System and methods for fabricating actuators and electrically actuated hydraulic solid materials

Abstract

With applications such as soft robotics being severely hindered by the lack of strong soft actuators, the invention provides a new soft-actuator material—Electrically Actuated Hydraulic Solid (EAHS) material—with a stress-density that outperforms any known electrically-actuatable material. One type of actuator is fabricated by making a closed cell that acts as highly paralyzed version of a standard paraffin actuator. Each cell exhibits microscopic expansion, which is summed to produce macroscopic motion. The closed cellular nature of the material allows the system to be cut and punctured and still operate. It can be produced in a lab or industrial scale, and can be formed using molding, 3D printing or cutting.

Description

[0001]This application claims the benefit of U.S. Provisional Application No. 62 / 163,156 filed May 18, 2015, incorporated by reference in its entirety.FIELD OF THE INVENTION[0002]The invention relates generally to actuators. More specifically, the invention is directed to a system and methods for fabricating actuators including wax actuators, for robotics and automation applications. In addition, the invention is directed to a new material including a conductive material component for use in the fabrication of actuators.BACKGROUND OF THE INVENTION[0003]Electrically driven polymeric actuators are an important basis for modern microfluidics, soft electronics, and soft robotics, and considered one of the bottlenecks of many applications for robotic and automation. Each one of the existing actuator technologies available today involves a difficult tradeoff between performance metrics. For example, dielectric actuators allow for high frequency responses and high strains, but are unable t...

AI Technical Summary

Benefits of technology

[0015]According to the invention, the EAHS material may be utilized in many different manufacturing processes, for example, cutting, casting and extruding processes including layer-wise fabrication. In addition, EAHS material may be used with a 3D printing device as described below. 3D printing of actuators has several potential advantages over traditionally manufactured actuators. 3D printing allows for rapid prototyping, allowing a user to iterate through design very quickly. A 3D printable actuator also allows a user to test a design for a new actuator without the costs associated with setting up tooling for a new traditionally manufactured design. 3D printing also offers added geometric complexity over traditional methods. This added geometric complexity may allow for new efficiencies to be achieved. 3D printing can also allow for many diverse material combinations which may allow for complete systems to be produced on a single device.

[0017]According to another embodiment of the invention, the cell including core are fabricated from an Electrically Actuated Hydraulic Solid (EAHS) material. An EAHS material may combine wax with other materials, with the combination 3D printable in the form of an actuator. Electrically actuated hydraulic solid (EAHS) materials are operable at relatively low voltages and currents, allowing for easy integration into many environments where high voltages or currents can be detrimental. The actuators can be formed by casting, additive manufacturing and mechanical operations allowing for the deployment of the actuators in small scale rapid prototyped systems and large scale commercial production.

[0019]The invention replicates the functionality and components of a traditional paraffin piston into a scalable material framework. Paraffin motor actuators are well known for their high force stroke and stable actuation, making them ideal for large quasi-static force generation. They operate at easily achievable voltages and currents, and have a slow cycle rate, making them robust against intermittent power disconnections. Paraffin motors have three distinct components: A chamber with an elastomeric membrane for containment of the wax, the wax itself, and a resistive heating source for converting current into thermal energy. Electrically Actuated Hydraulic Solid (EAHS) materials are a bulk material system where the functionality of these distinct components is replaced by the intrinsic behavior if three raw materials. This distributed cellular structure for the actuator makes it significantly more robust than its mono-cellular paraffin actuator counterpart. One advantage is that it can be punctured repeatedly and severed into section and each cell not damaged remains operational.

[0020]According to a particular embodiment, a phase change material (PCM) is dispersed in an elastomer matrix. The matrix is contains a network of conductive material. This allows the elastomeric matrix to act as a heater and membrane for the phase changing cells. When a voltage is applied, the system heats, the PCM expands generating an internal pressure. This pressure causes the overall structure to expand.

[0026]In order to address the challenges of existing actuator technologies, the invention identifies a new kind of bulk material actuator that offers a new performance tradeoff in stress density that is un-dominated by existing technologies. Whereas most compliant electroactive polymers attempt to induce a mechanical change by means of a charge migration, or charge separation, EAHS actuators uses a network of conductive materials suspended inside of an insulating elastomeric matrix to generate thermal energy. This energy is then transferred into cells of thermally expansive materials embedded inside of the matrix. The heated cells expand when they transition from a solid to a liquid as they are heated, generating internal pressure. The elastomer matrix acts as a containment system for the embedded phase change material, preventing the liquid phase from leaching out of the system. Each entrapped paraffin globule acts as an independent “micro-piston” as a result. Motion is bidirectional in that it is expansive on heating and shrinks on cooling. Large forces however are only generated during the expansion phase for a PCM. A PCM with a positive coefficient of thermal expansion from melting expand when heated. A PCM with a negative coefficient of thermal expansion from melting expand when cooled below the freezing point.

Problems solved by technology

3D printing also offers added geometric complexity over traditional methods.

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