It’s a really tough problem that has been solved to an amazing level. How do you capture and contain urine from a floppy, curved, and moving human infant? Ah, but the problem is a bit harder than that. You also want to keep that liquid away from the soft skin of the newborn and keep the exterior of your overall system dry too. From an R&D point of view the nice thing is that the customer base is huge — everyone needs some type of diapers. And what we have achieved thus far is a huge accomplishment of material science. [Bill Hammack], The Engineer Guy, takes on the engineering of baby diapers in his latest video.
A diaper uses three inner layers to sweep urine away from baby’s skin. The first layer actually repels water — being injected between skin and this layer, liquid passes through the holes in the material. But the moisture repellent property prevents it from moving in the opposite direction because of the next two layers encountered. The second layer uses capillary action to pull the moisture toward the third (and to act as a one-way moisture valve). The third layer contains a super-absorbent polymer. That layer starts off very thin and swells with absorption.
Bill explores just a bit about how these materials are actually manufactured. The layers are non-woven to form the necessary structures. The absorption layer uses cotton fibers to ensure moisture doesn’t form a dam between polymers. Whether you have a little one in your own household or not, the science behind this solved problem is fascinating and well worth the six minutes you’ll spend on the video below.
Continue reading “Disposable Diapers Are A Tribute To Material Science”
Electrospinning is a fascinating process where a high voltage potential is applied between a conductive emitter nozzle and a collector screen. A polymer solution is then slowly dispensed from the nozzle. The repulsion of negative charges in the solution forces fine fibers emanate from the liquid. Those fibers are then rapidly accelerated towards the collector screen by the electric field while being stretched and thinned down to a few hundred nanometers in diameter. The large surface area of the fine fibers lets them dry during their flight towards the collector screen, where they build up to a fine, fabric-like material. We’ve noticed that electrospinning is hoped to enable fully automated manufacturing of wearable textiles in the future.
[Douglas Miller] already has experience cooking up small batches of microscopic fibers. He’s already made carbon nanotubes in his microwave. The next step is turning those nanotubes into materials and fabrics in a low-cost, open source electrospinning machine, his entry for the Hackaday Prize.
Continue reading “Hackaday Prize Entry: Open Source Electrospinning Machine”
It’s not transparent aluminum, exactly, but it might be even better: transparent wood. Scientists at the University of Maryland have devised a way to remove all of its coloring, leaving behind an essentially clear piece of wood.
By boiling the block of wood in a NaOH and Na2SO chemical bath for a few hours the wood loses its lignin, which is gives wood its color. The major caveat here is that the lignin also gives wood strength; the colorless cellulose structure that remains is itself very fragile. The solution is to impregnate the transparent wood with an epoxy using about three vacuum cycles, which results in a composite that is stronger than the original wood.
There are some really interesting applications for this material. It does exhibit some haze so it is not as optimally transparent as glass but in cases where light and not vision is the goal — like architectural glass block — this is a winner. Anything traditionally build out of wood for its mechanical properties will be able to add an alpha color channel to the available options.
The next step is finding a way to scale up the process. At this point the process has only been successful on samples up to 1 centimeter thick. If you’re looking to build a starship out of this stuff in the meantime, your best bet is still transparent aluminum. We do still wonder if there’s a way to eliminate the need for epoxy, too.
A research group at the University of Rochester has developed a new polymer with some amazing traits. It can be stretched or manipulated into new shapes, and it will hold that shape until heat is applied. Shape-shifting polymers like this already exist, but this one is special: it can go back to its original shape when triggered by the heat of a human body. Oh, and it can also lift objects up to 1000 times its mass.
The group’s leader, chemical engineering professor [Mitch Anthamatten], is excited by the possibilities of this creation. When the material is stretched, strain is induced which deforms the chains and triggers crystallization. This crystallization is what makes it retain the new shape. Once heat is applied, the crystals are broken and the polymer returns to its original shape. These properties imply several biomedical applications like sutures and artificial skin. It could also be used for tailored-fit clothing or wearable technology.
The shape-shifting process creates elastic energy in the polymer, which means that it can do work while it springs back to normal. Careful application of molecular linkers made it possible for the group to dial in the so-called melting point at which the crystallization begins to break down. [Anthamatten] explains the special attributes of the material in one of the videos after the break. Another video shows examples of some of the work-related applications for the polymer—a stretched out strand can pull a toy truck up an incline or crush a dried seed pod.
Continue reading “New Shape-Shifting Polymer Works Hard, Plays Hard”
From the horse’s mouth,
“In this lithography experiment light creates free radicals from phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide which induce polymerization of 1,6-hexanediol diacrylate.”
Or for those without a Chemical Engineering degree, light from a (high resolution) projector interacts with a special liquid, producing a hard polymer on the surface. A platform within the liquid is lowered, taking the layer of polymer with it. Shine the projector again to produce another layer: lather, rinse, repeat. Long story short, an atypical 3D printer using light on a very small scale.
You get the chemicals and lab equipment, we’ll get the laptop and projector, and for goodness sake [Jimmie] stop bumping the table.