Graphene And Copper Nanowire Thermal Interface With Low Thermal Resistance

With the increasing waste heat production by today’s electronics in ever smaller spaces, drawing this heat away quickly enough to prevent thermal throttling or damage is a major concern. This is where research by Lin Jing and colleagues from Carnegie Mellon University’s Department of Mechanical Engineering demonstrates a thermal interface material (TIM) that should provide a significant boost here. In the article, published in ACS Nano (paywalled; open access preprint alternative) the construction of this copper and graphene ‘sandwich’ TIM is described, along with tests.

The general idea is to use pillars between the two surfaces that can quickly carry the heat from the hot surface to the cool one. Although pure copper versions exist and do work, they suffer from the complications of having to build up these copper pillars in place, and subsequent oxidation reducing the effectiveness. While graphene and similar materials have shown superior heat-transfer capabilities, interfacing these materials with copper and other metals has proven problematic.

What Lin Jing et al. demonstrate in this study is to use essentially the pure copper approach, but to combine it with earlier research by Raghav Garg et al. (2017), who demonstrated how to grow 3-dimensional graphene structures. By cladding the copper pillars with graphene, this material improves heat transfer by 60%, while preventing oxidation of the metal. While the challenge is obviously to transfer these findings to something that can be mass-produced for consumer devices, it demonstrates how much potential there is in the use of graphene, which is a relatively new material for such applications due to how hard it was to produce until recently.


Increasing PV Solar Cell Efficiency Through Cooling

An unavoidable aspect of photovoltaic (PV) solar panels is that they become less efficient when they warm up. [Tech Ingredients] explains in a new video the basic reason for this, which involves the input of thermal energy affecting the semiconductor material. In the subsequent experiment, it is demonstrated how cooling the backside of the panel affects the panel’s power output.

There are commercial solutions that use water cooling on the back of panels to draw heat away from panels, but this still leaves the issues of maintenance (including winter-proofing) and dumping the heat somewhere. One conceivable solution for the latter is to use this heat for a household’s hot water needs. In the demonstrated system a heatsink is installed on the back of the panel, with fans passing cool air over the heatsink fins.

On a 100 Watt PV panel, 10 W was lost from the panel heating up in the sun. After turning on the fans, the panel dropped over 10 °C in temperature, while regaining 5.5 W. Since the installed fans consumed about 3 W, this means that the fans cost no extra power but resulted in increased production. Not only that, but the lower temperatures will in theory extend the panel’s lifetime. Though even with active cooling, even the best of PV panels will need to be replaced after a couple decades.

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Cool Face Mask Turns Into Over-Engineered Headache

Seeing his wife try to use a cool face mask to get through the pain of a migraine headache, [Sparks and Code] started thinking of ways to improve the situation. The desire to save her from these debilitating bouts of pain drove him to make an actively cooled mask, all the while creating his own headache of an over-engineered mess.

Void spaces inside the printed mask are filled with chilled water.

Instead of having to put the face mask into the refrigerator to get it cold, [Sparks and Code] wanted to build a mask that he could circulate chilled water through. With a large enough ice-filled reservoir, he figured the mask should be able to stay at a soothing temperature for hours, reducing the need for trips to the fridge.

[Sparks and Code] started out by using photogrammetry to get a 3D model of his wife’s face. Lack of a compatible computer and CUDA-enabled GPU meant using Google Cloud to do the heavy lifting. When they started making the face mask, things got complicated. And then came the unnecessary electronics. Then the overly complicated  and completely unnecessary instrumentation. The… genetic algorithms? Yes. Those too.

We won’t spoil the ending — but suffice it to say, [Sparks and Code] learned a cold, hard lesson: simpler is better! Then again, sometimes being over-complicated is kind of the point such as in this way-too-complex gumball machine.

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The Benefits Of Displacement Ventilation

The world has been shaken to its core by a respiratory virus pandemic. Humanity has been raiding the toolbox for every possible weapon in the fight, whether that be masks, vaccinations, or advanced antiviral treatments.

As far as medicine has come in tackling COVID-19 in the past two years, the ultimate solution would be to cut the number of people exposed to the pathogen in the first place. Improving our ventilation methods may just be a great way to cut down on the spread. After all, it’s what they did in the wake of the Spanish Flu.

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PCB Thermal Design Hack Gets Hot And Heavy

Thanks to the relatively recent rise of affordable board production services, many of the people reading Hackaday are just now learning the ropes of PCB design. For those still producing the FR4 equivalent of “Hello World”, it’s accomplishment enough that all the traces go where they’re supposed to. But eventually your designs will become more ambitious, and with this added complexity will naturally come new design considerations. For example, how do you keep a PCB from cooking itself in high current applications?

It’s this exact question that Mike Jouppi hoped to help answer when he hosted last week’s Hack Chat. It’s a topic he takes very seriously, enough that he actually started a company called Thermal Management LLC dedicated to helping engineers cope with PCB thermal design issues. He also chaired the development of IPC-2152, a standard for properly sizing board traces based on how much current they’ll need to carry. It isn’t the first standard that’s touched on the issue, but it’s certainly the most modern and comprehensive.

It’s common for many designers, who can be referencing data that in some cases dates back to the 1950s, to simply oversize their traces out of caution. Often this is based on concepts that Mike says his research has found to be inaccurate, such as the assumption that the inner traces of a PCB tend to run hotter than those on the outside. The new standard is designed to help designers avoid these potential pitfalls, though he notes that it’s still an imperfect analog for the real-world; additional data such as mounting configuration needs to be taken into consideration to get a better idea of a board’s thermal properties.

Even with such a complex topic, there’s some tips that are widely applicable enough to keep in mind. Mike says the thermal properties of the substrate are always going to be poor compared to copper, so using internal copper planes can help conduct heat through the board. When dealing with SMD parts that produce a lot of heat, large copper plated vias can be used to create a parallel thermal path.

Towards the end of the Chat, Thomas Shaddack chimes in with an interesting idea: since the resistance of a trace will increase as it gets hotter, could this be used to determine the temperature of internal PCB traces that would otherwise be difficult to measure? Mike says the concept is sound, though if you wanted to get an accurate read, you’d need to know the nominal resistance of the trace to calibrate against. Certainly something to keep in mind for the future, especially if you don’t have a thermal camera that would let you peer into a PCB’s inner layers.

A rig used to test thermal properties of different trace configurations.

While the Hack Chats are often rather informal, we noticed some fairly pointed questions this time around. Clearly there were folks out there with very specific issues that needed some assistance. It can be difficult to address all the nuances of a complex problem in a public chat, so in a few cases we know Mike directly reached out to attendees so he could talk them through the issues one-on-one.

While we can’t always promise you’ll get that kind of personalized service, we think it’s a testament to the unique networking opportunities available to those who take part in the Hack Chat, and thank Mike for going that extra mile to make sure everyone’s questions were answered to the best of his ability.

The Hack Chat is a weekly online chat session hosted by leading experts from all corners of the hardware hacking universe. It’s a great way for hackers connect in a fun and informal way, but if you can’t make it live, these overview posts as well as the transcripts posted to make sure you don’t miss out.

Apple II computer on a workbench

Simple Fan Controller Helps Apple II To Beat The Heat

In its day, the Apple II computer didn’t typically require active cooling. However, the increasing scarcity of replacement hardware convinced [Joshua Coleman] to come up with a more robust active cooling solution for his Apple II+, increasing the likelihood that it will keep on crunching numbers for decades to come.

Joshua mentions that he recorded temperatures inside his Apple II+ peaking at 110 Fahrenheit (over 43 Celsius). This isn’t totally unexpected for a fully-loaded Apple II system, and components were built to handle this – the original datasheet for the 6500 microprocessor family reveals that the CPU can handle temperatures as high as 158 Fahrenheit (70 Celsius). Unfortunately, we’re not dealing with brand new components anymore. Decades-old microprocessors don’t necessarily have the same thermal tolerance as they once did. All components will eventually wear out, and heat can certainly accelerate the aging process.

In the interests of maintaining his system, Joshua cobbled together an Arduino-based cooling system for his Apple II+. A temperature/humidity sensor continuously monitors the heat situation inside the case – when things get too toasty, a 12V fan powers up to draw fresh air over the logic board and expansion cards. A simple cooling curve reduces wear on the fan motor and relay.

This is hardly the first active cooling system for the Apple II line – in the 1980s, Kensington produced a popular (if not stupendously ugly) ‘System Saver’ accessory, an external bolt-on fan that kept things running cool. These were often deployed in schools and by power users looking for added reliability when maxing out the Apple II expansion slots, a configuration that could increase temperatures due to the extra power requirements and reduced airflow.

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Hacked AC Window Unit Split In Half To Cool The Garage

It’s getting into the hot summer months for those of us in the Northern Hemisphere, and for many Hackaday readers, that means its time to get the old window air conditioner out of storage and lug it back into position. But what if you’re trying to cool a space that doesn’t have a convenient window? In that case, this clever conversion that [Infrared] came up with to keep his garage cool might be of interest.

Basically, he’s taken the classic window AC and turned it into an impromptu ductless unit. By rotating the evaporator coils into a vertical position and lengthening the compressor wires, he was able to make the center of the AC thin enough that he could close his garage door over it. The back of the unit looks largely untouched, but the front side has a real Mad Max vibe going on; with sheet metal, exposed wiring, and a couple of fans thrown in for good measure. Fine for the garage or workspace, but probably not a great choice for the kid’s room.

[Infrared] says the hacked up AC can get his garage 18 degrees cooler than the outside air temperature in its current form, but he hopes the addition of some high CFM computer fans will not only improve performance, but let him make the new front panel look a bit neater. Though even in its current form, this is far from the most ridiculous DIY AC project we’ve seen in recent memory.

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