#22 Pt1: The Four Layers Inside a Supermarket Pad

Materials engineer Shagun Maheshwari spent five years building the world's first blood-coagulating menstrual pad. In Part 1, she explains why the industry tests pads against saline rather than blood, takes a conventional pad apart layer by layer, and reveals the reframe — keep dry, don't just absorb — that led to a pad which clots blood in place.

Key topics in this part:

• Why pads are tested against water/saline, and how menstrual blood differs
• The four-layer anatomy of a conventional pad (top sheet, ADL, core, back sheet)
• Super absorbent polymer (SAP) and why it collapses under body weight
• The reframe from "absorb more" to "keep the person dry"
• How a physical, charge-based clot works (vs the biological clotting cascade)
• The naturally derived long-chain sugar coagulant, and how it was found
• Whether some "period problems" are actually product-design problems
• Industry inertia around cheap, mass-produced SAP

Timestamps:

• 00:00 — Hookable intro
• 00:40 — Biohacking Eve intro
• 01:05 — Episode summary
• 02:05 — Conversation begins: from smart contact lenses to period pads
• 07:00 — Optimising for the wrong metric; periods vs product problems
• 14:00 — What's in blood, and why it's hard to engineer for
• 16:00 — Pad anatomy, layer by layer
• 20:00 — Why fluid comes back out under load
• 21:00 — How coagulation works inside Papaya's pad
• 28:00 — The coagulant material and how it was identified
• 31:00 — Cliffhanger → outro

References mentioned in this part:

• Mojo Vision — smart contact lens company
• Super absorbent polymer / sodium polyacrylate (SAP)
• Stayfree, Whisper/Always — pad brands referenced

Guest & product links:

• Website: papayapads.com
• Instagram: @papaya.india and @shagun.maheshwari
• LinkedIn (Shagun): https://www.linkedin.com/in/maheshwarishagun/
• LinkedIn (company): https://www.linkedin.com/company/papayaindia/

Insta/TikTok: @BiohackingEve
Website: www.BiohackingEve.com

Transcript

Judith Mueller 0:01

The entire menstrual products industry has been designing pads to absorb one thing: water. But menstrual blood is not water. It contains proteins, lipids, mucus, and endometrial tissue. So designing products for saline, the blue water you see in the pad advertisements, when the actual fluid is blood, is a previously unexamined flaw in consumer product engineering. So today we're looking at a solution. Excuse the chemistry pun. What if instead of designing a pad to absorb blood as fast as possible, you designed it to clot it, to solidify it in place, the way your own body's biological mechanism works, so it never moves, it never leaks, and it never creates that uncomfortable wet feeling against the skin? This is exactly what today's guest has built, and she did it without having plastic against your skin, which is a known endocrine disruptor.

1:00

Welcome back to Biohacking Eve, health Optimization for Women with Judith Miller, where we shine a large on everything that will help you reach your best self as a woman, as unique and individual as then you can be live long and prosper my friend.

Judith Mueller 1:20

Welcome back to Biohacking Eve. If you've been listening for a while, you will know we have spent quite a lot of time exploring what goes on at the vaginal level, the microbiome, the bacteria that protect us, the diagnostic tools that are beginning to change what periods can tell us about our health. We've also looked at the history of the tampon itself, which is a rather remarkable story. So today we're going a layer further out and asking the question: What is actually inside the pad you've been wearing since you were a teenager? And critically, was it ever actually designed for blood? My guest today is a materials engineer who spent over five years in the lab building the answer to that question from scratch. This is not a wellness story. This is a material science story, and it starts with a flaw in the engineering promise that's gone unchallenged for decades. Let us get into that. Shagun Maheswari is a mechanical engineer with a master's degree from Duke University and a background in advanced process development, material science, and fluid dynamics. Before founding Papaya Pads, she contributed to the development of the world's first smart contact lens, which I think is pretty cool. So she's spent the last five years developing what is to date the world's first blood-coagulating menstrual pad. Shagun, welcome to Biohacking Eve.

Shagun 2:36

Thank you for having me, Judith. It's really nice to be here

Judith Mueller 2:40

Fantastic. So you went from contributing to the world's first smart contact lens to building the world's first blood-coagulating menstrual pad. Walk us through that leap. What was the thing that made you look at menstrual products and think, "This is an engineering problem I wanna solve"?

Shagun 2:56

So yeah. So basically I'm a mechanical engineer and I was I have been working in Silicon Valley for eight years. And then I was working at Mojo, that was a smart contact lens company. I have been obsessed with menstruation for a while, like way from s- for a very long time. And the idea was to just basically get a better product for myself. What would irk me personally is that I'm having to throw like plastic pads every month and they don't feel very good, and I just wanted something better. So I tried a bunch of products on the market, fell in love with the menstrual cup, and I thought that as an engineer the problem is solved, right? It-- you put it in, it-- you don't feel it. It's great. I bought the cup, I gave it to family and friends, and I realized that it's very hard for people to give up like a habit, to change habit. And some people it works great, but it's not a solution for everybody for a variety of reasons. Either it's like sociocultural or it's stuff like you have an IUD, you don't feel comfortable, just various things. And so I figured It is-- it may be engineering-wise solved, but it is not something that is accessible to everybody. And what can we do to what product really is the most widely used one for periods? And it is a pad. All over the world, 50% of menstruating women use pads. Even in countries where you think tampons have existed for so long and you think who even uses a pad? It's the 50% still more or less works out. So but the problem with pads is that you can get the plastic pads or you can get natural fiber pads, but the natural fiber, the more sustainable ones, don't feel as good or functional as the plastic ones because you feel like you have to change them more often. You feel just more wet, and they're thicker. So the thing was this weird trade-off that you go for sustainable, better for health, and you get the functional, I-it's always "Oh, it's sustainable, it must be less effective." And that was something that I really wanted to break. and so I realized that the thing the onus of making a healthier choice or a more sustainable choice should not be a place of moral high ground. It should be the default, and that w- that is what makes it like an engineering problem. This is a product problem, not a you can't expect people to change, work their lives around, especially for something as uncomfortable as a period to accommodate, either sustainability or like any of these things. So it has to change at the product level. That was the basic thought. And for pads, realized that m- plastic is very good at what it does. It's like there's a reason it's everywhere. And to r- to think about pads is "Oh, can I make a better absorbing but plastic replacement?" is limiting because any natural fiber, cotton, banana, like any natural fiber cannot compete with something like plastic, like super absorbent polymer. And I was messing with a bunch of things in the lab, and I realized that don't need to-- if we ask about absorbance, then we limit ourselves. But if we ask about what can make the person feel drier, then it opens up the space. Then we're no longer talking about how do I absorb the most amount of fluid? Then I'm asking how do I keep bl- menstrual blood in one place? How do I make the person feel dry? How do itchiness and the wet feeling? It's an entirely different question because blood inherently can clot And we just seem to have not utilized that as much as we could possibly have. And what happened was I was testing on myself, so I was testing on real menstrual blood, and it was just right there, like waiting for just to be of incorporated. And once you ask that question about how to keep dry and you have all of this this realization that I can clot blood, you don't need plastic for that. can happen with non-toxic, body safe all, know, naturally derived ingredients without any plastic, and it degrades and well. So now the question became, okay, how do I put it in a pad and make it comfortable? Which yeah, basically that's how the whole journey began.

Judith Mueller 7:24

So we're basically saying that, uh, the industry optimized for the wrong metric

Shagun 7:30

I think i-in a way I get it. Blood is very hard to work with. I was testing on myself, but I was testing monthly. I c- you know, I had to be like, "Let's wait for the next cycle," which is ridiculous. You cannot... Most labs to deal with blood means to deal with a lot of added stuff. You need to make sure it's frozen. You need to make sure there's not in- not infected. Also, venous blood is different from menstrual blood. There's a lot of these things. So I get why, saline or salt water is used or regular water is used because it's just so much easier. It's also easier to standardize. So people do use synthetic blood, but that is just more viscous fluid. It is not necessarily as complex as blood. So there's this whole it's optimizing for, in my opinion, the wrong thing, but I also get why, because it's just really hard. I also fear that w- I, y- we are the generation that did not wear sort of homemade cloth pads. What we wore started with a pad, and the first pad I know is the Always, Whisper in India, the brand w- is Whisper. and I was a Whisper girl for the longest time. You commit to it. You commit to a pad brand, that's all you know. And just the I realized this recently. I've been talking to a lot of customers, and I realized that, oh, we haven't known what it felt to have a period without a, pad on the market. so a lot of the problems that we associate with periods oh, itchiness or rashes or stuff, may not be inherently period problems but product design problems. Yeah. And how would we tell? Because we don't know

Judith Mueller 9:22

I find it so interesting. I mean, you know, uh, uh, growing up in Germany, you basically get put on the pill at, I don't know, 12 years old or something. I mean, I was eating three bars of chocolate at the time, and I got horrible acne. Surprise, surprise. So the, the... I can't remember if it was the dermatologist or just d- a doctor just said, "Oh, you take the pill. That will sort you." Well, no one actually asked me what I was eating. That might have been a better indication. Um, and you just take it, you know? And then you're on hormonal contraception for whatever, 20 years of your life or something. So I actually only changed, um, to non-hormonal contraception in my early 30s. So literally 20 years of my life I was just taking something that as a teenager you get told, "Don't get pregnant, use this." And I think it's very similar with the pads, right? I mean, I personally never really, uh, was a fan of pads. I thought they were always leaky. There was always... I mean, even at night, just the fact that you're lying down, right? There's always like, you have, I don't know how many pants I've ruined just having little bits of blood on the end. And even I was trying to put little pieces of paper in my, in my, you know, bum crack as a way to try to catch these. I mean, I, I don't think this is really designed the way it's supposed to be, right? So the, the question is, and this might be a rhetorical question, but why are we never questioning these things? Why do we just grow up with one thing and never even look in the supermarket to see if there's something better? Is it because we don't talk about it as women? It's just you s- take whatever you grew up with, or what do you think it is?

Shagun 10:40

I think for periods it's a bit of a bunch of things. For the longest time, we just didn't talk about it. Only lately has it become a thing that we openly talk about bodily secretions of any kind, and periods are a big part of that. And also in a lot of cultures there's also the stigma around it's something either very personal, it's something dirty, it's something like all kinds of stuff, which thankfully we're slowly getting rid of. But I also feel that in the lab, the people designing products if they are not people who experience what it is to bleed, it is just very hard. It's not even ill intent. It's just hard. How are you going to design for something know only as a second secondary anecdote? That too where people don't talk as freely. So-

Judith Mueller 11:33

So you, you don't even know what the problems are. Yeah

Shagun 11:36

you're taking your best guess, and you're really trying to optimize for a thing, but that's your best guess. And and it helps that the super absorbent polymers also work really well for diapers, right? urine. And so I think it just was like oh, we can just optimize the heck out of this, and we get two products. Great. But period blood is just complicated and messy, and in the s- in the sense it is not a simple one ingredient fluid. It has so much stuff going on with it. And even, with, Like for instance period blood is salty, and a lot of the super absorbent polymers actually collapse or absorb less with salt concentrations. even the reduced absorption is significantly larger than any kind of n- fiber absorption. But it is a thing. Period blood or the vaginal region and the vaginal secretions are also acidic. Again, super absorbent polymer performs less well in acidic, salty environments. for stuff like the clumpy, clotty flow that we get sometimes, right? That is hard for any kind of mesh, plastic or cotton to let go through. So there's all of these with it. But it's like we, like we-- we, collectively we as a, as the people who are trying to design a product, just, what could we really do? When there's like- So hard to test with

Judith Mueller 13:07

So tell us a bit more what's actually in blood. Why is it so hard? Because we touched on some of these previously, but how are they... Because I think the other thing is also it's inconsistent, right? You're saying, for example, different days are different. So talk us through the challenges in more detail

Shagun 13:24

Yeah. So obviously salty and acidic matter you change your pH in your vaginal region and you have a infection of some kind. It's just, yeah. So products that we're close to up close against vaginal tissue need to be pH regulated, need to just work well, not just in absorbing or like keeping you dr- dry by what I mean is by taking up the fluid, but they also need to do no harm in the sense that how do we not disrupt the microclimate, know? And one of the things that keeps coming up, and this ties back into the fact that we didn't know any better because we've been using pads through all our life, is, I've been having customer calls with people and they say, "You know, it doesn't dry out my skin as much. I don't get skin dryness, which re- which I think reduces my itchiness." Super absorbent polymer is so good at absorbing that it's also absorbing moisture from skin, which you need, which you don't want to get like too dry because that's just exacerbating a chaffing, itchiness issue even more. this is one of those things that is just I just thought this was a given because it was something wet rubbing against my skin, not because of actually the opposite problem of too much dryness and hence messing with the skin microclimate. And yeah, we just kind of assumed that there is no better option

Judith Mueller 15:02

let's have a chat about what's actually in a period pad, in a sense, is how it's made up. So I think most women have no idea what the different layers are, what the different function, because it's not just, you know, when you have a, say, a cotton cloth, you know what it's made of. It's fairly obvious. But actually a period pad is a, I would actually say, highly complex design in, in and of itself. So let's start from first principles. If I handed you a standard supermarket pad, and you took it apart in the lab layer by layer, what would you actually find?

Shagun 15:34

Okay. Top layer is called the top sheet or the skin contact layer. That, th-that- the job of that layer is basically to just take the liquid away from the body straight into the pad. So just it should go straight through and away from you. So that's your first barrier to get fluid away from you. The second layer is called the acquisition distribution layer, and ADL for short. And what it really does is it literally takes the stuff from the top sheet and distributes it lengthwise across the pad so that you end up using the pad and not just the little area where you bleed in. So it's a distribution yeah, layer. Then you have your core, and different pads do this differently. They-- You can either have those fluffy... Stayfree does this. It has the fluffy core or the-- like us- most maxi pads have the fluffy like the thick ones have the fluffy core. Or the ultra-thin ones will have a tissue layer which has super absorbent polymer, the plastic the gelling thing. Is what does the heavy lifting of absorbing fluid And that is basically also the hardest to replace in sustainable pads, because that is what you're trying to compete with when you try to stuff a sustainable pad with all kinds of natural fiber, and that's what gives it, sustainable pads, the bulk. Because super absorbent polymer is super efficient at absorbing, so you can do like a thin layer, but you need at least 10 times the amount of cotton to keep up with it. Then you have your back layer, essentially. So roughly, it's these four layers. You may have differences depending on engineering differences. Like some people would, play with the repellency or the water-- like hydrophobic or the hydrophilic nature of the substrate. Basically, how much it attracts water, how much it repels water to The whole point of the pad is how do we guide liquid away from the body and keep it away from the bod-body even when the person is sitting on the pad, so under weight. what it's designed to do. And yeah, so it's a fluid management problem. And how do we also not get it to like overheat? How do we get enough airflow so that you don't just feel like you're sweaty in a raincoat? what I mean? The fabric needs-- like the pad needs to have some micro air channels so that there's vapor go-- like breathing through it. Otherwise, that will be rashes because of too much wetness. So you have like too much dryness rash, which happens anyways, but you have the really wet plastic chafing against you rash. So most of these people do this by the back sheet, which is mostly a plastic sheet, is have tiny pores in that, that make some, it's still leak-proof, like liquid won't go through, but air will. So you get the breathability

Judith Mueller 18:34

How is it in technical, technological functions that some things can, I mean, the theory is that blood on the sense water that we're testing on goes in but doesn't come back out. What is the theory behind that, and why does it not work in practice?

Shagun 18:50

Okay. Most of the so anything that is absorbing water, It's swelling up, and what is happening is the water is making space between the molecules and sort of like a balloon swelling the whole thing up. But there is no actual real, like a skin. It is still a, like a, like a mesh, right? In which you've entrapped water. put weight on it, where does it go? It will collapse. that collapsing of the un- like basically absorbency under load. So under weight, collapse, the surrounding pad needs to be able to keep it so that you still feel dry. So you won't have a perfectly dry top, right? Like you will have wetness because the water needs to go somewhere. But it's just relative, like how much can we keep away from... It's also like what you feel and what is the universal truth. Like it's like, how do you feel comfortable? So essentially just that, like the water needs to go somewhere. Yeah.

Judith Mueller 19:59

how are you solving for that in Papaya Pad? So walk us through what coagulation actually means inside a menstrual pad, and what is happening physically when blood enters the pad compared to a conventional one

Shagun 20:11

Yeah. Blood has, a lot of proteins, a lot of cells, a lot of clumpy bits, which is your endometrial tissue or mucus layers. And all of these cells have like a little bit of a negative charge on them So meaning what we're doing is we're not phys-- like I'm not doing the same clotting cascade that happens when you get cut. That's biological and that's way too complicated for a pad. What I'm doing is a physical clot. I am giving it enough like these long chains of like organic molecules which have dangling positive charges on them. So what is happening is the cells with the slight negative charge or proteins with a slight negative charge come in and tangle with it. And so I'm basically making an entangled knot, a physical clot, because it's just all getting clumped up together. Now, there's still some obviously some liquid even in that, like there's still water in blood. So the surrounding pad needs to take care of that. Meanwhile, the main like cells get trapped in one place. the idea. So you don't swell typically like a balloon. You basically entrap by just meshing with the organic molecules of basically cells and proteins and all of the soup of things in blood, like the big bits.

Judith Mueller 21:42

So does that mean you're using the fact that there are big bits as it were in blood

Shagun 21:48

Yeah. Yes, absolutely, right? Like we're using that and we're like the hierar- like I explained, like the top sheet ADL core and back sheet. What we're doing is top sheet ADL pretty much the same functions, but then the core will have a differentiated one so that one layer of the core d- deals with the co-coagulation, and then the other deals with like residual fluid that needs to get absorbed in the more traditional fashion.

Judith Mueller 22:14

Are there currently coagulants in conventional pads?

Shagun 22:19

No, to the-- So, okay not to the best of my knowledge. It's mostly super absorbent polymer, which is a polyacrylate is the chemical name, basically a chain of carbon and hydrogen with a, with an end of a sodium acrylate group, essentially. And what it does is it the network of it, like literally swells up like a balloon. So you have like water in the middle. And the problem is that it when you have high salt concentration in that water, it the sodium, which is in the sodium polyacrylate, does not do well with that. So you basically have lower swelling. This is like a, you

Judith Mueller 23:08

So it's competing in the way that, for example, when you have a lot of sodium intake in the body, like we- you eat a lot of salt, you eat a lot of sodium,

Shagun 23:15

Kind

Judith Mueller 23:15

that usually gives you water retention, right? Because the sodium retains it. But if you also have sodium, say, on the outside of the pad, the, I guess, osmotic, um, whatever the word is

Shagun 23:26

the ionic gradient matters for s- for SAP, sodium polyacrylate. people are working on more resistant to ionic gradient sodium polyacrylades, but like any run-of-the-mill pad is probably going to have the basic SAP. And, the easiest tell is you buy whatever pad, and you just put some water on it, and you'll see like crazy swelling. Like way crazy. So that, that, that's basically the SAP talking in the pad.

Judith Mueller 23:55

Interesting

Shagun 23:57

to replace it with coagulant or with other ways of doing this because SAP over the years, sodium polyacrylate, has been made so cheap to be made so mass-produced, and it's just hard. So it's once you have an idea on how to do this, and then it gets industrialized to this scale that the cost starts becoming, so cheap, then there is an even bigger sort of inertia in the industry moving to a different way, which might be maybe better for the user. But how much better? is there like enough pu- is there enough pull from the user for something like that for it to even get industrialized to that point? So there's this whole... Y- yeah, there's a, it's a cycle. W- what

Judith Mueller 24:50

And it's also,

Shagun 24:51

Yeah.

Judith Mueller 24:52

it's a critical mass problem, right? If you say users are resistant to change, so even for good product, you're struggling to get mass adoption, therefore it's als- again, it's demand and supply, right? If the demand is there, supply will increase. But if demand doesn't know it should be demanding because it's, it's a better product, et cetera, that doesn't happen. Okay. So let's have a look at the coagulant. So you're using a naturally occurring bio coagulant. Without revealing your precise formulation, can you tell us what category of material it is, how it interacts with blood at a physical or biochemical level, perhaps?

Shagun 25:25

Yeah, so the physical chemical level with the, entangling I was explaining. Blood has a bunch of negatively charged particles and it is essentially getting entangled with the positive dangly bits of the clotting agent that I use. It is naturally derived. It is a long chain sugar, like it's type of a sugar almost. That's like the closest classification and yeah, it's com- like you could eat it. Like it's completely degradable and biocompatible. It has a like-- so there's historical uses in industry for within body like even like surgery and stuff. So it's, it has like fairly big, body of literature around how compatibility with body-

Judith Mueller 26:12

And how did you identify this material, this particular naturally occurring bio-collagen? It was

Shagun 26:18

yeah, so I was basically buying stuff off of Amazon that I thought could even remotely work as either an absorbent like starting all the way from cornstarch, right? Because cornstarch is a thickener, like anyone who's made any kind of gelatin any-- I was playing with everything. And a lot of these things are kitchen ingredients essentially, that you can so easily buy off of Amazon just to get an idea of what-- how does it do with blood? So it started there, and, I tried a b- there's not that many once you just classify all of the things that you could potentially use as a broad sweep, and you go from there essentially. So I tried it, it worked, but obviously it needed like a lot of tweaking and tuning and figuring it out. And was basically using a cup, then taking the-- like having a row of different things that I wanted to test, and then like pouring from the menstrual cup a little bit of blood in each of it, and then looking at what happened. That's basically how the first pass weeding was going on.

Judith Mueller 27:26

So every month you say you've gotta have five new versions, iterations ready, test them and see what happens, and just be very quick about it.

Judith Mueller - v4 27:33

Next time, we get into what's actually in the pad and it's not pretty. Up to ninety per cent plastic. Fragrances that may make odour worse, not better. And a question I couldn't stop thinking about afterwards: how does a microplastic get from a pad into your tissue in the first place? We also dig into the greenwashing in this space what "biodegradable" really means when you read the small print. That's all coming in Part 2. Thank you for joining me on this transformative journey. Your presence in this community is truly valued. Now, you may not realize it, but your words hold in men's power. They have the ability to reach others. You may benefit greatly from the wisdom shared here. If you found value in what you had, I kindly ask you to take a moment to subscribe to Bio Hacking Eve. Leave a glow and review on your preferred podcast platform and share bio hacking Eve with your friends and family. Your support helps spread the message of health optimization for women far and white. Lastly, I want to express my gratitude to you for investing in yourself. By prioritizing your wellbeing, new service, and inspiration to others. I'm eagerly looking forward to bringing you many more exciting episodes, and thank you for being a vital part of our community. Live long and prosper, my friend. The Biohacking Eve Health Optimization for Women Podcast is for general informational purposes only, and does not constitute the practice of medicine, nursing, or other professional healthcare services. Including the given of medical advice and no doctor patient relationship is formed. The use of information on this podcast or materials linked from this podcast is at the user's own risk. The content of this podcast is not intended to be substituted for professional medical advice, diagnosis, or treatment. Users should not disregard or delay obtaining medical advice for any medical condition they may have and should seek the assistance of the healthcare professionals for any such conditions. In addition, the information on this podcast does not constitute investment or financial advice.