Score
Title
439
AskScience Panel of Scientists XVII
2197
Why is the Congo River so deep?
7375
Are there any predators that hunt for sport rather than for food?
11
When water does down the drain, why does it always go down the drain in a form of whirlpool.?
25
What causes the thick mist/fog that I frequently see coming off of mountains in my area?
7
What makes things transparent?
5
What allows certain cars and airplanes to have their own Wifi?
182
Why are hail storms so short?
17
Many poisonous and venomous vertebrates get their toxins from toxic arthropods that form part of their diets. Why can't they just form the toxins themselves the same ways their prey do?
58
If aliens were to look at earth through a telescope from 65 million lightyears away, would they see dinosaurs?
2
How Bayes rule was used to help with aiming cannons?
10715
What exactly does the cold virus do to me to make me so weak?
10
Why does fire flicker?
30
What exactly is string theory and how does it work?
14
Are initial telomere lengths fairly consistent in mammals? Barring external circumstances, do they decay at the same rate?
4
I understand conduction and radiation as modes of heat transfer, but convection confuses me. Why does fluid moving over an object remove heat from it as opposed to adding heat due to friction?
15
What happens to the brain as you fall asleep? Are certain proteins released to induce sleep? Is it seen as a voluntary or involuntary action?
6
How do transitors amplify?
17
Why do some things burn and some things melt?
1
Is there a limit to the energy density of batteries?
11
Why does an animal like the sea otter have a long gestation period (145-325 days) but only have a lifespan of 15 years or so. Is there a relationship between gestation period and lifespan across marine mammals like that/or any other mammal?
7
Which modern encryption standards would be both practical to implement on a large scale using technology from the 1940s and still effectively unbreakable today?
4
How much does it actually cost to maintain the internet?
10
What is the significance of a quasar discovered at 690 million years after big bang?
1
How do particle accelerators such as the LHC detect particle collision products?
6
Why does water not heat up through the friction created by movement (ocean waves/shaking it in a bottle)?
4
How do drug companies decide on the form(s) of delivery for a given drug?
5
[Embryology] - Is the notochord derived from the endoderm or the mesoderm? I have 2 conflicting sources.
5
What makes some batteries chargeable and others not?
19
Why do bigger and heavier molecules have a higher boiling point compared to smaller and lighter molecules?
8
Is there a coating that you can put on a surface to make it easier for frost to form on the surface?
4
Are there certain materials that behave like mirrors to other parts of the EM spectrum that do not look like mirrors to us?
3
Apart from humans do any other animals use drugs for recreation?
6
Are there any internal mechanisms of trees from S. Hemisphere (ex. Australia) that make them go “out of whack” when introduced in the N. Hemisphere?
4
If the “new” elements (e.g. Oganesson) have half-lives of microseconds or less, how do scientists know they’ve been synthesized at all?
2
Why is snow white and not transparent, like ice?
7
how does the temperature of a metal effect the hall voltage?
8044
Can a planet have more than 4 seasons?
1
What influences height? Other than genetics. Does where you are born and raised impact height?
1
How are we able to make transistors near the size of atoms?
0
Why is graphene so light?
5 NanotechNinja I use scanning tunneling microscopy (STM), which is a similar probe technique to AFM. (It has the "restriction" that you can only measure conductive samples, whereas AFM can measure insulators, but it allows you to get additional electronic information in addition to topology.) Our tips are made of polycrystalline tungsten wire, 0.25mm in diameter. We prepare them by a fairly standard electrochemical etching method, as follows. 1. A small beaker is filled with a solution of potassium hydroxide. 2. A ring shaped wire is positioned at the surface of the solution 3. The tip wire is suspended partially in the solution in the middle of the ring, and a voltage is applied between ring and tip wire. 4. This causes the tip wire to etch preferentially at the surface of the solution. 5. The weight of the section of the tip in the solution causes the area being etched to stretch out as it gets etched. 6. At some point, the lower section of the wire drops off. This has an associated drop in current, which we use as an indicator to stop the etching. (This is pretty important, if you don't stop the etching as soon as possible after dropoff, the newly formed tip gets blunter; the electronic trigger which detects current drop stops the voltage in about a microsecond) 7. The tip is rinsed in deionized water (to remove KOH residue) and inserted into ultra high vacuum ASAP. By this method we routinely achieve tips sharp enough for atomic resolution measurements. For standard AFM, I know that people typically use silicon nitride tips. I believe these are made by standard photolithography processes with a silicon wafer, and then the nitride layer is grown on top.
8 whitcwa Early on, they were made by smashing diamonds with hammers and then looking for good candidates with an optical microscope. They don't need to be smaller than the atoms they are imaging. If you use a rounded 25mm broomstick end, you can easily feel a 1mm bump.
5 bearsnchairs Some specialized AFM tips have a CO molecule on them, for subatomic resolution. http://aip.scitation.org/doi/abs/10.1063/1.4934273?journalCode=apl The reason why CO is used is because oxygen is one of the smallest atoms, and the CO bond is very stable and you don’t need to worry as much about it reacting with your surface like you might with fluorine.
4 cantgetno197 I don't know much about how they're made, though I'd imagine it's using the same techniques they use for all MEMs, which is basically what they are. You can read some basics on MEM fabrication process flow here: https://en.wikipedia.org/wiki/Microelectromechanical_systems#MEMS_basic_processes But they're definitely not smaller than the atoms they're manipulating. The tips are in the nanometers to 10s of nanometers range in size I believe. Which is about ~100-1,000 atoms wide.
7 0 NanotechNinja I use scanning tunneling microscopy (STM), which is a similar probe technique to AFM. (It has the "restriction" that you can only measure conductive samples, whereas AFM can measure insulators, but it allows you to get additional electronic information in addition to topology.) Our tips are made of polycrystalline tungsten wire, 0.25mm in diameter. We prepare them by a fairly standard electrochemical etching method, as follows. 1. A small beaker is filled with a solution of potassium hydroxide. 2. A ring shaped wire is positioned at the surface of the solution 3. The tip wire is suspended partially in the solution in the middle of the ring, and a voltage is applied between ring and tip wire. 4. This causes the tip wire to etch preferentially at the surface of the solution. 5. The weight of the section of the tip in the solution causes the area being etched to stretch out as it gets etched. 6. At some point, the lower section of the wire drops off. This has an associated drop in current, which we use as an indicator to stop the etching. (This is pretty important, if you don't stop the etching as soon as possible after dropoff, the newly formed tip gets blunter; the electronic trigger which detects current drop stops the voltage in about a microsecond) 7. The tip is rinsed in deionized water (to remove KOH residue) and inserted into ultra high vacuum ASAP. By this method we routinely achieve tips sharp enough for atomic resolution measurements. For standard AFM, I know that people typically use silicon nitride tips. I believe these are made by standard photolithography processes with a silicon wafer, and then the nitride layer is grown on top.
8 0 whitcwa Early on, they were made by smashing diamonds with hammers and then looking for good candidates with an optical microscope. They don't need to be smaller than the atoms they are imaging. If you use a rounded 25mm broomstick end, you can easily feel a 1mm bump.
3 0 bearsnchairs Some specialized AFM tips have a CO molecule on them, for subatomic resolution. http://aip.scitation.org/doi/abs/10.1063/1.4934273?journalCode=apl The reason why CO is used is because oxygen is one of the smallest atoms, and the CO bond is very stable and you don’t need to worry as much about it reacting with your surface like you might with fluorine.
4 0 cantgetno197 I don't know much about how they're made, though I'd imagine it's using the same techniques they use for all MEMs, which is basically what they are. You can read some basics on MEM fabrication process flow here: https://en.wikipedia.org/wiki/Microelectromechanical_systems#MEMS_basic_processes But they're definitely not smaller than the atoms they're manipulating. The tips are in the nanometers to 10s of nanometers range in size I believe. Which is about ~100-1,000 atoms wide.