rapid-manufacturing-of-thin-soft-pneumatic-actuators-and-robots

Rapid Manufacturing of Thin Soft Pneumatic Actuators and Robots

This protocol describes a method for rapid manufacturing of soft pneumatic actuators and robots with an ultrathin form factor using a heat press and a ...

rapid-formation-testing-self-expanding-niti-frames-with-small-form

Rapid Formation and Testing of Self-expanding NiTi Frames with a Small Form Factor Suitable for Minimally Invasive Implants

NiTiNOL (commonly referred to as nitinol or NiTi) wires feature exceptional shape memory and super-elastic characteristics, while shape-setting is often a ...

Weill Cornell Medicine

New Mexico State University

The design and development of a novel apparatus for the simultaneous measurement of electrical resistivity and Seebeck coefficient of films is reported here. Mounting stage is integrated inside a cryostat chamber enabling measurements over the 10-400 K temperature range, intended for organic thermoelectrics. Finite element method was used to analyze the thermo-mechanical response of the sample holder. The apparatus was validated against high purity nickel film, and a very good agreement was found.

Measurement of the thermoelectric power factor of films over the 10-400 K range.

Pneumatically actuated soft robots address many challenges with interfacing with delicate objects, but these actuators/robots are still bulky and require many hours to fabricate, limiting their widespread use. This article reports a novel design and manufacturing method for ultrathin soft robots and actuators (∼70 μm) using a laser-cutting machine that cuts/welds sheets of thermoplastic polyurethane (TPU) from a 2D CAD drawing. Using this method, five different soft actuators (e.g., bending, rotating, contracting) are designed, fabricated, and characterized with both planar and nonplanar motions. Furthermore, we show how stacking multiple sheets of TPU enables rapid fabrication of multifunctional actuators. Finally, a portable four-arm swimming robot is designed and fabricated without any assembly steps. This rapid fabrication method enables soft robots to go from concept to operational within minutes, and creates a new subclass of soft robots suitable for applications requiring a robot to be ultrathin, lightweight, and/or fit within small volumes.

Laser Cutting as a Rapid Method for Fabricating Thin Soft Pneumatic Actuators and Robots.

3D printing has been used to create a wide variety of anatomical models and tools for procedural planning and training. Yet, the printing of permanent, soft endocardial implants remains challenging because of the need for haemocompatibility and durability of the printed materials. Here, we describe an approach for the rapid prototyping of patient-specific cardiovascular occluders via 3D printing and static moulding of inflatable silicone/polyurethane balloons derived from volume-rendered computed tomography scans. We demonstrate the use of the approach, which provides custom-made implants made of high-quality, durable and haemocompatible elastomeric materials, in the fabrication of devices for occlusion of the left atrial appendage-a structure known to be highly variable in geometry and the primary source of stroke for patients with atrial fibrillation. We describe the design workflow, fabrication and deployment of patient-specific left atrial appendage occluders and, as a proof-of-concept, show their efficacy using 3D-printed anatomical models, in vitro flow loops and an in vivo large animal model.

Patient-specific design of a soft occluder for the left atrial appendage.

Micropatterning is often used to engineer the surface properties of objects because it allows the enhancement or modification of specific functionalities without modification of the bulk material properties. Microneedle arrays have been explored in the past for drug delivery and enhancement of tissue anchoring; however, conventional methods are primarily limited to thick, planar substrates. Here, we demonstrate a method for the fabrication of microneedle arrays on thin flexible polyurethane substrates. These thin-film microneedle arrays can be used to fabricate balloons and other inflatable objects. In addition, these thin-filmed microneedles can be transferred, using thermal forming processes, to more complex 3D objects on which it would otherwise be difficult to directly pattern microneedles. This function is especially useful for medical devices, which require effective tissue anchorage but are a challenging target for micropatterning due to their 3D nonplanar shape, large size, and the complexity of the required micropatterns. Ultrathin flexible thermoplastic polyurethane microneedle arrays were fabricated from a polydimethylsiloxane (PDMS) mold. The technique was applied onto the nonplanar surface of rapidly prototyped soft robotic implantable polyurethane devices. We found that a microneedle-patterned surface can increase the anchorage of the device to a tissue by more than twofold. In summary, our soft lithographic patterning method can rapidly and inexpensively generate thin-film microneedle surfaces that can be used to produce balloons or enhance the properties of other 3D objects and devices.

Microneedle Patterning of 3D Nonplanar Surfaces on Implantable Medical Devices Using Soft Lithography.

Passive sensor-transponders have raised interest for the last few decades, due to their capability of low-cost remote monitoring without the need for energy storage. Their operating principle includes receiving a signal from a source and then reflecting the signal. While well-established transponders operate through electromagnetic antennas, those with a fully acoustic design have advantages such as lower cost and simplicity. Therefore, detection of pressures using the ultrasound signal that is backscattered from an acoustic resonator has been of interest recently. In order to infer the pressure from the backscattered signal, the established approach has been based upon the principle of detection of the shift to the frequency of resonance. Nevertheless, regression of the pressure from the signal with a small error is challenging and has been subject to research. Here in this paper, we explore an approach that employs deep learning for inferring pressure from the ultrasound reflections of polymeric resonators. We assess if neural network regressors can efficiently infer pressure reflected from a fully acoustic transponder. For this purpose, we compare the performance of several regressors such as a convolutional neural network, a network inspired by the ResNet, and a fully connected neural network. We observe that deep neural networks are advantageous in inferring pressure information with a minimal need for analyzing the signal. Our work suggests that a deep learning approach has the potential to be integrated with or replace other traditional approaches for inferring pressure from an ultrasound signal reflected from fully acoustic transponders or passive sensors.

Application of deep neural networks for inferring pressure in polymeric acoustic transponders/sensors.

This paper reports on the development of a novel soft robotic system for remote ultrasound applications. Direct contact of the ultrasound probe with the patient's body represents a safety risk and therefore control of the probe's positioning and applied force is a crucial task. The proposed robot uses a passive control system that provides safe interaction between the robot and the patient by leveraging soft robotics technology. The soft robot's structure can be considered as a nonlinear spring which can be designed to exert a safe force within the robot's workspace to guarantee the safety of human-robot interaction. The literature suggests that effective ultrasound imaging of both the heart and abdomen requires six degrees-of-freedom. These degrees-of-freedom consist of three translational motions, which are achieved using a novel hybrid soft cable-driven parallel robot, and three wrist motions, which is based on a universal joint design. The experimental results show that the robot can achieve all these six degrees-of-freedom, and its blocking force can be engineered to generate a uniform force within the workspace.

Toward Development of Novel Remote Ultrasound Robotic System Using Soft Robotics Technology.

Self-expanding frames for minimally invasive implants are typically made from nitinol wires and are heat treated to maintain the desired shapes. In the process of heat treatment, nitinol structures are placed in a high-temperature oven, while they are confined by a fixture. During this process, nitinol exerts a high amount of force. Accordingly, a fixture requires high mechanical strength and temperature resistance; this is why fixtures are typically made from metals. The use of metal fixture also increases the turnaround time and cost. However, accelerating this process is beneficial in many applications, such as rapid development of medical implants that are patient-specific. Inspired by the use of sacrificial layers in microfabrication technology, here we propose a novel method for shape setting nitinol wires using a sacrificial metal fixture. In this process, the nitinol wires are first aligned inside copper hypotubes. Next, the forming process is done using hand-held tools to shape complex geometrical structures, annealing the nitinol reinforced by copper, and then selectively etching copper hypotubes in ammonium persulfate solutions. In this process, other sacrificial cores, which are 3D printed or cast from low-cost polymers, are also used. This combination of polymeric cores and minimal use of metals enables reducing the cost and the turnaround time. As a proof of concept, we showed that this process was capable of fabricating springs with mm or sub-mm diameters. The result showed a change of less than 5% in the intended diameter of the nitinol spring with diameters ranging from ~ 0.7 to 1.9 mm, which confirms copper as a suitable sacrificial fixture to obtain the desired complex geometry for nitinol. A metric, based on the elastic strain stored in copper is suggested to predict the possible variation of the intended dimensions in this process. Finally, to demonstrate the potential of this method, as proof of concept, we fabricated NiTi wire frames designed for anchoring through the atrial septum. These frames demonstrated septal defect occluders that were designed based on a patient's cardiac image available in the public domain. This low-cost rapid fabrication technique is highly beneficial for a variety of applications in engineering and medicine with specific applications in rapid prototyping of medical implants.

Low-cost prototyping of nitinol wires/frames using polymeric cores and sacrificial fixtures with application in individualized frames anchoring through the atrial septum.

Hyperelastic materials are extensively incorporated in medical implants and microelectromechanical systems due to their large, elastic, recoverable strains. However, their mechanical properties are sensitive to processing parameters that may lead to inconsistent characterization. Various test setups have been employed for characterizing hyperelastic materials; however, they are often costly. Recent advancements in additive manufacturing and open-source software/hardware suggest the possibility of simpler solutions in research settings for characterizing them; raising the question of whether one can characterize these materials with low-cost tools and tests that take advantage of soft and small form-factor samples. Here, the authors investigate the potential of an open-source, 3D-printed test system designed for characterizing such materials. This system is tailored for small form-factor samples (sub-mm thickness) and large elastic deformations, common in polymeric parts of minimally invasive implants. The authors developed parts using additive manufacturing for uniaxial and planar tension testing, with a low-cost image correlation method adapted for measuring large strains. Polydimethylsiloxane was chosen for demonstration of a two-parameter Mooney-Rivlin model, due to its documentation and use in biocompatible devices. The estimated Young's and shear moduli were repeatable and consistent with the literature. Curve-fitting was challenging and dependent on the optimization choices, when data points were limited, consistent with prior reports. However, with a large number of data points and ideal optimization error choice,  and  were found to be close to those reported previously. This work demonstrates a low-cost, 3D-printed, open-source test setup for characterizing hyperelastic materials using a two-parameter Mooney-Rivlin model with reasonable accuracy.

Design and manufacture of a low-cost 3D-printed laboratory device to measure the hyperelastic properties of polymeric films with small form factor suitable for medical devices.

Seyedhamidreza Alaie

Dalio Institute of Cardiovascular Imaging,
New York-Presbyterian Hospital,
Department of Radiology,
Dalio Institute of Cardiovascular Imaging, New York-Presbyterian Hospital

Weill Cornell Medicine

Rapid Manufacturing of Thin Soft Pneumatic Actuators and Robots

Rapid Formation and Testing of Self-expanding NiTi Frames with a Small Form Factor Suitable for Minimally Invasive Implants

Seyedhamidreza Alaie

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Dalio Institute of Cardiovascular Imaging,New York-Presbyterian Hospital,Department of Radiology,Dalio Institute of Cardiovascular Imaging, New York-Presbyterian Hospital

Weill Cornell Medicine

Rapid Manufacturing of Thin Soft Pneumatic Actuators and Robots

Rapid Formation and Testing of Self-expanding NiTi Frames with a Small Form Factor Suitable for Minimally Invasive Implants

Dalio Institute of Cardiovascular Imaging,
New York-Presbyterian Hospital,
Department of Radiology,
Dalio Institute of Cardiovascular Imaging, New York-Presbyterian Hospital