Final Design

Endoscope Torque Applicator Final Design: EndoClamp

The final design solution is a silicone molded handle that has various inserts incorporated inside. The overall profile of the design was inspired by a screwdriver handle as the screwdriver is a tool optimized for torquing. Upon testing our handle, we found that our sponsors preferred to hold it backwards as it conforms to the shape of their thumbs better. As a result, our final design follows a reversed screwdriver handle profile. This silicone molded tool is able to give the doctors a larger grip radius which reduces the lateral force required to obtain the necessary torque. To prevent slippage between the lubed endoscope and the silicone handle, three different inserts were attached to the inner diameter of our device. The first two inserts, the scouring pad and the magic eraser sheet, have high coefficients of friction, which allow them to achieve no-slip condition. The third insert, the hexagonal shaped hard plastic, creates a jamming mechanism by applying a large normal force at an angle. All three inserts worked equally well. Therefore, two prototypes were created including all three inserts so doctors can choose which one they prefer.  

Performance

This design has a maximum thickness of 32mm compared to the 12.8mm thickness of the bare endoscope. With this thicker grip radius, we can get a mechanical advantage in achieving the necessary torque. The torque required in an endoscope procedure can reach up to 1.1Nm. With the 12.8mm thick endoscope we need to apply 171.8N of normal force to achieve this torque. However, with the added thickness with our tool we can reduce this required normal force to 68.7N, around a factor of 2.5. Other than the mechanical advantage this design gives the user, the thicker grip span allows the user's finger muscles to output the same force with less effort as it nears the optimal grip span of 50mm. 

Throughout the design process we decided to create an attribute table to help us compare the different iterations. Our final design was affected dexterity the least as it did not have an opening gap and provided a full wrap around the endoscope to maximize the grip surface. The scour pad so far soaked the least amount of lubricant compared to the towel and the magic sponge while providing great grip. The cost of manufacturing is not the lowest as it requires us to sew on the scour pad. The mechanical advantage is greater than that provided by the towel and provides amore ergonomic feel as it is not amorphous as the towel. The criterions for the attribute table are listed below:

1. Dexterity is defined as the degree to which our tool influences the physician’s overall ability to manipulate the endoscope. For instance, a tool that hinders the movement of the doctors will have a score of ‘Bad’ and vice versa. 

2. Accuracy is measured by the level of influence our tool has on the overall control of the endoscope. The magnification of the endoscope camera is about 43x, meaning slight movements have a large impact on the viewing angle and position. Thus, our tool must be able to provide feedback to the user to maximize accurate control. 

3. Sterility measures the cleanliness and maintenance of our product. For example if our device is to be reused and requires autoclave operation after every procedure, it will have a ‘Bad’ sterility score. On the other hand if the device can be disposed of, there is no incurred cleaning cost and will have a ‘Great’ sterility score.

4. Ergonomics measures the comfort and ease of use of our product. A towel, for instance, has a “Bad” score as it is not comfortable in a physician’s hand. It’s amorphous nature means the grip changes constantly throughout the procedure. If our design solution can maintain an ergonomic grip it will have a ‘Great’ score and if it cannot provide an ergonomic grip it will have a ‘Bad’ score.

5. Grip is measured by the required force to ensure non-slippage between the tool and the required normal force to torque the tool. Ideally our design will provide a mechanical advantage and obtain the same torque required to control the tool with less lateral force and have a ‘Great’ score.

6. Biocompatibility is a measure of the product’s ability to not harm the human body. In our case, the standards were the material data sheets. If the materials are not hazardous to the human body, it will have a ‘Great’ score.

7. Finally cost will be measured with price ranges. The ‘Great’ score will be under $20 and ‘Bad’ score will be over $100.

The outer profile of our handle has a maximum radius of 16 mm which decreases the lateral force required to torque the endoscope by a factor of 2.5. However, our solutions are definitely not perfect. The scouring pad and the magic eraser sheets, for instance, have the tendencies of absorbing the lubricant which slightly hinders the handle’s ability to slide across the endoscope. On the other hand, force application needs to be exact (from the top and the bottom) for the hexagonal inserts to prevent slippage. Despite the drawbacks of each design, we believe we were able to provide a cheap solution that not only meets the major requirements of the project, but also beats the current solution: the towel.