Bioinspired 3D-printed Piezoelectric Device for Acoustic Frequency Separation

Development of 3D-printed devices, sensors, and actuators has become increasingly popular in recent years due to low cost, rapid production, and device personalization. This personalization process allows development of devices with unique physical properties and phenomena that enhance the desired properties of the 3D-printed part. Biomimetics is a commonly used technique to develop 3D-printed devices, as organisms present in nature can provide smart and simple solutions to complex problems across a wide range of applications. Locust ears have a simple tympanic membrane with varying thicknesses that allows frequency selection, as well as presenting nonlinear phenomena. This acoustic frequency selection assists the insect in predation and swarming. In this work we present the development of a polymeric material that has been used to 3D-print a frequency selective piezoelectric sensor inspired by the locust's tympanic membrane. 3D-printing of functional sensors and/or actuators provides an insight into the development and enhancement of polymer-based science, with exciting and promising potential for the near future

Airborne broad-beam emitter from a capacitive transducer and a cylindrical structure

Beamwidth broadening of an ultrasonic air-coupled transducer is performed by an emitter constituted of an electrostatic transducer and of a cylinder with an opening at the top covering the surface of the transducer. The acoustic emission is thus forced through a hole smaller than the diameter of the transducer’s surface. In particular, a cylinder with an upper diameter of 10mm and a height of 5mm ensures the beam pattern of the final emitter is broad across a wide frequency range. Sound attenuation is reduced and lobes in the transducer’s beam pattern are cancelled. Beam broadening can improve range estimation techniques and ultrasonic sonar as a wider area can be inspected with one emission with no need for scanning

Mechanical phase shifters for coherent acoustic radiation in the stridulating wings of crickets: the plectrum mechanism

Male crickets produce stridulatory songs using engaged tegmina (forewings): a plectrum on the left sweeps along a tooth row on the right. During stridulation, the plectrum moves across the teeth and vibrations are amplified by the surrounding cells and veins, resonating at the frequency of tooth impacts. The advance of the plectrum on the file is controlled by an escapement mechanism so that passing each single tooth generates one wave of a highly tonal signal. Both tegmina must oscillate in phase to avoid destructive interference. But as each plectrum-tooth contact begins, the right and left tegmina react in opposite oscillatory directions. A mechanical phase shifter is part of the left tegmen and compensates to achieve wing oscillation synchrony. We use a new technique to simulate plectrum-on-file interactions: in combination with laser vibrometry, this technique assessed plectrum mechanics in the cricket Gryllus bimaculatus. Using an excised teneral file, shaped like a partial gear and moved by a motor, and a microscan Doppler laser vibrometer, plectrum and left-tegmen mechanics were explored. The results show that plectrum and harp oscillate with a phase difference of ca. 156 deg., a shift rather than a complete phase inversion (180 deg.). This phase shift occurs at the site of a large wing vein (possibly A3). Plectrum and harp vibrate with similar fundamental frequency, therefore, plectrum torsion resonant frequency is important for maintaining vibration coherence. The mechanical aspects involved in this partial phase inversion are discussed with respect to the escapement mechanism. The plectrum mechanics and its implications in katydid stridulation are also considered

A new cellular electret sensor-actuator

The new form of electret, EFoam, has a high degree of sensitivity, and can be manufactured with varying stiffness and shape. Initial investigations indicate sensitivity comparable to that of other commercially available piezoelectric polymers. Further work is needed to explore the maximum sensitivity attainable. Due to the nature of manufacture, EFoam can be made both in conventional sheet form, and bulk, three-dimensional shapes. The molding procedure used, combined with some post-processing, could confer EFoam with complex shapes, endowing different areas of the structure with heterogeneous and controllable mechanical properties. Finally, the resonant behavior (and so stiffness) of EFoam can be altered as a function of a dc-offset voltage applied

Picometre scale mechanics in the cicada ear

Female cicadas use sound to select their mate from a chorus of singing males. Cicadas have tympanal ears, with both the ear's tympanal membrane, and constituent tympanal ridge, acting as acousto-mechanical transducers and frequency filters. Within the ear the tympanal ridge is mechanically connected to a large number of mechanosensory neurons via a cuticular extension known as the tympanal apodeme. Using microscanning laser Doppler vibrometry, the in vivo vibrations of the tympanal apodeme of female Cicadatra atra have been measured for the first time as they respond to the motion of the tympanal membrane driven by sound. These precise measurements reveal that the tympanal membrane's nanometre motion is over a magnitude greater than that of the tympanal apodeme at the point where the neurons attach. Further, the tympanal apodeme acts as an additional mechanical frequency filter, enhancing the frequency filtering of the tympanal ridge, to narrow the frequency band of vibration at the mechanoreceptor neurons solely to that of the male calling song. This study thus enhances our understanding of the mechanical links between the external ear of the cicada and its sensory cells. Poster Session held on Tuesday 30th June 2009 at the Annual Meeting of the Society for Experimental Biology, 28th June-1st July, Glasgow, UK

Tympanal travelling waves in migratory locusts

Hearing animals, including many vertebrates and insects, have the capacity to analyse the frequency composition of sound. In mammals, frequency analysis relies on the mechanical response of the basilar membrane in the cochlear duct. These vibrations take the form of a slow vibrational wave propagating along the basilar membrane from base to apex. Known as von Békésy’s travelling wave, this wave displays amplitude maxima at frequency-specific locations along the basilar membrane, providing a spatial map of the frequency of sound – a tonotopy. In their structure, insect auditory systems may not be as sophisticated as those of mammals, yet some are known to perform sound frequency analysis. In the desert locust, this analysis arises from the mechanical properties of the tympanal membrane. In effect, the spatial decomposition of incident sound into discrete frequency components involves a tympanal travelling wave that funnels mechanical energy to specific tympanal locations, where distinct groups of mechanoreceptor neurones project. Notably, observed tympanal deflections differ from those predicted by drum theory. Although phenomenologically equivalent, von Békésy’s and the locust’s waves differ in their physical implementation. von Békésy’s wave is born from interactions between the anisotropic basilar membrane and the surrounding incompressible fluids, whereas the locust’s wave rides on an anisotropic membrane suspended in air. The locust’s ear thus combines in one structure the functions of sound reception and frequency decomposition

The nanomechanics of mechanosensory neurones in vivo

The ability to detect and process sound is a sense particularly important in many animals, including insects, playing a key role in predator, prey and mate detection. Acute hearing, both in the sense of extreme sensitivity to sound and sharp frequency selectivity, relies on the active participation of auditory mechanoreceptors. In insects, active auditory mechanics was first demonstrated in mosquitoes, whereby auditory sensitivity is enhanced by the action and reaction of mechanosensory neurones to sound-induced vibrations. The mosquito's auditory neurones can generate motions that mechanically drive the antenna and tune it to biologically relevant sounds. The mechanosensory neurones are capable of detecting exquisitely small mechanical displacements, down to 100 picometres. In the mosquito's Johnston's organ (300 µm in diameter) there is a high density of these neurones (16 000 units). The mechanical response of the mechanoreceptors was measured in vivo using an atomic force microscope, in response to stimulation of the external antenna. The work establishes the link between the previously measured non-linearities of the mosquito's antennal vibrations and the nanoscale mechanics of the mechanosensory neurones

A network model to assist ‘design for remanufacture’ integration into the design process

Remanufacturing is the process of returning a used product to a like-new condition with a warranty to match. It is widely recognised as an environmentally preferable end-of-life strategy for many products, as it is a process that saves materials from landfill and retains more intrinsic energy than similar end-of-life strategies such as recycling or repair. The concept of ‘design for remanufacture’ (DfRem) originates from the understanding that decisions made during the design process may have a considerable effect upon the efficiency and effectiveness of the remanufacturing process. Much of the DfRem literature to date has focused upon the identification of technical DfRem factors (such as material choice or fastening methods), and the subsequent development of design methods and tools. However, the literature has overlooked how DfRem practices may be integrated into a company design process, and has not considered the operational factors that may influence DfRem integration decision-making and practice. This paper presents the findings from industrial case study research with three original equipment manufacturers (OEMs) from the UK mechanical industry sector. The research has identified significant external and internal operational factors that influence DfRem integration, including management commitment, OEM-remanufacturer relationships and designer motivation. This paper also presents a ‘DfRem integration network model’ which maps the identified relationships between the various operational factors, providing practitioners with an enhanced understanding of DfRem and a portfolio of options when seeking to integrate DfRem into the design process

Hearing in tsetse flies? morphology and mechanics of a putative auditory organ

Tympanal hearing organs are widely used by insects to detect sound pressure. Such ears are relatively uncommon in the order Diptera, having only been reported in two families thus far. This study describes the general anatomical organization and experimentally examines the mechanical resonant properties of an unusual membranous structure situated on the ventral prothorax of the tsetse fly, Glossina morsitans (Diptera: Glossinidae). Anatomically, the prosternal membrane is backed by an air filled chamber and attaches to a pair of sensory chordotonal organs. Mechanically, the membrane shows a broad resonance around 5.3-7.2 kHz. Unlike previously reported dipteran tympana, a directional response to sound was not found in G. morsitans. Collectively, the morphology, the resonant properties and acoustic sensitivity of the tsetse prothorax are consistent with those of the tympanal hearing organs in Ormia sp. and Emblemasoma sp. (Tachinidae and Sarcophagidae). The production of sound by several species of tsetse flies has been repeatedly documented. Yet, clear behavioural evidence for acoustic behaviour is sparse and inconclusive. Together with sound production, the presence of an ear-like structure raises the enticing possibility of auditory communication in tsetse flies and renews interest in the sensory biology of these medically important insects

Sexual dimorphism in auditory mechanics: tympanal vibrations of cicada orni

In cicadas, the tympanum is anatomically intricate and employs complex vibrations as a mechanism for auditory frequency analysis. Using microscanning laser Doppler vibrometry, the tympanal mechanics of Cicada orni can be characterized in controlled acoustical conditions. The tympanum of C. orni moves following a simple drum-like motion, rather than the travelling wave found in a previous study of Cicadatra atra. There is a clear sexual dimorphism in the tympanal mechanics. The large male tympanum is unexpectedly insensitive to the dominant frequency of its own calling song, possibly a reflection of its dual purpose as a sound emitter and receiver. The small female tympanum appears to be mechanically sensitive to the dominant frequency of the male calling song and to high-frequency sound, a capacity never suspected before in these insects. This sexual dimorphism probably results from a set of selective pressures acting in divergent directions, which are linked to the different role of the sexes in sound reception and production. These discoveries serve to indicate that there is far more to be learnt about the development of the cicada ear, its biomechanics and evolution, and the cicada's acoustic behaviour