An Ultrasonically Actuated Silicon-Microprobe-Based Testicular Tubule Assay

Microdissection testicular sperm extraction (TESE) is an invasive surgical procedure in which sparsely located healthy larger diameter tubules carrying viable spermatazoa are identified by visual examination of the seminiferous tubules of the infertile testis under a microscope, and biopsies of regions of interest are performed. In this paper, we report on microfabricated silicon microprobes integrated with an ultrasonic horn actuator and strain gauges for microdissection probe-TESE (MP-TESE) surgery. The microprobes, with axial-force-sensitive polysilicon strain gauges, have high force sensitivity (-0.4 V/N). The probes were used to detect the boundaries between seminiferous tubules, thus enabling identification of individual tubule diameters. Insertion experiments were performed on rat testis tissue, and by monitoring the tubule puncture in the recorded force, we were able to estimate the average diameter ~ 41.2 plusmn 1.6 mum of the sperm-carrying tubules in samples. We have also demonstrated the ability to sense the existence of larger tubules embedded in a mess of thinner tubules, using an analytically calculated expression for the distribution of sizes measured by the microprobe. This information is important in MP-TESE to distinguish tubules with and without fertile sperm, potentially eliminating the large incision currently required for optical spermatazoa localization.