小肌肉發展為兒童視覺和手部動作之間的協調能力，以及手指及手腕精細的操作能力。若小肌肉發展遲緩，會影響兒童握筆、寫字等運用抓握技能的動作，進而影響生活或學習能力。因此Cartesian Diver為握力器再設計，改善傳統握力器尺寸僵化，且不易調整細微強度的缺點，加入趣味元素，為手部小肌肉發展遲緩兒童所設計的新型治療輔具。

Fine motor development is the skill that involves a refined use of the muscles controlling the hand, fingers, and thumb. If fine motor development delays, the child will fail to hold the pen, write and do every activity that needs to grasp or hold something. It will, even, affect life or learning ability. Therefore, Cartesian Diver improves the problem of the traditional handgrip, which can’t change the size and adjust the subtle strength. By adding interesting elements, it is designed as a new therapeutic auxiliary product for children with delay development of Fine Motor and helps them engage in the treatment gladly.