Global Artificial Muscles: The Future of Robotic Limbs and Exoskeletons

Global Artificial Muscle

Artificial muscles, also known as synthetic muscles, are materials and devices that mimic the behavior of natural muscles in mammals. By combining materials science and engineering, researchers are working to develop new types of these muscles that can power prosthetic devices, exoskeletons and robots.

Materials Behind Artificial Muscles

There are a few main categories of materials that are being used and developed for these muscles. Some commonly used materials include shape memory alloys, electrolytes, carbon nanotubes and conjugated polymers.

Shape memory alloys are metals that can be deformed from their initial shape but will return to that shape upon heating. Nickel-titanium alloys are a commonly used shape memory alloy for these muscles due to their flexibility and strength. When thin wires made from these alloys are heated, they contract and can apply forces similar to natural muscles.

Ionic polymer metal composites, also called ionic polymer-metal composites or IPMCs, are soft polymers combined with thin metal plates. When a low voltage is applied, the polymer absorbs or expels ions which causes it to bend. These muscles can replicate human-like movements and have potential uses in soft robotics.

Conjugated polymers are carbon-based polymers that can undergo redox reactions when an electric current is applied. The polymers undergo swelling and dimensional changes as oxidation and reduction move charges through their structures. Some conjugated polymers have been developed that can lift over a thousand times their own weight, making them promising for use in these muscles.

Applications in Robotic Limbs and Exoskeletons

Researchers are working on implementing these muscles into assistive devices to help people with mobility issues. Some important applications include:

Prosthetic Limbs - Shape memory alloys and IPMC Global Artificial Muscles are being used to power finger and hand movements in prosthetics. As the materials get stronger, they could enable more dexterous and natural arm movements.

Exoskeletons - Full body exoskeleton frames use these muscles at the joints to support and strengthen human movements. They are being developed for applications like assisting the elderly or helping workers lift heavy objects.

Soft Exosuits - Wearable assistive devices made of flexible artificial muscles are called soft exosuits. They apply assistance precisely where needed without restricting natural motions. Researchers are developing exosuits that can reduce the energy cost of walking or help stroke patients regain mobility.

Lower Limb Prosthetics - For leg prosthetics, these muscles are being integrated into ankle and knee joints to restore a more natural walking gait. This reduces risks of falls or injuries compared to rigid prosthetics.

Challenges and Future Outlook

While significant progress has been made, there are still challenges to overcome before artificial muscles can fully replicate natural muscle capabilities:

- Strength and Force Generation - Most synthetic muscles cannot yet match the power-to-weight ratios of real muscles. Materials science advancements are needed.

- Durability and Lifespan - Undergoing millions of contraction cycles, natural muscles rarely fatigue. But artificial muscles still lack comparable endurance in testing.

- Control and Sensing - Natural muscles receive precise neural signals, but prosthetics have difficulty mimicking this level of feedback and coordination.

- Biocompatibility - For implantable devices, artificial muscles and their degradation products must be demonstrated as safe for long-term tissue and organ contact.

Research in multi-functional materials, neuromuscular interfaces, and integration of artificial muscle actuators into complete limb systems will help address these challenges. With continued progress, highly dexterous and lightweight prosthetics or exoskeletons powered by synthetic muscles could become widespread realities within the next 10-20 years. These technologies hold tremendous promise to vastly improve quality of life for individuals with disabilities