Many plants and animals have evolved intriguing wetting properties; these special abilities result from the unique micro- and nano-scale structural features on their surfaces1,2,3,4,5,6. For example, certain beetles living in the Namib Desert can collect water from the fog on their backs4. Spider silks can also harvest water from humid air using the periodic spindle-knots and joints5. The gradient of surface-free energy7,8 and gradient of Laplace pressure9,10,11 are believed to be the primary driving forces behind these phenomena. Many members of the Cactaceae family can survive in highly arid deserts12. In addition to the adaptive characteristics that minimise water loss13,14, some species appear to use fog as an additional water supply by using spines15,16,17 that fulfil multiple functions14,15,18. Despite the considerable amount of research that has been performed on the Cactaceae family, the process of fog harvesting using spines is still poorly understood.

In situ observation of directional water collection on a horizontal spine of the cactus (Opuntia microdasys). The water drops move from the tip to the base side of the spine. (MOV 298 kb)

Morita M., Koga T., Otsuka H. & Takahara A. Macroscopic-wetting anisotropy on the line-patterned surface of fluoroalkylsilane monolayers. Langmuir 21, 911–918 (2005).

In fact, each geometry has been designed and studied to control chip formation in precise applications. These applications vary in terms of material groups and type of machining: finishing, medium removal or roughing. In our case we have used the letters PF as an example, where P identifies the family of steels while F indicates the finishing operation. So in this case the chipbreaker geometry is suitable for finishing operations on steels.

In situ observation of fog collection on two adjacent spines of the cactus (Opuntia microdasys). The water drops are collected on single spines at first and are quickly absorbed once they contact with the trichomes surrounding the base of the spines. (MOV 1830 kb)

Millinginsertspecification

To conclude, we can say that knowing the insert nomenclature you will have identified every dimensional and constructional aspect of your insert. Only the geometry of the chip breaker will be excluded from ISO, since it is not included in the standard and is defined differently from builder to builder.

The length of the cutting edge will influence the removal capacity of the insert depending on the thickness. This thickness is determined by the second pair of numbers, which we see here as 04. This pair indicates a thickness of 4.76 mm from the inch-millimetre conversion. Other cutting edge lengths will have different thicknesses.

Here we demonstrate that the cactus O. microdasys, which originates from the Chihuahua Desert, has an integrated multi-functional system that facilitates efficient fog collection. This unique fog collection system can be attributed to the integration of its multi-level surface structures.

In addition to the aligned grooves, the oriented barbs reduce the drop’s ability to spread or move towards the tip side with the barbs, facilitating movement towards the base side lacking barbs. With an anisotropic CAH35, a water drop on a surface with asymmetrical structures has a preferred direction to spread or move2,21,22. Because the barbs orient in the direction towards the spine’s base (Fig. 1e), the water drops prefer to spread and move along the oriented direction of the barbs. This CAH difference further aids the growth and movement of the water drops to the base side of the spine under deposition.

Loik M. E. The effect of cactus spines on light interception and Photosystem II for three sympatric species of Opuntia from the Mojave Desert. Physiol. Plant 134, 87–98 (2008).

We thank the National Research Fund for Fundamental Key Projects (grant nos. 2013CB933000, 2009CB930404, 2010CB934700, 2011CB935700 and 2012CB933200), the National Natural Science Foundation (grant nos. 20974113, 21071148, 20920102036, 21121001 and 91127025) and the Key Research Programme of the Chinese Academy of Sciences (grant no. KJZD-EW-M01) for providing financial support. Dr Xi Yao from Jilin University, Changchun, Dr Bin Su and Dr Kan Li from the Institute of Chemistry, Beijing and Dr Jiexing Du and Dr Peng Guo from Beijing University of Aeronautics and Astronautics are acknowledged for their helpful discussions and technical support.

Extrand C. W. Retention forces of a liquid slug in a rough capillary tube with symmetric or asymmetric features. Langmuir 23, 1867–1871 (2007).

Collett J. L., Herckes P., Youngster S. & Lee T. Processing of atmospheric organic matter by California radiation fogs. Atmos. Res. 87, 232–241 (2008).

Schill R., Barthlott W. & Ehler. N. Cactus spines under the electron scanning microscope. Cactus Succulent J. XLV, 175–185 (1973).

Robinson H. Scanning electron microscope studies of the spines and glochids of the Opuntioideae (Cactaceae). Amer. J. Bot. 61, 278–283 (1974).

where r is the roughness factor defined as the ratio of the actual surface area to the geometric projected area of a rough surface, and θ and θw are the intrinsic and apparent contact angles, respectively. The gradient of roughness generates a gradient of wettability, (that is, a gradient of surface-free energy)28,29,30. For the surface of the cactus spines covered with vegetable wax19, the tip is rougher and more hydrophobic; whereas the base is less rough and less hydrophobic (see Supplementary Fig. S6). In other words, the tip of the spine has a lower surface-free energy than the base. This gradient of the surface-free energy produces a driving force F, driving the water drops collected on the tip directionally towards the base5 as described as follows:

This work is licensed under a Creative Commons Attribution-NonCommercial-Share Alike 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/

To be precise in turning operations, it is measured in mm per revolution, i.e. the distance covered by the tip of the insert at each turn of the workpiece. The values, as we shall see, range from a few hundredths of a millimetre to a few millimetres in the rarest cases. A small nose radius implies small feeds; large nose radius allows large feeds to be used.

The nose radius influences a very important cutting data, the feed rate. We will dedicate a specific lesson to the feed rate, but for the moment let’s say that it identifies the speed at which the tool carries out its removal path.

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Sun C., Zhao X.-W., Han Y.-H. & Gu Z.-Z. Control of water droplet motion by alteration of roughness gradient on silicon wafer by laser surface treatment. Thin Solid Films 516, 4059–4063 (2008).

Yoshimitsu Z., Nakajima A., Watanabe T. & Hashimoto K. Effects of surface structure on the hydrophobicity and sliding behavior of water droplets. Langmuir 18, 5818–5822 (2002).

The last parameter to be considered is the pair of letters which in this case is PF. The field n°12 is left empty by the ISO standard for the insert builder who uses it to indicate the geometry of the chipbreaker drawn on the insert face. This geometry is fundamental for a correct use of the insert.

The aligned grooves can also generate an anisotropic contact angle hysteresis (CAH)31,32 in the direction parallel or perpendicular to the grooves, enhancing the directional movement of the water drops along the grooves on the barbs and spines (See Supplementary Fig. S8). Specifically, a water drop moves more readily in the direction that is parallel to the aligned structures than in other directions33. The drop has a continuous, three-phase contact line along the grooves that reduces the energy barrier and therefore facilitates the spreading and moving of the drop34. Without a gradient in width along the cactus spine, the submicrogrooves further enhance this anisotropic CAH (Supplementary Fig. S3), facilitating the directional movement of the water drops along the barbs and the spines.

Gau H., Herminghaus S., Lenz P. & Lipowsky R. Liquid morphologies on structured surfaces: From microchannels to microchips. Science 283, 46–49 (1999).

Bai H. et al. Direction controlled driving of tiny water drops on bioinspired artificial spider silks. Adv. Mater. 22, 5521–5525 (2010).

Now that we have seen some examples of coding that have been more or less used, let’s say a few words about the choice of the insert nose radius.

The cactus (Opuntia microdasys) was purchased from the Chinese Academy of Agricultural Sciences, Beijing, China. The clusters of the spines and trichomes, and the single spine were carefully selected and fixed on the sample frame.

where θA and θR are the advancing and receding contact angles of water drops on the middle of the spine, respectively, and dl is the integral variable along the length of the middle of the spine from the region near the tip (ltip) to the region near the base (lbase). The roughness arising from the microgrooves on the cactus spine enhances the gradient of the Laplace pressure (see Supplementary Fig. S7), contributing to the movement of the water drops along the cactus spines.

The first pair equals to 16 mm: this is the length of the insert side. With the triangular shape there are also other lengths, for example 11 or 22mm. The side dimension is 16 mm, which corresponds to an inscribed circle of 9.525 mm. This number was used to calculate the numerical value of tolerance M.

Norgaard T. & Dacke M. Fog-basking behaviour and water collection efficiency in Namib Desert Darkling beetles. Front. Zool. 7, 23 (2010).

Ogburn R. M. & Edwards E. J. Anatomical variation in Cactaceae and relatives: trait lability and evolutionary innovation. Am. J. Bot. 96, 391–408 (2009).

Good morning, in today’s additional info I would like to give you some examples of ISO nomenclature in order to help you become familiar with the names of the inserts but above all with the coding itself. It is very important for anyone working in machining to know and understand the insert and its ISO nomenclature. In the lesson we saw three examples of ISO nomenclature when we asked Paolo the question; we saw an RNMG, a WNMG and a WCGT. Apart from the first letter which distinguishes the form, the first two inserts have identical parameters 2, 3 and 4 and exactly _NMG. This is also the most common ISO nomenclature for double-sided tools with chipbreaker geometry; these, as we shall see in the lesson on side rake angles, are fitted to negative tools. While the third case of the exercise posed to Paolo has parameters 2, 3 and 4 equal, _CGT. The latter is the most common ISO nomenclature for single-sided inserts. Let’s look at a new case very similar to the one seen in the lesson. TNMG 160404 PF So let’s go in order and start with the letter T. Insert shape As we said in the lesson, the first letter identifies the shape of the insert; in this case is triangular with an angle between the cutting edges of 60 degrees. Side rake angle The second letter determines the value of the insert clearance angle. N for the ISO is an angle of 0 degrees so our insert can be a double-sided insert, so it can be used on both sides. It should also be noted at this point that the fixing of the insert on the tool is of the lever type and therefore a strong fixing. Tolerance Then we come to the third letter M. M establishes the tolerance class that is given with respect to the circle inscribed in the geometric figure of the insert. In this case is a circle with a diameter of 9.525. This value, the diameter of the inscribed circle, is taken from the insert size table, which we will see with parameter 5 relating to the size. Class M is a tolerance that is not very precise but nevertheless one of the most widely used in turning and which corresponds exactly to ±0.05 mm. Insert type Let’s now move on to G, the last letter of the alphanumeric code; it indicates that our insert has a chip-breaking geometry on the face of the cutting edge, suitable for controlling and breaking the chips that will be formed during machining. Obviously, the geometry is studied and carried out on both faces of the insert. Moreover it has some characteristics in relation to the material to be machined and the operation to be carried out, i.e. finishing or roughing of a component. After the letters we now move on to the numbers, which as we have seen are taken in pairs. Size The first pair equals to 16 mm: this is the length of the insert side. With the triangular shape there are also other lengths, for example 11 or 22mm. The side dimension is 16 mm, which corresponds to an inscribed circle of 9.525 mm. This number was used to calculate the numerical value of tolerance M. Thickness The length of the cutting edge will influence the removal capacity of the insert depending on the thickness. This thickness is determined by the second pair of numbers, which we see here as 04. This pair indicates a thickness of 4.76 mm from the inch-millimetre conversion. Other cutting edge lengths will have different thicknesses. Please note that thickness is very important as it constitutes the resistant section of the cutting edge. The greater the thickness, the greater the strength of our insert. Sometimes, in order to increase the life of the cutting edge with the same chip volume, i.e. with the same working data, it is sufficient to oversize the length of the cutting edge. This will provide a higher thickness, which will guarantee high resistance to the cutting forces and temperatures that will develop during turning. Nose radius The third and last pair of numbers in this part is 04, which in tenths of a millimetre is the value of the nose radius. The nose radius influences the strength of the cutting edge. In fact, a radius such as in this case 0.4 mm cannot be used for heavy roughing operations where, on the contrary, a larger radius will be useful, for example 1.2 mm. Therefore, this value of 0.4 mm also means that the field of application for this insert will be finishing or other light operations. The last parameter to be considered is the pair of letters which in this case is PF. The field n°12 is left empty by the ISO standard for the insert builder who uses it to indicate the geometry of the chipbreaker drawn on the insert face. This geometry is fundamental for a correct use of the insert. In fact, each geometry has been designed and studied to control chip formation in precise applications. These applications vary in terms of material groups and type of machining: finishing, medium removal or roughing. In our case we have used the letters PF as an example, where P identifies the family of steels while F indicates the finishing operation. So in this case the chipbreaker geometry is suitable for finishing operations on steels. To conclude, we can say that knowing the insert nomenclature you will have identified every dimensional and constructional aspect of your insert. Only the geometry of the chip breaker will be excluded from ISO, since it is not included in the standard and is defined differently from builder to builder. TPGN 110308 This second example of an insert is not very common, but it is shown here for educational purposes. It is a turning and finishing insert that is assembled on boring bars for internal machining or on adjustable boring cartridges. The insert has a flat face and its fixing system is of the micro-fused bracket type. T = triangular-shaped insert P = 11 degree insert clearance angle G = tolerance class in this case of accuracy N = insert with a flat face without chipbreaker geometry 11 in millimetres is the length of the side of the insert 03 indicates the thickness S of the product, here set at 3.17 millimetres 08 in tenths of a millimetre is the value of the nose radius which in this case is 0.8mm   SOEX 120508 Again, this is an uncommon insert but ideal for understanding the ISO nomenclature. It is a screw-clamp type insert with a countersunk slot, used in finishing or semi-finishing operations on internal machining tools such as boring bars. Sometimes for some builders it is also used in drilling on mechanically clamped drills. S = square-shaped insert O = 8 degree insert clearance angle E = tolerance class on inscribed circle. Precision insert (inscribed circle equal to mm 12,70) X = special non ISO standard (this letter only) with chipbreaker geometry 12 = in mm insert side length mm 12 05 = thickness value, in this case is 5.16mm 08 = in tenths of a millimetre the value of the nose radius, in this case 0.8mm   CHOICE OF NOSE RADIUS Now that we have seen some examples of coding that have been more or less used, let’s say a few words about the choice of the insert nose radius. The nose radius influences a very important cutting data, the feed rate. We will dedicate a specific lesson to the feed rate, but for the moment let’s say that it identifies the speed at which the tool carries out its removal path.   To be precise in turning operations, it is measured in mm per revolution, i.e. the distance covered by the tip of the insert at each turn of the workpiece. The values, as we shall see, range from a few hundredths of a millimetre to a few millimetres in the rarest cases. A small nose radius implies small feeds; large nose radius allows large feeds to be used. When choosing the radius of the point we must take into account various aspects which I will list below: In finishing operations the nose radius influences the internal corner radius that will remain on the workpiece profile. So it is usually the design or construction guidelines of the workpiece that define the maximum insert corner radius. Usually the most commonly used radius that takes this into account is 0.4mm. Obviously, if your workpiece has no internal corner  radius or the value of the internal radius left on the workpiece is irrelevant, the choice of insert radius will be made on the basis of the following considerations; Larger nose radius, stronger inserts; With large nose radius, high feed rates are possible (more on this in the feed rate lesson); Adopting large nose radius (all other cutting parameters being equal) will develop more radial forces, which are one of the primary sources of vibration. This last aspect is the one that puts a limit on the maximum nose radius that can be used. We will return to this subject in future lessons.

TurninginsertIdentification chart

The second letter determines the value of the insert clearance angle. N for the ISO is an angle of 0 degrees so our insert can be a double-sided insert, so it can be used on both sides. It should also be noted at this point that the fixing of the insert on the tool is of the lever type and therefore a strong fixing.

Schemenauer R. S. & Cereceda P. A proposed standard fog collector for use in high-elevation regions. J. Appl. Meteor 33, 1313–1322 (1994).

Daniel S., Chaudhury M. K. & Chen J. C. Fast drop movements resulting from the phase change on a gradient surface. Science 291, 633–636 (2001).

ISO turninginsertnomenclature

Prakash M., Quéré D. & Bush J. W. M. Surface tension transport of prey by feeding shorebirds: the capillary ratchet. Science 320, 931–934 (2008).

The cactus spine was carefully fixed on a frame and investigated under a saturated fog flow with a velocity of ∼20–30 cm s−1 (by an ultrasonic humidifier using Milli-Q water). The behaviour of the water drops was recorded by the optical contact angle meter system with charge-coupled device components. (OCA 40, Dataphysics Instruments GmbH, Germany).

Fang G., Li W., Wang X. & Qiao G. Droplet motion on designed microtextured superhydrophobic surfaces with tunable wettability. Langmuir 24, 11651–11660 (2008).

Yang J. -T., Yang Z. -H., Chen C. -Y. & Yao D. -J. Conversion of surface energy and manipulation of a single droplet across micropatterned surfaces. Langmuir 24, 9889–9897 (2008).

Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China

ANSIinsertnomenclature

Estrela M. J., Valiente J. A., Corell D. & Millán M. M. Fog collection in the western Mediterranean basin (Valencia region, Spain). Atmos. Res. 87, 324–337 (2008).

where R is the local radius of the spine (R1 and R2 are the local radii of the spine at the two opposite sides of the drop), γ is the surface tension of water, R0 is the drop radius, α is the half-apex angle of the conical spine, and dz is the incremental radius of the spine (Fig. 4b). The Laplace pressure on the region near the spine’s tip (small radius R1) is larger than that near the base (large radius R2). This difference (ΔPcurvature) within the water drop initiates a driving force that makes the drop move from the tip to the base side along the cactus spine.

Again, this is an uncommon insert but ideal for understanding the ISO nomenclature. It is a screw-clamp type insert with a countersunk slot, used in finishing or semi-finishing operations on internal machining tools such as boring bars. Sometimes for some builders it is also used in drilling on mechanically clamped drills.

Chu K.-H., Xiao R. & Wang E. N. Uni-directional liquid spreading on asymmetric nanostructured surfaces. Nat. Mater. 9, 413–417 (2010).

In addition to the gradient of the Laplace pressure, the gradient of the surface-free energy is another driving force. Specifically, the microgrooves on the cactus spines have a gradient in width. The microgrooves are sparser near the base (less rough) than near the tip (rougher) of the spine (Fig. 4c and Supplementary Fig. S2). This roughness can be described using Wenzel’s equation27 as follows:

ISOinsertgrade chart

To determine the function of the barbs, spines and trichomes in the water collection process, we utilized a horizontal spine for our investigations (Fig. 3). By focusing on the behaviour of the water drops on the tip side of a spine covered with several oriented barbs, we observed the initial, simultaneous deposition of tiny water drops on the barbs (drop 1) and the spine (drop 2) (see Fig. 3a). As the deposition proceeded, growing drop 1 moved towards the base of the barb and coalesced with drop 2, forming the larger drop 1+2 (arrows in Fig. 3a). With a continuous deposition, drop 1+2 further coalesced with drop 3, which had been deposited on the adjacent barb. After water drop 1 moved away from the barb, a new cycle of water deposition and directional collection began. This process can be seen in Fig. 3a, with additional water drop 1′ depositing in the same location as the original drop 1. During this process, the gradient of the Laplace pressure between the two sides causes the water drops on the barbs to continuously move towards the base of the barbs.

The unique structural features of the cactus, such as the spines and the barbs with aligned gradient grooves and the cooperation between the spines and the trichomes, contributed to this system’s excellent functioning. To characterize the structure–function relationship in this efficient fog collection process, we propose a potential mechanism. Figure 4a shows an overview of the entire process of fog collection. ‘Deposition’ initially occurs on the barb and the spine, with the water drops moving directionally along them. As the deposition proceeds and the water drops coalesce, these drops increase in size, leaving from the tip side of the spine (‘Collection’). The bigger drops are then further transported along the gradient grooves (‘Transportation’) and absorbed through the trichomes at the base of the spines (‘Absorption’). The gradient of the Laplace pressure arising from the conical shape of the spine and the gradient of the surface-free energy arising from the gradient of the surface roughness along the spine are the two forces that drive the directional movement of the water drops.

After the initial stage, the drops that were collected from the barbs or deposited directly from the fog could be observed on the tip side of the spine (identified by numbers 1–5 in Fig. 3b). As the water deposition continued, the drops increased in size; the tip-side drops coalesced and moved directionally along the spine (black arrows in Fig. 3b). For example, drops 1 to 2, 1+2 to 3, 1+2+3 to 4, ultimately forming a large drop 1+2+3+4+5 (see Supplementary Movie 2). These observations demonstrated that the water drops could move from the tip to the base of the spine with the driving forces attributed to the gradient of the surface-free energy and the gradient of the Laplace pressure. In addition, the oriented barbs on the tip side engendered an asymmetrical surface structure, similar to the butterfly wings2, which enabled the unidirectional rolling and spreading of the water drops21,22, further aiding the directional movement of the water drops towards the base of the spine. Figure 3c shows this directional movement in detail (see also Supplementary Figs S4 and S5 and Supplementary Movie 3). The individual drops that were collected on adjacent spines both moved to the base side that was covered with trichomes. The trichomes and the spines formed conical internal surfaces, similar to shorebird’s beaks23, which can generate a strong capillary force. When the water drops contacted the trichomes, the drops were rapidly absorbed (Fig. 3c). Compared with the time-consuming transportation process (∼27 s), the absorption process was rapid (within a half second). The drops on adjacent spines also coalesced into one large drop that was absorbed by the trichomes (Supplementary Fig. S5). Another cycle of water collection began as drop 3 appeared on the upper spine and moved towards the trichomes. The rapid absorption process (that is, the rapid departure of the water drops) guaranteed the rapid regeneration of the fog collection process. As described in previous studies on various species, water drops can be absorbed into the stem14,16,18,19, especially in foggy areas; from there, they can be reserved in the mucilage cells containing polysaccharides with a high affinity to water that can reduce the evaporative loss13. The integration of the multiple functions within the spines and the trichomes, including water deposition, collection, transportation and absorption in the cactus, facilitated an efficient fog collection system.

Good morning, in today’s additional info I would like to give you some examples of ISO nomenclature in order to help you become familiar with the names of the inserts but above all with the coding itself. It is very important for anyone working in machining to know and understand the insert and its ISO nomenclature.

Mooney H. A, Weisser P. J & Gulmon S. L. Environmental adaptations of the Atacaman Desert cactus Copiupoa haeeliouirmo. Flora 166, 117–124 (1977).

Mettu S. & Chaudhury M. K. Motion of drops on a surface induced by thermal gradient and vibration. Langmuir 24, 10833–10837 (2008).

Carbideinsertidentification chart PDF

Malvadkar N. A., Hancock M. J., Sekeroglu K., Dressick W. J. & Demirel M. C. An engineered anisotropic nanofilm with unidirectional wetting properties. Nat. Mater 9, 1023–1028 (2010).

In situ observation of directional water collection on a vertically placed spine of the cactus (Opuntia microdasys) with the tip pointing down. The water drops collected at the tip move against gravitational force toward the base of the spine. (MOV 691 kb)

A water drop can be driven by chemical7,8, thermal24,25 and shape9,26 gradients. Specifically, a drop on a conical-shaped surface is often driven to the side with the larger radius due to the gradient of the Laplace pressure9. As illustrated in Fig. 4b, a cactus spine can be considered as a conical object with aligned grooves. This type of conical shape generates a Laplace pressure difference (ΔPcurvature) between the two opposite sides of the drop5,9 as follows:

The optical images of the cactus were recorded by a digital camera (Canon Powershot A1100IS). The microstructures of the spines, the barbs and the trichomes were observed by a field-emission scanning electron microscope (JEOL, JSM-6700 F, Japan) at an accelerating voltage of ∼3.0 KV.

Chen Y., He B., Lee J. & Patankar N. A. Anisotropy in the wetting of rough surfaces. J. Colloid Interf. Sci. 281, 458–464 (2005).

ISOinsertnomenclature pdf

This second example of an insert is not very common, but it is shown here for educational purposes. It is a turning and finishing insert that is assembled on boring bars for internal machining or on adjustable boring cartridges. The insert has a flat face and its fixing system is of the micro-fused bracket type.

In the lesson we saw three examples of ISO nomenclature when we asked Paolo the question; we saw an RNMG, a WNMG and a WCGT. Apart from the first letter which distinguishes the form, the first two inserts have identical parameters 2, 3 and 4 and exactly _NMG. This is also the most common ISO nomenclature for double-sided tools with chipbreaker geometry; these, as we shall see in the lesson on side rake angles, are fitted to negative tools. While the third case of the exercise posed to Paolo has parameters 2, 3 and 4 equal, _CGT. The latter is the most common ISO nomenclature for single-sided inserts.

(a) Optical image of a plant of O. microdasys stem covered with well-distributed clusters of spines and trichomes. (b,c) Magnified optical images of a single cluster with spines growing from the trichomes in the top (b) and side (c) view. (d) SEM image of a single spine divided into three regions, the tip (e) with an apex angle (2α) and oriented barbs, the middle (f,g) with gradient grooves, and the base with belt-structured trichomes. (f,g) Magnified images of regions near the base and tip of the cactus spine, respectively. The microgrooves near the base are wider and sparser than those near the tip. (h) Magnified image of a single barb with an apex angle (2β) covering the tip of the spine (e). Scale bars, 5 cm (a), 500 μm (b,c), 100 μm (d), 20 μm (e–g) and 2 μm (h).

(a) Continuous deposition of the water drops on the barbs and the spine. Initially, tiny water drops 1 and 2 were deposited concomitantly on the barb and the spine, respectively. Drop 1 moved toward the base of the barb with the volume increasing and coalesced with drop 2, forming larger drop 1+2. As the deposition proceeded, drop 1+2 further coalesced with drop 3 on the adjacent barb. A new cycle started when a subsequent small water drop 1′ deposited at the same location of initial drop 1. (b) Directional collection of the water drops on the spine. The deposited drop (1) and the coalesced drops (2–4) combine, moving directionally along the spine (black arrows) to form a large drop (1+2+3+4+5). (c) The behaviour of the water drops on the two adjacent spines containing trichomes. Drops 1 and 2 moved along the spines towards the base side, increasing in size. Upon contact with the trichomes at the base, the drops were absorbed immediately through the trichomes within a half second (from 64.32 to 64.72 s). After the absorption of the coalesced drops, a new cycle of water collection can begin, as observed with the tiny drop 3 at the middle of the spine. Scale bars, 50 μm (a), 100 μm (b) and 500 μm (c).

The fog collection ability of the cactus O. microdasys was investigated using a saturated fog flow with a velocity of ∼20 to 30 cm s−1 (see Methods); the movement of the water drops was recorded by a charge-coupled device camera in time-lapse mode5. We placed a single spine at multiple tilt angles (90°, 45°, −45°, −90° and 0°) to determine the effects of the spine’s growing direction on the directional movement behaviour of the water drops (Fig. 2). For each case, even when the spine was vertically fixed with the tip pointing down (Fig. 2d), the water drops were directionally driven from the tip to the base side of the spine (black arrows in Fig. 2 and Supplementary Movie 1). These results indicate that the gravitational force of the water drop has little effect on the directional water collection performance. The spines’ directions of growth from the cactus stem were not apparently a key factor in the directional movement of the water drops.

Insert designationchart

These fog collection abilities have been examined using the mechanisms of a single spine. To extend this approach to a more complete system with tens of spines and trichomes in a single cluster (Fig. 1b), the cooperation among spines-trichomes, multiple spines and multiple trichomes in the collection process (Fig. 4d) must also be considered. In addition, the array of multiple clusters on the stem surface (Fig. 1a) may further enhance the fog collection ability. The integration of the multi-level structures and the consequent integration of the multi-functional abilities, including the deposition, collection, transportation and absorption of the water drops, may provide O. microdasys with an efficient fog collection system. The investigation into the structure–function relationship within this system may offer systematic opinions that can be used to design novel materials and devices to efficiently collect fog. By mimicking the primary characters of the areole system of O. microdasys and considering the existing artificial fog collectors36,37,38, an artificial system with similar mechanisms to cactus is currently being developed, as shown in Supplementary Fig. S9 and Supplementary Note 1. Owing to its high efficiency and portability, this artificial system may find applications in the self water supply for plants and human beings that live in arid areas (Supplementary Fig. S9).

Ju, J., Bai, H., Zheng, Y. et al. A multi-structural and multi-functional integrated fog collection system in cactus. Nat Commun 3, 1247 (2012). https://doi.org/10.1038/ncomms2253

(a–e) A spine placed in fog with the following tilt angles: 90°, 45°, −45°, −90° and 0°, respectively. The deposited water drops were driven from the tip to the base of the spine, even with the spine vertically fixed with the tip pointing down (d). Scale bar, 500 μm.

Yarin A. L., Liu W., Reneker D. H. Motion of droplets along thin fibers with temperature gradient. J. Appl. Phys. 91, 4751–4760 (2002).

Let’s now move on to G, the last letter of the alphanumeric code; it indicates that our insert has a chip-breaking geometry on the face of the cutting edge, suitable for controlling and breaking the chips that will be formed during machining. Obviously, the geometry is studied and carried out on both faces of the insert. Moreover it has some characteristics in relation to the material to be machined and the operation to be carried out, i.e. finishing or roughing of a component.

The third and last pair of numbers in this part is 04, which in tenths of a millimetre is the value of the nose radius. The nose radius influences the strength of the cutting edge. In fact, a radius such as in this case 0.4 mm cannot be used for heavy roughing operations where, on the contrary, a larger radius will be useful, for example 1.2 mm. Therefore, this value of 0.4 mm also means that the field of application for this insert will be finishing or other light operations.

As we said in the lesson, the first letter identifies the shape of the insert; in this case is triangular with an angle between the cutting edges of 60 degrees.

Multiple biological structures have demonstrated fog collection abilities, such as beetle backs with bumps and spider silks with periodic spindle-knots and joints. Many Cactaceae species live in arid environments and are extremely drought-tolerant. Here we report that one of the survival systems of the cactus Opuntia microdasys lies in its efficient fog collection system. This unique system is composed of well-distributed clusters of conical spines and trichomes on the cactus stem; each spine contains three integrated parts that have different roles in the fog collection process according to their surface structural features. The gradient of the Laplace pressure, the gradient of the surface-free energy and multi-function integration endow the cactus with an efficient fog collection system. Investigations of the structure–function relationship in this system may help us to design novel materials and devices to collect water from fog with high efficiencies.

The optical images of a representative O. microdasys stem in Fig. 1a–c illustrate the structural characteristics of this plant. Clusters of needle-like spines and trichomes grow as a well-distributed array on the stem’s surface with distances ranging from ∼7 to 23 mm (Fig. 1a). Together, the top-view image in Fig. 1b and the side-view image in Fig. 1c illustrate a single cluster containing ∼100 spines. These spines grow in arbitrary directions with an average angle of 18.1±5.3° between the nearest two spines, forming a hemispherical structure. The spines range from ∼800 to 2,500 μm in length and ∼30 to 65 μm in diameter in the middle portion. The dotted line in Fig. 1c shows the trichomes at the base of the spines; these trichomes also form a hemispherical structure (see also Supplementary Fig. S1). To investigate these structures in detail, we used a scanning electron microscope (SEM) to observe an individual spine (see Fig. 1d–h, Supplementary Fig. S2, and Supplementary Fig. S3). Figure 1d shows that the spine is composed of three parts with different structural features, the tip contains oriented barbs, the middle contains gradient grooves and the base contains belt-structured trichomes. The spine has a conical shape with an apex angle (2α) of 12.3±1.6° (Fig. 1e). The magnified image of the barb in Fig. 1h also reveals a conical shape (apex angle 2β: 19.5±3.3°) with aligned grooves. The magnified images of the middle portion of the spine reveal multi-level grooves. The first-level grooves (the epidermal cells of the cactus spines)19,20 are microgrooves and have a gradient in width along the spine, from an average of ∼6.8 μm near the base to an average of ∼4.3 μm near the tip (Fig. 1f–g and Supplementary Fig. S2a,b). The second-level grooves (the folding sculptures of the epidermal cell)19 are primarily submicrogrooves lacking an obvious gradient in width and are characterized with a constant value of ∼0.6 μm over the entire length of the spine (Supplementary Fig. S3). The subtle integration of these structures (that is, conical spines and barbs, oriented barbs, gradient grooves and belt-structured trichomes) may contribute to the superior ability of these structures to collect fog.

Please note that thickness is very important as it constitutes the resistant section of the cutting edge. The greater the thickness, the greater the strength of our insert. Sometimes, in order to increase the life of the cutting edge with the same chip volume, i.e. with the same working data, it is sufficient to oversize the length of the cutting edge. This will provide a higher thickness, which will guarantee high resistance to the cutting forces and temperatures that will develop during turning.

Koch K. & Barthlott W. Superhydrophobic and superhydrophilic plant surfaces: an inspiration for biomimetic materials. Phil. Trans. R. Soc. A 367, 1487–1509 (2009).

How to cite this article: Ju, J. et al. A multi-structural and multi-functional integrated fog collection system in cactus. Nat. Commun. 3:1247 doi: 10.1038/ncomms2253 (2012).

Then we come to the third letter M. M establishes the tolerance class that is given with respect to the circle inscribed in the geometric figure of the insert. In this case is a circle with a diameter of 9.525. This value, the diameter of the inscribed circle, is taken from the insert size table, which we will see with parameter 5 relating to the size. Class M is a tolerance that is not very precise but nevertheless one of the most widely used in turning and which corresponds exactly to ±0.05 mm.

(a) An overview of the efficient fog collection system of O. microdasys progressing from ‘1 Deposition’ on the barbs and the spine to ‘2 Collection’ on the tip of the spine, ‘3 Transportation’ on the gradient grooves, and ‘4 Absorption’ upon contact with the trichomes. (b,c) Analysis of the driving forces arising from the gradient of the Laplace pressure and the gradient of the surface-free energy. A water drop on a conical spine should move towards the base side with the larger radius (R2) due to the relatively smaller Laplace pressure (b). In addition to the conical shape, the surface of the spine was covered with multi-level grooves. The gradient of the microgrooves was sparser near the base than near the tip of the spine (as indicated by the black arrows). The aligned submicrogrooves were similar along the spine as indicated by the red arrows (c). This gradient of the microgrooves produced a gradient of roughness, contributing to a gradient of the surface-free energy along the spine, driving the water drops towards the base side. (d) Cooperation among the multiple spines, the multiple trichomes and the spines-trichomes. The water drops that progress through the ‘1 Deposition’, ‘2 Collection’ and ‘3 Transportation’ processes are quickly absorbed into the cactus stem upon contact with the trichomes (‘4 Absorption’).

J.J., T.Z. and R.F. performed the experiments. J.J., H.B., Y.Z. and L.J. collected and analysed the data and proposed the mechanism of the multi-structure and the multi-function integrated fog collection system of cactus. H.B., J.J., Y.Z. wrote the text. L.J. conceived the project and designed the experiments.