A Hot-Plugging Pinch Valve with Pressure-Controlled Logical Functions

Soft wearable robots utilize innovative textiles to create a mechanically active interface with human body. Compared to exoskeletons, they are more comfortable because they do not constrain the wearer’s joints with rigid structures. These robots are lightweight, conformal, and compliant. With minimal disturbance, they can not only enhance the abilities of healthy individuals by improving walking or lifting efficiency, but also assist those with muscle weakness or physical and neurological disorders. They can also be used in high-force kinesthetic haptics for training and entertainment. However, the miniaturization and integration of a large-scale and complex control system, with bulky and heavy actuators and energy units, pose significant challenges before the wearer can move autonomously in a soft wearable robotic suit. One aspect of these challenges is that the control valve is typically rigid and bulky.<br/>To address this issue, designing proper valves is crucial. Research on valves has grown significantly, displaying examples such as soft bi-stable valves and logic-enabled valves integrated with textiles. However, integrating these valves into pneumatic systems typically requires cutting out the tubing and reconnecting it. This process introduces considerable workload and increases the risk of leakage, especially in high-pressure applications. In the design and prototyping of wearable soft robots, the functionality and ease of application of control valves are greatly enhanced if they can be integrated into an operational system, for example, through a hot-plugging feature.<br/>In this work, we proposed a type of pinch valve with several notable characteristics. The basic working principle is that a silicone elastomer tube is pinched between a stiff ridge and a stiff plate, separately controlled by two soft pneumatic actuators. The application of the valve is significantly enhanced by a slotted frame, which provides a hot-plugging function as it allows the operational tube to be inserted into the valve without being cut. The valve is characterized by three crucial properties: (i) Flexibility in integration: the hot-plugging function allows for flexible integration of the valve into the system. (ii) Pressure control: it has the capability to open and close high-pressure systems using a lower control pressure, with a pressure ratio of at least 5. (iii) Logical functions: by controlling the pressure of the independent control actuators, the valve supports logical functions of NOT, NAND, and NOR gates, without the need to alter the pneumatic connections. Leveraging the NAND gate’s ability to detect when a signal input goes low, we demonstrated that the valve, with its NAND gate, can transform an unsecured gripper into a secured gripper.