Research On Package Properties Of Intraoperative Pressure Sensor For Lumbar Surgery

There are complex nerve tissues near the lumbar surgery site. In order to fully expose the surgical field and to avoid accidental injury, a nerve retractor can be used to retract the nerve root. Improper retraction may cause damage to the nerve root, which will affect the efficiency of the surgery and cause postoperative complications. Thus, a sensor is installed in the retractor to obtain the mechanical information of the retracted nerve root and provide qualified reference to surgery operator. However,stress concentration exists widely in retractors in related research, which can cause second damage to nerve root and bring out the error between measured value and the actual maximum value of stress in nerve root.Focused on the special using occasion of the MEMS sensor on the retractor, the package is optimized to release the stress concentration. The following work is completed:1. Nerve root model with viscoelastic properties is established. After applying a constant displacement load, the stress relaxation curve of nerve root is obtained, which reflects its viscoelastic properties.The mechanical character of the model is verified.2. The package of the sensor is designed, and the force-voltage relationship is obtained.Taking full account of "hammock effect", package outline with a buffer is designed. Comparison is made between package of single and double encapsulation, and double package is finally selected. Piezoelectric ceramic is selected as the core of the transducer, and the stress-voltage conversion relationship in the current package is obtained by simulation.3. Contact analysis is conducted between the sensing module and the nerve root Relationship with the displacement of sensing module is obtained for both the stress of contact center and that of contact edge.that provides important guidance for assessing the error between the actual damage on nerve root and the measured value of the sensor.This paper design the sensor based in the biomechanics of the measured biological tissue.Based on the biomechanical characteristics of the nerve root, a nerve root model with viscoelastic properties is established.We concern macro-mechanical properties of the model. The material model is complexed to simplify the model structure. Through the study of the model of the nerve root in contact with the sensor, the deviation between the stress at the contact center and that at the contact edge is obtained, which can provide guidance for error correction later.