Sperm cells navigate through thick fluids that would typically impede their movement. New research highlights how they achieve this by using unique properties of living matter.
According to a study led by Kenta Ishimoto from Kyoto University, sperm cells manage to swim not by conventional means but by exploiting certain behaviours of active systems. These tiny cells use their flagella, which are long, flexible tails, to generate movement through fluids that create significant resistance.
This study challenges the conventional understanding described by Newton’s third law, which states that for every action, there is an equal and opposite reaction. While this principle applies to everyday objects, sperm cells operate as active systems that inject energy into their movement.
The researchers found that sperm do not glide; instead, they rely on non-reversible strokes with their flagella. This is important because, at that tiny scale, inertia is nearly absent while viscosity is strong. In response, sperm cells use flagella powered by molecular motors to create waves that push them forward.
The study also introduces a concept called odd elasticity, where forces in active materials can respond in non-traditional ways. The findings could broaden scientists’ understanding of movement in living systems and may aid in developing small robots or materials mimicking natural motion. Future advancements may lead to practical applications in robotics and biotechnology as researchers continue to explore this field.
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