The manipulation of fluids in channels with dimensions of tens of micrometres--microfluidics--has emerged as a distinct new field. Microfluidics has the potential to influence subject areas from chemical synthesis and biological analysis to optics and information technology. But the field is still at an early stage of development. Even as the basic science and technological demonstrations develop, other problems must be addressed: choosing and focusing on initial applications, and developing strategies to complete the cycle of development, including commercialization. The solutions to these problems will require imagination and ingenuity.

The origins and the future of microfluidics

Microfabricated integrated circuits revolutionized computation by vastly reducing the space, labor, and time required for calculations. Microfluidic systems hold similar promise for the large-scale automation of chemistry and biology, suggesting the possibility of numerous experiments performed rapidly and in parallel, while consuming little reagent. While it is too early to tell whether such a vision will be realized, significant progress has been achieved, and various applications of significant scientific and practical interest have been developed. Here a review of the physics of small volumes (nanoliters) of fluids is presented, as parametrized by a series of dimensionless numbers expressing the relative importance of various physical phenomena. Specifically, this review explores the Reynolds number Re, addressing inertial effects; the Peclet number Pe, which concerns convective and diffusive transport; the capillary number Ca expressing the importance of interfacial tension; the Deborah, Weissenberg, and elasticity numbers De, Wi, and El, describing elastic effects due to deformable microstructural elements like polymers; the Grashof and Rayleigh numbers Gr and Ra, describing density-driven flows; and the Knudsen number, describing the importance of noncontinuum molecular effects. Furthermore, the long-range nature of viscous flows and the small device dimensions inherent in microfluidics mean that the influence of boundaries is typically significant. A variety of strategies have been developed to manipulate fluids by exploiting boundary effects; among these are electrokinetic effects, acoustic streaming, and fluid-structure interactions. The goal is to describe the physics behind the rich variety of fluid phenomena occurring on the nanoliter scale using simple scaling arguments, with the hopes of developing an intuitive sense for this occasionally counterintuitive world.

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Microfluidics: Fluid physics at the nanoliter scale

http://matera.fimmg.org/Linee%20guida/Linee%20guida%20nella%20nefrolitiasi%20(ing).pdf

Guidelines on urolithiasis

https://www.imop.gr/sites/default/files/giannakopoulos2.pdf

2007 Guideline for the Management of Ureteral Calculi

Purpose: To investigate the effect of pelvic lymph node dissection and radical cystectomy for transitional cell cancer of the bladder on recurrence-free and overall survival, pelvic recurrences, and metastatic patterns in a homogeneous group. Patients and Methods: A consecutive series of patients undergoing pelvic lymphadenectomy and radical cystectomy between 1985 and 2000 was analyzed. All patients were staged N0, M0 preoperatively, and no patient received neoadjuvant radio/chemotherapy. Pathologic characteristics based on the 1997 tumor-node-metastasis system, recurrence-free/overall survival, and metastatic patterns were determined. Results: Five hundred seven patients (age 66 ± 12 years) with a mean follow-up time of 45 months (range, 0.1 to 176 months) were analyzed. Five-year recurrence-free and overall survival were, respectively, 73% and 62% for patients with organ-confined, lymph node-negative tumors (n = 217; ≤ pT2, pN0) and 56% and 49% for non-organ-confined, lymph node-negative tumors (n = 16...

Radical Cystectomy for Bladder Cancer Today--A Homogeneous Series Without Neoadjuvant Therapy

This paper describes a self-contained integrated microfluidic system that can separate motile sperm from small samples that are difficult to handle using conventional sperm-sorting techniques. The device isolates motile sperm from nonmotile sperm and other cellular debris, based on the ability of motile sperm to cross streamlines in a laminar fluid stream. The device is small, simple, and disposable yet is an integrated system complete with sample inlets, outlets, sorting channel, and a novel passively driven pumping system that provides a steady flow of liquid; it requires no external power source or controls. The device fulfills a need in clinical settings where small amounts of sperm need to be sorted. It also opens the way for convenient bioassays based on sperm motility including at-home motile sperm tests.

Passively driven integrated microfluidic system for separation of motile sperm

Complications of ureteroscopy: analysis of predictive factors

A microfluidic device was designed with two parallel laminar flow channels where non-motile spermatozoa and debris would flow along their initial streamlines and exit one outlet, whereas motile spermatozoa had an opportunity to swim into a parallel stream and exit a separate outlet. Motile sperm samples were prepared with density gradient separation (n = 5). Sperm motility was assessed the following day after exposing aliquots to polydimethylsiloxane (PDMS) used to construct the device. There was no difference in sperm motility when compared with unexposed aliquots (P > 0.05). Unprocessed semen samples (n = 10) were placed in wider channels and sperm motility and strict morphology were assessed from sorted outlets. Sperm motility increased from 44 +/- 4.5% to 98 +/- 0.4% (P < 0.05) and morphology increased from 10 +/- 1.05% to 22 +/- 3.3% (P < 0.05) following processing. Finally, density gradient prepared samples (n = 6) containing 5 x 10(6) motile spermatozoa/ml and 50 x 10(6) round immature germ cells/ml were sorted and assessed in a similar fashion. The ratio of motile spermatozoa to round immature germ cells in the wide inlet (1:10) was significantly improved in the thin outlet (33:1) (P < 0.05). This microfluidic device provides a novel method for isolating motile, morphologically normal spermatozoa from semen samples without centrifugation. This technology may prove useful in isolating motile spermatozoa from oligozoospermic samples, even with high amounts of non-motile gamete and/or non-gamete cell contamination. A movie sequence showing streaming and sorting of spermatozoa may be purchased for viewing on the internet at www.rbmonline.com/Article/847 (free to web subscribers).

https://www.rbmojournal.com/article/S1472-6483(10)61732-4/pdf

Timothy G. Schuster

Papers

Passively driven integrated microfluidic system for separation of motile sperm

Complications of ureteroscopy: analysis of predictive factors

Isolation of motile spermatozoa from semen samples using microfluidics

Ureteroscopy For The Treatment Of Urolithiasis In Children

Ureteroscopic Treatment of Lower Pole Calculi: Comparison of Lithotripsy In Situ and After Displacement