A fiber is the base actuator unit. One nylon strand + one nichrome strand, bound with sewing thread, then twisted into a TCP coil. The nichrome is co-inserted inside the coil — not wrapped around the outside — for better thermal contact and integration.
Confirm nylon is PA6 or PA66 — not fluorocarbon (PVDF). Check packaging.
2
Lay parallel — side by side
Do not wrap yet. Just run them alongside each other. Nichrome sits next to nylon, not around it.
3
Bind tightly with sewing thread
Wrap tightly along the full length — coils touching, no gaps. Like thread whipping on a fishing rod. This is permanent — do not remove it later.
4
Tape one end, weight the other
Tape top end to a fixed surface. Attach a small weight (fishing sinker) to the bottom to keep tension while twisting.
5
Twist until it coils on itself
Twist from the top (~50–100 turns for 20cm). Stop when the strand spontaneously wants to spring into a helix. You'll feel it.
6
Heat-set in oven — 150°C, 10–15 min
Keep light tension (hang vertically with weight). Oven is most controlled. Heat gun works — keep moving. Hair dryer: not hot enough.
7
Cool, test resistance
Target: 10–50Ω per strand. Check with multimeter. Add more coats of graphite paint if using graphite method.
COARSE FIBER
NYLON0.1mm (label: 0.4), 120m roll
NICHROMEAWG34, 0.15mm ✓
RESISTANCETBD after testing
ROLEPower + load bearing
COOL TIME3–8 seconds
FINE FIBER
NYLON0.1mm PA6/PA66
NICHROMEAWG40, 0.08mm ✓
RESISTANCE~40Ω / 10cm
ROLEPre-tension + precision
COOL TIME~1 second (9× faster)
⚠ AWG40 nichrome is fragile — scratch surface lightly + apply flux before soldering. Order extra length. The co-insert method keeps it stable during coiling.