The history of the Dandelion, how smoke rings float, and why robots give bad hugs.

Macro Taraxacum portrait against black background — *Taraxacum officinale, April 24th*

“Dandelions are just friendly little weeds who only want to be loved like flowers.”

— Heather Babcock

Robots suck at snuggling. A Rhesus monkey will choose a milk-less cloth surrogate over a lactating wire frame ‘mother’. The implication is that primates like us would rather cuddle and starve than thrive with a cold and rigid companion. Traditionally, robots are precise and strong—ideal for the indoor, disciplined, systematic environment of the production line—but ridiculously dangerous and ineffective in the open world. The mercurial substrate of the organic milieu forever shifts, crumbles, and grows around us, creating a physically unforgiving framework for articulated, motor powered AI bots.

What is needed, or at least desired, is something soft and squeezy like us. Something morphologically adaptable and familiar. And thus it was, that in August, 2016, before the school became famous for grand scale plagiarism, a group at Harvard crafted the world’s first autonomous ‘soft’ robot. Christened the Octobot, this 3-D printed gelatinous ocean inspired droid was compressible and plump; but it could also independently flicker its tentacles, thanks to combustion driven actuators. To be honest, it’s not much to look at. (You can watch it here or below.) But it greased wheels that were excited and ready to apply those tactics evolution had long since matured to the blossoming science of robotics.

From the bosom of this artificial cephalopod sprang forth all manner of new innovations. Scientists began scouring the natural world for inspiration and advice. Soon came the eversion vine bot, the worm bot and the cyborg ray. Then the Stiff-Flop, PoseiDrone, and quite recently, a magnetic SlimeBot. So far, soft robots have achieved motion through actuators—an accessory that converts signal into motion—powered by one or more of several means: dielectric, magnetic, pneumatic, photosensitive, and combustive. But in May of last year, Naomi Nakayama and her team at the Imperial College of London, while observing a dandelion dispersing its seeds, published a new type: a radial actuator powered by humidity.

Wildflower salad — *People insist this is food.*

Taraxacum is a large genus of flowering plants in the family Asteraceae (with sunflowers and daisies), consisting of species generally known as dandelions. The common epithet is derived from the French dent-de-lion, or Lion’s tooth. Other names include blowball, swine snout, doon-head-clock, witch's gowan, milk witch, yellow-gowan, Irish daisy, monks-head, priest's-crown, puff-ball, and my favorite: cankerwort. Because of its diuretic effects, the Brits occasionally call it ‘piss-a-bed’, the Italians ‘pisacan’, and the French ‘pissenlit’. While the genus is native to Eurasia and North America, the two most prevalent species—T. officinale (the common dandelion) and T. erythrospermum (the red-seeded dandelion)—were introduced from Europe into North America on the Mayflower, likely for these aforementioned medicinal properties.

Dandelions, I’m told, make a fairly decent salad. Their greens contain considerable amounts of vitamins A, C, and K and some degree of calcium, potassium, iron, and manganese. The entire plant is considered edible, which really just means it won’t kill you. Dandelions have been gathered for consumption since prehistory and were well known to ancient Egyptians, Chinese, Native Americans, Greeks and Romans. They have been recorded in traditional Chinese medicine for over a thousand years.

*Dandelion pappus: Innovation waiting to happen.*

But what is most fascinating about the humble dandelion, I think, is that billowy globe and the manner by which it proliferates. As every child discovers, the bright yellow astral shaped dandelion flowers devolve into spheroidal puffs of about 100 feathery seed disseminating bristles called pappus, from the Greek word for grandfather due to their beard-like resemblance. Each pappus is in turn topped with about 100 fibrils that form a fan shaped parachute intended to catch wind and loft the seed afar. This parachute is netted and its structure occupies just 10% of the total surface area allowing it to create such incredible drag that a low pressure vortex forms above the feathers. Imagine a wafting ring of smoke and you’ll have some image of how this affects lift. Inspired by these plumes, in 2018 engineers at the University of Washington fashioned a lightweight solar powered ‘sensing device’ that utilizes this pappus-like reticulated mesh to float on the wind and achieve wide area dispersal with an astonishing 95% chance of landing upright.

Perhaps even more extraordinary is the tendency of dandelion seed heads to modify their architecture in varying weather conditions. If observed carefully, one will see these minuscule hairy parachutes clasping up like an inverted umbrella when the air is humid and fanning out when dry. This is because humid air suggests weak wind. Drier air tends to be gustier and the gustier the gust, the wider the seeds can scatter. Many dandelion seeds land within 2 meters of their parent flowers, but in warm, dry, windy conditions, some may fly more than a kilometer. Dr. Nakayama’s team discovered that this closing and opening actuation results from absorption of water molecules along radial tube-like linkages running between the filaments. Higher humidity triggers swelling of the actuators, mechanically folding the hairs upwards and diminishing the risk of seeds surrendering amidst an anemic breeze. This discovery illuminates an alternative resource for making things move artificially, offering new strategies in the ever expanding world of soft robotics. As Dr. Nakayama puts it: “Our work is a great example of what the natural world can teach us about interacting with our environments.”

So next time you pluck a dandelion, just before you puff away at that whimsical ball of fluff, pause to consider what incredible design and innovation you’re holding and what else a flower might have to teach us.