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Bioinspiration and biointegration

Zhigang Suo's picture

The nervous system has long been an inspiration for the engineer.  Here is an example in a popular textbook on neuroscience.  When a person steps on a nail, the sensor in his foot sends a signal to his brain, the brain sends a signal to his muscle, and he lifts his foot.  The example illustrates the sensor, actuator and processor in the nervous system.  In developing engineering sensors, actuators and processors, the engineer mimics functions, not the anatomy, of the biological system.  The engineer receives inspiration from many sources:  existing devices, newly available materials, newly available manufacturing methods, a discussion with a colleague, etc.  The biological system serves as one source of inspiration to the engineer just because the biological system exists, and its structure and function are described in the textbooks of anatomy and physiology.  The engineer gets inspired, but does not have to get into the messy business of tissues, cells and molecules.  In recent work, my colleagues and I have been inspired by one fact:  the nervous system transmits electrical signals using ions rather than electrons.  This inspiration has led us to invent high-speed devices using stretchable, transparent, ionic conductors

By contrast, biointegraion requires the integration of engineering devices and biological tissues.  The primary example is prostheses.  In a recent article, the neuroscientist Gregoire Courtine and his colleagues have reviewed the advances, promises and challenges of neuroprosthetics.  In a TED talk, he described his recent achievement in restoring locomotion in rats after paralyzing spinal cord injury using a combination of electrical stimulation, drugs, and training.  This vision of integrating engineering devices and biological tissues has motivated many people.  For some years, the engineer Stephanie Lacour has been developing soft neural implants.  To achieve biointegration, she has little choice but getting into the messy business of tissues, cells and molecules.  The work of John Rogers, Yonggang Huang and their collaborators has highlighted the opportunities in this exciting field, where mechanics and electronics must meet chemistry and biology.

Bioinspiration and biointegration require different mindsets.  They both present opportunities for the engineer for years to come.       

Comments

Teng Li's picture

Thanks, Zhigang, for bringing up an interesing perspective on the different requirements of bioinspiration and biointegration. Further in-depth discussion along this line would be helpful for better understanding the key needs to enable successful bioinspiration, and more importantly, successful biointegration for engineers given our less familiarity with biological systems.

This discussion reminds me some discussions on our recent work on wood-based sodium ion batteries over a dinner with some experimental electrochemists. In this work, we seek a possible solution for a medium to enable fast and facile transport of sodium ions and effective stress relief as desired in designing high performance anode for sodium ion batteries, a potential technology for grid-scale energy storage. We found ourselves inspired by Mother Nature, as trees tranport water and sodium ions and alike via soft wood fibers (cellulose) all the time. While the work can serve as another piece of examples of bioinspired engineering design, one of the electrochemists joked that if some day in the future we can just plug into trees to get electricity. Everyone laughed but in the hindsight in-line with this discussion, he indeed suggested a possible direction toward biointegration of the research findings of our work. I don't have a solution for now and believe it definitely requires more mindsets, which motivates the needs for more interactions between engineers and biologists. This would be the key to the success of bioinspiration and biointegration.  

p.s., just to entertain, often times artists could become more creative than engineers when they are exposed with a new idea. In a press coverage of our work by ACS, the following picture was used, which perfectly captures what I describes above.

Zhigang Suo's picture

Dear Teng:  Thank you for describing this conversation.  The work is fascinating, and the painting is even more so.  

When I was in China early this summer, I heard people talking about generating electricity from the tree.  Your comment reminded me of that conversation.  I went online and found a description of how to generate electricity from trees.  I have not looked into the technology carefully, but it might be of interest to you.  

Let's hope that others will relate their experience of bioinspiration and biointegration.

Dibakar Datta's picture

 Dear Dr. Teng Li,

 Inspired by this great work, I wrote a paper on Na-Ion Battery. I hope one day I will get an opportunity to work with you. 

 Thanks,

  Dibakar Datta

Xuanhe Zhao's picture

Dear Zhigang,

Many thanks for initiating this very interesting discussion. I would like to share our experience in seeking bioinspirations to solve one biorelated problem.

Biofouling, the accumulation of undesired bio-organisms on wetted surfaces, poses imminent challenges to biomedical devices, marine industry, food processing and water purification. Similar challenges are being faced by our lungs, which have to inhale significant amounts of dust, pollen and other foreign particles each day. However, nature offers an effective long-term solution -- tiny hairs called cilia on the surfaces of respiratory tracts constantly move back and forth, pushing inhaled foreign particles out of our lungs. In a conversation with biomedical engineer Gabriel Lopez on a different topic, the above biorelated problem and bioinspiration came across each other and immidately became the focus of our followup discussions, which eventually led to a unique antifouling idea – harnessing surface deformation of active materials to dynamically detach biofoulings. We are also lucky to have great students Qiming Wang, Phanindhar Shivapooja, Vrad Levering, who quickly turned the idea to fruition and demonstrated applications in both marine and biomedical antifoulings:

Bioinspired Surfaces with Dynamic Topography for Active Control of Biofouling,

Soft Robotic Concepts in Catheter Design: an On-demand Fouling-release Urinary Catheter

Zhigang Suo's picture

Dear Xuanhe:  Very inspiring!  I knew of your first paper, but not the second.  Now I'm intrigued.  It is always delightful to hear from you.

Nanshu Lu's picture

Dear Zhigang,

 

Thank you very much for keeping us working in the field of bioinspired and biointegrated motivated and inspired! It is also very enjoyable to learn about Teng and Xuanhe's facinating work. 

It has been 5 years since the concept of biointegrated electronics has been proposed by John Rogers and Yonggang Huang. While biointegrated sensors (both epidermal and implantable) have made significant progress, soft actuators are yet to catch up to close the sensing-feedback or diagnosis-therapy loop. Our recent work in collaboration with Dae-Hyeong Kim on a wearable device for movement disorders has applied silicon-based stretchable strain gauges for motion disorder tracking, paired with stretchable heaters for accelerated drug delivery once the motion disorder is detected. We want to point out here that in addition to mechanical interactions on the bio-electronics interface, there are also thermal, electrical, and chemical interactions, all of which are coupled to affect each other and lead to an overall outcome. 

Zhigang Suo's picture

Dear Nanshu:  So happy to see you do so well in the biointegration of electronics.  Indeed, even though bioinspiration and biointegration are two ancient ideas, the involvement of electronics is modern.  In neuroprosthetics, one may recall artificial pacemakers that regulate the heart,  cochlear implants that restore hearing, and retinal implants that restore vision.  A perspective on the development and commercialization of these neural implants is provided in Nature News on Electroceuticals.  

Yonggang Huang's picture

This is a very nice post on the emerging field of bioinspiration and biointegration.  This field has many important applications.  In fact, John Rogers and his colleagues have published a very nice review article 

Kim et al., “Materials for stretchable electronics in bio-inspired and bio-integrated devices,” MRS Bulletin, v 37, pp 226-235, 2012 (cover feature article)

that even has "bio-inspired and bio-integrated" in the title.

Another review paper by John Rogers and his colleagues published in Science also discussed extensively this emerging field.

Rogers et al., “Materials and mechanics for stretchable electronics,” Science, v 327, pp 1603-1607, 2010.

The biointegrated devices can facilitate seamless integration between human and devices, without any inteference to daily life, such as the epidermal electronics (Kim et al., “Epidermal electronics,” Science, v 333, pp 838-843, 2011) for continuous health monitoring (e.g., EKG, EMG, EcoG, temperature, acceleration) at any place (Xu et al., “Soft microfluidic assemblies of sensors, circuits and radios for the skin,” Scinece, v 344, pp 70-74, 2014).  The biointegrated devices can also influence or even wirelessly control the animal behavior (Kim et al., “Injectable, cellular-scale optoelectronics with applications for wireless optogenetics,” Science, v 340, pp 211-216, 2013).

For bioinspired devices, good examples include the electronic eye camera (Ko et al., “A hemispherical electronic eye camera based on compressible silicon optoelectronics,” Nature, v 454, pp 748-753, 2008) and the digital camera inspired by arthropod eye (Song et al., “Digital cameras with designs inspired by the arthropod eye,” Nature, v 497, pp 95-99, 2013).  These devices are inspired by animals and human, but may do better than them.

Bioinspiration and biointegration is really a very facinating field.

 

Zhigang Suo's picture

Thank you, Yonggang, for this quick summary of your recent work in collaboration with John Rogers.  I also enjoyed reading another post, where John was reported to remark that the collaboration between you two is "one of the most productive collaboration in physical sciences of all time".  Your joint work has shown the youthfulness and vitality of mechanics and electronics.  

The collaboration between you two has explored one of the most exciting frontier of our time, where electronics meet people.  This integration is still in its infancy, given the relatively short history of electronics, but has already generated excitement and promises.

Take Google glass as an example.  It looks silly, no matter how much money one pours into the design of the look.  The device is also stupid.  You have to talk to it.  It does not read your mind.  But wait, some people are trying to make Google glass read your mind.  The quality of mind reading might be very low at the moment, but it points to a direction to integrate electronics and people.  

What is the ultimate goal?  Who knows?  Michael Suo believed, when he was 13, that we might one day download knowledge directly to the brain.  I have not checked with him lately, but if that is the end game, we are indeed at the beginning of a trend.  In the meantime, people are developing brain-computer interfaces to provide solutions for healthcare.

The integration aims to realize bidirectional communication between people and the external.  The modes of interaction are diverse:  mechanical, electrical, optical, chemical...  The integration can occur at all levels:  body, organs, tissues, cells.  Once such bidirectional communication between people and computers are achieved, one can also achieve people-to-people communication.  The Internet provides a crude example of such communication.

The integration of electronics and people is a very young science indeed.  The field is so chaotic that we don't even have a name for it.  We have many names, all somehow related to, or enabled by, this integration.  I list some:

  • wearable electronics
  • biometric sensors
  • mobile health
  • teleoperation
  • neural recording
  • neural stimulation
  • neuroprosthetics
  • brain-machine interface
  • stretchable electronics
  • implantable electronics
  • injectable electronics
  • edible electronics
  • soft robots
  • soft machines
  • smart textile
  • bioelectronics
  • optogenetics
  • electroceutical
  • bionics
  • cyborg 

 

Yonggang Huang's picture

Dear Zhigang,

Thanks for the comments.  The bio-inspired and bio-integrated devices have already shown a promising future.  For example, the bio-integrated devices have enable one NOT to go to the hospital but to obtain and send the electrophysilogical data (e.g., EKG) from any place to his/her doctor.  The bio-integrated devices also enable true human-computer integration -- one does not need to wire any hard gadets to interact computers and machines.

Zhigang Suo's picture

Excellent point!  About two decades ago, it became clear that the bottleneck of the Internet was the last mile, the last leg of the network that connects to the individual users.   The last leg involves coaxial cables, etc., instead of optical fibers.  Back then, the interface between the Internet and the users was almost exclusively screens and keyboards.  

Now it has become clear that the Internet can do much more.  It can connect everything:  the locks of doors, the refrigerators in our homes, etc.  Or rather, the Internet is everything:  the locks and the refrigerators are all parts of the Internet.  

The interface between the Internet and the Things are sensors and actuators.  The Things can be our brains, hearts and stomachs.  Now the bottleneck is more intimate: it is last millimeter or micrometer or even smaller between the Internet and biological tissues. 

The Internet of Things will enable electronic health.  One benefit is to reduce the number of hospital visits.   A second benefit is to enable the comparison between the medial signals of one individual and the Big Data of all other individuals, living and dead.  We have all seen how Amazon recommends books to you by a combination of your past orders and orders of all other people, and how Google delivers search results at maddening speeds.  Healthcare will be dramatically changed by the Big Data.  After all, the medical knowledge has always been derived from individual patients.  That knowledge resides in the brains of doctors and their instruments.  They can all be parts of the Internet of the Things, or more specifically, the eHealth.   Your brain, her heart, and his stomach will all be parts of the Internet.  A patient is a source of information. The interface between the Internet and the Things can also be the mind readers, pacemakers and stomach stumulators.    

The last mile is a bottleneck because it is a century-old technology.  The last micron is a bottleneck because it is largely a non-existing, but rapidly emerging, technology.  This technology need be developed by a new generation of engineers.  The interface between the Internet and all Things is the most exciting frontier of our time. 

tongqing.lu's picture

Dear zhigang, thank you for initiating this intersting topic. As you wrote  when a person steps on a nail, the sensor in his foot sends a signal to his brain, the brain sends a signal to his muscle, and he lifts his foot.  The components of this nevous system can be made of soft materials, which turns the system into a soft machine.

Capacitive sensors made of polymer have advantages in softness, large strain, high sensitivity and small size.  

Viry et al. 2014 Flexible Three-Axial Force Sensor for Soft and Highly Sensitive Artificial Touch.

Stretchable and transparent inoic conductor can serve as the nerve to transport the signal.

Keplinger et al. 2013 Stretchable, Transparent, Inoic Conductors.

"Lifting the foot" needs an actuator, for which electrically active polymers are good candidates.

Brochu et al. 2010 Advances in Dielectric Elastomers for Actuators and Artificial Muscles.

The difficult part may be the processors. Human brain is so powerful and complex that probably no artificial brain can beat it. As Prof. Huang mentioned, human-computer integration can be a good choice. Alternate solution is the indirect control, e.g. human brain controls hands, soft acuators mimic the hands through the transporting signal.

Our group is now targeting to assemble these soft components. I'd like to hear more suggestions from all of you. Thank you! 

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