9 research outputs found
The Acoustic Hologram and Particle Manipulation with Structured Acoustic Fields
This book shows how arbitrary acoustic wavefronts can be encoded in the thickness proïŹle of a phase plate - the acoustic hologram. The workïŹow for design and implementation of these elements has been developed and is presented in this work along with examples in microparticle assembly, object propulsion and levitation in air. To complement these results, a fast thermographic measurement technique has been developed to scan and validate 3D ultrasound fields in a matter of seconds
Acoustic Hologram Enhanced Phased Arrays for Ultrasonic Particle Manipulation
The ability to shape ultrasound fields is important for particle manipulation, medical therapeutics, and imaging applications. If the amplitude and/or phase is spatially varied across the wave front, then it is possible to project âacoustic images.â When attempting to form an arbitrary desired static sound field, acoustic holograms are superior to phased arrays due to their significantly higher phase fidelity. However, they lack the dynamic flexibility of phased arrays. Here, we demonstrate how to combine the high-fidelity advantages of acoustic holograms with the dynamic control of phased arrays in the ultrasonic frequency range. Holograms are used with a 64-element phased array, driven with continuous excitation. Movement of the position of the projected hologram via phase delays that steer the output beam is demonstrated experimentally. This allows the creation of a much more tightly focused point than with the phased array alone, while still being reconfigurable. It also allows the complex movement at a water-air interface of a âphase surferâ along a phase track or the manipulation of a more arbitrarily shaped particle via amplitude traps. Furthermore, a particle manipulation device with two emitters and a single split hologram is demonstrated that allows the positioning of a âphase surferâ along a one-dimensional axis. This paper opens the door for new applications with complex manipulation of ultrasound while minimizing the complexity and cost of the apparatus
Structured light enables biomimetic swimming and versatile locomotion of photoresponsive soft microrobots.
Microorganisms move in challenging environments by periodic changes in body shape. In contrast, current artificial microrobots cannot actively deform, exhibiting at best passive bending under external fields. Here, by taking advantage of the wireless, scalable and spatiotemporally selective capabilities that light allows, we show that soft microrobots consisting of photoactive liquid-crystal elastomers can be driven by structured monochromatic light to perform sophisticated biomimetic motions. We realize continuum yet selectively addressable artificial microswimmers that generate travelling-wave motions to self-propel without external forces or torques, as well as microrobots capable of versatile locomotion behaviours on demand. Both theoretical predictions and experimental results confirm that multiple gaits, mimicking either symplectic or antiplectic metachrony of ciliate protozoa, can be achieved with single microswimmers. The principle of using structured light can be extended to other applications that require microscale actuation with sophisticated spatiotemporal coordination for advanced microrobotic technologies.This work was in part supported by the European Research Council under the ERC Grant agreements 278213 and 291349, and the DFG as part of the project SPP 1726 (microswimmers, FI 1966/1-1). SP acknowledges support by the Max Planck ETH Center for Learning Systems.This is the author accepted manuscript. The final version is available from Nature Publishing Group via http://dx.doi.org/10.1038/nmat456
Periodic Mesoporous Organosilica Nanorice
A periodic mesoporous organosilica (PMO) with nanorice morphology was successfully synthesized by a template assisted solâgel method using a chain-type precursor. The PMO is composed of D and T sites in the ratio 1:2. The obtained mesoporous nanorice has a surface area of 753 m2 gâ1, one-dimensional channels, and a narrow pore size distribution centered at 4.3 nm. The nanorice particles have a length of ca. 600 nm and width of ca. 200 nm
Simple Systematic Synthesis of Periodic Mesoporous Organosilica Nanoparticles with Adjustable Aspect Ratios
One-dimensional periodic mesoporous organosilica (PMO) nanoparticles with tunable aspect ratios are obtained from a chain-type molecular precursor octaethoxy-1,3,5-trisilapentane. The aspect ratio can be tuned from 2:1 to >20:1 simply by variation in the precursor concentration in acidic aqueous solutions containing constant amounts of triblock copolymer Pluronic P123. The mesochannels are highly ordered and are oriented parallel to the longitudinal axis of the PMO particles. No significant SiâC bond cleavage occurs during the synthesis according to29Si MAS NMR. The materials exhibit surface areas between 181 and 936 m2 gâ1
Wireless Acoustic-Surface Actuators for Miniaturized Endoscopes
Endoscopy
enables minimally invasive procedures in many
medical fields, such as urology. However, current endoscopes are normally
cable-driven, which limits their dexterity and makes them hard to
miniaturize. Indeed, current urological endoscopes have an outer diameter
of about 3 mm and still only possess one bending degree-of-freedom.
In this article, we report a novel wireless actuation mechanism that
increases the dexterity and that permits the miniaturization of a
urological endoscope. The novel actuator consists of thin active surfaces
that can be readily attached to any device and are wirelessly powered
by ultrasound. The surfaces consist of two-dimensional arrays of microbubbles,
which oscillate under ultrasound excitation and thereby generate an
acoustic streaming force. Bubbles of different sizes are addressed
by their unique resonance frequency, thus multiple degrees-of-freedom
can readily be incorporated. Two active miniaturized devices (with
a side length of around 1 mm) are demonstrated: a miniaturized mechanical
arm that realizes two degrees-of-freedom, and a flexible endoscope
prototype equipped with a camera at the tip. With the flexible endoscope,
an active endoscopic examination is successfully performed in a rabbit
bladder. The results show the potential medical applicability of surface
actuators wirelessly powered by ultrasound penetrating through biological
tissues