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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

A Non Resonant Piezoelectric Sensor for Mass, Force and Stiffness Measurements

Shrikanth, V January 2015 (has links) (PDF)
The word piezo in greek means \to compress". Piezoelectric sensors work on the principle of direct piezoelectric effect, where a mechanical input generates a corresponding electric charge. The advantages of these sensors are wide fre-quency range of operation, high stiffness and small size. The main limitation of a piezoelectric sensor is that it cannot be used in measurements that are truly static. When a piezoelectric sensor is subjected to a static force, a fixed amount of charge is developed which would eventually decay at a rate dependent on the external impedance of the sensor circuitry. Operating sensors at resonance have been one of the methods to overcome the limitation of using piezoelectric sensors for static measurements. However, since both actuation and sensing are done by the same piezoelectric element, this results in a cross-talk of input and output signals. The drawback of using single piezoelectric element for actuation and sensing is overcome in this work by using two identical elements|one for actuation and one for sensing. The operating frequency is about 10 % of the natural frequency of the sensor, thus enabling to operate the sensor in non resonant mode. Since the actuation and sensing mechanisms are separated, static measurement can be carried out. The output signal from the sensing element is monitored by a Lock-in amplifier which works on the principle of phase sensitive detection. The advantage of this sensor design is high sensitivity along with narrow band detection. It can be shown that the voltage output of the sensor Vout / a1 + m(b1 + b2F + b3K) + c1F + d1K, where m and K are the external mass and interaction stiffness, respectively, F is the force acting on it. By maintaining any two of these three quantities constant, the remaining one can be measured without any difficulty. The non resonant mode of operation makes it possible to explore the potential of this sensor in investigating mechanics of solid-liquid (viscous), solid-solid (inelastic) and solid-tissue(viscoelastic) interactions. High sensitivity, wide range of measurement (1 g{1 g) and high resolutio(0.1 g) of the non resonant mass sensor makes it possible to use it in measure-ment of very small masses of the order 1 g. Typically, resonant sensors such as quartz crystal microbalance (QCM) are used for mass measurements at that range. However, since the performance of resonant sensors is controlled by damp-ing, a phenomenon known as `missing mass effect' arises. Operating a sensor in non resonant mode (stiffness controlled mode) is a way to overcome this problem, especially when the mass is viscous and/or viscoelastic in nature. Drosophila fly, egg and larvae are the viscoelastic masses that are measured using this non res-onant sensor. Evaporating sessile drops of water and Cetyl trimethylammonium bromide (CTAB) surfactant solution from nominally flat surfaces are monitored to characterize the sensor for viscous mass measurement. Evaporation rate per unit surface area remains more or less constant, during the initial stages of evap-oration. When the surfactant concentration is varied, evaporation rate per unit surface area is highest for solutions around critical miscelle concentration (CMC). A study is carried out to understand the effect of concentrations on spreading of ink over inkjet printing paper. It is found that the spreading is least around CMC, since spreading is dependent on the rate of evaporation. The non resonant piezoelectric sensor which has high stiffness and quick re-sponse is also capable of measuring very small frictional forces. This sensor is configured to work as an inertial slider. Friction measurement at micro scales is important for designing microsystems such as stick-slip actuators. At such length scales, experiments have to performed at low loads and high excitation frequencies. The support stiffness of such systems should be high and the force of friction generated during slipping, when displacements are smaller than the contact radius, are of the order of few N. The displacement during slipping (S) is dependent on the amplitude of the input voltage to the actuation element. The frictional force measured during slipping by the sensor element indicates that the co-efficient of friction ( ) is independent of the sliding velocity. The developed non resonant sensor in this work under small amplitude exci-tation, can measure force gradient (i.e. stiffness). The total force generated when a needle is inserted into a viscoelastic material is a sum of force due to stiffness of the material, friction and the cutting force at the tip. The force due to stiffness is dominant when the needle is bending the tissue before the puncture occurs. Use of the non resonant sensor in tandem with strain gauge force sensor enables distinguishing the three components of the total force. The slope of the force-displacement (F -d) curve during the initial stages of needle penetration into the viscoelastic material, before puncture, is indicative of the stiffness of the mate-rial. The peak force measured during penetration is higher for needles with larger diameters and lower insertion velocities. The viscoelastic response (relaxation) of the material remains independent of the insertion velocity, for a given thickness of the material and a constant needle diameter. In summary, the sensor designed and developed in this work operates in stiffness controlled mode to eliminate the `missing mass effect' encountered dur-ing resonant mode of operation, has been clearly highlighted. Mass, force and stiffness measurements are possible over a wide range just by varying the ampli-tude of the input signal to the actuator element. The advantages such as high stiffness, small size and high response makes it advantageous to carry out in-situ micro scale studies in scanning electron microscopy (SEM) and transmission electron microscopy (TEM).
32

Objektivizace posturální funkce břišních svalů / The objectification of postural function of abdominal muscles

Novák, Jakub January 2018 (has links)
This thesis evaluates the possibility of using objective measurements to assess the postural function of abdominal muscles. The theoretical part provides an overview of findings regarding postural function of the abdominal muscles and the context for their co-activation using intra-abdominal pressure. The results are summarized in the form of research studies relating postural function and low back pain (LBP). The overview of the methods used to measure intra-abdominal pressure and the abdominal muscle activity is the main focus. In this section, we present a new methodology for measuring the activity of the abdominal muscles by using pressure sensors attached to the abdominal wall in the areas of the groin and the lumbar triangle. Methodology: In the experimental part, we tested 35 healthy subjects (average age 21.26t, SD ± 1,62) in 3 posturally different seated scenarios: 1. resting breathing, 2. with added external load (the subjects held a dumbbell 20% of their body weight) and 3. with maximum voluntary increase in intra-abdominal pressure (the diaphragm test). Results: An independent samples t-test indicated that the pressure created by the abdominal wall for both sensors in situation resting breathing increases in situation external load (HA1: upper sensor p=0.0079, lower sensor p=0.0009). We...
33

Sensor de força utilizando Fiber taper / Fiber taper based force sensor

Felipe Bueno Hernandez 29 March 2016 (has links)
Este trabalho teve por objetivo desenvolver e caracterizar um sensor de força utilizando uma fibra óptica modificada pelo processo conhecido como Fiber tapering. A fibra quando modificada deixa exposto o campo evanescente, o que a torna sensível a influências externas, e a luz guiada na fibra pode vir a sofrer reflexão interna total frustrada ao entrar em contato com materiais. Ao envolver a região modificada por um material elastomérico, a área de contato e consequentemente a atenuação torna-se uma função da intensidade da força aplicada, possibilitando então relacionar a força a atenuação da luz. Baseando-se nesse efeito, foi criado um sensor de dimensões reduzidas, de rápida resposta, linear, altamente sensível e de boa repetibilidade. Foi criado também um circuito eletrônico utilizando amplificadores operacionais para a aquisição e processamento do sinal proveniente da fibra e selecionado um sensor comercial comum para a realização de experimentos e comparações. Ambos os sensores foram posicionados sobre uma balança de precisão e submetidos a diversos esforços obtendo-se dados sobre a resposta estática. Em seguida utilizando um shaker eletrodinâmico foram medidos os tempos de resposta a uma entrada degrau, e realizando esforços repetitivos foram analisados os desvios das medidas lidas pelos sensores. / The aim of this research was to develop and characterize a force sensor using a modified optical fiber by a process known as Fiber tapering. The modified fiber leaves the evanescent field exposed and prone to external influences and the guided light may suffer frustration of total internal reflection upon contact with materials. When covering the modified fiber section with an elastomeric material, the contact area and therefore the attenuation becomes a function of the applied pressure, making it possible to relate force to attenuation in light intensity. Based on this effect, a small sensor was created, having a quick response time, with high linearity, high sensitivity and good repeatability. Along with the sensor, an electronic circuit using operational amplifiers was designed for acquisition and processing of the signal obtained from the optical fiber. In addition, in order to perform experiments and comparisons, a standard force sensor was chosen. Both sensors were placed over a precision weighing scale and had different intensities of force applied on them, and after that, data regarding static measurements was gathered. The response time was obtained using an electrodynamic shaker and applying a step input. Furthermore, data was gathered about the deviations on the measurements by performing a repetitive set of compressions.
34

Optimalizace vlastností snímače vektoru kontaktní síly / Design Optimization of Contact Force Vector Sensor

Vála, Pavel January 2008 (has links)
The aim of this work is an optimalization of vector contact force sensor properties which prototype is at the moment designed. The principle of sensor is based on transformation active part of sensor using three tensiometers and following value indentification of loading force vector using neuron network. Sensor has a bad sensitivity when axis force load or near to axis of sensor. To solve this problem ''MKP'' model of sensor was used on which suitable optimalization method was applicated. From the result of optimalization modificated sensor will be proposed and will be made a utility verification using neuron network.
35

Influence de l'environnement odorant sur le processus de simulation motrice révélée par une cellule de force en population jeune et vieillissante saine / Influence of odorant environment on motor simulation process revealed by a grip-force sensor in young and healthy aging population

Blampain, Justine 03 April 2019 (has links)
L’avancée de l’âge entraîne une diminution du contrôle moteur ainsi que l’apparition de troubles de la marche et de l'équilibre. Ces difficultés affectent la capacité des personnes âgées à accomplir les activités de la vie quotidienne et à maintenir leur indépendance (Salthouse, 2000 ; Seidler et al., 2010). Dans le cadre des théories de la simulation, de nombreuses études ont révélé des similitudes, tant au niveau comportemental que neuronal, entre exécution et simulation motrice (Decety & Jeannerod, 1995 ; Grezes & Decety, 2001). Selon Jeannerod (2001), ce processus cognitif permet de simuler mentalement une action, tandis qu’un mécanisme d’inhibition est mis en place pour contrôler toute exécution motrice externe (Bonnet et al., 1997 ; Jeannerod, 1994). Il est toutefois difficile de caractériser ce processus et d’ainsi révéler les troubles de simulation. Par ailleurs, peu d’études se sont intéressées à stimuler le processus de simulation motrice, notamment par l’utilisation de stimuli odorants. En effet, il a été rapporté que les odeurs avaient de nombreux effets sur la cognition (Millot et al., 2002), les émotions (Matsunaga et al., 2012), mais également l’exécution motrice (Castiello et al., 2006). Ce travail de thèse vise à évaluer l’effet de l’environnement odorant sur la simulation motrice lors de tâches d’observation et d’imagerie d’actions motrices chez des participants jeunes et âgés sains. Dans une première partie, nous avons révélé la simulation motrice à l’aide d’une cellule de force, lors de l’observation d’actions. Une amplitude plus importante des variations de la force de préhension a été observée lors du visionnage de scènes vidéo d’actions chez des sujets jeunes (étude 1), reflet de la mise en place du processus de simulation motrice. Ces résultats ont été retrouvés lors de la présentation de photos représentant des activités de faible (marche) ou forte (course) intensité (étude 2). Dans une deuxième partie, nous nous sommes intéressés à l’effet des odeurs sur le processus de simulation motrice, la cognition et les émotions. En effet, les odeurs sont fortement liées à la mémoire, qu’elle soit émotionnelle (souvenirs) ou sémantique (catégorisation d’une odeur). Placés dans un environnement odorant, les participants ressentaient une sensation de bien-être lorsque les odeurs rappelaient des souvenirs autobiographiques (étude 3). En nous basant sur le modèle d’Act-in (Versace et al.,2014), sentir une odeur entrainerait une réactivation des traces en mémoire et permettrait de se représenter les caractéristiques perceptuelles d’un objet. Ainsi, sentir une orange (gros fruit) ou une fraise (petit fruit) impliquerait une simulation et une exécution motrice différente en fonction de leurs caractéristiques propres. Nous avons ainsi évalué l’influence des odeurs de fraise et d’orange sur la simulation d’actions impliquant la manipulation de fruits (Etude 4). Il était observé un relâchement de la contraction musculaire lorsqu’une odeur de fraise était présentée. L’odeur d’orange entrainait en revanche une plus importante contraction musculaire, et cela même si les participants devaient s’imaginer manipuler une fraise. Ces études ouvrent la question de la représentation perceptuelle évoquée par l’odeur et pouvant influencer la simulation et donc l’exécution. Utiliser des odeurs pourrait, dès lors, être utile lors la prise en soin des personnes ayant des troubles de la motricité en augmentant la sensation de bien-être ressenti et en stimulant le processus de simulation motrice par l’évocation des caractéristiques de perception par l’odeur. Un ensemble de perspectives de recherches et d’applications cliniques s’ouvrent au regard de ces résultats, et seront discutées dans cette thèse. / With advanced age, a decline in fine motor control, gait and balance is observed. These difficulties affect the elderly’s ability to perform daily activities and maintain their independence (Salthouse, 2000; Seidler et al., 2010). In the context of simulation theories, numerous studies revealed similarities between motor execution and simulation, both at a behavioral and a neural level, in neuronal behavioral behavior (Decety and Jeannerod 1995, Grezes and Decety 2001). According to Jeannerod (2001), this cognitive process permits to simulate an action, while a mechanism of inhibition operates to control any external motor execution (Bonnet et al., 1997, Jeannerod, 1994). However, it is difficult to characterize this process and thus reveal the simulation disorders. In addition, few studies were interesting in the stimulation of the motor simulation process, especially by using odorant stimuli. Indeed, odors can have effects on cognition (Millot et al., 2002), emotions (Matsunaga et al., 2012), and motor execution (Castiello et al., 2006). This thesis aims to evaluate the effect of the odorant environment on motor simulation during action observation and motor imagery task in healthy young and elderly participants. In the first part, we revealed the motor simulation by using a grip-force sensor during action observation and motor imagery tasks. A higher amplitude of the grip force variations was observed in young participants when they were watching video scenes of actions (study 1), reflecting the involving of motor simulation process. These results were also found when pictures depicting either a low (walk) or high (race) intensity of force were presented to young participants (study 2). In the same way, these variations were observed in elderly participants when they were watching video of reach-to-grasp actions (study 3). In the second part, we were interested in the effect of odors on the motor simulation process, cognition and emotions. Indeed, odors are strongly related to memory, either in an emotional (memories) or in a semantic (categorization of an odor) way. Placed in an odorant environment, participants felt more positive affects when the odors recalling autobiographical memories were diffused (Study 4). Based on the Act-in model (Versace et al., 2014), perceiving an odor would lead to a reactivation of memory traces implying the perceptual characteristics of this odor. Thus, smelling an orange (large fruit) or a strawberry (small fruit) would lead to a different motor simulation and execution according to their own characteristics. We thus evaluated the influence of strawberry and orange odors on the simulation of reaching-grasping actions involving fruit handling (Study 4). A size-congruence effect was found when a strawberry odor was diffused, as revealed with the muscular release observed. On the other hand, the orange odor led to a more important muscular contraction, especially when the participants had to imagine handle a strawberry. These studies open the question of the perceptual representation evoked by the odors that can influence the simulation process and thus the execution. Using odors could be relevant in clinical settings for people who are suffering from motor disorders by improving the well-being feeling and also stimulate the motor simulation process by evoking perceptual characteristics with the odors. A set of research perspectives and clinical applications will be opened considering these results and will be discussed in this thesis.
36

Haptic optical tweezers with 3D high-speed tracking / Pinces optiques haptiques avec 3D haute vitesse de suivi

Yin, Munan 03 February 2017 (has links)
La micromanipulation a un grand potentiel pour révolutionner la recherche biologique et les soins médicaux. À petite échelle, microrobots peuvent effectuer des tâches médicales avec peu invasive, et d'explorer la vie à un niveau fondamental. Pinces optiques sont l'une des techniques les plus populaires pour la manipulation biologique. La production de petits lots qui exige une grande flexibilité repose principalement sur le processus de téléopération. Cependant, le niveau limité d'intuitivité rend de plus en plus difficile de conduire efficacement les tâches de manipulation et d'exploration dans le micromonde complexe. Dans de telles circonstances, des chercheurs pionniers ont proposé d'incorporer l'haptique dans la boucle de contrôle du système OTs, qui vise à gérer les tâches de micromanipulation de manière plus flexible et plus efficace. Cependant, la solution n'est pas encore complète, et il ya deux défis principaux à résoudre dans cette thèse: Détection de force 3D, qui doit être précis, rapide et robuste dans un espace de travail suffisamment grand; Haute vitesse jusqu'à 1 kHz force de rétroaction, ce qui est indispensable pour permettre une sensation tactile fidèle et d'assurer la stabilité du système. Dans la micromanipulation des pinceaux optiques, la vision est un bon candidat pour l'estimation de la force puisque le modèle force-position est bien établi. Cependant, le suivi de 1 kHz dépasse la vitesse des procédés de traitement classiques. La discipline émergente de l'ingénierie biomorphe visant à intégrer les comportements de vie dans le matériel informatique ou le logiciel à grande échelle rompt le goulot d'étranglement. Le capteur d'image asynchrone basé sur le temps (ATIS) est la dernière génération de prototype de rétine de silicium neuromorphique qui enregistre seulement les changements de contraste de scène sous la forme d'un flux d'événements. Cette propriété exclut le fond redondant et permet la détection et le traitement des mouvements à grande vitesse. La vision événementielle a donc été appliquée pour répondre à l'exigence de la rétroaction de force 3D à grande vitesse. Le résultat montre que les premières pinces optiques haptiques 3D à grande vitesse pour une application biologique ont été obtenues. La réalisation optique et les algorithmes de suivi événementiel pour la détection de force 3D à grande vitesse ont été développés et validés. L'exploration reproductible de la surface biologique 3D a été démontrée pour la première fois. En tant que puissant capteur de force 3D à grande vitesse, le système de pinces optiques développé présente un potentiel important pour diverses applications. / Micromanipulation has a great potential to revolutionize the biological research and medical care. At small scales, microrobots can perform medical tasks with minimally invasive, and explore life at a fundamental level. Optical Tweezers are one of the most popular techniques for biological manipulation. The small-batch production which demands high flexibilities mainly relies on teleoperation process. However, the limited level of intuitiveness makes it more and more difficult to effectively conduct the manipulation and exploration tasks in the complex microworld. Under such circumstances, pioneer researchers have proposed to incorporate haptics into the control loop of OTs system, which aims to handle the micromanipulation tasks in a more flexible and effective way. However, the solution is not yet complete, and there are two main challenges to resolve in this thesis: 3D force detection, which should be accurate, fast, and robust in large enough working space; High-speed up to 1 kHz force feedback, which is indispensable to allow a faithful tactile sensation and to ensure system stability. In optical tweezers micromanipulation, vision is a sound candidate for force estimation since the position-force model is well established. However, the 1 kHz tracking is beyond the speed of the conventional processing methods. The emerging discipline of biomorphic engineering aiming to integrate the behaviors of livings into large-scale computer hardware or software breaks the bottleneck. The Asynchronous Time-Based Image Sensor (ATIS) is the latest generation of neuromorphic silicon retina prototype which records only scene contrast changes in the form of a stream of events. This property excludes the redundant background and allows high-speed motion detection and processing. The event-based vision has thus been applied to address the requirement of 3D high-speed force feedback. The result shows that the first 3D high-speed haptic optical tweezers for biological application have been achieved. The optical realization and event-based tracking algorithms for 3D high-speed force detection have been developed and validated. Reproducible exploration of the 3D biological surface has been demonstrated for the first time. As a powerful 3D high-speed force sensor, the developed optical tweezers system poses significant potential for various applications.
37

The Impact Of Wood Species, Applied Force, And Sander Movement Speed On The Occurrence Of Swirl Scratch From Random Orbit Sanding

Song, Xiaoyu 07 September 2020 (has links)
No description available.
38

Měření aktivace břišní stěny v posturálních vývojových pozicích pomocí Ohm Beltu / Measurement of abdominal wall activation in developmental postural positions using Ohm Belt device

Svoboda, Petr January 2021 (has links)
Introduction: The aim of this work was to determine the difference in abdominal wall expansion and thus indirectly the amount of intra-abdominal pressure in various postural positions, first without any correction, then after verbal and manual instruction according to Dynamic Neuromuscular Stabilization (DNS) principles. The amount of activation of abdominal wall muscles in various postural positions helps determine the positions in which optimal postural stabilization is best activated. These positions may be suitable for postural therapy and training. The theoretical part introduces optimal trunk stabilization according to developmental kinesiology principles and DNS concept. Then, the relationship between the intra-abdominal pressure and postural activity of abdominal muscles is introduced as well as the most common methods of objectification. Participants and Methods: 30 healthy subjects (15 women and 15 men) aged 20 to 25 years (mean age 22.73 years, SD 1.88) were tested using the Ohm Belt device. This device uses pressure sensors that are attached to the abdominal wall in the area above the groin and in the trigonum lumbale and thus allows non-invasive monitoring of abdominal wall expansion and indirect measurement of the intra-abdominal pressure. The subjects were tested in five postural...
39

Temperature-Compensated Force/Pressure Sensor Based on Multi-Walled Carbon Nanotube Epoxy Composites

Dinh, Nghia Trong, Kanoun, Olfa 10 November 2015 (has links) (PDF)
In this study, we propose a multi-walled carbon nanotube epoxy composite sensor for force and pressure sensing in the range of 50 N–2 kN. A manufacturing procedure, including material preparation and deposition techniques, is proposed. The electrode dimensions and the layer thickness were optimized by the finite element method. Temperature compensation is realized by four nanocomposites elements, where only two elements are exposed to the measurand. In order to investigate the influence of the filler contents, samples with different compositions were prepared and investigated. Additionally, the specimens are characterized by cyclical and stepped force/pressure loads or at defined temperatures. The results show that the choice of the filler content should meet a compromise between sensitivity, temperature influence and noise behavior. At constant temperature, a force of at least 50N can be resolved. The measurement error due to the temperature influence is 150N in a temperature range of –20°C–50°C.
40

Micro-Newton Force Measurement and Actuation : Applied to Genetic Model Organisms

Khare, Siddharth M January 2016 (has links) (PDF)
Mechanical forces have been observed to affect various aspects of life, for example, cell differentiation, cell migration, locomotion and behavior of multicellular organisms etc. Such forces are generated either by external entities such as mechanical touch, fluid flow, electric and magnetic fields or by the living organisms themselves. Study of forces sensed and applied by living organisms is important to understand the interactions between organisms and their environment. Such studies may reveal molecular mechanisms involved in mechanosensation and locomotion. Several techniques have been successfully applied to measure forces exerted by single cells and cell monolayers. The earliest technique made use of functionalized soft surfaces and membranes as substrates on which cell monolayers were grown. The forces exerted by the cells could be measured by observing deformation of the substrates. Atomic Force Microscope (AFM) is another sensitive instrument that allows one to exert and measure forces in pico-Newton range. Advances in micromachining technology have enabled development of miniature force sensors and actuators. Latest techniques for mechanical force application and measurement use micromachined Silicon cantilevers in single as well as array form and micropillar arrays. Micropillar arrays fabricated using soft lithography enabled the use of biocompatible materials for force sensors. Together, these techniques provide access to a wide range of forces, from sub micro-Newton to milli-Newton. In the present work, types of forces experienced in biological systems and various force measurement and actuation techniques will be introduced. This will be followed by in depth description of the two major contributions of this thesis, 1) ―Colored polydimethylsiloxane micropillar arrays for high throughput measurements of forces applied by genetic model organisms‖. Biomicrofluidics, January 29, 2015. doi: 10.1063/1.4906905 2) ―Air microjet system for non-contact force application and the actuation of micro-structures‖. Journal of micromechanics and microengineering, December 15, 2015. doi: 10.1088/0960-1317/26/1/017001 Device developed for force measurement consists of an array of micropillars made of a biocompatible polymer Poly Dimethyl Siloxane (PDMS). Such devices have been used by researchers to measure traction forces exerted by single cells and also by nematode worm Caenorhabditis elegans (C. elegans). C. elegans is allowed to move in between the micropillars and the locomotion is video recorded. Deflection of the micropillar tips as the worm moves is converted into force exerted. Transparent appearance of C. elegans and PDMS poses difficulties in distinguishing micropillars from the worm, thus making it challenging to automate the analysis process. We address this problem by developing a technique to color the micropillars selectively. This enabled us to develop a semi-automated graphical user interface (GUI) for high throughput data extraction and analysis, reducing the analysis time for each worm to minutes. Moreover, increased contrast because of the color also delivered better images. Addition of color changed the Young‘s modulus of PDMS. Thus the dye-PDMS composite was characterized using hyper-elastic model. The micropillars were also calibrated using commercial force sensor. Analysis of forces exerted by wild type and mutant C. elegans moving on an agarose surface was performed. Wild type C. elegans exerted a total average force of 7.68 µN and an average force of ~1 µN on an individual pillar. We show that the middle of C. elegans exerts more force than its extremities. We find that C. elegans mutants with defective body wall muscles apply significantly lower force on individual pillars, while mutants defective in sensing externally applied mechanical forces still apply the same average force per pillar compared to wild type animals. Average forces applied per pillar are independent of the length, diameter, or cuticle stiffness of the animal. It was also observed that the motility of the worms with mechanosensation defects, lower cuticle stiffness, and body wall muscle defects was reduced with worms that have defective body wall muscle having the largest degree. Thus, we conclude that while reduced ability to apply forces affects the locomotion of the worm in the micropillar array, the reduced motility/locomotion may not indicate that the worm has reduced ability to apply forces on the micropillars. We also used the colored micropillar array for the first time to measure forces exerted by Drosophila larvae. Our device successfully captured the peristaltic rhythm of the body wall muscles of the larva and allowed us to measure the forces applied on each deflected pillar during this motion. Average force exerted by 1st instar wild type Drosophila larvae was measured to be ~ 1.5 µN per pillar. We demonstrated that a microjet of air can be used to apply forces in micro-Newton range. We developed a standalone system to generate a controlled air microjet. Microjet was generated using a controlled electromagnetic actuation of a diaphragm. With a nozzle diameter of 150 µm, the microjet diameter was maintained to a maximum of 1 mm at a distance of 5 mm from the nozzle. The force generated by the microjet was measured using a commercial force sensor to determine the velocity profile of the jet. Axial flow velocities of up to 25 m/s were obtained at distances as long as 6 mm. The microjet exerted a force up to 1 µN on a poly dimethyl siloxane (PDMS) micropillar (50 µm in diameter, 157 µm in height) and 415 µN on a PDMS membrane (3 mm in diameter, 28 µm thick). We also demonstrate that from a distance of 6 mm our microjet can exert a peak pressure of 187 Pa with a total force of about 84 µN on a flat surface with 8 V operating voltage. Next, we demonstrated that the response of C. elegans worms to the impinging air microjet is similar to the response evoked using a manual gentle touch. This contactless actuation tool avoids contamination and mechanical damage to the samples. Out of the cleanroom fabrication and robust design make this system cost effective and durable. Magnetic micropillars have been used as actuators. We fabricated magnetic micropillar arrays and designed actuation mechanisms using permanent magnet and a pulsed electromagnet. Force of about 19 µN was achievable using a permanent magnet actuation. In a pulsed electromagnetic field micropillar exerted a force of about 10 µN on a commercial force sensor. These techniques have promising applications when actuation needs to be controlled from long distances.

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