The human body is a complex place, and our immune systems are powerful allies.
If you get sick, doctors can often rely on strengthening what’s already inside you.
But sometimes you need an assist: technology that can be put inside the body.
Things like biodevices.
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We’ve all seen a TV show where someone has a heart attack, only to be revived with a quick shock to the chest.
Defibrillators are powerful tools, but by the time a patient needs one, they’re already in a life-or-death situation.
What if it never had to get to that point?
What if there was a way to catch the problem as it started and act more quickly than any human could?
This isn’t science fiction:
millions are walking around right now with exactly that inside their chest, an incredible tool called the implantable cardioverter-defibrillator, or ICD.
It continuously monitors a person’s heartbeat and delivers an electrical pulse to restore a normal rhythm whenever it detects a problem is about to occur.
That’s something a drug, no matter how sophisticated, could never do.
That’s where medical devices, or biodevices, come in.
They serve many roles, from rebuilding lost bodily functions, to managing diseases and helping you live longer.
It’s a broad category, but some of the most important are implantable biodevices, like ICDs and cochlear implants.
A biodevice is implantable if all or part of it is put inside the body for an extended period of time.
They might not be easy to spot, but they’re already in widespread use today.
Around 8% of Americans and 5% of people in developed countries have used an implantable biodevice of some sort – that’s millions and millions of people!
Before they could become so common, engineers had to overcome numerous challenges.
The body’s a complex place, so many biodevices are, too.
They have to coexist with changing temperatures, electrical signals, and chemical reactions in a way that doesn’t disrupt our body’s carefully-balanced systems.
So to design a good biodevice, you need to acquaint yourself with not only the environment of the human body,
but also its functionality, structure, and ongoing processes.
The design process for these devices is similar to anything else you might make as an engineer.
You need a design that doesn’t just work, but one that can be manufactured in a safe and cost-effective way.
But the tolerances can be tiny: a needle that’s a hair too short might not reach where it needs to go.
A joint that’s too large could cause a lifetime of pain.
There are a few things you’ll need to pay special attention to, the first being biocompatibility.
We’ve already talked about biocompatibility in a previous episode – it’s the idea that not every material is at home in a living thing.
Not only do you need to use biomaterials, it’s important to sterilize anything going into the body and you need to account for the stresses that process demands.
One technique recommended by the CDC is dry heat sterilization, which bakes the device at a high heat using moisture-free air.
Baking the device at 160°C for around 2 hours should do the trick, or you can go to 170°C for about an hour if you want to speed things up.
If your biomaterial can’t survive that kind of heat, you’ll need to find a different way to get it clean.
Many biodevices contain tiny computers, so you’ll need to include a battery to keep it running and maybe some wifi to communicate with the outside world.
Engineers call these things power and connectivity.
You don’t want your patients to have to lug around big battery packs or always need to be hooked up to a cord in the wall.
If you don’t think about power and connectivity during the design process,
it can lead to a device that’s too impractical, one that doesn’t work, or one that stops working soon after you implant it.
A great example of this was the first successfully implanted electronic pacemaker back in 1958.
Pacemakers use electrical pulses to help the heart beat more regularly, so it was a big step forward for patients with abnormal heart rhythms.
However, as revolutionary as this was, the first implanted device failed after only three hours,
in part because of electronics that were too bulky and batteries with short, unreliable lives.
Until the advent of more reliable lithium batteries in the 1970s, failures like this were inherent in the design of implantable biodevices.
Not to mention that all that water in the body is pretty bad for electronics, so you need appropriate packaging, too.
The device should be airtight and watertight – what engineers call hermetically sealed.
You might be tempted to encase everything in a metal like titanium, but metal packages don’t just keep out air and water: they also block radio waves.
If your metal device needs to communicate with the outside world, it will need an external antenna, which makes everything more complicated.
A better bet might be to use a ceramic or glass enclosure like you’d find in a smartphone.
Wireless connectivity helps not only with device diagnostics, but also with a patient’s peace of mind.
People want to know their implant is working properly and it’s far more accessible to have stats on a device that patients can take with them,
rather than something that can only be downloaded by the doctor.
Dropping an external antenna also helps make the overall structural design of the system smaller and less invasive.
Remember, at the end of the day, whatever you design is gonna be placed inside a person.
The same goes for your delivery system, or any medical procedure that you need to do to implant the device.
Patients are more likely to recover quickly if you use the least invasive approach practical.
If you can build your device small enough using tools like nanotechnology, in the future doctors may be able to deliver it through a simple injection.
Larger implants might be deliverable through a tiny slit using laparoscopic surgery, which often enables patients to go home the same day.
If your device is too big to go in through a small hole, you might run into another problem: finding enough space inside the body.
If a spot isn’t big enough to fit the whole thing, or it’s simply better for different parts of the device to be in different places,
you can design it so that it’s separated into multiple components.
Take a cochlear implant, for example.
These devices – which can help provide a sense of sound to people who are profoundly deaf or severely hard-of-hearing – are often made up of two main parts:
an external portion that fits behind the ear and one that is surgically placed under the skin.
Even if space wasn’t an issue, it’s much better for something like a microphone to be on the outside so that it can more easily pick up sounds from the environment.
Another option might be to remove part of an organ to make room for your device.
Hip replacements, for instance, replace the damaged parts of the joint with titanium.
Once you take all of this into account – from biocompatibility to delivery systems –
you still need to consider device management and diagnostics from the day you deliver it, to the second it’s removed from the patient.
Basically, you want to keep an eye on your device to make sure it’s working correctly.
This can be rudimentary, like having a patient come into the office to physically get their implant checked out,
to more modern options, like giving a doctor the ability to remotely diagnose any issues.
But what if you didn’t need an external device at all?
That’s the promise of smart tattoos!
Researchers are learning how to put flexible electronic sensors into temporary tattoos that would be able to withstand all the twists and bends of daily life.
These sensors – which are thinner than the hairs on your head –
could monitor the electrical signals produced by the body, allowing a patient to monitor heart conditions.
Or, for those with diabetes, the tattoos could measure blood glucose levels in real time.
The results could appear as a changing color, right there on the skin!
Tiny tech like this is just the beginning.
Devices that use Micro-Electro-Mechanical Systems, or MEMS, are the future for active implantable drug delivery systems.
MEMS enable delivery systems on the micrometer scale, which doesn’t just make things more compact,
but also allows them to accomplish tasks that wouldn’t be possible at the macroscopic level.
You’ve probably had your blood pressure checked by one of those inflatable cuffs that they put around your arm.
That may work for a simple checkup, but measuring someone’s blood pressure in that way isn’t always that easy, especially for people in intensive care.
That’s where MEMS come in!
A new MEMS sensor can monitor blood pressure directly through the IV line,
enabling continuous measurement and removing the need for daily calibration and sterilization.
And soon, with MEMS, the idea of tiny robots inside your body could escape science fiction and make its way into real life!
One day, they might not only deliver drugs, but help repair DNA and even restore sight to the blind.
Once you’ve solved all the problems of getting a biodevice working well inside someone, there’s just one issue left: how do you get it out?
Some patients might need the device for the rest of their lives, but for everyone else, it’s usually a surgical procedure to take it out.
Well, it’s a surgical procedure for now.
Researchers are focused on developing metallic materials made from elements like magnesium, zinc, and iron that are also biodegradable.
These materials could be invaluable in the electronics of a temporary biodevice.
They’d have the same properties of the devices made today, but once their job is done, they would just disappear into the body.
With applications like these, the potential for biodevices is nearly unlimited.
But it’s gonna take the work of dedicated engineers to continue to bring those ideas to life.
So today we talked about biodevices and the part they play in the healthcare world.
We focused on implantable biodevices and all of the challenges that they face,
including biocompatibility, power and connectivity, packaging, structural design, delivery systems, and device management.
Finally, we saw some of the latest research, like smart tattoos, and just what the future of biodevices might hold.
I’ll see you next time, when we’ll talk about genetic engineering.
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Crash Course is a Complexly production and this episode was filmed in the Doctor Cheryl C. Kinney Studio with the help of these wonderful people.
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