A research consortium composed of Zhejiang University of Technology, Tianjin University, Nanjing University of Science and Technology and Ritsumeikan University has created soft robotic fingers using 3D printing. This research aims to prove that multi-material 3D printing can be used not only to manufacture soft actuators, but also to manufacture functional sensors.
The robot finger is driven by an embedded single-electrode triboelectric curvature sensor (S-TECS), which can still induce bending curvature at an ultra-low operating frequency without external power. The researchers hope that this innovation will pave the way for a simple and fast manufacturing process, and that in the future, controllable soft robots can be produced.
Constructing robots using a mixture of soft materials and compliant structures is increasingly providing solutions to the challenges posed by the aging population. With the development of soft robot research and the development of new manufacturing methods, human-computer interaction has become more and more secure, and opened up new applications for the technology. Now, it is possible to directly print soft robots with airtight complex structures and hard components, such as the 3D printing jumping robot produced by Wyss Institute in 2015.
According to reports from members of the Research Alliance, this soft robot finger has integrated software sensors based on piezoelectric, conductive, magnetic and organic optical materials into its software robot design at the beginning of the design. However, these sensors may have disadvantages such as long prototyping time, unstable cable connections, complicated system assembly, and difficult system integration.
Therefore, the research team chose to use triboelectric sensors. This type of component provides high stretchability and sensitivity, so that the robot can actively sense and sense its deformation or response in real time. 3D printing plays a big role in this process. It can not only use a variety of materials, but also use a one-step printing process that shortens the time for prototyping. The researchers' S-TECS sensor is constructed by combining a triboelectric curvature sensor and a retractable electrode, avoiding the same integration complexity as the previous project.
The main body of this soft robot finger is composed of nine inflatable chambers connected to the main airway, each of which is rectangular to provide a flat surface for printing S-TECS patterns. The width of the hard-reinforced chamber is 2 mm, with two shims at both ends to support the top layer of S-TECS and maintain a height of 3 mm between the two layers. The additional finger can only be bent in one direction according to its chamber configuration. When the finger is bent, the top layer of S-TECS begins to approach the bottom layer until it is completely in contact, activating the contacts to charge and generate electricity.
The researchers used the Stratasys multi-material Objet350 3D printer to divide this soft robot finger into two parts: an enhanced soft body and connectors, and then produced them one by one. The pattern of S-TECS is printed directly on the top surface of the finger body to simplify the entire manufacturing process and reduce production time. The triboelectric layer and the flexible body of the device were produced using a friction-like AgilusBlack printing material because its tensile strength was 2.75 MPa and the elongation at break was 250%. The curing is performed at room temperature for 24 hours, and then the 3D printed parts of the fingers are screwed together, and the S-TECS is pasted through the silicone adhesive to complete the assembly.
By changing the surface structure, the force exerted on it and the automatically set working frequency to test the performance of the sensor under different pieces. It has not been found that integrating sensors with different soft materials will reduce the flexibility and adaptability of the entire robot system.
This test not only proved the effectiveness of S-TECS as a self-powered curvature sensor, but also proved the feasibility of using multi-material 3-D printing technology to create a flexible robot structure with triboelectric layer. Therefore, the researchers concluded that the method may be used in future robot applications that use advanced sensing functions.