This Camera Captures Piezo Inkjet Micro-Drops For DIY Microfluidics

In microfluidics, there are “drop on demand” instruments to precisely deposit extremely small volumes (pico- or nano-liters) of fluid. These devices are prohibitively expensive, so [Kyle] set out to design a system using hobbyist-level parts for under $1000. As part of this, he has a fascinating use case for a specialized camera: capturing the formation and shape of a micro-drop as it is made.

There are so many different parts to this effort that it’s all worth a read, but the two big design elements come down to:

  1. Making the microdrop using a piezo element
  2. Ensuring the drop is made correctly, and visually troubleshooting
Working prototype. The piezo tube is inside the blue piece at the top. The camera is to the right, and the LED strobe is on the left.

It’s one thing to make an inkjet element in a printer work, but it’s quite another to make a piezoelectric element dispense arbitrary liquids in a controlled, repeatable, and predictable way. Because piezoelectric elements force liquid out with a mechanical motion, different liquids require different drive signals and that kind of experimentation requires a way to see what is going on, hence the need for a drop observation camera.

[Kyle] ended up taking the lens assembly from a cheap USB microscope and mating it to his Korukesu C1 USB Camera with a 3D printed assembly. Another 3D printed enclosure doubles as a lightbox, holding the piezo tube in the center with the LED strobe and camera on opposite sides. The whole assembly had a few false starts, but in the end [Kyle] seems pretty happy with his results. The device is briefly described at a high level here. There are some rough edges, but it’s a working system.

Inkjet technology has been around for a long time (you can see a thirty-plus year old inkjet printer in action here) but it’s worth mentioning that not all inkjet heads are alike. Most inkjet printer heads operate thermally, which means a flash of heat vaporizes some ink to expel a micro-drop. These heads aren’t very suitable for microfluidics because not only do they rely on vaporizing the liquid, but they also don’t work well with anything other than the ink they’re designed for. Piezoelectric print heads are less common, but are more suited to the kind of work [Kyle] is doing.

Can You Print With Highlighter Ink?

With huge swathes of people either out of work or working from home, many are now attempting all manner of exciting or silly projects in their downtime. [Emily Velasco] is no exception. She decided to explore the feasability of printing with highlighter ink.

It’s a messy business. Wear gloves.

The hack starts with a rather ancient inkjet printer, so old that it works with tractor feed paper. [Emily] set about gutting several highlighter pens and squeezed out the ink reservoirs into a ladle. The printer’s ink cartridge was then filled with the fluid, and a test print was fired off. Upon initial extraction, it appears blank. However, with the aid of a UV light, the printed pattern is revealed. It appears that the inkjet is printing a very faint image, such that the system almost works as an “invisible ink”.

It’s a fun little hack with an old printer, made easier as it lacks the DRM of newer models. It’d probably be quite achievable with a dot-matrix, too. If you’re similarly tinkering in the innards of your peripherals, be sure to let us know. Video after the break.

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Vintage Mini Inkjet Prints On-Demand ASCII Art

Readers of a certain age may fondly remember ASCII art emerging from line printers in a long-gone era of computing; for others, it’s just wonderfully retro. Well, when [Emily Velasco] found a vintage Kodak Diconix 150 inkjet at a local thrift store for $4, she knew what she had to do: turn it into a dedicated ASCII-art machine.

Dating to the mid-1980s, the diminutive printer she scored was an early example of consumer inkjet technology; with only 12 “jets,” it sported a resolution roughly equivalent to the dot-matrix impact printers of the day. [Emily] notes that this printer would have cost around $1000 in today’s money — this is from a time before printer companies started selling the printer itself as a loss leader to make revenue on the back end selling consumables. It seems you can’t escape the razor-and-blades model, though: [Emily] had to pay $16 for a new ink cartridge to revive the $4 printer.

With the new ink in place, and some tractor-feed paper acquired, [Emily] started work on the art generator. The concept is something that might have been sold on late-night TV ads: a “cartridge” you plug into your printer to make ASCII masterpieces. Starting with a stripped-down Centronics printer cable that matches the printer’s port, she added an Arduino nano to store and serve up the art. The user interface is foolproof: a single button press causes a random selection from one of ten ASCII images to be printed. The whole thing is ensconced within a slick 3D printed case.

One of the coolest aspects of this project is the lack of power supply. When she first hooked the Arduino to the printer’s parallel port, [Emily] noticed that it powered right up with no external supply, and in true hacker fashion, just ran with it. Upon reflection, it seems that power is being supplied by the printer status lines, Busy and/or Ack, through the input protection diodes of the Atmega328 on the nano.

We really like this project, and are more than a little bummed we tossed those old printers that were kicking around the Hackaday labs for years. If you still have yours, and would like turn out some rad ASCII art, the code for this project is up on GitHub.

We’re no strangers to [Emily]’s work, but if you aren’t familiar with it, check out her inspiring talk from the 2019 Hackaday Superconference. Meanwhile, don’t miss the excellent video about the ASCII art printer cartridge, after the break.

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Printing On Wood, With An Inkjet

As a little experiment in desktop printing, because you can make a desk out of wood, [BlueFlower] modified a standard inkjet printer to print on wood. This is not an electronics mod by any means; this is still a printer that’s plugged into a USB port, does all the fancy printer firmware stuff, tells you to refill the yellow ink cartridge when you only want to print black, and all the other things that inkjet printer firmware will do. This is a mechanical mod. By taking apart the belts and rails and mounting them to a new frame, [BlueFlower] was able to open up the printer so a moving bed holding a board could be moved through the mechanics.

While the printer itself looks a little janky, you can’t argue with results. The prints look good, and should hold up well with a bit of finish. There’s a height adjustment for different thicknesses of stock, and if you’re exceptionally clever, you might be able to put a six-foot-long board through this thing. You can check out a video of this direct to wood printer in action below.

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HP Inkjet Printer Trains For Space

The International Space Station is one of our leading frontiers of science and engineering, but it’s easy to forget that an exotic orbiting laboratory has basic needs shared with every terrestrial workplace. This includes humble office equipment like a printer. (The ink-on-paper kind.) And if you thought your office IT is slow to update their list of approved equipment, consider the standard issue NASA space printer draws from a stock of modified Epson Stylus 800s first flown on a space shuttle almost twenty years ago. HP signed on to provide a replacement, partnering with Simplexity who outlined their work as a case study upgrading HP’s OfficeJet 5740 design into the HP Envy ISS.

Simplexity provided more engineering detail than HP’s less technical page. Core parts of inkjet printing are already well suited for space and required no modification. Their low power consumption is valued when all power comes from solar panels, and ink flow is already controlled via methods independent of gravity. Most of the engineering work focused on paper handling in zero gravity, similar to the work necessary for its Epson predecessor. To verify gravity-independent operation on earth, Simplexity started by mounting their test units upside-down and worked their way up to testing in the cabin of an aircraft in free fall.

CollectSpace has a writeup with details outside Simplexity’s scope, covering why ISS needs a printer plus additional modifications made in the interest of crew safety. Standard injection-molded plastic parts were remade with an even more fire-resistant formulation of plastic. The fax/scanner portion of the device was removed due to concerns around its glass bed. Absorbent mats were attached inside the printer to catch any stray ink droplets.

NASA commissioned a production run for 50 printers, the first of which was delivered by SpaceX last week on board their CRS-14 mission. When it wears out, a future resupply mission will deliver its replacement drawn from this stock of space printers. Maybe a new inkjet printer isn’t as exciting as 3D printing in space or exploring space debris cleanup, but it’s still a part of keeping our orbital laboratory running.

[via Engadget]

 

Repurposing Inkjet Technology For 3D Printing

You would be forgiven for thinking that 3D printing is only about plastic filament and UV-curing resin. In fact, there are dozens of technologies that can be used to create 3D printed parts, ranging from welders mounted to CNC machines to the very careful application of inkjet cartridges. For this year’s Hackaday Prize, [Yvo de Haas] is modifying inkjet technology to create 3D objects. If he gets this working with off-the-shelf parts, this will be one of the most interesting advances for 3D printing in recent memory.

The core of this build is a modification of HP45 inkjet print heads to squirt something other than overpriced ink. To turn this into a 3D printer, [Yvo] is filling these ink cartridges with water or alcohol. This is then printed on a bed of powder, either gypsum, sugar, sand, or ceramic, with each layer printed, then covered with a fine layer of powder. All of this is built around a 3D printer with an X/Y axis gantry, a piston to lower the print volume, and a roller to draw more powder over the print.

The hardest part of this build is controlling the inkjet cartridge itself, but there’s prior work that makes this job easier. [Yvo] is successfully printing on paper with the HP45 cartridges, managing to spit out 150 x 150 pixel images, just by running the cartridge over a piece of paper. Already that’s exceptionally cool, great for graffiti, and something we can’t wait to see in a real, working printer.

You can check out [Yvo]’s handheld printing efforts below.

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Eating A QR Code May Save Your Life Someday

QR codes are easy to produce, resistant to damage, and can hold a considerable amount of data. But generally speaking, eating them has no practical purpose. Unfortunately the human digestive tract lacks the ability to interpret barcodes, 2D or otherwise. But thanks to the University of Copenhagen, that may soon change.

A new paper featured in the International Journal of Pharmaceutics details research being done to print QR codes with ink that contains medicine. The mixture of medicines in the ink can be tailored to each individual patient, and the QR code itself can contain information about who the drugs were mixed for. With a standard QR reader application on their smartphone, nurses and care givers can scan the medicine itself and know they are giving it to the right person; cutting down the risk of giving patients the wrong medication.

The process involves using a specialized inkjet printer to deposit the medicine-infused ink on a white edible substrate. In testing, the substrate held up to rough handling and harsh conditions while still keeping the QR code legible; an important test if this technology is to make the leap from research laboratory to real-world hospitals.

In the future the researchers hope the edible substrate can be produced and sent to medical centers, and that the medicinal ink itself will be printable on standard inkjet printers. If different medicines were loaded into the printer as different colors, it should even be possible to mix customized drug “cocktails” through software. Like many research projects it seems likely the real-world application of the technology won’t be as easy as the researchers hope, but it’s a fascinating take on the traditional method of dispersing medication.

QR codes have long been a favorite of the hacker community. From recovering data from partial codes to using them to tunnel TCP/IP, we’ve seen our fair share of QR hacks over the years.

[Thanks to Qes for the tip]

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