Jin-Huat Low

Customizable Soft Pneumatic Chamber–Gripper Devices for Delicate Surgical Manipulation

Traditional hard tissue grippers are limited in handling delicate soft tissues during surgery, particularly due to the high stress points that are generated on the soft tissue during gripping. In this study, customizable soft pneumatic chamber–gripper devices were designed to provide compliant gripping, so as to replace conventional tissue grippers such as the laparoscopic grasper or forceps in delicate tissue manipulation. The soft chamber–gripper device involves very simple design and control to generate actuation. It is fabricated from an elastomeric material using a modified soft lithography technique. The device consists of a gripper component that can be made up of one or more gripper arms with a pneumatic channel in each arm, and a chamber filled with air. The pneumatic channels are positioned close to the outer wall of the gripper arms and are connected to the chamber. Upon compression of the chamber, the pneumatic channels will inflate towards the outer walls, which thus bends the gripper arms and results in a closed gripping posture. This soft chamber–gripper device can be used to pick up objects of size up to 2 mm with a compressive force that is more than three times smaller than the grip force generated by traditional forceps. This will be useful in preventing tissue trauma during surgical manipulation, especially in nerve anastomosis. [DOI: 10.1115/1.4027688] Background

Customizable soft pneumatic finger actuators for hand orthotic and prosthetic applications

Traditional actuators are usually heavy, expensive and require a complex multi-component mechanical structure to generate human-like movement. Therefore, we proposed a lightweight soft finger actuator (25g) that is powered by pneumatic means to perform the grasping tasks. The soft actuators were fabricated using 3D-printing and soft lithography techniques. 5 healthy subjects (3 males and 2 females; age: 25±2.5 years) were recruited and they were asked to wear a hand orthosis with actuator attached on index finger to evaluate the performance of the soft actuators. The flexion angle at metacarpo-phalangeal joint is 55.7±19.0°, proximal interphalangeal joint is 141.2±2.0°, and distal interphalangeal joint is 126.6±3.0°. Also, three finger actuators were used to create a prosthetic hand, which is capable of grasping and holding objects with different sizes and weights up to 600 g. These studies showed the possibility of deploying these soft finger actuators in hand orthotic and prosthetic devices.

Soft haptics using soft actuator and soft sensor

In this paper, we presented fabric-based soft tactile actuator and soft sensor. The force characterization result indicates that the actuator is able to produce force up to about 2.20(±0.017)N, when it is supplied with 80kPa of pressurized air. Hence it is capable of producing sufficient amount of force, which surpasses the humans haptic perception threshold. The thin, sheet nature of the material creates lightweight actuator, which improves the payload-to-weight ratio. The pneumatic-based operation principle creates a safer human-machine interface. Thus, it eliminates possible occurrence of safety issues such as the danger of applying high voltages to users skin in case of malfunction. Direct force coupling of the soft actuator with the sensor is established to enable transmission of force information from the sensor to the actuator. The test profile indicates that the actuator is able to produce similar force profile as that of the sensor. This opens up possibility of developing soft tactile sensors and actuators based gloves, which can be paired and applied in virtual-reality based training and rehabilitation programs. Superimposition of multiple soft actuators would create an array that provides shape and size specific haptic feedback.

Rod-based Fabrication of Customizable Soft Robotic Pneumatic Gripper Devices for Delicate Tissue Manipulation.

Soft compliant gripping is essential in delicate surgical manipulation for minimizing the risk of tissue grip damage caused by high stress concentrations at the point of contact. It can be achieved by complementing traditional rigid grippers with soft robotic pneumatic gripper devices. This manuscript describes a rod-based approach that combined both 3D-printing and a modified soft lithography technique to fabricate the soft pneumatic gripper. In brief, the pneumatic featureless mold with chamber component is 3D-printed and the rods were used to create the pneumatic channels that connect to the chamber. This protocol eliminates the risk of channels occluding during the sealing process and the need for external air source or related control circuit. The soft gripper consists of a chamber filled with air, and one or more gripper arms with a pneumatic channel in each arm connected to the chamber. The pneumatic channel is positioned close to the outer wall to create different stiffness in the gripper arm. Upon compression of the chamber which generates pressure on the pneumatic channel, the gripper arm will bend inward to form a close grip posture because the outer wall area is more compliant. The soft gripper can be inserted into a 3D-printed handling tool with two different control modes for chamber compression: manual gripper mode with a movable piston, and robotic gripper mode with a linear actuator. The double-arm gripper with two actuatable arms was able to pick up objects of sizes up to 2 mm and yet generate lower compressive forces as compared to elastomer-coated and non-coated rigid grippers. The feasibility of having other designs, such as single-arm or hook gripper, was also demonstrated, which further highlighted the customizability of the soft gripper device, and its potential to be used in delicate surgical manipulation to reduce the risk of tissue grip damage.

Design and fabrication of a pneumatic soft robotic gripper for delicate surgical manipulation

Soft compliant gripping is a promising way to protect soft tissues from the grip damage caused by the high stress points in delicate surgical manipulation. In this paper, a new soft robotic gripper is designed to minimize the risk of soft tissues damage due to the over-gripping force generated by the conventional forceps. This new soft robotic gripper consists of a 3D-printed hook retractor shell, a soft inflatable actuator and two small rods. The ability of compliant grip is achieved by the inflated soft pneumatic actuator. Two small rods are used to separate the inflatable actuator into three-fingers-like bloats which can firmly grip the soft tissues by multi-contacts between the tissues and the gripper when the air pressure is applied to the pneumatic channel. In addition, it can protect the tissues against the harmful contacts with the rigid shell. The hook structure allows scooping-up motion during delicate surgical manipulation. The gripping tests and pulling force sensing experiments are carried out to evaluate the performance of the proposed soft robotic gripper.