LED chips (edge lengths 230 to 380 µm) embedded in a radiation pit of a photodetector wafer
Research and industry worldwide are working on health wearables, mobile and barely visible systems that can record vital parameters with a high degree of comfort and under everyday conditions, analyse them and make them available to medical professionals for evaluation.
The continuous recording of so-called peripheral photoplethysmograms should provide further valuable information on human health in the future. In addition to pulse and arterial oxygen saturation, these include heart rate variability, respiratory rate as well as information on vascular stiffness and signs of rising or falling blood pressure.
Elevated blood pressure is the most important risk factor for cardiovascular disease today.
The necessary raw data are taken from the shape of the pulse wave and its temporal behaviour. A high quality of the sensor signals and the application of suitable mathematical algorithms in the data analysis are mandatory prerequisites for a variety of medical applications.
For this purpose, the CiS Research Institute is presenting miniaturised, silicon-integrated, multispectral photoplethysmography sensors at the fair. These are placed in the external auditory canal and are individually adapted to the patient.
Sensor performance and high wearing comfort were at the forefront of the development.
Up to 4 LEDs of different wavelengths are currently used to take additional measurements from different tissue depths and to detect and eliminate motion artefacts. The optical sensor can also be used to measure temperature.
The Erfurt scientists achieved this success through a holistic development approach. This includes all technological steps from sensor design to in-house sensor production, but also the necessary system knowledge, especially for the optical simulation of the skin model and the electronic signal acquisition, its processing and optimisation.
The special technological features of the microsensor solution lie in the use of 3D-structured silicon wafers on which the photodetectors are already integrated. The number and wavelengths of the light sources are mounted with high precision as bare chips in the specified cavities of the silicon wafer according to exact specifications.
Within the framework of an accompanying, still ongoing research project, the scientists and engineers of the CiS Research Institute are already working on the next task. Using the laser Doppler principle, information on blood flow and perfusion in the tissue is to be obtained.
The research and development work was partially funded by the Federal Ministry of Economics and Technology (Funding code: VP2020410KJ2, VF140011 and VF120024).
Project presentation at:
Hannover Messe, 25-29 April 2016, Hannover, Hall 4 Stand F34
SENSOR+TEST, 10-12 May 2016, Nuremberg, Hall 5 Stand 5-364