Nanomechanical sensors for direct and rapid characterization of sperm motility based on nanoscale vibrations

Infertility, whether of male or female origin, is a critical challenge facing the low birth rate and aging population throughout the world, and semen analysis is a cornerstone of the diagnostic evaluation of the male contribution to infertility. This means that tools which can characterize sperm properties in an effective manner are very much needed. The conventional approaches are essentially image-based, which have a limited value for analyzing sperm properties. Here, we show that an assay using nanomechanical sensors can detect sperm motility based on nanomotion. We use microcantilever sensors to directly characterize the mechanical response of the sperm based on the fluctuations of microcantilevers. We applied this methodology to sperms exposed to different chemical or physical agents. Real-time nanomechanical fluctuations showed that living sperms produced smaller fluctuations after treatment with inhibitory chemicals, and larger fluctuations after treatment with stimulatory chemicals. Our preliminary experiments suggest that the frequency of fluctuation is associated with sperm motility. This technique offers a brand-new perspective in the characterization of the sperm. By combining conventional measurements, reproductive medicine doctors and researchers should now be able to achieve unprecedented depth in the sperm properties.