The anticipated size of the injectable Sencell Glucose Sensor (Lifecare, Norway) is planned to be 2 x 0.8 x 0.6 mm² to fit into a larger injection needle. It uses an active fluid in an osmotic pressure chamber with a glucose binding molecule (GBM) and a glucose-like ligand. The reversible reaction affinity in the chamber does not destroy any molecule when generating the signal, resulting in a long-term survival of the sensor in the body.
To miniaturize the core sensor without losing pressure sensing sensitivity, a 3D-printed nanosensor technology was employed. MEMS technology was used to build a sensor chamber with less than 1 mm³ volume, and the pressure membrane was equipped with a nano-strain sensor (4 x 1 µm²). The chamber was embedded into a circuit board chip and connected to an electronic read-out interface for sensor calibration using a standardized gas-pressure protocol.
The collected signals showed a very sensitive and linear pressure to signal relation (r²=0.996), a high reproducibility (CV = 0.2 %), no hysteresis/drift over time, and a high stability even when performing continuous repetitive calibration procedures. The observed sensor specifications (pressure range: <-300 to >300 mbar, pressure resolution 480 µbar, membrane Size 1x1mm², 300 nm thickness) would allow to track glucose changes with a resolution of 1-2 mg/dL
In conclusion, the first pilot attempt to miniaturize the core Sencell sensor technology by means of a nanostrain pressure sensor resulted in a very small osmotic pressure chamber (1mm²) suitable for the anticipated purpose