The research in artificial muscles has produced viable, low cost and efficient means in creating actuators for a variety of possible applications from energy-efficient windows to children’s toys. Research has been conducted into the use of nylon actuators for applications in soft robotics and medical devices such as prosthetic limbs.


The objective of the research here is to investigate the viability of making and using nylon artificial muscles to provide the force and static tensile strength required for daily use in an artificial hand for use in robotics or prosthetics. Here the focus is on finding a definitive, reproducible way of making nylon actuators with an arbitrary standard derived from the current research so that there is a consistent result in making the actuators for future use. The actuators were then tested individually and within a 3D printed hand as a viability test case. Preliminary tests of the exoskeleton hand show a static strength strong enough to lift >60lb of weight with no creep, while testing of the individual fibers indicates that it can lift loads over 100 times as much as human muscle of the same length and weight. The goal of this project is to create a viable and low-cost means of creating nylon actuators for use in a biomimicry approach to robotics and prosthetics.

unreleased coil 1


Since the discovery of the use of nylon monofilament for making spring actuators, people have been experimenting with the procedure to see if they could replicate the findings for themselves. This has led to a large following of people in conducting the experiments from every place such as the laboratories at universities to people at home in their garages. This is due to the low cost of manufacturing and the relative ease with which it takes to make the artificial muscles. The applications for the muscles have also been touted from the use of making a self-closing window to the next generation prosthetics.

Artificial muscles made of twisted polymer actuators (TPA) are actuators made of polymer filaments. These are usually of a polyamide such as nylon 6, nylon 6,6, polyethylene and cPEVA. The fibers are usually twisted either with a heating element such as a conductive thread until they self-coil or are painted with a conductive paint/coating once coiled. Once the actuator is created, the coils will expand or contract depending on their final chemical structure (chiral or heterochiral) bonds when a thermal, joule or chemical heating element is applied.

The phenomenon of self-coiled TPAs has been studied theoretically to produce the literature and mathematical results in regard to the geometry, force, and chemical make up of the completed coils. This information has proved useful in calculating initial length to final length of coils and strength of the TPAs in relation to the number of coils per diameter of the filament.

In this work, we investigated the processing and characterization of TPA from the nylon monofilament fishing line wound with a nichrome wire for Joule heating. Using equipment commonly available in an undergraduate physics laboratory testing focused on the creation process of an actuator using nylon 6 fishing line of a 0.70 mm diameter.


The Set-Up

Before the process of making the twisted coiled polymers (TCP) could get underway in earnest, a couple of devices needed to be made in order to facilitate the process.

The Method

Once the set-up is complete, it was on to make the TCPs for testing and future use.

The Results

There was a lot of data collected. It is just the tip of the iceberg when it comes to finding out what TCP's are capable of.


What is next? What was the overall finding? There is still more to know, more to do, but even a bit of new information is useful for moving forward.


All good research starts somewhere. A full list of references can be found here.