INAE Monthly E-News Letter Vol. VIII, Issue 2, February 1, 2017

 (+) Academy Activities

From the Editor’s Desk

Trust begets trust
It is believed that both ‘cold reasons’ and ‘hot emotions’ are needed to take ‘right decisions’. Trustworthy decisions emanate from a trustworthy mind. Being realistic, honest, and forgiving with yourself and with Read more...

Purnendu Ghosh
Chief Editor of Publications

 (+) Editorial Board, INAE

 (+) Articles by INAE Fellows

Dr Purnendu Ghosh
Dr Baldev Raj
Dr K V Raghavan
Dr Sanak Mishra
Prof. Indranil Manna
Prof BS Murty
Prof Sanghamitra Bandyopadhyay
Prof Pradip Dutta
Prof Manoj K Tiwari
Prof Sanjay Mittal
Prof Prasun K Roy
Brig Rajan Minocha

 (+) Engineering and Technology Updates

  Civil Engineering

  Computer Engineering  and Information Technology

  Mechanical Engineering

  Chemical Engineering

  Electrical Engineering

  Electronics and Communication Engineering

  Aerospace Engineering

  Mining, Metallurgical and Materials Engineering

  Energy Engineering

  Interdisciplinary Engineering and Special Fields 

 (+) Engineering Innovation in India
 (+) Previous E-newsletter

 

Civil Engineering

1. World’s Highest Bridge Opens in China

The world’s highest bridge has opened to traffic in China on December 30, 2016, connecting two provinces in the mountainous southwest and reducing travel times by as much as three-quarters. The Beipanjiang Bridge soars 565 metres (1,854 feet) above a river and connects the two mountainous provinces of Yunnan and Guizhou, the Guizhou provincial transport department said in a statement on its official website. The 1,341-metre span cost over 1 billion yuan ($144 million) to build. It overtook the Si Du River Bridge in the central province of Hubei to become the world’s highest bridge. Several of the world’s highest bridges are in China, although the world’s tallest bridge — measured in terms of the height of its own structure, rather than the distance to the ground — remains France’s Millau viaduct at 343 metres.

 

Source : http://www.thehindu.com/news/international/Worlds-highest-bridge-opens-in-China/article16963400.ece

 

Computer Engineering and Information Technology

2.  Scientists Turn Memory Chips into Processors to Speed Up Computing Tasks

ReRAM Computing Circuit is under the microscopes.

A team of international scientists have found a way to make memory chips perform computing tasks, which is traditionally done by computer processors like those made by Intel and Qualcomm. This means data could now be processed in the same spot where it is stored, leading to much faster and thinner mobile devices and computers. This new computing circuit was developed by Nanyang Technological University, Singapore in collaboration with Germany’s RWTH Aachen University. It is built using state-of-the-art memory chips known as Redox-based resistive switching random access memory (ReRAM). Developed by global chipmakers such as SanDisk and Panasonic, this type of chip is one of the fastest memory modules that will soon be available commercially. However, instead of storing information the researchers showed how ReRAM can also be used to process data. Current devices and computers have to transfer data from the memory storage to the processor unit for computation, while the new NTU circuit saves time and energy by eliminating these data transfers. It can also boost the speed of current processors found in laptops and mobile devices by at least two times or more. By making the memory chip perform computing tasks, space can be saved by eliminating the processor, leading to thinner, smaller and lighter electronics. The discovery could also lead to new design possibilities for consumer electronics and wearable technology. Currently, all computer processors in the market are using the binary system, which is composed of two states — either 0 or 1. For example, the letter A will be processed and stored as 01000001, an 8-bit character. However, the prototype ReRAM circuit processes data in more than just two states. For example, it can store and process data as 0, 1, or 2, known as a ternary number system. Because ReRAM uses different electrical resistance to store information, it could be possible to store the data in an even higher number of states, hence speeding up computing tasks beyond current limitations. In current computer systems, all information has to be translated into a string of zeros and ones before it can be processed. The quest for faster processing is one of the most pressing needs for industries worldwide, as computer software is getting increasingly complex while data centres have to deal with more information than ever. The researchers said that using ReRAM for computing will be more cost-effective than other computing technologies on the horizon, since ReRAMs will be available in the market soon. ReRAM is a versatile non-volatile memory concept. These devices are energy-efficient, fast, and they can be scaled to very small dimensions. Using them not only for data storage but also for computation could open a completely new route towards an effective use of energy in the information technology. The excellent properties of ReRAM like its long-term storage capacity, low energy usage and ability to be produced at the nanoscale level have drawn many semiconductor companies to invest in researching this promising technology. The research team is now looking to engage industry partners to leverage this important advance of ReRAM-based ternary computing.



Source : https://www.sciencedaily.com/releases/2017/01/170103101808.htm
 

 

Mechanical Engineering

3.  Additive Manufacturing: A New Twist for Stretchable Electronics?

Electronic components that can be elongated or twisted — known as “stretchable” electronics — could soon be used to power electronic gadgets, the onboard systems of vehicles, medical devices and other products. And a 3-D printing-like approach to manufacturing may help make stretchable electronics more prevalent, say researchers at Missouri University of Science and Technology. Missouri S&T researchers assess the current state of the emerging field of stretchable electronics, focusing on a type of conductor that can be built on or set into the surface of a polymer known as elastomer. These conductors could one day replace the rigid, brittle circuit board that powers many of today’s electronic devices. They could be used, for example, as wearable sensors that adhere to the skin to monitor heart rate or brain activity, as sensors in clothing or as thin solar panels that could be plastered onto curved surfaces. Key to the future of stretchable electronics is the surface, or substrate. Elastomer, as its name implies, is a flexible material with high elasticity, which means that it can be bent, stretched, buckled and twisted repeatedly with little impact on its performance. One challenge facing this class of stretchable electronics involves “overcoming mismatches” between the flexible elastomer base and more brittle electronic conductors, the researchers explain. “Unique designs and stretching mechanics have been proposed to harmonize the mismatches and integrate materials with widely different properties as one unique system,” writes the research team. A relatively new manufacturing technique known as additive manufacturing may help resolve this issue, they say. Additive manufacturing is a process that allows manufacturers to create three-dimensional objects, layer by layer — much like 3-D printing, but with metals, ceramics or other materials. The researchers suggest that additive manufacturing could be used to “print” very thin layers of highly conductive materials onto an elastomer surface. “With the development of additive manufacturing, direct writing techniques are showing up as an alternative to the traditional subtractive patterning methods,” the S&T researchers say. Subtractive approaches include photolithography, which is commonly used to manufacture semiconductors. The researchers see additive manufacturing as a relatively economical approach to creating these new devices. At Missouri S&T, they are testing an approach called “direct aerosol printing.” The process involves spraying a conductive material and integrating with a stretchable substrate to develop sensors that can be placed on skin. “With the increase of complexity and resolution of devices, higher requirements for patterning techniques are expected,” they write. “Direct printing, as an additive manufacturing method, would satisfy such requirements and offer low cost and high speed in both prototyping and manufacturing. It might be a solution for cost-effective and scalable fabrication of stretchable electronics.” Yet further challenges must be addressed before stretchable electronics become widely used as components in consumer electronics, medical devices or other fields, the researchers say. These challenges include the development of stretchable batteries that can store energy and the need to ensure that stretchable electronics and the malleable surfaces they’re built upon perform and age well together. Nevertheless, the researchers are optimistic for the future of stretchable electronics. They foresee a growth in the types of materials that could be used as efficient conductors of electricity and as flexible surfaces on which to build stretchable electronics.



Source: https://www.sciencedaily.com/releases/2017/01/170103135847.htm
 

 

Chemical Engineering

4.  Artificial Leaf Goes More Efficient for Hydrogen Generation

This is the newly-developed hetero-type dual photoelectrodes

A team of international researchers, affiliated with UNIST has recently engineered a new artificial leaf that can convert sunlight into fuel with groundbreaking efficiency. In the study, the research presented a hetero-type dual photoelectrodes, in which two photoanodes of different bandgaps are connected in parallel for extended light harvesting. Their new artificial leaf mimics the natural process of underwater photosynthesis of aquatic plants to split water into hydrogen and oxygen, which can be harvested for fuel. This study is expected to contribute greatly to the reduction and treatment of carbon dioxide emissions in accordance with the recent Paris Agreement on climate change. Because using hydrogen produced by artificial leaf as fuel, does not generate carbon dioxide emissions. In addition, it can be used as a cheap and stable hydrogen fuel for hydrogen fuel cell vehicles. Just like any other plants, marine plants also generate energy from the sun through photosynthesis. However, it is difficult to receive the full sunlight deep under the sea. Therefore, they are subjected to various types of photosynthesis that selectively utilize wavelengths reaching their depths. “We aim to achieve 10% enhanced light harvesting efficiency within three years,” says a researcher. “This technology will greatly contribute to the establishment of the renewable-energy-type hydrogen refueling station by supplying cheap fuel for hydrogen fuel cell vehicles.



Source: https://www.sciencedaily.com/releases/2017/01/170104103549.htm
 

 

Electrical Engineering

5. GaN-on-Silicon for Scalable High Electron Mobility Transistors

This is a GaN on 200 mm Si wafer thickness mapping image.

A team of researchers at the University of Illinois at Urbana-Champaign has advanced gallium nitride (GaN)-on-silicon transistor technology by optimizing the composition of the semiconductor layers that make up the device. Working with industry partners Veeco and IBM, the team created the high electron mobility transistor (HEMT) structure on a 200 mm silicon substrate with a process that will scale to larger industry-standard wafer sizes. Can Bayram, an assistant professor of electrical and computer engineering (ECE), and his team have created the GaN HEMT structure on a silicon platform because it is compatible with existing CMOS manufacturing processes and is less expensive than other substrate options like sapphire and silicon carbide. However, silicon does have its challenges. Namely, the lattice constant, or space between silicon atoms, doesn’t match up with the atomic structure of the GaN grown on top of it. “When you grow the GaN on top, there’s a lot of strain between the layers, so we grew buffer layers [between the silicon and GaN] to help change the lattice constant into the proper size,” a researcher. Without these buffer layers, cracks or other defects will form in the GaN material, which would prevent the transistor from operating properly. Specifically, these defects — threading dislocations or holes where atoms should be — ruin the properties of the 2-dimensional electron gas channel in the device. This channel is critical to the HEMTs ability to conduct current and function at high frequencies. “The single most important thing for these GaN [HEMT] devices is to have high 2D electron gas concentration,” said a researcher, about the accumulation of electrons in a channel at the interface between the silicon and the various GaN-based layers above it. “The problem is you have to control the strain balance among all those layers — from substrate all the way up to the channel — so as to maximize the density of the of the conducting electrons in order to get the fastest transistor with the highest possible power density.” After studying three different buffer layer configurations, the research team discovered that thicker buffer layers made of graded AlGaN reduce threading dislocation, and stacking those layers reduces stress. With this type of configuration, the team achieved an electron mobility of 1,800 cm2/V-sec. “The less strain there is on the GaN layer, the higher the mobility will be, which ultimately corresponds to higher transistor operating frequencies,” said another researcher leading the scaling of these devices for 5G applications. The next step for the team is to fabricate fully functional high-frequency GaN HEMTs on a silicon platform for use in the 5G wireless data networks. When it’s fully deployed, the 5G network will enable faster data rates for the world’s 8 billion mobile phones, and will provide better connectivity and performance for Internet of Things (IoT) devices and driverless cars.



Source : https://www.sciencedaily.com/releases/2017/01/170109113756.htm
 

 

Electronics and Communication Engineering

6. Telecommunications Light Amplifier Could Strengthen Integrity of Transmitted Data

These are optical signals propagating through a USRN waveguide undergo 42.5dB of optical parametric amplification.

Imagine a dim light which is insufficiently bright enough to illuminate a room. An amplifier for such a light would increase the brightness by increasing the number of photons emitted. Photonics researchers have created such a high gain optical amplifier that is compact enough to be placed on a chip. The developed amplifier, when used within an optical interconnect such as a transceiver or fiber optic network, would help to efficiently increase the power of the transmitted light before it is completely depleted through optical losses. Besides having the potential to replace bulky, expensive amplifiers used today for the study of attosecond science and ultrafast optical information processing, the newly developed nanoscale-amplifier also provides a critical element to the optical interconnects toolkit, potentially providing regenerative amplification in short to long range interconnects. This work was a collaborative effort between researchers at the Singapore University of Technology and Design (SUTD), A*STAR Data Storage Institute and the Massachusetts Institute of Technology. “We have developed an optical amplifier which is able to amplify light by 17,000 times at the telecommunications wavelength,” said a researcher at SUTD who led the development of the amplifier. “We use a proprietary platform called ultra-silicon-rich nitride, with a material composition of seven parts silicon, three parts nitrogen, with the large nonlinearity and photon efficiency needed for high gain amplification, through the efficient transfer of photons from a pump to the signal. To give a sense of the scale, a conventional optical parametric amplifier costs several hundred thousand dollars, and occupies an entire optical table, while the newly developed amplifier is much smaller than a paper clip, and costs a fraction of the former.” Providing high gain on such a small footprint could enable new opportunities in low cost broadband spectroscopy, precision manufacturing and hyperspectral imaging. The device’s efficiency is also revealed through cascaded four wave mixing, which is a higher order mixing of the amplified and converted photons. This phenomenon also allows the amplifier to operate as a tunable broadband light source, enabling cheaper and more efficient spectroscopic sensing and molecular fingerprinting than what is available today. “The inefficiencies in highly nonlinear photonic devices are overcome here, by photonic device engineering for maximum nonlinearity, while still maintaining a sufficiently large bandgap to eliminate two-photon absorption at the telecommunications wavelength. We believe this is one of the highest gains demonstrated at the telecommunications wavelength to date on a CMOS chip” said a researcher. Achieving ultra-large amplification while maintaining high compactness was possible because the researchers managed to design and implement an amplifier which operates simultaneously with a high nonlinearity and photon efficiency. In other platforms which are compatible with processes used in the electronics industry today, either the nonlinearity or photon efficiency is low. “The results demonstrate the ultra-silicon-rich nitride platform to be extremely promising for highly efficient nonlinear optics applications, particularly in the field of CMOS photonics leveraging existing electronics infrastructure,” says a Scientist at the A*STAR Data Storage Institute.



Source: https://www.sciencedaily.com/releases/2017/01/170105123047.htm
 

 

Aerospace Engineering

7. New Simulation Software Improves Helicopter Pilot Training

Missions at sea, in mountainous regions or close to skyscrapers are extremely risky for helicopter pilots. The turbulent air flows near oil rigs, ships, cliffs and tall buildings can throw a helicopter off balance and cause a crash. To provide pilots with optimal preparation for these challenging conditions, engineers at the Technical University of Munich (TUM) are developing new simulation software. Providing helicopter pilots with the best possible preparation for extreme situations: That is the goal of the new simulation software being developed by researchers working at TUM’s Chair of Helicopter Technology. For the first time, real-time computational analysis will be implemented for both fluid mechanics and flight dynamics. “Until now, flight simulators have not adequately reflected the reality of flying in close proximity to large objects,” says Dr. Juergen Rauleder. “The problem is that, when it comes to wind conditions and the response of the helicopter, existing programs follow a rigid pattern. That means that local variations and changing conditions are not taken into account – unless the entire flow environment is known in advance.” But it is the unforeseen air flows that can be the most treacherous: For example, a moving ship causes air turbulence and sudden local shifts in wind speed known by specialists as “ship airwake flow”. It changes continually through wave action and fluctuating inflow conditions. In addition, turbulence occurs near the deck, the bridge and other ship structures. As a helicopter approaches the ship, there is interference between these air currents and the flow produced by the rotors. Conditions near a mountain slope or next to high buildings are similarly complicated. In all of these cases, the helicopter’s flight characteristics are influenced by complex and overlapping aerodynamic effects. zealing with those situations takes a lot of skill and practice, both of which can currently be acquired only through on-the-job training. To become adept at landing on a ship in heavy seas, for example, a student pilot has to repeat this tricky situation dozens of times with an experienced flight instructor. That’s the only way to gain the necessary experience to compensate for the complex interplay of air flows through perfectly timed adjustments to the pitch of the rotor blades. “Conventional training is expensive, risky and very stressful for student pilots. It also imposes heavy demands on the aircraft: Because the first attempts usually result in rather hard landings, the dampers and landing gear take quite a beating,” explains Rauleder. His team has now developed a simulation program that combines flow mechanics and flight dynamics in real time: “The numerical model is extremely flexible and does not depend on stored flow data. We only have to enter the external conditions such as topography, global wind speeds and the helicopter type. During the simulation, our algorithms use that data to continuously compute the interacting flow field at the virtual helicopter’s current location,” the engineer explains. The new program also lets pilots instantly “feel” the impact of the local air flows on the helicopter. This allows them to try out the effects of their control movements in a stress-free situation: perfect preparation for a soft landing that is easy on the aircraft. The TUM researchers have successfully validated the new real-time simulation with established reference models. All that is left to do is the biggest test of all: the reality check. The specialists have measured air flows on a ship using hundreds of sensors. To check the flight dynamics, the team will also be using in-flight data collected by the German Aerospace Center (DLR). “The validation of the models and testing of our simulation environment by experienced pilots in our research simulator is enormously important for our developments,” says Rauleder. “That’s the only way we can ensure that the simulator training provides student pilots with optimal preparation for tough missions.”



Source : http://phys.org/news/2016-12-simulation-software-helicopter.html
 

 

Mining, Metallurgical and Materials Engineering

 

8.  A Wolverine-Inspired Material

Illustration showing self-healing via ion-dipole interaction.

Scientists, including several from the University of California, Riverside, have developed a transparent, self-healing, highly stretchable conductive material that can be electrically activated to power artificial muscles and could be used to improve batteries, electronic devices, and robots. The findings represent the first time scientists have created an ionic conductor, meaning materials that ions can flow through, that is transparent, mechanically stretchable, and self-healing. The material has potential applications in a wide range of fields. It could give robots the ability to self-heal after mechanical failure; extend the lifetime of lithium ion batteries used in electronics and electric cars; and improve biosensors used in the medical field and environmental monitoring. This project brings together the research areas of self-healing materials and ionic conductors. Inspired by wound healing in nature, self-healing materials repair damage caused by wear and extend the lifetime, and lower the cost, of materials and devices. Ionic conductors are a class of materials with key roles in energy storage, solar energy conversion, sensors, and electronic devices. Another author of the paper previously demonstrated that stretchable, transparent, ionic conductors can be used to power artificial muscles and to create transparent loudspeakers — devices that feature several of the key properties of the new material (transparency, high stretchability and ionic conductivity) — but none of these devices additionally had the ability to self-heal from mechanical damage. The key difficulty is the identification of bonds that are stable and reversible under electrochemical conditions. Conventionally, self-healing polymers make use of non-covalent bonds, which creates a problem because those bonds are affected by electrochemical reactions that degrade the performance of the materials. The researchers helped solve that problem by using a mechanism called ion-dipole interactions, which are forces between charged ions and polar molecules that are highly stabile under electrochemical conditions. They combined a polar, stretchable polymer with a mobile, high-ionic-strength salt to create the material with the properties the researchers were seeking. The low-cost, easy to produce soft rubber-like material can stretch 50 times its original length. After being cut, it can completely re-attach, or heal, in 24 hours at room temperature. In fact, after only five minutes of healing the material can be stretched two times its original length. They demonstrated that the material could be used to power a so-called artificial muscle, also called dielectric elastomer actuator. Artificial muscle is a generic term used for materials or devices that can reversibly contract, expand, or rotate due to an external stimulus such as voltage, current, pressure or temperature. The dielectric elastomer actuator is actually three individual pieces of polymer that are stacked together. The top and bottom layers are the new material, which is able to conduct electricity and is self-healable, and the middle layer is a transparent, non-conductive rubber-like membrane. The researchers used electrical signals to get the artificial muscle to move. So, just like how a human muscle (such as a bicep) moves when the brain sends a signal to the arm, the artificial muscle also reacts when it receives a signal. Most importantly, the researchers were able to demonstrate that the ability of the new material to self-heal can be used to mimic a preeminent survival feature of nature: wound-healing. After parts of the artificial muscle were cut into two separate pieces, the material healed without relying on external stimuli, and the artificial muscle returned to the same level of performance as before being cut.



Source : https://www.sciencedaily.com/releases/2016/12/161225231953.htm
 

 

Energy Engineering 

9. Researchers Solve Mystery that was Holding Back Development of Next-Generation Solar Cells

Scientists have identified an unexpected cause of poor performance in a new class of flexible and cheap solar cells, bringing them closer to market. Solar cells are the building blocks of photovoltaic solar panels. They are made from light-absorbing materials that convert sunlight into electricity. Normally the light-absorbing material is silicon, which has an energy-intensive manufacturing process. In the new study, scientists looked at solar cells made from materials known as perovskites. These can be produced cheaply from chemicals mixed into printable or sprayable ink, which then crystallises to form light-absorbing films.
However, perovskite films contain charged defects that are likely to impair their performance. Slow movement of these defects is thought to be responsible for a process known as hysteresis, which leads to irregularities in the efficiency with which light is converted to electrical current. Light-generated electricity exits the solar cell in the form of electrons to be harnessed. This is done via ‘contacts’ that sandwich the light-absorbing film. Previously, scientists have managed to remove hysteresis by using more ‘selective’ contact materials that ensure a one-way flow of electrons out of the solar cell. In theory, changing these contact materials shouldn’t have any effect on the movement of the charged defects within the perovskite, so it has remained a mystery why this appeared to ‘fix’ the hysteresis problem. Now researchers from Imperial College London and collaborators have developed new experiments to follow which direction electrons move in the solar cell when they are generated with a short pulse of light. They found that the mobile charged defects are still present even in solar cells with very efficient contact materials, despite these cells showing no hysteresis. Hysteresis was only found when cells suffered the combined effects of both the defects and poor selectivity at the contacts. The researchers said: “The field has made amazing progress, and we’re on the right track by reducing problems with the contacts. However, the results also show that improving the contacts is only part of the solution, and we still need to be concerned about the charged defects moving inside the perovskite.” The charged defects may provide a chemical weak point which could lead to the eventual degradation of the perovskite film. This raises a potential concern over the solar cells’ long term stability. The researcher said: “The new techniques we have designed will allow the community to assess the extent of charged defect movement to help the future research needed to improve the stability and bring this technology to market.” Now that the causes of hysteresis have been uncovered, there are a few challenges that must be overcome before perovskite solar cells can be commercialized. One concern with current perovskites is that they contain small amounts of lead in their chemical structure. A replacement metal will probably have to be found before they are deemed safe at larger scales. Scientists will also have to reproduce their laboratory results with life-sized solar panels. However, the crucial challenge will be to find a way of improving the long-term stability of the perovskite materials.



Source : https://techxplore.com/news/2016-12-mystery-next-generation-solar-cells.html
 

 

Interdisciplinary Engineering and Special Fields

10. Implantable Microrobots: Innovative Manufacturing Platform Makes Intricate Biocompatible Micromachines

Fabrication and complete assembly of a Geneva drive device using the iMEMS method. The left panel shows the layer-by-layer fabrication of support structures and assembly of gear components. The image on the right shows the complete device after the layers have been sealed.

A team of researchers led by Biomedical Engineering Professor Sam Sia at Columbia Engineering has developed a way to manufacture microscale-sized machines from biomaterials that can safely be implanted in the body. Working with hydrogels, which are biocompatible materials that engineers have been studying for decades, Sia has invented a new technique that stacks the soft material in layers to make devices that have three-dimensional, freely moving parts. The study demonstrates a fast manufacturing method Sia calls “implantable microelectromechanical systems” (iMEMS). By exploiting the unique mechanical properties of hydrogels, the researchers developed a “locking mechanism” for precise actuation and movement of freely moving parts, which can provide functions such as valves, manifolds, rotors, pumps, and drug delivery. They were able to tune the biomaterials within a wide range of mechanical and diffusive properties and to control them after implantation without a sustained power supply such as a toxic battery. They then tested the “payload” delivery in a bone cancer model and found that the triggering of release of doxorubicin from the device over 10 days showed high treatment efficacy and low toxicity, at 1/10 of the standard systemic chemotherapy dose. Most current implantable microdevices have static components rather than moving parts and, because they require batteries or other toxic electronics, have limited biocompatibility. “Hydrogels are difficult to work with, as they are soft and not compatible with traditional machining techniques,” says a researcher. “We have tuned the mechanical properties and carefully matched the stiffness of structures that come in contact with each other within the device. Gears that interlock have to be stiff in order to allow for force transmission and to withstand repeated actuation. Conversely, structures that form locking mechanisms have to be soft and flexible to allow for the gears to slip by them during actuation, while at the same time they have to be stiff enough to hold the gears in place when the device is not actuated. We also studied the diffusive properties of the hydrogels to ensure that the loaded drugs do not easily diffuse through the hydrogel layers.” The team used light to polymerize sheets of gel and incorporated a stepper mechanization to control the z-axis and pattern the sheets layer by layer, giving them three-dimensionality. Controlling the z-axis enabled the researchers to create composite structures within one layer of the hydrogel while managing the thickness of each layer throughout the fabrication process. They were able to stack multiple layers that are precisely aligned and, because they could polymerize a layer at a time, one right after the other, the complex structure was built in under 30 minutes. Sia’s iMEMS technique addresses several fundamental considerations in building biocompatible microdevices, micromachines, and microrobots: how to power small robotic devices without using toxic batteries, how to make small biocompatible moveable components that are not silicon which has limited biocompatibility, and how to communicate wirelessly once implanted. The researchers were able to trigger the iMEMS device to release additional payloads over days to weeks after implantation. They were also able to achieve precise actuation by using magnetic forces to induce gear movements that, in turn, bend structural beams made of hydrogels with highly tunable properties. In collaboration with an orthopaedic surgeon at Columbia University Medical Center, the team tested the drug delivery system on mice with bone cancer. The iMEMS system delivered chemotherapy adjacent to the cancer, and limited tumour growth while showing less toxicity than chemotherapy administered throughout the body. “These microscale components can be used for microelectromechanical systems, for larger devices ranging from drug delivery to catheters to cardiac pacemakers, and soft robotics,” notes Sia. “People are already making replacement tissues and now we can make small implantable devices, sensors, or robots that we can talk to wirelessly.



Source : https://www.sciencedaily.com/releases/2017/01/170104145738.htm

 
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