Movable Finger Research Articles

A new species of Chaerilus Simon, 1877 (Scorpiones, Chaerilidae) from China

A new species, Chaerilus mainlingensis sp. nov., is described from Xizang in China. The present new species is distinguished from the congeners by chela with width/length ratio more than 2.4, seven rows of denticles on fixed and movable fingers of pedipalp chelae, three or four pectinal teeth in females, and almost smooth teguments of the seventh sternite and all of the metasomal segments.

Computational simulation for MEMS combdrive levitation using FEM

Generally the levitation value is a very important design parameter for a comb drive, because the levitation effect will seriously downgrade the performance and reliability of electrostatic MEMS devices. Thus an accurate electrostatic and structural analysis is essential. Besides the distance traveled by the movable finger of MEMS comb drive, studies of the effect of gap sizes between comb drive fingers and ground plane and between movable and fixed fingers for levitation are also needed. By way of the finite element method, an accurate electrostatic field under diverse gap sizes considering the fringing electric field around the edges of the fixed and movable fingers of comb drive can be obtained. The subsequent levitation and strain analyses for an MEMS comb drive can be also implemented more precisely. Results show that the levitating displacement and strain of the movable finger are dependent on the distance traveled. The smaller the gap between comb drive fingers and ground plane, the larger the structural response of the movable finger. In addition, the levitation also becomes more predominant as the gap between the movable and fixed fingers decreases.

Specialized shell-breaking crab claws in Cretaceous seas

Here we report on a large brachyuran crab species from the Late Cretaceous of Mexico that has claws indicative of highly specialized shell-breaking behaviour. This crab possessed dimorphic claws (the right larger than the left), armed with several broad teeth, including a curved tooth structure found at the base of the movable finger of the right claw. The curved tooth is similar to the one observed on claws of many living durophagous crabs that use it as a weapon to peel, crush or chip the edges of hard-shelled prey, particularly molluscs. These morphological traits suggest that specialized shell-breaking crab predators had evolved during the Cretaceous, which contradicts previous findings supporting an Early Cenozoic origin for specialized shell crushers within the brachyuran clade.

Fabrication of a polymer-based torsional vertical comb drive using a double-side partial exposure method

A novel approach which uses a double-side partial exposure method to fabricate a polymer-based torsional vertical comb drive (VCD) with thick photoresist AZ9260® as the structural material is proposed in this paper. Front-side partial exposure defines the height of the fixed lower fingers, and back-side partial exposure creates the suspending space of the upper fingers, where the overlap and self-alignment between fingers can easily be achieved in this way. It does not need any sacrificial layer and etching process. A metal layer is finally deposited on the structural surface by a sputtering system for suitable electric conductivity to activate the polymer torsional VCD. The finite element method is used here to simulate the capacitance at different finger positions, and twelfth-order polynomial curve fitting is performed to obtain capacitance as a function of finger displacement. Then the rotation angle can be calculated analytically with the capacitance function. Also, the static deflection and dynamic response of polymer torsional VCDs are characterized experimentally, where the dimensions of the torsion plate are 300 µm wide and 360 µm long with movable fingers of length 100 µm; the torsion spring is 60 µm long and 4 µm wide. Both have a thickness of 31 µm, and the initial overlap is 11 µm in depth and 80 µm in length between the lower and upper fingers. By comparing the simulated and experimental results, the feasibility of the proposed fabrication method of polymer torsional VCDs is verified with a measured rotation angle of 2.31° under a driving voltage of 158.3 V.

One new species of scorpion belonging to the genus Euscorpiops Vachon, 1980 from South China (Scorpiones: Euscorpiidae, Scorpiopinae)

A new species of scorpion, Euscorpiops yangi sp. nov. (Euscorpiidae) is described from Maguang County, Yunnan Province, China. The new species can be characterized by 18 external trichobothria (5 eb, 2 esb, 2 em, 4 est, 5 et) and 9 to 10 ventral trichobothria in the pedipalp patella; a narrow and elongated chela with a length vs width ratio equal to 3.4 on males and 3.3 on female; cheliceral movable finger with 5 basal teeth on ventral edge.

Design and synthesis of wide tuning range variable comb drive MEMS capacitors

PurposeTo present a general synthesis method in the design of variable comb drive MEMS capacitors which can provide specified capacitance versus position profiles while give large tuning range.Design/methodology/approachBy carefully choosing design parameters and constraint conditions, the design process is implemented as the solution of a constraint optimization problem. An electric field analysis software based on the finite element method and an optimization software based on the evolutionary stochastic search are chosen to work together to implement the system.FindingsThe results verify that the shape of a variable MEMS capacitor has a great influence on the capacitance versus distance profile and demonstrates that a specific geometry of the MEMS capacitor can be found to match a desired capacitance‐distance profile.Research limitations/implicationsThe analytical expression for the capacitance formed between the fixed and the movable fingers is somewhat inaccurate. The results are not compared to measurement because no device has been fabricated.Practical implicationsA very successful numerical simulation example and guidance for MEMS designers to develop MEMS devices with variable electrode shapes.Originality/valueThis paper proposes a systematic way for the design of MEMS tunable capacitors with variable shape. The approach can be used to design MEMS devices with variable electrode shapes to satisfy specific requirements.

Laterally actuated multicontact MEMS relay fabricated using MetalMUMPS process: experimental characterization and multiscale contact modeling

Multicontact MEMS relays laterally actuated using electrostatic comb-drive actuators are reported. The relay consists of a movable main beam anchored to the substrate using two identical folded suspension springs. Multicontact RF ports consist of five movable fingers connected to the movable main beam and six fixed fingers anchored to the substrate. Comb-drive actuators located at the top and bottom ends of the main beam enable bidirectional actuation of the RF contacts. The MEMS relays were fabricated using the MetalMUMPs process, which uses 20-µm-thick electroplated nickel as the structural layer. A 3-µm-thick gold layer was electroplated at the electrical contact surfaces. An example MEMS relay with planar contacts of area 80 µm×20 µm and a spacing of 10 µm between the movable and fixed contacting surfaces is discussed. The overall size of the relay is approximately 3 mm×3 mm. "Resistance versus applied voltage" characteristics of the MEMS relay have been measured for applied DC bias voltages in the range of 172 V to 220 V. A multiscale rough surface contact model was used to estimate the actual electrical contact resistance versus applied force curve of these devices. The multiscale model showed good qualitative agreement with the experimental measurements but requires more refinement to achieve good quantitative agreement.

The scorpion of Montecristo, Euscorpius oglasae Di Caporiacco, 1950, stat. nov. (Scorpiones, Euscorpiidae): a paleo-endemism of the Tuscan Archipelago (northern Tyrrhenian, Italy)

The scorpion of Montecristo Island (Tuscan Archipelago, Italy): Euscorpius carpathicus oglasae Di Caporiacco, 1950, is a poorly known taxon. We redescribe and illustrate the insular endemism of E. c. oglasae for the first time, and elevate this subspecies to the rank of species following a thorough study of the comparative morphology of 372 specimens (including 7 related taxa). Euscorpius oglasae stat. nov. is an oligotrichous form that differs from the related species by the inner proximal surface of pedipalp movable finger, with a reduced lobe and a slightly swollen telson vesicle in males. Attention was given to the analysis of the hemispermatophore and peg sensilla of pectens. The hemispermatophore is small, with the basal lobe bearing a very short spine. We also discuss aspects of the ecology, conservation and biogeography of this species. To cite this article: V. Vignoli et al., C. R. Biologies 330 (2007).

Study of the electrical contact resistance of multi-contact MEMS relays fabricated using the MetalMUMPs process

The reliability of electrostatically actuated ohmic contact type MEMS relays has been investigated. Multi-contact MEMS relays laterally actuated using electrostatic comb-drive actuators were used in this study. The MEMS relays were fabricated using the MetalMUMPs process, which uses a 20 µm thick electroplated nickel as the structural layer. A 3 µm thick gold layer was electroplated on the electrical contact surfaces. An example MEMS relay with planar contacts of area 80 µm × 20 µm and spacing of 10 µm between the movable and fixed contacting surfaces is discussed. The overall size of the relay is approximately 3 mm × 3 mm. ‘Resistance versus applied voltage’ characteristics have been studied. At an applied dc bias voltage of 120 V, the movable fingers make initial contact with the fixed fingers. The ‘resistance versus applied voltage’ characteristics have been measured for an applied bias voltage in the range of 172–220 V. Reliability testing of the MEMS relay up to one million actuations has been carried out and the resistance degradation with actuation cycles is discussed.

A new species of Periclimenes Costa, 1844 (Crustacea: Decapoda: Palaemonidae) from the Caribbean coast of Quintana Roo, Mexico, and a key for the “iridescens” complex

A new species of pontoniine shrimp, Periclimenes siankaanensis, is described from the Mexican Caribbean coast. The new species shares morphological features with P. patae Heard & Spotte,1991, P. antipathophilus Spotte, Heard & Bubucis, 1994, and P. mclellandi Heard & Spotte, 1997, all species belonging to the “iridescens” complex, and with P. platalea Holthuis, 1951, of the tropical east Atlantic. Periclimenes siankaanensis differs from P. patae and P. mclellandi by its large size, pereopods 3–5 with 2 or 3 spines on propodal inner margin and the presence of bifid dactyl, and is distinguished from P. antipathophilus by its smaller size, entire endite on the second maxilla, pereopods 2 of same shape, and by the lack of tooth on the movable finger. In addition, P. siankaanensis can be separated immediately from P. platalea by having the second pereopods equal in shape and length, and bifid dactyl present on pereopods 3–5. Periclimenes siankaanensis inhabits shallow water Thalassia testudinum seagrass meadows and sandy bottoms, while the other species here compared are associated with gorgonians in deeper zones.

Vestigial serrula in scorpion genera Paravaejovis, , Smeringurus and Vejovoidus (Scorpiones: Vaejovidae)

The presence of vestigial serrula on the ventral edge of the cheliceral movable finger is established for vaejovid genera Paravaejovis, Paruroctonus, Smeringurus, and Vejovoidus. Detailed descriptions and SEM images illustrating the various manifestations of this interesting cheliceral structure are provided for many species of these four genera. A brief systematic overview of this structure as it exists in Recent scorpions is also presented.

A pulse-operating electrostatic microactuator for bi-stable latching

We propose a novel microactuator with spade comb fingers designed for pulse-operating bi-stability. When the broad parts of the movable comb fingers are positioned facing the broad parts of the fixed comb fingers, the direction of electrostatic force is inward, like a conventional comb actuator. However, the spade comb fingers generate outward electrostatic force when the broad end part of each movable comb finger is positioned facing the narrow part of the fixed comb fingers. The proposed spade comb is combined with chevron-type springs to effectively operate the actuator in a bi-stable latching. For a driving input, a fast electrical pulse was applied to one driving electrode, and its operability was investigated in terms of voltage magnitude and duty time. Through an FEA (finite element analysis) and a numerical analysis, the dynamic characteristics were theoretically investigated including transient time response and operable bi-stability, which were compared with the experimental values. The bi-stable actuator was fabricated using a silicon-on-insulator (SOI) wafer, and successfully operated by a pulse voltage input of 55 V with a duty time of 0.32 ms.

Computational study of the effect of finger width and aspect ratios for the electrostatic levitating force of MEMS combdrive

Since the width ratio between movable and fixed fingers, and the aspect ratio between the height and width of fingers, can play very important roles for combdrive levitation control, computational study of variations in those parameters for electrostatic levitating force acting on the movable finger is indispensable for MEMS performance. For diverse finger width and aspect ratios of MEMS combdrive design, the BEM has become a better method than the domain-type FEM because BEM can provide a complete solution in terms of boundary values only, with substantial saving in modeling effort. DBEM still has some advantages over conventional BEM for singularity, so the DBEM was used to simulate the fringing of field around the edges of the fixed finger and movable finger of MEMS combdrive for diverse finger width and aspect ratios. Results show that the less the finger width ratio is, the larger the levitating force acting is. Furthermore, the levitating force becomes more dominant as the aspect ratio increases, but it will be kept constant while the aspect ratio becomes larger.

Description of a new species of Compsobuthus Vachon, 1949 (Scorpiones: Buthidae) from southern Iran

A new species of Compsobuthus Vachon, 1949 is described; the specimen was collected near Persepolis in Fars Province, south-western Iran. Compsobuthus petriolii n. sp. belongs to the “werneri” group on the basis of the rows of denticles on the movable fingers, which appears as external accessory granules. The new species is of a slender appearance with particularly elongated pedipalp chelae, and is easy to distinguish from all congeneric taxa. Meristic data, drawings, and an identification key are provided.

Descrição de uma nova espécie de Rhopalurus thorell, 1876 (scorpiones: Buthidae) do nordeste brasileiro

Rhopalurus guanambiensis n.sp. é descrita de Guanambi, Estado da Bahia, nordeste do Brasil. A nova espécie aproxima-se de R. lacrau Lourenço & Pinto-da-Rocha, 1997 (Itaeté, Estado da Bahia) por apresentar o mesmo número de séries de grânulos no dedo móvel da quela do pedipalpo, igual quantidade de carenas nos segmentos metasomais I, III, IV e V e pelo tamanho do corpo semelhante; aproxima-se de R. crassicauda Di Caporiacco, 1947 (Estado da Roraima) por apresentar o mesmo número de carenas nos segmentos metasomais I, II, IV e V, pela coloração mais escura dos dois últimos segmentos metasomais, que são dilatados e por apresentar aproximadamente o mesmo tamanho. Distingue-se de R. lacrau pela coloração diferente da carapaça, mesosoma e dos segmentos metasomais IV-V, maior número de dentes pectínios e pela presença de dez carenas no segmento metasomal II; de R.crassicauda, devido ao menor número de séries de grânulos no dedo móvel da quela do pedipalpo, maior número de dentes pectíneos, presença de oito carenas no segmento metasomal III e por apresentar um tubérculo subaculear acentuado no telson e carenas do segmento V do metasoma vestigiais. O macho de R. guanambiensis distingue-se da fêmea pela mão mais robusta e pela dilatação dos dois últimos segmentos do metasoma. A descrição desta espécie amplia para nove o número de espécies que ocorrem no Brasil.

Fabrication technique for microelectromechanical systems vertical comb-drive actuators on a monolithic silicon substrate

This article presents a technique to fabricate a microelectromechanical systems vertical comb-drive actuator on a monolithic silicon substrate. This technique employs only two photomasks. The first photomask defines all the critical patterns, including a set of movable upper hollow comb fingers, a set of fixed lower comb fingers, and a suspension spring to avoid the alignment problem and maintain a small finger gap. The second photomask selectively covers the upper fingers to obtain the released upper hollow fingers. The vertical comb-drive actuator is fabricated by deep reactive ion etching process on a monolithic silicon wafer using these uniquely designed photomasks to avoid the residual stress and stiction problems. Different lateral gaps between the adjacent lower solid and upper hollow fingers are obtained with various finger widths. The height of the comb fingers is 10.0 μm. The vertical offset between the two sets of comb fingers can be adjusted by controlling the process conditions. Both symmetric and asymmetric staggered comb-drives are achieved through process modifications. The mechanism of notching effect is discussed and addressed by multiple spacer oxide deposition. Silicon residue effect, which occurs during the lowering down etching process, is investigated from the fabrication aspect and resolved by combining isotropic and anisotropic etching processes. This kind of vertical comb-drive actuator can be widely applied in optical switches, scanning micromirrors, and sensors.

Numerical studies of variations in the gap and finger width ratio and travelled distance for the driving force of a radio-frequency microelectromechanical system device using the dual boundary element method

For the comb-drive design of microelectromechanical systems (MEMSs), the driving force due to the electrostatic field is very important, and an accurate electrostatic analysis is essential and indispensable. For various gaps, finger width ratios and travelled distances of the comb drive of MEMSs, the dual boundary element method (DBEM) has become a better method than the domain-type finite element method because the DBEM can provide a complete solution in terms of boundary values, with substantial saving in modelling effort. In this article, the DBEM is used to simulate the fringing field around the edges of the fixed and movable fingers of the comb drive of an MEMS for diverse design cases, and many electrostatic problems for typical comb drive designs of MEMSs are analysed, investigated and compared with a widely used approximate method. Results show that the driving force is obviously dependent on the travelled distance, and the approximate method cannot work well for all travelled positions because there is an apparent error (not less than 10 per cent), especially at the beginning and ends of the range of travel. In addition, the smaller the gap between movable and fixed fingers, the larger the driving force is, and the error of approximate method also becomes more and more predominant as the gap decreases. The results also demonstrate that the difference between the DBEM and the approximate method effect due to finger width ratio is very small. Using the DBEM presented in this article, an accurate and reasonable electrostatic field can be obtained, and the follow-up control method of driving force for the comb drive of an MEMS can be implemented more precisely.

Computational study of variations in gap size for the electrostatic levitating force of MEMS device using dual BEM

For MEMS combdrive performance, the calculation of levitating force due to electrostatic field is very important, and an accurate electrostatic analysis is essential. Because the gap size between combdrive fingers and ground plane or movable finger and fixed finger, plays a very important role for levitation, a study of the effect of gap size variation is indispensable. For diverse gaps of MEMS comdrive design, the dual BEM (DBEM) has become a better method than the domain-type FEM because DBEM can provide a complete solution in terms of boundary values only, with substantial saving in modeling effort, hence the DBEM was used to simulate the fringing of field around the edges of the fixed finger and movable finger of MEMS combdrive for diverse gap size. Results show that the less the gaps between combdrive fingers and ground plane are, the larger the levitating force acting on the movable finger is. In addition, the levitating force becomes more predominant as the gaps between movable finger and fixed finger decrease. By way of DBEM presented in this article, an accurate electrostatic field can be obtained, and the follow-up control method of levitation force for MEMS combdrive can be implemented more precisely.

An alternatively efficient method (DBEM) for simulating the electrostatic field and levitating force of a MEMS combdrive

For MEMS combdrive design, the reduction of levitating force due to electrostatic fields is very important, and an accurate electrostatic analysis is essential and indispensable. For diverse MEMS combdrive designs, the boundary element method (BEM) has become a better method than the domain-type finite element method (FEM) because the BEM can provide a complete solution in terms of boundary values only, with substantial saving in modeling effort. Since dual BEM (DBEM) has some advantages over conventional BEM for a singularity, the DBEM was used to simulate the fringing of field around the edges of the fixed fingers and movable fingers of MEMS combdrives for diverse design cases. A number of electrostatic problems for typical MEMS combdrive designs were analyzed to check the efficiency and validity of this new technique. It is found that the numerical results computed by coarse mesh DBEM match the reference data from a large refined mesh FEM very well, and the accuracy and performance of DBEM are also better than those of conventional BEM for solving the electric intensity field of MEMS combdrives. By way of the DBEM presented in this paper, an accurate and reasonable electrostatic field can be obtained, and the follow-up control method of levitating force for the MEMS combdrive can be implemented more precisely.

DIMORPHISM OF CHELIPEDS IN THE FIDDLER CRAB, UCA ARCUATA

Dimorphism of chelipeds due to regeneration occurs both in males and females of Uca arcuata (De Haan, 1833). After the loss of the large cheliped in males, a new large claw is regenerated at its original place, and no transformation of handedness occurs. However, the regenerated chelipeds have no distinct tooth on either the movable or immovable fingers. Females have a pair of teeth on their chelipeds but the regenerated cheliped has no teeth. Young crabs of early stages, both males and females, possess two small, symmetrical chelipeds with teeth, but regenerated chelipeds have no teeth. It is assumed that both males and females of U. arcuata have a special morphogenetic mechanism at the base of the cheliped. The mechanism starts to work after the loss of the cheliped and transforms the regenerating cheliped into the toothless type.