Figure 1.
Explanation of the HIF sensor components and schematic view of the forces acting on the end of the spring blades of the HIF sensor; A-plastic discs, B- silicone discs, C-spring blade D-small hall sensor, E-magnet.
Since the max. pulling force F, max. torque T and max. distance u are known, the required dimensions of the spring blade can be calculated.
Figure 2.
Explanation of the SF sensor components; A-housing, B- spring blades oriented in a circle, C-Close up of tip with fissure, D-hall sensor and magnet.
Due to the force in the thread (F), a torque is created in the tip (T). This torque rotates the shaft in respect of the fixed housing (A). While the spring blades deform, the distance between hall sensor (G) and magnet (E) increases resulting in a change in output signal.
Figure 3.
Both sensors are installed in one thread. The left side of the thread is fixated while tension is applied on the other side of the thread with a calibrated spring balance.
Figure 4.
experimental validation setup after placement of the last stitch.
the SF sensor is installed at the right side of the incision while the HIF sensor is installed on the pulled thread left of the incision.
Figure 5.
Installation of the SF sensor.
The tip is placed over the thread and rotated towards point A until half of the tip is in contact with the tissue.
Figure 6.
Calibration graphs of Hook-In with regression lines, R2 fit and 95% CI.
Each data point represents the average of 3 measurements per load value.
Figure 7.
Upper graph; the output in newton from the HIF sensor and SF sensor during one loading cycle. Lower graph; Fdifference indicates the difference between HIF and SF output in newton.
Figure 8.
Force graphs from the HIF and SF sensors for a continuous suture with 6 stitches.
SF output; force in the thread of the second stitch. HIF output; force in the thread 50 mm under the needle. Rectangle; indicator that shows where the highest mean force in the HIF sensor was found.
Figure 9.
Force graph of averaged force per stitch with SD of all six measurements.
The force in the 2nd stitch was measured with the SF sensor and the force in the thread 50 mm under the needle was measured with the HIF sensor. Stitches were placed in the fascia.
Figure 10.
A simple “wheel” sensor with embedded measurement and feedback system.
Left, force exceeds 10 Newton and LED turns red. Right, force is between 8 and 10 Newton and LED turns green. A-Inner pin, B-external pins, C-spiral shaped bar, D-inner ring, E-external ring, F-embedded electronics for force feedback.