# High-Speed Cell Assembly with Piezo-Driven Two-Finger Microhand
## 5 Discussion  
For any cell manipulation, the extent of damage to the cells is a crucial concern. In this study, cell manipulation was performed using a two-finger microhand, which involves a mechanical contact microoperation. The end-effector is made of capillary glass, exhibiting good biocompatibility, and the cell deformation after grasping is controlled within 2 um to  
Figure 7: Assembly process for character ‘T’.  
minimize damage to the cells. Studies related to cell micromanipulations indicated that the damage caused by this single operation on cells was minimal and fell within an acceptable range. However, as the number of operations on the same cell increased, the impact on cell viability became more pronounced [42; 43]. This paper only involves a single grasping and releasing of each target cell, so although there is inevitably some damage caused by contact operations, the extent of the damage is relatively low.  
Although the micromanipulation robot system can currently accomplish the assembly of cell arrays, it still has several limitations. Firstly, the grasping and releasing of cells cannot achieve a 100% success rate. Grasping cells is much more challenging than microspheres due to variations in cell sizes, more complex morphologies, and unpredictable deformations that occur upon grasping. In addition, the adhesive forces of cells occasionally result in attachment at different positions of the end-effector, making detachment difficult. Secondly, there is an issue of disturbance in micromanipulations within a liquid environment. Manipulating cells in a liquid causes the movement of the end-effector to induce microflows, which is significantly harmful for high-precision operations. While compensation can enhance the placement accuracy for individual cells, continuous operations on multiple cells will cause the previously placed cells to shift due to the microflows induced by the subsequent movement of the end-effector. Thirdly, cell assembly is limited to a two-dimensional plane. Tissue engineering requires the construction of cells into three-dimensional structures. We have not yet attempted 3D cell assembly, which represents an important future research direction.  
In the future, we plan to optimize our study from the following directions. Firstly, the microhand structure design can be optimized. Currently, manipulations on micro-objects in the range of tens of micrometers are easily achievable, but manipulations on targets at the level of hundreds of micrometers are challenging due to workspace limitations, which is a major drawback of parallel mechanisms. Therefore, in the future, we consider designing new serial-parallel hybrid structures, such as connecting two 3-PRR modules in series to introduce the advantage of a larger workspace. Secondly, the precision of micromanipulations needs to be further improved. This involves using higher-precision piezoelectric actuators, enhancing the accuracy of sensors, and optimizing controller algorithms. The next goal is to achieve a micromanipulation precision of 0.1 \(\upmu\)m. Thirdly, we aim to increase the efficiency of automated operations. Enhancing target detection speed can be achieved through improvements in visual recognition algorithms. For instance, employing convolutional neural network (CNN)-based algorithms can strengthen robustness in identifying targets in complex scenes. Additionally, selecting better hardware configurations can also improve the running speed of algorithms.