Red Blood Cell
A flexible biconcave disk, for all your flexible biconcave disk needs!
Use a combination of yarn and needle size to get a firm gauge so the stuffing won't show through. For the cell pictured, I used fingering weight yarn held double with US 7 needles, and the finished size is 3¼" x 3".
Techniques used include knitting in the round, increasing, and decreasing.
Stitches and abbreviations:
kfb: increase by knitting in the front and back of the stitch
k2tog: decrease by knitting two stitches together
Note: The number of stitches and the grouping of increases and decreases are intentionally a bit irregular for a more organic look. This might make the instructions look complicated, but the basic idea is just to increase or decrease by 8 stitches on most of the increase or decrease rounds. Since the total number of stitches is not divisible by 8, there will be two odd stitches scattered here and there in each of those increase and decrease rounds.
Leaving a long tail, cast on 6 stitches. Distribute on needles for knitting in the round.
Round 1: *k1, [kfb] twice, repeat from * (10 stitches)
Round 2: *[kfb] twice, k1, [kfb] twice, repeat from * (18 stitches)
Round 3: k
Round 4: *[k1, kfb] 4 times, k1, repeat from * (26 stitches)
Round 5: k
Round 6: [kfb, k2] 5 times, k1, [kfb, k2] 3 times, k1 (34 stitches)
Round 7: k
Round 8: [k3, kfb] 4 times, k1, [k3, kfb] 3 times, k4, kfb (42 stitches)
Round 9: k
Round 10: *kfb, k2, repeat from * (56 stitches)
Round 11: k
Round 12: k
Round 13: k
Round 14: k
Round 15: k
Round 16: *k2tog, k2, repeat from * (42 stitches)
Round 17: k
Round 18: *[k3, k2tog] 4 times, k1, repeat from * (34 stitches)
Round 19: k
Round 20: *k1, [k2tog, k2] 3 times, k1, k2tog, k1, repeat from * (26 stitches)
Round 21: k
Round 22: *[k2tog, k1] 4 times, k1, repeat from * (18 stitches)
Round 23: *k1, [k2tog] 4 times, repeat from * (10 stitches)
At this point, stuff the toy, flattening it out and stuffing the rim more firmly to get the biconcave shape of a red blood cell. If you are using safety eyes, attach them now.
Round 24: *[k2tog] twice, k1, repeat from * (6 stitches)
Cut yarn and use a darning needle to draw the tail through the remaining stitches. I find that I get neater results if I lightly tug on the stitches on the darning needle to tighten them before drawing the yarn tail through. Use the yarn tails to stitch between the top center and the bottom center to secure the biconcave shape. To weave in the ends, draw the yarn through the length of the toy, bringing the needle out in the center of a stitch. Reinsert the needle through the same place it emerged from and repeat. The yarn tail will be secured in the stuffing.
I hope you enjoy your new red blood cell!
This pattern has not been tested, but I welcome constructive criticism and feedback!
Please don't copy or distribute this pattern or sell items made from this pattern without permission.