Achim Wixforth

Achim Wixforth
Universität Augsburg | UNA · Experimental Physics 1

Professor

About

377
Publications
31,468
Reads
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8,923
Citations
Additional affiliations
November 2000 - August 2007
Advalytix AG, Brunnthal Germany
Position
  • Founder and CTO
January 1990 - January 2014
University of California, Santa Barbara
Position
  • guest scientist
Description
  • Various stays over the years
January 1989 - January 1990
University of California, Santa Barbara
Position
  • Research Assistant
Description
  • post doctoral position

Publications

Publications (377)
Preprint
Full-text available
The interaction between surface acoustic waves (SAWs) and spin waves (SWs) in a piezoelectric-magnetic thin film heterostructure yields potential for the realization of novel microwave devices and applications in magnonics. In the present work, we characterize magnetoacoustic waves in three adjacent magnetic micro-stripes made from CoFe+Ga, CoFe, a...
Article
With a view on adding to their use in trace gas sensing, we perform a combined experimental and theoretical study of the change of the conductivity of a metal organic framework (iron (1,2,3)-triazolate, Fe(ta)2) with the uptake of chemically inert gases. To align our first-principles calculations with experimental measurements, we perform an ensemb...
Article
Full-text available
Direct conversion of X-ray irradiation using a semiconductor material is an emerging technology in medical and material sciences. Existing technologies face problems, such as sensitivity or resilience. Here, we describe a novel class of X-ray sensors based on GaN thin film and GaN/AlGaN high-electron-mobility transistors (HEMTs), a promising enabli...
Article
Full-text available
Membrane-associated enzymes have been found to behave differently qualitatively and quantitatively in terms of activity. These findings were highly debated in the 1970s and many general correlations and reaction specific models have been proposed, reviewed, and discarded. However, new biological applications brought up the need for clarification an...
Article
Full-text available
With the development of ink jet printers or spotters for biological applications, the control size and homogeneity of small fluids as well as their successful deposition on various substrates has gained significant importance. We study the impingement process of such small droplets onto a solid substrate and investigate their evaporation and drying...
Article
Full-text available
A fluid-independent ultrasonic approach for flow determination in microchannels in the harsh environment of an ultra high pressure liquid chromatography (UHPLC) system is presented. Ultrasonic waves in the fluid are excited by separate media surface acoustic waves (SAW) of Rayleigh-Wave type. The LiNbO3 SAW chip being equipped with interdigitated t...
Article
Full-text available
Here, we present a novel approach for the transient permeabilization of cells. We combined laminar shear flow in a microchannel with chaotic advection employing surface acoustic waves. First, as a fundamental result on the one hand, and as a kind of reference measurement for the more complex acoustofluidic approach on the other hand, we studied the...
Article
In this study, we present proof of concept for an x-ray detector. The hybrid device consists of a synthetic single crystal diamond in mechanical contact with a piezoelectric lithium niobate surface acoustic wave (SAW) delay line. Upon x-ray irradiation, the diamond crystal experiences a change in conductivity, which, in turn, very sensitively influ...
Article
We study the interaction of surface acoustic waves (SAWs) with spin waves (SWs) in a Co40Fe40B20/Au/Ni81Fe19 system composed of two ferromagnetic layers separated by a nonmagnetic Au spacer layer. Because of interlayer magnetic dipolar coupling between the two ferromagnetic layers, a symmetric and an antisymmetric SW mode form, which both show a hi...
Article
We study the interaction of Rayleigh and shear horizontal surface acoustic waves (SAWs) with spin waves in thin Ni films on a piezoelectric LiTaO3 substrate, which supports both SAW modes simultaneously. Because Rayleigh and shear horizontal modes induce different strain components in the Ni thin films, the symmetries of the magnetoelastic driving...
Article
A Love-wave based biosensor is introduced for analyzing a standardized wound healing assay by observing cell growth and quantifying cell detachment processes. Utilizing the piezoelectric material LiTaO3 36° XY-cut with a thin SiO2-cover layer, shear horizontal surface acoustic waves (SAW) are excited and detected by a set of Interdigital Transducer...
Article
Full-text available
TiO2 is the most widely used photocatalyst for water splitting reaction to generate clean fuel of hydrogen, but the energy conversion efficiency of it is still low, mainly due to the easy recombination of photo-generated electron-hole pairs. In order to promote the efficiency of the catalyst, a Surface Acoustic Waves assisted catalyst is presented...
Preprint
We study the interaction of Rayleigh and shear horizontal surface acoustic waves (SAWs) with spin waves in thin Ni films on a piezoelectric LiTaO$_3$ substrate, which supports both SAW modes simultaneously. Because Rayleigh and shear horizontal modes induce different strain components in the Ni thin films, the symmetries of the magnetoelastic drivi...
Article
We report on in vitro wound-healing and cell-growth studies under the influence of radio-frequency (rf) cell stimuli. These stimuli are supplied either by piezoactive surface acoustic waves (SAWs) or by microelectrode-generated electric fields, both at frequencies around 100 MHz. Employing live-cell imaging, we studied the time- and power-dependent...
Article
We study the interaction of surface acoustic waves with spin waves in ultrathin CoFeB/Pt bilayers. Because of the interfacial Dzyaloshinskii–Moriya interaction (DMI), the spin wave dispersion is nondegenerate for oppositely propagating spin waves in CoFeB/Pt. In combination with the additional nonreciprocity of the magnetoacoustic coupling itself,...
Preprint
We study the interaction of surface acoustic waves with spin waves in ultra-thin CoFeB/Pt bilayers. Due to the interfacial Dzyaloshinskii-Moriya interaction (DMI), the spin wave dispersion is non-degenerate for oppositely propagating spin waves in CoFeB/Pt. In combination with the additional nonreciprocity of the magnetoacoustic coupling itself, hi...
Article
For Plasmodium falciparum related malaria (B50), one of the outstanding host factors for the development of severe disease is the ABO blood group of malaria patients, where blood group O reduces the probability of severe disease as compared to individuals of groups A, B, or AB. In this report, we investigate the stability of rosette aggregates in m...
Article
Full-text available
Unilamellar lipid vesicles can serve as model for protocells. We present a vesicle fission mechanism in a thermal gradient under flow in a convection chamber, where vesicles cycle cold and hot regions periodically. Crucial to obtain fission of the vesicles in this scenario is a temperature-induced membrane phase transition that vesicles experience...
Article
Full-text available
One of the main challenges in endoprosthesis surgeries are implant-associated infections and aseptic-loosenings, caused by wear debris. To combat these problems, the requirements to surfaces of endoprostheses are wear-resistance, low cytotoxicity and antimicrobial efficacy. We here present antimicrobial coatings with a smart, adaptive release of me...
Article
Full-text available
Today, surface acoustic waves (SAWs) and bulk acoustic waves are already two of the very few phononic technologies of industrial relevance and can been found in a myriad of devices employing these nanoscale earthquakes on a chip. Acoustic radio frequency filters, for instance, are integral parts of wireless devices. SAWs in particular find applicat...
Article
Full-text available
Today, surface acoustic waves (SAWs) and bulk acoustic waves are already two of the very few phononic technologies of industrial relevance and can been found in a myriad of devices employing these nanoscale earthquakes on a chip. Acoustic radio frequency filters, for instance, are integral parts of wireless devices. SAWs in particular find applicat...
Article
A metal–organic framework (MFU‐4) with ultra‐narrow pores has been integrated on a specially designed sensor, with response in the range of milliseconds, and based on surface acoustic waves (SAWs). Selective diffusion of D2 in H2/D2 mixtures below 64 K has been observed due to kinetic quantum‐sieving. More information can be found in the Communicat...
Article
The separation of deuterium from hydrogen still remains a challenging and industrially relevant task. Compared to traditional cryogenic methods for separation, based on different boiling points of H2 and D2, the use of ultramicroporous materials offers a more efficient alternative method. Due to their rigid structures, permanently high porosity, tu...
Article
Full-text available
We report a comprehensive study on the impact of the structural properties of radial GaAs-Al0.3Ga0.7As nanowire-quantum well heterostructure on the optical recombination dynamics and electrical transport properties and we emphasize particularly the role of the commonly observed variations of the quantum well thickness of different facets. Typical t...
Article
Full-text available
Investigating cell adhesion behavior on biocompatible surfaces under dynamic flow conditions is not only of scientific interest but also a principal step towards development of new medical implant materials. Driven by the improvement of the measurement technique for microfluidic flow fields (scanning particle image velocimetry, sPIV), a semi-automa...
Article
For the investigation of cell-cell interaction in general and for neural communication and future applications of neural networks, a controllable and well-defined network structure is crucial. We here propose the implementation of an acoustically driven system for tunable and deliberate stimulation and manipulation of cell growth on a chip. This pi...
Article
In the context of cell–nanoparticle interaction, the question arises how ions influence the adhesion between nanoparticles and cell membranes. Here, the question is addressed how the adhesion energy between supported lipid bilayers and silica particles helps to understand nanoparticle uptake. Supported lipid bilayers on mica and glass substrates se...
Article
Full-text available
Wide-passband interdigital transducers are employed to establish a stable phase lock between a train of laser pulses emitted by a mode-locked laser and a surface acoustic wave generated electrically by the transducer. The transducer design is based on a multiharmonic split-finger architecture for the excitation of a fundamental surface acoustic wav...
Article
Full-text available
A quantum dot is created within a suspended nanobridge containing a two-dimensional electron gas. The electron current through this dot exhibits well-pronounced Coulomb blockade oscillations. When surface acoustic waves (SAW) are driven through the nanobridge, Coulomb blockade peaks are shifted. To explain this feature, we derive the expressions fo...
Article
Full-text available
Wide passband interdigital transducers are employed to establish a stable phase-lock between a train of laser pulses emitted by a mode-locked laser and a surface acoustic wave generated electrically by the transducer. The transducer design is based on a multi-harmonic split-finger architecture for the excitation of a fundamental surface acoustic wa...
Article
Diamond-like carbon (DLC) is known to be a versatile coating material, being found in a wide variety of surface engineering applications. In this study, we produced DLC coatings by ion irradiation and thus reconstruction of a thin polymer film. This procedure leads to a thin diamond-like carbon layer which is characterized by its high hardness. Due...
Chapter
Full-text available
We study the dynamics and formation of differently ordered lateral phases of interfacial lipid layers for two types of lipid systems, a vesicle-supported bilayer and a Langmuir–Blodgett monolayer, both in experiment and by simulation. Similarly, we investigate the dynamics of objects embedded in a simpler interface given by an air–water surface and...
Article
Observation of the kinetics and measurement of the activation energies for gas diffusion in porous materials requires very fast and sensitive sensors. In this work, thin films of metal–organic frameworks (MOFs) with different pore sizes are grown on a surface acoustic wave (SAW) substrate, resulting in very sensitive and specific sensor systems for...
Article
Cells experience forces if subjected to laminar flow. These forces, mostly of shear force character, are strongly dependent not only on the applied flow field itself but also on hydrodynamic effects originating from neighboring cells. This particularly becomes important for the interpretation of data from in vitro experiments in flow chambers witho...
Article
We have measured both the current-voltage ($I_\mathrm{SD}$-$V_\mathrm{GS}$) and capacitance-voltage ($C$-$V_\mathrm{GS}$) characteristics of a $\mathrm{MoS_2-LiNbO_3}$ field effect transistor. From the measured capacitance we calculate the electron surface density and show that its gate voltage dependence follows the theoretical prediction resultin...
Article
Full-text available
Cell adhesion processes are of ubiquitous importance for biomedical applications such as optimization of implant materials. Here, not only physiological conditions such as temperature or pH, but also topographical structures play crucial roles, as inflammatory reactions after surgery can diminish osseointegration. In this study, we systematically i...
Article
Full-text available
Fifteen years ago, surface acoustic waves (SAW) were found to be able to drive fluids and numerous applications in microfluidics have been developed since. Here, we review the progress made and report on new approaches in setting-up microfluidic, continuous flow acoustic mixing. In a microchannel, chaotic advection is achieved by generation of a SA...
Article
The aim of this study was the synthesis of hard and low-abrasive novel implant materials with built-in time-dependent antibacterial properties, which can be tailored by a well-defined time-dependent and finite release of metal ions. We were able to synthesize such smart implant surfaces employing ECR (electron cyclotron resonance)-plasma on typical...
Article
Full-text available
In this work we investigate the interaction between endothelial cells and nanoparticles emitted by catalytic converters. Although catalyst-derived particles are recognized as growing burden added to environmental pollution, very little is known about their health impact. We use platinum-decorated ceria nanoparticles as model compounds for the actua...
Article
A low cost version to enable high temperature MAS NMR experiments at temperatures of up to 700 °C and spinning speeds of up to 10 kHz is presented. The method relies on inductive heating using a metal coated rotor insert. The metal coating is accomplished via a two step process involving physical vapor deposition and galvanization.
Article
A coupled quantum dot--nanocavity system in the weak coupling regime of cavity quantumelectrodynamics is dynamically tuned in and out of resonance by the coherent elastic field of a $f_{\rm SAW}\simeq800\,\mathrm{MHz}$ surface acoustic wave. When the system is brought to resonance by the sound wave, light-matter interaction is strongly increased by...
Article
A novel, ultrasound based approach for the dynamic stimulation and promotion of tissue healing processes employing surface acoustic waves (SAW) on a chip is presented for the example of osteoblast-like SaOs-2 cells. In our investigations, we directly irradiate cells with SAW on a SiO2 covered piezoelectric LiNbO3 substrate. Observing the temporal e...
Article
Full-text available
Background Rosetting is associated with severe malaria and a primary cause of death in Plasmodium falciparum infections. Detailed understanding of this adhesive phenomenon may enable the development of new therapies interfering with rosette formation. For this, it is crucial to determine parameters such as rosetting and parasitaemia of laboratory s...
Article
Piezoelectric surface acoustic waves are employed to induce radio frequency spatio-temporal dynamics of photogenerated electrons and holes in the GaAs core of individual GaAs/AlGaAs core/shell semiconductor nanowires. Comparison of the time-dependent interband optical recombination to numerical simulations allow to determine the charge carrier tran...
Article
Full-text available
The implant-bone interface is the scene of competition between microorganisms and distinct types of tissue cells. In the past, various strategies have been followed to support bony integration and to prevent bacterial implant-associated infections. In the present study we investigated the biological properties of diamond-like carbon (DLC) surfaces...
Article
Full-text available
We demonstrate continuous, passive, and label-free sorting of different in vitro cancer cell lines (MV3, MCF7, and HEPG2) as model systems for circulating tumor cells (CTCs) from undiluted whole blood employing the non-inertial lift effect as driving force. This purely viscous, repulsive cell-wall interaction is sensitive to cell size and deformabi...
Article
Full-text available
Lithium niobate is the archetypical ferroelectric material and the substrate of choice for numerous applications including surface acoustic wave radio frequencies devices and integrated optics. It offers a unique combination of substantial piezoelectric and birefringent properties, yet its lack of optical activity and semiconducting transport hampe...
Article
Full-text available
Two-dimensional photonic crystal membranes provide a versatile planar architecture for integrated photonics to control the propagation of light on a chip employing high quality optical cavities, waveguides, beamsplitters or dispersive elements. When combined with highly non-linear quantum emitters, quantum photonic networks operating at the single...
Article
Full-text available
The concept of Fourier synthesis is heavily used in both consumer electronic products and fundamental research. In the latter, pulse shaping is key to dynamically initializing, probing and manipulating the state of classical or quantum systems. In NMR, for instance, shaped pulses have a long-standing tradition and the underlying fundamental concept...
Article
Full-text available
Static conditions represent an important shortcoming of many in vitro experiments on the cellular uptake of nanoparticles. Here, we present a versatile microfluidic device based on acoustic streaming induced by surface acoustic waves (SAWs). The device offers a convenient method for introducing fluid motion in standard cell culture chambers and for...