Jun Shintake

Related publications (36)

A variable stiffness magnetic catheter made of a conductive shape memory polymer for minimally invasive surgery

Dario Floreano, Jun Shintake

A hollow variable stiffness thread including a flexible inner tube, a conductive shape memory polymer (CSMP) layer arranged around the inner tube forming a variable stiffness zone, a flexible encapsulation layer arranged around the CSMP layer, and a first electrode and a second electrode, at least a portion of the first and the second electrodes being in contact with the CSMP layer.

2023

A Variable Stiffness Magnetic Catheter Made of a Conductive Phase-Change Polymer for Minimally Invasive Surgery

Dario Floreano, Jun Shintake

Variable stiffness (VS) is an important feature that significantly enhances the dexterity of magnetic catheters used in minimally invasive surgeries. Existing magnetic catheters with VS consist of sensors, heaters, and tubular structures filled with low melting point alloys, which have a large stiffness change ratio but are toxic to humans. In this paper, a VS magnetic catheter is described for minimally invasive surgery; the catheter is based on a novel variable stiffness thread (VST), which is made of a conductive shape memory polymer (CSMP). The CSMP is nontoxic and simultaneously serves as a heater, a temperature sensor, and a VS substrate. The VST is made through a new scalable fabrication process, which consists of a dipping technique that enables the fabrication of threads with the desired electrical resistance and thickness (with a step size of 70 µm). Selective bending of a multisegmented VST catheter with a diameter of 2.0 mm under an external magnetic field of 20 mT is demonstrated. Compared to existing proof-of-concept VS catheters for cardiac ablation, each integrated VST segment has the lowest wall thickness of 0.75 mm and an outer diameter of 2.0 mm. The segment bends up to 51° and exhibits a stiffness change factor of 21.

2022

Enhancement of Pressure-Sensitive Adhesive by CO2 Laser Treatment

Dario Floreano, Vivek Ramachandran, Jun Shintake, Jianhang Yang

Pressure-sensitive adhesives (PSAs) are polymeric films that can be adhered to and detached from surfaces without leaving residue. Researchers are looking to enhance the bond strength between PSAs and different substrates. It can be achieved by tuning PSA's peeling, shear, and tack properties for every specific case. ‘Very High Bond’ (VHB) is a widely used PSA because of its high compliance suitable for stretchable and soft-matter devices. In this study, a simple and fast surface treatment approach to modify the adhesion of VHB by CO2 laser engraving is reported. We characterized this surface treatment method for VHB with different substrates. Multiple laser settings were tested for each material combination to determine the conditions at which the surface adhesion would be the highest. Tests on mechanical properties, ablation directions, chemical composition, tackiness, surface viscosity, and peeling forces were conducted to understand the adhesion and viscoelasticity changes. A higher concentration of non-crosslinked materials was determined in the VHB structure after treatment than before. Thus, we reason that laser treatment changes the surface adhesion of the PSA by cleavage of the polymer network. This work provides a simple route for tuning peeling, shear, and tack forces of a popular VHB using common equipment.

2022

Stretchable and Soft Electroadhesion Using Liquid‐Metal Subsurface Microelectrodes

Dario Floreano, Egor Piskarev, Jun Shintake

Electroadhesion is an attractive mechanism to electrically modulate adhesion to surfaces. Electroadhesion arises from the interaction of electric fields with conductive or dielectric materials. Electroadhesion devices consist of in-plane, interdigitated electrodes that generate out-of-plane electric fields, which increase adhesion with target surfaces. To date, these electrodes have predominantly been composed of carbonaceous materials. Here, liquid metal is utilized to create the electrodes in silicone substrates. Liquid metal can be patterned in a variety of unique ways, including microfluidic injection, spray deposition, or printing. These electrodes have nearly unlimited deformation in soft and stretchable substrates while maintaining metallic conductivity. The experimental results show that stretching improves electroadhesion performance due to the changes in geometry of the electrodes and insulation layer, whose behaviors are theoretically predictable. The use of liquid-filled, sub-surface microchannels can help to maintain contact between the elastomer and substrate during peeling due to the surface stresses caused by the capillary pressure. This approach to electroadhesion can be implemented in ultra-stretchable and soft substrates, including those used in soft robotics, due to the inherently compliant and deformable electrical conductivity of the liquid metal electrodes.

2021

Bio-Inspired Tensegrity Fish Robot

Dario Floreano, Yusuke Ikemoto, Timothée John Martin Peter, Jun Shintake, Davide Zappetti

This paper presents a method to create fish-like robots with tensegrity systems and describes a prototype modeled on the body shape of the rainbow trout with a length of 400 mm and a mass of 102 g that is driven by a waterproof servomotor. The structure of the tensegrity robot consists of rigid body segments and elastic cables that represent bone/tissue and muscles of fish, respectively. This structural configuration employing the tensegrity class 2 is much simpler than other tensegrity-based underwater robots. It also allows the tuning of the mechanical stiffness, which is often said to be an important factor in fish swimming. In our robot, the body stiffness can be tuned by changing the cross-section of the cables and their pre-stretch ratio. We characterize the robot in terms of body stiffness, swimming speed, and thrust force while varying the body stiffness i.e., the cross-section of the elastic cables. The results show that the body stiffness of the robot can be designed to approximate that of the real fish and modulate its performance characteristics. The measured swimming speed of the robot is 0.23 m/s (0.58 BL/s), which is comparable to other fish robots of the same type. Strouhal number of robot 0.54 is close to that of the natural counterpart, suggesting that the presented method is an effective engineering approach to realize the swimming characteristics of real fish.

2020

Lighter and Stronger: Cofabricated Electrodes and Variable Stiffness Elements in Dielectric Actuators

Dario Floreano, Egor Piskarev, Vivek Ramachandran, Jun Shintake

The inherent compliance of soft robots often makes it difficult for them to exert forces on surrounding surfaces or withstand mechanical loading. Controlled stiffness is a solution to empower soft robots with the ability to apply large forces on their environments and sustain external loads without deformations. Herein, a compact, soft actuator composed of a shared electrode used for both electrostatic actuation and variable stiffness is described. The device operates as a dielectric elastomer actuator, while variable stiffness is provided by a shared electrode made of gallium. The fabricated actuator, namely variable stiffness dielectric elastomer actuator (VSDEA), has a compact and lightweight structure with a thickness of 930 μm and a mass of 0.7 g. It exhibits a stiffness change of 183×, a bending angle of 31°, and a blocked force of 0.65 mN. Thanks to the lightweight feature, the stiffness change per mass of the actuator (261× g−1) is 2.6 times higher than that of the other type of VSDEA that has no shared electrode.

2020

Delicate yet strong: characterizing the electro-adhesion lifting force with a soft gripper

Vito Cacucciolo, Herbert Shea, Jun Shintake

Compliant grippers are one of the most promising soft robotic devices for industrial tasks. Soft grippers dramatically simplify grasping control because the gripper automatically conforms to the object's shape. A common limitation of soft structures is that they can only generate low forces, limiting grasping ability. One approach to increase the holding force is to increase the shear force by using controlled adhesion: the lifting force is thus increased, while the clamping force can be kept low, important for manipulating delicate objects. In this work, we explore the lifting force generated with a soft gripper using electroadhesion. We show that this force is highly dependent on the holding posture, which depends on both the shape of the gripper and the shape of the object. For a 1 cm(2) electroadhesion area, we measure maximum lifting forces up to 16 N, strongly dependent on object's shape. Reliability is also an essential feature to move soft robots into industrial scenarios. The gripper survived over 100 cycles at high load with no damage, showing its high robustness. Combining electroadhesion and dielectric elastomers actuators, our soft gripper generates grasping forces so high that we reach the structural limits of the rigid plastic frame, yet it is delicate enough to gently pick up and release a cherry tomato.

IEEE2019

Phase Changing Materials-Based Variable-Stiffness Tensegrity Structures

Dario Floreano, Jun Shintake, Davide Zappetti

Soft robots leverage deformable bodies to achieve different types of locomotion, improve transportability, and safely navigate cluttered environments. In this context, variable-stiffness structures provide soft robots with additional properties, such as the ability to increase forces transmitted to the environment, to lock into different body configurations, and to reduce the number of actuators required for morphological change. Tensegrity structures have been recently proposed as a biologically inspired design principle for soft robots. However, the few examples of tensegrity structures with variable stiffness displayed relatively small stiffness change (i.e., by a factor of 3) or resorted to multiple and bulky actuators. In this article, we describe a novel design approach to variable-stiffness tensegrity structures (VSTSs) that relies on the use of variable-stiffness cables (VSCs). As an example, we describe the design and implementation of a three-strut tensegrity structure with VSCs made of low melting point alloys. The resulting VSTS displays unprecedented stiffness changes by a factor of 28 in compression and 13 in bending. We show the capabilities of the proposed VSTS in three validation scenarios with different tensegrity architectures: (1) a beam with tunable load-bearing capability, (2) a structure that can self-deploy and lock its shape in both deployed and undeployed states, and (3) a joint with underactuated shape deformations.

2019

Stretchable pumps for soft machines

Vito Cacucciolo, Dario Floreano, Yu Kuwajima, Herbert Shea, Jun Shintake

Machines made of soft materials bridge life sciences and engineering. Advances in soft materials have led to skin-like sensors and muscle-like actuators for soft robots and wearable devices. Flexible or stretchable counterparts of most key mechatronic components have been developed, principally using fluidically driven systems6–8; other reported mechanisms include electrostatic, stimuli-responsive gels and thermally responsive materials such as liquid metals and shape-memory polymers. Despite the widespread use of fluidic actuation, there have been few soft counterparts of pumps or compressors, limiting the portability and autonomy of soft machines. Here we describe a class of soft-matter bidirectional pumps based on charge-injection electrohydrodynamics. These solid-state pumps are flexible, stretchable, modular, scalable, quiet and rapid. By integrating the pump into a glove, we demonstrate wearable active thermal management. Embedding the pump in an inflatable structure produces a self-contained fluidic ‘muscle’. The stretchable pumps have potential uses in wearable laboratory-on-a-chip and microfluidic sensors, thermally active clothing and autonomous soft robots.

2019

All‐Fabric Wearable Electroadhesive Clutch

Dario Floreano, Vivek Ramachandran, Jun Shintake

A lightweight, textile fabricated, haptic device consisting of an electrostatic adhesive clutch is introduced, which can constrain body movement when activated at low power (≈1 mW). The clutch electrodes are composite structures, prepared by coating copper‐plated polyester fabric with thin films of high‐κ dielectric ink. When voltage is applied across a pair of overlapping electrodes, the charge separation created between the overlapped surfaces gives rise to adhesive forces that resist tensile loads along the electrode surface. The clutch is arranged in parallel with a sheet of knitted fabric, which exhibits low‐stiffness spring‐like characteristics, thus decreasing load resistance when the clutch is deactivated. Mechanical tests are carried out to assess the dependency on scaling and loading rate at different voltages. The load‐bearing capacity of the device is experimentally shown to sustain a 10 kg load for a clutch pair with 120 × 70 mm2 dielectric overlap, when activated at 400 V. Current‐dependent charging and discharging times that can be as low as 15 ms are presented. To exemplify its pertinence in wearable applications, the device is used as an elbow joint constraint, exhibiting its conformability to curvatures and suitability for skin‐mounted applications.

2018