Sometimes, a sensor comes into contact not only with body fluids, such as in a dental unit for saliva suction, but the fluid also returns to the human body, as in dialysis machines or oxygenators. In these cases, the sensors must not only be resistant to the medium but also biocompatible.
This biocompatibility of the contact materials is provided by only a few sensors. Only a handful of suppliers, such as AMSYS from Mainz, offer specialized pressure sensors for such ex- and in-vivo applications. This also includes tiny IntraSense pressure sensors, only three to four hair diameters wide, for use in arterial, bladder, or brain catheters.
Biocompatible pressure sensors in size comparison
Biocompatibility
Biocompatibility refers to materials and components that are compatible with and in contact with living organisms. This property, certified according to ISO 10993, became particularly important with the implementation of the MDR regulation. Sensors that come into contact with body fluids or tissue must also meet this standard. This is made possible through the use of biocompatible materials or at least a safe coating. Sensors such as the MS5839, the disposable 1620, and IntraSense are examples of sensors that are already biocompatible and are used in many medical products.
As a specialist in sensor technology for the medical field, AMSYS offers biocompatible pressure sensors in various designs for a wide range of applications, including the IntraSense, which is probably the smallest absolute pressure sensor for in-vivo applications in catheters.
The following will introduce selected biocompatible sensors with their most common applications:
IntraSense – Probably the Smallest In-vivo Pressure Sensor for Catheter Applications 1 French
The biocompatible absolute pressure sensor IntraSense simplifies direct pressure measurement in the human body. With a size of less than 1 French (equivalent to 1/3 mm in diameter), the sensor can measure and monitor intravascular, intracranial, or intraurethral pressure. The sensor enables precise in-vivo pressure measurement in many minimally invasive devices, including catheters and endoscopes. To ensure easy system integration, the sensor can be directly exposed to various body fluids without requiring encapsulation.
This single-use absolute pressure sensor provides accurate and stable readings in the clinically relevant range of -300 mmHg to +500 mmHg and can remain in the body for up to seven days. The sensor is designed for operation in air and saline liquids such as blood, cerebrospinal fluid, or urine. As such, it is suitable for monitoring during brain and eye surgeries, as well as applications in arteriosclerosis, urology, and prenatal diagnostics. For rapid initial development, AMSYS also offers an evaluation kit with USB connection and software for initial pressure and temperature measurements for prototyping.
Intravascular Pressure Measurement
For pressure measurement in human vessels, the pressure sensor is inserted into veins, arteries, vessels, and cavities via a catheter. The sensor is available in several cable length variants, allowing for pressure measurement and external evaluation within a length of up to 180 cm. In endoscopy, the light-protected version of the IntraSense can also be used.
Intracranial Pressure Measurement
For monitoring intracranial pressure levels, the biocompatible IntraSense pressure sensor can be used for up to a certified time frame of 48 hours. With its diameter of 1 French, it is significantly smaller than the usual 1-2 mm pressure sensors used for blood flow measurement. The sensor comes into direct contact with body fluids, so reuse of this pressure sensor is not possible. The IntraSense in-vivo pressure sensor is calibrated as a standard version for the range of -300 to +500 mmHg but can also be customized.
Intraurethral Pressure Measurement
The IntraSense can also be used for pressure measurement in the human bladder, for example, during a kidney stone surgery. It ensures that no blockage occurs during the flushing of the kidney stone fragments and that the bladder pressure does not rise too high.
Link to product page of the in-vivo pressure sensor IntraSense
1620 – Affordable Disposable Sensor for External Pressure Monitoring with Media Contact
With the 1620, AMSYS also offers a relative pressure sensor designed for single-use applications such as in dialysis machines or oxygenators. These affordable sensors cover the typical pressure range for medical applications up to 300 mmHg. Like the other pressure sensors presented, it can be sterilized with ETO (ethylene oxide).
Compact Biocompatible Absolute Pressure Sensors MS5839 and MS5849 with Calibrated I²C Output
With a footprint of only 3.3 x 3.3 mm², these waterproof sensors are universally applicable and can also be used in anesthesiology, for example, due to their biocompatible gel. Through its I²C interface, the MS5839 / MS5849 provides the measured pressure and temperature signal with high accuracy at 24-bit resolution. Additionally, the module contains 6 individual coefficients that allow for software correction of pressure and temperature measurements via an external microprocessor. The MS5849, in addition to the barometric pressure range up to 2 bar, is also available for pressures up to 7 and even 30 bar.
Calibrated Relative Pressure Sensor MS5547 with I²C and Biocompatible Gel
The MS5547 is also protected from body fluids by a biocompatible silicone gel. It provides 24-bit temperature and pressure readings via I²C, which can be corrected for maximum accuracy using the individual coefficients stored in the sensor’s memory during calibration.
On the underside of the sensor, there is an opening required for a relative pressure sensor, allowing pressure measurement relative to atmospheric pressure. Relative pressures from -200 to 2000 mbar can be measured with a resolution of just 0.023 mbar.