MICROSCALE HYDRAULIC HELICAL ACTUATOR FOR CARDIOVASCULAR PROCEDURES

Pulmonary emboli are one of the most common causes of deaths annually. When patientsundergo anticoagulant therapy, they may either experience long-term health effects or evenexperience another PE. Therefore, surgical interventions have been introduced to remove PEs.There are several commercially available surgical tools that remove PEs by using catheters todeliver thrombolytic agents to lyse the clot. However, some patients may have contraindicationsto the delivered drugs, so patients opt to have their PEs removed mechanically. However, the tipof the catheter that physically breaks apart PEs can only move in low degrees of freedom, whichcould result in some fragments getting left behind in the vessel since the catheter cannot press thefragments against the surface area of the vessel. Additionally, tips made with metal meshes poseharm to the vessel tissue. Our research presents the design and fabrication of a hydraulic helicalsoft actuator aimed at enhancing surgical catheters to remove pulmonary emboli (PE). Ourresearch progressed from a macroscale to microscale actuator to validate the design andfabrication process that produces the coiling mechanism. At the macroscale level, the actuator’soptimal shape, chamber size, materials, and power supply-coiling relationship were determined,showing that the actuator starts performing a clear coiling motion after 10 mL of air is supplied.Validating and testing the macroscale actuator allows us to apply the fabrication procedure to amicroscale actuator in a similar manner. However, an additional step to create the microscaleactuator is needed, which is creating a mold made of an alternative material. Currently, we are inthe process of determining how this mold should be created. Getting past this step will allow usto move forward to apply the same macroscale fabrication procedure to the microscale actuator.This research offers a comprehensive and methodical approach to developing a soft roboticactuator that is compatible with the human body and capable of effectively removing PEs

Parallel Helix Actuators for Soft Robotic Applications

Fabrication of soft pneumatic bending actuators typically involves multiple steps to accommodate the formation of complex internal geometry and the alignment and bonding between soft and inextensible materials. The complexity of these processes intensifies when applied to multi-chamber and small-scale (~10 mm diameter) designs, resulting in poor repeatability. Designs regularly rely on combining multiple prefabricated single chamber actuators or are limited to simple (fixed cross-section) internal chamber geometry, which can result in excessive ballooning and reduced bending efficiency, compelling the addition of constraining materials. In this work, we address existing limitations by presenting a single material molding technique that uses parallel cores with helical features. We demonstrate that through specific orientation and alignment of these internal structures, small diameter actuators may be fabricated with complex internal geometry in a single material—without- additional design-critical steps. The helix design produces wall profiles that restrict radial expansion while allowing compact designs through chamber interlocking, and simplified demolding. We present and evaluate three-chambered designs with varied helical features, demonstrating appreciable bending angles (>180°), three-dimensional workspace coverage, and three-times bodyweight carrying capability. Through application and validation of the constant curvature assumption, forward kinematic models are presented for the actuator and calibrated to account for chamber-specific bending characteristics, resulting in a mean model tip error of 4.1 mm. This simple and inexpensive fabrication technique has potential to be scaled in size and chamber numbers, allowing for application-specific designs for soft, high-mobility actuators especially for surgical, or locomotion applications

3D printed helical soft pneumatic actuators

Nature abounds with complex, three-dimensional shapes, and helices which are some of the most common structures in nature. This article describes a new soft pneumatic actuator that generates bending and twisting motions. The actuator consists of several angled chambers arranged in a line that can be actuated simultaneously using one power source (air pressure). The bending and twisting trajectory of the actuator has been characterized by changing the length of the actuator, the number of chambers, and the angle of chambers using the finite element analysis (FEA). The 3D printing method of fused filament fabrication (FFF) type was employed to directly manufacture the thin-walled, airtight, and low cost helical actuators, without requiring any post-manufacturing process. Based on the above design and fabrication, an entire soft helical actuator was fabricated, and used as a gripper to handle slender objects