Magnetic Yarn
These yarns seem to have a mind of their own!
Yarn
- Magnetic Yarn
- Electromagnetic Yarn: Prototype 1
- Electromagnetic Yarn: Prototype 2
Magnetic Yarn (MY)Features:
- Cotton, Steel Fibers, and Neodymium Magnets
- Over the 18in length, the yarn is insulating. However because of 1 inch conductive (10-100 ohm) patches, the yarn's resistance is sensitive to posture and internal connection.
- Can be attached to any ferromagnetic surface (like your refrigerator)
Electromagnetic Yarn: Prototype 1 (EMY1) Features:
- Cotton, and Coated Copper Wire
- Electromagnets lend themselves well to the form factor of yarn and this 23 inch cord featuring 21 "beads" of coiled copper will behave as one.
- Over 2500 coils with area <20mm^2!
- Electromagnets can be re-oriented to direct field lines conveniently.
- Copper wire allows high current without burning up
- Actuation (bunching) may be possible
Electromagnetic Yarn: Prototype 2 (EMY2) Features:
- Cotton, Steel Fibers, Coated Copper Wire, and Neodymium Magnets
- Conceptually bunching and unbunching possible
- In development:
- 6 in. yarn incorporating all above materials
- 36 in. silicone dip-coated conductive thread
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Motivation
Re-imagining the fundamental yarns of a textile provides an opportunity to think about embedded intent and actuation schemes. We have seen in class materials that sense and communicate, but what about textiles that 'do' ? Nitinol wire has traditionally been the first approach to this question, but large switching times and required currents continue to be obstacles to adoption. Here we explore the first steps of incorporating magnetic components as an eventual alternative.
Construction
MY: Two spun strands were twisted, one entirely cotton and the other cotton, alternating with steel wool or steel wool with small magnet. After being twisted together, additional cotton and steel wool were added around both strands to help with cohesion and keeping the magnets in place.
EMY 1: Cotton balls were unrolled and laid on top of each other with ends fanned out. The cotton was then hand spun by twisting an S twist. Copper wire was then twisted as a Z twist and coiled ~120 times every few centimeters. The entire piece has a resistance of less than 30 ohms. The entire yarn is insulated and is only conductive end to end.
Note that a .5 T magnet did interact with the electomagnet enough to pick up the end when the current through the yarn was approximately 600 mA.
EMY2: Conductive thread was dip coated in a polymerizing silicone rubber and was removed after 6,7, and 8 minutes respectively. This was done to determine whether this could be a viable option to replace the coated copper wire. This has been ruled out for the time being. Techniques from MY and EMY1 were combined, unfortunately unsuccessfully. THe magnets selected were too strong and the yarn would not remain in the desired static position.
Opportunities for Improvement
With its short fibers and ease of untwisting, cotton proved challenging to use. We hypothesize that the electromagnetic would be stronger if the coils were around a ferromagnetic material rather than an air core. Fortunately our work with steel wool puts us in a good position to test this theory within the next iteration. Incorporating permanent magnets should be delayed until order of magnitude estimates are completed to determine sizing.