All things badminton, just a little closer. SEM images download link below.
This is the first post of the Badminton Under the Microscope series and in this post, we will be looking at Yonex racket strings using two types of microscopes, an optical microscope and a scanning electron microscope (SEM). The models of strings that we are going to looking at today are the legendary Yonex BG-80 (in both pink and sky blue), the up and coming ultra-popular Aerobite (including the Aerosonic which is used as a cross string), and ultimately the BG-66 Ultimax.
I started with the optical microscope. I took a craft mat and used it as a base for the optical microscope. Then, using my fingers to hold the string in place, I adjusted the microscope to focus and magnify the strings.
For the SEM, I had to cut the strings into tiny bits, small enough to fit into the 1cm diameter carbon dot of the vacuum chamber.
Let's take a look at the pink BG-80 string first. At 25 times magnification under the optical microscope, you can see how clearly printed the BG-80 printing is. If you have your badminton racket with you, go take a closer look at your strings now to feel how much magnification we've had to clearly see the printing on our strings. You can also see that there are plenty of fibres encased in the pink outer casing of the string. I tried to use the tweezers to poke and mess around with the nylon filaments inside and they actually felt very soft and has a stretchy feeling to it and as they're nylon filaments, which tend to be stretchy and able to store energy under tension.
Have you also noticed the little holes on the string? I have circled them out in blue in the photo above. BG-80 is known for having a grippy and rough feel on its surface but I did not expect to see holes in the casing of the string.
Moving on to the sky blue version of the BG-80, here you can better see the internals of the string and the holes perhaps due to its more transparent outer casing. It looks like there are plenty of filaments and fibres in the core of the string, which is not surprising as all Yonex badminton strings are multifilament strings. The image from Yonex's BG-80 packaging shows that there are weaves on the outer casing of the string, and I was really pleased to be able to see those weaves under the optical microscope, though I must say that the weaves are not obvious.
Here is a photo of the BG-80 magnified to around 25 times in the SEM. Can you see the holes on the string clearly?
We now move onto the Aerobite. Stringers and users of the Aerobite know this string really grips and bite onto the shuttle. From my recent racket research of players at the Tokyo Olympics, I realise there are quite a number of players using the Aerobite. They are easier to spot than other strings because of their dual coloured nature with the mains and crosses in different string colours. The main string is the one that is grippy, whereas the cross string is actually the Aerosonic string which is superfine and very smooth in comparison.
Let's start by looking at the grippy mains. Under the optical microscope, you can see that there are two little triangles or love hearts before the 'Aerobite' printing. So far I've not seen these shapes on other strings. You can also see that the weaves are finer and tighter compared to the BG-80 and there are some slight holes on the casing of the string as well. Perhaps this is a design feature of grippy badminton strings from Yonex.
At the core of the Aerobite string, you can see how fine these individual strands are. If we were to optically compare the Aerosonic cross string, instantly you can see the string is smoother and less textured compared to the red Aerobite main string and it is also thinner in diameter.
Here's a further comparison with the BG-66 Ultimax. The Ultimax is clearly shinier than the rest of the group and also has a very fine weave of its outer casing. You can see how bumpy or more textured the casing of the Aerobite is compared to the Ultimax. The Aerobite is also slightly thicker than the Ultimax. You can see how smooth the Ultimax is and thicker than the Aerosonic under the microscope. The Ultimax also looks a lot shinier under the light.
Let's now look at the internal filaments of the Ultimax. Below are the images of the Ultimax magnified at 50 times, 100 times and 200 times respectively under the SEM and you can see how the casing is slightly crushed on the bottom whilst some of the filaments are squashed before breaking off. Based on the scale of magnification, I estimate each nylon filament to be around 20 microns and that's less than half of the thickness of a human hair which is typically around 70 microns!
Here are images of the inner filaments from the SEM when they are cut without a super sharp pair of cutters. They go everywhere and you can see how fine each filament is. Imagine how many strands of filaments are needed to make a single string.
I hope you've found this post interesting. Let me know what else you want me to take a look at for the Badminton Under the Microscope Series and there will be more posts coming soon. See you in the next one!
SEM Images full resolution download link: HERE