Design of an Integrated Photonic Distributed Force Sensor
X.E. Hsu (TU Delft - Mechanical Engineering)
W.J. Westerveld – Mentor (TU Delft - Dynamics of Micro and Nano Systems)
G.J. Verbiest – Mentor (TU Delft - Dynamics of Micro and Nano Systems)
Mohammad Mirzaali – Graduation committee member
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Abstract
From the research in the field of mechanobiology, it is evident that cells exert different force magnitudes while growing based on the biomaterial these are in contact with. The magnitude of the exerted force determines certain behaviors and mechansims of the cells, such as differentiation. For this reason, it is proposed to develop a distributed force sensor using a photonic integrated circuit with a PDMS top layer to measure the exerted forces, which can be used to study the behavior of the cells. Unlike conventional measurement techniques, this method allows cell exerted distributed forces at µN levels to be detected and monitored over a continuous time-span of multiple days and weeks. The photonic integrated circuit design consists of a sensing array of silicon photonic ring resonators for force sensing. On each sensor row, reference ring resonators are applied as well to cancel out the spectral noise caused by temperature drifts and laser wavelength repeatabilities. The reference ring resonators are shielded against cell exerted forces with a commercial hybrid-polymer, which has a Young's modulus of around 1 GPa. Using the reference ring resonators resulted in a theoretical measurement resolution of potentially as small as approximately 0.012 pm. Finally, the force limit-of-detection of the designed distributed force sensor remains below 1 µN when the force exertion area does not exceed 100 µm2 and assuming a sensitivity of 65.41 nm/RIU for one of the multiplexed ring resonators.