Tag Archives: bioinspiration

Bionic jellyfish for deep ocean exploration

This research may be a little disturbing for animal lovers as it involves conjoining a jellyfish (or sea jelly) and a robotic device. That said, a February 29, 2024 news item on ScienceDaily highlights new research into the oceanic depths,

Jellyfish can’t do much besides swim, sting, eat, and breed. They don’t even have brains. Yet, these simple creatures can easily journey to the depths of the oceans in a way that humans, despite all our sophistication, cannot.

But what if humans could have jellyfish explore the oceans on our behalf, reporting back what they find? New research conducted at Caltech [California Institute of Technology] aims to make that a reality through the creation of what researchers call biohybrid robotic jellyfish. These creatures, which can be thought of as ocean-going cyborgs, augment jellyfish with electronics that enhance their swimming and a prosthetic “hat” that can carry a small payload while also making the jellyfish swim in a more streamlined manner.

The researchers describe their work and provide recordings of the jellyfish,

A February 28, 2024 California Institute of Technology (Caltech) news release (also on EurekAlert) by Emily Velasco, which originated the news item, provides more detail,

The work, published in the journal Bioinspiration & Biomimetics, was conducted in the lab of John Dabiri (MS ’03, PhD ’05), the Centennial Professor of Aeronautics and Mechanical Engineering, and builds on his previous work augmenting jellyfish. Dabiri’s goal with this research is to use jellyfish as robotic data-gatherers, sending them into the oceans to collect information about temperature, salinity, and oxygen levels, all of which are affected by Earth’s changing climate.

“It’s well known that the ocean is critical for determining our present and future climate on land, and yet, we still know surprisingly little about the ocean, especially away from the surface,” Dabiri says. “Our goal is to finally move that needle by taking an unconventional approach inspired by one of the few animals that already successfully explores the entire ocean.”

Throughout his career, Dabiri has looked to the natural world, jellyfish included, for inspiration in solving engineering challenges. This work began with early attempts by Dabiri’s lab to develop a mechanical robot that swam like jellyfish, which have the most efficient method for traveling through water of any living creature. Though his research team succeeded in creating such a robot, that robot was never able to swim as efficiently as a real jellyfish. At that point, Dabiri asked himself, why not just work with jellyfish themselves?

“Jellyfish are the original ocean explorers, reaching its deepest corners and thriving just as well in tropical or polar waters,” Dabiri says. “Since they don’t have a brain or the ability to sense pain, we’ve been able to collaborate with bioethicists to develop this biohybrid robotic application in a way that’s ethically principled.”

Previously, Dabiri’s lab implanted jellyfish with a kind of electronic pacemaker that controls the speed at which they swim. In doing so, they found that if they made jellyfish swim faster than the leisurely pace they normally keep, the animals became even more efficient. A jellyfish swimming three times faster than it normally would uses only twice as much energy.

This time, the research team went a step further, adding what they call a forebody to the jellies. These forebodies are like hats that sit atop the jellyfish’s bell (the mushroom-shaped part of the animal). The devices were designed by graduate student and lead author Simon Anuszczyk (MS ’22), who aimed to make the jellyfish more streamlined while also providing a place where sensors and other electronics can be carried.

“Much like the pointed end of an arrow, we designed 3D-printed forebodies to streamline the bell of the jellyfish robot, reduce drag, and increase swimming performance,” Anuszczyk says. “At the same time, we experimented with 3D printing until we were able to carefully balance the buoyancy and keep the jellyfish swimming vertically.”

To test the augmented jellies’ swimming abilities, Dabiri’s lab undertook the construction of a massive vertical aquarium inside Caltech’s Guggenheim Laboratory. Dabiri explains that the three-story tank is tall, rather than wide, because researchers want to gather data on oceanic conditions far below the surface.

“In the ocean, the round trip from the surface down to several thousand meters will take a few days for the jellyfish, so we wanted to develop a facility to study that process in the lab,” Dabiri says. “Our vertical tank lets the animals swim against a flowing vertical current, like a treadmill for swimmers. We expect the unique scale of the facility—probably the first vertical water treadmill of its kind—to be useful for a variety of other basic and applied research questions.”

Swim tests conducted in the tank show that a jellyfish equipped with a combination of the swimming pacemaker and forebody can swim up to 4.5 times faster than an all-natural jelly while carrying a payload. The total cost is about $20 per jellyfish, Dabiri says, which makes biohybrid jellies an attractive alternative to renting a research vessel that can cost more than $50,000 a day to run.

“By using the jellyfish’s natural capacity to withstand extreme pressures in the deep ocean and their ability to power themselves by feeding, our engineering challenge is a lot more manageable,” Dabiri adds. “We still need to design the sensor package to withstand the same crushing pressures, but that device is smaller than a softball, making it much easier to design than a full submarine vehicle operating at those depths.

“I’m really excited to see what we can learn by simply observing these parts of the ocean for the very first time,” he adds.

Dabiri says future work may focus on further enhancing the bionic jellies’ abilities. Right now, they can only be made to swim faster in a straight line, such as the vertical paths being designed for deep ocean measurement. But further research may also make them steerable, so they can be directed horizontally as well as vertically.

The paper describing the work, “Electromechanical enhancement of live jellyfish for ocean exploration,” appears in the XX issue of Bioinspiration & Biomimetics. Co-authors are Anuszczyk and Dabiri.

Funding for the research was provided by the National Science Foundation and the Charles Lee Powell Foundation.

Here’s a link to and a citation for the paper,

Electromechanical enhancement of live jellyfish for ocean exploration by Simon R Anuszczyk and John O Dabiri. Bioinspiration & Biomimetics, Volume 19, Number 2 DOI 10.1088/1748-3190/ad277f Published 28 February 2024

This paper is open access.

International conference “Living Machines” dedicated to technology inspired by nature in Genoa, Italy (July 10 – 13, 2023)

I love the look and the theme for this “Living Machines” conference, which seems to be water,

A June 28, 2023 Istituto Italiano di Tecnologia (IIT) press release (also on EurekAlert) provides more detail about the conference,

Now in its twelfth year, the international conference “Living Machines”, organised by Istituto Italiano di Tecnologia (Italian Institute of Technology, IIT), returns to Italy and comes to Genoa for the first time, from 10 to 13 July. Around one hundred experts from all over the world are expected, and they will present their achievements in the field of bio-inspired science and technology. The conference will take place in an exceptional venue, the Acquario di Genova (Genoa Aquarium), which, having reached its 30th birthday, is the ideal location at which to bring together various subject areas, from biology to artificial intelligence and robotics, with a focus on sustainability and environmental protection.

The scientific organiser of the event is Barbara Mazzolai, Associate Director for Robotics and head of the Bioinspired Soft Robotics Lab at IIT, along with Fabian Meder, researcher in the Bioinspired Soft Robotics Lab group and co-chair of the conference programme.

The conference will include two events open to the public: an exhibition area, which will be accessible from 11 to 13 July in the afternoon (from 2 to 4.30 pm); and a scientific café, which will take place on the 12 July at 5 pm. The conference will be an opportunity for international guests to appreciate the region’s beauty and talents, and it will also include the participation of students from the Niccolò Paganini Conservatory of Music. In addition, a satellite event of the conference will be the ISPA – Italian Sustainability Photo Award – exhibition, which will open at Palazzo Ducale on 10 July at 6 p.m.

The “Living Machines” conference is the landmark event for the international scientific community which bases its research on living organisms, such as human beings and other animal species – terrestrial, marine, and airborne – in addition to plants, fungi, and bacteria, in order to create so-called “living machines”, in other words, forms of technology capable of replicating their structure and mechanisms of operation.

“The conference is rooted in the union between robotics and neuroscience, using man and other animal species as a model for the study of intelligence and control systems,” said Barbara Mazzolai, Associate Director for Robotics at IIT. “This year the conference will focus on the role of biomimicry in the creation of robots that are more sustainable, with applications for the challenges of environmental protection and human health. Discussions will revolve around the development of robots with a lower energy impact, made using recyclable and biodegradable materials, and that can be used in emergency situations or extreme environments, such as deep sea, soil, space, or environmental disasters, but also for precision agriculture, environmental surveillance, infrastructure monitoring, human care and medical-surgical assistance.

In the conference programme, experts will take part in a first day of parallel workshop and tutorial sessions (on 10 July), during which the topics of bioinspiration and biohybrid technology in the fields of medicine and the marine environment will be addressed. This first day will be followed by three days of plenary sessions, featuring talks by internationally-renowned scientists. More specifically: Oussama Khatib, one of the pioneers of robotics and director of the Robotics Laboratory at Stanford University; Marco Dorigo, professor at the Université Libre de Bruxelles and one of the pioneers of collective intelligence; Peter Fratzl, director of the Max Planck Institute of Colloids and Interfaces, working on research into osteoporosis and tissue regeneration; Eleni Stavrinidou, coordinator of the “Electronic Plants” group at Linköping University and an expert in bioelectronic and biohybrid systems; Olga Speck, Principal Researcher at the University of Freiburg, specialising in biomimetic materials and the regenerative capabilities of plants; and Kyu-Jin Cho, director of the Research Centre for Soft Robotics and the Biorobotics Laboratory at Seoul National University, one of the world’s leading experts on soft robotics.

For conference participants only, the programme includes: a visit to the Acquario, guided by the facility’s scientific staff, who will illustrate the work and practices needed for the protection and conservation of marine species and the undergoing research projects; an exhibition area for prototypes and products by research groups and companies operating in this field; and a dinner at Villa Lo Zerbino, with a musical contribution by students from the Niccolò Paganini Conservatory.

Open to the general public, on 12 July from 5 p.m. to 6 p.m. there will be a round table entitled “Living Machines: The Origin and the Future” chaired by science journalist Nicola Nosengo, Chief Editor of Nature Italy. Speakers will include Cecilia Laschi from the National University of Singapore, Vickie Webster-Wood from Carnegie Mellon University, Thomas Speck from the University of Freiburg and Paul Verschure from Radboud University Nijmegen.

A satellite initiative of the conference will be the exhibition for ISPA, the Italian Sustainability Photo Award, which will open at Palazzo Ducale on 10 July at 6.00 p.m. ISPA is the photographic award created by the Parallelozero agency in cooperation with the main sponsor PIMCO, to raise public awareness of environmental, social, and governance sustainability issues, encapsulated in the acronym ESG. The works of the winning photographers and finalists in the last three editions will be on display in Genoa: a selection of images that depict the emblematic stories of Italy, a nation moving towards a more sustainable future, a visual narrative that makes it easier to understand the country’s progress in research and innovation.

The organisations supporting the event include, in addition to the principal organiser Istituto Italiano di Tecnologia (Italian Institute of Technology), the international Convergent Science Network [emphasis mine], the Office of Naval Research, Radboud University Nijmegen, and the Living, Adaptive and Energy-autonomous Materials Systems Cluster of Excellence in Freiburg.

Event website: https://livingmachinesconference.eu/2023/

I was particularly struck by this quote, “The conference is rooted in the union between robotics and neuroscience [emphasis mine], using man and other animal species as a model for the study of intelligence and control systems,” from Barbara Mazzolai as I have an as yet unpublished post for a UNESCO neurotechnology event coming up on July 13, 2023. These events come on the heels of a May 16, 2023 Canadian Science Policy Centre panel discussion on responsible neurotechnology (see my May 12, 2023 posting).

For the curious, you can find the Convergent Science Network here.

Smartphone battery inspired by your guts?

The conversion of bacteria from an enemy to be vanquished at all costs to a ‘frenemy’, a friendly enemy supplying possible solutions for problems is fascinating. An Oct. 26, 2016 news item on Nanowerk falls into the ‘frenemy’ camp,

A new prototype of a lithium-sulphur battery – which could have five times the energy density of a typical lithium-ion battery – overcomes one of the key hurdles preventing their commercial development by mimicking the structure of the cells which allow us to absorb nutrients.

Researchers have developed a prototype of a next-generation lithium-sulphur battery which takes its inspiration in part from the cells lining the human intestine. The batteries, if commercially developed, would have five times the energy density of the lithium-ion batteries used in smartphones and other electronics.

An Oct. 26, 2016 University of Cambridge press release (also on EurekAlert), which originated the news item, expands on the theme and provides some good explanations of how lithium-ion batteries and lithium-sulphur batteries work (Note: A link has been removed),

The new design, by researchers from the University of Cambridge, overcomes one of the key technical problems hindering the commercial development of lithium-sulphur batteries, by preventing the degradation of the battery caused by the loss of material within it. The results are reported in the journal Advanced Functional Materials.

Working with collaborators at the Beijing Institute of Technology, the Cambridge researchers based in Dr Vasant Kumar’s team in the Department of Materials Science and Metallurgy developed and tested a lightweight nanostructured material which resembles villi, the finger-like protrusions which line the small intestine. In the human body, villi are used to absorb the products of digestion and increase the surface area over which this process can take place.

In the new lithium-sulphur battery, a layer of material with a villi-like structure, made from tiny zinc oxide wires, is placed on the surface of one of the battery’s electrodes. This can trap fragments of the active material when they break off, keeping them electrochemically accessible and allowing the material to be reused.

“It’s a tiny thing, this layer, but it’s important,” said study co-author Dr Paul Coxon from Cambridge’s Department of Materials Science and Metallurgy. “This gets us a long way through the bottleneck which is preventing the development of better batteries.”

A typical lithium-ion battery is made of three separate components: an anode (negative electrode), a cathode (positive electrode) and an electrolyte in the middle. The most common materials for the anode and cathode are graphite and lithium cobalt oxide respectively, which both have layered structures. Positively-charged lithium ions move back and forth from the cathode, through the electrolyte and into the anode.

The crystal structure of the electrode materials determines how much energy can be squeezed into the battery. For example, due to the atomic structure of carbon, each carbon atom can take on six lithium ions, limiting the maximum capacity of the battery.

Sulphur and lithium react differently, via a multi-electron transfer mechanism meaning that elemental sulphur can offer a much higher theoretical capacity, resulting in a lithium-sulphur battery with much higher energy density. However, when the battery discharges, the lithium and sulphur interact and the ring-like sulphur molecules transform into chain-like structures, known as a poly-sulphides. As the battery undergoes several charge-discharge cycles, bits of the poly-sulphide can go into the electrolyte, so that over time the battery gradually loses active material.

The Cambridge researchers have created a functional layer which lies on top of the cathode and fixes the active material to a conductive framework so the active material can be reused. The layer is made up of tiny, one-dimensional zinc oxide nanowires grown on a scaffold. The concept was trialled using commercially-available nickel foam for support. After successful results, the foam was replaced by a lightweight carbon fibre mat to reduce the battery’s overall weight.

“Changing from stiff nickel foam to flexible carbon fibre mat makes the layer mimic the way small intestine works even further,” said study co-author Dr Yingjun Liu.

This functional layer, like the intestinal villi it resembles, has a very high surface area. The material has a very strong chemical bond with the poly-sulphides, allowing the active material to be used for longer, greatly increasing the lifespan of the battery.

“This is the first time a chemically functional layer with a well-organised nano-architecture has been proposed to trap and reuse the dissolved active materials during battery charging and discharging,” said the study’s lead author Teng Zhao, a PhD student from the Department of Materials Science & Metallurgy. “By taking our inspiration from the natural world, we were able to come up with a solution that we hope will accelerate the development of next-generation batteries.”

For the time being, the device is a proof of principle, so commercially-available lithium-sulphur batteries are still some years away. Additionally, while the number of times the battery can be charged and discharged has been improved, it is still not able to go through as many charge cycles as a lithium-ion battery. However, since a lithium-sulphur battery does not need to be charged as often as a lithium-ion battery, it may be the case that the increase in energy density cancels out the lower total number of charge-discharge cycles.

“This is a way of getting around one of those awkward little problems that affects all of us,” said Coxon. “We’re all tied in to our electronic devices – ultimately, we’re just trying to make those devices work better, hopefully making our lives a little bit nicer.”

Here’s a link to and a citation for the paper,

Advanced Lithium–Sulfur Batteries Enabled by a Bio-Inspired Polysulfide Adsorptive Brush by Teng Zhao, Yusheng Ye, Xiaoyu Peng, Giorgio Divitini, Hyun-Kyung Kim, Cheng-Yen Lao, Paul R. Coxon, Kai Xi, Yingjun Liu, Caterina Ducati, Renjie Chen, R. Vasant Kumar. Advanced Functional Materials DOI: 10.1002/adfm.201604069 First published: 26 October 2016

This paper is behind a paywall.

Caption: This is a computer visualization of villi-like battery material. Credit: Teng Zhao

Caption: This is a computer visualization of villi-like battery material. Credit: Teng Zhao

A new memristor circuit

Apparently engineers at the University of Massachusetts at Amherst have developed a new kind of memristor. A Sept. 29, 2016 news item on Nanowerk makes the announcement (Note: A link has been removed),

Engineers at the University of Massachusetts Amherst are leading a research team that is developing a new type of nanodevice for computer microprocessors that can mimic the functioning of a biological synapse—the place where a signal passes from one nerve cell to another in the body. The work is featured in the advance online publication of Nature Materials (“Memristors with diffusive dynamics as synaptic emulators for neuromorphic computing”).

Such neuromorphic computing in which microprocessors are configured more like human brains is one of the most promising transformative computing technologies currently under study.

While it doesn’t sound different from any other memristor, that’s misleading. Do read on. A Sept. 27, 2016 University of Massachusetts at Amherst news release, which originated the news item, provides more detail about the researchers and the work,

J. Joshua Yang and Qiangfei Xia are professors in the electrical and computer engineering department in the UMass Amherst College of Engineering. Yang describes the research as part of collaborative work on a new type of memristive device.

Memristive devices are electrical resistance switches that can alter their resistance based on the history of applied voltage and current. These devices can store and process information and offer several key performance characteristics that exceed conventional integrated circuit technology.

“Memristors have become a leading candidate to enable neuromorphic computing by reproducing the functions in biological synapses and neurons in a neural network system, while providing advantages in energy and size,” the researchers say.

Neuromorphic computing—meaning microprocessors configured more like human brains than like traditional computer chips—is one of the most promising transformative computing technologies currently under intensive study. Xia says, “This work opens a new avenue of neuromorphic computing hardware based on memristors.”

They say that most previous work in this field with memristors has not implemented diffusive dynamics without using large standard technology found in integrated circuits commonly used in microprocessors, microcontrollers, static random access memory and other digital logic circuits.

The researchers say they proposed and demonstrated a bio-inspired solution to the diffusive dynamics that is fundamentally different from the standard technology for integrated circuits while sharing great similarities with synapses. They say, “Specifically, we developed a diffusive-type memristor where diffusion of atoms offers a similar dynamics [?] and the needed time-scales as its bio-counterpart, leading to a more faithful emulation of actual synapses, i.e., a true synaptic emulator.”

The researchers say, “The results here provide an encouraging pathway toward synaptic emulation using diffusive memristors for neuromorphic computing.”

Here’s a link to and a citation for the paper,

Memristors with diffusive dynamics as synaptic emulators for neuromorphic computing by Zhongrui Wang, Saumil Joshi, Sergey E. Savel’ev, Hao Jiang, Rivu Midya, Peng Lin, Miao Hu, Ning Ge, John Paul Strachan, Zhiyong Li, Qing Wu, Mark Barnell, Geng-Lin Li, Huolin L. Xin, R. Stanley Williams [emphasis mine], Qiangfei Xia, & J. Joshua Yang. Nature Materials (2016) doi:10.1038/nmat4756 Published online 26 September 2016

This paper is behind a paywall.

I’ve emphasized R. Stanley Williams’ name as he was the lead researcher on the HP Labs team that proved Leon Chua’s 1971 theory about the memristor and exerted engineering control of the memristor in 2008. (Bernard Widrow, in the 1960s,  predicted and proved the existence of something he termed a ‘memistor’. Chua arrived at his ‘memristor’ theory independently.)

Austin Silver in a Sept. 29, 2016 posting on The Human OS blog (on the IEEE [Institute of Electrical and Electronics Engineers] website) delves into this latest memristor research (Note: Links have been removed),

In research published in Nature Materials on 26 September [2016], Yang and his team mimicked a crucial underlying component of how synaptic connections get stronger or weaker: the flow of calcium.

The movement of calcium into or out of the neuronal membrane, neuroscientists have found, directly affects the connection. Chemical processes move the calcium in and out— triggering a long-term change in the synapses’ strength. 2015 research in ACS NanoLetters and Advanced Functional Materials discovered that types of memristors can simulate some of the calcium behavior, but not all.

In the new research, Yang combined two types of memristors in series to create an artificial synapse. The hybrid device more closely mimics biological synapse behavior—the calcium flow in particular, Yang says.

The new memristor used–called a diffusive memristor because atoms in the resistive material move even without an applied voltage when the device is in the high resistance state—was a dielectic film sandwiched between Pt [platinum] or Au [gold] electrodes. The film contained Ag [silver] nanoparticles, which would play the role of calcium in the experiments.

By tracking the movement of the silver nanoparticles inside the diffusive memristor, the researchers noticed a striking similarity to how calcium functions in biological systems.

A voltage pulse to the hybrid device drove silver into the gap between the diffusive memristor’s two electrodes–creating a filament bridge. After the pulse died away, the filament started to break and the silver moved back— resistance increased.

Like the case with calcium, a force made silver go in and a force made silver go out.

To complete the artificial synapse, the researchers connected the diffusive memristor in series to another type of memristor that had been studied before.

When presented with a sequence of voltage pulses with particular timing, the artificial synapse showed the kind of long-term strengthening behavior a real synapse would, according to the researchers. “We think it is sort of a real emulation, rather than simulation because they have the physical similarity,” Yang says.

I was glad to find some additional technical detail about this new memristor and to find the Human OS blog, which is new to me and according to its home page is a “biomedical blog, featuring the wearable sensors, big data analytics, and implanted devices that enable new ventures in personalized medicine.”

Robots built from living tissue

Biohybrid robots, as they are known, are built from living tissue but not in a Frankenstein kind of way as Victoria Webster PhD candidate at Case Western Reserve University (US) explains in her Aug. 9, 2016 essay on The Conversation (also on phys.org as an Aug. 10, 2016 news item; Note: Links have been removed),

Researchers are increasingly looking for solutions to make robots softer or more compliant – less like rigid machines, more like animals. With traditional actuators – such as motors – this can mean using air muscles or adding springs in parallel with motors. …

But there’s a growing area of research that’s taking a different approach. By combining robotics with tissue engineering, we’re starting to build robots powered by living muscle tissue or cells. These devices can be stimulated electrically or with light to make the cells contract to bend their skeletons, causing the robot to swim or crawl. The resulting biobots can move around and are soft like animals. They’re safer around people and typically less harmful to the environment they work in than a traditional robot might be. And since, like animals, they need nutrients to power their muscles, not batteries, biohybrid robots tend to be lighter too.

Webster explains how these biobots are built,

Researchers fabricate biobots by growing living cells, usually from heart or skeletal muscle of rats or chickens, on scaffolds that are nontoxic to the cells. If the substrate is a polymer, the device created is a biohybrid robot – a hybrid between natural and human-made materials.

If you just place cells on a molded skeleton without any guidance, they wind up in random orientations. That means when researchers apply electricity to make them move, the cells’ contraction forces will be applied in all directions, making the device inefficient at best.

So to better harness the cells’ power, researchers turn to micropatterning. We stamp or print microscale lines on the skeleton made of substances that the cells prefer to attach to. These lines guide the cells so that as they grow, they align along the printed pattern. With the cells all lined up, researchers can direct how their contraction force is applied to the substrate. So rather than just a mess of firing cells, they can all work in unison to move a leg or fin of the device.

Researchers sometimes mimic animals when creating their biobots (Note: Links have been removed),

Others have taken their cues from nature, creating biologically inspired biohybrids. For example, a group led by researchers at California Institute of Technology developed a biohybrid robot inspired by jellyfish. This device, which they call a medusoid, has arms arranged in a circle. Each arm is micropatterned with protein lines so that cells grow in patterns similar to the muscles in a living jellyfish. When the cells contract, the arms bend inwards, propelling the biohybrid robot forward in nutrient-rich liquid.

More recently, researchers have demonstrated how to steer their biohybrid creations. A group at Harvard used genetically modified heart cells to make a biologically inspired manta ray-shaped robot swim. The heart cells were altered to contract in response to specific frequencies of light – one side of the ray had cells that would respond to one frequency, the other side’s cells responded to another.

Amazing, eh? And, this is quite a recent video; it was published on YouTube on July 7, 2016.

Webster goes on to describe work designed to make these robots hardier and more durable so they can leave the laboratory,

… Here at Case Western Reserve University, we’ve recently begun to investigate … by turning to the hardy marine sea slug Aplysia californica. Since A. californica lives in the intertidal region, it can experience big changes in temperature and environmental salinity over the course of a day. When the tide goes out, the sea slugs can get trapped in tide pools. As the sun beats down, water can evaporate and the temperature will rise. Conversely in the event of rain, the saltiness of the surrounding water can decrease. When the tide eventually comes in, the sea slugs are freed from the tidal pools. Sea slugs have evolved very hardy cells to endure this changeable habitat.

We’ve been able to use Aplysia tissue to actuate a biohybrid robot, suggesting that we can manufacture tougher biobots using these resilient tissues. The devices are large enough to carry a small payload – approximately 1.5 inches long and one inch wide.

Webster has written a fascinating piece and, if you have time, I encourage you to read it in its entirety.

Mimicking the sea urchin’s mouth and teeth for space exploration

Researchers at the University of California at San Diego (UCSD) have designed a new device for use in space exploration that is based on the structure and mechanics of a sea urchin’s mouth and teeth. From a May 2, 2016 news item on ScienceDaily,

The sea urchin’s intricate mouth and teeth are the model for a claw-like device developed by a team of engineers and marine biologists at the University of California, San Diego to sample sediments on other planets, such as Mars. The researchers detail their work in a recent issue of the Journal of Visualized Experiments.

A May 2, 2016 UCSD press release (also on EurekAlert), which originated the news item, expands on the theme by hearkening back to Aristotle (a Greek philosopher),

The urchin’s mouthpiece was first described in detail by the Greek philosopher Aristotle, earning it the nickname “Aristotle’s lantern.” It is comprised of an intricate framework of muscles and five curved teeth with triangle-shaped tips that can scrape, cut, chew and bore holes into the toughest rocks—a colony of sea urchins can destroy an entire kelp forest by churning through rock and uprooting seaweed.  The teeth are arranged in a dome-like formation that opens outwards and closes inwards in a smooth motion, similar to a claw in an arcade prize-grabbing machine.

The news release goes on to describe the methodology,

Bio-inspiration for the study came from pink sea urchins (Strongylocentrotus fragilis), which live off the West Coast of North America, at depths ranging from 100 to 1000 meters in the Pacific Ocean. The urchins were collected for scientific research by the Scripps Institution of Oceanography at UC San Diego.

Researchers extracted the urchins’ mouthpieces, scanned them with microCT, essentially a 3D microscopy technique, and analyzed the structures at the National Center for Microscopy and Imaging Research at the School of Medicine at UC San Diego. This allowed engineers to build a highly accurate model of the mouthpiece’s geometry.

Researchers also used finite element analysis to investigate the structure of the teeth, a method that allowed them to determine the importance of the keel to the teeth’s performance.

Engineers then turned the microCT data into a user-friendly file that a team of undergraduate engineering students at UC San Diego used to start iterating prototypes of the claw-like device, under the supervision of Ph.D. students in McKittrick’s lab.

The first iteration was very close to the mouthpiece’s natural structure, but didn’t do a very good job at grasping sand.  In the second iteration, students flattened the pointed end of the teeth so the device would scoop up sand better. But the device wasn’t opening quite right. Finally, on the third iteration, they connected the teeth differently to the rest of the device, which allowed it to open much easier. The students were able to quickly modify each prototype by using 3D printers in the UC San Diego Design Studio.

The device was then attached to a remote-controlled small rover. The researchers first tested the claw on beach sand, where it performed well. They then used the claw on sand that simulates Martian soil in density and humidity (or lack thereof). The device was able to scoop up sand efficiently. Researchers envision a fleet of mini rovers equipped with the claw that could be deployed to collect samples and bring them back to a main rover. Frank hopes that this design will be of interest to NASA [US National Aeronautics and Space Administraton] and SpaceX [a private enterprise for designing, manufacturing, and launching craft bound for space].

Here’s a link to and a citation for the paper,

A Protocol for Bioinspired Design: A Ground Sampler Based on Sea Urchin Jaws by Michael B. Frank, Steven E. Naleway, Taylor S. Wirth, Jae-Young Jung, Charlene L. Cheung, Faviola B. Loera, Sandra Medina, Kirk N. Sato, Jennifer R. A. Taylor, Joanna McKittrick. Journal of Visualized Experiments, 2016; (110) DOI: 10.3791/53554 Date Published: 4/24/2016

This paper and its video are behind a paywall. For those unfamiliar with the Journal of Visualized Experiments (JOVE), it is focused largely on videos which demonstrate the various techniques and protocols being described in the accompanying papers.

The researchers have made an introductory video available courtesy of UCSD,

4D printing: a hydrogel orchid

In 2013, the 4th dimension for printing was self-assembly according to a March 1, 2013 article by Tuan Nguyen for ZDNET. A Jan. 25, 2016 Wyss Institute for Biologically Inspired Engineering at Harvard University news release (also on EurekAlert) points to time as the fourth dimension in a description of the Wyss Institute’s latest 4D printed object,

A team of scientists at the Wyss Institute for Biologically Inspired Engineering at Harvard University and the Harvard John A. Paulson School of Engineering and Applied Sciences has evolved their microscale 3D printing technology to the fourth dimension, time. Inspired by natural structures like plants, which respond and change their form over time according to environmental stimuli, the team has unveiled 4D-printed hydrogel composite structures that change shape upon immersion in water.

“This work represents an elegant advance in programmable materials assembly, made possible by a multidisciplinary approach,” said Jennifer Lewis, Sc.D., senior author on the new study. “We have now gone beyond integrating form and function to create transformable architectures.”

In nature, flowers and plants have tissue composition and microstructures that result in dynamic morphologies that change according to their environments. Mimicking the variety of shape changes undergone by plant organs such as tendrils, leaves, and flowers in response to environmental stimuli like humidity and/or temperature, the 4D-printed hydrogel composites developed by Lewis and her team are programmed to contain precise, localized swelling behaviors. Importantly, the hydrogel composites contain cellulose fibrils that are derived from wood and are similar to the microstructures that enable shape changes in plants.

By aligning cellulose fibrils (also known as, cellulose nanofibrils or nanofibrillated cellulose) during printing, the hydrogel composite ink is encoded with anisotropic swelling and stiffness, which can be patterned to produce intricate shape changes. The anisotropic nature of the cellulose fibrils gives rise to varied directional properties that can be predicted and controlled. Just like wood, which can be split easier along the grain rather than across it. Likewise, when immersed in water, the hydrogel-cellulose fibril ink undergoes differential swelling behavior along and orthogonal to the printing path. Combined with a proprietary mathematical model developed by the team that predicts how a 4D object must be printed to achieve prescribed transformable shapes, the new method opens up many new and exciting potential applications for 4D printing technology including smart textiles, soft electronics, biomedical devices, and tissue engineering.

“Using one composite ink printed in a single step, we can achieve shape-changing hydrogel geometries containing more complexity than any other technique, and we can do so simply by modifying the print path,” said Gladman [A. Sydney Gladman, Wyss Institute a graduate research assistant]. “What’s more, we can interchange different materials to tune for properties such as conductivity or biocompatibility.”

The composite ink that the team uses flows like liquid through the printhead, yet rapidly solidifies once printed. A variety of hydrogel materials can be used interchangeably resulting in different stimuli-responsive behavior, while the cellulose fibrils can be replaced with other anisotropic fillers of choice, including conductive fillers.

“Our mathematical model prescribes the printing pathways required to achieve the desired shape-transforming response,” said Matsumoto [Elisabetta Matsumoto, Ph.D., a postdoctoral fellow at the Wyss]. “We can control the curvature both discretely and continuously using our entirely tunable and programmable method.”

Specifically, the mathematical modeling solves the “inverse problem”, which is the challenge of being able to predict what the printing toolpath must be in order to encode swelling behaviors toward achieving a specific desired target shape.

“It is wonderful to be able to design and realize, in an engineered structure, some of nature’s solutions,” said Mahadevan [L. Mahadevan, Ph.D., a Wyss Core Faculty member] , who has studied phenomena such as how botanical tendrils coil, how flowers bloom, and how pine cones open and close. “By solving the inverse problem, we are now able to reverse-engineer the problem and determine how to vary local inhomogeneity, i.e. the spacing between the printed ink filaments, and the anisotropy, i.e. the direction of these filaments, to control the spatiotemporal response of these shapeshifting sheets. ”

“What’s remarkable about this 4D printing advance made by Jennifer and her team is that it enables the design of almost any arbitrary, transformable shape from a wide range of available materials with different properties and potential applications, truly establishing a new platform for printing self-assembling, dynamic microscale structures that could be applied to a broad range of industrial and medical applications,” said Wyss Institute Founding Director Donald Ingber, M.D., Ph.D., who is also the Judah Folkman Professor of Vascular Biology at Harvard Medical School and the Vascular Biology Program at Boston Children’s Hospital and Professor of Bioengineering at Harvard SEAS [School of Engineering and Applied Science’.

Here’s an animation from the Wyss Institute illustrating the process,

And, here’s a link to and a citation for the paper,

Biomimetic 4D printing by A. Sydney Gladman, Elisabetta A. Matsumoto, Ralph G. Nuzzo, L. Mahadevan, & Jennifer A. Lewis. Nature Materials (2016) doi:10.1038/nmat4544 Published online 25 January 2016

This paper is behind a paywall.

A bioinspired approach to self-healing materials

Scientists have been working to develop self-healing materials for a while now and a Jan. 8, 2016 news item on Nanowerk chronicles a relatively recent attempt,

Inspired by healing wounds in skin, a new approach protects and heals surfaces using a fluid secretion process. In response to damage, dispersed liquid-storage droplets are controllably secreted. The stored liquid replenishes the surface and completes the repair of the polymer in seconds to hours …

The fluid secretion approach to repair the material has also been demonstrated in fibers and microbeads. This bioinspired approach could be extended to create highly desired adaptive, resilient materials with possible uses in heat transfer, humidity control, slippery surfaces, and fluid delivery.

A December ??, 2015 US Department of Energy (DOE) news release, which originated the news item, expands on the theme,

A polymer that secretes stored liquid in response to damage has been designed and created to function as a self-healing material. While human-made material systems can trigger the release of stored contents, the ability to continuously self-adjust and monitor liquid supply in these compartments is a challenge. In contrast, biological systems manage complex protection and healing functions by having individual components work in concert to initiate and self-regulate a coordinated response. Inspired by biological wound-healing, this new process, developed by researchers at Harvard University, involves trapping and dispersing liquid-storage droplets within a reversibly crosslinked polymer gel network topped with a thin liquid overlayer. This novel approach allows storage of the liquid, yet is reconfigurable to induce finely controlled secretion in response to polymer damage. When the gel was damaged by slicing, the ruptured droplets in the immediate vicinity of the damage released oil and the gel network was squeezed. This squeezing allowed oil to be pushed out from neighboring droplets and the polymer network linkages to unzip and rezip rapidly, allowing just enough oil to flow to the damaged region. Healing occurred at ambient temperature within seconds to hours as fluid was secreted into the crack, severed polymer ends diffused across the gap, and new network linkages were created. Droplet-embedded polymers repaired faster or at lower temperatures than polymers without oil droplets. Also, the repaired droplet-embedded materials were much stronger than the repaired networks that did not contain the droplets. This dynamic liquid exchange to repair the material has also been demonstrated in other forms, showing the potential to extend this bioinspired approach for fabricating highly desired adaptive, resilient materials to a wide range of polymeric structures.

Here’s a link to and a citation for the paper,

Dynamic polymer systems with self-regulated secretion for the control of surface properties and material healing by Jiaxi Cui, Daniel Daniel, Alison Grinthal, Kaixiang Lin, & Joanna Aizenberg. Nature Materials 14,  790–795 (2015) doi:10.1038/nmat4325 Published online 22 June 2015

I’m not sure what occasioned a late push to promote this particular piece of research but if you are interested, the paper is behind a paywall.

Building nanocastles in the sand

Scientists have taken inspiration from sandcastles to build robots made of nanoparticles. From an Aug. 5, 2015 news item on ScienceDaily,

If you want to form very flexible chains of nanoparticles in liquid in order to build tiny robots with flexible joints or make magnetically self-healing gels, you need to revert to childhood and think about sandcastles.

In a paper published this week in Nature Materials, researchers from North Carolina State University and the University of North Carolina-Chapel Hill show that magnetic nanoparticles encased in oily liquid shells can bind together in water, much like sand particles mixed with the right amount of water can form sandcastles.

An Aug. 5, 2015 North Carolina State University (NCSU) news release (also on EurekAlert) by Mick Kulikowski, which originated the news item, expands on the theme,

“Because oil and water don’t mix, the oil wets the particles and creates capillary bridges between them so that the particles stick together on contact,” said Orlin Velev, INVISTA Professor of Chemical and Biomolecular Engineering at NC State and the corresponding author of the paper.

“We then add a magnetic field to arrange the nanoparticle chains and provide directionality,” said Bhuvnesh Bharti, research assistant professor of chemical and biomolecular engineering at NC State and first author of the paper.

Chilling the oil is like drying the sandcastle. Reducing the temperature from 45 degrees Celsius to 15 degrees Celsius freezes the oil and makes the bridges fragile, leading to breaking and fragmentation of the nanoparticle chains. Yet the broken nanoparticles chains will re-form if the temperature is raised, the oil liquefies and an external magnetic field is applied to the particles.

“In other words, this material is temperature responsive, and these soft and flexible structures can be pulled apart and rearranged,” Velev said. “And there are no other chemicals necessary.”

The paper is also co-authored by Anne-Laure Fameau, a visiting researcher from INRA [French National Institute for Agricultural Research or Institut National de la Recherche Agronomique], France. …

Here’s a link to and a citation for the paper,

Nanocapillarity-mediated magnetic assembly of nanoparticles into ultraflexible filaments and reconfigurable networks by Bhuvnesh Bharti, Anne-Laure Fameau, Michael Rubinstein, & Orlin D. Velev. Nature Materials (2015) doi:10.1038/nmat4364 Published online 03 August 2015

This paper is behind a paywall.