CiS is active in the field of industrial research and the development of silicon-based sensors. They develop customized solutions for sensor systems and manufacture them in small series. In cooperation with CiS, we developed the product design of a wearable in-ear pulse oximeter for measuring the arterial oxygen saturation based on an existing prototype.
The content presented has been shortened and serves as overview only.
The prototype of the In-Ear Pulse Oximeter has a PPG sensor and can measure heart rate, heart rate variability and arterial oxygen saturation. The silicon chip of the sensor has three functions: It serves as a carrier for built-in LEDs, its 3D structured cavity is used for light shaping and the integrated photodiode is the detector.
The infrared, red and green light have special wavelengths and are particularly well absorbed by hemoglobin (red blood pigment) in the superficial venous plexus. Light rays of the wavelengths 525nm, 660nm, 905nm are emitted from the LED's and then reflected and registered by photodiode.
The market analysis shows a variety of wearable products. However, none of them can measure arterial oxygen saturation. This is why this unique selling proposition should be reflected in the design and function of the In-Ear Wearables for CiS.
Usability tests with comparable products have shown that the devices tend to slip out of the ear during training. Thus, the measured data is distorted or not recorded at all. Another problem was that the wearables were too conspicuous and their look reminded of hearing aids.
To get a feeling for the production technology and individual injection molded parts, the wearables from the usability test were disassembled and upgraded according to their advantages and disadvantages.
As the CiS wearable should sit discreetly in the ear, but since the battery charging capacity of most in-ears is limited, a mobile charging case should be considered. Moreover, the app should adjust to the user’s fitness level and be able to improve it gradually.
The in-ear pulse oximeter should also record vital signs without the use of a smartphone so that they can be transmitted and evaluated later. Since a one-sided in-ear wearable can lead to balance problems, the product must not impair hearing.
After the requirements for the device were compiled, first sketches for the respective criteria were drawn and discussed. These sketches were the basis for the product design of the Wearable In-Ear Pulse Oximeter.
In order to get a feeling for the necessary dimensions, the first models were manufactured and tested. This created the technical conditions necessary for modelling in 3D.
3D CAD PROTOTYPING
After the final selection of sketches, the design was further refined, modeled in Solidworks 3D, printed in 3D and tested for ergonomic criteria.
This allowed the product design of the in-ear pulse oximeter to be refined step by step and details to be improved.
The pictures are from the idea phase. They do not show the final solution.
The case of the In-Ear Pulse Oximeter is based on a circular shape with round edges. To improve the fit inside the ear, the wearable is enclosed by a silicone shell, while the "shark fin" on the sheath provides a reliable grip inside the ear and gives the product a unique optical feature.
The PPG sensor is built into the earplug and positioned in such a way that the wearable can be worn in both the left and right ear with the appropriate case. An air channel extends through the entire housing so as not to restrict hearing. The funnel-shaped element enhances the function on a visual level.
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