For several centuries fluid dynamics studies have relied upon the assumption that when a liquid flows over a solid surface, the liquid molecules adjacent to the solid are stationary relative to the solid. This no-slip boundary condition (BC) has been applied successfully to model many macroscopic experiments, but has no microscopic justification. In recent years there has been an increased interest in determining the appropriate BCs for the flow of Newtonian liquids in confined geometries, partly due to exciting developments in the fields of microfluidic and microelectromechanical devices and partly because new and more sophisticated measurement techniques are now available. An increasing number of research groups now dedicate great attention to the study of the flow of liquids at solid interfaces, and as a result a large number of experimental, computational and theoretical studies have appeared in the literature. We provide here a review of experimental studies regarding the phenomenon of slip of Newtonian liquids at solid interfaces. We dedicate particular attention to the effects that factors such as surface roughness, wettability and the presence of gaseous layers might have on the measured interfacial slip. We also discuss how future studies might improve our understanding of hydrodynamic BCs and enable us to actively control liquid slip.

https://iopscience.iop.org/article/10.1088/0034-4885/68/12/R05/pdf

Boundary slip in Newtonian liquids: a review of experimental studies

A series of experiments is presented which demonstrate significant drag reduction for the laminar flow of water through microchannels using hydrophobic surfaces with well-defined micron-sized surface roughness. These ultrahydrophobic surfaces are fabricated from silicon wafers using photolithography and are designed to incorporate precise patterns of microposts and microridges which are made hydrophobic through a chemical reaction with an organosilane. An experimental flow cell is used to measure the pressure drop as a function of the flow rate for a series of microchannel geometries and ultrahydrophobic surface designs. Pressure drop reductions up to 40% and apparent slip lengths larger than 20 μm are obtained using ultrahydrophobic surfaces. No drag reduction is observed for smooth hydrophobic surfaces. A confocal surface metrology system was used to measure the deflection of an air–water interface that is formed between microposts and supported by surface tension. This shear-free interface reduces the ...

http://www.ecs.umass.edu/mie/faculty/rothstein/pub_files/PhysFluids2004v16p4635_4643.pdf

Laminar drag reduction in microchannels using ultrahydrophobic surfaces

While many recent studies have confirmed the existence of liquid slip over certain solid surfaces, there has not been a deliberate effort to design and fabricate a surface that would maximize the slip under practical conditions. Here, we have engineered a nanostructured superhydrophobic surface that minimizes the liquid-solid contact area so that the liquid flows predominantly over a layer of air. Measured through a cone-and-plate rheometer system, the surface has demonstrated dramatic slip effects: a slip length of approximately 20 microm for water flow and approximately 50 microm for 30 wt % glycerin. The essential geometrical characteristics lie with the nanoposts populated on the surface: tall and slender (i.e., needlelike) profile and submicron periodicity (i.e., pitch).

/pdf/large-slip-of-aqueous-liquid-flow-over-a-nanoengineered-3d3eew5gdl.pdf

Large Slip of Aqueous Liquid Flow over a Nanoengineered Superhydrophobic Surface

The no-slip boundary condition at a solid-liquid interface is at the center of our understanding of fluid mechanics. However, this condition is an assumption that cannot be derived from first principles and could, in theory, be violated. In this chapter, we present a review of recent experimental, numerical and theoretical investigations on the subject. The physical picture that emerges is that of a complex behavior at a liquid/solid interface, involving an interplay of many physico-chemical parameters, including wetting, shear rate, pressure, surface charge, surface roughness, impurities and dissolved gas.

/pdf/microfluidics-the-no-slip-boundary-condition-4yg4du3ofj.pdf

Microfluidics: The no-slip boundary condition

The discovery of enhanced magnetoresistance and oscillatory interlayer exchange coupling in transition metal multilayers just over a decade ago has enabled the development of new classes of magnetically engineered magnetic thin-film materials suitable for advanced magnetic sensors and magnetic random access memories. Magnetic sensors based on spin-valve giant magnetoresistive (GMR) sandwiches with artificial antiferromagnetic reference layers have resulted in enormous increases in the storage capacity of magnetic hard disk drives. The unique properties of magnetic tunnel junction (MTJ) devices has led to the development of an advanced high performance nonvolatile magnet random access memory with density approaching that of dynamic random-access memory (RAM) and read-write speeds comparable to static RAM. Both GMR and MTJ devices are examples of spintronic materials in which the flow of spin-polarized electrons is manipulated by controlling, via magnetic fields, the orientation of magnetic moments in inhomogeneous magnetic thin film systems. More complex devices, including three-terminal hot electron magnetic tunnel transistors, suggest that there are many other applications of spintronic materials.

Magnetically engineered spintronic sensors and memory

Background
The aim of this study was to evaluate whether 3-dimensional (3D) simulation software is applicable to and useful for anatomic liver segmentectomy and subsegmentectomy.
Methods
A prospective study of 83 consecutive patients who underwent anatomic segmentectomy or subsegmentectomy using the puncture method was performed. All patients underwent 3D simulation analysis (SA) preoperatively for planning operative procedures. The clinical information acquired by 3D SA and the consistency of virtual and real hepatectomy were evaluated.
Results
The time needed for completing 3D SA was 18.3 ± .7 minutes. Three-dimensional SA proposed resection of multiple segments or subsegments in 29 patients (35%). It also helped complement the resection line in 26 patients (31%) who lacked a bold staining area on the liver surface. The volume of segment or subsegment calculated by 3D SA was correlated with the actual resected specimen (R2 = .9942, P < .01). The bordering hepatic veins were clearly exposed in 71 patients (86%), in accordance with completed drawings by 3D SA.
Conclusions
Three-dimensional SA showed accurate completed drawings and assisted liver surgeons in planning and executing anatomic segmentectomy and subsegmentectomy.

http://lib.ajaums.ac.ir/booklist/1-s2.0-S0002961013002912-main.pdf

Planning of anatomical liver segmentectomy and subsegmentectomy with 3-dimensional simulation software

The influence of the mixed inert gas species for plasma oxidization process of a metallic Al layer on the tunnel magnetoresistance (TMR) was investigated for a magnetic tunnel junction (MTJ), Ta 50 A/Cu 200 A/Ta 200 A/Ni–Fe 50 A/Cu 50 A/Mn75Ir25 100 A/Co70Fe30 25 A/Al–O/Co70Fe30 25 A/Ni–Fe 100 A/Cu 200 A/Ta 50 A Using Kr–O2 plasma, a 588% of TMR ratio was obtained at room temperature after annealing the junction at 300 °C, while the achieved TMR ratio of the MTJ fabricated with usual Ar–O2 plasma remained 486% A faster oxidization rate of the Al layer by using Kr–O2 plasma is a possible cause to prevent the over oxidization of the Al layer, which depolarizes the surface of the underlaid ferromagnetic electrode, and to realize a large magnetoresistance

60% magnetoresistance at room temperature in Co–Fe/Al–O/Co–Fe tunnel junctions oxidized with Kr–O2 plasma

Preoperative chemotherapy containing oxaliplatin (FOLFOX) or irinotecan (FOLFIRI) causes histological liver injury and increases postoperative morbidity and mortality in patients with colorectal liver metastasis (CRLM). However, information on the aggravation of liver function and its reversibility is scarce. A total of 55 patients who underwent a hepatectomy after receiving FOLFOX and/or FOLFIRI were included in the present study. Indocyanine green tests were repeatedly performed before hepatectomy for monitoring the change of hepatic functional reserve. A significant decrement in the ICG R15 value was observed at 2–4 weeks (12.9%, P = .04), 4–8 weeks (11.4%, P = .01), and 8 or more weeks (11.1%, P = .006) after the last chemotherapy, compared with results documented within 2 weeks (16.8%). However, no significant change was observed among the values obtained at 2–4 weeks, 4–8 weeks, and 8 or more weeks. The individual ICG R15 values at the beginning and end of the cessation period also improved from 17.7% to 11.6% (P = .001). Histological liver injury was associated with larger amounts of operative blood loss but not with morbidity. Neither liver failure nor mortality occurred in the present series. The hepatic functional reserve, represented by the ICG R15 value, improves during the period after chemotherapy cessation. The present study suggests that chemotherapy cessation for at least 2–4 weeks enables an improvement in the hepatic functional reserve, especially among patients with an abnormal ICG R15 value (> 10%) who have received 6 or more cycles of FOLFOX and/or FOLFIRI.

Recovery of liver function after the cessation of preoperative chemotherapy for colorectal liver metastasis.

Some microtextured surfaces strongly repel water. In particular, surfaces with contact angle (CA) higher than 150° are called superhydrophobic surfaces and many studies to obtain such surfaces have been reported. However, none of them could be a guide to achieve superhydrophobicity and the thermodynamic mechanisms are not well understood. In this study, two types of 3-D models—pillar-textured surfaces and cavity surfaces—were selected and thermodynamically analyzed focusing on the surface free energy. By calculations, equilibrium CA, free energy wall (FEW), and CA hysteresis are obtained. Based on these calculations, the factors to determine the sliding angle are indicated. Additionally, based on these results, one example of the optimal geometry for superhydrophobic surfaces is proposed.

3-D thermodynamic analysis of superhydrophobic surfaces.

The torque and velocity profile of a flow between two coaxial cylinders with a highly water-repellent wall were measured experimentally. Two kinds of highly repellent wall were tested to clarify the surface condition effect of the cylinder on laminar drag reduction with fluid slip. The results of torque measurement showed that laminar drag reduction does not occur for a highly water-repellent wall with no fine grooves at the wall surface. Fluid slip of Newtonian fluids was clarified by measuring the velocity profile close to the highly water-repellent wall in a Couette flow by a tracer method for flow visualization. The maximum slip velocity is less than 20% of the wall velocity of the rotating inner cylinder. The result of the drag reduction ratio for the torque was calculated by applying to the slip velocity, and agrees with the experimental result quantitatively. Consequently, the gas trapped in the fine grooves plays an important role in laminar drag reduction with respect to fluid slip. From the flow visualization of laminar Taylor–Couette flow, the intervals of Taylor cells become slightly irregular in the case of the cylinder with a highly water-repellent wall. The calculation result for the Taylor cell applying the fluid slip boundary condition agrees with the experimental result.

Satoshi Ogata

Papers

Planning of anatomical liver segmentectomy and subsegmentectomy with 3-dimensional simulation software

60% magnetoresistance at room temperature in Co–Fe/Al–O/Co–Fe tunnel junctions oxidized with Kr–O2 plasma

Recovery of liver function after the cessation of preoperative chemotherapy for colorectal liver metastasis.

3-D thermodynamic analysis of superhydrophobic surfaces.

Flow between two coaxial rotating cylinders with a highly water‐repellent wall