Why Shaving Blades Become Useless After Cutting Human Hair

For a long time scientists have been fascinated with one problem when it concerns blades. Although blades are made of stainless steel and have edges that are razor-sharp, to further strengthen them they are coated with diamond-like carbon, but a material that is 50 times softer than a blade such as a human hair can be able to make the blade useless over time. From a logical point of view, this should not be the case.

 

Intrigued by this problem, the engineers at MIT’s department of Material Science and Engineering have come up with an innovative solution. These engineers concern themselves daily with exploring the microstructure of materials in order to design and make new materials that could be able to have exceptional damage-resistance properties. The lead researcher, Gianluca Roscioli, an MIT graduate student, came up with his idea when he was shaving his own hair.

After noticing that his blades tend to get dull with time after shaving, he decided to take images of the blades after each shaving activity. He took these images with a scanning electron microscope (SEM), scanning the blade’s edge in order to track how the blade wore down over time. What he discovered showed that the process is much more complex than a simple wear over time. He noticed very little wear and rounding out at the edges but instead realized that chips were being formed around certain regions of the razor’s edge. These led him to ask himself: Under what conditions do these chipping take place, and what are the ingredients for a strengthened blade to fail after shaving a material as soft as human hair?

To answer these questions conclusively he built an apparatus that was designed to fit inside an SEM and he used it to take samples of his shaving and that of his colleagues. They found that there were some conditions that might cause the edges of a blade to chip and as the chipping proceeds with time, it will cause the blade to get dull. The conditions depend on the blade’s microstructure. If the blade is heterogeneous or the microscopic structure is not uniform, the blade will be more prone to chipping. Also, the angle at which the cutting was done was found to be significant. Therefore, they found that shaving at right angles were better than lower angles. Finally, the presence of defects in the steel’s microstructure was another factor that played a role in initiating cracks on the blade’s edge. Chipping was found to be more prominent when the human hair met the blade at a weak point in the blade’s heterogeneous structure.

These conditions illustrate a mechanism that is well known in engineering - stress intensification. This is the intensification of the stress applied to a material because the structure of the material has microcracks. Once an initial microcrack has formed, the material’s heterogeneous structure enabled these cracks to easily grow to become chips. Therefore, even though the material might be fifty times stronger than what it is cutting, the heterogeneity of the material can increase the stress on it, making cracks to intensify.

The implications of this discovery is immense. It will save money and costs to the average user of shaving blades because it will offer clues on how the edges of a blade can be preserved, and give manufacturers the opportunity to make better blades or cutting materials by using more homogenous materials.

The engineers have already taken their discovery one step further. They have filed a provisional patent on a process to manipulate steel into a more homogenous form, with the hope that they could use this process to build longer-lasting, and more chip-resistant blades.

Material for this post was taken from the MIT news website.

A Microscopic View Of Python’s Lookbehind and Lookahead Regex Assertions

Any discussion on regular expressions, or regex, is not complete without taking note of the lookaround assertions. Lookaround assertion in regex are assertions that state that at the current position of the string, check whether so and so pattern exists before or after the string. Note that when doing lookarounds, the string used in the lookaround is not consumed and the current position in the string does not change.

Now we will be making use of four types of lookaround assertions in regex today. They are the positive lookbehind, the negative lookbehind, the lookahead, and lastly the negative lookahead assertion.

 

The Positive and Negative lookbehind assertions.

In lookbehind assertions, we are only looking for what precedes the current position in the string that we want to match. The pattern in the lookbehind assertion does not participate in the match, or as it is said, is not consumed in the match. It only helps in asserting that the match is true. Lookbehind can be positive or negative. In positive lookbeind assertions, we are asserting that the pattern is present before the string. In negative lookbehind assertions, we are asserting that the pattern is not present before the string.

The syntax for positive lookbehind assertion is (?<=foo) where a match is found if foo precedes the current position of the string that is to be matched and foo ends at the current position.

Let’s illustrate this with some example. For example, let’s assert some currency figures. If we have a string like ‘USD100’ and we only want to match 100. We can assert that USD should come before the number 100 with this code: (?<=USD)\d{3} which states to match a digit consisting of exactly 3 characters which is preceded by the string, USD.

The syntax for the negative lookbehind assertion is (?<!foo) which matches the current position of the string if foo is not before the string. If we could continue with the string, ‘USD100’, then to say that the EURO should not be in the string we could use the code: (?<!EURO)\d{3}. I believe by now you must understand what the pattern represents.

Now, we will go on the the second set of lookaround assertions which are the lookahead assertion and negative lookahead assertion.

The lookahead and negative lookahead assertions.

The lookahead assertions are just the opposite of the lookbehind assertions. The lookahead assertions look for the pattern or non-existence of the pattern ahead of the current position in the string.

The lookahead assertion looks for the existence of the specified pattern from the current position. The syntax of the lookahead assertion is (?=foo) where from the current position of the string we are looking ahead if foo exists. Let’s take our 'USD100' string again. If we want to do a lookahead to see if the number exists after the dollar symbol, we could use the following code: w{3}(?=\d{3}). But the 100 number is not consumed in the match, we are taking out only the USD, just that we only want to assert that the 100 comes after the USD.

The negative lookahead assertion is an opposite of the lookahead assertion. If included in a pattern, it asserts that the pattern in the assertion does not come after the current position in the string. For example, if we have the following string 'USD100' and we want to assert that it is not 'USD200' we could use the following code: \w{3}(?!200). The code states that we are matching any string that has three letters but without 200 following it literally.

So, that is what we can take from the lookaround assertions in python. Now, let’s use our knowledge to solve a problem.

Assuming you are given the following string, rabcdeefgyYhFjkIoomnpOeorteeeeet, and you want to match all substrings of the string that contain 2 or more vowels on the condition that each of the substrings must lie between two consonants and must only contain vowels. How do you go about it.

If you look at the question, it involves lookbehind and lookahead assertions. That is, a consonant must lie before the vowel (lookbehind) and must also lie ahead of the vowels (lookahead). When you understand this, your work is nearly done. Then we must denote what it means to have a consonant. That means, it must be any letter that does not lie within the set of vowels, [aeiou]. We will be doing a case-insensitive match, so we will have to raise the Ignore case flag for the regex search pattern, re.I.

Here is how the code is written:

There is nothing new in the code. I have already explained most of the code in another blog post, entitled: The Big Advantage of Understanding Python Regex Methods.

You can download the script here if you want to take a deeper look at it.

I hope you have a nice day. If you want to keep receiving python updates like this, just subscribe to the blog using your email.

A Game Changing, Innovative, Microscale E-waste Recycling Strategy For The Environment And Manufacturing.

A typical recycling process involves the following – waste is collected, sorted, cleaned and processed, then the processed waste is used to manufacture more of the same product, and the cycle is closed when consumers buy these products. The recycling process depends on the fact that these collected waste are made of the same material. That makes it possible to manufacture new products. Yet, that is not the typical case for e-waste.

E-waste, or electronic products that are no longer working, unwanted, or close to the end of their useful lives, are usually made of heterogeneous materials which cannot be readily separated. Therefore, recycling them and putting them back into the cycle does not seem too commercially profitable for the average manufacturer. Yet, these wastes have to be recycled because if they are put back into the environment, which turns out to be usually the case, the toxic materials contained in them can poison our soil, water, air, or wildlife. 

 

To solve this problem some researchers have developed a selective, small-scale microrecycling strategy which can be used to convert old printed electronic parts like circuit boards and monitors into a new type of strong metal coating. These researchers, Veena Sahajwalla and Rumana Hossain, based their research on the copper and silica that are usually the components of electronic devices. They realized that based on the properties of these compounds they could be extracted from e-waste, then combined at high temperatures, even up to 2,732 F, thereby in the process generating silicon carbide nanowires which can then be processed further to create a durable, new hybrid material that is ideal for protecting metal surfaces.

These technique is innovative and a game changer. This could reduce the number of e-waste that end up in landfills and make it profitable for recycling plants to go into recycling larger amounts of e-waste. Imagine, the typical electronic device like a laptop and a TV screen contains lots of potentially valuable substances that could be used to modify the performance of other materials or used to manufacture new reliable materials. That is what this innovation makes possible. Also, the process, which the researchers have called material microsurgery, could be used to recover a large amount of copper annually for use in industries such as electronic devices, industrial, transportation, and consumer products.

Imagine the number of jobs that could be created in the recycling industry if e-waste was taken out of the ecosystem daily. Imagine what benefits it would bring to our environment not to have to dispose of these devices in landfills where they could percolate back to our water cycle or food.

These material microsurgery technique could also be used to create durable, new hybrid materials that could be used to protect metal surfaces. Yes, and it has been tested. During laboratory experiments it was discovered that the hybrid materials when fixed to steel remain firmly entrenched and when the steel is struck with a nanoscale indenter the hybrid layer does not get detached from the steel but remains firm, showing no signs of cracking or chipping. Further, it was seen to increase the hardness of steel by about 125%.

The potential benefits of this small-scale microrecycling strategy is very high. Thanks to the innovation of these two researchers, we could have a cleaner environment free from e-wastes and making sure more electronic products are not disposed of improperly.

I included this innovation in my blog because of its high potential benefit to mankind. I think this is a problem solved and worthy of being acclaimed.

Materials for this post were taken from a press release by the American Chemical Society, ACS.