|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 three rapidly-developing fields: 3-D printing, soft robotics, and printed electronics. The objective is to develop a new additive manufacturing technology that will allow for the first time the direct, automated manufacturing of integrated, multi-material devices such as soft robots with embedded actuators, sensors, and circuitry.
The challenge of manufacturing soft robotic components that include a large number of distributed actuators, sensors, and associated circuitry can be economically approached by 3-D printing multiple materials simultaneously. Today’s 3-D printing can only build structures from a single class of material (e.g., a polymer or a metal). Overcoming this limitation would be transformative and enable a wide range of sophisticated, active structures to be readily fabricated.
The results of this research will lead to a new manufacturing process for soft robots, an emerging class of devices promising greater safety, better manipulation of delicate and irregular objects, the ability to squeeze through small openings in search and rescue operations, new forms of locomotion, etc. Beyond robotics, applications of the research include wearable electronics, defense systems, advanced prosthetics, customizable consumer electronics, and smart implants.
The focus of the NSF project is to design, prototype, characterize, and optimize the new fabrication technology, and to design, simulate, build, and test actuators and sensors made using the process. A prototype 3-D printer has been developed, and several demonstration devices have been fabricated, including a working loudspeaker/voice coil actuator, linear variable differential transformer, rheostat, and membrane switch array. A portion of the project involves developing the ability to 3-D print soft elastomers, and good progress has been achieved to date.
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.
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.