The future generation of wearable assistive devices or smart trousers require considerable developments in various aspects ranging from low-level technology to final product prototypes. The devices must be lightweight, flexible, high force generation while being aesthetic, friendly and safe for human use. We are developing the devices based on pneumatic-driven and electrically-driven technology including smart materials and soft robotics. Below are our research contribution:
Soft Shrink-to-fit Sleeve
Soft fabric-based shrink-to-fit pneumatic sleeve was developed to replace the conventional, uncomfortable anchoring methods of existing exoskeletons and wearable assistive devices. Typically, the conventional approach contains rigid elements, which can consistently compress human skin and muscle and resist natural body movements. This can potentially cause harms to a user for long-time usage during daily activities. The soft shrink-to-fit sleeve provides an alternative solution, which is more comfortable, user-friendly and safer to be used on human body. It resembles normal clothing we are wearing every day. It can be activated at any time to provide assistance to the body and deactivated when no further assistance is required. The work was presented at 2022 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2022) in Kyoto, Japan. We are currently developing the device further for more complex functions.
Electro-pneumatic Pump (EPP) is a novel, lightweight, flexible, portable, soft electrically-driven pump with potential to replace conventional large, heavy pumps and compressors. It is capable of controlling air transferring to actuate pneumatic devices to deliver high contraction at fast response and generating high air flow rate to operate as soft pumps at low power consumption.The EPP was used to create an antagonistic mechanism, an arm-flexing robotic device, and a continuous-pumping system. These demonstrators show its versatility to integrate and enable next generation of smart assistive trousers.
Read the original paper: https://robotics.sciencemag.org/content/6/51/eabc3721
Recently, the EPP was further developed to produce higher maximum pressure of 12 kPa and maximum air flow rate of 239 ml/min. These improvements can expand its versatility for Soft Robotics.
Bubble Artificial Muscle
Bubble Artificial Muscle (BAM) is a flexible, inexpensive, pneumatic actuator, which can initialise fast contraction at low pressure and deliver high contraction and tension. This enables the BAM to contract up to 43% of its original length and exert maximum stress of 0.9 MPa, corresponding to 1000 times force-to-weight ratio. The BAM is simply made of a commercial plastic tubing with retaining rings, resulting in low weight and affordability. It is scalable and can be customised to achieve desired stroke and force generation using a developed mathematical model. This model can estimate its actuation performance and provide optimal designs for various specific actuation requirements, where the ideal, maximum expanding, “bubble” shape is consistently reached. An orthosis consisting of serial BAMs was built to perform a sit-to-stand transition on a human-like leg mechanism to demonstrate its potential to be used in the future wearable assistive devices.
Read the original paper: https://www.liebertpub.com/doi/10.1089/soro.2019.0157
Electro-ribbon Actuator (ERA) is an electrically-driven, origami actuator, which overcomes the limitation of conventional electrostatic actuators and generates much higher stress and strain. The ERA inserts additional liquid dielectric between two insulated electrodes, leading to high electrostatic-attractive-force amplification. As a result, it was able to contract over 99% of its length and exert force 1000 times higher than it own weigh, and its specific energy and specific power are equivalent to human muscle. The ERA can simply fabricated using various combination of conductive and insulated materials. It can be scalable, and complex structure can be built to deliver desired actuation, for instead, high-stroke and high-force morphologies, mulitactuator lattices, self-twisting spirals, spider-silk-inspired tensile actuator. In addition, some examples of the ERA applications include solenoids, grippers, locomoting robots and origami artificial muscles.
Read the original paper: https://robotics.sciencemag.org/content/3/25/eaau9795