Biomimetics on the micro- and nanoscale – The 25th anniversary of the lotus effect

• Matthias Mail,
• Kerstin Koch,
• Thomas Speck,
• William M. Megill and
• Stanislav N. Gorb

Beilstein J. Nanotechnol. 2023, 14, 850–856, doi:10.3762/bjnano.14.69

• the three species of beetles flying tethered in a wind tunnel. The results show that at low wind speeds, typical during insect flight, the species with the highest folding ratio and highest flapping frequencies produced the highest lift-to-drag ratio. The results are in agreement with other studies of

• repellency, but also on the capability of some surfaces to keep stable air layers under water – the so-called Salvinia Effect. Such air layers are of great importance for drag reduction (passive air lubrication), antifouling, sensor applications, or oil–water separation. Up to now, based on the

Liquid phase exfoliation of talc: effect of the medium on flake size and shape

• Samuel M. Sousa,
• Helane L. O. Morais,
• Joyce C. C. Santos,
• Ana Paula M. Barboza,
• Bernardo R. A. Neves,
• Elisângela S. Pinto and
• Mariana C. Prado

Beilstein J. Nanotechnol. 2023, 14, 68–78, doi:10.3762/bjnano.14.8

• here. An interesting hypothesis discussed in recent works [25][28] is that centrifugation might also lead to the loss of the smallest flakes along with the large ones due to drag effects. Flakes of the SC6 sample would be very susceptible to this effect, and a single centrifugation step at high

Dry under water: air retaining properties of large-scale elastomer foils covered with mushroom-shaped surface microstructures

• Matthias Mail,
• Stefan Walheim,
• Thomas Schimmel,
• Wilhelm Barthlott,
• Stanislav N. Gorb and
• Lars Heepe

Beilstein J. Nanotechnol. 2022, 13, 1370–1379, doi:10.3762/bjnano.13.113

• Effect, the capability to keep a stable air layer when submerged under water. Such air layers are of great importance, e.g., for drag reduction (passive air lubrication), antifouling, sensor applications or oil–water separation. Some biological models, e.g., the floating fern Salvinia or the backswimmer

• function for biomimetic air retaining surfaces is drag reduction. If an air layer is mounted between a solid surface and water flowing over this surface, the air layer serves as slip agent [26][27][28]. Such a drag reducing coverage allows significant friction reduction (up to 30%) in applications, where

• for the development of biomimetic air retaining surfaces have been found [1]. Transferring these parameters into technical surfaces, different prototypes have been developed, showing air retention over several years and drag reduction values up to 30% [24][36]. Up to now, all these prototypes are only

Straight roads into nowhere – obvious and not-so-obvious biological models for ferrophobic surfaces

• Wilfried Konrad,
• Christoph Neinhuis and
• Anita Roth-Nebelsick

Beilstein J. Nanotechnol. 2022, 13, 1345–1360, doi:10.3762/bjnano.13.111

• air layer between ship hull and water reduces the drag considerably. The physical basis of the capability of the Salvinia hairs to hold persistent air layers was the topic of various studies [5][26], which also included their elastic properties [27][28]. Main factors for the persistence and resilience

• . K. and A. R.-N., “Drag-reducing air–water interfaces”, see appendix A), it was attempted to tackle the problem of water/air interfaces at pillared surfaces theoretically. Principally, such an interface can be described by a differential equation. The main obstacle, however, is the complexity of this

• (Figure 2) circular columns of constant diameter and constant contact angle, but proved impracticable for more realistic protrusion models showing eggbeaters with hydrophilic tips (implying non-constant column diameter and contact angle, see the project “Drag-reducing air–water interfaces” in appendix A

Roll-to-roll fabrication of superhydrophobic pads covered with nanofur for the efficient clean-up of oil spills

• Patrick Weiser,
• Robin Kietz,
• Marc Schneider,
• Matthias Worgull and
• Hendrik Hölscher

Beilstein J. Nanotechnol. 2022, 13, 1228–1239, doi:10.3762/bjnano.13.102

• packaging and bottles, anti-fouling [36] and antibacterial [37] surfaces, or drag reduction [38] are imaginable. With the low-cost production of large areas of nanofur they seem also financially feasible. Schematic showing the roll-to-roll fabriction of a thin nanofur film by the example of PP and COC. (a

Application of nanoarchitectonics in moist-electric generation

• Jia-Cheng Feng and
• Hong Xia

Beilstein J. Nanotechnol. 2022, 13, 1185–1200, doi:10.3762/bjnano.13.99

• to the surface charges. When the liquid moves in the microchannel, it will drag the diffusion layer ions to form a flowing current, thus creating a potential difference, namely the flowing potential between the two ends of the channel. In nanochannels, approximating the channel geometry to be

Micro-structures, nanomechanical properties and flight performance of three beetles with different folding ratios

• Jiyu Sun,
• Pengpeng Li,
• Yongwei Yan,
• Fa Song,
• Nuo Xu and
• Zhijun Zhang

Beilstein J. Nanotechnol. 2022, 13, 845–856, doi:10.3762/bjnano.13.75

• that require torsion, often with transverse bending, and other deformations including alteration of the effective area [18]. The butterfly can increase the aspect ratio by spreading the forewings to generate maximum lift and increase the lift-to-drag ratio during flapping flight. Thus, it significantly

• tunnels and high-speed cameras, the relationships between wing shapes, flapping flight lift, and aerodynamic efficiency of dragonflies [31] and fruit flies [32] were examined. In addition, the influence of frequency and wind speed on the aerodynamic characteristics (such as the lift, drag, and vortex) of

• , three beetle species from different living environments were selected to explore the influence of different folding ratios on their flight performance through wind tunnel tests. The aspect ratios and flapping frequencies and the influence of the flow velocity on their lift-to-drag ratio are discussed in

Temperature and chemical effects on the interfacial energy between a Ga–In–Sn eutectic liquid alloy and nanoscopic asperities

• Yujin Han,
• Pierre-Marie Thebault,
• Corentin Audes,
• Xuelin Wang,
• Haiwoong Park,
• Jian-Zhong Jiang and
• Arnaud Caron

Beilstein J. Nanotechnol. 2022, 13, 817–827, doi:10.3762/bjnano.13.72

• and corresponds to friction. In our case, we attribute the observed hysteresis of the lateral force to the resistance to pull and drag a meniscus at the tip–metallic liquid interface. In principle, this resistance corresponds to the interfacial tension of the tip and metallic liquid. The occurrence of

Hierachical epicuticular wax coverage on leaves of Deschampsia antarctica as a possible adaptation to severe environmental conditions

• Elena V. Gorb,
• Iryna A. Kozeretska and
• Stanislav N. Gorb

Beilstein J. Nanotechnol. 2022, 13, 807–816, doi:10.3762/bjnano.13.71

• ., Asclepiadaceae and Cactaceae) [15], plays a crucial role in the protection from water loss. Biomimetic potential Since the discovery of the lotus effect [43], different properties of superhydrophobic surfaces in plants, which are highly relevant for modern technologies, such as self-cleaning, fluid drag

Reliable fabrication of transparent conducting films by cascade centrifugation and Langmuir–Blodgett deposition of electrochemically exfoliated graphene

• Teodora Vićentić,
• Stevan Andrić,
• Vladimir Rajić and
• Marko Spasenović

Beilstein J. Nanotechnol. 2022, 13, 666–674, doi:10.3762/bjnano.13.58

• thickness distribution, depending on the centrifugation parameters. However, it is important to consider the impact of buoyant density and drag coefficient of the materials, as well as the viscosity of the solvent and many other parameters to achieve the desired results [28]. It was demonstrated by Coleman

Enhancement of the piezoelectric coefficient in PVDF-TrFe/CoFe₂O₄ nanocomposites through DC magnetic poling

• Marco Fortunato,
• Alessio Tamburrano,
• Maria Paola Bracciale,
• Maria Laura Santarelli and
• Maria Sabrina Sarto

Beilstein J. Nanotechnol. 2021, 12, 1262–1270, doi:10.3762/bjnano.12.93

• place between PVDF-TrFe and CoFe2O4 nanoparticles, with the formation of a carbonyl group (C=O), as suggested by the FTIR spectra reported in Figure 1. When the DC magnetic field is applied, the ferromagnetic nanoparticles orient themselves along the direction of the applied field and then drag the

• of the β phase along the direction of the applied magnetic field rather than an increase of the β phase content itself. We believe that the increase of the d33 is due to the strong interaction between the molecular chains of the polymer nanocomposite and the magnetic field, thanks to the drag effect

A review on slip boundary conditions at the nanoscale: recent development and applications

• Ruifei Wang,
• Jin Chai,
• Bobo Luo,
• Xiong Liu,
• Jianting Zhang,
• Min Wu,
• Mingdan Wei and
• Zhuanyue Ma

Beilstein J. Nanotechnol. 2021, 12, 1237–1251, doi:10.3762/bjnano.12.91

• surfaces, where the true slip length is non-zero, the increase in amplitude leads to an increase in the drag resistance at the fluid–solid interface for rough surfaces of the same nature [86]. Interestingly, when the amplitude of the structured surface is large compared with the local slip length, the

• ]. 3 Applications of nanofluidics with tunable slip length 3.1 Drag reduction Reducing drag is of great significance in many areas related to nanotechnology, such as nanotribology [117], nanomedicine [118], and electrokinetics [119] due to the low energy dissipation. For instance, it has been reported

• that the drag reduction might lead to the improvement of energy conversion efficiency from mechanical to electrical energy for the generation of streaming current induced by the pressure difference [119]. As stated in Section 1.1, the drag reduction is equivalent to the increase of slip length, which

Thermophoretic tweezers for single nanoparticle manipulation

• Jošt Stergar and
• Natan Osterman

Beilstein J. Nanotechnol. 2020, 11, 1126–1133, doi:10.3762/bjnano.11.97

• the surrounding fluid via electroosmosis where an applied feedback electric field moves a layer of surface ions, which subsequently pulls the fluid, along with any suspended objects, by viscous drag. In such a manner, quantum dots in a liquid have been manipulated with nanometer precision [13]. Real

Effect of magnetic field, heat generation and absorption on nanofluid flow over a nonlinear stretching sheet

• Santoshi Misra and
• Govardhan Kamatam

Beilstein J. Nanotechnol. 2020, 11, 976–990, doi:10.3762/bjnano.11.82

• fluid which decreases with an increase in M due to a drag-like force, or resistance, that is developed by the fluid. Another observation was that the temperature gradient considerably increases with an increase in M, thus enhancing the thermal boundary layer thickness of the fluid as the external

An investigation on the drag reduction performance of bioinspired pipeline surfaces with transverse microgrooves

• Weili Liu,
• Hongjian Ni,
• Peng Wang and
• Yi Zhou

Beilstein J. Nanotechnol. 2020, 11, 24–40, doi:10.3762/bjnano.11.3

• were undertaken to evaluate the drag reduction performance of these bionic pipelines. It was found that the vortex ‘cushioning’ and ‘driving’ effects produced by the vortexes in the microgrooves were the main reason for obtaining a drag reduction effect. The shear stress of the microgrooved surface was

• reduced significantly owing to the decline of the velocity gradient. Altogether, bionic pipelines achieved drag reduction effects both in a pipeline and in a concentric annulus flow model. The primary and secondary order of effect on the drag reduction and optimal microgroove geometric parameters were

• obtained by an orthogonal analysis method. The comparative experiments were conducted in a water tunnel, and a maximum drag reduction rate of 3.21% could be achieved. The numerical simulation and experimental results were cross-checked and found to be consistent with each other, allowing to verify that the

Graphene–graphite hybrid epoxy composites with controllable workability for thermal management

• Idan Levy,
• Eyal Merary Wormser,
• Maxim Varenik,
• Matat Buzaglo,
• Roey Nadiv and
• Oren Regev

Beilstein J. Nanotechnol. 2019, 10, 95–104, doi:10.3762/bjnano.10.9

• (see Table 1 in the Experimental section). In such a case, the drag on the larger filler particles exerted by the composite medium (small filler particles and liquid) is similar to the drag they would encounter when passing through a neat liquid (without small particles) of the same density and

Bidirectional biomimetic flow sensing with antiparallel and curved artificial hair sensors

• Claudio Abels,
• Antonio Qualtieri,
• Toni Lober,
• Alessandro Mariotti,
• Lily D. Chambers,
• Massimo De Vittorio,
• William M. Megill and
• Francesco Rizzi

Beilstein J. Nanotechnol. 2019, 10, 32–46, doi:10.3762/bjnano.10.4

• a capacitive artificial neuromast based sensor platform that was integrated as high-density arrays to measure high-frequency acoustic flow patterns based on drag force [33][34][35][36]. The artificial neuromast is made of a vertical pillar with heights between 400 and 1000 μm, heights similar to the

• × 500 μm × 10 μm) which bent as air flow hit the plate. While the plate received the drag force of the air flow, the cantilevers measured the drag force using platinum strain gauges. One variable resistor (strain gauge) on each of the two cantilevers and two fixed resistances on the sensor substrate

• flow conditions, which was expected, as drag force on the bent cantilevers is a function of flow direction (or rotation angle in the presented experiment). When a cantilever is rotated by angle α, the expected signal amplitude is Aα = Amaxsin(α), where Amax is the signal amplitude for the rotation

A new bioinspired method for pressure and flow sensing based on the underwater air-retaining surface of the backswimmer Notonecta

• Matthias Mail,
• Adrian Klein,
• Horst Bleckmann,
• Anke Schmitz,
• Torsten Scherer,
• Peter T. Rühr,
• Goran Lovric,
• Robin Fröhlingsdorf,
• Stanislav N. Gorb and
• Wilhelm Barthlott

Beilstein J. Nanotechnol. 2018, 9, 3039–3047, doi:10.3762/bjnano.9.282

• ., for drag reducing ship coatings [5]. Submerged backswimmers are covered with a thin air layer, in particular on their hemelytra (forewings) [4][11][12]. This air layer remains stable over long periods of time under both static and dynamic conditions [4][13][14][15]. To understand the mechanism that

• typical morphological features of mechanoreceptors, such as a dendritic canal or an outer dendritic tip, were identified (Figure 5). The morphological data suggest that the clubs (Figure 1b, yellow) are used for pressure detection while the pins (Figure 1b, grey) are used for the detection of drag caused

• mechanosensitive setae not only for drag reduction, but also for the detection of prey or predators. With one exception [16], the involvement of air layers in a sensory function has never been demonstrated. A possible principle for a sensor that uses an air layer for the detection of pressure changes is shown in

The effect of flexible joint-like elements on the adhesive performance of nature-inspired bent mushroom-like fibers

• Elliot Geikowsky,
• Serdar Gorumlu and
• Burak Aksak

Beilstein J. Nanotechnol. 2018, 9, 2893–2905, doi:10.3762/bjnano.9.268

• results from load–drag–pull (LDP) experiments performed along (gripping) and against (releasing) the tilt direction indicate that the soft and the very soft joint fibers performed superior to the stiff joint fibers and maintained directionally dependent performance. The soft joint fibers achieved up to 22

• than vertically aligned [10]. This tilt, in addition to enhanced performance [11], equips the gecko with directional adhesion properties as shown by Autumn et al. [12]. When they tested setae using a load–drag–pull (LDP) experiment, they found that setae exhibit very high interfacial shear and tension

• Figure 1c. Friction and adhesion are measured as a function of initial compressive load (preload) using load–drag–pull (LDP) experiments. Fibers arrays were dragged in the direction of tilt (i.e., gripping direction) and against the tilt direction (i.e., releasing direction) to assess directional

Recent highlights in nanoscale and mesoscale friction

• Andrea Vanossi,
• Dirk Dietzel,
• Andre Schirmeisen,
• Ernst Meyer,
• Rémy Pawlak,
• Thilo Glatzel,
• Marcin Kisiel,
• Shigeki Kawai and
• Nicola Manini

Beilstein J. Nanotechnol. 2018, 9, 1995–2014, doi:10.3762/bjnano.9.190

• of most moving machinery parts, it has the disadvantages of a relatively large viscous drag and the risk of a transition to the boundary regime under certain, sometimes uncontrolled conditions. Just recently, a few systems based on layered materials, such as graphene or molybdenum chalcogenides have

Nonlinear effect of carrier drift on the performance of an n-type ZnO nanowire nanogenerator by coupling piezoelectric effect and semiconduction

• Yuxing Liang,
• Shuaiqi Fan,
• Xuedong Chen and
• Yuantai Hu

Beilstein J. Nanotechnol. 2018, 9, 1917–1925, doi:10.3762/bjnano.9.183

• and the acoustic wave itself [1][2][3][4]. This kind of interaction between an acoustic wave and carriers in piezoelectric semiconductors is called the acoustoelectric effect, which is a special case of a more general phenomenon, called wave–particle drag [4][5]. Obviously, acoustoelectric coupling of

Surface characterization of nanoparticles using near-field light scattering

• Eunsoo Yoo,
• Yizhong Liu,
• Chukwuazam A. Nwasike,
• Sebastian R. Freeman,
• Brian C. DiPaolo,
• Bernardo Cordovez and
• Amber L. Doiron

Beilstein J. Nanotechnol. 2018, 9, 1228–1238, doi:10.3762/bjnano.9.114

• (trapping force), scattering force, coating force, and drag force (Figure 1) [21]. Nanoparticles are either trapped in the evanescent field and reside in a potential well or escape the potential well via Brownian motion due to inadequate trapping force [22]. The potential well is the sum of all forces, and

• particle polarizability is α = [3V(ε − εs)/(ε + 2εs)], V is the particle volume, ε and εS are the dielectric constants of the particle and solution, respectively, and I is the local intensity. As the particle travels in solution, a drag force also acts on the particle along the opposite direction of the

• laser waveguide. According to Stokes’s Law, the drag force can be written as, where η is the solution viscosity, r is the particle radius and v is the particle velocity. When a particle enters the evanescent field and is trapped by the gradient force, it can be transported along the direction of the

Engineering of oriented carbon nanotubes in composite materials

• Razieh Beigmoradi,
• Abdolreza Samimi and
• Davod Mohebbi-Kalhori

Beilstein J. Nanotechnol. 2018, 9, 415–435, doi:10.3762/bjnano.9.41

• of the gap between the two layers and the simultaneous effects of the shear force and mechanical tensile stretch, a slight drag force pulls the CNT in the vertical direction. However, the obtained free CNTs are certainly not vertical relative to the surface of layers. Although the small length of the

The nanofluidic confinement apparatus: studying confinement-dependent nanoparticle behavior and diffusion

• Stefan Fringes,
• Felix Holzner and
• Armin W. Knoll

Beilstein J. Nanotechnol. 2018, 9, 301–310, doi:10.3762/bjnano.9.30

• height, ω = h/a, for [27] by Faxèn [28] and Goldman [29], respectively. A similar approach leads to the drag-reduced diffusion in a slit [30]: where d is the gap distance of the confining walls. Oseen suggested the LSA [30] where the drag of each wall is treated independently and the total force is given

• role in a nanofluidic system, in particular when a particle is close to a charged wall. Whereas diffusion measurements for uncharged particles [15] and for particles in electrolyte with higher ionic concentration [33] are in agreement with predictions that consider only a hydrodynamically hindered drag

• . There is considerable evidence of an increased drag of charged particles near charged walls in a weak electrolyte [18][38]. In a similar experimental configuration Eichmann et al. [18] measured a ≈30% (≈55%) lower lateral diffusion coefficient for 60 nm (100 nm) gold nanospheres with a relative radius

Nematic topological defects positionally controlled by geometry and external fields

• Pavlo Kurioz,
• Marko Kralj,
• Bryce S. Murray,
• Charles Rosenblatt and
• Samo Kralj

Beilstein J. Nanotechnol. 2018, 9, 109–118, doi:10.3762/bjnano.9.13

• rotation of an assembly of TDs. Finally, we show that an external electric field could be used to drag the boojum fingertip towards the interior of the confinement cell. Assemblies of TDs could be exploited as traps for appropriate nanoparticles, opening several opportunities for the development of