When you blow away dust or crumb on the table, maybe you do not mind what happens in your lungs; when you are afraid of dangerous typhoon or volcano eruption, maybe you do not know that it's actually a sneeze of the earth; when you smell the sea breeze and stand by the shipboard to listen to the song of the screw propeller and bethink a cuttlefish escaping like a ghost, or feel glad to fly faster than a bird accompanying with the roar of the powerful jet engines, maybe you do not note that you are moving with the same principle; when you thank a river flows by your house and wonder where its heart is, I know that we always thank our hearts who are pumping blood day and night. In fact, in the dictionary of Isaac Newton, all these movements can be named as propjet (pressurized ejection), which a word almost reveal all meanings beyond the heart, lung, engine, rocket, water jet, air hammer, gun, atomizer, flamethrower, fanner, hair drier, paint-sprayer, needle and syringe injection, fiber spinning, ink-jet printing and so on.

 

Sir Isaac Newton at 46 (4 January 1643 – 31 March 1727)
by Godfrey Kneller in 1689

Lex III: Actioni contrariam semper et æqualem esse reactionem: sive corporum duorum actiones in se mutuo semper esse æquales et in partes contrarias dirigi.
Philosophiae Naturalis Principia Mathematica (published on July 5, 1687).  

Law III: All forces occur in pairs, and these two forces are equal in magnitude and opposite in direction. 
Mathematical Principles of Natural Philosophy (published on July 5, 1687)

 

Beyond all doubt, the well-known devices powered by or with the pressurized ejection have covered a variety of applications in our daily life, however, when the size is scaled down to nanoscale, the story is just little sentences. The physicists start from a tube structure like waterjet, which is a famous tool used in almost every industry and can cut almost any material from wood, plastics, stone, metal and alloys to ceramics.

In 2000, Uzi Landman's group reported a groundbreaking step to high speed nanojets [ 1(a) , 1(b) ]. The atomistic molecular dynamics simulations revealed the formation, stability, and breakup of nanojets. A steady-state flow (nanojet) with a higher velocity of 440 m/s could be achieved by pressurized injection of fluid propane (C3H8) through a 6-nm-diameter gold nozzle with 500 MPa and 150 K under nonwetting conditions. The average intact length of the nanojet (breakup length) is about 170 nm. 

In 2006, Manuel Melle-Franco and Francesco Zerbetto described their noticeable insights into high speed nanoejection [ 2 ]. It's a computational experiment on nanoscale hydrodynamics done with well-designed carbon nanotube (CNT) nozzles. The diameters of the used CNT inlets are 2.11-3.05 nm. For getting high speed ejection, they designed different zigzag-type CNT-junction nozzles featured with the same configuration including a long (n1, 0) CNT inlet of constant diameter and a convergent (n2, 0) outlet. The simulations of high-pressurized liquid argon (Ar, at 150 K) atoms confined inside CNT indicated that the cross-sectional patterns of the Ar flow showed in pure concentric layers and concentric layers with one or two central atomic lines, and importantly, the flow pressurized to 6000 atm could squirt through a (27, 0)|(17, 0) CNT-junction nozzle with velocity of 508 m/s. 

This velocity breaks a new record comparing with Landman's nanojet [ 1(a) , 1(b) ]. However, the pressurized ejection of liquid Ar through the CNT-based nozzle is typically composed of both clusters and isolated atoms. No real nanojet (steady-state flow) was observed in any simulation.  

Three experiment details should be noted. 

The first is the pressure range. In a view of experience, the higher the pressure is, the faster the ejected squirts. However, there are a roof and a floor. By pressurized the liquid Ar from 1000 to 7000 atm, interestingly, argon was found to be glassy state at 7000 atm, while the flowing rate was severely decreased under a pressure lower than 4000 atm. This theoretic finding hints that the ejecting velocity could have an upper limit for certain tube (diameter) and liquid (atom, molecular); 

Second, with effective pressures for high speed flow, the cross-sectional flux patterns shown in concentrical circles indicated the high-ordered arrangement of the flowing atoms, which should be very helpful to increase the jetting velocity. At the interface between Ar atoms and CNT wall, the simulations revealed the existence of the negative flux-low density but evident-to the direction of the main jetting flow, thus the friction; 

Third, note the high-ordered flow within the inlet tube, one may naturally expect that an axisymmetric inlet/outlet nozzle should jet faster than that of the asymmetric one. However, the simulations said no. For example, under the same pressure of 6000 atm and the same inlet/outlet diameter ratios but with different junction shapes, the (27, 0)|(17,0) asymmetric nozzle jetted liquid Ar with a velocity of 508 m/s, while for (27, 0)|(17,0) axisymmetric nozzle, only 419 m/s. I believe this result is reasonable because the interface friction may induce a radial velocity gradient, that is, maybe the flowing velocity in the central region of the tube is larger than the velocity near tube wall. Upon this postulation and with the designed inlet/outlet junction, the flow momentum reflected by the steeper wall of the asymmetric nozzle should be larger than that of the axisymmetric nozzle at the same time duration. This reflected momentum superimposed in the axis-directional flow thus causes much higher flow pressure at the nozzle tip, then a faster ejecting velocity comparing with the axisymmetric one.

Although there are different nanotubes suiting for tube inlet, it should be noted that the CNT is strong enough to be a good selection. This is not only because it can be easily fabricated today in high-controllable manner but also a zigzag configuration of C-C bonds shown in an excellent symmetry paralleling to the tube axis could provide an almost frictionless hydrophobic wall for much faster flowing especially for water [ 3, 4 ]. 

Certainly, the power of the presented CNT gun is not strong enough to cut a stone like waterjets. The force of the ejected liquid is similar in value to that of biomotors, 10-100 pN, while the output per second is of the order of picoliters [ 1(a) , 1(b) ]. However, the force should be big enough to cut single polymer chain.

Much should be theorized and calculated before fulfilling true applications. Of particular interests to this topic are microscopic events at the junction between the convergent nozzle and the inlet tube; and what happens at the interfaces where liquid/air meets vacuum, or importantly in true applications, air, another liquid or other substances such as cells, proteins or polymer chain. All of them strongly call for corroborating experiments.

Source: www.ScideaNews.com Credit: 2006 Scidea Sketch

I agree that the idea beyond these experiments deeply stimulates me. Certainly, from a more common sense point of view, mechanical nanolithography should prefer to a continuous jet, just like common waterjetting technology, which make it to be much effective in nanofabrication or nanomanipulation. As an experiment fellow, I wait for someone's computer to give a conclusive design for nanojet which can squirt a continuous liquid/gas flow with ultrahigh speed. Fortunately, beneficial with the works by Landman, Noworyta, Hinds and Zerbetto et al., maybe this answer need not rely on IBM's Deeper Blue. ♦

Nano Letters 6(5), 969–972 (2006). doi: 10.1021/nl060154y
Online: March 31, 2006 | Abs | Full | PDF | Supp.Info. | CrossRef  

Ejection Dynamics of a Simple Liquid from Individual Carbon Nanotube Nozzles
Manuel Melle-Franco†,‡ and Francesco Zerbetto‡ 

† Istituto Nazionale di Scienza e Tecnologia dei Materiali, Italy,
‡ and Dipartimento di Chimica “G. Ciamician”, Università di Bologna, V. F. Selmi 2, 40126, Bologna, Italy

Correspondence to: Manuel Melle-Franco; Francesco Zerbetto 

Link 

Uzi Landman
Francesco Zerbetto's research group
Nano Letters
Nanotube Modeler from JCrystal

Reference 

Citation