An Additive Millimeter‐Scale Fabrication Method for Soft Biocompatible Actuators and Sensors

Abstract

intuitiveness of the system. [6] Soft robotics represents a promising technology in this field because soft robots are constructed from compliant and flexible materials, resulting in machines that can safely interact with the surrounding environment. [7,8] They have already found applications in several research fields including the creation of biomimetic devices (given that the majority of the animal kingdom is mostly or entirely soft), [9][10][11][12] wearable robots, [13] and medical robots. [14] However, the low elastic modulus of soft materials can limit the interaction forces between the robots and the surgical target. To resolve the paradox of generating large forces from soft devices, stiffening mechanisms can be exploited, [15] such as granular jamming that has been integrated in a soft manipulator in order to effectively apply forces on a desired surgical target. [16] Soft biomedical robots are typically centimeter-scale [17] or larger but the current trend in minimally invasive procedures is to perform surgical tasks through small and remote entry points relative to the surgical target, [18] thus requiring millimeter-scale systems. Prior examples of soft millimeter-scale mechanisms include flexible microactuators for building robotic manipulators and grippers constructed by casting silicone rubber and nylon fibers in micromolds fabricated using electrical discharge machining, [19] soft microtentacles for grasping delicate objects consisting of elastomeric microtubes fabricated with a direct peeling-based soft-lithographic technique, [20] and a soft miniature hand fabricated through casting in micromolds and bonding silicone rubber through excimer light irradiation. [21] The forces that these actuators can exert are restricted to the millinewton range, thus suggested biomedical applications are limited to low-force surgical tasks, such as those performed in retinal surgery [22] and neurosurgery. [23] These limitations motivate the need for new millimeter-scale manufacturing technologies that combine soft materials with precision mechanisms to achieve distal articulation, integrated sensing, and effective force transmission with compliant, back-drivable, and safe devices for minimally invasive surgery.The "pop-up book microelectromechanical systems (MEMS)" manufacturing method creates 3D microstructures based on folding of multilayer rigid-flex laminates, [24] and enables fabrication of highly complex structures with embedded actuation and sensing. [25] Surgical applications of pop-up mechanisms have been proposed as self-assembling force sensors A hybrid manufacturing paradigm is introduced that combines pop-up book microelectromechanical systems (MEMS) manufacturing with softlithographic techniques to produce millimeter-scale mechanisms with embedded sensing and user-defined distributed compliance. This method combines accuracy, flexibility in material selection, scalability, and topological complexity with soft, biocompatible materials and microfluidics, paving the way for applications of soft fluid-p...

Soft Robotic Grippers

“…It can exert a force of 0.78 mN with a pressure of 60–70 kPa. Russo et al developed a millimeter‐scale articulated arm that is fluidically actuated for tissue handling …”

Soft Robotics

“…Pneumatically actuated soft robotics is limited by the availability of the obvious, standard components used to handle compressed gasses as soft structures. The most commonly used types of valves are conventional hard solenoid valves, located (usually) close to the source of gas rather than on the robot; easily integrated equivalents of the “Quake valves” (so useful in microfluidics) do not yet exist (although initial steps are evident), nor are there reliable functional analogs of the set of components (transistors, resistors, capacitors, and inductors) that form the elements of electrical circuits and that might—in principle—form the basis for “all‐soft” controllers.…”

Increasing the Dimensionality of Soft Microstructures through Injection‐Induced Self‐Folding

“…By merging well‐established techniques such as multilayer soft lithography and bulk micromachining, we combine the benefits of distinct fabrication techniques to create a new class of soft microstructures, which we call “microfluidic origami for reconfigurable pneumatic/hydraulic” (MORPH) systems. Previous work has demonstrated the possibility of exploiting laser cutting to release cut simple soft microactuators from an elastomeric matrix, while templateless prototyping of polydimethylsiloxane microfluidic structures exploiting laser machining has also been proposed . Here, we use lithographic techniques to manufacture elastomeric layers with embossed features that we then further modify by means of laser micromachining.…”