Rosenberger, Matthew R.
Chen, Sihan
Prater, Craig B.
King, William P.
This paper reports the design, fabrication, and characterization of micromechanical devices that can present an engineered contact stiffness to an atomic force microscope (AFM) cantilever tip. These devices allow the contact stiffness between the AFM tip and a substrate to be easily and accurately measured, and can be used to calibrate the cantilever for subsequent mechanical property measurements. The contact stiffness devices are rigid copper disks of diameters 2-18 mu m integrated onto a soft silicone substrate. Analytical modeling and finite element simulations predict the elastic response of the devices. Measurements of tip-sample interactions during quasi-static force measurements compare well with modeling simulation, confirming the expected elastic response of the devices, which are shown to have contact stiffness 32-156 N m(-1). To demonstrate one application, we use the disk sample to calibrate three resonant modes of a U-shaped AFM cantilever actuated via Lorentz force, at approximately 220, 450, and 1200 kHz. We then use the calibrated cantilever to determine the contact stiffness and elastic modulus of three polymer samples at these modes. The overall approach allows cantilever calibration without prior knowledge of the cantilever geometry or its resonance modes, and could be broadly applied to both static and dynamic measurements that require AFM calibration against a known contact stiffness.
Nikiforov, Maxim P.
Hohlbauch, Sophia
King, William P.
Voitchovsky, Kislon
Contera, Sonia Antoranz
Jesse, Stephen
Kalinin, Sergei V.
Proksch, Roger
Phase transitions in purple membrane have been a topic of debate for the past two decades. In this work we present studies of a reversible transition of purple membrane in the 50-60 degrees C range in zeptoliter volumes under different heating regimes (global heating and local heating). The temperature of the reversible phase transition is 52 +/- 5 degrees C for both local and global heating, supporting the hypothesis that this transition is mainly due to a structural rearrangement of bR molecules and trimers. To achieve high resolution measurements of temperature-dependent phase transitions, a new scanning probe microscopy-based method was developed. We believe that our new technique can be extended to other biological systems and can contribute to the understanding of inhomogeneous phase transitions in complex systems.
Rosenberger, Matthew R.
Wang, Michael Cai
Xie, Xu
Rogers, John A.
Nam, SungWoo
King, William P.
Atomic force microscope infrared spectroscopy (AFM-IR) combines the spatial resolution of AFM with the chemical specificity of IR spectroscopy. In AFM-IR, sample absorption of pulsed IR light causes rapid thermomechanical expansion, which excites resonance in an AFM cantilever in contact with the sample. The cantilever resonant amplitude is proportional to the local sample IR absorption coefficient. It is difficult to detect thermomechanical expansion in the smallest samples such as 1D and 2D nanomaterials. In this work, we overcome this limitation and use AFM-IR to measure nanometer-scale IR absorption in individual single walled carbon nanotubes and monolayer graphene. By placing a thin layer of polymer beneath the sample, the AFM-IR signal may be increased by up to two orders of magnitude. The polymer beneath the sample thermally insulates the sample and amplifies thermomechanical expansion. Finite element simulations agree with the measurements and provide a general framework for applying this approach to arbitrary samples, including other 1D and 2D materials and thin biological samples.
Radadia, Adarsh D.
Stavis, Courtney J.
Carr, Rogan
Zeng, Hongjun
King, William P.
Carlisle, John A.
Aksimentiev, Aleksei
Hamers, Robert J.
Bashir, Rashid
Immunoassays for detection of bacterial pathogens rely on the selectivity and stability of bio-recognition elements such as antibodies tethered to sensor surfaces. The search for novel surfaces that improve the stability of biomolecules and assay performance has been pursued for a long time. However, the anticipated improvements in stability have not been realized in practice under physiological conditions because the surface functionalization layers on commonly used substrates, silica and gold, are themselves unstable on time scales of days. In this paper, we show that covalent linking of antibodies to diamond surfaces leads to substantial improvements in biological activity of proteins as measured by the ability to selectively capture cells of the pathogenic bacterium Escherichia coli O157:H7 even after exposure to buffer solutions at 37 degrees C for extended periods of time, approaching 2 weeks. Our results from ELISA, XPS, fluorescence microscopy, and MD simulations suggest that by using highly stable surface chemistry and controlling the nanoscale organization of the antibodies on the surface, it is possible to achieve significant improvements in biological activity and stability. Our findings can be easily extended to functionalization of micro and nanodimensional sensors and structures of biomedical diagnostic and therapeutic interest.
This paper presents a microcantilever having a microscale heater-thermometer fabricated from doped single crystal silicon that is mounted on a silicon nitride thermal isolation structure. The silicon nitride isolation structure is in turn connected to doped single crystal silicon legs. The cantilever fabrication, its characterization, and its application in thermal nanotopography measurements are presented in this work. The cantilever can reach temperatures over 600 degrees C with a heating power of 4 mW. The cantilever has a thermal resistance that exceeds 10(5) K W(-1) when away from a substrate. Making a contact-mode scan over a silicon calibration grating of height 20 nm, the cantilever has a topography reading sensitivity of 1.3 x 10(-4) nm(-1), and a topography reading resolution of about 7 pm Hz(-1/2). These performance characteristics compare extremely well to published ones for other kinds of cantilevers.
Hua, Yueming
Saxena, Shubham
Clifford, Henderson
King, William P.
Nanopatterning of polymer thin films is the basis for the vast majority of current microlithography processes used in integrated circuit manufacturing. Future scaling of such polymer patterning methods will require innovative solutions to overcome the prohibitively high tool and mask costs associated with current optical lithography methods, which will prevent their use in many applications. Scanning probe-based methods for surface modification are desirable in that they offer high resolution patterning while also offering the ability to perform in situ metrology. We report a new scanning probe lithography method that uses heated atomic force microscope cantilevers to achieve nanoscale patterning in thin polymer films via the local thermal decomposition of the polymer and, in situ postdecomposition metrology. Specifically, cross-linked polycarbonate thin films are developed in this work and are shown to be excellent writing media for this process. This new method has the advantage that the tip can be heated and cooled on microsecond time scales and thus material can be removed and patterned without need for the disengagement of the tip from the polymer surface. This ability to write while the tip is constantly engaged to the surface offers significantly higher, writing speeds for discontinuous patterns relative to other scanning probe techniques. (c) 2007 Society of Photo-Optical Instrumentation Engineers.
Rowland, Harry D.
King, William P.
Sun, Amy C.
Schunk, P. Randy
Cross, Graham L. W.
This paper reports predictions of nanometer-scale polymer deformation during nanoprobe indentation at elevated temperature. The simulations assume continuum polymer properties with modified boundary conditions to model subcontinuum polymer mechanical deformation. The indenter is a heated atomic force microscope (AFM) tip, and the media is a high molecular weight polymer film where tip radius, film thickness, and polymer coil radius are of similar size, in the range 20-50 rim. The simulations model isothermal conditions, where the tip and polymer are at the same temperature, or nonisothermal conditions, where the tip is hot while the polymer is cool. Isothermal simulations with shear-thinning bulk material behavior and full-slip polymer-tip interface predict force, displacement, and displacement rate. Nonisothermal simulations show that the polymer-tip interface temperature governs the indentation process. The temperature-dependent polymer viscosity varies by several orders of magnitude within 50 nm of the polymer-tip interface, causing highly localized polymer deformation near the tip. Steep viscosity gradients near the tip require the polymer-tip interface temperature to exceed the polymer glass transition temperature in order to form indents. In all cases the predictions compare well with experimental data. The continuum simulations allow for improved understanding of high-temperature AFM nanoindentation and nanoembossing.
Fletcher, Patrick C.
Bhatia, Bikramjit S.
Wu, Yan
Shannon, Mark A.
King, William P.
This paper reports the integration of both electrical and thermal elements into the free end of an atomic-force microscope cantilever, where the electrode and heater-thermometer are electrically isolated by an NPN semiconductor back-to-back diode. The electrothermal cantilever can be self heated using an integrated solid-state heater to more than 600 degrees C. The tip voltage can be measured or controlled independent of the tip temperature, either in the direct or the alternating current mode. To our knowledge, this setup is the first microcantilever to have a solid-state junction and heater integrated near a scanning probe tip. [2010-0276]
Lee, Jungchul
Liao, Albert
Pop, Eric
King, William P.
We utilize a multifunctional atomic force microscope (AFM) cantilever applying highly localized temperature and electric fields to interrogate transport in single-wall carbon nanotube field-effect transistors (CNTFETs). The probe can be operated either in contact with the CNT, in intermittent contact, or as a Kelvin probe, and can independently control the electric field, mechanical force, and temperature applied to the CNT. We modulate current flow in the CNT with tip-applied electric field, and find this field-effect depends upon both cantilever heating and CNT self-heating. CNT transport is also investigated with AFM tip temperature up to 1170 degrees C. Tip-CNT thermal resistance is estimated at 1.6 X 10(7) K/W and decreases with increasing temperature. Threshold force (<100 nN) for reliable contact mode imaging is extracted and used to determine set points for nanotube manipulation, such as displacement or cutting. The ability to measure thermal coupling to a single-molecule electronic device could offer new insights into nanoelectronic devices.
Lee, Woo Kyung
Dai, Zhenting
King, William P.
Sheehan, Paul E.
Nanoparticle polymer Composites containing metal, semiconductor, magnetic, and optically active nanoparticles were deposited onto multiple substrates from a heatable atomic force microscope tip. The nanoparticle nanostructures were functional as deposited or could be etched with an oxygen plasma, revealing single nanoparticle lithographic resolution. Many types of nanoparticles can be patterned with the same technique, without the need to tailor the substrate chemistry and without solution processing.
Pikul, James H.
Liu, Jinyun
Braun, Paul V.
King, William P.
Microbatteries are increasingly important for powering electronic systems, however, the volumetric energy density of microbatteries lags behind that of conventional format batteries. This paper reports a primary microbattery with energy density 45.5 mu Wh cm(-2) mu m(-1) and peak power 5300 mu W cm(-2) mu m(-1), enabled by the integration of large volume fractions of high capacity anode and cathode chemistry into porous micro-architectures. The interdigitated battery electrodes consist of a lithium metal anode and a mesoporous manganese oxide cathode. The key enabler of the high energy and power density is the integration of the high capacity manganese oxide conversion chemistry into a mesostructured high power interdigitated bicontinuous cathode architecture and an electrodeposited dense lithium metal anode. The resultant energy density is greater than previously reported three-dimensional micro batteries and is comparable to commercial conventional format lithium-based batteries. (C) 2016 Elsevier B.V. All rights reserved.