Science AMA Series: I'm Hugh Herr, professor and co-director of the Center for Extreme Bionics at the MIT Media Lab. At 17 I lost both my legs during a blizzard while rock climbing. Now I design bionic limbs that let us transcend disability and augment the human condition. AMA!



Forgive me for being starstruck, but you're one of my personal heroes. I love the way you describe humanity's relationship with technology, and your thoughts on how a human can never be broken really resonate with me. I hope you'll forgive my long list of questions.

  1. I noticed in some media that you were working with osseointegrated sockets. How is that going? How are you mitigating mechanical forces walking up the implant and snapping at the osseus tissue? Flexible materials perhaps? Interfacing tendons with the implants?

  2. When building bionics, you're literally building new body parts for people. How do we ensure those people truly become symbiotic with their technology, instead of becoming burdened by it? Do your bionics come with well documented interfaces and schematics? Do the end users get access to these things? Do you encourage the users to learn about and modify their bionics?

  3. As far as I know, the primary school of thought on reducing the risk of surgery is to reduce the invasiveness. Do you know of any efforts to do the opposite, and gain so much control over the system and procedure that extremely radical surgeries become effectively risk-free?

  4. In one interview, you mentioned that other climbers threatened to amputate their legs but never did. Is this because they lacked surgial access, or because they weren't serious? How would one get surgical access?

  5. You've built your own awesome bionics - If this isn't too personal, I'd like to know what, if any, what future enhancements you have planned for yourself?

  6. How have the experiments growing nerves into channels gone?

  7. Have you considered synthesizing proprioception data in a prosthesis using IMUs, then feeding that to the brain through haptics like the VEST or direct nerve stimulation? I've wanted to try this but lack all of the means to do so.

  8. How goes the fight against phantom pain? I've hypothesized that providing the brain with real signals via the nerves might resolve this, and the recent work with a woman named Melissa Loomis, I think, involving the DEKA arm / APL hand combination seems to suppor this. Your thoughts?

  9. Has anyone tried using psychedelics to help in the process of getting pilots acquainted with their bionics? If they've spent their entire life building procedural memory for "flex this way, arm responds this way", it might make sense to blow some of that away when asking them to learn a new method.

  10. I'm an autodidact currently doing programming and UI design for VR/AR. One day I'd like to work in human augmentation. Do you have any advice for me?


These are all excellent questions - I wish I could answer them all. I want to address question 4, though: one can ask a surgeon to amputate their limb – however today surgeons won’t agree unless there’s a medical reason to do so. Such a surgery has to have an expected outcome that will improve the QOL for the patient. If you don’t have such a reason, I don’t believe a surgeon would agree to such a surgery.

How well do current bionics wear with time? In other words, how much maintenance and replacement do current technologies require, and how do you see this changing in the future?

Also, about how long would you estimate it will take for hand-replacing bionics to roughly match normal dexterity and responsiveness?

Thanks for doing this AMA!


Excellent question! The performance of biological systems is of course phenomenal, one characteristic of animals is extraordinary robustness or durability. Sometimes we go 80 years or more without maintenance or repair. Engineered machines go a very short time before needing repair – for example the bionic limbs that I invented and am wearing right now (BiOMs) are designed to work and be functional for only 5 years. To get a machine to emulate a biological body part and to go for more than 5 years is an extremely hard technological challenge. To truly emulate biological function, biological durability would require that the machine repairs itself. Before we have this, our machines will be very limited in their capacity.

Hi Dr Herr, I was hit by a car while riding my motorcycle and the end result is a left ankle and foot full of scar tissue and arthritis, with the prognosis from multiple experts that I will need an ankle fusion in ten years (I'm thirty now). This will mean I can't do long hikes which was my passion before the accident.

Walking is painful now just due to all of the tendons bound up with scar tissue and changed foot geometry.

So what I was wondering was whether it would be A) possible, and B) worth it, to chop my left leg off at the shin and have a bionic ankle/foot? This is a serious question, because I've already lost my previously active lifestyle due to my injury, and I'd love to have it back one day.

Thanks in advance.


It is becoming more and more common for people to make the decision to have their limb amputated. Cases such as yours where a biological limb no longer is functional – doctors will often support this decision, if in their professional view the patient’s QOL will improve as the result of the amputation. Without knowing the specifics of your case, I cannot make a recommendation, I would urge you to seek counsel from a physician before making such a critically important decision.

Hello, if you have ever seen or played the game Deus Ex, where humans augment themselves with bionic limbs, do you think humanity will ever get to that point where prosthetic limbs are not so much a replacement for what's lost, but rather an upgrade of one's body? And do you think it would be ethical?


Yes, I do believe that modern technology will ultimately enable human augmentation. Recently my laboratory in 2014 developed the first leg exoskeleton to augment human walking. So human augmentation is already being demonstrated in the world! Is it ethical? I personally accept the notion of human augmentation, as long as it doesn’t mitigate individual freedoms. There are some forms of augmentation that would negatively impact us, and have the potential of collapsing human diversity. For these types of augmentation technologies, I am passionately opposed.

Hey, im currently a high school student in Australia and my dream is to develop bionic limbs and prosthetics like you have done. What university/career advice could you give to help me make this happen?


Hey Matt, thank you for your question. The field of bionics is quite intellectually diverse, requiring a broad set of topics to study. Relevant topics are robotics, machine learning, tissue engineering, biocompatibility, and of course human biology. My undergraduate degree was in straight physics, and I also have graduate degrees in mechanical engineering and biophysics. I would strongly recommend an undergraduate degree in physics because, through such a degree, one has an opportunity to learn the fundamental principles of nature. Such a fundamental education then enables one to study a diverse set of topics in graduate school that are relevant to bionics.

Hi Hugh, how are you?

First of all, I would like to thank you for doing this AMA.

I really appreciate the work you do regarding bionic limb technology. However, most replacement limbs given to the majority of people are very low tech, due to the high cost of technologically advanced models. How do you propose your technology is adapted and used by more people around the world? Edit: Spelling


Several of my research group’s bionic technologies have been commercialized, and have price points that are fairly standard or comparable to prices of other high tech limbs. We are working very hard to get Medicare and Medicaid Services within the U.S. to recognize bionics and to offer pricing and coverage. I’m hopeful that we will succeed in getting reimbursement for such limbs, enabling patients that so badly need high functioning bionics to have access.

What's the next step for this technology? Is it likely that it will be used not just to fix disabilities but to actually enhance a functioning member?


I believe the next step in bionics is to increase the mergence of the built design world with biological tissues, electrically, mechanically, and chemically. The fundamental science and technology that will enable this mergence will not only end many disabilities, but will also serve as the same foundation to enable human augmentation, extending capability beyond innate physiological levels.

Hello Prof. Herr,

Thank you for doing this AMA. I want to be honest with you - I teared up during your TED-Talk when you said:

"In 3.5 seconds these criminals and cowards [of the Boston terrorist attacks] took Adrian off the dancefloor. In 200 days we took her back. We will not be intimidated or brought down, diminished, conquered or stopped by acts of violence."

So my question to you is: Since conventional prosthetics will remain cheaper than electronic ones for a foreseeable future, how can we further propagate these new technologies so that they can get covered by health insurances?

I mean at the moment all those inventions are all good looking but unfortunately far from being universally used, bought or funded. How can we change that?


I often get the comment from people that bionics is all very well, but how could anyone possibly afford bionics? And my answer is – how could we ever choose not to pursue bionics as a society? True bionics emulates or restores biological function, and when technology truly achieves such emulation, typically the overall healthcare cost to treat a patient across their lifetime decreases.

For example, if a bionic limb is available that eliminates limping and completely restores normalized walking capability, secondary conditions that are typically attributed to leg amputation (e.g. joint osteoarthritis) are eliminated. Because of inadequate technology that exists today, after limb amputation while using such prosthetic technology people limp and experience pain when they walk. Limping causes secondary conditions that balloon healthcare costs, and are, in fact, the dominant economic drivers in the treatment of people suffering from limb amputation. With advanced technology that truly emulates biological capability, secondary conditions can be eliminated, along with all the associated costs. Thus, bionics is a win-win for both the user and the payer.

Hello Hugh, I'm a materials chemistry Ph.D. student, and I'm interested in learning what opportunities there are for new materials in the field of prosthetic technology.

  1. What types of materials are needed in this area, i.e. what properties would the structural and active parts of an artificial limb possess in an ideal future world?

  2. Is there a type of smart material (a material that can adapt its properties to its environment) you can envision that could be useful right now?


Improvements in materials is of course critically important to the field of bionics. One example that comes to mind is osseointegration. Today osseointegration involves a titanium shaft passing through the skin membrane and into the residual bone. The osseo implant serves as a mechanical mounting surface for an external bionic limb, such that when a person walks, for example, the loads of walking are transferred directly to the person’s skeleton. The osseo implant can also be made to have a hollow core, enabling the passage of wires from muscles/nerves inside the body through the osseo conduit to an external bionic limb. A critical challenge of an osseo implant has to do with its material properties. With today’s osseo implant design, it is recommended that the user not take part in athletic activities, for fear that the high stresses on the osseo implant may cause damage. In the field of bionics, what we desire is a novel biocompatible implant with exceptionally high material strength and fatigue life such that the user could, once again, pursue their athletic endeavors.

First of all thanks a lot for taking the time to do this AMA (and for improving the quality of life of many patients).

I have a few questions for you:

  • How much room for improvement do you think there is left in bionic legs ? I remember that in your last TED talk, you mentioned that the current bottleneck is in the link between the prosthetics and the human body.
  • Are the methods used for leg bionics usable for other parts of the body ? I guess that the challenges are much different (much more articulations).
  • What is the current state of the art in sensory feedback with leg prosthetics, I saw this neat thesis on arm ones from the neural interfaces group at the Imperial College of London.
  • By how much do you think the cost of prothetics could be lowered ?
  • Is there still a lot of work in order to improve the quality of life of patients ?
  • Alex and Mina what is it that you work on every day on for your PhD (besides answering AMA on reddit) ?
  • Might seem a bit off topic (and selfish), but what would you look for in a grad student at your lab (I would love to apply for that next year) ? Is a Masters degree in Computer Engineering enough ? Would a second master in neurobiology be useful ? What about professional experience ? If I had a year to spend what would you recommend spending it on (I already read most of the papers published by your group, enrolled in a neurobiology masters and should work at a French NIH for a year).

Once again thanks a lot for your time.


Great question! Our lab is incredibly diverse in what Dr. Herr lets us pursue – socket design, bionic motors, you name it. I’ve worked with Team Neural over the summer, where we’re currently testing a neural interface for limbs so that patients can feel their artificial feet. It’s a combination of design work (AutoCAD), coding and electrophysiology, and because it’s all design/troubleshooting, you get to spend most of your day critically thinking, which I love. -Alex

Hello gamazeps, I'm actually an undergraduate researcher in Biomech. I've worked on our ankle exoskeleton and peripheral nerve projects, focusing on device design and data acquisition/analysis. A day usually involves working with my mentors on experiments or individually working on elements of a larger project. -Mina

I heard your story on the radio. How tall have made yourself with the fake legs? Is it hard to balance when the legs get extended that much?


Years ago, when I was climbing actively, I on occasion made my height very very excessive. There was one occasion where I was 3m high! And yes indeed, it is very hard to balance (and a large distance to fall!).

Hello Professor Herr,

You are a beacon of hope for all the disabled people around the world. Thank you for your research and for this AMA.

I have a few Questions for you.

1) How do you plan to improve your technology so as to make it affordable to the masses?

2) When I saw the word "neural interfaces", Prof Ed Boyden immediately came into my mind, If you don't mind me asking, Does your group collaborate with Prof Boyden's group?

3) Can you 3D print, your products using current 3D printing technologies?

4) (I see a Deus Ex comments here), basically asking for the ethical conundrum posed by this technology. what is your view on it?


To answer question 2, yes! My group does in fact collaborate with Ed Boyden’s. Boyden and I codirect the MIT Center for Extreme Bionics and we’re working very closely together on fundraising as well as scientific projects.

How did you overcome losing your legs at 17? Im sure it was a lot of struggle in the beginning. Can you tell us how your feelings about the tragedy changed over the years?


After my mountain climbing accident, I was extremely angry at myself for having caused the accident, and the death of a rescuer, Albert Dow. Because of Albert’s ultimate sacrifice, I felt it was my duty and obligation to invest my body and mind, and all of my energies, to improving the world in some way. The way that I chose was to improve technology for the disabled. I believe I dealt with my accident by embracing Albert’s legacy and the challenge of eliminating disability through technological innovation. As I walked down that road, I also began to heal.

What is the goal of your current research?

What is the biggest missconception or hype regardingi prosthetics?


Hollywood has given us the impression that synthetic robots and bionic appendages will be awkward, unnatural and machine-like. I do not agree with this vision of the future. We can as designers and technologists embed the fundamental nature of humans into the designed world. In the future as we construct, certainly in the realm of bionics – these devices will move like us, will think like us, and will even feel like us. In that future, the distinction between what is biological and what is not, what is human and what is not will be forever blurred.

Hi Professor Herr!

Thank you for taking the time to respond to us. I have two questions.

1) What kind of special concerns or considerations do you take into account (if any) regarding the use of AI and/or bionics for unintended purposes (ex: weaponry)?

2) What is your favorite day hike?


I was raised in the Mennonite religious tradition. Mennonites are devout pacifists. Thus, I would be very upset if technologies that my lab had developed were used for unintended nefarious purposes (e.g. weapons). Every new technology has intended and, unfortunately, unintended purposes. It is critically important that, as a society, we advance legal and social frameworks that promote the development of bionics while at the same time mitigate inappropriate uses of such technology.

And my favorite mountain range in the world is the Italian Alps!

In your professional opinion what is the timeline for bionic arms or legs that will match their biological counterparts in functionality?

Thank for doing this AMA!


To advance a bionic limb that captures the full versatility of its normal biological counterpart, will most likely take on the order of three decades.

How close are we to having bionic limbs that can be powered by energy from the human body?


While it is difficult to give a timeframe, human-powered bionics is certainly achievable. One can imagine extending biological bone using synthetics and attaching biological muscle and ligaments to an artificial skeleton, where the synthetics are in fact internal to the skin envelope.

Hi Hugh

Is anyone in the field considering what kind of phycological effect bionics could have on people? Does the digital nature of cybernetic eyes change the way people relate to the world around them? Could being vastly stronger/faster due to bionics affect a human's empathy? I'm curious how the human mind would adapt to rapid changes brought about by augmentation.


Whenever a bionic intervention is applied to the body, the body certainly adapts and responds to that intervention. How humans will adapt to various types of bionic interventions is largely unknown. You mentioned empathy in your question. Keep in mind that bionics will not only enhance human physicality, but also human cognition and emotional acuity. I have no doubt that one day human empathy will be augmented.

It seems there are two particularly interesting future events relating to research and advancement of bionics:

  • When bionics research leads to the elimination of disability.
  • When members of the general populace begin enhancing themselves with bionic limbs and advanced exoskeletons.

In comparing the time period between now and the first event, versus the time between the first event and the second event - when human augmentation becoming the norm begins to appear realistic for a consumer - do you think the latter of these two developments in humanity will take another century or so after the former to become realized? Or do you think human enhancement is a much more direct following and will reach its full potential within decades of eliminating human disability, or even sooner? Or are they in fact indistinguishable - will the moment we eliminate disability also be the moment we master human augmentation?

In a nutshell, will the day that disability is eliminated be the same day that a person might decide to amputate a fully-functioning limb for the sake of adding a better-functioning bionic limb?


Interesting question. I take from your question that the day that disability ends the bionic appendage would fully encompass the functionality of a biological limb – it would be equal to it. Thus the only rational reason to amputate a fully functioning biological limb in that future world would be to achieve the flexibility of an upgradeable system. Today, every year my own bionic limbs are upgraded, offering me greater functionality. So yes! It may be the case in that future world that a person might want a synthetic version of their limb because they want to achieve the capacity to upgrade in time, and to enable the synthetic part of their body to improve over time.

Additional Assets


This article and its reviews are distributed under the terms of the Creative Commons Attribution 4.0 International License, which permits unrestricted use, distribution, and redistribution in any medium, provided that the original author and source are credited.