As a project gets more complicated, some kind of internal communication network is often used to that all of the various modules and sensors can talk with each other. For hardware hackers like us, that usually means SPI, I2C, or maybe even good old fashioned UART. But if you’re pushing a lot of data around, like live video feeds from multiple cameras, you’ll need something a bit faster than that.
Which is why [Josh Elijah] has created the SwitchBlox Nano, a three port 10/100 Ethernet switch that fits on a one inch square PCB. All you need to do is provide it with power, with a generous input range of 5 to 50 volts, connect your devices to the Molex Picoblade connectors on the board, and away you go. There’s even a 5 V 1 A regulated output you can use to run your downstream devices.
If you’ve got a feeling that you’ve seen something very similar on these pages earlier in the year, you’re not imagining things. Back in April we covered the original five port SwitchBlox in a post that garnered quite a bit of attention. In fact, [Josh] tells us that the design of this new switch was driven largely by the feedback he got from Hackaday readers. The Nano is not only smaller and cheaper than the original, but now maintains full electrical isolation between each port.
The average Hackaday reader is as knowledgeable as they are opinionated, and we’re glad [Josh] was able to put the feedback he received to practical use. We’re proud that our community has had a hand in refining successful commercial products like the Arduboy handheld game system and the Mooltipass hardware password keeper. Now it looks like we can add a tiny Ethernet switch to the list of gadgets we’ve helped push up the hill. Maybe we should get a stamp or something…
Like most of us, [Hunter] and his partner [Katyrose] have been in quarantine for the past few months. Unlike most of us, they spun a 3D printed chicken playground design hackathon out of their self-isolation. The idea is simple: to build a playground full of toys custom-tailored to appease each chicken’s distinctive taste. The execution, however, can be proven a little tricky given that chickens are very unpredictable.
For each of the four select chickens in their coop, the couple designed separate toys based on their perceived interests. One, showing a fondness for worms, inspired the construction of a tree adorned with rice noodles in place of the living article, and moss to top it off. For late-night entertainment, the tree is printed in glow-in-the-dark filament. The others were presented with a print-in-place rotating mirror disguised as a flower, and a pecking post covered in peanut butter and corn. As a finishing piece, the fourth toy is designed as a jungle gym post with a reward of bread at the top for the chicken who dares climb it. Since none of the chickens seemed interested in it, they were eventually hand-fed the bread.
With no other entries to their hackathon, [Hunter] declared themselves as the winners. The 3D files for their designs are available for their patrons to print, should they have their own chicken coops they want to adorn. While the hackathon might’ve been a success for them, their chickens in particular seemed unimpressed with their new toys, only going to show that the only difference between science and messing around is writing it down, or in this case, filming the process. If you’re looking for other ways to integrate your chickens into the maker world, check out this Twitch-enabled chicken feeder, or this home automation IoT chicken coop door. Meanwhile, check out the video about their findings after the break.
It’s not a balloon, however shiny its exterior may seem. This miniature indoor robotic airship created by the University of Auckland mechanical engineering research group [New Dexterity] is an asymmetric system experimenting with the possibilities of an open-source helium-based airship.
Why a helium airship, as opposed to a fixed wing aircraft? The group wanted to experiment with the advantages of lighter-than-air (LTA) travel, namely the higher mobility and looser path planning constraints. Furthermore, LTA airships have a less obstructed field of vision and fewer locomotion issues. While unmanned aerial vehicles (UAV) may be capable of hovering in one place, their lift is generated by rotor thrust, which drains their batteries quickly in the order of minutes. LTA airships can hover for longer periods of time.
The design was created for educational and research purposes, focusing on the financial feasibility of manufacturing the platform, the environmental impact of the materials, and the helium loss through the balloon-like envelope. By measuring these parameters, the researchers are able to study the effects of circumstances such as the cost of indoor commercial balloons and the mechanical properties of balloon materials.
The airship gondola was designed and 3D printed in a modular fashion, then attached to the envelope with Velcro. The placement with respect to the horizontal symmetry of the gondola was done for flight stability, with several configurations tested for the side rotor angle.
The group open-sourced their CAD files and ROS interface for controlling the airship. They primarily use off-the-shelf components such as Raspberry Pi boards, propellers, a DC single brushed motor driver carrier, and LiPo batteries for a total cost of $90 for the platform, with an addition $20 for the balloon and initial helium filling. The price is comparable to the cost of indoor blimps like the Blimpduino 2.0.
You can check out the completed airship below, where the team demonstrates its path following capabilities based on a carrot chasing path finding algorithm.
It’s not a balloon, however shiny its exterior may seem. This miniature indoor robotic airship created by the University of Auckland mechanical engineering research group [New Dexterity] is an asymmetric system experimenting with the possibilities of an open-source helium-based airship.
Why a helium airship, as opposed to a fixed wing aircraft? The group wanted to experiment with the advantages of lighter-than-air (LTA) travel, namely the higher mobility and looser path planning constraints. Furthermore, LTA airships have a less obstructed field of vision and fewer locomotion issues. While unmanned aerial vehicles (UAV) may be capable of hovering in one place, their lift is generated by rotor thrust, which drains their batteries quickly in the order of minutes. LTA airships can hover for longer periods of time.
The design was created for educational and research purposes, focusing on the financial feasibility of manufacturing the platform, the environmental impact of the materials, and the helium loss through the balloon-like envelope. By measuring these parameters, the researchers are able to study the effects of circumstances such as the cost of indoor commercial balloons and the mechanical properties of balloon materials.
The airship gondola was designed and 3D printed in a modular fashion, then attached to the envelope with Velcro. The placement with respect to the horizontal symmetry of the gondola was done for flight stability, with several configurations tested for the side rotor angle.
The group open-sourced their CAD files and ROS interface for controlling the airship. They primarily use off-the-shelf components such as Raspberry Pi boards, propellers, a DC single brushed motor driver carrier, and LiPo batteries for a total cost of $90 for the platform, with an addition $20 for the balloon and initial helium filling. The price is comparable to the cost of indoor blimps like the Blimpduino 2.0.
You can check out the completed airship below, where the team demonstrates its path following capabilities based on a carrot chasing path finding algorithm.
It’s not a balloon, however shiny its exterior may seem. This miniature indoor robotic airship created by the University of Auckland mechanical engineering research group [New Dexterity] is an asymmetric system experimenting with the possibilities of an open-source helium-based airship.
Why a helium airship, as opposed to a fixed wing aircraft? The group wanted to experiment with the advantages of lighter-than-air (LTA) travel, namely the higher mobility and looser path planning constraints. Furthermore, LTA airships have a less obstructed field of vision and fewer locomotion issues. While unmanned aerial vehicles (UAV) may be capable of hovering in one place, their lift is generated by rotor thrust, which drains their batteries quickly in the order of minutes. LTA airships can hover for longer periods of time.
The design was created for educational and research purposes, focusing on the financial feasibility of manufacturing the platform, the environmental impact of the materials, and the helium loss through the balloon-like envelope. By measuring these parameters, the researchers are able to study the effects of circumstances such as the cost of indoor commercial balloons and the mechanical properties of balloon materials.
The airship gondola was designed and 3D printed in a modular fashion, then attached to the envelope with Velcro. The placement with respect to the horizontal symmetry of the gondola was done for flight stability, with several configurations tested for the side rotor angle.
The group open-sourced their CAD files and ROS interface for controlling the airship. They primarily use off-the-shelf components such as Raspberry Pi boards, propellers, a DC single brushed motor driver carrier, and LiPo batteries for a total cost of $90 for the platform, with an addition $20 for the balloon and initial helium filling. The price is comparable to the cost of indoor blimps like the Blimpduino 2.0.
You can check out the completed airship below, where the team demonstrates its path following capabilities based on a carrot chasing path finding algorithm.
Stress monitoring has always been a tricky business. As it turns out, there is a somewhat reliable way of monitoring stress by measuring how much cortisol, the so-called “stress hormone,” the human body produces. With that in mind, bioengineering researchers at the University of Texas at Dallas decided to make CortiWatch, a wearable device for continuously monitoring cortisol excreted in sweat, as a sort of DIY stress meter.
They made their own potentiostat, a device for measure small amounts of current produced by electrochemical reactions, similar to the glucometer. We’ve talked about these types of measurements before. Simply put, the potentiostat contains a voltage reference generator which biases the sensing electrodes at a preset potential. The voltage bias causes local electrochemical reactions at the sensing electrodes (WE in the image above), stimulating electron flow which is then measured by a transimpedance amplifier or “current-to-voltage” converter. The signal is then analyzed by an onboard analog-to-digital converter. Simply put, the more cortisol in the system, the higher the transimpedance amplifier voltage.
To validate their system a bit more thoroughly than simple benchtop studies, the researchers did some “real-life” testing. A volunteer wore the CortiWatch for 9 hours. The researchers found a consistent decrease in cortisol levels throughout the day and were able to verify these measurements with another independent test. Seems reasonable, however, it’s not quite clear to us what cortisol levels they were expecting to measure during the testing period. We do admit that it takes quite a bit of calibration to get these systems working in real-life settings, so maybe this is a start. We’ll see where they go from here.
Stress monitoring has always been a tricky business. As it turns out, there is a somewhat reliable way of monitoring stress by measuring how much cortisol, the so-called “stress hormone,” the human body produces. With that in mind, bioengineering researchers at the University of Texas at Dallas decided to make CortiWatch, a wearable device for continuously monitoring cortisol excreted in sweat, as a sort of DIY stress meter.
They made their own potentiostat, a device for measure small amounts of current produced by electrochemical reactions, similar to the glucometer. We’ve talked about these types of measurements before. Simply put, the potentiostat contains a voltage reference generator which biases the sensing electrodes at a preset potential. The voltage bias causes local electrochemical reactions at the sensing electrodes (WE in the image above), stimulating electron flow which is then measured by a transimpedance amplifier or “current-to-voltage” converter. The signal is then analyzed by an onboard analog-to-digital converter. Simply put, the more cortisol in the system, the higher the transimpedance amplifier voltage.
To validate their system a bit more thoroughly than simple benchtop studies, the researchers did some “real-life” testing. A volunteer wore the CortiWatch for 9 hours. The researchers found a consistent decrease in cortisol levels throughout the day and were able to verify these measurements with another independent test. Seems reasonable, however, it’s not quite clear to us what cortisol levels they were expecting to measure during the testing period. We do admit that it takes quite a bit of calibration to get these systems working in real-life settings, so maybe this is a start. We’ll see where they go from here.
Stress monitoring has always been a tricky business. As it turns out, there is a somewhat reliable way of monitoring stress by measuring how much cortisol, the so-called “stress hormone,” the human body produces. With that in mind, bioengineering researchers at the University of Texas at Dallas decided to make CortiWatch, a wearable device for continuously monitoring cortisol excreted in sweat, as a sort of DIY stress meter.
They made their own potentiostat, a device for measure small amounts of current produced by electrochemical reactions, similar to the glucometer. We’ve talked about these types of measurements before. Simply put, the potentiostat contains a voltage reference generator which biases the sensing electrodes at a preset potential. The voltage bias causes local electrochemical reactions at the sensing electrodes (WE in the image above), stimulating electron flow which is then measured by a transimpedance amplifier or “current-to-voltage” converter. The signal is then analyzed by an onboard analog-to-digital converter. Simply put, the more cortisol in the system, the higher the transimpedance amplifier voltage.
To validate their system a bit more thoroughly than simple benchtop studies, the researchers did some “real-life” testing. A volunteer wore the CortiWatch for 9 hours. The researchers found a consistent decrease in cortisol levels throughout the day and were able to verify these measurements with another independent test. Seems reasonable, however, it’s not quite clear to us what cortisol levels they were expecting to measure during the testing period. We do admit that it takes quite a bit of calibration to get these systems working in real-life settings, so maybe this is a start. We’ll see where they go from here.
If you are dealing with solar or battery power, you might want to have one of these little energy meters built by [Open Green Energy] around. The Arduino-based instrument measures DC voltage, current, power, energy, capacity, and temperature. The range is only up to 26 volts and 3.2 amps, but you could extend that with some external circuitry.
Of course, measuring a voltage with the Arduino is old hat. But the addition of a INA219 current sensor provides voltage, current, and power measurements in a single module that talks I2C back to the host computer.
The layout is neat although he’s working on a PCB, as well. This basic circuit would work well for a data logger or current monitor with just a few software changes.
If you are into this sort of thing, the INA219 actually comes in two versions. The “A” version is not as precise as the “B” version. The difference, though, is small. According to the data sheet, the “A” version can be off as much as 1% on current measurement across the entire temperature range, while the “B” variant holds to 0.5%. Both devices are typically around 0.2% under normal operating conditions.
The device works with an external shunt resistor, so it measures the supply voltage on one side of the shunt and by observing the difference in voltage on the other side, it can calculate the amount of current.
If you want to see what an $8,000 instrument can do for current measurement, have a look at the Keithley 2460 SourceMeter. If your budget is somewhat less, there’s the Joulescope.
Ever since the high-quality camera for the Raspberry Pi was released a few months back it has been the center of attention for many hacks. In this quick build [Martin Mander] shows us how to make a servo-powered focusing mechanism entirely from LEGO.
The inspiration for this project came to him while he was working on his 1979 Merlin Pi Camera and found that setting the focus just right is vital in order to get good quality pictures. So he set himself the goal to build a mechanism that allows him to focus the camera precisely and remotely.
It is the plethora of LEGO-compatible parts that are available off-the-shelf that make such a project possible without the use of any 3D printed components. He not only found a LEGO-compatible continuous rotating servo but also a LEGO-compatible case for the Pi, and a LEGO cogwheel which almost fits exactly onto the camera lens. He also added a tripod mount to the case that allows him to set up the camera anywhere. The camera and focussing mechanism are controlled with a custom GUI based on guizero Python 3 library and the camera can be accessed remotely via VNCViewer.
It’s taken 54 years, but soon, you’ll finally be able to buy a fully-functional version of the tricorder from Star Trek. Announced on the official website for the legendary sci-fi franchise, the replica will be built by The Wand Company, who’ve previously produced a number of high-quality official Star Trek props as well as replicas for Doctor Who and the Fallout game series.
Admittedly, we’re not sure what a “fully-functional tricorder” actually is, mainly because the various on-screen functions of the device were largely driven by whatever bind Kirk and Spock managed to find themselves in that week. But the announcement mentions the ability to scan radio frequencies, pull in dynamic data from environmental sensors, and record audio. The teaser video after the break doesn’t give us any more concrete information than the announcement, but it does seem to confirm that we’ll be viewing said data on the device’s iconic flip-up display.
Now as the regular Hackaday reader knows, fans have been building extremely impressive “functional” tricorders for some time now. Unlike the sleek 24th century versions seen in Star Trek: The Next Generation, the original tricorder prop was rather clunky and offers plenty of internal volume for modern goodies. Cramming a Raspberry Pi, LCD, and a bunch of sensors into an inert replica is a relatively approachable project. So it will be interesting to see how the official version stacks up to what’s already been done by intrepid hackers and makers.
The official tricorder won’t be available until summer of 2021, but you can sign up to be notified when it’s your turn to beam one up. While the $250 USD sticker price might keep the more casual Trekkers at bay, it’s actually a bit cheaper than we would have assumed given the amount of time and money we’ve seen fans put into their own builds.
If you were to travel back in time to the turn of the previous century and try to convince the average person that the grains of sand on just about any beach would be the basis of an industry worth hundreds of billions of dollars within 100 years, they’d probably have thought you were crazy. Aside from being coarse, rough, and irritating, sand is everywhere, and convincing anyone of its value would be a hard sell, unless your interlocutor was a real estate visionary with an appreciation of the future value of seaside property and a lot of patience.
Fast forward to our time, and we all know the value of the material that comes from common quartz sand: silicon, specifically the ultra-purified crystals of silicon that end up as the wafers we depend on to build the circuitry of life. The trip from beach to chip foundry is a long and non-obvious one which would not have been possible without the insights of an undistinguished Polish student and one-time druggist who discovered the process that made the Information Age possible: Jan Czochralski.
Those Who Can’t Teach
Born in 1885 in what is now Kcynia, Poland but was then part of the Prussian Empire, Jan Czochralski showed an early aptitude for chemistry. As always seems the case with chemistry prodigies, an early experiment in his home laboratory resulted in an explosion. His father, a carpenter, had aspirations that Jan would one day become a teacher, but despite his love of chemistry, or perhaps because of it, Jan’s grades were poor enough to preclude him from that career path. As an alternative, he left home and took a job in a drug shop, vowing only to return to his hometown once he had become rich and famous.
Jan Czochralski, circa 1910
Jan continued his studies on his own and progressed through a series of jobs in Germany’s burgeoning chemistry industry. He was largely self-trained when he applied to and was accepted by the Technische Hochschule in Berlin Charlottenburg, where he would specialize in metallurgy. Soon thereafter, as a newly minted chemical engineer at the Germany electrical giant AEG, he began studies into the applications in electronics of what was then an exotic and expensive material: aluminum.
Czochralski’s career was advancing rapidly on the value of his metallurgical research and the degree to which he published his findings. His work was cited frequently, so much so that he would one day become one of the most referenced Polish scientists, no mean feat when the list includes names like Marie Skłodowska Curie and Stanisław Ulam. His fame was eventually such that Henry Ford would court him aggressively and offer to put him in charge of his entire factory in 1923. Czochralski politely declined.
Absent-Minded Professor?
For someone who was so driven and devoted to the field of chemical metallurgy, and for as methodical as Czochralski reportedly was, it’s ironic that what he is perhaps best known for, and the discovery that would certainly become his most important legacy, was the result of an accident. In 1916, as the story goes, Czochralski was making some notes on a metallurgical experiment at his bench. Intent on his notebook pages, he didn’t notice that instead of dipping his pen into the inkwell, he had dipped it into a crucible of molten tin. The story may be apocryphal, given that the melting point of tin is 232 °C and it would be unlikely that a careful experimenter like Czochralski would be so cavalier with a pot of molten metal, but however the pen got into the tin, the result was interesting.
When he withdrew the pen, a fine whisker of tin was drawn up with it from the pool of molten metal. Curious as to the nature of the thread, Czochralski analyzed it and was surprised to find that it was a single crystal. He continued to experiment with the technique, replacing the pen nib with various capillary tubes, and adding seed crystals to provide nucleation sites for crystal formation. He was soon able to produce single crystals of various metals up to 1 mm in diameter and as long as a meter and a half. In addition to tin, he used his method to produce crystal filaments of lead and zinc.
Czochralski duly reported his findings in 1917, and though there was an initial burst of experimentation by others into the “Czochralski method”, the distractions of back-to-back world wars left the work largely in obscurity. He continued working in the chemical industry for the rest of his life, and would live long enough to see researchers at Bell Labs — it’s always Bell Labs — rediscover his process in the late 1940s and apply it to materials he never imagined working with, like silicon and germanium, as they began to invent the semiconductor industry.
The details of the Czochralski process for producing the single enormous silicon crystals, or boules, that are the raw material of almost every semiconductor product made today varies from the original method only in minor details, and of course in the scale of production. Silicon boule production is carried out in an induction furnace that has precise temperature control and can be provided with an inert atmosphere such as argon. The process starts when a quartz crucible is charged with ultrapure (99.9999%, or one non-silicon molecule in a million) polycrystalline silicon. The furnace is heated to about 1,500 °C while the crucible slowly rotates.
When the polysilicon has melted, a puller rod is lowered into the molten silicon pool. The end of the puller rod carries a seed crystal of silicon in a precise orientation, to serve as a nucleation site for crystallization. The puller rod, which is rotating in the opposite direction from the crucible, remains in the molten silicon for a short time before slowly being withdrawn. The molten silicon has by this point started to crystallize, and the puller rod begins accumulating a cone of crystalline silicon in the same orientation as the seed crystal.
Eventually the growing crystal reaches its maximum diameter, and the boule becomes more cylindrical. The diameter of the boule can reach up to 300 mm routinely, although 450 mm diameter processes are currently being prototyped; a theoretical maximum of 675 mm is possible but has not been attained. The boule continues to grow as it is withdrawn, a single crystal of silicon dangling from the puller rod and eventually weighing several hundred kilograms. The video above gives a good overview of the entire process, from production of polycrystalline silicon from quartzite sand through boule formation, and on to the fascinating details of processing the boule into wafers.
The Czochralski process is not only used for silicon crystals. Synthetic gemstones, including ruby, sapphire, garnet, and spinel can be grown using the method. On the other hand, the method is far from the only way of making ingots of monocrystalline silicon.
The float-zone process, also developed at Bell Labs, uses RF energy to heat a zone within a rod of polycrystalline silicon. It can produce silicon of much higher purity since the melt isn’t exposed to oxygen by the quartz crucible of the Czochralski method. There’s also the Bridgman–Stockbarger method, which is basically an upside-down version of the Czochralski method.
At the end of the day, though, Jan Czochralski’s accidental discovery of a crystal-growing technique has stood the test of time, as something like 90% of silicon wafers are cut from boules grown using his method.
If you were to travel back in time to the turn of the previous century and try to convince the average person that the grains of sand on just about any beach would be the basis of an industry worth hundreds of billions of dollars within 100 years, they’d probably have thought you were crazy. Aside from being coarse, rough, and irritating, sand is everywhere, and convincing anyone of its value would be a hard sell, unless your interlocutor was a real estate visionary with an appreciation of the future value of seaside property and a lot of patience.
Fast forward to our time, and we all know the value of the material that comes from common quartz sand: silicon, specifically the ultra-purified crystals of silicon that end up as the wafers we depend on to build the circuitry of life. The trip from beach to chip foundry is a long and non-obvious one which would not have been possible without the insights of an undistinguished Polish student and one-time druggist who discovered the process that made the Information Age possible: Jan Czochralski.
Those Who Can’t Teach
Born in 1885 in what is now Kcynia, Poland but was then part of the Prussian Empire, Jan Czochralski showed an early aptitude for chemistry. As always seems the case with chemistry prodigies, an early experiment in his home laboratory resulted in an explosion. His father, a carpenter, had aspirations that Jan would one day become a teacher, but despite his love of chemistry, or perhaps because of it, Jan’s grades were poor enough to preclude him from that career path. As an alternative, he left home and took a job in a drug shop, vowing only to return to his hometown once he had become rich and famous.
Jan Czochralski, circa 1910
Jan continued his studies on his own and progressed through a series of jobs in Germany’s burgeoning chemistry industry. He was largely self-trained when he applied to and was accepted by the Technische Hochschule in Berlin Charlottenburg, where he would specialize in metallurgy. Soon thereafter, as a newly minted chemical engineer at the Germany electrical giant AEG, he began studies into the applications in electronics of what was then an exotic and expensive material: aluminum.
Czochralski’s career was advancing rapidly on the value of his metallurgical research and the degree to which he published his findings. His work was cited frequently, so much so that he would one day become one of the most referenced Polish scientists, no mean feat when the list includes names like Marie Skłodowska Curie and Stanisław Ulam. His fame was eventually such that Henry Ford would court him aggressively and offer to put him in charge of his entire factory in 1923. Czochralski politely declined.
Absent-Minded Professor?
For someone who was so driven and devoted to the field of chemical metallurgy, and for as methodical as Czochralski reportedly was, it’s ironic that what he is perhaps best known for, and the discovery that would certainly become his most important legacy, was the result of an accident. In 1916, as the story goes, Czochralski was making some notes on a metallurgical experiment at his bench. Intent on his notebook pages, he didn’t notice that instead of dipping his pen into the inkwell, he had dipped it into a crucible of molten tin. The story may be apocryphal, given that the melting point of tin is 232 °C and it would be unlikely that a careful experimenter like Czochralski would be so cavalier with a pot of molten metal, but however the pen got into the tin, the result was interesting.
When he withdrew the pen, a fine whisker of tin was drawn up with it from the pool of molten metal. Curious as to the nature of the thread, Czochralski analyzed it and was surprised to find that it was a single crystal. He continued to experiment with the technique, replacing the pen nib with various capillary tubes, and adding seed crystals to provide nucleation sites for crystal formation. He was soon able to produce single crystals of various metals up to 1 mm in diameter and as long as a meter and a half. In addition to tin, he used his method to produce crystal filaments of lead and zinc.
Czochralski duly reported his findings in 1917, and though there was an initial burst of experimentation by others into the “Czochralski method”, the distractions of back-to-back world wars left the work largely in obscurity. He continued working in the chemical industry for the rest of his life, and would live long enough to see researchers at Bell Labs — it’s always Bell Labs — rediscover his process in the late 1940s and apply it to materials he never imagined working with, like silicon and germanium, as they began to invent the semiconductor industry.
The details of the Czochralski process for producing the single enormous silicon crystals, or boules, that are the raw material of almost every semiconductor product made today varies from the original method only in minor details, and of course in the scale of production. Silicon boule production is carried out in an induction furnace that has precise temperature control and can be provided with an inert atmosphere such as argon. The process starts when a quartz crucible is charged with ultrapure (99.9999%, or one non-silicon molecule in a million) polycrystalline silicon. The furnace is heated to about 1,500 °C while the crucible slowly rotates.
When the polysilicon has melted, a puller rod is lowered into the molten silicon pool. The end of the puller rod carries a seed crystal of silicon in a precise orientation, to serve as a nucleation site for crystallization. The puller rod, which is rotating in the opposite direction from the crucible, remains in the molten silicon for a short time before slowly being withdrawn. The molten silicon has by this point started to crystallize, and the puller rod begins accumulating a cone of crystalline silicon in the same orientation as the seed crystal.
Eventually the growing crystal reaches its maximum diameter, and the boule becomes more cylindrical. The diameter of the boule can reach up to 300 mm routinely, although 450 mm diameter processes are currently being prototyped; a theoretical maximum of 675 mm is possible but has not been attained. The boule continues to grow as it is withdrawn, a single crystal of silicon dangling from the puller rod and eventually weighing several hundred kilograms. The video above gives a good overview of the entire process, from production of polycrystalline silicon from quartzite sand through boule formation, and on to the fascinating details of processing the boule into wafers.
The Czochralski process is not only used for silicon crystals. Synthetic gemstones, including ruby, sapphire, garnet, and spinel can be grown using the method. On the other hand, the method is far from the only way of making ingots of monocrystalline silicon.
The float-zone process, also developed at Bell Labs, uses RF energy to heat a zone within a rod of polycrystalline silicon. It can produce silicon of much higher purity since the melt isn’t exposed to oxygen by the quartz crucible of the Czochralski method. There’s also the Bridgman–Stockbarger method, which is basically an upside-down version of the Czochralski method.
At the end of the day, though, Jan Czochralski’s accidental discovery of a crystal-growing technique has stood the test of time, as something like 90% of silicon wafers are cut from boules grown using his method.
If you were to travel back in time to the turn of the previous century and try to convince the average person that the grains of sand on just about any beach would be the basis of an industry worth hundreds of billions of dollars within 100 years, they’d probably have thought you were crazy. Aside from being coarse, rough, and irritating, sand is everywhere, and convincing anyone of its value would be a hard sell, unless your interlocutor was a real estate visionary with an appreciation of the future value of seaside property and a lot of patience.
Fast forward to our time, and we all know the value of the material that comes from common quartz sand: silicon, specifically the ultra-purified crystals of silicon that end up as the wafers we depend on to build the circuitry of life. The trip from beach to chip foundry is a long and non-obvious one which would not have been possible without the insights of an undistinguished Polish student and one-time druggist who discovered the process that made the Information Age possible: Jan Czochralski.
Those Who Can’t Teach
Born in 1885 in what is now Kcynia, Poland but was then part of the Prussian Empire, Jan Czochralski showed an early aptitude for chemistry. As always seems the case with chemistry prodigies, an early experiment in his home laboratory resulted in an explosion. His father, a carpenter, had aspirations that Jan would one day become a teacher, but despite his love of chemistry, or perhaps because of it, Jan’s grades were poor enough to preclude him from that career path. As an alternative, he left home and took a job in a drug shop, vowing only to return to his hometown once he had become rich and famous.
Jan Czochralski, circa 1910
Jan continued his studies on his own and progressed through a series of jobs in Germany’s burgeoning chemistry industry. He was largely self-trained when he applied to and was accepted by the Technische Hochschule in Berlin Charlottenburg, where he would specialize in metallurgy. Soon thereafter, as a newly minted chemical engineer at the Germany electrical giant AEG, he began studies into the applications in electronics of what was then an exotic and expensive material: aluminum.
Czochralski’s career was advancing rapidly on the value of his metallurgical research and the degree to which he published his findings. His work was cited frequently, so much so that he would one day become one of the most referenced Polish scientists, no mean feat when the list includes names like Marie Skłodowska Curie and Stanisław Ulam. His fame was eventually such that Henry Ford would court him aggressively and offer to put him in charge of his entire factory in 1923. Czochralski politely declined.
Absent-Minded Professor?
For someone who was so driven and devoted to the field of chemical metallurgy, and for as methodical as Czochralski reportedly was, it’s ironic that what he is perhaps best known for, and the discovery that would certainly become his most important legacy, was the result of an accident. In 1916, as the story goes, Czochralski was making some notes on a metallurgical experiment at his bench. Intent on his notebook pages, he didn’t notice that instead of dipping his pen into the inkwell, he had dipped it into a crucible of molten tin. The story may be apocryphal, given that the melting point of tin is 232 °C and it would be unlikely that a careful experimenter like Czochralski would be so cavalier with a pot of molten metal, but however the pen got into the tin, the result was interesting.
When he withdrew the pen, a fine whisker of tin was drawn up with it from the pool of molten metal. Curious as to the nature of the thread, Czochralski analyzed it and was surprised to find that it was a single crystal. He continued to experiment with the technique, replacing the pen nib with various capillary tubes, and adding seed crystals to provide nucleation sites for crystal formation. He was soon able to produce single crystals of various metals up to 1 mm in diameter and as long as a meter and a half. In addition to tin, he used his method to produce crystal filaments of lead and zinc.
Czochralski duly reported his findings in 1917, and though there was an initial burst of experimentation by others into the “Czochralski method”, the distractions of back-to-back world wars left the work largely in obscurity. He continued working in the chemical industry for the rest of his life, and would live long enough to see researchers at Bell Labs — it’s always Bell Labs — rediscover his process in the late 1940s and apply it to materials he never imagined working with, like silicon and germanium, as they began to invent the semiconductor industry.
The details of the Czochralski process for producing the single enormous silicon crystals, or boules, that are the raw material of almost every semiconductor product made today varies from the original method only in minor details, and of course in the scale of production. Silicon boule production is carried out in an induction furnace that has precise temperature control and can be provided with an inert atmosphere such as argon. The process starts when a quartz crucible is charged with ultrapure (99.9999%, or one non-silicon molecule in a million) polycrystalline silicon. The furnace is heated to about 1,500 °C while the crucible slowly rotates.
When the polysilicon has melted, a puller rod is lowered into the molten silicon pool. The end of the puller rod carries a seed crystal of silicon in a precise orientation, to serve as a nucleation site for crystallization. The puller rod, which is rotating in the opposite direction from the crucible, remains in the molten silicon for a short time before slowly being withdrawn. The molten silicon has by this point started to crystallize, and the puller rod begins accumulating a cone of crystalline silicon in the same orientation as the seed crystal.
Eventually the growing crystal reaches its maximum diameter, and the boule becomes more cylindrical. The diameter of the boule can reach up to 300 mm routinely, although 450 mm diameter processes are currently being prototyped; a theoretical maximum of 675 mm is possible but has not been attained. The boule continues to grow as it is withdrawn, a single crystal of silicon dangling from the puller rod and eventually weighing several hundred kilograms. The video above gives a good overview of the entire process, from production of polycrystalline silicon from quartzite sand through boule formation, and on to the fascinating details of processing the boule into wafers.
The Czochralski process is not only used for silicon crystals. Synthetic gemstones, including ruby, sapphire, garnet, and spinel can be grown using the method. On the other hand, the method is far from the only way of making ingots of monocrystalline silicon.
The float-zone process, also developed at Bell Labs, uses RF energy to heat a zone within a rod of polycrystalline silicon. It can produce silicon of much higher purity since the melt isn’t exposed to oxygen by the quartz crucible of the Czochralski method. There’s also the Bridgman–Stockbarger method, which is basically an upside-down version of the Czochralski method.
At the end of the day, though, Jan Czochralski’s accidental discovery of a crystal-growing technique has stood the test of time, as something like 90% of silicon wafers are cut from boules grown using his method.
[Ty Palowski] doesn’t like folding his many shirts. He saw one of those boards on TV that supposedly simplifies folding, but it does require you to manually move the board. That just won’t do, so [Ty] motorized it to create a shirt folding robot.
The board idea is nothing new, and probably many people wouldn’t mind the simple operation required, but what else are you going to do with your 3D printer but make motor mounts for a shirt folding machine. The folding board is, of course, too big for 3D printing so he made that part out of cardboard at first and then what looks like foam board.
The side “wings” were easy to manipulate, but the top fold required a little more effort. The machine still requires a manual fold at the end and, of course, you have to put the shirt on the right way for things to work out.
Honestly, we aren’t sure this is a very practical project, but we still enjoyed the idea and we can’t deny it seems to work. We don’t think there’s much torque required so we wondered if some beefy RC servos would have been just as effective and probably a lot easier to work with. Still, just about anything that could move would work. You could probably even use a spring and a solenoid to get the same effect. There’s not much build detail, but we think you could figure it out using whatever motors you happen to have on hand.
If you find laundry too time-consuming, there’s always Eleven. If you want a better folding robot, you’ll have to put in some serious work.
