Prosthetic limbs made user-friendly with polymer based elastic sensors

June 27, 2017, University of Electro Communications
Prosthetic limbs made user-friendly with polymer based elastic sensors.
Design of the PPy band. Credit: University of Electro Communications

Prostheses are used to replace body parts damaged through trauma or congenital deficiencies. A wide range of prosthetic limbs exist including myoelectric prostheses that operate by so-called surface electromyography (sEMG), where pulses of electrical voltage from muscles are relayed to sensors when users want to initiate a movement. However, a major problem limit the application of such prosthetic devices is the instability of the electrical signals measured.

Now, Yinlai Jiang and colleagues at the University of Electro-Communications, Tokyo, and collaborators in China, have developed sensors made of polypyrrole (PPy), a conductive polymer that is sewn onto elastic bands. The flexibility of these bands makes them much easier for patients to wear with one hand, and highly ergonomic.

The functionality of the sensors was tested by comparing the signals measured with the proposed sensor and those with traditional wet Ag/Agcl electrodes. Four subjects were recruited to wear sensors on their arms using both type of electrodes. Subsequently, signals measured by each kind of electrode when contracting the same set of muscles was measured. The quality of the signals measured in both cases had high correlation, indicating the functioning of PPy electrodes to be equivalent to traditional ones. Furthermore, usually provide five basic motions and the recognition of each motion by the PPy sensor was also confirmed to be similar to traditional electrodes.

The PPy are in direct contact with skin, in contrast to the wet electrodes that are covered by an electrolyte gel. This -skin contact often exacerbates the source impedance or resistance in the circuit, masking the quality of signal. Balancing the source impedance however, restores the signal to noise ratio. The researchers conclude, "Source impedances, rather than the shape and the size of the electrodes, are important for sEMG measurement." This renders flexibility in the design of the PPy electrodes.

Ag/Agcl electrodes vs. PPy electrodes worn on similar regions of the arm. Credit: University of Electro Communications

The research team plans to expand this study with trials for a longer duration, and more patients. Given this study's promising results, the rigorous training, which patients must undergo to stabilize signals for myoelectric control, could be made much simpler in the future.

Explore further: Wearable sensor clears path to long-term EKG, EMG monitoring

More information: Yinlai Jiang et al. sEMG Sensor Using Polypyrrole-Coated Nonwoven Fabric Sheet for Practical Control of Prosthetic Hand, Frontiers in Neuroscience (2017). DOI: 10.3389/fnins.2017.00033

Related Stories

Wearable sensor clears path to long-term EKG, EMG monitoring

January 20, 2015

Researchers from North Carolina State University have developed a new, wearable sensor that uses silver nanowires to monitor electrophysiological signals, such as electrocardiography (EKG) or electromyography (EMG). The new ...

Big improvements to brain-computer interface

February 16, 2017

When people suffer spinal cord injuries and lose mobility in their limbs, it's a neural signal processing problem. The brain can still send clear electrical impulses and the limbs can still receive them, but the signal gets ...

Bionic leg undergoing clinical trials

April 22, 2011

(Medical Xpress) -- A "bionic" leg designed for people who have lost a lower leg is undergoing clinical trials sponsored by the US Army. The researchers hope the leg will be able to learn the patient's nerve signal patterns ...

Recommended for you

Permanent, wireless self-charging system using NIR band

October 8, 2018

As wearable devices are emerging, there are numerous studies on wireless charging systems. Here, a KAIST research team has developed a permanent, wireless self-charging platform for low-power wearable electronics by converting ...

Facebook launches AI video-calling device 'Portal'

October 8, 2018

Facebook on Monday launched a range of AI-powered video-calling devices, a strategic revolution for the social network giant which is aiming for a slice of the smart speaker market that is currently dominated by Amazon and ...

Artificial enzymes convert solar energy into hydrogen gas

October 4, 2018

In a new scientific article, researchers at Uppsala University describe how, using a completely new method, they have synthesised an artificial enzyme that functions in the metabolism of living cells. These enzymes can utilize ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.