Revealing stepping forces in sub-mg tiny insect walking

Measuring walking forces of small or tiny insects can help the comprehension of their locomotion principles. However, as their size and force are generally too small, walking forces of small insects in sub-mg mass have never been actually measured. In this work, a convenient multi-lens and jelly surface based shadow method was developed for simultaneous multiple walking forces measuring, ranged from nN to mN with a sensitivity of sub-nN/pixel under ambient conditions. Walking force of six legs of a 0.3 mg water treader was demonstrated. The obtained results disclosed a rapid and extending middle leg strategy of water treader in walking forward above a jelly surface. This method is cost-effective and high-resolution, which could be easily used in measuring other tiny forces.