Ultrasonic sensors for single-use medical applications

Ultrasonic sensors for single-use medical applications

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Non-invasive ultrasonic sensors are widely used in medical technology: they measure flow rates with automatic fluid intake, monitor fluid levels in drip chambers, detect air bubbles in tubes or measuring chambers and detect smallest amounts of blood in dialysates.
By eeNews Europe


These sensors guarantee the highest hygienic standards and prevent contamination. In the pharmaceutical industry, the characteristics of non-invasive sensors are required as well. Especially in single-use systems, the hygienic clamp-on sensors provide multiple benefits.

Sterile single-use technologies are applied in the entire production process of biopharmaceuticals. The technology has become increasingly popular especially in the production of highly effective, small and medium volume biopharmaceuticals such as vaccines.

Your benefits: little investment costs, quick establishment, acceleration of processing times and reduction of contamination risks and cleaning efforts. Single use-technologies protect the user effectively when working with cytotoxic agents and highly efficient biological materials.

However, wearing protective clothing is still necessary to avoid any contact with the reagents. But these clothes do not only protect but also impede. With protective gloves the operation of small switches, tubing or other equipment is quite difficult. Therefore, manufacturer of disposable components must pay attention to their ease of use.

Clamp-on ultrasonic sensor for single-use processes

For this purpose, German specialist for ultrasonic sensors Sonotec has designed a single-use version of its clamp-on sensor Sonoflow CO.55. This non-invasive ultrasonic sensor checks the correct dosage and flow rate with automatic fluid intake in pharmaceutical production processes, measures the flow of liquids in PVC and flexible tubes and is also suitable for easy use and retrofitting of different devices. The tube is simply put into the sensor, so that no additional mounting is required.

The various versions of the clamp-on ultrasonic flowmeter Sonoflow CO.55, left to right: standard sensor, sensor with optimized lid for better handling, sensor made of stainless steel for use in cleanrooms with optimized lid for better handling.

For single-use applications, Sonotec modified the material and design of the sensor: the single-use version of the CO.55 is made of stainless steel, which is especially approved for cleanroom applications. Furthermore, the sensor’s lid makes it easier to handle it with gloves. The Sonoflow meets all criteria for use in cleanrooms and is available for many different tube diameters just like all sensors of the Sonoflow CO family.

In the filling process of protein biology products a hinged lid version of the non-invasive sensors of the Sonocheck ABD06 series is used.

Detect micro air bubbles reliably

Non-invasive ultrasonic sensors are also in demand for a new DNA analysis machine. During the analysis process, which determines the order of the four bases adenine (A), cytosine (C), guanine (G), and thymine (T), micro air bubbles can appear in the analyzed liquids. Even bubbles smaller than 1 µl would destroy the sample completely or produce incorrect results.

In such cases, the clamp-on air bubble detector Sonocheck ABD06.85 is called into action. Due to its high sensitivity the sensor reliably detects even these micro bubbles smaller than 1 µl in PEEK and PTFE tubing with an inner diameter of 0.79 mm (outer diameter: 1.59 mm).

Sonotec designed the extremely sensitive clamp-on ultrasonic sensor Sonotec ABD06.85 especially for the detection of micro air bubbles (< 1 μl) in DNA analysis fluids.

Another version of the contactless sensors of the Sonocheck ABD06 family is used in the filling process of protein biology products. The sensor checks if bubbles smaller than 1 µl occur in PTFE tubing. The Sonocheck ABD06 – the most suitable sensor for the task – convinces furthermore through its advanced software, which allows for easy parameterization and monitoring of the sensor performance. The customer also uses serial communication protocols for estimating the bubble size and tracking the estimated fluid loss.

The Sonocheck ABD06 sensors are part of a series of clamp-on ultrasonic sensors that detect air bubbles in liquid-filled tubes and measuring chambers – they allow fluid monitoring as well as full-empty detection. These sensors easily adapt to varying acoustic conditions and guarantee high measurement stability to varying environmental conditions.

The measurement cycle is 200 µs, the reaction time is typically 1 ms. The ultrasonic sensor has a user-specific programmable micro-controller with extendable functionalities such as fail-safe and serial communication. Additionally, a RS485 interface and a power output (0/4 … 20mA) are possible features of the sensor.

Redundant air bubble sensor

Also part of the clamp-on ultrasonic sensors for non-invasive air bubble detection is the redundant Sonocheck ABD08. The patent-pending cubic device combines two ultrasonic sensors in one housing with an edge length of 35 mm. Thus, it meets the requirements of the third edition of the European standard EN 60601-1. Furthermore, the sensor fulfils the stringent demands of the US Food and Drug Administration (FDA) with respect to reliability and accuracy of sensors used in medical devices.

With reference to the redundancy of the sensor, it is absolutely impossible that air bubbles enter into the patient’s bloodstream. The technology is independent of colour and transparency of the tubing and fluids. However, the integration of two sensors into one housing leads to electric crosstalk of the two ultrasonic channels. Sonotec solved this problem by an intelligent design, which includes not only the electronics, but also the acoustic path. The result is a complete and safe redundancy.

Adaptable to specific applications

All thesed non-invasive ultrasonic sensors have optionally configurable switch, power (0/4 … 20 mA) or pulse outputs. A serial interface allows for connecting to a computer, and thus easy parameterization and detailed analysis by using monitor software. Hence, the customer is even able to test the sensors and – at a given frame – to make adjustments to his specific needs. In addition, the sensors’ design, interfaces and features such as safety routines or power supply can be customized application-specific by Sonotec.

About the author:

Anne Luise Gellner is Head of Marketing at Sonotec GmbH – www.sonotec.de

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