Multiple Actuations Research Articles

Liquid crystal polymer actuators with complex and multiple actuations.

Deformable liquid crystal polymers (LCPs), which exhibit both entropic elasticity of polymer networks and anisotropic properties originating from ordered mesogens, have gained more and more interest for use as biomedical soft actuators. Especially, LCP actuators with controllable mesogen alignment, sophisticated geometry and reprogrammability are a rising star on the horizon of soft actuators, since they enable complex and multiple actuations. This review focuses on two topics: (1) the regulation of mesogen alignment and geometry of LCP actuators for complex actuations; (2) newly designed reprogrammable LCP materials for multiple actuations. First, basic actuation mechanisms are briefly introduced. Then, LCP actuators with complex actuations are demonstrated. Special attention is devoted to the improvement of fabrication methods, which profoundly influence the available complexity of the mesogen alignment and geometry. Subsequently, reprogrammable LCP actuators featuring dynamic networks or shape memory effects are discussed, with an emphasis on their multiple actuations. Finally, perspectives on the current challenges and potential development trends toward more intelligent LCP actuators are discussed, which may shed light on future investigations in this field.

Bioinspired anisotropic PEEK for solvent sensing and programmable actuations

Soft actuators capable of reversible, strong and multiple actuations with minimum energy consumption are highly desired for the areas like soft robotics and internet of things. However, it remains highly challenging to achieve multiple-way actuations with materials having high mechanical strength and via a simple procedure. Here, accurate solvent sensing and solvent-induced actuations are realized at room temperature in 3D-printed actuator made of poly-ether-ether-ketone (PEEK), which is an excellent engineering plastic. The dual gradient of roughness and crystallinity in PEEK actuator, which is inspired by pinecone and regulated by 3D-printing, determines the absorption/desorption of solvent and thus the multiple-way actuation of PEEK actuator. The actuation can be further programmed by altering the solvent, the annealing temperature and the training method. As a result, PEEK actuator can be used to sense the incoming flow of organic solvents and to repeatedly transfer cargoes much heavier than its own bodyweight without the need of energy input. The work here not just provides a high-performance actuator that could function under harsh conditions, but also proposes a design strategy for sensor and actuators.

The Interplay between Different Stimuli in a 4D Printed Photo-, Thermal-, and Water-Responsive Liquid Crystal Elastomer Actuator.

Multi-stimuli responsivity in 3D-printed objects is receiving much attention. However, the simultaneous interplay between different environmental stimuli is largely unexplored. In this work, we demonstrate direct ink writing of an oligomeric ink containing an azobenzene photo-switch with an accessible hydrogen bond allowing triple responsivity to light, heat, and water. The resulting printed liquid crystal elastomer performs multiple actuations, the specific response depending on the environmental conditions. Bilayer films formed by printing on a static substrate can rapidly change shape, bending almost 80 degrees if irradiated in air or undergoing a shrinkage of about 50 % of its length when heated. The bilayer film assumes dramatically different shapes in water depending on combined environmental temperature and lighting conditions.

Actuation of an electrohydraulic manipulator with a novel feedforward compensation scheme and PID feedback in servo-proportional valves

Achieving good tracking control beyond 0.1Hz by electrohydraulic manipulators still remains challenging due to the coupling of nonlinear actuation dynamics and multiple actuations. A novel order-separated feedforward, or FF, model has been proposed for estimating the major part of the commands of servo-proportional valves for metering their ports to monitor oil flow in the paired cylinders. Motion studies have been executed in serial manipulation mode by using such control to two valves and in serial–parallel mode to eight valves. Oil leakage and cylinder friction have been included as lower-order effects for the narrow radial clearance and near-zero lap in the valves each paired with a low-friction cylinder. Other assumptions of negligible inertia and suspended weight under the pistons have been validated by a numerical exercise. A PID feedback has been added during real-time tracking by an FFPID controller. Reciprocating and circular motion demands in the serial mode and heave tracking in serial–parallel mode, all in a vertical plane, have been executed. More precise and smoother tracking has been achieved up to 1Hz in the serial mode mostly with lower expense of energy than a conventional PID-alone controller. Results indicate FF guidance to mitigate oscillations occasionally apparent in PID-only case due to either hunting among multiple solutions or gain sensitivity of the nonlinear system. Good heave tracking has been obtained up to 0.2Hz. Substantial disturbance rejection capability of the controller has been demonstrated against tension arising from the connecting oil hoses. A potential use of the FF model in diagnosing emerging valve or cylinder fault with their aging has also been explained.

Highly Integrated Multi-Material Fibers for Soft Robotics.

Soft robots are envisioned as the next generation of safe biomedical devices in minimally invasive procedures. Yet, the difficulty of processing soft materials currently limits the size, aspect-ratio, manufacturing throughput, as well as, the design complexity and hence capabilities of soft robots. Multi-material thermal drawing is introduced as a material and processing platform to create soft robotic fibers imparted with multiple actuations and sensing modalities. Several thermoplastic and elastomeric material options for the fibers are presented, which all exhibit the rheological processing attributes for thermal drawing but varying mechanical properties, resulting in adaptable actuation performance. Moreover, numerous different fiber designs with intricate internal architectures, outer diameters of 700µm, aspect ratios of 103 , and a fabrication at a scale of 10s of meters of length are demonstrated. A modular tendon-driven mechanism enables 3-dimensional (3D) motion, and embedded optical guides, electrical wires, and microfluidic channels give rise to multifunctionality. The fibers can perceive and autonomously adapt to their environments, as well as, probe electrical properties, and deliver fluids and mechanical tools to spatially distributed targets.

A Multi-Contact-Aided Continuum Manipulator With Anisotropic Shapes

Cable-driven continuum manipulators have shown excellent benefits to work for endoluminal intervention. Demand of small diameter for confined anatomy limits the usage of multiple actuations, leading to limited DOFs and bending shapes. To address this problem, this letter proposes a multi-contact-aided continuum manipulator with anisotropic bending shapes. First, contact-aided compliant mechanisms (CCMs) are configured at different locations to introduce the specific constraints to enable the anisotropy. Then, the forward and inverse kinematic models considering contact blocks are built. The reachable workspace of the continuum manipulator is given, and simulation cases are studied to demonstrate the superiority of the proposed manipulator. Finally, a 3D-printed physical prototype is fabricated, and preliminary experiments are conducted to evaluate the model accuracy. Results show an average shape error of 1.98 mm (4.2%) and a maximum of 3.58 mm (7.6%). A robotic bronchoscopy platform integrated with the continuum manipulator is developed to conduct the airway phantom experiments. The shape deviation of the proposed manipulator from the centerline of the bronchus is 31.8% smaller than that of the constant curvature manipulator. The experiments validate the system-level feasibility and effectiveness of the developed continuum manipulator.

Single-pass 1-needle actuation versus single-pass 3-needle actuation technique for EUS-guided liver biopsy sampling: a randomized prospective trial (with video)

Several reports have validated EUS-guided liver biopsy sampling (EUS-LB) as safe and effective. Nineteen-gauge EUS aspiration (FNA) or core (fine-needle biopsy [FNB]) needles are used, but different needle techniques can yield variable outcomes. Some data show that 1 pass (single liver puncture) with 1 actuation (1 to-and-fro needle movement) may be enough to obtain a satisfactory specimen. However, there has not been a head-to-head comparison of single versus multiple needle actuations for EUS-LB. This was a prospective randomized trial of EUS-LB in 40 patients comparing tissue yields and adequacy using 1 pass, 1 actuation (1:1) versus 1 pass 3 actuations (1:3) of an FNB needle. The primary outcome was number of complete portal triads (CPTs). Secondary outcomes were length of the longest piece, aggregate specimen length, number of cores >9mm, and adverse events (AEs). Computerized randomization determined selection (either 1:1 or 1:3 with fanning technique). Sample lengths were measured before pathologic processing. Both groups had similar demographics and indications for EUS-LB. All biopsy samples were adequate for pathologic interpretation. Compared with 1:1, biopsy sampling with 1:3 yielded more CPTs (mean [standard deviation], 17.25 [6.2] vs 24.5 [9.88]; P< .008) and longer aggregate specimen length (6.89 cm [1.86] vs 12.85 cm [4.02]; P< .001). AEs were not statistically different between the techniques. No severe AEs were noted. EUS-LB using the 1:3 technique produced longer liver cores with more CPTs than the 1:1 technique with an equivalent safety profile. Two needle passes are more likely to provide tissue adequacy according to the American Association for the Study of Liver Diseases guidelines. (Clinical trial registration number: UMIN 000040101.).

Humanoid gesture control ARM with manifold actuation by embedded system

The design and implementation of humanoid gesture control robotic arm with multiple actuations is proposed. Utilization of gesture based design is made here. The design is made such a way that five separate movable fingers, flexion and extension installed wrist with tilt feature. Human palm movements are imitated in robotic arm using the motion glove. To develop the processing of arms with additional movement, to improve the aesthetics both for the safety and to look as less artificial. Already in this field metallic and plastic variants are used. The dimensions are made with the help of human palm dimensions. A human design is not sufficient. It also need the movements that is done by actual human [1]. In this paper we propose the number of movements done by the arm is made to 120 [2].

Primary break-up and atomization characteristics of a nasal spray.

The primary objective of this research was to extract the essential information needed for setting atomization break up models, specifically, the Linear Instability Sheet Atomization (LISA) breakup model, and alternative hollow cone models. A secondary objective was to gain visualization and insight into the atomization break up mechanism caused by the effects of viscosity and surface tension on primary break-up, sheet disintegration, ligament and droplet formation. High speed imaging was used to capture the near-nozzle characteristics for water and drug formulations. This demonstrated more rapid atomization for lower viscosities. Image processing was used to analyze the near-nozzle spray characteristics during the primary break-up of the liquid sheet into ligament formation. Edges of the liquid sheet, spray break-up length, break-up radius, cone angle and dispersion angle were obtained. Spray characteristics pertinent for primary breakup modelling were determined from high speed imaging of multiple spray actuations. The results have established input data for computational modelling involving parametrical analysis of nasal drug delivery.

Humanoid gesture control arm with manifold actuation using additive manufacturing

The design and implementation of humanoid gesture control robotic arm with multiple actuations is proposed. Utilization of gesture based design is made here. The design is made such a way that five separate movable fingers, flexion and extension installed wrist with tilt feature. Human palm movements are imitated in robotic arm using the motion glove. To develop the processing of arms with additional movement, to improve the aesthetics both for the safety and to look as less artificial. Already in this field metallic and plastic variants are used. The dimensions are made with the help of human palm dimensions. A human design is not sufficient. It also need the movements that is done by actual human [1]. This paper we propose the number of movements done by the arm is made to 120 [2].

Magnetically-driven implantable pump for on-demand bolus infusion of short-acting glucagon-like peptide-1 receptor agonist

For type 2 diabetic patients, short acting glucagon-like peptide-1 receptor agonist (GLP-1 RA) is often prescribed with frequent needled injections. Long-acting GLP-1 RA for less frequent injections do not mimic physiologic secretion of GLP-1. Therefore, an implantable pump is proposed in this work, which can deliver a short-acting GLP-1 RA, exenatide, without needles and batteries. The implanted pump can infuse an accurate amount of exenatide bolus only when a noninvasive magnetic force is applied from outside the body. The pump includes a safety feature of patterned magnets for actuation to prevent accidental infusion possibly caused by a general household magnet. The reservoir for exenatide is made of a flexible biomaterial and thus, a negative pressure build-up in the reservoir can be prevented even after multiple actuations and almost all drug consumption (~ 94%). This allows a reproducible drug dose for a longer period after implantation, hence less frequent replenishment procedures. The pump is also equipped with an intermediate container with two distinct check-valves and thus, the reservoir of exenatide can be further separated and better prevented from infiltration of the bodily fluid surrounding the implanted pump. When tested in Goto-Kakizaki rats, the pump demonstrates the efficacy of exenatide similar to conventional subcutaneous injections. Therefore, the pump can be promising for patient-friendly, optimal delivery of short-acting GLP-1 RA that better follows the physiologic secretion profile of GLP-1.

Evaluation of Technique Using Pressurized Metered dose Inhaler and its Determinants among COPD Patients: A Cross Sectional Study

The aim was to evaluate the inhalation technique among COPD patients using pressurized metered dose inhaler and determinants of incorrect inhalation technique. In this hospital based cross-sectional study, total 92 COPD patients were enrolled. Basic socio-demographic information was collected. The inhalation technique was visually observed and scored on checklist. Statistical Analysis Used: Chi-square test and Fisher exact test. Among the 92 patients observed, 69 (75.0%) were males. The mean age of the patients was 45.8 ± 1.4 years. Correct technique was observed in only 22 (23.9%) patients step at which maximum number of patients committed mistake was exhalation 65.2% followed by breath holding 45.7% and multiple actuations were seen in 44.5%. It was found that substantial errors were made in the inhalation technique hence proper training and follow-up of the patients is required to achieve the desired effects of the inhaled medications.

Antistatic treatment and salbutamol dosing have variable effect on drug delivery of valved holding chambers

AimsOur aim was to evaluate whether the number of puffs or antistatic treatment have significant effect on drug delivery of six different valved holding chambers (VHCs). MethodsWe used simulated paediatric breathing pattern with 25/min frequency and 200 ml tidal volume. When comparing the effect of antistatic treatment, we used 100 μg of salbutamol (one puff Ventolin Evohaler 100 μg/dos) actuated into each VHC before and after detergent wash. When comparing the effect of one or two puffs (100 vs. 200 μg), all VHCs were washed prior to the measurements. ResultsAll VHC were significantly affected by antistatic treatment. Washing improved drug delivery of four VHCs (1.3–2.2 fold increase in median filter dose) but had an opposite effect in two devices (54–61% decrease). The effect of dose doubling resulted in a 2.03–2.93 fold increase on filter dose in two VHCs. Four out of the six VHC showed significantly poorer performance with two puffs as opposed to one puff (ratio of two puffs to one puff varied between 1.19 and 1.77). ConclusionVHCs marketed as antistatic are significantly affected by antistatic treatment. To ensure optimal drug delivery, salbutamol should be actuated to VHCs one puff at a time. Each VHC brand has its unique characteristic that affects drug delivery in a way that cannot be generalised to another VHC. There is a need for universal standardisation of VHCs. Key notesValved holding chambers (VHCs) that are marketed as antistatic are significantly affected by antistatic treatment. Multiple actuations before inhalation tend to decrease the drug delivery efficacy of VHCs. Each VHC brand has its unique characteristic that affects drug delivery in a way that cannot be generalised to another VHC. There is a need for comprehensive and financially independent testing and standardisation of VHCs.

Experimental for simulating walking motion by using single leg mechanism introduced the integrated coupled drive system having multiple coupled-wire actuations

Experimental for simulating walking motion by using single leg mechanism introduced the integrated coupled drive system having multiple coupled-wire actuations

A cephalopod-inspired combustion powered hydro-jet engine using soft actuators

Combustion in soft and compliant materials may enable new methods for underwater locomotion. Inspired by the motion of the soft bodied cephalopods, we developed a combustion-powered hydro-jet engine (CPHJE) using an expandable silicone bladder. The CPHJE used high energy density methane combustion to expand a silicone bladder and accelerate water into a hydro-jet that propelled the CPHJE. Cephalopods demonstrate the epitome of underwater soft robot capabilities. Their use of hydrojetting as a mode of high-speed underwater motion resembles high-power combustion events. This paper describes a soft combustion engine that propels a ∼0.7 kg body, with hydrodynamic surfaces in the likeness of an ellipsoid shaped squid, at instantaneous velocities of at least 0.8 m s−1 and single-pulse average velocities of 0.1 m s−1. High-speed videography informs a model for the CPHJE’s motion in time; the imaging also reveals that the hydrojetting generates a ring vortex. Tracking of this vortex results in an estimate that the working fluid is ejected in excess of 6.7 m s−1. We demonstrate the CPHJE motion is both repeatable and able to produce multiple actuations with the same bladder. These results demonstrate a new method of underwater propulsion using combustion in soft and compliant bladders.

Design of a smart bidirectional actuator for space operation

A common need for space borne instruments, satellites and planetary exploration payloads is the usage of compact, light and low power actuators. In the recent years, this need has been partially solved by the development of customized solutions with an increasing usage of smart materials. A linear bidirectional actuator based on shape memory alloy technology is presented in this work. The device has been conceived to lock the double-pendulum scanning mechanism of a miniaturized Fourier transform spectrometer for planetary observation. The mechanism class is that of pin pullers, with the pin locking the movable components of the spectrometer during launch and landing phases. The proposed mechanism, differently from available off-the-shelf devices, allows multiple actuations without the need of manual resetting. Moreover, the device requires to be powered only to change its status. An appealing feature of the adopted concept is that the actuation is intrinsically shock-less, a key requirement for deployment of devices sensitive to mechanical vibration and shocks. All these characteristics, in addition to the design flexibility of the proposed concept in terms of achievable forces and strokes, make the designed actuator promising for many different applications, from space to ground. The designed bidirectional actuator provides 0.6 mm stroke and a 50 N preload but it represents just an example of implementation for the proposed concept. Structural design of the functional elastic components and SMA alloy characterization have guided the actuator development. A mockup of the actuator has been manufactured and the predicted performances preliminary validated.

Photo-thermo-mechanically actuated liquid crystalline elastomer nanocomposite reinforced by polyurethane fiber-network

ABSTRACTIn this work, we develop a nanocomposite consisting of nematic liquid crystal elastomer (LCE) matrix incorporated with single-wall carbon nanotubes (SWCNTs) and the reinforcement phase of polyurethane fiber-network (PUFN). The photo-thermo-mechanical actuation of LCE matrix is realized by converting light into heat with assistant of SWCNTs. The PUFN enhances the mechanical properties of the material, thus the actuation capability. Under the irradiation from a wide-spectrum light source with an intensity on the order of 100 mW/cm2, the PUFNs/SWCNT/LCE nanocomposite contracts up to 27% of the original length in several seconds due to the photo-induced strain, and recovers to the original length in several seconds after the light source is switched off. The efficiency of actuation is not light-spectrum dependent. The maximum effective actuation force is about 260 kPa, much larger than that of the LCE material without the reinforcement of PUFNs. The tensile strength and the performance of anti-fatigue failure under multiple reversible actuations are also greatly improved. The mechanism of the actuation capability of LCE material involved in the fiber-network reinforcement phase is studied.

Small-size controlled vacuum spark-gap in an external magnetic field

It is demonstrated that the operation of a small-size controlled spark-gap can be controlled by applying a uniform external magnetic field. It is shown that the magnetic field of such a simple configuration efficiently suppresses the effect of localization of the discharge current after multiple actuations of the spark-gap.

State space reconstruction applied to a multiparameter chaos control method

The idea of the chaos control is the stabilization of unstable periodic orbits (UPOs) embedded in chaotic attractors. The OGY method achieves system stabilization by using small perturbations promoted in the neighborhood of the desired orbit when the trajectory crosses a Poincare section. A generalization of this method considers multiple actuations of parameters and sections, known as semi-continuous multiparameter method. This paper investigates the state space reconstruction applied to this general method, allowing chaotic behavior control of systems with non-observable states using multiple control parameters from time series analysis, avoiding the use of governing equations. As an application of the proposed multiparameter general formulation it is presented an uncoupled approach where the control parameters do not influence the system dynamics when they are not active. This method is applied to control chaos in a nonlinear pendulum using delay coordinates to perform state space reconstruction. Results show that the proposed procedure can be applied together with delay coordinates providing UPO stabilization.

Data-driven physical parameter estimation for lumped mass structures from a single point actuation test

Data-driven subspace system identification techniques developed from control theory provide a rich set of analytical tools to estimate state-space models of structural systems. Furthermore, a recent technological advance in physical parameter extraction directly from the identified state-space models paves a way for new developments in experimental structural dynamics. In this study, a practical issue of data-driven physical parameter estimation for lumped mass structures is discussed. To cope with difficulties related to dynamic tests of multiple actuations, this study proposes a signal processing strategy to estimate physical parameters from a dynamic test of single point actuation. To demonstrate the proposed strategy, an experimental study is conducted. A three-story shear frame structure is excited by a modal shaker with an input force measured and the corresponding displacement responses at each floor are scanned using a laser Doppler vibrometer (LDV). Based on the proposed strategy, physically interpretable mass and stiffness matrices, as well as non-proportional damping matrix are estimated solely from the measured experimental data.