# Development of Robot-Assisted Untact Swab Sampling System for Upper Respiratory Disease
## 3 Experimental Results
### Swab Insertion Tests Using a Head Phantom Model  
A head phantom model (Head with Neck, 3B Scientific Inc., Hamburg, Germany) was used in NP swab insertion tests. This head phantom model is a life-size model with nostrils, the nasal cavity, and bony structures in the nasopharyngeal area. In these NP swabing experiments, a disposable swab of the same kind used for real inspections was installed in the slave robot. As shown in Figure 10, the slave robot was fixed in the robot base, which is designed for respiratory sample collection from a patient seated next to the slave robot. At the master site, the operator visually controlled the slave robot by looking at the phantom's nostrils and the swab. Since the camera and the swab are fixed on the top plate and move together with respect to the head phantom model, it is straightforward to determine the swab insertion point even from the two-dimensional images captured by a single camera.  
Since the head phantom mode is split at the sagittal plane, it was possible to utilize specific elements of the cross-sectional anatomical structure of the head and face for testing. To test remote NP swab sampling, a virtual specimen (a cotton ball soaked with orange ink) was installed on the posterior nasopharynx wall of one section of the phantom model, as shown in Figure 11a. Visual telemanipulation of the slave robot based on facial images of the phantom model was performed as shown in Figure 10b. Figure 11b shows a clean NP swab just before insertion into the nostril, Figure 11c shows the NP swab inserted into the nostril, and Figure 11d shows the swab after extraction; the ink-smeared tip of the swab reveals that the swab successfully touched the cotton ball on the posterior nasopharynx wall.  
Figure 10: (**a**) The experimental environments of the slave site and (**b**) master site in the tests using the head phantom model.  
Figure 9: Variation in force with swab displacement when pressing against a solid block.  
During NP swab sampling, the force information was also recorded. Figure 12 shows the recorded swab displacement and force data over time. The swab was pressed against the cotton ball in the head phantom twice. If the swab is inserted in the wrong direction and touches another hard structure, as shown in Figure 9, a larger force value (300) will be recorded. However, when it touches a soft structure such as a cotton ball, a smaller force value (100) will be recorded, as shown in Figure 12. We tested NP sampling several times, and all instances of swab sampling from the cotton ball based on monitoring the change in the force data were successful. As seen from these experiments, the force data, which depend on the hardness of the anatomical structures encountered when inserting an NP swab, can be used as an important basis to determine whether sampling is performed successfully in the case of a real person.  
Figure 11: **(a)** An experiment involving swab insertion and sample collection using the head phantom model: installation of a virtual specimen (cotton ball) on the posterior nasopharynx wall, **(b)** before swab insertion, **(c)** swab insertion, and **(d)** swab removal after collection of the virtual sample.  
Figure 12: Experimental results of force sensing and swab displacement during nasopharynxgeal (NP) swab sampling in the head phantom of Figure 11.