# Design and Development of a Flexible 3D-Printed Endoscopic Grasping Instrument
## 2 Materials and Methods
### Instrument Design
#### 2.1.1 Grasping Forceps  
The distal tip of the instrument is based on a single-action Johan grasper, which is specifically designed to allow for the gentle manipulation of fragile and histologically important tissue. Additionally, the grasping forceps are used for effectively placing sponges and other objects into leak cavities.  
To ensure that the instrument can properly grasp objects, a wide opening angle is necessary. However, achieving this wide opening angle can be challenging in the narrow space of the GI tract, which can be as narrow as 15-20 mm in the esophageal region. To balance the need for a wide opening angle with the narrow operational space, an opening angle of 65\({}^{\circ}\) was adopted. This angle allows the instrument to grasp objects securely while still being able to maneuver in the narrow spaces of the GI tract. The grasping forceps of the instrument have a total length of 22 mm and an outer diameter of 5 mm, making them compact and easy to use in endoscopic procedures.  
To ensure that they are effective at grasping objects, a minimal required grasping force of 10 N was adopted. This value was determined based on the average force required for grasping epithelial tissue (3.8 N) and muscle tissue (4.1 N), with maximum values of up to 9.7 N [34]. Overall, the design of the distal tip of the instrument is balanced to ensure that it can effectively grasp objects and handle tissue while still being maneuverable in the narrow spaces of the GI tract.  
\begin{table}
\begin{tabular}{c} \hline Instrument features \\ \hline Adequate length to reach the dedicated region, at least 40 cm. \\ A diameter of 5 mm for intraluminal application alongside an endoscope. \\ Sufficient strength for movement independent from the endoscope. \\ Safe introduction and maneuvering inside the GI tract, with smooth parts and surfaces. \\ Biocompatibility of the parts with contact with organs. \\ Affordable manufacturing through 3D printing and simple assembly. \\ Grasping forceps \\ \hline A smooth shape of the features that are in contact with the mucosal surfaces. \\ A minimum of 10 N grasping force to manipulate the tissue or a sponge. \\ Minimal length of non-grasping segments. The total length is less than 25 mm. \\ Jaw opening angle of at least 60\({}^{\circ}\). \\ At least 8 mm-long grasping area with a gentle wave-like profile. \\ Bending section \\ \hline Planar bending in both directions (left and right). \\ A high bending angle of at least 180\({}^{\circ}\) and a compact bending radius. \\ Adequate bending force for tissue and object manipulation of more than 5N. \\ Sufficient strength to withstand the loads introduced during maneuvering. \\ Flexible shaft \\ \hline A high degree of flexibility for safe introduction into the dedicated region. \\ Sufficient torsional stiffness to precisely transfer the hand inputs to the distal tip. \\ Enough stiffness during pushing when transporting objects (no buckling). \\ Control handle and tendon wires \\ \hline Convenient for single-hand use. \\ Star knob mechanism to control the bending of the distal tip, such as on endoscopes. \\ Push–pull motion for opening the grasping jaws, like on common biopsy forceps. \\ \hline \end{tabular}
\end{table}
Table 1: The list of requirements for the 3D-pEI and its elements.