thermia, and embolization, at the target location. [9,10] Recently, also soft-bodied wireless medical robots have become possible, where soft body enables programmable shape change, multifunctionality, and reconfiguration and safe operation inside the body. [11][12][13][14][15] Efforts have been made to develop and implement such robots, including fabrication of microscale soft robotic devices, and synthesis of biocompatible or biodegradable materials and strategies for locomotion inside the body. [16][17][18][19] However, applying these approaches have many limitations to operate safely and robustly in such complicated environments.Among various limitations, achieving strong adhesion to biological tissues whose surfaces are soft, rough, and wet is critical for the robots to efficiently implement various biomedical functions, including collecting bio-signals, bonding with unwanted derivatives and destroying them, healing wounds, and applying electrical impulses to nerves. [20][21][22][23] Although there are already commercial adhesives for tissues, the lack of long-term durability causes the failure of adhesion on the tissue. [24,25] Tough adhesives made of double-layered hydrogels [24][25][26] and dry double-sided tapes [27] were recently suggested for biological adhesives. These tissue adhesives are capable of strong adhesion to wet tissues, it is very difficult to detach them, indicating that a surgical operation is required for the detachment process. In addition, uncontrolled detachment can cause not only a problem of leaving an undesirable residue in Recently, the realization of minimally invasive medical interventions on targeted tissues using wireless small-scale medical robots has received an increasing attention. For effective implementation, such robots should have a strong adhesion capability to biological tissues and at the same time easy controlled detachment should be possible, which has been challenging. To address such issue, a small-scale soft robot with octopus-inspired hydrogel adhesive (OHA) is proposed. Hydrogels of different Young's moduli are adapted to achieve a biocompatible adhesive with strong wet adhesion by preventing the collapse of the octopus-inspired patterns during preloading. Introduction of poly(N-isopropylacrylamide) hydrogel for dome-like protuberance structure inside the sucker wall of polyethylene glycol diacrylate hydrogel provides a strong tissue attachment in underwater and at the same time enables easy detachment by temperature changes due to its temperature-dependent volume change property. It is finally demonstrated that the small-scale soft OHA robot can efficiently implement biomedical functions owing to strong adhesion and controllable detachment on biological tissues while operating inside the body. Such robots with repeatable tissue attachment and detachment possibility pave the way for future wireless soft miniature robots with minimally invasive medical interventions.

While suction cups prevail as common gripping tools for a wide range of real-world parts and surfaces, they often fail to seal the contact interface when engaging with irregular shapes and textured surfaces. In this work, the authors propose a suction-based soft robotic gripper where suction is created inside a self-sealing, highly conformable and thin flat elastic membrane contacting a given part surface. Such soft gripper can self-adapt the size of its effective suction area with respect to the applied load. The elastomeric membrane covering edge of the soft gripper can develop an air-tight self-sealing with parts even smaller than the gripper diameter. Such gripper shows 4 times higher adhesion than the one without the membrane on various textured surfaces. The two major advantages, underactuated self-adaptability and enhanced suction performance, allow the membrane-based suction mechanism to grip various three-dimensional (3D) geometries and delicate parts, such as egg, lime, apple, and even hydrogels without noticeable damage, which can have not been gripped with the previous adhesive microstructures-based and active suction-based soft grippers. The structural and material simplicity of the proposed soft gripper design can have a broad use in diverse fields, such as digital manufacturing, robotic manipulation, transfer printing, and medical gripping.

No abstract