Facebook released a series of AR / AVR information at connect 2020 in mid September, covering the latest hardware products, software products, solutions, developer services, cutting-edge technology research, etc. However, this activity did not introduce a promising glove project of FRL research.
In fact, FRL research is working with researchers at Cornell University to develop a 3D printed glove with flexible pneumatic actuators that can “measure local forces” and provide “tactile feedback” to users.
Tactile gloves must meet two conditions: on the one hand, it must be light and able to adapt to the flexible movement of hands and fingers; on the other hand, it must be durable enough to use and clean a thousand times without damage. Therefore, it puts forward very high requirements for application materials.
Compared with traditional synthetic materials, flexible materials have inherent advantages of shock absorption, load management and passive energy recovery. Flexible organization is particularly useful in robotics because of its low modulus and high scalability, which allows the manufacture of flexible robots that can change into almost any state without breaking.
Due to its heat resistance and chemical inertia, silicone rubber is an ideal material for making flexible components. However, the traditional manufacturing process can only produce simple prism. Recent rubber research has been using liquid silicone materials as extrusion 3D printing inks, but their modification weakens the crosslinking density.
Due to the reduced strength of the materials, the samples based on the extrusion process show limited print fidelity in terms of drapability, resulting in their slump before curing. Other research groups have tried to use light cured (SLA) technology to produce liquid resin parts, providing greater stability, but less toughness than commercial rubber.
In addition, SLA processing requires the use of stable low viscosity resins, so traditional methods cannot be used to enhance them. As an alternative strategy, the FRL research and Cornell team proposed using double networks to provide stronger rubber, which means that the two polymers occupy the same volume.
In this new method, the two polymer layers have different properties and functions. The outer layer is fragile and dissipates energy, while the second layer network remains intact and can withstand heavy loads. Using these dnss, researchers say they can not only match the strength and quality of commercial rubber, but also combine printed objects with other substrates.
In order to create this new material, the researchers used the thiol Silene formula as the basis, because it has the characteristics of low viscosity, rapid gelation and high reaction conversion. In contrast, the secondary polymer in DN needs to form its own unique network, so the team used moldmaxseries resin because of its inherent toughness and rigidity.
In the two-stage combination process, the light cured mercaptan silicone and mechanically stable condensation cured silicone were formed in turn. Subsequent infrared spectroscopy tests showed that the relative mass fraction of the two networks could be changed, allowing researchers to adjust the printability and mechanical properties of the resin.
For example, by increasing the “green” section from 0.008 MPa to 0.92 MPa, increasing the load on the condensing network can significantly improve the tensile strength of the final part. Using four different tin based rubber materials, the team then experimented with changing the substrate in DN to adjust its mechanical properties.
Next, the researchers built a prototype of a tactile feedback glove using one of the materials and four 3D printed pneumatic actuators. Where air blows into the chamber and causes the material to expand to simulate resistance. Experiments show that the device not only allows dexterous operation, but also the bonding structure withstands hundreds of motion cycles in 10 months.