Injectable Sensors Based on Passive Rectification of Volume-Conducted Currents

Area of Science:

• Biomedical Engineering
• Implantable Sensors
• Minimally Invasive Devices

Background:

• Minimally invasive sensing implants deployed via catheterization or injection are preferred over surgical implants.
• Current implant technologies are limited by bulky components for powering and interrogation, hindering miniaturization.
• Existing methods impede the development of truly minimally invasive active and passive sensing systems.

Purpose of the Study:

• To propose a novel approach for developing miniaturized passive sensing systems.
• To overcome limitations of previous implantable sensing systems regarding size and invasiveness.
• To demonstrate a proof-of-concept for injectable, thread-like implants for tissue conductivity measurement.

Main Methods:

• Developed thread-like implants (0.95 mm thick) with electrodes and a simple RLC circuit (resistor, inductor, capacitor).
• Utilized high-frequency (≥1 MHz) alternating current bursts for non-invasive interrogation via volume conduction.
• Captured and processed implant-generated voltage signals to determine surrounding tissue conductivity.

Main Results:

• Successfully developed and characterized a flexible, injectable implantable sensor.
• The system achieved an accuracy of ±10% for tissue conductivity measurements ranging from 0.2 to 0.8 S/m.
• Demonstrated feasibility of using off-the-shelf components for miniaturized implantable sensors.

Conclusions:

• The proposed approach enables the development of highly miniaturized, injectable passive sensing implants.
• This technology overcomes key limitations of current implantable devices, paving the way for advanced minimally invasive diagnostics.
• The system offers a promising solution for in-situ tissue property assessment with high accuracy.