Silicone SpO2 sensor with robust TPU cable
GPE has demonstrated a knack for dealing with highly complex challenges. Our new silicone SpO2 sensor with TPU cable.
Safe blood oxygen measurement thanks to ‘Great Performance Engineering’ – the manufacturer of a newly developed sleep diagnosis system tasked us with the re-engineering its custom connector on the one hand and the connection of the sensor with a robust TPU cable on the other. The result is a reliable, absolutely watertight SpO2 sensor with a slim connector that has excellent alternate bending properties. In this way, it guarantees reliable blood oxygen measurement in sleep diagnostics. After all, pulse oximetry is essential to patients’ survival.
Nothing’s possible without oxygen. Inhaled, it enriches the blood in the lungs, which – pumped through the veins from the heart – supplies the muscles. Pulse oximetry is used to observe this connection between respiration, oxygen conversion and lung function via the degree of oxygen saturation. Vital functions of the patients are monitored by means of SpO2 sensors, which must meet the most exacting standards in terms of function, reliability and quality.
Our job was to fit an existing SpO2 sensor with a new – customised – connector for a newly developed sleep diagnosis system. On the one hand, we needed to engineer a connector and cable assembly offering excellent alternate bending properties in a small package.
On the other hand, the focus was on achieving a secure connection between the silicone and TPU for the sensor connector. On top of that, this required highly process-optimised workmanship as well as cost optimisation through the use of new transmitter and receiver components for the red and infrared diodes. The design had to be carried out in accordance with EN 80601-2-61 – Part 2-61. This standard defines the specifications for the safety of medical electrical equipment, including the essential performance characteristics of pulse oximetry equipment.
The challenge of this project on the connector side was to develop a grommet that would both meet the limited installation space of the slim connector in relation to the cable diameter and also have excellent alternate bending properties.
The second challenge was to ensure that the material connection between the TPU cable and the silicone finger cap on the sensor side was watertight. On the one hand, the new diodes and sensor elements as well as the TPU cable in the heated silicone mould had to be overmoulded with silicone. And both without damaging the diodes and sensor elements as well as the cable sheath. It was a complex and complicated task, which – befitting the finger cap for which the SpO2 sensor was redesigned – required a particularly fine touch.
Here at NICOLAY, we solved this problem by thermally decoupling the areas in the silicone mould where the sensors were to be overmoulded, thus preventing the TPU cable sheath from melting. The material bond between the silicone material of the finger cap on the one hand and the cable on the other was ultimately achieved by means of a special surface treatment. In other words, we developed a slim mounting for a slim connector and precisely defined the soldering parameters and selected the soldering equipment accordingly. We overcame the challenge of overmoulding the diodes with silicone by using sensors that are as heat-resistant as possible. The integrity of the electronic components is constantly documented via ongoing functional tests during the injection moulding process.
For the connector side, after selecting the appropriate material, it was possible to adapt the specially designed grommet precisely to the connector’s housing. The result stands out for its impressive alternating bending properties and outstanding reliability.
The result is a newly engineered, absolutely watertight SpO2 sensor whose connector has a specially developed and precisely adapted grommet, while on the sensor side, two materials – silicone and TPU – have been reliably bonded together. This guarantees absolutely reliable blood oxygen measurement in sleep diagnostics. After all, proper oxygen saturation is vital to patients’ survival.