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The control of fundamental optical properties, such as transmission and reflection, over metallic surfaces plays a significant role in multiple fields like solar cells and aerospace. The direct laser etching in air can perform a variety of flexible control abilities in optical functional metal surfaces. In this paper, the authors use the aluminum alloy as an example of widely metal materials and propose two kinds of controlling strategies: large-range controlling strategy and small-range precise controlling strategy. The former changes the process repeat number of femtosecond lasers or the scanning speed of nanosecond lasers. The latter combines the femtosecond laser and the nanosecond laser. The results show that when the process repeat number of femtosecond lasers is changed from 30 to 1, the height of the induced micropillars on the surface of Al alloy is changed from 80 to 6 μm. As a result, the reflectivity of samples will change from ∼16% to ∼87%. The nanosecond laser-induced micro-/nanostructures achieve the reflectivity changing from ∼18% to ∼79% when the scanning speed changes from 10 to 400 mm/s in a spectrum range of 250–2000 nm. What is more, after being fabricated in the way of two-step controlling strategy, the reflectivity raises from ∼30% to ∼40% when the scanning speed of nanosecond lasers changes from 10 to 200 mm/s, while the reflectivity of samples fabricated simply by nanosecond laser changes from ∼18% to ∼66% when the scanning speed changes in the same range and other parameters are kept the same. In addition, the authors demonstrated that the two-step precise controlling strategy is applicable to a variety of metals such as copper, stainless steel, and titanium. [ABSTRACT FROM AUTHOR]

The phenomenon of droplet jumping induced by coalescence holds significant potential for application in diverse areas such as water collection, self-cleaning, and thermal management of electronic devices. In comparison to a flat surface, a superhydrophobic surface with structure can affect the interaction between the droplet and the surface, thereby affecting parameters such as the droplet jumping velocity. In this study, numerical simulation was used to examine the similarities and differences of coalescence-induced droplet jumping on superhydrophobic surfaces with uniform and non-uniform micropillars, as well as the effect of micropillar non-uniformity on droplet jumping. The results indicated that the non-uniform distribution of micropillars could lead to asymmetries in the shrinkage of the liquid bridge, the morphology of the droplet when it jumps off the surface, and the distribution of the high-pressure region at the bottom of the droplet. Additionally, it decreased the droplet's vertical velocity while substantially increasing the horizontal velocity. When the droplet radius was constant, decreasing the micropillar width or increasing the micropillar spacing on the sparse side was advantageous for the droplet jumping on a superhydrophobic surface with non-uniform micropillars. By defining the solid fraction on the micropillar surface with non-uniform distribution, the coupling effect of the width and spacing of the micropillars on the droplet jumping was thoroughly analyzed, and the optimal solid fraction for the best directional transport effect of droplets was determined. This study revealed the mechanism underlying the effect of surface micropillar structure on coalescence-induced droplet jumping, and the findings could guide the design of superhydrophobic surface microstructures, which was of great significance for the advancement of droplet jumping applications. [Display omitted] • The droplet jumping on superhydrophobic non-uniform micropillar surfaces was studied. • The effect of micropillar width, height, and spacing on droplet jumping was revealed. • The solid fraction of the non-uniform micropillar surface was proposed. [ABSTRACT FROM AUTHOR]

This paper presents the mechanical behaviour of single crystal Ta (6.5 GPa–22 GPa) 1-D shocked along the three principal crystallographic directions [100], [110] and [111]. Room temperature mechanical testing was carried out on micropillars to make possible precise load and displacement measurements. The findings exhibit a marked variation in the flow curve and strain hardening between the three orientations, and relative changes are noticed with shock loading. The yield strength (YS) increases linearly as a function of shock load. The YS was highest along [111] (282 MPa) compared with the [100] and [110] orientations (194 and 206 MPa). The strain hardening rates without pre-shock loading are found to be in the order [111] > [100] > [110] and this is not altered by pre-shock loading. Deformation was accomplished by slip on {112} planes. Further, assessments are considered to identify effective plastic strain accumulation during shock loading. The accumulation of effective plastic strain was found to be similar for all directions for shock loading up to 6.5 GPa, however, above 15 GPa the effective strain was lower for [110] compared to [100] and [111] directions. An attempt is made here to assess the flow curve hardening behaviour and variation in yield strength based on a different combination of pair orientation to throw some light into materials response at high-pressure shock loading. [ABSTRACT FROM AUTHOR]

[Display omitted] • A copper film containing incoherent twin boundaries is deposited, thick enough for micropillar compression. • Multi-slip compression direction is not to be suitable for the observation of dislocation transmission. • A novel configuration is used to fabricate thin-film micropillars to promote single slip in bi-crystals. • Incoherent twin boundaries show some resistance to transmission, but are penetrable to dislocations. The role of a ∑3{1 1 2} incoherent twin boundary (ITB) on the shear stress of Cu at the micron scale has been investigated through microcompression of bi-crystalline pillars containing ITB, as well as single-crystalline pillars, in two different compression directions. The Cu sample containing ITBs was synthesized using magnetron sputtering on a sapphire substrate. Firstly, pillars along [1 1 1] compression direction were milled on the film surface. As multiple slip systems were activated upon loading, the dislocation-ITB interaction in this direction was dominated by the dislocation–dislocation interactions. Another set of pillars was milled from the side of the film (in the thickness of the film) in a nominally [13 4 ¯ ] compression direction. Compression in this direction activated a single slip in each grain, which facilitated the investigation of the interaction between dislocations and ITBs. Post - mortem images showed that slip traces were not distinctly connected at the boundary unlike ideal slip transmission in pillars containing a coherent twin boundary. Moreover, bi-crystalline pillars in the single slip direction are stronger than single-crystalline pillars. The observations indicate that ITBs are not impenetrable for dislocations, but the boundary demonstrates some resistance to transmission. [ABSTRACT FROM AUTHOR]

Micropillar arrays with radial p–n junctions are attractive for photovoltaic applications, because the light absorption and carrier collection become decoupled. The main challenge in manufacturing radial p–n junctions is achieving shallow (dopant depth 1020 cm−3) that will allow the formation of a quasi-neutral region (QNR) and space charge region (SCR) in its tiny geometry. This experimental study investigates an approach that allows shallow and heavy doping in silicon micropillars. It aims to demonstrate that silicon dioxide (SiO2) can be used to control the dopant penetration depth in silicon micropillars.

In this work, we report the optical and thermal properties of Cu(BTC)·3H2O (BTC = 1,3,5-benzenetricarboxylic acid) and Zn(ADC)·DMSO (ADC = 9,10- anthracenedicarboxylic acid, DMSO = dimethyl sulfoxide) metal-organic frameworks (MOFs) micro/nanopillars. The morphologies of MOFs on surfaces are most in the form of micro/nanopillars that were vertically oriented on the surface. The size and morphology of the pillars depend on the evaporation time, concentration, solvent, substrate, and starting volume of solutions. The crystal structures of the nanopillars and micropillars are the same, confirmed by powder XRD. Zn(ADC)·DMSO pillars have a strong blue fluorescence. Most of ADC in the pillars are in the form of monomers, which is different from ADC in the solid powder.

Neural tissue-related illnesses have a high incidence and prevalence in society. Despite intensive research efforts to enhance the regeneration of neural cells into functional tissue, effective treatments are still unavailable. Here, a novel therapeutic approach based on vertically aligned carbon nanotube forests (VA-CNT forests) and periodic VA-CNT micropillars produced by thermal chemical vapor deposition is explored. In addition, honeycomb-like and flower-like morphologies are created. Initial viability testing reveals that NE-4C neural stem cells seeded on all morphologies survive and proliferate. In addition, free-standing VA-CNT forests and capillary-driven VA-CNT forests are created, with the latter demonstrating enhanced capacity to stimulate neuritogenesis and network formation under minimal differentiation medium conditions. This is attributed to the interaction between surface roughness and 3D-like morphology that mimics the native extracellular matrix, thus enhancing cellular attachment and communication. These findings provide a new avenue for the construction of electroresponsive scaffolds based on CNTs for neural tissue engineering., (© 2023 Wiley-VCH GmbH.)

This study presents the mechanical characterization of UV-curing acrylate systems. UV-curable polymers are commonly used in the stereolithography (SLA) technique to build multi-layered objects. Typically, the mechanical properties of the 3D-printed product are affected by the intrinsic material heterogeneity along the sample thickness. To understand what determines this heterogeneity, single layers of UV-curable polymer are characterized and the effect of process conditions on the mechanical properties is studied. Micro-compression experiments are carried out to determine the intrinsic mechanical properties which are representative of one single UV-cured layer. To determine the right conditions to generate maximally-cured micropillars, the evolution with irradiation time of monomer conversion, glass-transition temperature and yield stress has first been studied. Thereto, micrometer-sized pillars and dog-bone shaped samples have been prepared via UV-curing. Micro-compression measurements on maximally-cured micropillars are performed to study possible size effects. The results reveal that with decreasing pillar size, the yield stress decreases. Tensile measurements are performed on dog-bone shaped samples which have been processed in the same way as compared to the compression samples. These tensile tests show higher yield stress values when compared with compression tests. This size effect can be attributed to the rinsing with acetone during the sample preparation that leads to a removal of monomer from the crosslinked network. As a consequence, in the real 3D-printing process, the mechanical properties will depend on the feature size. In conclusion, a method is presented to determine the mechanical properties of one single layer of material used in the rapid-prototyping SLA process. The experimental procedure we adopted requires only a few millilitres of material and, therefore, is well suited for screening materials under real SLA process conditions. [ABSTRACT FROM AUTHOR]

Microcompressive tests were performed to investigate the intrinsic modulation effect and extrinsic diameter effect on strength and deformation behaviors of nanolaminated Cu/Cu-Zr crystalline/amorphous micropillars within a diameter D range from 300 to 1500 nm as well as a modulation ratio η range from 0.1 to 3.0. Experimental results revealed a transition of D -dependent deformation mode from homogeneous-like to shear localization at large η , while D -independent homogeneous extrusion of Cu at small η . Furthermore, the flow strength increased with raising D at small η , but decreased at large η , exhibiting a D -insensitive strength at a critical η* ~ 0.5. These unusual results were rationalized in terms of a coupling effect of dislocation actions and shear transformation zone mediated operations. [ABSTRACT FROM AUTHOR]

Highlights • Third bodies formed during wear are complex in microstructure & phase composition. • Application of nanoindentation to determine hardness of tribofilm was reviewed. • Micro/nanopillar testing on tribofilm was reviewed. • Pros and cons of the above two nanomechanical techniques were discussed. • Challenges & future directions of nanomechanical testing of third bodies were presented. Abstract During wear, materials undergo chemical and mechanical changes that lead to the formation of what are known as ‘third bodies’. Tribologists have long understood that third bodies have significant influence on the friction and wear performance of materials. However, the inhomogeneous nature of third bodies and how they form at the ‘buried interface’ of a sliding tribological contact has long made it difficult to fully characterize and study them. Recently, there have been significant advancements in nanomechanical testing such that researchers have begun to use these techniques to, for the first time, determine mechanical properties of third bodies. Coupling these measurements with high resolution electron microscopy and surface chemical analysis has finally given tribologists the ability to obtain the necessary data to understand and model third bodies and their connections to friction and wear. This review will present recent work on the topic of nanomechanical testing of third bodies while at the same time identifying the challenges and opportunities this research presents. [ABSTRACT FROM AUTHOR]

The size effect on the mechanical behaviors of single crystalline Fe-31.2Pd (at.%) micropillars with four different pillar diameters (approximately 2 μm, 1 μm, 500 nm and 400 nm) were studied by compressing in the [001] direction. Both the Young's modulus and yield stress increase with the decrease of pillar diameter. The main defects in the plastically deformed pillars are the {111} deformation twins, which could be covered by high density of dislocations after further plastic deformation in a 400 nm pillar. A repeatable elastic-like strain ~4% was observed for more than 40,000 cycles. [ABSTRACT FROM AUTHOR]

Eutectic alloys are widely used as solder-joint materials due to their suppressed melting points, but when used in micro-devices with small dimensions, their characteristic lamellar microstructure may lead to an internal length scale that affects strength. Here, we report an unusual ‘smaller-being-weaker’ phenomenon in eutectic Sn/Pb alloys with fine lamellar microstructure, namely, in the specimen-size regime close to and slightly larger than the interphase lamellar spacing, the strength decreases with decreasing size, while above this regime the strength tends towards the bulk value. Theoretical modeling indicates that in a fine lamellar microstructure, high contents of dislocations are retained, so that strength is governed by mutual dislocation interactions, rather than by dislocation starvation. Therefore, in smaller samples, fewer interphase lamellar boundaries are present to block dislocations, thus resulting in a ‘smaller-being-weaker’ behavior. In samples a lot larger than the lamellar spacing, significant strengthening arises from Taylor hardening and mutual dislocation interactions as a result of significant dislocation retention by the interphase boundaries, so that strength does not depend on specimen size anymore. In a course lamellar microstructure, however, even a larger micro-specimen may contain insufficient interphase boundaries to significantly retain dislocations, and strength may be governed by the starvation effect due to significant loss of dislocations at free surfaces. In this case, the size effect of strength may become a lot milder, or even exhibit the conventional “smaller-being-stronger” behavior. The results here supplement conventional knowledge on size effects in micro-scaled crystalline materials, and provide important implications on solder-joint design in micro-devices. [ABSTRACT FROM AUTHOR]

In this research paper, performance analysis of two different material-based micropillars capacitive antennas is proposed. The method involves formation of self-organized mask, micropillar formation by using process of etching and metal deposition (Au/Cr) on the top and bottom of micropillars. For fabrication of these capacitive antennas, we considered 2-inch p-type silicon (Si) wafers as a substrates material while upper and lower plates of capacitive antenna were fabricated by using gold as plating material on top and bottom. Both capacitive antennas were fabricated by taking the two different materials (ZnO and HfO2) micropillars which acts a dielectric material between two upper and lower gold plates. For realization of both antennas firstly we have simulated both the antenna using CST Microwave studio software and thereafter fabricated by using appropriate microfabrication technique. Both the metamaterial-based capacitive antennas were designed by taking dimension of 35 × 26 mm on the 2″ Si substrate. The thickness (h) and dielectric constant (εr) of silicon substrate were taken as 0.270 mm and 11.7, respectively. The proposed antenna was designed to operate at frequency range of 1-10 GHz, which signifies that return loss (S11) parameter must be less than −10 dB and voltage standing wave ratio must be less than 2. To validate the design, various parameters of RF antenna such as the return loss, gain, surface current distribution, and radiation patterns were obtained and compared for the fabricated antennas. The simulated and experimental results were found to show good agreement. [ABSTRACT FROM AUTHOR]

This work presents a micropillar-based microfluidic system, which was designed mainly for three-dimensional (3D) cardiac cell culture, but it can be also used for two-dimensional (2D) cell culture. 3D cell culture was based on the use of the hydrogel, which is gelled by the contact with culture medium inside the microsystem. The geometry of the designed microsystem provided gelation of the liquid hydrogel-cells mixture (3D) and location of the cells (2D) in the middle of the main microchannel. This process was facilitated by the presence of micropillar array. Furthermore, the integration of the designed microsystem with the multi-well plate reader allowed to monitor cell proliferation in situ during the cultures. The designed microsystem was successfully applied to 3D and 2D human cardiomyocytes cultures for 4 days. It was also used as cardiac cell culture model for the investigation of isoproterenol cytotoxicity. The results of both cultures in the designed microsystem indicated that cardiomyocytes proliferated better in 3D than 2D conditions and the cytotoxic effect of investigated drug was lower in 3D than 2D culture. We suggest that the presented microsystem could be a promising microfluidic heart model for analysis of various drugs. [ABSTRACT FROM AUTHOR]

Tunneling nanotubes are important membrane channels for cell-to-cell communication. In this study, we investigated the effect of the microenvironment on nanotubular structures by preparing a three-dimensional silk fibroin micropillar structure. In previous reports, tunneling nanotubes were described as stretched membrane channels between interconnected cells at their nearest distance. They hover freely in the cell culture medium and do not contact with the substratum. Interestingly, the micropillars could provide supporting points for nanotubular connection on silk fibroin films, where nanotubular structure formed a stable anchor at contact points. Consequently, the extension direction of nanotubular structure was affected by the micropillar topography. This result suggests that the hovering tunneling nanotubes in the culture medium will come into contact with the raised roadblock on the substrates during long-distance extension. These findings imply that the surface microtopography of biomaterials have an important influence on cell communication mediated by tunneling nanotubes.

Silicon micropillars have been suggested as one of the techniques for improving the efficiency of devices. Fabrication of micropillars has been done in several ways—Metal Assisted Chemical Etching (MACE) and Reactive Ion Etching (RIE) being the most popular techniques. These techniques include etching through the surface which results in surface damage that affects the carrier lifetime. This paper presents a study that compares the carrier lifetime of micropillars fabricated using RIE and MACE methods. It also looks at increasing carrier lifetime by surface treatment using three main approaches: surface passivation by depositing Al2O3, surface passivation by depositing SiO2/SiN, and surface passivation by etching using KOH and Hydrofluoric Nitric Acetic (HNA) solution. It was concluded that passivating with SiO2 and SiN results in the highest carrier lifetime on the MACE and RIE pillars.

Compression-compression cyclic deformation of nanocrystalline NiTi tubes intended for medical stents and with an outer diameter of 1 mm and wall thickness of 70 μm was studied using micropillars produced by FIB with the loading axis orthogonal to the tube axis. These micropillars were cycled in a displacement-controlled mode using a nanoindenter equipped with a flat punch to strain levels of 4, 6 and 8% in each cycle and specimens were subjected to several hundred cycles. The cyclic response of two NiTi tubes, one with A f of 17 °C and the other with an A f of −5 °C is compared. The texture of the tube with the A f of −5 °C was measured at the microscopic level using transmission electron microscopy and at the macroscopic level by X-ray diffraction and good agreement was noted. Characteristics such as i) a reduction in the forward transformation stress, ii) increase in maximum stress for a given displacement amplitude, and iii) a reduction in the hysteresis loop area, all with increasing number of cycles, observed typically during cyclic deformation of conventional macroscopic specimens, were captured in the micropillar cyclic tests. These observations lead to the conclusion that micropillar compression testing in a cyclic mode can enable characterizing the orientation-dependent response in such small dimension components that see complex loading in service, and additionally provide an opportunity for calibrating constitutive equations in micromechanical models. [ABSTRACT FROM AUTHOR]

The present work investigates, for the first time, the effects of martensitic transformation as well as orientation on the stress-strain behaviour of austenitic micropillars. It is found that large strain burst can be induced by martensitic transformation, and its magnitude depends on the orientation of pillars. Pillars with an orientation close to [1 0 0] show a much larger strain burst than the ones with an orientation close to [1 1 0]. This is because [1 0 0] pillars have a much higher fraction of transformed martensite to which the magnitude of strain burst is directly correlated. [ABSTRACT FROM AUTHOR]

Irradiation-induced defects have been experimentally observed either to inhibit or promote strain bursts and lead to plastic flow localization. Through three dimensional discrete dislocation dynamics simulations, this work unravels the mystery of how and why irradiation-induced defects enhance or inhibit strain bursts in submicron BCC iron and FCC Cu single crystals. It is shown that smaller strain burst amplitudes in irradiated nano- and micro-pillars are obtained under stress control conditions. However, under strain control conditions, bursts are found not to be sensitive to irradiation, despite the arresting effect of radiation defects. This feature is a result of rapid stress relaxation truncating the strain burst, compared with the influence of irradiation-induced defects. In heavily irradiated materials, dislocation avalanches and strain bursts are shown to be promoted. The influence of dislocation-defect interaction mechanisms, cross slip, irradiation dose, as well as loading mode on strain bursts is systematically investigated, and the results compared with experimental observations. [ABSTRACT FROM AUTHOR]

We developed a method to fabricate dense elastomer pillar arrays with height gradient and uniform top surface by using photolithography and soft-lithography techniques. This method relies on formation of sloped tails aside pre-patterned stripes by spin-coating a low-viscosity resist and back side UV exposure through a Cr mask. PDMS pillar arrays were produced by casting to study migration of NIH 3T3 cells. With PDMS pillars of 2 μm diameter, 5.5 μm pitch size and variable heights in the range between 3.8 μm and 10.1 μm, we observed that NIH 3T3 cells migrated toward and then remained in the area of greater stiffness with smaller pillar heights. Thus, PDMS pillar arrays with height gradient and uniform top surface were shown to be useful in cell culture durotaxis studies. [ABSTRACT FROM AUTHOR]

The superelastic behavior of single crystal Cu-Al-Mn-Ni shape memory alloy micro-pillars was studied under compression as a function of crystallographic orientation. Cylindrical pillars of about 2 μm diameter were micro-machined from targeted crystal orientations. While pillars oriented close to the [001] direction showed the largest total transformation strain (∼7%), plastic deformation dominated the compressive response in the pillars milled close to the [111] direction due to their high elastic anisotropy combined with the large stresses required to induce the transformation. Shape strain contour plots were constructed for γ′ and β′ martensites, and the martensite start stress was calculated using the Clausius-Clapeyron equation. The same general trends are observed in both the experimental and calculated results, with some exceptions: larger transformation stresses and lower transformation strains are observed in the microsized pillars. [ABSTRACT FROM AUTHOR]

The growing role of charged particle irradiation in the evaluation of nuclear reactor candidate materials requires the development of novel methods to assess mechanical properties in near-surface irradiation damage layers just a few micrometers thick. In situ transmission electron microscopic (TEM) mechanical testing is one such promising method. In this work, microcompression pillars are fabricated from a Fe 2+ ion irradiated bulk specimen of a model Fe-9%Cr oxide dispersion strengthened (ODS) alloy. Yield strengths measured directly from TEM in situ compression tests are within expected values, and are consistent with predictions based on the irradiated microstructure. Measured elastic modulus values, once adjusted for the amount of deformation and deflection in the base material, are also within the expected range. A pillar size effect is only observed in samples with minimum dimension ≤100 nm due to the low inter-obstacle spacing in the as received and irradiated material. TEM in situ micropillar compression tests hold great promise for quantitatively determining mechanical properties of shallow ion-irradiated layers. [ABSTRACT FROM AUTHOR]

• FCM has an adhesion strength of 1.2 MPa under a loading force of 5 mN, which is 3.7 times of the micropillars with a flat punch top. • FCM is quite robust that the structure and the adhesion performance are very well maintained even after1000 cycles of adhesion tests. • The structure of FCM is quite simple that it could be easily fabricated and replicated. Robust and strong adhesion is highly required for reversible adhesions. Inspired by gecko setae and octopus sucker, micropillar array with frustum of conical micropits (FCM) was fabricated by direct laser writing lithography. With an optimized micropit in FCM, the adhesion strength of 1.2 MPa is achieved under a loading force of 5 mN, which is 3.7 and 2.1 times the micropillars with flat punch top and circular conical micropit, respectively. Under a loading force larger than 3 mN, compliant contacts are formed between FCM micropillars and the counterpart surface, which results in a uniformly distributed stress at the separating interface, an instantaneous detachment of multiple FCM micropillars, and therefore a strong adhesion. Moreover, the adhesion of FCM is quite robust that 1000 cycles of attaching and detaching have no influence on the adhesion performance. The work here not only provides a bioinspired structure for strong and robust adhesion but also consolidates the concept of combining features from different biological systems to create new functional materials. [ABSTRACT FROM AUTHOR]

Viscosity monitoring has recently received significant attention in various fields such as pharmacy, oil industry, food industry, and medical diagnostics. Given that the commercially available viscometers usually require a large sample volume to conduct accurate measurement, there is an urgent need to develop a viscometer that can consume the least sample while maintaining high accuracy. Despite of being simple, rapid, and cost-effective, quartz crystal microbalance (QCM) based viscometers are low in sensitivity and not able to measure viscosity directly. This work focuses on the development of a novel micropillar-enhanced QCM viscosity measurement device which relies on the coupled vibration between micropillars and quartz substrate (QCM-P) to achieve an ultra-sensitive viscosity measurement of a sample droplet. A hybrid model by integrating an equivalent circuit and numerical simulation approach was established to understand the working principle of the QCM-P device and evaluate the viscosity value. The experimental results and analysis demonstrate that the micropillar-enhanced acoustic wave (μPAW) devices such as QCM-P viscometer is a promising device for droplet-based viscosity measurement. [Display omitted] • PMMA micropillars are fabricated on an acoustic wave substrate to form a novel resonance vibration system for viscosity measurement • The developed μPAW device is capable of measuring the viscosity of a liquid droplet (200 μl) at an ultra-high sensitivity • Both bandwidth and frequency shifts of the μPAW device can be utilized to evaluate viscosity • A hybrid model is developed to analyze the effects of solution properties on the frequency and bandwidth shifts of μPAW devices [ABSTRACT FROM AUTHOR]

In this work, we report investigations of the swimming behaviour of Paramecium tetraurelia , a unicellular microorganism, in micro-engineered pools that are decorated with thousands of cylindrical pillars. Two types of contact interactions are measured, either passive scattering of Paramecium along the obstacle or avoiding reactions (ARs), characterized by an initial backward swimming upon contact, followed by a reorientation before resuming forward motion. We find that ARs are only mechanically triggered approximately 10% of the time. In addition, we observe that only a third of all ARs triggered by contact are instantaneous while two-thirds are delayed by approximately 150 ms. These measurements are consistent with a simple electrophysiological model of mechanotransduction composed of a strong transient current followed by a persistent one upon prolonged contact. This is in apparent contrast with previous electrophysiological measurements where immobilized cells were stimulated with thin probes, which showed instantaneous behavioural responses and no persistent current. Our findings highlight the importance of ecologically relevant approaches to unravel the motility of mechanosensitive microorganisms in complex environments., Competing Interests: We declare we have no competing interests., (© 2023 The Authors.)

We report the discovery of a micropillar-based quartz crystal microbalance (QCM) coupled resonator sensor (CRS) in detecting flow rates of gases with different densities. The fabricated QCM CRS was housed in a stainless steel chamber and the resonance frequency changes associated with gas flow at small values of mass flow rates inside the chamber were measured. Argon and helium were used as the test gases. The results obtained revealed an extraordinary sensitivity to mass flow rate changes under room temperature and flow rates as low as 20 sccm. Moreover, the QCM-CRS system was able to differentiate the densities of the two gases. Identical experiments conducted using a bare QCM showed that the mass flow rates had negligible effects on the QCM resonance frequency response. Thus, it is evident that a coupled resonance phenomenon plays a significant role in enabling the QCM to be sensitive to small mass changes caused by differences in flow rates. We propose that the QCM-CRS system can be used as a new class of mass flow sensing element, especially for flow measurement in vacuum processing systems. [ABSTRACT FROM AUTHOR]

In this study, laser powder bed fusion (LPBF) was used for the fabrication of an interstitial-strengthened high entropy alloy (iHEA), Fe 49.5 Mn 30 Co 10 Cr 10 C 0.5 (at.%). The as-fabricated iHEA possesses excellent strength-ductility synergy during tensile loading, with fracture strength reaching up to 1109 MPa at 37% engineering strain. Electron backscatter diffraction (EBSD) and high energy synchrotron X-ray diffraction were used to evaluate the microstructural characteristics of the material. In-situ EBSD analysis during uniaxial tensile testing was performed to unveil the deformation mechanisms. Moreover, crystallographic orientation-specific micropillar compression tests were conducted to determine how the grain deformation characteristics differ between orientations. Due to the activation of multiple slip systems and the homogeneous plastic flow, the [111] orientation demonstrated a higher yield strength and continuous work hardening rate. This research helps in clarifying grain orientation-specific contributions to the bulk mechanical response of additively manufactured HEA. [Display omitted] [ABSTRACT FROM AUTHOR]

One of the main interests in developing microfluidic platforms is the lab-on-a-chip (LOC) applications, including the use of microdevices for the culture of prokaryotic and eukaryotic cells for different applications. In this context, the trapping and control of Micro/nano-scale bubbles have been considered as it becomes a field of growing concern addressing many challenges in LOC applications. In the present work, we present a novel microfluidic bioreactor based on the micropillar design that reduces stresses caused by bubbles on the cell growth in the microchip. The combination of one chamber with 3-pillars and 10-pillars design with the channel heights of 270 µm and 2 mm were evaluated. Computational fluid dynamics simulations (CFD) were conducted to investigate the flow dynamics in the new designs. Numerical values of velocity were compared with those obtained by experimental flow tests to evaluate the performance of the proposed microdevice. Finally, the functionality of the new milli-bioreactor design was validated by culturing human induced pluripotent stem cells (hiPSC) for 5 days. Cell growth, viability and sustain pluripotency were successfully proved using a new platform architecture. This multidisciplinary research provides new insights into the chemical engineering and operability of micro and milli-bioreactors with prospects for future industrial applications. [Display omitted] • The milli-bioreactor allows the control of bubbles without affecting the system. • CFD and experimental tests were used to characterize the designs. • The 3 and 10 pillars designs supported the growth of hiPSC stem cells for 5 days. • hiPSCs cells in the milli-bioreactor expressed the pluripotent genes Oct4, Nanog and Sox2. [ABSTRACT FROM AUTHOR]

The article presents a study focusing on organic field-effect transistors (OFETs) and the use of dewetting liquid-bridges to assemble nanoparticles on the interface. Topics discussed include the fabrication of large-scaled polymer microwires in OFETs; the arrangement of polymer molecules within the confined spaces; and the fabrication of thin film transistors in the study.

Experiments by He et al. [J.Y. He, Z.L. Zhang, M. Midttun, G. Fonnum, G.I. Modahl, H. Kristiansen, and K. Redford. Size effect on mechanical properties of micron-sized PS-DVB polymer particles. Polymer 2008, 49(18), 3993] have indicated that polymers exhibit enhancement of strength at length scales of the order of microns. This is surprising since size effects, widely reported for FCC metals, owe their origin to the presence of crystalline defects, particularly dislocations. On the other hand, polymers being a material of choice in microfabrication, these results assume technological importance. In this work, we conduct controlled experiments on polystyrene (PS) micropillars to ascertain whether they exhibit size effects. The pillars are microfabricated and hence free of beam damage. The experimental load displacement curves obtained from microcompression experiments are matched with computer simulations on similar samples using a well-calibrated constitutive model. Our results demonstrate significant intrinsic size effect on the yield strength, though effects of size on rehardening response turned out to be an experimental artifact. [ABSTRACT FROM AUTHOR]

The plastic behavior of silicate glasses has emerged as a central concept for the understanding of glass strength. Here we address the issue of shear-hardening in amorphous silica. Using in situ SEM mechanical testing with a high stiffness device, we have been able to compress silica pillars to large strains while directly monitoring radial strain. The sizeable increase of pillar cross-section during compression directly demonstrates the significant role of homogeneous shear flow. From the direct evaluation of the cross section, we have also measured true stress-strain curves. The results demonstrate that silica predominantly experiences plastic shear flow but that there is no shear-induced hardening. The consequence of this finding for our understanding of glass strength is discussed. [ABSTRACT FROM AUTHOR]

We here report an improved experimental technique for the determination of Young׳s modulus and uniaxial strength of extracellular bone matrix at the single micrometer scale, giving direct access to the (homogeneous) deformation (or strain) states of the tested samples and to the corresponding mechanically recoverable energy, called potential or elastic energy. Therefore, a new protocol for Focused Ion Beam milling of prismatic non-tapered micropillars, and attaching them to a rigid substrate, was developed. Uniaxial strength turns out as at least twice that measured macroscopically, and respective ultimate stresses are preceded by hardening elastoplastic states, already at very low load levels. The unloading portion of quasi-static load–displacement curves revealed Young׳s modulus of 29 GPa in bovine extracellular bone matrix. This value is impressively confirmed by the corresponding prediction of a multiscale mechanics model for bone, which has been comprehensively validated at various other observation scales, across tissues from the entire vertebrate animal kingdom. [ABSTRACT FROM AUTHOR]

Anti-icing abilities are achieved on surfaces of micropillar arrays with nanohairs that are fabricated by methods of soft replication and crystal growth, i.e., different micropillar arrays with the similar nanohairs, different nanohairs with the same micropillar arrays. It is demonstrated that an optimal micropillar array with nanohairs contributes an excellent anti-icing or antifogging property at low temperature below zero. As a result, the longest icing delay time is achieved effectively up to ≈9839 s at −10 °C on the optimal surface. As for the optimal surface in humidity, the condensed droplets merge into each other, and meanwhile jump off easily. Accordingly, a largest dry area is up to ≈90.5% at −5 °C in ≈1020 s after breeze action. It is attributed to the stability of less liquid-solid fraction on an optimal surface under low temperature, in addition to cooperation between micropillar arrays and nanohairs in sizes. This finding provides an insight into the design of structure size on micro-nanostructured surface for anti-icing/antifogging ability effectively, which can be extended into the applications in some surfaces of systems, e.g., microdevices worked in cold or humid environment. [ABSTRACT FROM AUTHOR]