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1.
Rehabilitation (Stuttg) ; 63(2): 100-106, 2024 Apr.
Artigo em Alemão | MEDLINE | ID: mdl-38244536

RESUMO

PURPOSE: Dysfunctional breathing patterns (DAM) are deviations from physiologic breathing patterns. DAM seem to be associated with lower asthma control. To date, it is unclear what effect inpatient rehabilitation can have on this problem. The aim of this work is to investigate the effect of pulmonary rehabilitation (PR) on DAM. METHODS: The data are based on a randomized controlled trial with a waiting control group. The intervention group (IG) received PR 4 weeks after application approval and the control group (KG) after 5 months. Dysfunctional breathing was assessed by Nijmegen-Questionnaire (NQ). Values ≥ 23 points indicate an existing DAM. Values at the end of rehabilitation (T2) and after three months (T3) were compared (analysis of covariance). Supplemental moderator analysis was performed to examine whether the effect of PR was related to baseline NQ scores. RESULTS: Significant differences in NQ score are found between IG (n=202) and KG (n=210) at T2 (AMD=10.5; 95%CI [9; 12]; d=1.4; p<0.001) and at T3 (AMD=5.8; 95%CI [4.3; 7.3]; d=0.8; p<0.001). There is an interaction effect between the difference in NQ score between the groups at T2 and baseline at T0 (b=5.6; 95%CI [2.2; 11.9]; p<0.001). At T3, this interaction effect was no longer detectable (b=4.5; 95%CI [-3.1; 14.1]; p=807). CONCLUSION: Inpatient, multimodality, and interdisciplinary PR is associated with significant and clinically relevant improvement in DAM both at discharge and 3 months later. In the short term, patients with existing DAM benefit more from PR than patients without DAM.


Assuntos
Asma , Qualidade de Vida , Humanos , Alemanha , Asma/complicações , Asma/reabilitação , Pacientes Internados
2.
Med Probl Perform Art ; 37(3): 176-191, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-36053495

RESUMO

BACKGROUND: Recently, Wolf et al. proposed a novel, marker-based method to analyze the three-dimensional upper-body kinematics of high string players for clinical application. The method provides an objective evaluation of high string players' motor strategies, especially in the shoulder complex, by distinguishing between the scapulothoracic (ST) and glenohumeral (GH) joints, while minimizing skin movement artifacts, marker occlusions, and limitations due to instrument placement. Nevertheless, reproducibility of kinematic measurements is crucial for clinical applications. The aim of this study was to assess the method's reproducibility in terms of reliability and repeatability. METHODS: One healthy professional violinist underwent a total of nine bowing trials in three different laboratory sessions. Each trial was conducted by one of two different examiners. A biomechanical model was applied to motion capture data of the pelvis, thorax, spine, and head, as well as both upper limbs (consisting of the scapula, upper arm, forearm and hand). Reproducibility was assessed by calculating inter- and intra-tester, inter-session, and intra-subject measurement errors for each rotational degree of freedom in the upper-body segments and joints. FINDINGS: Small measurement errors were accepted to be good indicators for reproducibility. Intra- and inter-tester errors were found to be small (< 3° for the most part). Both inter-session and intra-subject repeatability were found to be larger (< 5° for the most part). INTERPRETATION: This study generally showed the novel, marker-based method to have good reproducibility for a healthy violinist. This indicates that the proposed method is a reliable tool for quantifying upper-body movements during violin playing across subjects, examiners, laboratories, and motion capture systems.


Assuntos
Braço , Escápula , Fenômenos Biomecânicos , Humanos , Movimento , Amplitude de Movimento Articular , Reprodutibilidade dos Testes
3.
Med Probl Perform Art ; 34(4): 179-190, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31800669

RESUMO

AIMS: High string players (violin and viola) often suffer from musculoskeletal disorders. Although 3D motion analysis has proved helpful in diagnosing different musculoskeletal syndromes and identifying injurious movement patterns in violin and viola performance, more detailed analyses of upper body movement strategies and especially of the shoulder complex have not yet been recorded. The use of spherical surface markers on some anatomical landmarks is, however, inappropriate when an instrument is being played. The aim of this study was to develop and evaluate a novel marker-based method for analyzing upper body kinematics of high string players using conditions specific to violin and viola playing. METHODS: A custom upper body marker set was developed and a biomechanical model applied to 3D motion capture data of the pelvis, thorax, spine, head, and both upper limbs (scapula, upper arm, forearm, hand) of 12 professional violinists, to assess its clinical feasibility. FINDINGS: Lumbar and thoracic spine, thorax, neck, and left upper limb were quite static, while extensive motion occurred in the right upper limb. Most rotation angles showed a reasonable intersubject variability except for glenohumeral and wrist joints. Significant differences were observed between G- and D-string bowing, especially in the left wrist and right shoulder joints. INTERPRETATION: This study suggests that the proposed method is a valid tool for quantifying upper body movements in violin and viola performance. With the extended upper body model, it will improve understanding of the motor strategies adopted by high string players and may contribute to injury prevention, diagnosis, and treatment.


Assuntos
Fenômenos Biomecânicos , Movimento , Música , Braço , Estudos de Viabilidade , Humanos , Amplitude de Movimento Articular
4.
Med Probl Perform Art ; 33(3): 166-174, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-30204822

RESUMO

AIM: In this prospective longitudinal study, the physical and psychological health status of music students is assessed at the beginning of their university music study and tracked over time. Analysis strategies and interim results from the first-year cohort, including 1-year incidences, monthly prevalences, and predictors of developing musculoskeletal health complaints (MHC), are presented. METHODS: This prospective longitudinal study is calculated to enlist a total sample of 370 participants, including musicians and non-musicians, over 5 years. Baseline measurements include a self-designed questionnaire, core strength endurance, hypermobility, finger-floor-distance, motor control, mechanosensitivity, health-related quality of life (SF36), and stress and coping inventory (SCI). The occurrence of MHC is based on monthly online questionnaires. RESULTS: The first-year subcohort enrolled 33 music students and 30 non-music control students. The mean monthly completion rate for the questionnaire was 55.7±8.7%. At baseline, music students showed significantly more stress symptoms, reduced physical function¬ing, and increased bodily pain compared to control students. The 1-year incidence of MHC was 59% for music students and 44% for controls. Risk factors for MHC included being a music student, previous pain, reduced physical functioning, stress symptoms, reduced emotional functioning, and mechanosensitivity. Being a music student, physical functioning, sleep duration, positive thinking, and general mechanosensitivity had a predictive ability of 0.77 (ROC curve) for MHC. CONCLUSION: A total of 63 students enrolled in the first cohort is in line with the precalculated sample size. This prospective study design enables the measurement of MHC incidence and provides insight into mechanisms in the development of MHC among music students, including the interaction of physical, psychological, and psychosocial factors.


Assuntos
Indicadores Básicos de Saúde , Doenças Musculoesqueléticas/epidemiologia , Música , Doenças Profissionais/epidemiologia , Estudantes/estatística & dados numéricos , Adaptação Psicológica , Feminino , Alemanha/epidemiologia , Humanos , Incidência , Estudos Longitudinais , Masculino , Medição da Dor , Resistência Física , Estudos Prospectivos , Qualidade de Vida , Projetos de Pesquisa , Fatores de Risco , Estresse Psicológico/epidemiologia , Inquéritos e Questionários , Universidades , Adulto Jovem
5.
Med Probl Perform Art ; 33(3): 147-155, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-30204820

RESUMO

BACKGROUND: Muscle fatigue seems to be a risk factor in the development of performance-related musculoskeletal disorders (PRMDs) in musicians, but it is unclear how muscle activity characteristics change between musicians with and without PRMDs over a prolonged playing period. PURPOSE: To investigate muscle activity patterns in muscles of the arms, shoulder, and back of high string musicians during prolonged performance. METHODS: Fifteen professional or university high string musicians were divided into PRMD and non-PRMD groups. All musicians played a chromatic scale, then an individual "heavy" piece for 1 hr, and finally the chromatic scale again. Surface electromyography (sEMG) data were recorded from 16 muscles of the arm, shoulder, and trunk on both sides of the body. Two parameters were analyzed: the percentage load in relation to the respective maximum force during the chromatic scale, and the low-frequency spectrum to determine the fatigue behavior of muscles during the 1-hr play. RESULTS: Changes in muscle activation patterns were observed at the beginning and end of the trial duration; however, these varied depending on whether musicians had PRMDs or no PRMDs. In addition, low-frequency spectrum changes were observed after 1 hr of playing in the PRMD musicians, consistent with signs of muscular fatigue. CONCLUSION: Differences in muscle activity appear between high string musicians with and without PRMDs as well as altered frequency spectrum shifts, suggesting possible differential muscle fatigue effects between the groups. The applied sEMG analysis proved a suitable tool for detailed analysis of muscle activation characteristics over prolonged playing periods for musicians with and without PRMDs.


Assuntos
Fadiga Muscular , Doenças Musculoesqueléticas/etiologia , Doenças Musculoesqueléticas/fisiopatologia , Música , Doenças Profissionais/etiologia , Doenças Profissionais/fisiopatologia , Adulto , Braço/fisiopatologia , Dorso/fisiopatologia , Eletromiografia , Feminino , Alemanha , Humanos , Masculino , Medição da Dor , Fatores de Risco , Ombro/fisiopatologia , Inquéritos e Questionários , Fatores de Tempo
6.
J Nanobiotechnology ; 11: 21, 2013 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-23842114

RESUMO

BACKGROUND: For the design and characterization of ultrasonic particle manipulation devices the pressure field in the fluid cavity is of great interest. The schlieren method provides an optical tool for the visualization of such pressure fields. Due to its purely optical nature this experimental method has got some unique advantages compared to methods like particle tracking. RESULTS: A vertical schlieren setup and an investigation with the same of a mm-sized chamber used to agglomerate particles are presented here. The schlieren images show a two-dimensional representation of the whole pressure distribution recorded simultaneously with a good resolution in time. The gained description of the pressure field is shown to be in agreement with a numerical simulation. Thermal effects as well as streaming effects are shown. CONCLUSIONS: The results show the great potential of schlieren visualization to investigate ultrasonic particle manipulation devices. Visualized are pressure fields, acoustic streaming, temperature effects and effects caused by fluid volumes of different density.


Assuntos
Fenômenos Ópticos , Tamanho da Partícula , Ultrassom/instrumentação , Ultrassom/métodos , Acústica , Simulação por Computador , Pressão , Fatores de Tempo
7.
Equine Vet J ; 55(3): 515-523, 2023 May.
Artigo em Inglês | MEDLINE | ID: mdl-35831933

RESUMO

BACKGROUND: Selective laryngeal reinnervation using the first and second cervical nerve (C1C2) is a treatment option for recurrent laryngeal neuropathy that aims to restore the function of the cricoarytenoideus dorsalis (CAD) muscle. Despite the technique's satisfying success rate, it has several limitations. These triggered the search for another potential donor nerve that could reduce CAD muscle fatigue and shorten rehabilitation. The ventral branch of the spinal accessory nerve, providing motor innervation to the sternomandibularis (SM) muscle, was identified as a potentially well-adapted nerve. OBJECTIVES: To gather normative data from SM muscle activity induced by physiological spinal accessory nerve stimulation at rest and during exercise, and to determine SM muscle activity and fibre type recruitment relative to posture, gait and respiratory cycle. STUDY DESIGN: Clinical observational study. METHODS: Surface electromyography (EMG) of the SM muscle was performed in nine horses: trained warmbloods, Thoroughbreds and Standardbreds. Signals were recorded in different feeding postures and at exercise, which included standardised treadmill exercise tests, lungeing and ridden work. RESULTS: Timing of the SM muscle contraction coincided with inspiration at gallop. Intra-individual mean SM muscle activity increased with exercising speed (four times higher in Thoroughbreds at gallop than walk and seven times higher in Standardbreds at high-speed trot than walk). Moreover, the SM muscle was strongly activated at rest when the horse was grazing (seven times more than when it was eating out of a hay net or stable feeder). Frequency domain analysis revealed a predominant type I muscle fibre recruitment during feeding and at exercise (type I muscle fibre activity was at least 2.5 times higher than type II muscle fibre activity). MAIN LIMITATIONS: Lack of reference data on equine EMG. CONCLUSIONS: This study confirmed the potentially advantageous properties of the spinal accessory nerve for laryngeal reinnervation.


Assuntos
Nervo Acessório , Músculos Laríngeos , Animais , Cavalos , Músculos Laríngeos/inervação , Músculos , Eletromiografia/veterinária , Marcha
8.
J Man Manip Ther ; 30(3): 180-191, 2022 06.
Artigo em Inglês | MEDLINE | ID: mdl-35045803

RESUMO

BACKGROUND: Orofacial pain is a complex disabling condition. Multimodal physical therapy intervention may be helpful, yet studies of such approaches are not available and are the basis of this study. OBJECTIVE: To identify whether combined orofacial manual therapy, pain neuroscience education, graded motor imagery, and face emotional expression training has an impact on orofacial pain and associated features. DESIGN: Mixed-methods case series report. METHODS: Eight subjects (five females) with predominant chronic unilateral face pain (mean duration 7.3 years) were given six individualized treatment sessions and a home program. The primary outcome was orofacial pain, while secondary outcomes were depression, quality of life, alexithymia, 2-point discrimination (TPD), laterality and emotional recognition, as well as qualitative analysis were evaluated post intervention. RESULTS: Following the intervention orofacial pain intensity significantly reduced (p = 0.03) from 3.0 (0.53) to 2.2 (1.75) on the Graded Chronic Pain Status questionnaire. As well, secondary outcome measures depression, alexithymia, TPD, and quality of life also significantly improved. Changes were not significant in aspects of facial perception. Qualitative analysis of perception of therapy is discussed. CONCLUSION: Multimodal therapy had a positive outcome in terms of improvement in unilateral persistent facial pain, depression score, facial body perception and quality of life, and pain in people with chronic unilateral facial pain. Based on the qualitative analysis of their perception of the therapy, multimodal therapy had beneficial effects through increased motivation and joy to exercise.


Assuntos
Dor Crônica , Manipulações Musculoesqueléticas , Encéfalo , Dor Crônica/psicologia , Dor Crônica/terapia , Dor Facial/terapia , Feminino , Humanos , Percepção , Qualidade de Vida
9.
J Bodyw Mov Ther ; 28: 376-390, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34776167

RESUMO

OBJECTIVE: Brass players are exposed to high musculoskeletal strains during their instrumental play. Various assessments can be used to measure these strains, whereby a targeted therapy can also be supported. The aim of this study was to review literature concerning assessments used in quantitatively based studies about the analysis of musculoskeletal loads of brass players. DATA SOURCES: The Cochrane Library, PubMed, CINAHL, PEDro as well as the journal "Medical Problems of Performing Artists" were searched for relevant studies. STUDY SELECTION: Two reviewers independently applied the inclusion and exclusion criteria to select potential studies. A third reviewer was involved in the case of discrepancies. DATA EXTRACTION: Two reviewers independently extracted the data. DATA SYNTHESIS: A total of 73 studies conducted between 2004 and 2019 were included. Within a total of 30 studies, 18 assessments could be found that collect 2-dimensional or 3-dimensional kinematic data using video- or image-based analysis of posture, sonographic, optoelectronic and various electromagnetic systems. In 7 studies kinetic data were measured by force-transducers, pressure platforms, stabilizer and dynamometer. Fifteen studies used clinical examinations and additional assessments to screen individual body regions and 9 studies derived electromyography measurements from a total of 25 muscles. Thirty-one partially validated questionnaires were used to record musculoskeletal pain of brass players. CONCLUSIONS: A variety of assessments can be used to optimize analysis and treatment procedures in research and clinical work. Future studies should both examine quality criteria of the various assessment methods and validate clinical examinations and questionnaires.


Assuntos
Dor Musculoesquelética , Música , Fenômenos Biomecânicos , Cobre , Humanos , Postura , Zinco
10.
Mol Ecol ; 19(23): 5204-15, 2010 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-20964758

RESUMO

Despite the advantage of avoiding the costs of sexual reproduction, asexual vertebrates are very rare and often considered evolutionarily disadvantaged when compared to sexual species. Asexual species, however, may have advantages when colonizing (new) habitats or competing with sexual counterparts. They are also evolutionary older than expected, leaving the question whether asexual vertebrates are not only rare because of their 'inferior' mode of reproduction but also because of other reasons. A paradigmatic model system is the unisexual Amazon molly, Poecilia formosa, that arose by hybridization of the Atlantic molly, Poecilia mexicana, as the maternal ancestor, and the sailfin molly, Poecilia latipinna, as the paternal ancestor. Our extensive crossing experiments failed to resynthesize asexually reproducing (gynogenetic) hybrids confirming results of previous studies. However, by producing diploid eggs, female F(1) -hybrids showed apparent preadaptation to gynogenesis. In a range-wide analysis of mitochondrial sequences, we examined the origin of P. formosa. Our analyses point to very few or even a single origin(s) of its lineage, which is estimated to be approximately 120,000 years old. A monophyletic origin was supported from nuclear microsatellite data. Furthermore, a considerable degree of genetic variation, apparent by high levels of clonal microsatellite diversity, was found. Our molecular phylogenetic evidence and the failure to resynthesize the gynogenetic P. formosa together with the old age of the species indicate that some unisexual vertebrates might be rare not because they suffer the long-term consequences of clonal reproduction but because they are only very rarely formed as a result of complex genetic preconditions necessary to produce viable and fertile clonal genomes and phenotypes ('rare formation hypothesis').


Assuntos
Evolução Molecular , Hibridização Genética , Poecilia/genética , Reprodução Assexuada/genética , Animais , DNA Mitocondrial/genética , Feminino , Genética Populacional , Masculino , Repetições de Microssatélites , Filogenia , Dinâmica Populacional , Análise de Sequência de DNA
11.
BMJ Open ; 9(11): e032340, 2019 11 25.
Artigo em Inglês | MEDLINE | ID: mdl-31772099

RESUMO

OBJECTIVES: To develop a time-efficient motor control (MC) test battery while maximising diagnostic accuracy of both a two-level and three-level classification system for patients with non-specific low back pain (LBP). DESIGN: Case-control study. SETTING: Four private physiotherapy practices in northern Germany. PARTICIPANTS: Consecutive males and females presenting to a physiotherapy clinic with non-specific LBP (n=65) were compared with 66 healthy-matched controls. PRIMARY OUTCOME MEASURES: Accuracy (sensitivity, specificity, Youden index, positive/negative likelihood ratio, area under the curve (AUC)) of a clinically driven consensus-based test battery including the ideal number of test items as well as threshold values and most accurate items. RESULTS: For both the two and three-level categorisation system, the ideal number of test items was 10. With increasing number of failed tests, the probability of having LBP increases. The overall discrimination potential for the two-level categorisation system of the test is good (AUC=0.85) with an optimal cut-off of three failed tests. The overall discrimination potential of the three-level categorisation system is fair (volume under the surface=0.52). The optimal cut-off for the 10-item test battery for categorisation into none, mild/moderate and severe MC impairment is three and six failed tests, respectively. CONCLUSION: A 10-item test battery is recommended for both the two-level (impairment or not) and three-level (none, mild, moderate/severe) categorisation of patients with non-specific LBP.


Assuntos
Dor Lombar/diagnóstico , Dor Lombar/fisiopatologia , Movimento , Medição da Dor/métodos , Adulto , Estudos de Casos e Controles , Feminino , Alemanha , Humanos , Dor Lombar/classificação , Masculino , Pessoa de Meia-Idade , Destreza Motora , Transtornos dos Movimentos/diagnóstico , Modalidades de Fisioterapia , Curva ROC
12.
Musculoskelet Sci Pract ; 37: 1-7, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-29879488

RESUMO

Many musicians suffer from playing-related musculoskeletal disorders (PRMDs) however many of the epidemiological surveys on PRMD do not utilize evaluated self-report instruments, especially as a tool to assess musculoskeletal pain intensity and pain interference in terms of function and psychosocial constructs. The aim of this study was to translate and cross-culturally adapt the Musculoskeletal Pain Intensity and Interference Questionnaire for Musicians (MPIIQM) into German, and validate it among a population of professional orchestral musicians. The translated and cross-culturally adapted German version of the questionnaire was sent to a total of 367 professional orchestral musicians in Germany who were eligible for the study. Of this total, 124 musicians responded to the questionnaire. The psychometric evaluation showed a clear two dimensionality namely "pain intensity" and "pain interference". Internal consistency was very high for both the "pain intensity" and "pain interference" dimensions as well as for the complete scale. The values for the Intraclass Correlation Coefficient for the test-retest reliability indicated good to excellent repeatability. The subscales of MPIIQM showed strong correlation with the Brief Pain Inventory (BPI) and the shorter version of Disabilities of the Arm, Shoulder and Hand (QuickDash) and low correlation with the Fatigue Severity Scale (FSS). These results were as expected, confirming the good construct validity of the MPIIQM. The German Version of the MPIIQM (MPIIQM-G) and the original version have similarly high qualities and thus the MPIIQM-G represents a useful self-report instrument for the measurement and evaluation of musculoskeletal pain intensity and pain interference for professional orchestral musicians.


Assuntos
Dor Musculoesquelética/diagnóstico , Doenças Profissionais/diagnóstico , Medição da Dor/métodos , Psicometria , Adulto , Feminino , Alemanha , Humanos , Masculino , Pessoa de Meia-Idade , Música , Reprodutibilidade dos Testes , Índice de Gravidade de Doença , Inquéritos e Questionários , Traduções
13.
Ultrason Sonochem ; 20(2): 655-66, 2013 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-23058229

RESUMO

A model was developed to determine the local changes of concentration of particles and the formations of bands induced by a standing acoustic wave field subjected to a sawtooth frequency ramping pattern. The mass transport equation was modified to incorporate the effect of acoustic forces on the concentration of particles. This was achieved by balancing the forces acting on particles. The frequency ramping was implemented as a parametric sweep for the time harmonic frequency response in time steps of 0.1s. The physics phenomena of piezoelectricity, acoustic fields and diffusion of particles were coupled and solved in COMSOL Multiphysics™ (COMSOL AB, Stockholm, Sweden) following a three step approach. The first step solves the governing partial differential equations describing the acoustic field by assuming that the pressure field achieves a pseudo steady state. In the second step, the acoustic radiation force is calculated from the pressure field. The final step allows calculating the locally changing concentration of particles as a function of time by solving the modified equation of particle transport. The diffusivity was calculated as function of concentration following the Garg and Ruthven equation which describes the steep increase of diffusivity when the concentration approaches saturation. However, it was found that this steep increase creates numerical instabilities at high voltages (in the piezoelectricity equations) and high initial particle concentration. The model was simplified to a pseudo one-dimensional case due to computation power limitations. The predicted particle distribution calculated with the model is in good agreement with the experimental data as it follows accurately the movement of the bands in the centre of the chamber.

14.
Lab Chip ; 12(3): 506-14, 2012 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-22218392

RESUMO

Piezoelectric materials are widely used in the excitation of MHz frequency vibrations in devices for ultrasonic manipulation. An applied electrical voltage is transformed into mechanical stress, strain and displacement. Piezoelectric elements can be used in either a resonant or non-resonant manner. Depending on the desired motion the piezoelectric longitudinal, transverse or shear effects are exploited. Because of the coupling between electrical and mechanical quantities in the constitutive law the modelling of devices turns out to be quite complex. In this paper, the general equations that need to be used are delineated. For a one-dimensional actuator the underlying physics is described, including the consequences resulting for the characterization of devices. For a practical setup used in ultrasonic manipulation, finite element models are used to model the complete system, including piezoelectric excitation, solid motion and acoustic field. It is shown, how proper tailoring of transducer and electrodes allows selective excitation of desired modes.

15.
Lab Chip ; 12(5): 852-62, 2012 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-22301707

RESUMO

Because of uncertainties in material and geometrical parameters in ultrasonic devices, experimental characterization is an indispensable part in their successful application for the manipulation of particles or cells. Its miniaturized size precludes the use of many of the usual tools used for macroscopic systems. Also, a further challenge is the fact that the resulting motion due to the electromechanical actuation has both high frequency and small amplitudes. Contactless methods like laser interferometry are therefore promising methods. In addition, as long as there is strong electromechanical coupling between the transducer and the device also electrical measurements like admittance curves give insight into the frequencies at which the devices might work best. This is the case for example for piezoelectric transducers working at one of their resonance frequencies. Because the devices usually are used in resonant modes, narrow frequency detection methods like lock in amplifiers help to improve the signal to noise ratio. Also many analysis tools have been established in the context of modal analysis, which is based on frequency domain methods. Special emphasis is placed here on the determination of the quality factor Q of the resonator, as Q determines the efficiency of a device.

16.
Lab Chip ; 12(20): 4010-21, 2012 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-22971740

RESUMO

Acoustic radiation forces are increasingly used for the handling of micron sized particles (cells, functionalized beads, etc.) suspended in a fluid in the chamber of a manipulation device. The primary radiation forces arise as a nonlinear effect when an acoustic wave interacts with a particle. For specific robotic applications, precise control of the acoustic field in the cavity is important, which is excited, for example, by piezoelectric transducers attached to the device. Based on Gor'kov's potential the relevant forces on spherical particles can be computed. The field can be controlled by varying the excitation parameters: chamber and electrode configuration, as well as frequency, amplitude and phase of the excitation and their modulation. In the first part of the present tutorial, a number of examples are described: displacement and rotation of particles in micro machined chambers and macroscopic transport of particles in a larger chamber. In the second part, numerical tools (Finite Volume Method, COMSOL) are used to model the interaction of the acoustic field with a particle beyond a Gor'kov potential: viscosity, effects of walls near particles and acoustic radiation torque to rotate the particle. Excellent agreement between the various methods has been found.


Assuntos
Técnicas Analíticas Microfluídicas/instrumentação , Técnicas Analíticas Microfluídicas/métodos , Modelos Teóricos , Ultrassom/instrumentação , Ultrassom/métodos , Microeletrodos , Tamanho da Partícula , Retratos como Assunto , Suspensões , Viscosidade
17.
Ultrasonics ; 48(6-7): 529-36, 2008 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-18649908

RESUMO

The use of acoustic radiation forces for the manipulation and positioning of micrometer sized particles has shown to be a promising approach. Resonant excitation of a system containing a particle laden fluid filled cavity, can (depending on the mode excited) result in positioning of the particles in parallel lines (1-D) or distinct clumps in a grid formation (2-D) due to the high amplitude standing pressure fields that arise in the fluid. In a broader context, the alignment of particles using acoustic forces can be used to assist manipulation processes which utilise an external mechanical tool, for instance a microgripper. In such a system, particles can be removed sequentially from a line formed by acoustic forces within a microfluidic channel, hence allowing a degree of automation. In order to fully automate the gripping process, the particles must be confined to a repeatable and accurate location in two dimensions (assuming that in the third dimension they sit on the lower surface of the channel). Only in this way it is possible to remove subsequent particles by simply bringing the gripper to a known location and activating its fingers. This combined use of acoustic forces and mechanical gripping requires that one extremity of the channel is open. However, the presence of the liquid-air interface which occurs at this opening, causes the standing pressure field to decay to zero towards the opening. In a volume of liquid in proximity to the interface positioning of particles by acoustic forces is therefore no longer possible. In addition, the longitudinal gradient of the field can cause a drift of particles towards the longitudinal center of the channel at some frequencies, undesirably moving them further away from the interface, and so further from the gripper. As a solution the use of microfluidic flow induced drag forces in addition to the acoustic force potential has been investigated.


Assuntos
Acústica/instrumentação , Automação , Técnicas Analíticas Microfluídicas/instrumentação , Desenho de Equipamento , Análise de Elementos Finitos , Tamanho da Partícula , Transdutores , Ultrassom
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