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Direct Optical Visualization Of Graphene On Transparent Substrates

96 Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:Calibri; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;} The ∼10% optical contrast of graphene on specialized substrates like oxide-capped silicon substrates, together with the high-throughput and noninvasive features of optical microscopy, have greatly facilitated the use and research of graphene research for the past decade.  However, substantially lower contrast is obtained on transparent substrates. Visualization of nanoscale defects in graphene, e.g., voids, cracks, wrinkles, and multilayers, formed during either growth or subsequent transfer and fabrication steps, represents yet another level of challenge for most device substrates.     UC Berkeley researchers have developed a facile, label-free optical microscopy method to directly visualize graphene on transparent inorganic and polymer substrates at 30−40% image contrast per graphene layer.  Their noninvasive approach overcomes typical challenges associated with transparent substrates, including insulating and rough surfaces, enables unambiguous identification of local graphene layer numbers and reveals nanoscale structures and defects with outstanding contrast and throughput. We thus demonstrate in situ monitoring of nanoscale defects in graphene, including the generation of nano-cracks under uniaxial strain, at up to 4× video rate.  

Finite-State Machines For DNA Information Storage

DNA can store petabytes of information per gram and can last intact for tens of thousands of years.  This makes it an appealing prospect for long-term archival storage.  However, DNA synthesis, sequencing, and replication are prone to errors, which limit its potential as a storage medium.  These errors can be controlled by applying the tools of information theory, treating DNA storage as a noisy channel coding problem.  Several coding schemes for DNA storage have been proposed that address the interrelated issues of error avoidance, error correction and redundancy.  There are currently no schemes that address all the above.    Researchers at UC Berkeley have combine some of these ideas, and introduced new ones, using a modular strategy for code design.  With this method, codes can be assembled to meet requirements including error-avoidance, error-correction (resistant to corruption of the information by substitutions, insertions, duplications, or deletions that are introduced during sequencing or replication of the DNA), and demarcation of metadata.  The DNA generated by the codes is free of short local repeats and other (foldback) structure.  The codes generated by this method are flexible in that they arise by systematic combination of state machines, each machine formally representing a particular transformation of the input sequence.  So, for example, one state machine might be used to introduce a "watermark" signal that helps protect against insertion/deletion errors; another state machine could be used to convert the binary sequence into a ternary sequence (or mixed-radix sequence); another state machine would convert the ternary or mixed-radix sequence into a non-repeating DNA sequence; and another state machine to model the errors that are introduced during sequencing. 

Low-variability, Self-assembled Monolayer Doping Methods

Semiconductor materials are fundamental materials in all modern electronic devices. Continuous demand for faster and more energy-efficient electronics is pushing miniaturization and scaling to unprecedented levels. Controlled and uniform doping of semiconductor materials with atomic accuracy is critical to materials and device performance. In particular, junction depth and dopant concentration need to be tightly controlled to minimize contact resistance, as well as variability effects due to random dopant fluctuations in the channel. Conventional doping methods such as ion implantation is imprecise and can have large variability effect. Moreover, energetic introduction of dopant species will often cause crystal damage, leading to incompatibility with nanostructured-materials and further performance degradation. To address these problems, researchers at the University of California, Berkeley, have experimented with an alternative approach to a wafer-scale surface doping technique first developed at the UC Berkeley in 2007. The team has demonstrated a controlled approach for monolayer doping (MLD) in which gas phase dopant-containing molecules form low-variability, self-assembled monolayers (SAM) on target semiconductor surfaces.

Universal Coating Compound

Polydimethyl siloxane (PDMS) has many characteristics that make it the most popular candidate for producing organ-on-a-chip devices or mirco-physiological systems (MPS) devices. After crosslinking, PDMS has shown to be biologically compatible and amenable to many standard cell culture techniques due to it’s transparency, oxygen permeability, and low auto-fluorescence. However, due to PDMS’s hydrophobicity, molecules that are also hydrophobic partition into the PDMS to produce unpredictable concentrations in cell and media channels making it impossible to predict the actual dosing concentrations for drug investigations. This unpredictability is an obstacle for using organ-on-a-chip devices as screens for drug candidates in discovery stages.   Researchers at UC Berkeley have developed a simple coating procedure that allows the formation of substrate independent (universal) coatings. The researchers identified a novel compound able to form stable coatings that outperformed existing dip-coating precursor molecules in their ability to prevent absorbance of small molecules into a variety of organic and inorganic polymers, such as PDMS. 

Nanostructured Metal Oxide Sensing Film From Liquid Precursor

Nanostructured metal oxide materials have generated much interest for sensing applications due to their high surface area, low thermal mass, and superior performance.  However, stable and reproducible integration of these materials into a functional sensor is difficult. Vacuum deposition techniques such as sputtering or evaporation do not offer substantial sensing performance improvement. Sacrificial templating steps have been suggested, but the manufacturing complexity and cost are not suitable for high volume production. There remains a need for a simple, effective method to prepare nanostructured metal oxide films for low power, miniaturized gas sensors with high sensitivity.   Researchers at UC Berkeley have developed a novel method for creating highly porous, nanostructured metal oxide film in a controlled location from a liquid precursor using a localized heat source. This method eliminates processing steps, such as the need to separately synthesize nanomaterials and suspend them into a stable ink for deposition. The localized heat source acts to both evaporate the solvent and thermally decompose the precursor into a highly porous film of nanocrystalline metal oxide, as well as to define the location of the formed film. The utility of this method has been demonstrated for the formation of a tin oxide gas sensor with superior performance, including high sensitivity and fast response and recovery time for carbon monoxide gas. However, the method could be useful for other applications that require localized formation of a porous film of nanocrystalline metal oxide.   

An Ultra-Sensitive Method for Detecting Molecules

To-date, plasmon detection methods have been utilized in the life sciences, electrochemistry, chemical vapor detection, and food safety. While passive surface plasmon resonators have lead to high-sensitivity detection in real time without further contaminating the environment with labels. Unfortunately, because these systems are passively excited, they are intrinsically limited by a loss of metal, which leads to decreased sensitivity. Researchers at the University of California, Berkeley have developed a novel method to detect distinct molecules in air under normal conditions to achieve sub-parts per billion detection limits, the lowest limit reported. This device can be used detecting a wide array of molecules including explosives or bio molecular diagnostics utilizing the first instance of active plasmon sensor, free of metal losses and operating deep below the diffraction limit for visible light.  This novel detection method has been shown to have superior performance than monitoring the wavelength shift, which is widely used in passive surface plasmon sensors. 

Low Capacitance/High Speed Bipolar Phototransistor

The performance of optoelectronic links is very strongly related to the sensitivity of the detector on the receiver end. Conventional receivers include a photodiode whose signal is sent to amplifiers until it is strong enough to be used in microelectronic circuits. The energy cost of amplification is very high and could be significantly reduced if the capacitance of the photodiode and first stage of amplification were smaller. In order to be useful for this application, a phototransistor must have several features: - Low capacitance - High speed - Large photon absorption volume Unfortunately, for conventional bipolar phototransistors, these requirements are contradictory. Indeed the photon absorption length in typical semiconductors is on the order of microns, while the speed requirement only allows transit regions for amplified carriers of a few tens of nanometers at best. This is over a 100x size mismatch. Increasing any other dimension (that is not the transit direction) results in prohibitively high capacitances. This invention offers a solution to these issues consisting of a new kind of semiconductor phototransistor device, which integrates a large PIN-photodiode with a bipolar junction transistor (or Heterojunction Bipolar transistor). 

Stimuli-Sensitive Intrinsically Disordered Protein Brushes

Recent advances in biomedicine and biotechnology are driving the demand for novel surface functionalization platforms for biologically active molecules. Polymer brush coatings form when macromolecular chains are end-tethered to surfaces at high grafting densities. While there have been notable successes integrating polymer brush coatings with proteins to control biological function, such strategies require covalent conjugation of the protein to the polymer, which can be inefficient and can compromise biological function. Moreover, these polymer brushes almost universally feature synthetic polymers, which are often heterogeneous and do not readily allow incorporation of chemical functionalities at precise sites along the constituent chains. To address these challenges, Researchers at the University of California, Berkeley (UCB) conducted experiments with polymer brushes based on nerve cell neurofilaments as the intrinsically disordered protein (IDP). By cloning a portion of a gene that encodes one of the neurofilament bristles, and re-engineering it such that they could attach the resulting protein to surfaces, UCB investigators have developed a biomimetic, recombinant IDP that can assemble into an environment-sensitive protein brush that swells and collapses dramatically with environmental changes in solution pH and ionic strength. Their research demonstrates that stimuli-responsive brushes can be efficiently integrated with proteins without compromising biological function, which could have broad commercial appeal as a new class of smart biomaterial building blocks.

Stimuli Responsive Based Digital Biosensors For The Measurement Of Oxidative Stress

Oxidative stress and reactive oxygen species (ROS) are the hallmarks of many disorders, including drug-associated toxicity, atherosclerosis, cancer, and degenerative processes associated with aging. Routine monitoring of circulating ROS in a point-of-care (POC) manner would reduce morbidity and mortality. However, current methods for measuring oxidative stress and lipid peroxidation rely on label-based fluorescence transduction methods for optical detection. This is laborious, lengthy and requires accurate optical instrumentation. It is also expensive and difficult to miniaturize, making it impractical for POC use in low-resource settings. Developing electrochemical biosensors for POC applications has been challenging due to the difficulties in combining the query biomolecule receptor with an electrical transducer to produce an electrical signal in presence of the query biomolecule for a simple, accurate and inexpensive platform for patient diagnosis.Investigators at UC Berkeley have met this challenge with the ROSchip innovation. ROSchip is an oxidative stress digital biosensor, a lab-on-a-chip device which has a novel stimuli responsive polymer for early detection of circulating ROS in blood. The ROSchip’s data provides accurate management of cardiovascular and atherosclerosis diseases in routine clinical practices. Circulating lipid hydroperoxides (LPH), the primary biomarkers of lipid oxidation, predict cardiovascular events in patients with a history of cardiovascular disease. The ROSchip provides accurate, cost-effective, and fast assessment and monitoring of LPH. The ROSchip system is designed with interdigitated electrodes coated with a thin film of ROS-responsive polymer. The ROS generates an electrical signal indicating LPH present in a sample. 

Methods for Electrospun Fibrous Scaffolds

Controlling the structure and organization of electrospun fiber is desirable for fabricating scaffolds and materials with precise microstructures for use in textile, filtering materials, wound healing, drug delivery, and tissue engineering. Manufacturing by electrospinning templates for controlling the microstructure architecture is inherently complicated and non-dynamic, and typically slow and expensive. Moreover, conventional electrospinning techniques are prone to mechanical instabilities, including distortion, shrinkage, and delamination or pore collapse. To help solve these problems, researchers at Berkeley created methods and technology to control fiber deposition in electrospinning using unique microfabrication means. In one instance, investigators performed an animal study with electrospun scaffolds to assess collagen deposition in histologic cross sections of spun scaffolds. Early data results related to the new materials and structures suggest superior fiber organization, porosity, biocompatibility, and biological performance properties, which may have broad industrial applications, from materials microfabrication to clinical therapies.

System And Methods For Fabricating Boron Nitride Nanostructures

A research team led by Alex Zettl has developed a variable pressure, powder/gas/liquid injection inductively coupled plasma system that is used to produce high quality boron nitride nanotubes (BNNTs) at continuous rates of 35 g/hour.  For example, in this system, boron powder is introduced to a directed flow of plasma and boron nitride nanostructures are formed in a chamber. This system can produce collapsed BN nanotubes (nanoribbons) and closed shell BN capsules (nanococoons).  The system is also adaptable to a large variety of feedstock materials.

Methods to Produce Ultra-Thin Copper Nanowires for Transparent Conductors

The disclosure provides innovative synthesis methods to produce uniform, ultrathin and high-quality metal nanostructures. In certain embodiments, the synthesis methods disclosed herein are solution based, therefore affording scalability and allowing for the production of metal nanostructures (e.g. Cu-nanowires ) that can have varying diameters, e.g., between 1 nm to 70 nm. The resulting metal nanostructures can be used to construct transparent electrodes that have lower costs, better transparency, and superior flexibility in comparison to conventional metal-oxide conductors, such as indium tin oxide (ITO) .

Functional Graphene Nanostructure Devices From Polymers

The rapid expansion of data-intensive information technology has highlighted the urgent need for a successor to the silicon based complementary metal-oxide-semiconductor (CMOS) integrated circuit (IC) architecture to continuously improve the performance of digital data management. Over the last decade, the evolution of scaling of dimensions, energy efficiency, and processor speed has slowed significantly due to the limitations imposed by a photolithographic top-down approach and the limited control of inorganic semiconductor material properties at sub-10nm dimensions. Carbon-based low-dimensional materials may aid problems with transistor scaling, speed, and energy efficiency for future IC generations. To help address these needs, researchers at the University of California, Berkeley, have developed unique heterostructures based on innovative graphene nanoribbon (GNR)-based materials and methods. These structures are chemically synthesized from the bottom up using rational polymerization methods, producing GNRs with uniform sub-5nm widths and with atomically precise edges. This approach shows promise towards producing GNRs of identical molecular structure in bulk.

Hybrid Porous Nanowires for Electrochemical Energy Storage

Supercapacitors are attractive energy storage devices due to their high-power capabilities and robust cycle lifetimes.   “Super” capacitors are named in part because the electrodes are composed of materials with high specific surface area and the distance between the electrode and electrochemical double layer is very small compared to standard capacitors.  A variety of porous silicon nanowires have been developed for use as supercapacitors electrodes by maximizing the specific surface area of active materials.  Although the use of Si is attractive due to its wide-spread adoption by microelectronics industry and due to its abundance, Si nanowires are highly reactive and dissolve rapidly when exposed to mild saline solutions.  Previously, silicon carbide thin films were used to protect the porous silicon nanowires, but the coatings were 10’s of nm thick and while they successfully mitigated Si degradation during electrochemical cycling in aqueous electrolytes, they also resulted in pore blockage and a large decrease in energy storage potential.   Researchers at UC Berkeley have developed methods and materials to improve porous silicon nanowires by overcoming the above limitations.  The resulting nanowires have an ultrathin carbon coating preserving the pore structure while mitigating Si degradation.  The resulting supercapacitor electrodes have the highest capacitance (and hence energy storage) per projected area to date.   

Flexible Porous Aluminum Oxide Films

Ceramic materials are widely used because of their strength, dielectric properties, and ability to withstand high temperatures.  Ceramics can withstand a great deal of compressional stress; however, because ceramic materials are brittle and inflexible, they fracture under stress like glass and shatter if bent.  Flexible ceramic membranes combine the attributes of the high strength of ceramic materials with the elasticity of polymers, however, many of these materials are composite materials which have drawbacks in that the non-ceramic material is part of the film and cannot withstand high temperatures and are flammable.   UC Berkeley investigators have developed a reproducibly flexible porous aluminum oxide film that can be bent with a radius of curvature exceeding 0.2 mm.  These flexible porous aluminum oxide films are more robust and can withstand greater mechanical abuse.  The material can also stretch elastically the same amount as comparable porous polypropylene films, while withstanding over 100 times the external pressure and higher temperatures.   

Self-doping materials for solution-processed organic n-type thermoelectrics

Organic thermoelectrics have become a major part of the electronics industry in the last 25 years, spurred by the shortcomings of inorganic semiconductors. Organic semiconductors offer greater ease in substrate compatibility, device processability, flexibility, large area coverage, and reduced cost; as well as facile tuning of the frontier molecular orbital energies by molecular design. Building efficient thermoelectric architectures requires both high performance p-type and n-type materials. Although the thermoelectric performance of p-type organic materials is rapidly advancing, the performance of n-type organic electronic materials has not benefitted from the same level of innovation. The design of n-type organics has proven challenging, and thermoelectric studies of organic n-type systems are scarce. Consequently, very few materials have been identified as n-type organic thermoelectrics that exhibit high thermoelectric performance and are amenable to solution-processing. Berkeley researchers have discovered a promising molecular design strategy for self-doping n-type organic materials with enhanced thermoelectric performance. The resulting materials have demonstrated the highest n-type thermoelectric performance of solution-processed organic materials reported to date. This novel molecular design strategy can be coupled with other external doping strategies for additional tuning of thermoelectric properties.

Piezoelectric Voltage Transformer For Low Voltage Transistors

Power consumption is increasingly critical for modern electronics.  In the past, transistor voltage reduced with shrinking size, but in recent years the voltage scaling has stopped.  At the end of the transistor roadmap, the operating voltage is projected to be reaching just 0.4 V. To reduce the voltage below this floor value, the transistor needs to be reinvented. To help overcome these challenges, investigators at UC Berkeley have developed unique techniques and devices that could break through the voltage floor, significantly reducing chip operating voltage by several times, and improve power consumption by at least an order of magnitude. The results offer a simple approach for preparing nanoscale piezoelectric voltage transformers that can be fabricated with each individual transistor for revolutionary advances in low-voltage transistor technologies.

Highly Responsive PMUT

Ultrasonic imaging is one of the most important and widely used medical imaging techniques, which uses high-frequency sound waves to view soft tissues such as muscles, internal organs as well as blood flowing through blood vessels in real time. With the advancement of microelectromechanical systems (MEMS), ultrasonic devices operated based on plate flexural mode have shown remarkable improvements in bandwidth, cost, and yield over the conventional thickness-mode PZT sensors. MEMS fabrication technologies can be utilized to realize both capacitive (cMUTs) and piezoelectric (pMUTs) micromachined ultrasonic transducers However, these devices could enjoy much more widespread applications if they were adjustable , better focused with lower energy requirements.   In response to this challenge, Investigators at University of California at Berkeley have developed innovative design and fabrication concept to make piezoelectric micromachined ultrasonic transducer (pMUT) based on a CMOS compatible fabrication process for the first time. The prototype device shows a resonant frequency in the MHz range with a DC displacement exceeding 1nm/V (more than one order of magnitude higher than typical pMUTs at similar frequencies). As such, this new class of pMUTs has the potential of replacing the state-of-art pMUTs for high electromechanical coupling ultrasonic transducer arrays.

Programmable Photo-Actuators And Motors Based On Carbon Nanotubes With Tuned Chirality Distributions

Programmable materials that change their shape and functionality in response to external stimuli represent a novel class of materials that enable new applications. Previous work using shape memory polymers, thermal bimorphs, molecular motors and hydrogels are typically less practical due to slow response times and cost, and their actuations are often non-tunable and non-reversible. To meet these challenges, investigators at UC Berkeley have demonstrated highly versatile photoactuators, oscillators, and motors based on specialized polymer/single-walled carbon nanotube (SWNT) materials and structures, producing tunable, high-performance chromatic actuators. These new techniques and structures open up the use of SWCT and polymers for advanced photomechanical devices.

A Drift-Corrected, High-Resolution Optical Trap

Optical trapping systems are commercially available through several companies. In these systems, the optical trap precision relies on the passive stability of the instrument itself, and therefore demands costly engineering solutions to limit environmental noise that can be coupled into the optomechanical components. Consequently, high-resolution measurements are not possible in common biological laboratory settings that typically lack appropriate vibration isolation and temperature stability.  Researchers at the University of California, Berkeley have developed an invention that addresses a critical problem currently limiting the performance of high-resolution optical traps: that the mechanical drift of optical components often results in physical drift in the location of an optical trap that obscures the displacement-of-interest. The motion of biological motor proteins that are specific to interacting with DNA often take steps along the double helix that is on the order of 0.3 nanometers in size. Accurate measurement of displacements on this scale requires that drift of the trap positions be limited to no more than a few angstroms. However, the current best-performing optical traps suffer from instrumental drift that is almost twice what can be tolerated. Owing to the critical role of these components in all optical trapping systems, and the previously undetectable levels of mechanical drift they undergo, we sought to measure the trap drift with angstrom-level precision using a new approach. This new approach has successfully measured for and corrected for the mechanical drift of these components and demonstrated that this novel invention is capable of consistently reducing the noise floor to levels that have not previously been accomplished.       

Growth Factor Sequestering and Presenting Hydrogels

0 0 1 96 540 UC Berkeley 10 4 632 14.0 Normal 0 false false false EN-US JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:Cambria; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin;} The encapsulation of stem cells in a hydrogel substrate provides a promising future in biomedical applications. However, communications between hydrogels and stem cells is complicated, for example, factors such as porosity, different polymer types, stiffness, compatibility and degradation will lead to stem cell survival or death. Hydrogels mimic the three-dimensional extracellular matrix to provide a friendly environment for stem cells.   UC Berkeley researchers have developed hydrogel cell matrices for the support, growth, and differentiation of a stem cell or progenitor cell and methods for making such hydrogel cell matrices.

A Cavity-Based Atom Interferometer Inertial Sensor

Light-pulse atom interferometers (LALIs) are useful as inertial sensors, measuring acceleration and rotation. In addition to being extremely sensitive, LAIs show a highly accurate scale factor and stable baseline even without calibration, unlike classical sensors such as laser gyroscopes. Rotation sensing however, does not yet benefit fully from this stability.  In existing sensors, one of these dimensions for the enclosed area A is determined by the atoms’ initial velocity, a quantity known to relatively low precision. Moreover, all LAIs, including “compact” versions for inertial navigation, use beam splitters based on Raman transitions (which limit their sensitivity and introduces systematic effects), atomic fountains (which are ~1-m tall and must be carefully aligned with respect to the vertical), and free-beam optics (which limit available laser intensity and wavefront purity). To address these challenges, investigators at University of California at Berkeley have developed a cavity-based atom interferometer which overcomes these limitations.  This atom interferometer is provided a 40 cm optical cavity to enhance the available laser power, minimize wavefront distortions, and control other systematic effects symptomatic to atomic fountains.  This innovated system allows the production of LAI inertial sensors that simultaneously measures linear accelerations and rotations. The cavity-based interferometer offers the full performance of a large-scale atomic fountain within a small volume.  The cavity-based interferometer will surpass the baseline stability of current rotation sensors.  It will allow spatial separations between atomic trajectories comparable to larger scale fountains within a more compact device.

A Zero-Power, High Throughput Micro, Nanoparticle Printing Via Gravity-Surface Tension Mediated Formation Of Picoliter-Scale Droplets

Current approaches to print micro and nanoparticles are promising, but have serious limitations to commercial applications. These methods require high power consumption and have complicated and costly set-up. These systems are low-throughput, have limited pattern size and resolution-tunability, and difficult alignment. In response to these challenges, investigators at University of California at Berkeley have developed zero-power nanoparticle printing system. This system uses gravity and surface tension to generate and print picoliter-scale droplets for high-throughput, size-tunable printing of micro, nanoparticle assemblies. High-throughput, picoliter-scale droplets are printed by a single step, contact-transferring of the droplets through microporous nanomembrane of a printing head. Rapid evaporative self-assembly of the particles on a hydrophobic surface leads to printing a large array of various microparticles and nanoparticles assemblies of tunable sizes and resolutions. With this technology, continuous printing of single type particles and multiplex printing of various types of particles with accurate alignment are successfully performed. As a demonstration of this innovation, the investigators have produced size-tunable, uniform large arrays of gold nanoparticle assemblies for Surface Enhanced Raman Spectroscopy (SERS) are created. Strong and uniform (<10% variation) SERS signals were obtained and the signal is tunable by controlling the pattern sizes. Also, the superb uniformity of the printed patterns is demonstrated in a quantitative manner. This technology offers a straightforward, efficient methodology to manufacture nanophotonic and nanoelectrical devices in a controllable way with low power and material consumption.

Biocompatible And Biodegradable Microneedles Made From Silk

Although silk is commonly known as a fiber, dissolved silk protein has recently received significant attention for its use in creating biocompatible, biodegradable, and mechanically tough materials. These materials have been applied to tissue engineering, biosensors, and microfluidics. Reconstituted silk solutions present a promising alternative to polydimethylsiloxane (PDMS), currently the most commonly used material in micropatterning and soft lithography. However, it is not clear if this alternative can rectify the main problems associated with PDMS: the difficulty in replicating nano-scale features, and the inability of PDMS to support high aspect ratio structures (such as needles) without collapsing.Researchers at UC Berkeley have used reconstituted silk fibroin (RSF) to make microneedles, proving that RSF is an excellent material for molding of nano- and micro-scale patterned features. They demonstrated feature replication down to 25 nm, and the ability to support high aspect ratio structures up to 3.75 (height to diameter). Theoretical calculations suggest that silk films could support aspect ratios of up to 10. Furthermore, the researchers showed that the RSF films are in an alpha-helical/random coil water-soluble state, but can also be crystallized into a beta-sheet and water-insoluble conformation. Most importantly, they demonstrated the fabrication of silk microneedles that could be used in drug delivery and wound healing.

Biologically Inspired Self-Activated Building Envelope Regulation (Saber)

Throughout the world, there is a growing need for energy efficient housing solutions. The need is particularly strong in developing countries located in tropical climates, where the cost of energy used for temperature and humidity control is very high. As these climates are often prone to flooding, there is also a need for low-cost, energy efficient emergency housing. The bulk of energy is spent on compensating for heat and cooling losses that occur through the building envelope ? the outer shell of a building that protects the indoor environment. Most current building envelopes have separate controls for environmental flows such as humidity, cooling, and light transmission that lack precision and are difficult to calibrate. Climatic self-regulation of building envelopes that can reduce the need for artificial space conditioning is highly relevant to develop. Through a pioneering interdisciplinary collaboration between bioengineering and architecture, researchers at UC Berkeley developed a new sensor technology for external building membranes that can actively respond to environmental changes, and provide automated control of moisture and temperature. The system for Self-Activated Building Envelope Regulation (SABER) is inspired by new understanding of moisture barrier and heat transfer in plants. SABER utilizes optomechanical and hygrothermal sensor/actuator networks build onto a thin film membrane, which can replace the expensive and large mechanical control systems.

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