency electrosurgical instruments address bleeding more effectively, but their reliance on resistive heating can produce substantial thermal injury to surrounding tissues. Low-temperature plasma ablation offers an attractive alternative, combining tissue dissection and coagulation while reducing thermal damage and supporting faster postoperative recovery.
A research article published in Progress in Medical Devices (DOI: 10.61189/409228vdbtgj) takes a closer look at a component of plasma ablation devices that has received comparatively little attention: the electrode itself. Led by first author Siqi Zhao, with Lin Mao as corresponding author, the research team designed three novel plasma ablation electrode configurations and evaluated their electrothermal behavior and ablation performance through finite element simulation and ex vivo experiments.
Rather than simply asking how plasma ablation systems can be better cooled or irrigated, the study asks a more fundamental engineering question: Can redesigning the electrode improve plasma generation and tissue ablation?
Beyond Fixed Electrode Designs
Much of the previous development of low-temperature plasma scalpels has focused on improving irrigation, suction, cooling, and anti-clogging systems. These advances help maintain a stable plasma layer and control heat accumulation, but another limitation remains: conventional devices often use fixed, non-replaceable electrode heads with relatively uniform geometries.
That can be problematic because surgical anatomy and operative requirements vary. An electrode geometry suitable for one tissue interface may not provide the optimal electric field, discharge behavior, or ablation profile in another.
To address this limitation, the researchers developed three electrode configurations: a ring-needle electrode, a needle electrode, and a cylinder electrode. Each was fabricated from titanium, and the electrode head was designed with a magnetic coupling mechanism that could support interchangeable configurations. The concept is straightforward but potentially important: rather than forcing one electrode geometry to accommodate every surgical situation, surgeons could select a tip better suited to the specific operative requirement.
Modeling What Happens Around the Electrode
Designing a new electrode is only the first step. For low-temperature plasma ablation to work effectively, the local electrical and thermal environment must support plasma generation without causing excessive collateral heating.
The team therefore used COMSOL Multiphysics to model coupled electric and thermal fields around the three electrode configurations in physiological saline. The simulation incorporated the Electric Currents and Heat Transfer in Solids modules, allowing the researchers to examine how electrode geometry affected electric field intensity and temperature distribution.
The simulations revealed highly localized thermal effects around the electrodes. Peak temperatures differed among the three designs, while temperatures decreased rapidly with increasing distance from the electrode surface. This localization is particularly relevant to plasma ablation, where sufficient energy must be concentrated near the active electrode while surrounding tissues should ideally remain protected from excessive thermal exposure.
Electric field modeling revealed an even more striking difference.
The needle electrode reached approximately 1.57 × 106 V/m in its central region, while the cylinder electrode produced approximately 1.6 × 106 V/m near the electrode. The ring-needle design showed substantially stronger local field enhancement: electric field intensity exceeded 1.8 × 106 V/m across much of the discharge region and reached a maximum of approximately 3.4 × 106 V/m.
This matters because the study used approximately 1 × 106 V/m as the empirical electrical breakdown threshold for the vapor layer. Once the local field exceeds this threshold, electrical breakdown can initiate electron avalanche ionization and facilitate plasma formation. The simulations therefore suggested that all three designs could create conditions compatible with plasma generation, but that the ring-needle geometry offered the strongest local electric field enhancement.
From Simulation to Real Tissue
A promising simulation does not necessarily translate into effective tissue ablation. The researchers therefore fabricated the electrode tips and tested them experimentally in physiological saline and ex vivo porcine liver tissue.
Each electrode was evaluated at four voltage levels — 180, 220, 260, and 300 V — allowing the team to compare both discharge behavior and tissue ablation performance under progressively increasing electrical input.
The discharge experiments showed a clear voltage-dependent effect. Plasma became progressively more apparent as voltage increased, and at 300 V the discharge was brightest and most stable. Importantly, the three electrode geometries did not behave identically. At the highest tested voltage, the ring-needle electrode produced the brightest discharge, followed by the needle electrode, while the cylinder electrode showed the weakest discharge behavior.
These observations closely mirrored the electric field simulations, providing experimental support for the idea that electrode geometry can directly influence plasma formation.
Why the Ring-Needle Electrode Stood Out
The most clinically relevant question, however, is not which electrode produces the brightest plasma. It is which design can remove tissue effectively while limiting unintended thermal injury.
Here, the ring-needle electrode emerged as the strongest overall performer.
Across standardized voltage conditions, the study reported a consistent hierarchy of ablation performance: ring-needle > needle > cylinder. Effective ablation depth increased with voltage for all three electrode types. At 300 V, the ring-needle electrode produced a comparatively large effective ablation region while maintaining a small area of thermal damage.
The authors attribute this performance, at least in part, to the stronger local electric field generated by the ring-needle geometry. A stronger field facilitates electrical breakdown and plasma generation, potentially shifting the tissue effect toward more effective plasma-mediated ablation and away from uncontrolled thermal injury.
This distinction is important. Simply increasing voltage is not necessarily desirable: beyond an appropriate range, greater energy input may increase damage to surrounding normal tissue. The goal is therefore not maximum power, but an optimal combination of electrode geometry, electric field distribution, plasma stability, ablation depth, and thermal safety.
One Device, Different Surgical Needs
Perhaps the broader contribution of the study lies in its design philosophy.
Instead of treating the plasma scalpel tip as a fixed component, the researchers propose an electrode system in which different geometries could potentially be selected according to the surgical situation. The study highlights a design featuring interchangeable electrode tips, allowing different configurations to accommodate different operative requirements.
This could be particularly valuable in procedures such as tonsillectomy, where surgeons must balance precise dissection, effective hemostasis, accessibility within a confined anatomical space, and protection of adjacent normal tissues.
The findings also illustrate why electrode geometry should not be considered a purely mechanical design choice. Shape influences electric field concentration; electric field concentration influences breakdown and plasma generation; and plasma behavior ultimately influences how tissue is ablated.
In other words, electrode architecture becomes part of the therapeutic mechanism itself.
From Porcine Liver to the Operating Room
The results are encouraging, but the study represents an early engineering and preclinical step rather than a demonstration of clinical superiority.
The ablation experiments were performed on ex vivo porcine liver tissue, not living tonsillar tissue or patients. The authors acknowledge that longer-term studies are needed to establish safety and efficacy and that further optimization remains necessary, particularly for the cylinder electrode. In the current experiments, the cylinder configuration showed relatively weak plasma-mediated ablation and greater thermal effects, potentially because of insufficient electric field strength, suboptimal electrode extension length, or incomplete contact between the bipolar cutting surface and tissue.
Future work will therefore need to refine electrode dimensions and geometry, optimize electrical parameters, and determine whether the advantages observed in saline and porcine liver translate to clinically relevant tissues and surgical conditions.
Still, the study provides a useful proof of concept: changing the geometry of a plasma ablation electrode can meaningfully alter electric field distribution, plasma stability, ablation efficiency, and thermal damage.
By combining mechanical design, finite element simulation, and experimental validation, the researchers offer a new route toward more adaptable low-temperature plasma ablation devices. Among the three configurations tested, the ring-needle electrode showed the most promising overall performance, suggesting that carefully engineered, interchangeable electrode structures could help move plasma-based surgical instruments toward greater precision, flexibility, and clinical versatility.
Publication Details
Journal: Progress in Medical Devices
Article Title: Design and Experimental Study of Novel Plasma Ablation Electrodes
Article Type: Research Article
Website Link: View Article
DOI: 10.61189/409228vdbtgj
Publication Date: June 30, 2025
First Author: Siqi Zhao
Corresponding Author: Lin Mao (linmao@usst.edu.cn)
Affiliation: Shanghai Institute for Minimally Invasive Therapy, School of Health Science and Engineering, University of Shanghai for Science and Technology
