|Concept for soft robot limb with distributed,
monolithically-fabricated linear actuators
With funding from NSF under the National Robotics Initiative, LAMRA is pursuing research at the intersection of several rapidly-developing fields: 3-D printing, soft robotics, printed electronics, and stretchable electronics. The objective is to develop a new additive manufacturing technology for electromechanical systems and electronics that will allow direct, integrated, flexible manufacturing of functional, active devices such as soft robots with embedded actuators, sensors, and circuitry. The challenge of manufacturing soft robotic components which include a large number of distributed actuators, sensors, and interconnects can be economically approached by 3-D printing multiple materials simultaneously. However, conventional 3-D printing can only build structures from a single class of material (e.g., a polymer or a metal). To overcome this limitation we are developing a new fabrication technology, Fiber Encapsulation Additive Manufacturing (FEAM). The process is implemented in a single, low-cost 3-D printer in which polymer and metal are deposited simultaneously. As a demonstration of FEAM's new capabilities, devices including a loudspeaker, inductive position sensors, and membrane switch have been produced. To support applications in soft robotics, we have also demonstrated printing of extremely soft, high-strength elastomers. Applications of FEAM include robotics, wearable electronics, defense systems, electronic packaging, customizable consumer electronics, and advanced prosthetics.
Additive Manufacturing with Advanced Elastomers.
Additive manufacturing (AM) allows complex, highly-customized 3-D structures to be produced quickly, flexibly, and without tooling by precisely depositing material in layers according to a CAD design. AM’s usefulness, however, is limited by the materials available, with metals and hard thermoplastic polymers dominating, and very limited use of elastomers. The few elastomers used in commercial processes have poor mechanical properties, including low tensile and tear strengths, and cannot provide good durability or longevity. Conversely, the excellent mechanical properties and biocompatibility of advanced elastomers, and a wide range of potential applications, represent great potential for expanding their use in 3-D printing. To capitalize on this, we are developing with corporate sponsorship a technology for additive manufacturing of parts made from advanced elastomers, including the ability to modulate the properties of the polymers during the manufacturing process. Applications for the proposed technology include single and multi-material elastomeric products such as patient-customized soft tissue implants, prosthetics, and orthotics; patient-customized medical instruments; customized consumer products such as sporting goods and fashion accessories; soft robotics; functional prototypes of molded rubber products; and soft tooling.
Selective laser sintering (SLS) is a well-established AM process for printing durable polymer parts and in some cases, working assemblies. The SLS process involves spreading a layer of fine thermoplastic powder (typically nylon) on a moveable platform in a heated chamber, then precisely scanning the beam of an infrared laser to locally sinter powder particles in the pattern of a cross-section of the desired part. SLS is a mature process that is favored for the high strength, highly impact-resistant parts that can be obtained, and for the ease of making complex structures (no support structures are needed since the unsintered powder supports the part during fabrication). Recently SLS has been adopted for making production end-use parts, e.g., for aircraft. However, despite its benefits, SLS has certain limitations. Surface finish, minimum feature size, and sometimes accuracy are poorer than with several other AM technologies. Moreover, SLS systems typically cost in the range of several hundred thousand dollars due to the laser, scanner, and sophisticated optics required. Although lower-end (e.g., $13-25K) SLS printers are emerging, these remain too costly for many users and applications. We are working to develop a new AM process which shares the benefits of SLS but promises significant advantages in terms of surface smoothness, feature definition, accuracy, and cost.
Steerable Robotic Cannula.
Minimally invasive procedures have been highly successful in improving outcomes, speeding recovery, limiting trauma, and allowing earlier intervention. Cannulas and related devices such as catheters and endoscopes are commonly used in such procedures, allowing surgical tools, diagnostic and therapeutic instruments, implants, and drugs to be safely introduced into the body, or to remove excised tissue or fluid. Yet, current devices are sometimes unable to access specific regions due to obstructions such as bone and sensitive organs. Therefore, a “holy grail” of minimally invasive medicine is a small-diameter, stable, controllable device that can follow an optimal 3-D path to reach virtually any anatomical target at any approach angle, and do so without iterative, time-consuming, traumatic manipulation by the clinician. We are developing a steerable robotic cannula able to grow into a complex 3-D shape within the body. In addition to medical applications, other potential (larger scale) applications include search and rescue, disaster cleanup, inspection and repair, and underwater and space exploration.
Additive Manufacturing with 'Click' Chemistry.
A major limitation of Additive Manufacturing (AM) is the short list of materials that can be used in the process. Hard, meltable plastics (thermoplastics), photopolymers, and metals dominate the application space of AM. To address these material limitations of AM while seeking to leverage its versatility, we are pursuing a project that seeks to develop, test, and optimize methods for using 'click' chemistry in AM. The thiol-ene reaction has gained widespread acceptance in the chemistry community over the last 15 years as a click reaction. A thiol-ene reaction occurs between a thiol (sulfur-containing compound) and an alkene (carbon-containing compound). The reaction is extremely fast and efficient, often taking place at room temperature. An important characteristic of thiol-ene polymers is the wide range of mechanical hardness and stiffness that is available from inexpensive and commercially available starting materials. We are working to address a variety of challenges associated with thiol-ene rheology, mixing, and curing, which we believe will lead to a 3-D printer capable of producing a variety of useful parts with unprecedented properties.