Nicholas A. Melosh - US grants

This CAREER project addresses mechanisms of voltage switching in molecular electronics and their extension to nanoscale opto-electronic devices. The approach is based upon coupling surface plasmons into molecular junctions. Through these experiments, optical and Raman spectra of molecular layers as a function of applied bias are directly observed. The measurements indicate whether mechanisms such as bond torsion, redox chemistry, or mechanical re-arrangements are responsible for bistable current-voltage (IV) switching. Additional activities will address integration of molecular electronic switches into nanoscale plasmon waveguides to control plasmon propagation. Metal-molecule metal waveguides for devices such as electro-optic modulators, optical memories and optical logic circuits will be fabricated and characterized. This research is expected to enhance design of molecules for specific electronic functions, and impact the development of smaller, lower-power consumption computing.
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The project addresses fundamental research issues in electronic/photonic materials science having technological relevance. In conjunction with the research component, this project will involve a substantial program of education and outreach. The PI will strive to provide exciting and valuable research opportunities for high school, undergraduate, and graduate students. These experiences will be an important supplement to classroom education. In cooperation with the Engineering Diversity Program at Stanford, he will work to attract underrepresented minority students through research opportunities. To enhance the education of local high school students, particularly within historically disadvantaged and underrepresented schools, he has committed to "Adopt a Class," bringing graduate students from Stanford with him into the classroom to give demonstrations and lectures several times a year. He will also integrate teaching and course development to include results from research, and aims to provide fundamental skills needed for successful careers in science and technology.
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Abstract (0556032)

We propose to develop an AFM-based nanowire tensile test apparatus together with an experimentally validated computational tool, to obtain fundamental understanding on the mechanical properties of nanowires. The proposal features close integration of theory and experiment to validate and illuminate the results in a manner that would not be possible from a single study alone. This tool set will be essential for a wide array of research and industrial fields with interests in nanowires and nanomaterials, including resonators, composites, nanofluidics, and electrical junctions.

The broader impact of this proposal includes establishing mechanical design guidelines for nanowires and providing a set of computational tools to calculate the behavior of nanowire devices and nanowire/metal interfaces in new applications. These tools will enable a wide range engineers and researchers to confidently implement nanowire designs, a key building block of nanotechnology. The educational plan include the development of a large-scale version of the AFM style tensile test and simplified version of computational codes, demonstrating the concepts of stress, strain, and AFM operation to high school and undergraduate students.

CBET-0827822
Melosh

Self-assembly at interfaces involves a delicate balance between charge, bonding strength, transport, and reversibility. External fields or non-uniform charge distributions can alter assembly behavior in surprising ways by accelerating, inhibiting or changing the assembly process. In particular, many molecular and biological species are themselves highly-charged systems which may also undergo significant conformational and electrostatic reconfiguration during reaction/assembly. This general problem of self-assembly in external fields and charge-redistribution during the assembly process has received little attention, yet is vital for the goals of top-down/bottom-up patterning or more traditional applications such as DNA microarrays and biosensors. This project will systematically measure how electric fields modulate self-assembly at interfaces, and develop a fully-vetted theoretical model. A new optical technique will be applied to monitor the spatial and temporal build-up of assembling species as well as the ionic double layer with single nanometer accuracy, providing new, quantitative information on the dynamics of highly charged species. In these experiments DNA serves as an ideal model system, as preliminary studies have shown that ionic strength and electric fields have some effect on assembly, but a complete theoretical model has not been established. DNA transport to the interface, hybridization, and melting kinetics will be studied as a function of length, potential field, mismatch locations, and charge density.

The intellectual merit of this project is to elucidate how electric fields and ion distributions affect self-assembly mechanisms. Fundamentally, this work will fill a void in our understanding of how highly-charged species interact and react at surfaces under an external bias. While small ion and colloidal behavior in external fields are well-established areas, self-assembly under electric fields, the tendency of monomer reconfiguration during assembly, and the effect of force distribution on DNA within field gradients have not been explored. Mean-field and Brownian dynamics theoretical models will be developed that can replicate the results of these experiments, providing deeper insight into their mechanism.

The broader impacts of this project include developing models to predict the hybridization and melting dynamics of DNA on surfaces, providing straight-forward error correction methods for nanomaterials assembly, educate graduate and undergraduate students, and to disseminate these findings. Development of new methods to control interfacial activity is important for separations, bio-fouling, DNA-array technology and coatings. A full understanding of the interplay between assembly and fields will allow design of pulse algorithms and conditions through which to greatly accelerate DNA hybridization while reducing mis-matches and cross-contamination, a critical problem for commonly used DNA microarrays, and can be implemented in a number of applications. These results will be widely shared with other researchers, foremost through development of a website with free public access to the codes and protocols used. In addition to scientific and technological impact, this proposal incorporates an educational outreach component as well. Undergraduate research, curriculum development, scientific professional development, and tutoring elementary school students are an integral part of the research program.

The Analytical and Surface Chemistry Program at NSF Division of Chemistry will support the international collaborative research project of Prof. Nicholas Melosh of Stanford University and Prof. Peter Schreiner of Justus-Liebig University Giessen. This international collaborative research project will examine the fundamental properties and applications of diamondoids, a newly discovered nanoscale form of carbon. Diamondoid molecules consist of 2-6 diamond cages fused together, combining both the remarkable properties of diamond with the uniformity and functionality of a nanomaterial. Profs. Melosh and Schreiner and their students will investigate how these materials can be chemically modified with high specificity, and determine how these molecular substituents affect electronic and structural behavior. Diamondoid properties ranging from dielectric constant, band gap, electron affinity, and energy level alignment will be measured using a combination of ultraviolet photoemission spectroscopy, field emission, microwave probes and electron tunneling. Diamondoids are unique model systems to examine how electronic structure develops in nanomaterials because they are molecularly pure, atomically uniform, and include a systematic sequence of sizes and shapes. Diamondoid thin films are expected to significantly impact technological applications involving electron emission, such as displays, based upon their similarity to hydrogen-terminated diamond. Field- and thermionic- electron emission from diamondoid surfaces will reveal how diamond and diamond-like structures enhance surface emission, which could lead to a new generation of robust displays and lighting.

This international collaborative research project is supported jointly by NSF and the Deutsche Forschungsgemeinschaft (DFG) in Germany. The study is also supported by the Office of International Science and Engineering (OISE) at NSF.

The Center for Probing the Nanoscale (CPN) addresses five overriding goals:

1.To develop novel probes that dramatically improve our capability to observe, manipulate, and control nanoscale objects and phenomena.

2.To educate the next generation of scientists and engineers regarding the theory and practice of these probes.

3. To apply these novel probes to answer fundamental questions and to shed light on technologically relevant issues.

4. To disseminate knowledge and to transfer technology so that other research scientists and engineers can make use of the advances, and so that corporations can manufacture and market the new novel probes.

5. To inspire thousands of middle school students by training their teachers at a Summer Institute.

The CPN includes thirteen core faculty-level Investigators (including three IBM Investigators who also serve as Consulting Professors at Stanford), twenty-eight affiliated faculty members and dozens of students and postdocs in eight academic departments: Applied Physics, Art and Art History, Electrical Engineering, Chemistry, Materials Science and Engineering, Mechanical Engineering, and Physics.

Research at the Center is focused on five Theme Groups:

Plasmonic Scanning Tunneling Microscopy. The plasmonic scanning tunneling microscope will perform spatially localized combined electronic and optical imaging and spectroscopy. The pivotal goal is to combine the exquisite spatial resolution inherent in high-resolution scanning tunneling microscopy and spectroscopy with the detailed information on high-frequency excitations of materials yielded by optical channels.

Nanoscale Electrical Imaging. Lithographically-patterned structures such as transistors now commonly have electronic properties that vary on scales of nanometers to tens of nanometers. The goal is to develop and apply a suite of techniques to measure electronic properties such as dielectric constant, conductivity, and carrier density of materials at the 10 nm scale, with sensitivity to variations deep beneath a sample surface.

Individual Nanomagnet Characterization. The volume, shape, and structure of magnetic nanoparticles lead to a number of present and proposed applications in biology and medicine. This theme will develop and advance a variety of nanoprobes with the spatial resolution and magnetic sensitivity to detect and characterize individual nanomagnets for nanobiotechnology applications

Nanoscale Magnetic Resonance. Recent work sponsored by CPN has proven that magnetic resonance force microscopy (MRFM) can achieve three dimensional imaging with spatial resolution below 10 nm. Research in the second five years will focus on extending MRFM resolution to below 1 nm - or roughly an order of magnitude improvement over today's capability. If sub-nanometer can be achieved, then MRFM?s true 3D imaging capability, lack of radiation damage and elementally specific contrast could make it a powerful tool for structural biologists.

BioProbes: Nanoscale Cantilevers. The objective of the BioProbes theme is to measure the forces, mechanical stiffness, electrostatics, and sequence of biological processes on cell membranes. Our theme will adapt unique cantilever designs for aqueous solution, based on recently invented torsional and dual-cantilever AFM cantilevers that have extremely high force sensitivity together with kHz sampling frequencies, ideal for biological samples.

Nanoprobes are arguably the enabling technology for all of the scientists and engineers working to realize the vast potential of nanotechnology. CPN research and outreach activities combine to broadly impact science, technology and education. The programs span graduate education, K-12 teacher development, academic courses, ethics for scientists and public scientific literacy. CPN intellectual contributions are widely disseminated through publications, on-line resources, conferences, workshops, and institutes.

The following activities constitute the educational and outreach programs:

Graduate and Postdoctoral Fellowships. Research students learn nanotechnology and precision measurement techniques as well as the fundamentals of their field. CPN Fellows are strongly engaged in Center events and outreach. The interdisciplinary Center provides a broader and deeper education for students than traditional graduate study.

CPN Prize Fellowships Program. CPN Graduate Prize Fellowships are competitively awarded on the basis of advisor recommendations and student-written proposals, and provide graduate students with a full stipend to initiate a novel nanoprobe research project.

Summer Institute for Middle School Teachers (SIMST). Middle school teachers participate in an intensive week-long program of content lectures, hands-on activities and curriculum development exercises. Teachers apply their new knowledge to create nanoscience lessons that are shared among participants for use during the school year and will be compiled for broader dissemination through workshops and online education resources.

CPN Annual Nanoprobe Workshop. The Annual Workshop provides an excellent opportunity for academic and industrial scientists to exchange knowledge and ideas and to broaden the horizons of the students.
Industrial Affiliates Program. The CPN Industrial Affiliates Program builds partnerships between CPN researchers and companies that have a strategic interest in nanoprobe development.

Collaborations. Collaborations with local institutions greatly enhance the impact and diversity of programs such as the Summer Institute for Middle School Teachers. Partners such as SRI International and the Exploratorium contribute curriculum and teaching best-practices, while collaborations with the National Hispanic University and the Latino College Preparatory Academy (LCPA) allow the Center to engage a diverse group of under-served students and teachers.

Curriculum. Probing the Nanoscale (AP275) is a graduate survey of scanning probes that draws on the expertise of CPN Investigators. Lecture videos are publicly available online as a rich source of information that has been accessed by people throughout the world.

Workshop on Professional Ethics for Students in Science and Engineering. A Workshop on Professional Ethics for Graduate Students in Science and Engineering was over-enrolled and reviewed very positively by the participants. This workshop will be offered annually during the renewal period.

IDBR: Solid State Patch-Clamping with Stealth Probes

Electrical measurements of cell activity play a critical role in understanding neural communication and testing for adverse reactions to pharmaceutical therapies. However, current measurement techniques either cause rapid cell death or provide low-quality data, severely limiting monitoring and understanding of these activities. There is thus a compelling need for a new instrument that provides long-duration, high-quality electrical cell measurements that is easy to use and can measure a number of cells at the same time. The key obstacle is creating an intimate junction between the cell membrane and a cell-penetrating electrode. This research program explores a unique approach to this problem by creating metallic electrodes that mimic the structure and functionality of biological transmembrane proteins. These electrodes are designed to fuse into the lipid membrane, enabling direct electrical access into the cell without leakage. Electrode structure, surface modification and size will be optimized to provide the best electrical junctions and cell longevity. The final architecture will be developed into a simple to use, 96-electrode platform for low-noise, long-term electrical cell measurements.

The broader impact of this work is greatly enhancing the number, quality, and duration of electrophysiological recording and stimulation, as well as training undergraduate students, graduate students, and middle school teachers in interdisciplinary scientific research. The final platform will dramatically impact studies of neural networks, neuron physiology, and drug screening, where slow testing rates and poor cell viability limits the number and types of experiments that can be performed. With this device, interconnected networks of up to 96 neurons could be stimulated and recorded simultaneously, allowing an unprecedented view of the evolution of sub-threshold voltage signaling in neural networks. These platforms will also play a crucial role in faster validation and screening for potential side effects of drug candidates, enhancing public health and safety.

? DESCRIPTION (provided by applicant): Transitioning from small numbers of neural depth recording electrodes to many thousands requires consideration not only of data management, but also how to non-destructively deliver these electrodes into the desired brain regions. Simply developing larger planar probes with more electrodes packed onto the surface invites increased immune response, likelihood of neuronal perturbation due to the presence of the large foreign substrate, and limited spatial sampling distributions. Here we propose to break the paradigm of mechanically stiff shuttles to insert electrodes, but instead will develop arrays of ultra-small 'slf-motile' electrodes that are each able to move to a target region under their own power, and with minimal perturbation of surrounding cells. This process is based upon electro-osmotic drives developed for microfluidics, which propel fluid along the electrode surface. We will investigate the device design and electrical optimization for guiding micron scale, flexible electrodes to specific locations. This will be complemented by organic electrochemical transistors as the recording elements, which are less sensitive to small sizes than metal electrode pads. The combination of minimal cell perturbation, ultra-small dimensions, and arbitrary three dimensional distributions will create a highly functional network of electrodes to record and modulate complex neural behavior throughout the brain. This non-perturbative, high-density sampling platform could have revolutionary impact both for fundamental neuroscience as well as clinical applications, such as brain-machine interfaces.

? DESCRIPTION: The advent of induced pluripotent stems cells (iPSCs) has created unprecedented access to primary cell types such as cardiomyocytes and neurons, which may lead to the next-generation of drugs, regenerative medicine, and cancer treatments. Unfortunately, the iPS transformation and differentiation process produces a heterogeneous mixture of cell types, required cell sorting and purification for testing or therapy. For these electrically active cells it is critical to directly test their electrophysiological and functional behavior, yet current patch-clamping measurements are destructive, preventing further cell use, and non-contact methods do not have sufficient resolution to discriminate between different phenotypes. The field is thus limited to non-functional analysis techniques such as morphology or cell-surface markers as proxies. Here we propose a new method for non-contact electrical assessment: Single Cell Stethoscopes for measuring the acoustic waves given off by the cell when an action potential fires. While small, these pressure waves are measureable with ultra-sensitive hydrophones. Under this program, we will directly correlate the measured acoustic signals to patch clamp electrophysiology, and demonstrate the ability to identify individual cardiomyocyte cell types. These hydrophones will be an order of magnitude more sensitive than any existing at the relevant frequency ranges for cardiomyocytes (5-10 Hz), enabling measurements down to individual cells. We will further reveal the correlation between the electronic action potential and acoustic signals, and use these to non-destructively categorize and iPSC derived cardiomyocytes. These cell populations will be tested and benchmarked against known cell types, and the accuracy of the technique quantitatively assessed. This completed technology will dramatically impact the effectiveness and safety of iPSC-derived cells for disease modeling, regenerative medicine, and drug discovery.

Project Summary The advent of induced pluripotent stems cells (iPSCs) has created unprecedented access to primary cell types such as cardiomyocytes and neurons, which may lead to the next-generation of patient-specific disease models and more effective therapeutics. Unfortunately, the iPS reprogramming and differentiation process produces a heterogeneous mixture of cell types, required cell sorting and purification for testing or therapy. In particular, how the mRNA and protein expression in cells determines the evolution of cell lineage over time is currently unclear at the single cell level. We propose to adapt the ?nanostraw? platform developed initially developed in the Melosh lab for intracellular delivery to non-destructively sample cytosolic proteins and mRNA over an extended period of time (1-3 weeks). This platform can scale from individual cells to thousands of cells in parallel, depending on the desired application. The technique will first be assessed using cell lines as proof of principle, with quantitative statistical evaluation of the performance of the platform. Subsequently we will measure somatic iPSCs during differentiation into cardiomyocytes over a 3-week period. The extracted proteins and mRNA will then be analyzed to provide insights into the longitudinal proteins and mRNA concentrations inside the cell and how these relate to the terminal cell phenotype. The goal of this R21 proposal is to validate and quantitatively assess the performance of this system as applied to the differentiation of iPSC cells into cardiomyocytes. Toward this end, we have constructed a team of both engineering and cardiomyocyte iPSC differentiation expertise. If successful, this work will form the foundational technology for non-destructively monitoring intracellular contents, particularly for understanding dynamic cell function changes such as reprogramming and differentiation.

Planarians have captured the imagination of generations of scientists, and today play a critical role in our efforts to understand development and regeneration. These small flatworms can regenerate their entire body from small tissue fragments. As a result of the current surge in the sequencing technology, tremendous progress has been made over the past two decades to understand planarian biology from a variety of perspectives, including but not limited to regeneration, stem cell, animal body plan and evolution, germline, nervous system, metabolism, innate immunity, signaling pathways, regulatory RNAs, and genome stability. Yet the entire field has been limited by the lack of tools for transgene expression and genome editing. At the same time, technological innovation has exploded for transfection and gene editing of mammalian cells. In particular, nanotechnological approaches can very locally disrupt the cell membrane and inject molecular cargo directly, providing both low cell toxicity and high delivery efficiencies. In this project, the researchers will use the novel nanotechnology, "nanostraws," to deliver genetic materials into planarian cells, and provide a simple and effective means for transgene expression and genome editing. This project also aims to rapidly disseminate the new technology by facilitating data, protocol, and materials sharing across labs, and organizing training workshops. In addition, because of planarians' appealing regenerative ability, childlike cuteness, and ease to rear in the lab, the researchers will promote the usage of planarians in teaching, education, and outreach activities to engage non-scientists' interests in modern biological research.

Planarians have been a powerful animal model to study tissue regeneration and stem cell biology. They have the unique capacity to regenerate the entire body from minute tissue fragments using pluripotent somatic stem cells. During this process, they reset the body axes and rebuild all organs in appropriate proportions. Although extensive genomic and transcriptomic information is available, progress on addressing causal genotype-phenotype relationships in planarians has been severely hindered by a lack of transgenic tools despite decades of attempts. Enabled by the recent technical advances made in the investigators' laboratories, including cell culture and transplantation methods, novel nanotechnology for gene delivery in hard-to-transfect cell types, and successful expression of luminescence reporters in planarian cells, they aim to address this long-standing challenge. This research project aims to develop and disseminate the methodology and resources for planarian transgenesis. Specifically, the goals of this project include (1) to develop nanoscale electroporation methods for transgene delivery in planarian cells, (2) to demonstrate genome editing using CRISPR/Cas9, and (3) to enhance the collaboration, training, and diversity of the planarian research community to address a broad spectrum of questions in molecular, cellular, organismal, and evolutionary biology.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Non-Technical Description:
The National Nanotechnology Coordinated Infrastructure site at Stanford University, nano@stanford, promotes nanoscience and engineering by making experimental resources and the know-how to use them available to all. At the core of nano@stanford are four advanced research facilities that are open for use by any researcher, from other universities, industry, or government: the Stanford Nano Shared Facilities (SNSF), the Stanford Nanofabrication Facility (SNF), the Stanford Microchemical Analysis Facility (MAF), and the Stanford Isotope and Geochemical Measurement and Analysis Facility (SIGMA). These facilities are staffed with technical experts dedicated to supporting the progress of science and together span the full range of fabrication and characterization methods to serve the broad user community. The site welcomes all disciplines; researchers use the facilities to solve real world problems in energy, environment, medicine, and beyond. The site also hosts artists and teachers, as its mission is to train and educate, not only the researchers in the facilities, but anyone anywhere wanting to learn about experimental nanoscience and technology. nano@stanford cultivates a library of just-in-time educational materials aimed at building foundational knowledge for the newest researchers and is available to everyone everywhere. nano@stanford has developed and will expand programs in workforce development, teacher training, and K-12 outreach. Through its partners in the NNCI network, nano@stanford will continue to expand these efforts to educate beyond the classroom and beyond the lab.

Technical Description:
nano@stanford offers a comprehensive array of nanofabrication and nanocharacterization equipment and expertise, housed in facilities that encompass ~30,000 ft2 of lab space, including 16,000 ft2 of cleanrooms, 6,000 ft2 of which is low vibration. Fabrication capabilities are anchored by a full electronics device fabrication cleanroom and a nanopatterning laboratory that are supplemented by a dozen lab spaces providing specialized and flexible processing systems. Characterization capabilities encompass the full suite of tools for imaging and chemical/physical property identification of materials. nano@stanford offers advanced capabilities not normally available to the research community at large. These specialized capabilities include: MOCVD for growing crystalline films of III-V materials; Electron-Beam Lithography for wafers up to 200 mm; NanoSIMS for isotope analysis at high lateral resolution; scanning SQUID for high resolution mapping of surface magnetic fields. Experienced, technical staff support all researchers, who have used the facilities to develop and characterize advanced structures, such as photonic crystals, photodetectors, optical MEMS, inertial sensors, optical/electronic biosensors, cantilever probes, nano-FETs, new memories, batteries, and photovoltaics. nano@stanford welcomes researchers in non-traditional areas of science and engineering, such as the life sciences and medicine, earth and environmental sciences, and offers personal consultations, seed grants, fabrication and characterization services, seminars and webinars, to the nano-curious.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Project Summary/Abstract The goal of this proposal is to develop a high-fidelity adaptive electrical interface to the retina and use it to investigate the contributions of the parallel visual pathways (M and P, ON and OFF) to the perception and behavior of macaque monkeys. The device will operate bi-directionally at the resolution of single cells and single spikes, and will adapt itself to the diversity of cell types and locations in the host neural circuitry. We build on our extensive work in isolated primate retina, which demonstrates the ability to electrically stimulate and record nearly complete populations of retinal ganglion cells at single-cell, single-spike resolution. We will develop the technologies needed to take this approach to the in vivo setting, and then use them to probe visual function in behaving macaques, by pursuing three aims: (1) develop and test a high-density, large-scale electrical recording and stimulation device, (2) develop surgical techniques, test biocompatibility, and test functionality in anesthetized animals, and (3) probe the computations within and between the M and P pathways and their role in motion vision. Our unique approach to these problems relies on a team with extensive experience in neurophysiology, visual behavior, integrated circuits, materials science, surgery, and signal processing. In addition to testing fundamental aspects of visual function in novel ways, this work will produce a platform technology for other neural interfaces and a functional prototype for a future retinal implant to treat incurable blindness.