Flexible Biopsy Robot with Force Sensing for Deep Lung Examination

Lung disease has become a leading cause of disease‐related death, making it one of the most serious health problems in the world. Due to the advantages of fast postoperative recovery and small trauma, transbronchoscopic biopsy has become the main method for the diagnosis of lung diseases. However, limited by the large outer diameter of the bronchoscope, insufficient flexibility of the biopsy needle, and lack of force sensing, traditional biopsy operation is simple and rough, and it is difficult to enter the deep narrow areas of the lung for examination. In this article, a flexible biopsy robot with force‐sensing ability is proposed. The robot is composed of a tendon‐actuated catheter and an inner sliding flexible needle as well as their driving systems. The experimental results demonstrate that the robot has good positioning accuracy of 0.72 mm and high flexibility and repeatability. With the cooperation of the commercial bronchoscope, the robot can reach various narrow areas of the lung to perform biopsy operations. The proposed robot has the potential to improve the diagnosis rate of lung diseases and reduce related deaths.


Introduction
Lung cancer causes approximately 350 deaths per day in the United States in 2022, [1] making it the leading cause of cancer death.Early and accurate diagnosis is of great significance to prevent further deterioration of lung diseases and improve the cure rate. [2]However, lung diagnosis has been a difficult problem due to the inherently complex structure of the lung. [3]ere are currently two approaches to reaching peripulmonary nodules: percutaneous [4] biopsy and transbronchoscopic [5] biopsy.The percutaneous biopsy is to insert a needle through the lung pleura from outside the body to collect tissue samples for histopathological analysis, but small malignant nodules are difficult to diagnose, and the diagnostic accuracy is not high. [6]In addition, the percutaneous biopsy carries a substantial risk of intraoperative complications, including pneumothorax or lung collapse. [7,8]In contrast, transbronchoscopic biopsy sends biopsy tools to lesion areas through a flexible bronchoscope. [9]The surgeon manipulates the bronchoscope through the mouth into the lung and uses their knowledge of anatomy and camera to navigate to lesion areas, using tools such as biopsy needles to perform tissue sampling. [10,11]Transbronchoscopic biopsy has less incidence of 2.2% of local recurrence with pleural dissemination than percutaneous biopsy with an incidence of 4.9%, and fewer cancer deaths. [12]owever, the standard bronchoscope with an outer diameter of about 6 mm reduces the capability of transbronchoscopic biopsy, as most lesions are located in the periphery of the lung and can only be accessed through a narrow bronchiole. [3,13]reathing motions associated with normal body functions also lead to variations in accuracy, [14] with the position of the target area changing by an average of 17.6 mm in the lung throughout the procedure, which affected the diagnosis of the procedure to varying degrees.[17] The well-known commercial bronchoscope robot systems include the Monarch system [18] and the Ion system. [19]The Monarch has a 4.4 mm scope with a 2.1 mm working channel, while the Ion has a 3.5 mm scope with a 2.0 mm working channel occupied by the camera.The camera needs to be removed prior to introducing biopsy instruments. [20]These systems have the advantages of flexibility and stability to provide better control for biopsy; however, the accompanying biopsy tools still lack controllability and rely on the scope to reach the lesion areas for biopsy.In recent years, several advanced biopsy robots have been proposed to expand the capabilities of transbronchoscopic DOI: 10.1002/aisy.202300107 Lung disease has become a leading cause of disease-related death, making it one of the most serious health problems in the world.Due to the advantages of fast postoperative recovery and small trauma, transbronchoscopic biopsy has become the main method for the diagnosis of lung diseases.However, limited by the large outer diameter of the bronchoscope, insufficient flexibility of the biopsy needle, and lack of force sensing, traditional biopsy operation is simple and rough, and it is difficult to enter the deep narrow areas of the lung for examination.In this article, a flexible biopsy robot with force-sensing ability is proposed.The robot is composed of a tendon-actuated catheter and an inner sliding flexible needle as well as their driving systems.The experimental results demonstrate that the robot has good positioning accuracy of 0.72 mm and high flexibility and repeatability.With the cooperation of the commercial bronchoscope, the robot can reach various narrow areas of the lung to perform biopsy operations.The proposed robot has the potential to improve the diagnosis rate of lung diseases and reduce related deaths.
In view of the current problems, a flexible biopsy robot for lung examination is proposed, which consists of a tendon-driven catheter with omnidirectional deflection ability and an inner sliding biopsy needle with force sensing ability.As shown in Figure 1, the robot is used in conjunction with a commercial bronchoscope.First, the bronchoscope is controlled by the surgeon to enter the bronchus near the lesion area under the guidance of the endoscopic images.Second, the flexible biopsy robot is inserted into the working channel of the bronchoscope and extends out.Third, the biopsy robot is controlled to near the lesion area by the deflection and feed movement of the tendondriven catheter.Finally, push the biopsy needle to move axially and perform biopsy operations.During the biopsy process, the puncture force of the biopsy needle is monitored in real-time to ensure safety and stability.

Design and Fabrication of Flexible Biopsy Robot
As shown in Figure 2A, the flexible biopsy robot mainly consists of a tendon-driven catheter with an inner sliding flexible needle used for biopsy operation, a steering control system used to actuate all-directional deflection of the catheter, a feed mechanism used to feed the biopsy needle and an electric slide to feed the catheter.
The tendon-driven catheter consists of a soft tube made of polycarbonate material as the transition segment, and a hinge structure (made of laser-cut stainless-steel tube) as the steering segment.The flexible biopsy needle is composed of a push rod made of nitinol material as the backbone that slides inside the catheter and a notched needle installed on the tip.The steering control system consists of a motor fixture used to install four linear motors for pulling the tendons, four motor flanges used to connect tendon clamps for connecting tendons, a guide seat used to guide tendons, and a mounting rack for connecting the steering control system with the electric slide.The feeding mechanism is composed of a motor mounting seat used to mount two servos with symmetrical center distribution, a force sensor used to measure the puncture force of the flexible needle, two sensor flanges used to mount the force sensor and push rod, two pulleys installed on the output end of servos used to feed the push rod of the biopsy needle.
The tendon-driven catheter is driven by two pairs of antagonistic tendons and can achieve omnidirectional bending without whole-body rotation.During operation, it is inserted into the working channel of the commercial bronchoscope, which can expand the biopsy ability for lung diseases.The ability to sense puncture force can improve the safety of biopsy procedures.Besides, the catheter is easy to miniaturize (with an outer diameter of 1.8 mm and an inner diameter of 1.0 mm) because the force sensor is placed in the feed mechanism without being deployed to the biopsy needle.The puncture force is transmitted from the needle to the force sensor through the push rod.

Model Analysis of Flexible Biopsy Robot
The bending ability of the tendon-driven catheter has a great influence on the flexibility and controllability of the biopsy Figure 1.Overview of the flexible biopsy robot for lung examination.The robot is used in conjunction with a commercial bronchoscope.First, the bronchoscope is controlled by the surgeon to enter the bronchus near the lesion area under the guidance of the endoscopic image.Next, the flexible biopsy robot is inserted along the working channel of the bronchoscope and extends out.Next, the biopsy robot is controlled to near the lesion area by the deflection of its steering segment and feed movement.Finally, push the biopsy needle to move axially and perform biopsy sampling.During the biopsy process, the puncture force of the biopsy needle is monitored in real-time to ensure safety and stability.
operation.Thus, the deformation model of the catheter is analyzed and characterized.As shown in Figure 3A, the assembled catheter is inserted into the working channel of the commercial bronchoscope, and the biopsy needle can extend through the push rod. Figure 3B shows the established coordinate system of the tendon-driven catheter along with the biopsy needle.Since the transition segment is inserted into the bronchoscope and its stiffness is greater than that of the steering segment, only the steering segment deforms under the actuation of tendons.The detailed derivation process is described in S1, Supporting Information.
To verify the proposed deformation model, characterization experiments are carried out.First, pull each tendon at the velocity of 1 mm s À1 which is the actuation velocity during normal operation.Then, record the actuation displacement and corresponding bending angle.To improve the reliability of the model analysis, multiple experiments are carried out and the results are plotted in Figure 3C.The error bar represents the fluctuation range of multiple measurements, while the solid point is the average.It is observed that as the actuation displacement increases, the bending angle of the steering segment increases linearly with a slope of 0.5 rad mm À1 .And the curves of the four tendons almost coincide.However, there are still some small differences.The main reason is that the tendons need to run through the transition segment and be rubbed against the tube.Based on the characterization result, the workspace of the tendon-driven catheter along with the biopsy needle is shown in Figure 3D.

Force Analysis of Flexible Biopsy Robot
During the biopsy operation, the push rod is used to push the biopsy needle forward into the tissue.Therefore, the stiffness of the push rod directly affects the limit of puncture force.On the other hand, when the tendon-driven catheter is actuated to bend, the friction between the push rod and the inner wall of the catheter will also increase, thus affecting the accuracy of the transmitted puncture force.It is necessary to analyze the characteristics of the puncture force of the actual robot for a safe biopsy operation.The force measuring system is shown in Figure 4A, including a force sensor connected with two sensor flanges, one of which is used to be fixed on the base, and another of which is used to install the guide slot.The tendon-driven is inserted into the guide slot along the inner curved groove while The flexible biopsy robot consists of a tendon-driven catheter with an inner sliding flexible needle used for biopsy operation, a steering control system used to actuate all-directional deflection of the catheter, a feed mechanism used to feed the biopsy needle and an electric slide to feed the catheter.B) CAD model of the driving systems.The steering control system consists of a motor fixture used to install four linear motors for pulling the tendons, four motor flanges used to connect tendon clamps for connecting tendons, a guide seat used to guide tendons, and a mounting rack for connecting the steering control system with the electric slide.The feeding mechanism is composed of a motor mounting seat used to mount two servos with symmetrical center distribution, a force sensor used to measure the puncture force of the flexible needle, two sensor flanges used to mount the force sensor and push rod, two pulleys installed on the output end of servos used to feed the push rod of the biopsy needle.C) CAD model of the catheter.The tendon-driven catheter consists of a soft tube made of polycarbonate material as the transition segment and a hinge structure (made of laser-cut stainless-steel tube) as the steering segment.The flexible biopsy needle is composed of a push rod made of nitinol material as the backbone that slides inside the catheter and a notched needle installed on the tip.
the biopsy needle extends and reaches the bottom.Thus, the puncture force could be simultaneously sensed by the force sensor installed on the feed mechanism and the force sensor of this measuring system.
First, the influence of the bending angle of the tendon-driven catheter on force transmission is analyzed.As shown in Figure 4B, the ratio of the transmitted puncture force to the push force is plotted when the tendon-driven catheter is actuated to bend from 10°to 140°.It is observed that as the bending angle increases, the ratio decreases and the rate of descent increases slightly.The main reason is the friction between the push rod and the catheter.Second, the maximum puncture force is tested shown in Figure 4C.The tendon-driven catheter is inserted vertically into the guide slot, and the biopsy needle extends and reaches the bottom.By moving the catheter down, the extended length of the biopsy needle can be reduced.The maximum puncture force at different extension lengths is plotted in Figure 4D.It is observed that as the length increases from 2 to 20 mm, the maximum puncture force reduces from 2.1N to 1.3N.In general, the puncture force for lung cancer is 0.264N, [29] so the proposed biopsy robot could satisfy the requirement.

Control Performance of Flexible Biopsy Robot
To control the robot to carry out flexible sampling of lesion tissue, a control strategy of the flexible biopsy robot is proposed shown in Figure 5A.The operator inputs the control command, including the steering information of the tendon-driven catheter and the feed information of the flexible needle.Then, the command is converted to the actuation information of the steering control system and feed mechanism by inverse kinematics.Finally, the robot is controlled to reach the desired area and carry out biopsy operations.
Based on the control strategy, trajectory-tracking experiment is carried out to test the positioning accuracy of the robot.During the experiment, the commercial bronchoscope is fixed, and the flexible biopsy robot is inserted into its working channel and extended.Then, the robot tip is controlled to move along the desired circle pattern based on the proposed model.The actuation displacements of four tendons are plotted in Figure 5B, and the actual trajectory is plotted in Figure 5C.It is observed that the actual trajectory is basically consistent with the ideal trajectory, showing high control accuracy.To quantitatively analyze the error of trajectory tracking, the total error or its projection error on the X, Y, and Z axis are respectively plotted in Figure 5D.It is observed that the error fluctuates within a small range.However, there are relatively large errors in some angles, which might source from the processing of hinge structure and assembling of tendons.Furthermore, the mean value and standard deviation are plotted in Figure 5E.It is observed that the projection error on the Z axis is lower than others, and the mean total error reaches 0.72 mm, showing good positioning accuracy.The assembled catheter is inserted into the working channel of the commercial bronchoscope, and the biopsy needle can extend through the push rod.B) Established coordinate system of the catheter.Since the transition segment is inserted into the bronchoscope and its stiffness is greater than that of the steering segment, only the steering segment deforms under the actuation of tendons.C) The relationship between the actuation displacement and corresponding bending angle.As the actuation displacement increases, the bending angle of the steering segment increases linearly with a slope of 0.5 rad mm À1 .D) The workspace of the tendon-driven catheter along with the biopsy needle.

Plane Biopsy Experiments
To test the flexibility and maneuverability of the robot, plane biopsy experiments are performed shown in Figure 6.Three simulated lesions were observed on the plane.Initially, the flexible biopsy robot is inserted into a commercial bronchoscope and extended for a distance.During experiments, the robot is controlled by teleoperation to perform biopsy operations on three lesions, respectively.
Three groups of biopsy experiments are respectively shown in Figure 6A.It is observed that the tendon-driven catheter is first controlled to point to the lesion, after which the biopsy needle is extended and inserted into the lesion.The robot successfully performed all biopsy experiments, indicating that it has good controllability and a large range of operating space.In addition, puncture force is also analyzed in each biopsy process.When the tendon-driven catheter points to the lesion, let the feeding mechanism reciprocate three times to drive the biopsy needle into the simulated lesion and draw the force variation curves in Figures 6B. it is observed that the variation of puncture force in repeated biopsy operations is roughly consistent, indicating that the proposed biopsy robot has high repeatability and stability.

in vitro Bronchial Biopsy Experiments
To test the clinical application of the flexible biopsy robot, in-vitro bronchial biopsy experiments are performed shown in Figure 7A.The experimental setup consists of a commercial bronchoscope with its host, an electric slide with its driver, a transparent bronchial phantom, and the proposed biopsy robot.The biopsy robot is inserted into the working channel of the .Force analysis of flexible biopsy robot.A) Experiment setting of force measurement at different bending angles.The force measuring system includes a force sensor connected with two sensor flanges, one of which is used to be fixed on the base, and another of which is used to install the guide slot.The tendon-driven is inserted into the guide slot along the inner curved groove while the biopsy needle extends and reaches the bottom.B) The ratio of the transmitted puncture force to the push force.As the bending angle increases, the ratio decreases and the rate of descent increases slightly.The main reason is the friction between the push rod and the catheter.C) Experiment setting of the maximum puncture force at different extension lengths.The tendon-driven catheter is inserted vertically into the guide slot, and the biopsy needle extends and reaches the bottom.By moving the catheter down, the extended length of the biopsy needle can be reduced.D) The maximum puncture force at different extension lengths.With the length increasing from 2 to 20 mm, the maximum puncture force reduces from 2.1N to 1.3N.In general, the puncture force for lung cancer is 0.264N, so the proposed biopsy robot could satisfy the requirement.
commercial bronchoscope and aids the bronchoscope in performing biopsy operation by teleoperation.
As shown in Figure 7B,C, the biopsy robot respectively entries the left distal bronchus and the right distal bronchus to perform biopsy operations with the cooperation of the bronchoscope.It is difficult for traditional bronchoscopes to access the distal bronchioles due to their large outer diameter and limited flexibility.Figure 7D,E shows the biopsy operations of the biopsy robot outside the bronchial phantom.It is observed that the biopsy robot gradually penetrates the bronchial wall and is controlled to point to the lesion, then the biopsy needle is extended and inserted into simulated lesion tissue.These results demonstrate that the proposed biopsy robot can extend the capability of traditional bronchoscopes to perform biopsy operations in narrow lung areas.
During the biopsy operation, the puncture forces are recorded for analysis.Figure 7F shows the force variation curves in the above experiments (trials 1, 2, 3, and 4 correspond to Figure 7B-E.It is observed that the average puncture time is about 1.2 s, and the maximum puncture force is below 0.5N. Figure 7G shows the distribution of the maximum and mean value of puncture force in three repeated biopsy operations.It is obvious that the biopsy operation has high repeatability, and the maximum and mean values of different trials fluctuate The operator inputs the control command, including the steering information of the tendon-driven catheter and the feed information of the flexible needle.Then, the command is converted to the actuation information of the steering control system and feed mechanism by inverse kinematics.Finally, the robot is controlled to reach the desired area and carry out biopsy operations.B) The actuation displacements of desired circle trajectory.C) The scatter plot of the actual trajectory and desired trajectory.The actual trajectory is basically consistent with the ideal trajectory.D) The error variation curves of the total error and projection errors on the X, Y, and Z axis.The error fluctuates within a small range.However, there are relatively large errors in some angles, which might source from the processing of hinge structure and assembling of tendons.E) The mean value and standard deviation of errors.The mean total error reaches 0.72 mm, showing good positioning accuracy.
within a narrow range.These experimental results demonstrate that the robot can safely and smoothly perform biopsy operations with the force sensing ability.

Discussion
Table 1 summarizes the advantages and disadvantages of current advanced biopsy robots.[23] This design helps to further reduce the outer diameter of the robot catheter, but the rotation can easily induce a collision between the robot and human tissues.Besides, there are also some new design methods, such as the pneumatic catheter with camera channel and needle channel, [24] biopsy robot based on concentric tube architecture, [25] origamiinspired retractable biopsy robot, [26] and soft magnetic actuated robot. [27,28]However, the above-mentioned robots also have limitations, which makes it difficult to realize more flexible steering control and do not have force-sensing ability.
In order to remedy the above defects, a biopsy robot with omnidirectional deflection and force-sensing ability is proposed.Tendon actuation is used to achieve omnidirectional deflection due to the advantages of a large bending angle of about 140°a nd high load capacity.Considering that only the steering segment (hinge structure) would deform under the actuation of tendons, an inner sliding flexible biopsy needle is used to improve the robot's flexibility and safety (with force sensing ability).The biopsy needle can achieve nearly 1N puncture force at a 20 mm extension length, meeting the needs of the biopsy of lung lesions.
The experiments demonstrate that the proposed biopsy robot has good performance and can enter narrow areas of the lung to perform biopsy operations.However, there are still some aspects to be improved: The first is to further reduce the outer diameter of the catheter to a submillimeter level with the help of advanced processing technology.The second is to further improve the   flexibility and controllability of the biopsy robot with the help of advanced driving and control methods.The third is to combine with advanced bronchoscope robots to achieve more flexible biopsy operations.

Conclusion
In this article, a flexible biopsy robot with omnidirectional bending and force-sensing ability has been proposed.The robot is composed of a tendon-actuated catheter and an inner sliding flexible needle along with their actuation systems, having good positioning accuracy (0.72 mm) and flexible steering ability.With the cooperation of a commercial bronchoscope, the robot can reach various areas of the lung to perform biopsy operations.
The experimental results show that the robot has good mobility and repeatability and the puncture force of multiple biopsy operations is almost consistent.The proposed robot has the potential to realize the examination in deep narrow lung areas and improve the diagnosis rate of lung diseases.

Experimental Section
Materials: The used commercial bronchoscope is purchased from Qisheng (Shanghai) Medical Device Co., Ltd.The Nickel titanium alloy used for the push rod is purchased from a grocery store in China.The electric slide used for the feed movement of the tendon-driven catheter is purchased from Oriental Motor Electric Machinery Trading (Shanghai) Co., Ltd.The servo used for feed movement of the flexible needle is purchased from ROBOTIS CHINA Co., Ltd.The soft tube used as the transition segment of the catheter is purchased from a grocery store in China.The force sensor used for measuring the puncture force is purchased from FUTEK GROUP Co., Ltd.
Fabrication: The biopsy needle is processed by the Shenzhen Maodeng 3D Printing Co., Ltd. using a high-definition ultrafine plastic printing material (similar to ABS material, with 0.016 mm printing accuracy).The tendon clamp, motor flange, and sensor flange are processed by Changzhou Hengsheng Chang Electronics Co., Ltd, using aeronautical aluminum materials.All other connecting parts of the driving systems are processed by Shenzhen Wenext Technology Co., Ltd, using Nylon 7500 materials.
Control System: The robot control system is composed of a computer, motor drivers, and a flexible biopsy robot.The computer plays the role of the brain and interprets the operator's commands into the control instructions of different motors, which are sent to the corresponding drivers and finally control the robot's movement.

Figure 2 .
Figure 2. Design and fabrication of flexible biopsy robot.A) CAD assembly drawing of the robot.The flexible biopsy robot consists of a tendon-driven catheter with an inner sliding flexible needle used for biopsy operation, a steering control system used to actuate all-directional deflection of the catheter, a feed mechanism used to feed the biopsy needle and an electric slide to feed the catheter.B) CAD model of the driving systems.The steering control system consists of a motor fixture used to install four linear motors for pulling the tendons, four motor flanges used to connect tendon clamps for connecting tendons, a guide seat used to guide tendons, and a mounting rack for connecting the steering control system with the electric slide.The feeding mechanism is composed of a motor mounting seat used to mount two servos with symmetrical center distribution, a force sensor used to measure the puncture force of the flexible needle, two sensor flanges used to mount the force sensor and push rod, two pulleys installed on the output end of servos used to feed the push rod of the biopsy needle.C) CAD model of the catheter.The tendon-driven catheter consists of a soft tube made of polycarbonate material as the transition segment and a hinge structure (made of laser-cut stainless-steel tube) as the steering segment.The flexible biopsy needle is composed of a push rod made of nitinol material as the backbone that slides inside the catheter and a notched needle installed on the tip.

Figure 3 .
Figure 3. Model analysis of flexible biopsy robot.A) Physical view of the robot catheter.The assembled catheter is inserted into the working channel of the commercial bronchoscope, and the biopsy needle can extend through the push rod.B) Established coordinate system of the catheter.Since the transition segment is inserted into the bronchoscope and its stiffness is greater than that of the steering segment, only the steering segment deforms under the actuation of tendons.C) The relationship between the actuation displacement and corresponding bending angle.As the actuation displacement increases, the bending angle of the steering segment increases linearly with a slope of 0.5 rad mm À1 .D) The workspace of the tendon-driven catheter along with the biopsy needle.

Figure 4
Figure 4. Force analysis of flexible biopsy robot.A) Experiment setting of force measurement at different bending angles.The force measuring system includes a force sensor connected with two sensor flanges, one of which is used to be fixed on the base, and another of which is used to install the guide slot.The tendon-driven is inserted into the guide slot along the inner curved groove while the biopsy needle extends and reaches the bottom.B) The ratio of the transmitted puncture force to the push force.As the bending angle increases, the ratio decreases and the rate of descent increases slightly.The main reason is the friction between the push rod and the catheter.C) Experiment setting of the maximum puncture force at different extension lengths.The tendon-driven catheter is inserted vertically into the guide slot, and the biopsy needle extends and reaches the bottom.By moving the catheter down, the extended length of the biopsy needle can be reduced.D) The maximum puncture force at different extension lengths.With the length increasing from 2 to 20 mm, the maximum puncture force reduces from 2.1N to 1.3N.In general, the puncture force for lung cancer is 0.264N, so the proposed biopsy robot could satisfy the requirement.

Figure 5 .
Figure 5.Control performance test of the flexible biopsy robot.A) Control strategy of the flexible biopsy robot.The operator inputs the control command, including the steering information of the tendon-driven catheter and the feed information of the flexible needle.Then, the command is converted to the actuation information of the steering control system and feed mechanism by inverse kinematics.Finally, the robot is controlled to reach the desired area and carry out biopsy operations.B) The actuation displacements of desired circle trajectory.C) The scatter plot of the actual trajectory and desired trajectory.The actual trajectory is basically consistent with the ideal trajectory.D) The error variation curves of the total error and projection errors on the X, Y, and Z axis.The error fluctuates within a small range.However, there are relatively large errors in some angles, which might source from the processing of hinge structure and assembling of tendons.E) The mean value and standard deviation of errors.The mean total error reaches 0.72 mm, showing good positioning accuracy.

Figure 6 .
Figure 6.Plane biopsy experiments.A) The three groups of biopsy experiments.The tendon-driven catheter is firstly controlled to point to the lesion, after which the biopsy needle is extended and inserted into the lesion.B) Force variation curves of the three groups of biopsy experiments.The variation of puncture force in repeated biopsy operations is roughly consistent, indicating that the proposed biopsy robot has high repeatability and stability.

Figure 7 .
Figure 7. In-vitro biopsy experiments.A) Experiment setting.There is a commercial bronchoscope with its host, an electric slide with its driver, a transparent bronchial phantom, and the proposed biopsy robot.The biopsy robot is inserted into the working channel of the commercial bronchoscope and aids the bronchoscope in performing biopsy operation by teleoperation.B) Biopsy experiment of endobronchial tumor in the left of phantom.C) Biopsy experiment of endobronchial tumor in the right of phantom.D) Biopsy experiment of extrabronchial tumor in the middle of phantom.E) Biopsy experiment of extrabronchial tumor in the right of phantom.F) Force variation curves of the above biopsy experiments.The average puncture time is about 1.2 s, and the maximum puncture force is below 0.5N.G) Distribution diagram of the maximum and mean value of puncture force in three repeated biopsy operations.The biopsy operation has high repeatability, and the maximum and mean values of different trials fluctuate within a narrow range.

Table 1 .
Comparison of advanced flexible biopsy robot in recent years.