Semiconductive Ceramic Cap Homogenizes Bipolar RF Field

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Solution Overview

Problem

Bipolar RF energy delivery to tissue results in non-uniform thermal effects due to high current density concentrations along the edges of electrodes, leading to thermal hotspots and potential adverse skin effects such as burns and erythema.

Innovation Solution

The use of semiconductive ceramic material applied to electrodes, with varying thickness to homogenize the electrical field and high thermal conductivity to dissipate heat, minimizing thermal hotspots. The ceramic material is thicker at the inner edges and thinner at the center, and is designed to match the conductivity of the skin to reduce energy loss and spread current density evenly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If bipolar RF energy is delivered through electrodes to tissue, then thermal energy is delivered to stimulate therapeutic effect, but high current density concentrations occur along the edges of electrodes causing thermal hotspots and potential skin burns

Engineering Contradiction:

Improvetissue temperatureVSAvoidskin burns and erythema

Core Design Contradiction:

TemperatureVSObject-affected harmful factors

Solution Approach 1:

A semiconductive cap is introduced as an intermediary component between the metal electrode and the skin tissue. This cap serves as a mediator that modifies the electrical and thermal fields at the interface, reducing edge effect and distributing current more uniformly across the electrode surface, thereby preventing thermal hotspots and skin burns while still delivering therapeutic thermal energy to the tissue

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The electrical conductivity parameter of the interface between electrode and tissue is modified by introducing the semiconductive cap with specific conductivity properties. The cap's conductivity is lower than the metal electrode but higher than dry skin, creating an intermediate electrical property that reduces current concentration at edges. Additionally, the thickness of the cap is optimized to balance electrical field distribution with thermal energy delivery requirements

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If higher RF energy is delivered to overcome edge effect, then more thermal energy reaches tissue for therapeutic effect, but adverse skin effects such as burns and blisters increase

Engineering Contradiction:

ImproveRF energy delivery efficiencyVSAvoidburns and blisters

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The semiconductive cap acts as an energy distribution intermediary that allows higher total RF energy to be delivered to the tissue while preventing localized overheating. It redistributes the energy flux density uniformly across the treatment area, enabling increased energy delivery without proportionally increasing the risk of skin damage

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If electrode edges are used for energy delivery, then current path is shorter and energy delivery is more efficient, but current density concentration causes non-uniform thermal effects

Engineering Contradiction:

Improveenergy delivery efficiencyVSAvoiduniformity of thermal effects

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

The semiconductive cap introduces spatially varying electrical properties across the electrode surface. The cap's material properties and thickness are optimized to create local variations in current density that compensate for the natural edge effect, resulting in more uniform current distribution and thermal effects across the entire electrode surface while maintaining overall energy delivery efficiency

Inventive Principle:

Principle #3Local quality

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach allows for more efficient and uniform delivery of RF energy to tissue, reducing thermal hotspots and minimizing the risk of adverse skin effects while increasing the volume of tissue heated, allowing for safer and more effective treatments.

Implementation Method 1

The ceramic material is also selected to have a high thermal conductivity so that heat at the metal electrode-ceramic junction is carried away via a heat sink and does not accumulate causing unwanted skin surface heating

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

The semiconductive material can have a specified electrical conductivity to improve the spatial uniformity of energy delivered to skin or other tissues

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS9889297B2Reduction of RF electrode edge effect

Publication Date: 2018.02.13 CANDELA CORP

AI summary

A skin surface is treated with bipolar RF energy. A first semiconductive cap disposed on a first distal end of a first electrode and a second semiconductive cap disposed on a second distal end of a second electrode are applied to the skin surface. RF energy is delivered from the first electrode and the second electrode through the first semiconductive cap and the second semiconductive cap, respectively, through the skin surface. A thickness of each semiconductive cap between a blunt skin contacting surface and a curved surface affixed to a respective electrode is thicker at an inner portion and thinner at a center portion to homogenize the electrical field at the skin surface.