Soft Haptic Devices Research Articles

Integrated Pneumatic Sensing and Actuation for Soft Haptic Devices

Integrated Pneumatic Sensing and Actuation for Soft Haptic Devices

Soft Electromagnetic Vibrotactile Actuators with Integrated Vibration Amplitude Sensing.

Soft vibrotactile devices have the potential to expand the functionality of emerging electronic skin technologies. However, those devices often lack the necessary overall performance, sensing-actuation feedback and control, and mechanical compliance for seamless integration on the skin. Here, we present soft haptic electromagnetic actuators that consist of intrinsically stretchable conductors, pressure-sensitive conductive foams, and soft magnetic composites. To minimize joule heating, high-performance stretchable composite conductors are developed based on in situ-grown silver nanoparticles formed within the silver flake framework. The conductors are laser-patterned to form soft and densely packed coils to further minimize heating. Soft pressure-sensitive conducting polymer-cellulose foams are developed and integrated to tune the resonance frequency and to provide internal resonator amplitude sensing in the resonators. The above components together with a soft magnet are assembled into soft vibrotactile devices providing high-performance actuation combined with amplitude sensing. We believe that soft haptic devices will be an essential component in future developments of multifunctional electronic skin for future human-computer and human-robotic interfaces.

A 3D-Printed Soft Haptic Device with Built-in Force Sensing Delivering Bio-Mimicked Feedback.

Haptics plays a significant role not only in the rehabilitation of neurological disorders, such as stroke, by substituting necessary cognitive information but also in human-computer interfaces (HCIs), which are now an integral part of the recently launched metaverse. This study proposes a unique, soft, monolithic haptic feedback device (SoHapS) that was directly manufactured using a low-cost and open-source fused deposition modeling (FDM) 3D printer by employing a combination of soft conductive and nonconductive thermoplastic polyurethane (TPU) materials (NinjaTek, USA). SoHapS consists of a soft bellow actuator and a soft resistive force sensor, which are optimized using finite element modeling (FEM). SoHapS was characterized both mechanically and electrically to assess its performance, and a dynamic model was developed to predict its force output with given pressure inputs. We demonstrated the efficacy of SoHapS in substituting biofeedback with tactile feedback, such as gripping force, and proprioceptive feedback, such as finger flexion-extension positions, in the context of teleoperation. With its intrinsic properties, SoHapS can be integrated into rehabilitation robots and robotic prostheses, as well as augmented, virtual, and mixed reality (AR/VR/MR) systems, to induce various types of bio-mimicked feedback.

Intrinsically Synchronized Flexible Visuo‐Haptic Device Operated by Single External Electric Field

AbstractProviding multisensory expression in a synchronized form helps human perception in human‐machine interfaces. Synchronized visuo‐haptic integration has been relatively less explored because the two expressions operate by different principles. This study demonstrates a flexible visuo‐haptic device that generates haptic sensation by electrovibration (EV) in conjunction with the synchronized optical expression by alternating‐current electroluminescence (ACEL). This study suggests material design and electric field modulation that are effective for both EV and electroluminescence (EL). Owing to the structural simplicity of the opto‐electrovibration (O‐EV) device, the EV and EL are intrinsically coupled under single electric field input. A curved O‐EV device simultaneously provides localized frictional tactile expression and localized luminescence on the touch screen. This study opens a simple material approach for multisensory expression that can be useful in soft haptic devices.

Novel Soft Haptic Biofeedback-Pilot Study on Postural Balance and Proprioception.

Sensory feedback is critical in proprioception and balance to orchestrate muscles to perform targeted motion(s). Biofeedback plays a significant role in substituting such sensory data when sensory functions of an individual are reduced or lost such as neurological disorders including stroke causing loss of sensory and motor functions requires compensation of both motor and sensory functions. Biofeedback substitution can be in the form of several means: mechanical, electrical, chemical and/or combination. This study proposes a soft monolithic haptic biofeedback device prototyped and pilot tests were conducted with healthy participants that balance and proprioception of the wearer were improved with applied mechanical stimuli on the lower limb(s). The soft monolithic haptic biofeedback device has been developed and manufactured using fused deposition modelling (FDM) that employs soft and flexible materials with low elastic moduli. Experimental results of the pilot tests show that the soft haptic device can effectively improve the balance of the wearer as much as can provide substitute proprioceptive feedback which are critical elements in robotic rehabilitation.

Elastomeric Haptic Devices for Virtual and Augmented Reality

AbstractSince the modern concepts for virtual and augmented reality are first introduced in the 1960's, the field has strived to develop technologies for immersive user experience in a fully or partially virtual environment. Despite the great progress in visual and auditory technologies, haptics has seen much slower technological advances. The challenge is because skin has densely packed mechanoreceptors distributed over a very large area with complex topography; devising an apparatus as targeted as an audio speaker or television for the localized sensory input of an ear canal or iris is more difficult. Furthermore, the soft and sensitive nature of the skin makes it difficult to apply solid state electronic solutions that can address large areas without causing discomfort. The maturing field of soft robotics offers potential solutions toward this challenge. In this article, the definition and history of virtual (VR) and augmented reality (AR) is first reviewed. Then an overview of haptic output and input technologies is presented, opportunities for soft robotics are identified, and mechanisms of intrinsically soft actuators and sensors are introduced. Finally, soft haptic output and input devices are reviewed with categorization by device forms, and examples of soft haptic devices in VR/AR environments are presented.

High-performance biocompatible nanobiocomposite artificial muscles based on ammonia-functionalized graphene nanoplatelets–cellulose acetate combined with PVDF

There are challenges in developing practically viable biopolymer-based actuators with ecofriendly, biocompatible, and biodegradable functionalities. Therefore, we propose a cellulose acetate (CA)-based ecofriendly soft-ionic networking actuator consisting of multifunctional additive polyvinylidene difluoride (PVDF), highly conductive ammonia-functionalized graphene nanoplatelets (AFGNPs), ionic liquids (IL), and flexible conducting polymer poly(3,4-ethylenedioxuthiopene)-polystyrene sulfonate (PEDOT:PSS) as an electrode. The proposed actuator exhibits a large bending displacement and short response time in an open-air environment, resulting from its enhanced electro-chemo-mechanical properties and strong ionic and interfacial interactions. In comparison with CA/PVDF-IL actuator, the CA/PVDF–IL–AFGNPs actuator demonstrates a considerably increased IL uptake and ion-exchange capacity of up to 71.04% and 300.6%, respectively, and an increase in the specific capacitance by over 3.64 times, which lead to bending actuation performances 2.21 and 1.87 times greater, respectively, under AC (4 V) and DC (4 V). Moreover, we demonstrate that a CA/PVDF–IL–AFGNPs actuator with a hierarchical structure shows values that are 1.32, 1.5, and 1.74 times larger than those of a planar actuator in DC (4 V), AC (3 V), and blocking force (4 V), respectively. The developed high-performance CA/PVDF–AFGNPs and the hierarchical surface texture of the patterned CA/PVDF–IL–AFGNPs actuators present these extraordinary achievements together with environmentally friendly materials, a low driving voltage, easy manufacturing, and high actuation performances. Therefore, they can be candidates for human-friendly products (e.g., biomedical devices, bioinspired robots, and soft haptic devices).

Design and Analysis of Pneumatic 2-DoF Soft Haptic Devices for Shear Display

Haptic devices use touch to enable communication in a salient and private manner. While most haptic devices are held or worn at the hand, there is recent interest in developing wearable haptic devices for the arms. This frees the hands for manipulation tasks, but creates challenges for wearability. One approach is to use pneumatically driven soft haptic devices that, compared to rigid devices, can be more readily worn due to their form factor and light weight. We propose a two-degree of freedom (2-DOF) pneumatic soft linear tactor that can be mounted on the forearm and provide shear force. The tactor is comprised of four soft fiber-constrained linear pneumatic actuators connected to a dome-shaped tactor head. The tactor can provide fast, repeatable forces on the order of 1 N in shear, in various directions in the plane of the skin surface. We demonstrate the tradeoffs of two housing schemes, one soft and one rigid, that mount the pneumatic soft linear actuator to the forearm. A user study demonstrated the performance of both versions of the device in providing directional cues, highlighting the challenges and importance of grounding soft wearable devices and the difficulties of designing haptic devices given the perceptual limits of the human forearm.

A Soft Robotic Wearable Wrist Device for Kinesthetic Haptic Feedback.

Advances in soft robotics provide a unique approach for delivering haptic feedback to a user by a soft wearable device. Such devices can apply forces directly on the human joints, while still maintaining the safety and flexibility necessary for use in close proximity to the human body. To take advantage of these properties, we present a new haptic wrist device using pressure-driven soft actuators called reverse pneumatic artificial muscles (rPAMs) mounted on four sides of the wrist. These actuators are originally pre-strained and release compressive stress under pressure, applying a safe torque around the wrist joints while being compact and portable, representing the first soft haptic device capable of real-time feedback. To demonstrate the functional utility of this device, we created a virtual path-following task, wherein the user employs the motion of their wrist to control their embodied agent. We used the haptic wrist device to assist the user in following the path and study their performance with and without haptic feedback in multiple scenarios. Our results quantify the effect of wearable soft robotic haptic feedback on user performance. Specifically, we observed that our haptic feedback system improved the performance of users following complicated paths in a statistically significant manner, but did not show improvement for simple linear paths. Based on our findings, we anticipate broader applications of wearable soft robotic haptic devices toward intuitive user interactions with robots, computers, and other users.

High-fidelity bioelectronic muscular actuator based on porous carboxylate bacterial cellulose membrane

Human-friendly electronic products, such as smart mobile phones, soft haptic devices, wearable electronics, and implantable or disposal biomedical devices, will require the use of high-performance durable soft electroactive actuators with eco-friendly, biocompatible, and biodegradable functionalities. Here, we report a high-fidelity bioelectronic muscular actuator based on porous carboxylate bacterial cellulose (CBC) membranes fabricated using the facile zinc oxide (ZnO) particulate leaching (PL) method. The proposed CZ-PL muscular actuator exhibits large deformation, low actuation voltage, fast response, and high-durability in open air environment. In particular, the CZ-PL membrane shows a dramatic increase in the ionic liquid uptake ratio, ionic exchange capacity, and ionic conductivity of up to 70.63%, 22.50%, and 18.2%, respectively, for CBC, resulting in a 5.8 times larger bending deformation than that of the pure CBC actuator. The developed high-performance CZ-PL muscular actuator can be a promising candidate for meeting the tight requirements of human-friendly electronic devices such as wearable devices, biomimetic robots, and biomedical active devices.

High‐Fidelity Bioelectronic Muscular Actuator Based on Graphene‐Mediated and TEMPO‐Oxidized Bacterial Cellulose

High‐performance electoactive artificial muscles with biofriendly, biodegradable, and biocompatible functionalities have attracted enormous attention in the era of human friendly electronic devices such as wearable electronics, soft haptic devices, and implantable or disposal biomedical devices. Here, a high‐fidelity bioelectronic soft actuator is reported based on biofriendly 2,2,6,6‐tetramethylpiperidine‐1‐oxyl radical‐oxidized bacterial cellulose (TOBC), chemically modified graphene, and ionic liquid [EMIM][BF4] as plasticizer, thereby realizing large deformable, faster, biodegradable, air working, and highly durable TOBC‐IL‐G muscular actuator. Especially, the TOBC‐IL‐G(0.10 wt%) membrane shows a dramatic increment of the ionic conductivity up to 120%, of specific capacitance up to 95%, of tensile modulus up to 63%, and of tensile strength up to 60%, for TOBC‐IL, resulting in 2.3 times larger bending deformation without serious back‐relaxation phenomena. The developed high‐performance and durable bioelectronic muscular actuator can be a promising candidate for satisfying the tight requirements of human‐related bioengineering as well as biomimetic robotics and biomedical active devices.