Leveraging elastic instabilities for amplified performance: Spine-inspired high-speed and high-force soft robots

Abstract

Soft machines typically exhibit slow locomotion speed and low manipulation strength because of intrinsic limitations of soft materials. Here, we present a generic design principle that harnesses mechanical instability for a variety of spine-inspired fast and strong soft machines. Unlike most current soft robots that are designed as inherently and unimodally stable, our design leverages tunable snap-through bistability to fully explore the ability of soft robots to rapidly store and release energy within tens of milliseconds. We demonstrate this generic design principle with three high-performance soft machines: High-speed cheetah-like galloping crawlers with locomotion speeds of 2.68 body length/s, high-speed underwater swimmers (0.78 body length/s), and tunable low-to-high-force soft grippers with over 1 to 103 stiffness modulation (maximum load capacity is 11.4 kg). Our study establishes a new generic design paradigm of next-generation high-performance soft robots that are applicable for multifunctionality, different actuation methods, and materials at multiscales.

Status of and trends in soft pneumatic robotics

“…例如同样的变刚度功 能, 还可以利用原理与生物不同的变刚度材料来实 现 [139] . [72] , 模仿蛇类动物爬行方式的蛇形机器人 [263] , 模仿猎豹跳跃的四足机器人 [264] , 以及模仿植物触须的 缠绕机器人 [265] . 植物的自生长能力赋予了藤蔓植物无 限延伸的能力, 斯坦福大学和加州大学圣巴巴拉分校 [266] , 以及利用人工神经网络控制气动肌肉机械 臂 [267] , 甚至基于多模块或者集群机器人的群体智 [94] 使用TPU材料通过3D打印 制作的驱动器的寿命在250 kPa下为606次, 而在 400 kPa下为82次.…”

Leveraging Monostable and Bistable Pre‐Curved Bilayer Actuators for High‐Performance Multitask Soft Robots

“…Thus, it precludes the potential instability or bistability that often requires a pre‐curved shape to switch between two stable states. Very recently, bistability has been harnessed in soft robots for untethered directional propulsion, [ 7 ] autonomous control of airflow in soft bistable valves, [ 8 ] soft fluidic actuators with amplified responses, [ 9 ] and cheetah‐like galloping soft robots, [ 10 ] demonstrating its power in enhancing diverse high‐performance functionalities in soft robots.…”

“…Our recent study of LEAP soft robots demonstrated leveraging the strategy of tunable monostable and bistable mechanism for high‐speed locomotion and high‐strength manipulation. [ 10 ] It features a hybrid design of integrating a rigid bistable spine with 2D soft bending actuators. However, how to extend a similar strategy to design high‐performance entirely soft robotics without a rigid bistable spine remains largely unexplored.…”

Lightweight Self‐Forming Super‐Elastic Mechanical Metamaterials with Adaptive Stiffness

“…Flexible mechanical systems, including soft robotics, wearable devices, and compliant mechanisms have attracted tremendous research interest in the recent years. However, mimicking the ability of living organisms to maintain geometrical stability for precise manipulations while being resilient to tolerate shock and allow shape transformations remains a challenge due to the intrinsic limitation of materials [ 1,2 ] : High‐modulus materials such as metallic alloys and ceramics only allow small elastic strain before permanent deformation or fracture, while highly‐resilient materials such as hyper‐elastic elastomers suffer from low rigidity. Although natural super‐elastic shape memory materials offer a variable modulus arising from stress‐induced microscopic phase transformations (Figure S1b, Supporting Information), it is dedicated to only a small group of crystalline materials that suffer from insufficient strain capacity (<10%), high material density (5−10 g cm −3 ), and narrow operating temperature window.…”

“…Although natural super‐elastic shape memory materials offer a variable modulus arising from stress‐induced microscopic phase transformations (Figure S1b, Supporting Information), it is dedicated to only a small group of crystalline materials that suffer from insufficient strain capacity (<10%), high material density (5−10 g cm −3 ), and narrow operating temperature window. [ 3–6 ] However, recent studies in soft robotics are beginning to tackle this trade‐off, [ 1,2 ] with new horizons opened up by the introduction of mechanical metamaterials where macroscopic modular structures made from conventional materials are assembled to achieve extreme and programmable mechanical properties that are not found in naturally occurring materials. [ 7–10 ]…”