A new prosthetic hand
It gives users the sensation of touch, and is cheaper than alternatives, too
Prosthetic limbs have been around for a long time. The oldest known, a piece of wood carved and painted to replace the lost toe of an Egyptian noblewoman, dates back more than 3,000 years. But prosthetics which behave like the real thing as well as looking like it are still very much a work in progress. And a group at Shanghai Jiao Tong University, in China, have just come up with what looks to be a significant advance—an affordable prosthetic hand that not only responds like a real one to signals from the wearer’s brain, but is also able to signal back to the brain what it is touching and doing.
Gu Guoying and his colleagues describe their invention in Nature Biomedical Engineering. Its fingers are made of rigid tubes connected by soft joints. These are similarly connected to a 3dprinted plastic palm. The whole is covered with a flexible elastomer layer to mimic skin and is attached to the user’s residual limb via a customised plastic socket. In contrast to current models, which are electrically powered, Dr Gu’s hand is powered pneumatically by a pump held in a waist bag, with the connecting air lines running under the user’s clothes alongside communication cables. This reduces its weight below 300 grams—half that of some current models, and less, indeed, than the weight of a real hand—though the waist bag adds a further 444 grams.
The hand uses similar signalprocessing algorithms to other prosthetics on the market. The big advance is that it
does not require invasive surgery or electronic implants into the residual limb to communicate with the user’s brain. Sensors on the skin record electrical activity from the remaining arm muscles. In an intact arm, this activity would tell those muscles how to operate the hand. Instead, they are interpreted by patternrecognition software that sends appropriate commands to the pump to move the artificial hand in the same way. Meanwhile, other signals travel in the opposite direction from sensors in the hand’s fingertips to nerves in the arm, whence they are relayed to the brain and provide a sensation of touch. The upshot is something which responds like a hand and feels like one to the user.
Dr Gu and his colleagues compared the efficacy of their invention with that of existing models using tests borrowed from research into strokes and spinalcord injuries. These included writing, grasping and lifting objects, lifting food to the mouth, and stacking draughtsmen. Normally, they found, it worked better—particularly for delicate tasks like handling fragile objects, petting a cat and shaking hands.
The other advantage of Dr Gu’s invention is that it is cheap. The components it is made from cost about $500. Existing models may sell for $10,000 or more. If it, or something similar, goes into production, that will permit the transformation of many more of the lives of the 5m people who have lost a hand, or were born without one, than is possible at the moment.
Off a busy street in Florence stands the church of San Remigio. The chapel nearest the left of the altar was patronised by the Gaddi family, one of whose most illustrious sons, Niccolò Gaddi, commissioned its 16th-century altarpiece. In his will, he specified that it should depict a scene from Dante Alighieri’s “Paradiso”, the final part of his monumental poem, known in English as the “Divine Comedy”.
Gaddi’s stipulation was a gesture of appreciation to the poet’s family, the Alighieri, who previously sponsored the chapel. Even so, as David Ekserdjian remarks in a recently published study, “The Italian Renaissance Altarpiece”, it was an extraordinary choice. Here was a Florentine grandee, a man whose entire life was entwined with the Catholic church, treating a work of fiction—and one scathingly derogatory of Catholic clerics—as a religious authority “almost on a par with the Bible and the lives of the saints”.
The painting in the chapel, by Jacopo da Empoli, exemplifies Dante’s exceptional status. For Italians, he is the sommo poeta: the supreme poet, unsurpassed in the 700 years since his death in 1321, the anniversary of which falls next month. Though Dante wrote several other works, including treatises on politics and language, the “Divine Comedy”, a chronicle of his imaginary journey through hell and purgatory to heaven, is his masterpiece. There is scarcely an Italian who cannot recite its opening lines, in which he describes being in the middle of his life, finding himself in a dark wood and losing his way:
For non-Italians, too, Dante belongs in a pantheon of the West’s paramount literary geniuses, alongside Homer, Cervantes and Shakespeare. In the English-speaking world, his influence can be discerned in the work of Chaucer, Milton, Shelley and T.S. Eliot, among many others. The terza rima, the interlocking rhyme scheme that Dante first set down in writing, and which propels readers through the “Divine Comedy”, has been used by poets ever since.
And yet Jacopo da Empoli’s altarpiece was painted in a city that exiled Dante, confiscated his possessions and sentenced him to death on trumped-up charges. For Lino Pertile of Harvard University, that points to a paradox: “We celebrate Dante. But we don’t listen to him. Why has Florence never revoked the capital sentence it decreed in 1315? Because what Dante was preaching and what the Florentines were doing were utterly at odds.”
It is often argued that the sommo poeta was ahead of his time. Dante unquestionably gave Italians the basis for a common language more than 500 years before they were united politically (though it is doubtful that he would have approved of unification: he lived before the age of nationstates and aspired to a universal monarchy). Dante also prefigured ideas characteristic of the Renaissance and the Reformation. He imagined a pagan author, Virgil, as his guide to hell, which he peopled with monsters from classical mythology. And he consigned to the underworld “clergymen, and popes and cardinals within whom avarice works its excess”.
But in no sense was Dante, who was born in or around 1265, a liberal—even by the standards of his time. He was appalled by the property boom that had transformed Florence in the 13th century and the rampant materialism it unleashed. One of the city’s proudest achievements was, and still is, to have made its gold coin, the fiorino, widely accepted in Europe seven centuries before the euro. In a play on words, Dante damned it as il maladetto fiore
(the accursed flower). The little that is known of his personality suggests that, at least while he remained in Florence, he
Nel mezzo del cammin di nostra vita mi ritrovai per una selva oscura, ché la diritta via era smarrita.
was a rather grouchy moralist.
What Dante offers in the “Divine Comedy” is a journey beyond politics, “from the life of the senses to a life of the spirit”, as Mr Pertile puts it. That may renew his appeal in a bruised world that in short order has endured a financial crisis, a recession and a pandemic, and now faces the cataclysm of global warming.
Joseph Luzzi of Bard College calls Dante a “poet of crisis”, whose life split in two when he was expelled from Florence. Mr Luzzi himself endured a similar fate, in even more dramatic fashion. At 9.15am on November 29th 2007 Mr Luzzi’s wife, Katherine Mester, eight and a half months pregnant with their first child, pulled out of a petrol station in upstate New York and into the path of an oncoming van. Fortyfive minutes after doctors performed an emergency caesarean section to deliver Isabel, her daughter, Mester died. By noon Mr Luzzi was a father—and a widower.
Beyond mortal flesh
A book he published in 2015, “In a Dark Wood”, recounts how he began to see his own distraught bereavement reflected in the writings of his favourite poet. “I heard Dante’s own voice as never before,” he says. The poet “lost everything. And the sense he conveys of losing a life that you once had was visceral in me.” Mr Luzzi too felt he was wandering through hell, and only after years of despair and confusion reached a kind of purgatory. But then his path crossed that of Bard’s artistinresidence, Helena Baillie, an English violinist, and “the stars aligned”. They married and today have four children, including Isabel.
Most readers never proceed beyond the macabre thrills of Dante’s “Inferno”, with its grotesquely inventive torments. The gluttons get off comparatively lightly: they merely lie for ever under icy rain while the threeheaded monster Cerberus claws at their flesh and they “howl like dogs”. Warmongers flounder in boiling blood while flatterers wallow in excrement. The archbishop of Pisa, Ruggieri degli Ubaldini, is encased with the enemy he had starved to death, Count Ugolino, who gnaws at his neck for eternity.
Those who do ascend from the “Inferno” find some of Dante’s most lyrical verse in his “Purgatorio”. One of the most quoted passages is the greeting he receives from his friend, Casella, in the second section, or canto: “As once I loved you in my mortal flesh, without it now I love you still.”
But it is the leastread of the three books, “Paradiso”, that makes sense of the other two. It shows, says Mr Luzzi, that its author was not just a poet of crisis, but also a poet of hope: “The ‘Divine Comedy’ is that rarest thing, an epic poem with a hopeful ending. It is about getting a second chance—and ultimately finding joy.” n