T. Ranzani, S. Russo, C. J. Walsh, and R. J. Wood, “A soft pop-up proprioceptive actuator for minimally invasive surgery,” in The 9th Hamlyn Symposium on Medical Robotics, London, England, 2016.
T. Ranzani, S. Russo, C. J. Walsh, and R. J. Wood, “A soft suction-based end effector for endoluminal tissue manipulation,” in The 9th Hamlyn Symposium on Medical Robotics, London, England, 2016.
J. B. Gafford, T. Ranzani, S. Russo, S. B. Kesner, R. J. Wood, and C. J. Walsh, “Toward Medical Devices with integrated Mechanisms, Sensors and Actuators via Printed-Circuit MEMS,” ASME Journal of Medical Devices, vol. 11, no. 1, pp. 011007-011018, 2016. Publisher's VersionAbstract

Recent advances in medical robotics have initiated a transition from rigid serial manipulators to flexible or continuum robots capable of navigating to confined anatomy within the body. A desire for further procedure minimization is a key accelerator for the development of these flexible systems where the end goal is to provide access to the previously inaccessible anatomical workspaces and enable new minimally invasive surgical (MIS) procedures. While sophisticated navigation and control capabilities have been demonstrated for such systems, existing manufacturing approaches have limited the capabilities of millimeter-scale end-effectors for these flexible systems to date and, to achieve next generation highly functional end-effectors for surgical robots, advanced manufacturing approaches are required. We address this challenge by utilizing a disruptive 2D layer-by-layer precision fabrication process (inspired by printed circuit board manufacturing) that can create functional 3D mechanisms by folding 2D layers of materials which may be structural, flexible, adhesive, or conductive. Such an approach enables actuation, sensing, and circuitry to be directly integrated with the articulating features by selecting the appropriate materials during the layer-by-layer manufacturing process. To demonstrate the efficacy of this technology, we use it to fabricate three modular robotic components at the millimeter-scale: (1) sensors, (2) mechanisms, and (3) actuators. These modules could potentially be implemented into transendoscopic systems, enabling bilateral grasping, retraction and cutting, and could potentially mitigate challenging MIS interventions performed via endoscopy or flexible means. This research lays the ground work for new mechanism, sensor and actuation technologies that can be readily integrated via new millimeter-scale layer-by-layer manufacturing approaches.

S. Lee, F. Panizzolo, T. Miyatake, D. M. Rossi, C. Siviy, and C. J. Walsh, “Lower limb biomechanical analysis of unanticipated step on a bump,” in Dynamic Walking, Holly, Michigan, USA, 2016.
J. Bae, et al., “Assisting paretic ankle motion with a soft exosuit can reduce whole-body compensatory gait patterns and improve walking efficiency for patients after stroke,” in Dynamic Walking, Holly, Michigan, USA, 2016.
F. A. Panizzolo, et al., “A biologically-inspired multi-joint soft exosuit that can reduce the energy cost of loaded walking,” Journal of NeuroEngineering and Rehabilitation, vol. 13, no. 1, pp. 1-14, 2016. Publisher's VersionAbstract

Carrying load alters normal walking, imposes additional stress to the musculoskeletal system, and results in an increase in energy consumption and a consequent earlier onset of fatigue. This phenomenon is largely due to increased work requirements in lower extremity joints, in turn requiring higher muscle activation. The aim of this work was to assess the biomechanical and physiological effects of a multi-joint soft exosuit that applies assistive torques to the biological hip and ankle joints during loaded walking.

C. A. Cezar, E. T. Roche, H. H. Vandenburgh, G. N. Duda, C. J. Walsh, and D. J. Mooney, “Biologic-free mechanically induced muscle regeneration,” Proceedings of the National Academy of Sciences (PNAS), vol. 113, no. 6, pp. 1534-1539, 2016. Publisher's VersionAbstract

Severe skeletal muscle injuries are common and can lead to extensive fibrosis, scarring, and loss of function. Clinically, no therapeutic intervention exists that allows for a full functional restoration. As a result, both drug and cellular therapies are being widely investigated for treatment of muscle injury. Because muscle is known to respond to mechanical loading, we investigated instead whether a material system capable of massage-like compressions could promote regeneration. Magnetic actuation of biphasic ferrogel scaffolds implanted at the site of muscle injury resulted in uniform cyclic compressions that led to reduced fibrous capsule formation around the implant, as well as reduced fibrosis and inflammation in the injured muscle. In contrast, no significant effect of ferrogel actuation on muscle vascularization or perfusion was found. Strikingly, ferrogel-driven mechanical compressions led to enhanced muscle regeneration and a ∼threefold increase in maximum contractile force of the treated muscle at 2 wk compared with no-treatment controls. Although this study focuses on the repair of severely injured skeletal muscle, magnetically stimulated bioagent-free ferrogels may find broad utility in the field of regenerative medicine.

S. Lee, S. Crea, P. Malcolm, I. B. Galiana, A. T. Asbeck, and C. J. Walsh, “Controlling Negative and Positive Power at the Ankle with a Soft Exosuit,” in IEEE International Conference on Robotics and Automation (ICRA), Stockholm, Sweden, 2016. PDF
B. Quinlivan, et al., “Multi-articular soft exosuit continually reduces the metabolic cost of unloaded walking with increased assistance magnitude,” in Dynamic Walking, Holly, Michigan, USA, 2016.
C. Siviy, et al., “Optimization of soft exosuit peak force with ramp and step sweep protocol,” in Dynamic Walking, Holly, Michigan, USA, 2016.
Self-Assembling, Low-Cost, and Modular mm-Scale Force Sensor
J. B. Gafford, R. J. Wood, and C. J. Walsh, “Self-Assembling, Low-Cost, and Modular mm-Scale Force Sensor,” IEEE Sensors Journal, vol. 16, no. 1, pp. 69-76. [Cover Article], 2016. Publisher's VersionAbstract

The innovation in surgical robotics has seen a shift toward flexible systems that can access remote locations inside the body. However, a general reliance on the conventional fabrication techniques ultimately limits the complexity and the sophistication of the distal implementations of such systems, and poses a barrier to further innovation and widespread adoption. In this paper, we present a novel, self-assembling force sensor manufactured using a composite lamination fabrication process, wherein linkages pre-machined in the laminate provide the required degrees-of-freedom and fold patterns to facilitate self-assembly. Using the purely 2-D fabrication techniques, the energy contained within a planar elastic biasing element directly integrated into the laminate is released post-fabrication, allowing the sensor to self-assemble into its final 3-D shape. The sensors are batch-fabricated, further driving down the production costs. The transduction mechanism relies on the principle of light intensity modulation, which allows the sensor to detect axial forces with millinewton-level resolution. The geometry of the sensor was selected based on the size constraints inherent in minimally invasive surgery, as well as with a specific focus on optimizing the sensor's linearity. The sensor is unique from the fiber-based force sensors in that the emitter and the detector are encapsulated within the sensor itself. The bare sensor operates over a force range of 0-200 mN, with a sensitivity of 5 V/N and a resolution of 0.8 mN. The experimental results show that the sensor's stiffness can be tuned using a thicker material for the spring layer and/or encapsulation/integration with soft materials. The empirical validation shows that the sensor has the sensitivity and the resolution necessary to discern the biologically relevant forces in a simulated cannulation task.

D. L. Miranda, et al., “Sensory Enhancing Insoles Modify Gait during Inclined Treadmill Walking with Load,” Medicine & Science in Sports & Exercise, vol. 48, no. 5, pp. 860-868, 2016. Publisher's VersionAbstract

Introduction: Inclined walking while carrying a loaded backpack induces fatigue, which may destabilize gait and lead to injury. Stochastic resonance (SR) technology has been used to stabilize spatiotemporal gait characteristics of elderly individuals but has not been tested on healthy recreational athletes. Herein, we determined if sustained vigorous walking on an inclined surface while carrying a load destabilizes gait and if SR has a further effect.

Methods: Participants were fitted with a backpack weighing 30% of their body weight and asked to walk at a constant self-selected pace while their feet were tracked using an optical motion capture system. Their shoes were fitted with SR insoles that were set at 90% of the participant’s sensory threshold. The treadmill incline was increased every 5 min until volitional exhaustion after which the treadmill was returned to a level grade. SR stimulation was turned ON and OFF in a pairwise random fashion throughout the protocol. Spatiotemporal gait characteristics were calculated when SR was ON and OFF for the BASELINE period, the MAX perceived exertion period, and the POST period.

Results: Vigorous activity increases variability in the rhythmic stepping (stride time and stride length) and balance control (double support time and stride width) mechanisms of gait. Overall, SR increased stride width variability by 9% before, during, and after a fatiguing exercise.

Conclusion: The increased stride time and stride length variability may compromise the stability of gait during and after vigorous walking. However, participants may compensate by increasing double support time and stride width variability to maintain their stability under these adverse conditions. Furthermore, applying SR resulted in an additional increase of stride width variability and may potentially improve balance before, during, and after adverse walking conditions.

J. B. Gafford, S. Russo, T. Ranzani, R. J. Wood, and C. J. Walsh, “Snap-On Robotic Wrist Module for Enhanced Dexterity in Endoscopy,” in IEEE International Conference on Robotics and Automation (ICRA), Stockholm, Sweden, 2016. PDF
L. N. Awad, et al., “A soft exosuit for assisting poststroke walking,” in 9th World Congress of Neurorehabilitation, Philadelphia, PA, USA, 2016.
S. Russo, T. Ranzani, J. B. Gafford, C. J. Walsh, and R. J. Wood, “Soft pop-up mechanisms for micro surgical tools: design and characterization of compliant millimeter-scale articulated structures,” in IEEE International Conference on Robotics and Automation (ICRA), Stockholm, Sweden, 2016. PDF
L. N. Awad, et al., “Soft Wearable Robots Can Reduce the Energy Cost of Poststroke Walking: A Proof-of-Concept Study,” in Combined Sessions Meeting of the American Physical Therapy Association, Anaheim, CA, 2016.
P. Malcolm, et al., “Study of the contribution of negative work assistance at the ankle with a multi-articular soft exosuit during loaded walking,” in Dynamic Walking, Holly, Michigan, USA, 2016.
M. B. Yandell, D. Popov, B. Quinlivan, C. J. Walsh, and K. E. Zelik, “Systematic evaluation of human-exosuit physical interfaces,” in Dynamic Walking, Holly, Michigan, USA, 2016.
Y. Ding, et al., “Biomechanical and Physiological Evaluation of Multi-joint Assistance with Soft Exosuits,” IEEE Transactions on Neural Systems and Rehabilitation Engineering, vol. PP, no. 99, pp. 1, 2016. Publisher's VersionAbstract

To understand the effects of soft exosuits on human loaded walking, we developed a reconfigurable multi-joint actuation platform that can provide synchronized forces to the ankle and hip joints. Two different assistive strategies were evaluated on eight subjects walking on a treadmill at a speed of 1.25 m/s with a 23.8 kg backpack: 1) hip extension assistance and 2) multi-joint assistance (hip extension, ankle plantarflexion and hip flexion). Results show that the exosuit introduces minimum changes to kinematics and reduces biological joint moments. A reduction trend in muscular activity was observed for both conditions. On average, the exosuit reduced the metabolic cost of walking by 0.21 ± 0.04 W/kg and 0.67 ± 0.09 W/kg for hip extension assistance and multi-joint assistance respectively, which is equivalent to an average metabolic reduction of 4.6% and 14.6% demonstrating that soft exosuits can effectively improve human walking efficiency during load carriage without affecting natural walking gait. Moreover, it indicates that actuating multiple joints with soft exosuits provides a significant benefit to muscular activity and metabolic cost compared to actuating single joint.

Y. Ding, I. Galiana, C. Siviy, F. A. Panizzolo, and C. J. Walsh, “IMU-based Iterative Control for Hip Extension Assistance with a Soft Exosuit,” in IEEE International Conference on Robotics and Automation (ICRA), Stockholm, Sweden, 2016.Abstract

In this paper we describe an IMU-based iterative controller for hip extension assistance where the onset timing of assistance is based on an estimate of the maximum hip flexion angle. The controller was implemented on a mono-articular soft exosuit coupled to a lab-based multi-joint actuation platform that enables rapid reconfiguration of different sensors and control strategy implementation. The controller design is motivated by a model of the suit-human interface and utilizes an iterative control methodology that includes gait detection and step-by-step actuator position profile generation to control the onset timing, peak timing, and peak magnitude of the delivered force. This controller was evaluated on eight subjects walking on a treadmill at a speed of 1.5 m/s while carrying a load of 23 kg. Results showed that assistance could be delivered reliably across subjects. Specifically, for a given profile, the average delivered force started concurrently with the timing of the maximum hip flexion angle and reached its peak timing 22.7 ± 0.63% later in the gait cycle (desired 23%) with a peak magnitude of 198.2 ± 1.6 N (desired 200 N), equivalent to an average peak torque of 30.5 ± 4.7 Nm. This control approach was used to assess the metabolic effect of four different assistive profiles. Metabolic reductions ranging from 5.7% to 8.5% were found when comparing the powered conditions with the unpowered condition. This work enables studies to assess the biomechanical and physiological responses to different assistive profiles to determine the optimal hip extension assistance during walking.