A single drop of sweat can reveal these 7 things about your health
Constantly wiping sweat from our brows isn't anyone's idea of a summer highlight. But the warm-weather annoyance and exercise byproduct could offer a goldmine of data about your body. A new device designed by North Carolina State University (NCSU) engineers has the potential to transform this sun-induced saline solution into a powerful diagnostic tool for everything from dehydration to cystic fibrosis.
Using a low-powered, paper-based design, a team of engineers has created a wearable device designed to continuously analyze the biological make-up of a person's sweat for 10-days at a time. While similar devices stop working after becoming too saturated with sweat, the plant-like capillary action of this device wicks excessive moisture from it and allows it to operate continuously.
Because this method also leaves behind tree-ring-like salt deposits on the device, the authors say it can be used to determine the health history of a user as well.
Far more than just a sticky nuisance, human sweat contains important biochemical information about invisible health processes taking place inside the body, such as evidence of cystic fibrosis in young children, a genetic lung disease that affects 30,000 people worldwide. Chemicals in your sweat can also reveal to doctors if you're dehydrated, intoxicated, or have taken too much of a medication.
Previous methods for conducting these and other sweat-based analyses have been either too expensive or too inefficient for continuous monitoring.
Sweat offers a goldmine of data. Finding it could get a whole lot cheaper.
In a new study published Tuesday in the journal Biomicrofluidics, a team of biomolecular engineers describes how their paper-based design differs from previous, more expensive models.
"The monitoring of human health and well-being with the use of wearables is considered critical in the next generation of biomedical devices," write the authors. "[But] most existing paper-based devices are designed for one-time use only, functioning under relatively intense capillary flow into the paper, which ceases upon saturation... [Our approach] can function as a key part of a platform for long-term sweat sampling and biomarker monitoring."
If you've ever accidentally spilled an entire glass of liquid across a table, then you'll likely know the absorbent action of paper products (like the paper towels you probably used to control the mess.) This instant absorption of liquid by the paper towel is similar to how plants draw liquid from the soil through their stems and is the same approach the team used to wick away moisture from their paper-based device.
This meant the device could quickly evaporate excess moisture from the sweat while densely packing the remaining salt crystals for further analysis. When testing this device on a non-human sweat model, the researchers found that it was able to continuously operate for 10-days or more without becoming oversaturated by sweat.
This small, paper-based sweat analysis device evaporates excess moisture from the sweat to store the biomarker-containing salt for analysis.
Biomicrofluidics
Orlin Velev, a lead researcher on the study and professor of chemical and biomolecular engineering at NCSU, tells Inverse that this model sweat, like many natural fluids in the human body, was made to be incredibly salty and contain trace metabolites like lactate and cortisol that can be indicators of different health conditions such as dehydration or hypertension.
"You can recover a long-term record of what has been present in the sweat."
In a statement, Velev said the team was surprised by how well this simple model worked in practice.
"We expected that the flow of the model sweat will be suppressed by the deposition of a salt layer inside the drying pad," Velev said. "By following the flow of model sweat, we found, quite surprisingly, that such a simple paper construct can achieve continuous sweat pumping and disposal for very long periods."
Piles of leftover salt from the evaporation process created time-stamped data of when the body was excreting different biomarkers.
Orlin D. Velev and co-authors, NC State University
The team also found that these densely packed, tree-ring-like, piles of salt leftover from the evaporated sweat could be used to timestamp different biomarkers from the users' body. This could preserve the biomarkers for future analysis, the authors explain.
"Everything the device would collect is deposited on the evaporation pad and embedded in the salt layer," Velev tells Inverse. "[You can] recover a long-term record of what has been present in the sweat."
This can be particularly useful in scenarios such as drug monitoring, says Velev, where a doctor may need to know how a person is metabolizing their medication and what concentration they've taken over time.
Going forward, Velev says the research hopes to soon continue the human trials it began before Covid-19 to explore how this device operates when faced with different types of sweat flow. Velev tells Inverse that the model represented "non-active" sweating, or the amount of sweat collected at rest, but future human trials would evaluate sweat before, during, and after exercise. Velev tells Inverse the team is also looking to collaborate with colleagues in other departments to incorporate electronic sensors into the device.
"We're very interested in working with colleagues in interfacing this device with electronic sensing," says Velev. "Our device will be a component of future devices that are kind of the Holy Grail in this area, where you have an electronic wearable that is going to detect your health status long term."
Abstract: We construct and investigate paper-based microfluidic devices, which model long-term fluid harvesting, transport, sensing and analysis in new wearables for sweat analysis. Such devices can continuously wick fluid mimicking sweat and dispose of it on evaporation pads. We characterize and analyze how the action of capillarity and evaporation can cooperatively be used to transport and process sweat mimics containing dissolved salts and model analytes. The results point out that non-invasive osmotic extraction combined with paper microfluidics and evaporative disposal can enable sweat collection and monitoring for durations longer than 10 days. We model the fluid flow in the new capillary-evaporative devices and identify the parameters enabling their long-term operation. We show that the transport rates are sufficiently large to handle natural sweat rates, although we envision that such handling can be interfaced with osmotic harvesting of sweat, a concept that we demonstrated recently. Finally, we illustrate that the salt film deposited at the evaporation pad would eventually lead to cessation of the process, but at the same time will preserve a record of analytes that may be used for long-term biomarker monitoring in sweat. These principles can be implemented in future platforms for wearable skin-interfacing assays or electronic biomarker monitors.
Biker Dad Performs on Stage With His Sick Daughter at School – The Next Day, His Motorcycle Club Shows up at His House
A few months after my cancer diagnosis brought my distant father back into my life, I woke up to the terrifying sound of dozens of motorcycles outside our house. When my mom rushed me downstairs, I had no idea why an entire biker club was waiting for us.
My name is Emily, and I was 13 years old when cancer changed everything.
Before my diagnosis, my dad and I lived in the same house, but sometimes it felt like we lived in different worlds.
He wasn't mean.
He wasn't the kind of father who yelled or forgot my existence.
He just always seemed busy with something else.
If he wasn't working, he was with his motorcycle club.
Their jackets, their bikes, their road trips, their weekend rides. That was his whole world.
School events, parent meetings, birthdays, and dance recitals usually came second.
I used to watch other kids run into their dads' arms after performances while my mom sat alone in the audience, saving the empty seat beside her.
Whenever I asked where Dad was, there was always an explanation.
"He had work."
"He already promised the club he'd help."
"He'll make it up to you later."
Later rarely came.
After a while, I stopped asking.
Then, a few months ago, my family found out I had cancer.
I still remember the hospital room.
The doctor spoke gently, but I barely heard anything after the word itself.
Cancer.
The room seemed to shrink around me.
My mom squeezed my hand so tightly it hurt.
When I looked at Dad, he looked different.
For once, there was nowhere else he'd rather be.
The day we got my diagnosis, it felt like somebody pressed a reset button on my dad's life.
Suddenly, he was everywhere.
He drove me to appointments.
He sat beside me during treatments.
He brought me snacks when I felt sick.
When I couldn't sleep, he stayed awake with me and watched old movies.
When I was scared, he listened.
Really listened.
Not while checking his phone.
Not while thinking about somewhere else.
Just listened.
For the first time in my life, I felt like I really had my dad.
One evening, after a treatment session that left me exhausted, we sat on the couch together watching a comedy.
I laughed so hard that my stomach hurt.
Dad laughed too.
Then he looked at me and said quietly, "I've missed too much."
I looked over.
"What do you mean?"
He rubbed the back of his neck.
"Your life."
The sadness in his voice surprised me.
"You didn't miss all of it," I said.
He smiled sadly.
"Enough of it."
I didn't know what to say.
So I leaned against his shoulder, and we finished the movie together.
A few weeks later, my school announced a Father's Day performance.
Every student could participate with their dad or another family member.
Most kids were doing songs, skits, or sports demonstrations.
I had a small ballet routine planned.
I almost signed up to perform alone.
Then an idea popped into my head.
Before I could talk myself out of it, I asked, "Would you do it with me?"
Dad nearly choked on his coffee.
"Ballet?"
I laughed.
"Yeah."
He stared at me.
I waited for him to say no.
Instead, he asked, "Do I get lessons first?"
I blinked.
"Is that a yes?"
He grinned.
"It's a yes."
I screamed so loudly that my mom dropped a spoon in the kitchen.
The next few weeks were hilarious.
Dad was terrible.
Absolutely terrible.
He stepped on my feet.
He mixed up left and right.
He nearly fell over trying to spin.
More than once, we both ended up laughing too hard to continue practicing.
But he never quit.
Not once did he give up.
One afternoon, while we practiced in the school gym, a few parents stopped to watch.
Some smiled.
Others looked confused.
One father actually applauded.
Dad just kept trying.
Even when he looked ridiculous.
Especially when he looked ridiculous.
A few days before the performance, one of his biker friends stopped by our house.
His name was Rick.
The two of them stood in the driveway talking while I sat on the porch.
Rick shook his head when Dad mentioned the performance.
"You're seriously going on stage doing ballet?" he asked.
Dad nodded.
"You aren't afraid of what the guys are going to think?" Rick asked.
Dad just shrugged.
"I don't care."
Rick stared at him.
"Seriously?"
Dad glanced toward me.
His expression softened.
"Seriously."
For some reason, hearing that made my chest feel warm.
Maybe because I knew how much the club meant to him.
Maybe because, for once, he was choosing me.
The Father's Day performance arrived sooner than expected.
I was nervous all morning.
My hands wouldn't stop shaking.
Dad looked nervous too, though he tried to hide it.
Backstage, he adjusted the costume shirt my ballet teacher had convinced him to wear.
"I look ridiculous," he muttered.
"You do," I agreed.
He laughed.
"Thanks for the support."
"You're welcome."
The auditorium was packed.
Parents, teachers, students, grandparents.
Every seat seemed full.
When our turn came, I thought Dad might back out.
Instead, he squeezed my shoulder.
"Ready?"
I nodded.
We walked onto the stage together.
The music started.
For the next few minutes, Dad did his best.
It wasn't graceful.
It wasn't elegant.
It definitely wasn't professional.
The entire school watched as this huge biker covered in tattoos awkwardly tried to follow my ballet steps.
Everybody laughed, but not in a mean way.
Even I couldn't stop laughing.
At one point, he spun the wrong direction and almost crashed into a curtain.
The audience erupted.
Dad laughed too.
By the time the routine ended, everyone was clapping.
Some people were standing.
I couldn't stop smiling.
It was the happiest I'd been in months.
That night, I fell asleep still thinking about it.
I thought about how my dad and I danced up on stage like we were the only two people in the world.
I thought about how my mom watched us the entire time with tears in her eyes.
I thought about how the entire auditorium erupted in cheers after we finished our performance.
For once, I forgot about hospitals.
I forgot about treatments.
I forgot about cancer.
The following morning, I woke up to the sound of motorcycles.
Not one.
Not two.
Dozens.
The roar was so loud it shook the windows.
At first, I thought I was dreaming.
Then the noise grew louder.
And louder.
I sat up in bed.
My heart started pounding.
I rolled over and looked outside.
My stomach dropped.
The street in front of our house was packed with bikers.
An entire crowd had arrived.
Rows and rows of motorcycles stretched down the block.
Some riders stood beside their bikes.
Others were staring at our house.
Nobody seemed to be leaving.
I couldn't understand what I was seeing.
Had something happened?
Was someone in trouble?
A minute later, my mom rushed into my room.
Her face looked strange.
Not scared.
Not angry.
Just emotional.
"Emily," she said quietly. "You and your dad are being called outside. Right now."
I slipped on my slippers and headed downstairs.
As Dad opened the front door, the roar of the motorcycles suddenly stopped.
Every rider turned toward us.
The man standing at the front of the crowd took a step forward.
I recognized him immediately.
Rick.
The same biker who had laughed when he heard Dad was going to perform ballet with me.
For a second, nobody spoke.
The entire street seemed frozen.
Rows of motorcycles stretched in every direction. Men in leather jackets and sunglasses, with tattoos and beards.
It looked like something out of a movie.
I suddenly felt very small standing on our front porch.
Dad looked just as confused as I felt.
"Rick?" he called. "What's going on?"
Rick scratched his beard and glanced around at the crowd.
Then he smiled.
"You really thought we'd let you have all the attention after that performance?"
A wave of laughter rolled through the bikers.
Dad frowned.
"What are you talking about?"
Rick shook his head.
"We all saw the video."
My stomach tightened.
The video.
Several parents had recorded our Father's Day performance. By the time we got home, clips of it were already being shared online.
Dad groaned.
"Oh no."
The bikers laughed again.
I noticed they didn't look angry or disappointed.
They looked amused.
Some even looked emotional.
Rick pointed at Dad.
"Relax. The dancing wasn't what people were talking about."
Dad folded his arms.
"Then what was?"
Rick glanced at me.
"The look on Emily's face."
The smile disappeared from Dad's face.
So did mine.
The crowd grew quiet.
Rick continued.
"We saw a father showing up for his daughter."
Several bikers nodded.
One of them stepped forward.
His gray beard reached almost to his chest.
"I've got three daughters," he said. "They're all grown now."
He looked down for a moment.
"I missed a lot."
Nobody laughed.
Nobody joked.
Another biker spoke up.
"I missed softball games."
A third shrugged.
"I missed dance recitals."
A fourth added quietly, "I missed more birthdays than I care to admit."
The silence that followed felt heavy.
Dad looked around at them, and his expression softened.
Rick shoved his hands into his pockets.
"A lot of us watched that video and started thinking."
"About what?" Dad asked.
"About what really matters."
Nobody spoke for several seconds.
Then Rick smiled again.
"So we decided to do something."
He waved toward one of the motorcycles.
A woman climbed off the back and walked forward, carrying a large wooden box.
My mom gasped.
Dad stared.
The woman handed the box to Rick.
Rick opened it.
Inside were dozens of envelopes.
My dad blinked.
"What is this?"
Rick looked uncomfortable for the first time all morning.
"We passed the hat around."
Dad stared.
Rick shrugged.
"Actually, we passed it around a lot."
A few bikers chuckled.
Another called out, "And Rick wouldn't stop asking people."
"Shush," Rick shot back.
The crowd laughed.
Then he looked at Dad again.
"We know treatments aren't cheap."
My mom covered her mouth.
I felt my chest tighten.
Rick continued.
"We know you've been missing work."
"We know things have been hard."
Dad looked speechless.
For perhaps the first time in my life, I couldn't think of a single thing to say either.
Rick handed him the box.
"Open it."
Dad slowly lifted one of the envelopes.
Then another.
And another.
Each contained money.
Some held checks.
Others contained handwritten notes.
My mom started crying.
Dad swallowed hard.
"Guys..."
His voice cracked.
He stopped talking.
One biker grinned.
"See? We finally found a way to shut him up."
The crowd erupted with laughter.
Even Dad laughed, though tears were running down his face.
Rick faced me.
"This wasn't only for your dad."
I blinked.
"What?"
A grin spread across his face.
Then he snapped his fingers.
Another biker stepped forward, carrying something bright pink.
At first, I couldn't tell what it was.
Then I realized.
A motorcycle helmet.
Pink with white stripes.
My favorite color.
I stared.
"What is that?"
Rick held it out toward me.
"Yours."
My eyes widened.
"Mine?"
Every biker around him started smiling.
I carefully took the helmet.
The surface was covered in signatures.
Dozens of them.
Messages filled every space.
"Keep fighting."
"You've got this."
"Your whole crew is behind you."
"Strongest kid we know."
My vision blurred.
I realized I was crying.
Again.
I seemed to be doing that a lot lately.
One of the bikers pointed toward the signatures.
"Read the back."
I turned the helmet over.
Across the bottom, written in thick silver marker, were the words:
"HONORARY ROAD CAPTAIN"
I looked up.
The entire crowd was watching me.
Rick folded his arms.
"So, Emily."
I swallowed.
"Yeah?"
He smiled.
"Want to lead today's ride?"
I stared at him.
"Me?"
The bikers laughed.
"You."
I looked at Dad.
He was smiling through tears.
"What do you think, kiddo?" he asked.
I couldn't stop smiling.
"Really?"
"Really," Rick said.
A few minutes later, Dad helped me put on the pink helmet.
It was a little big.
I didn't care.
I felt like the coolest person in the world.
Then he lifted me onto his motorcycle.
The crowd cheered.
The sound startled me.
Not because it was loud.
Because it was for me.
Dad climbed on in front.
I wrapped my arms around him.
The motorcycles around us began moving.
Slowly.
Carefully.
We rolled down the street.
Then something amazing happened.
The other bikers didn't pass us.
They didn't surround us randomly.
They formed around us.
Two rode ahead.
Several stayed behind.
Others positioned themselves along both sides.
Like an escort.
Like a parade.
Like they were protecting somebody important.
For the first time, I realized they were protecting me.
People came out of their houses to watch.
Neighbors waved from porches.
Children pointed excitedly.
A few parents from school stood on the sidewalk, smiling when they recognized Dad and me from the performance video.
One woman pressed her hand to her chest.
Another wiped her eyes.
Everybody smiled.
Everybody waved.
And for the first time since my diagnosis, nobody was looking at me with pity.
Nobody was looking at me like I was sick.
They were looking at me like I was special.
Like I was strong.
Like I belonged.
The ride wasn't long.
Just around the neighborhood.
But I wished it could last forever.
When we finally returned home, the motorcycles lined both sides of the street.
Dad helped me climb off the bike.
The crowd applauded.
Neighbors clapped from their lawns.
Someone from across the street shouted, "Go, Emily!"
My face turned red, but I couldn't stop smiling.
Rick walked over.
"Not bad for your first ride."
I laughed.
"I think I liked it."
"You think?"
"I loved it."
He grinned.
"Good answer."
One by one, the bikers started heading back to their motorcycles.
Engines began rumbling to life.
Then more.
Within seconds, dozens of motorcycles were roaring again.
The sound was enormous.
One by one, riders saluted me.
Some waved.
Others pointed at the pink helmet.
A few shouted good luck.
The noise echoed across the neighborhood.
But now it didn't feel scary.
It felt supportive.
I looked at Dad.
He wrapped an arm around my shoulders.
I leaned against him.
For a moment, neither of us said anything.
I realized I wasn't facing cancer alone.
Not just with Mom and Dad.
With an entire community standing behind me.
As the motorcycles disappeared down the street, I watched until the last one was gone.
Then I looked up at Dad.
He smiled.
And I smiled back.
A few months earlier, I thought my dad's motorcycle club had taken him away from me.
Standing there that morning, surrounded by dozens of roaring engines and people cheering my name, I realized they had helped bring him back.
But here is the real question: How often do we tell ourselves there's always more time, only to realize that the moments we remember most are the ones we almost missed?
If this story touched your heart, here's another one you might like: A man believed his grandchildren loved him, even though they had barely visited him in 15 years. After discovering his family had been deceiving him for years just to keep receiving his money, he made a shocking decision about his will that left them speechless.
