Robert M. Panas

Simulation of a carbon nanotube-based compliant parallel-guiding mechanism: A nanomechanical building block

The authors report the behavior of a nanoscale parallel-guiding mechanism wherein the compliant components are single-walled carbon nanotubes. Parallel-guiding mechanisms are often the building blocks of macro- and microscale mechanical systems. The authors present results that provide insight into the performance of a parallel-guiding mechanism for nanoscale devices. The device exhibits a range over 75% of the device size, i.e., 5.5nm, when actuated with 6.4nN. Below 3.6nN, displacements are due to bulk elastic bending of the nanotubes. Above 5.2nN, displacements are governed by the hingelike bending of kinks in the nanotubes. van der Waals forces are shown to cause direction-dependent behavior.

A multi-axis MEMS sensor with integrated carbon nanotube-based piezoresistors for nanonewton level force metrology.

This paper presents the design and fabrication of a multi-axis microelectromechanical system (MEMS) force sensor with integrated carbon nanotube (CNT)-based piezoresistive sensors. Through the use of proper CNT selection and sensor fabrication techniques, the performance of the CNT-based MEMS force sensor was increased by approximately two orders of magnitude as compared to current CNT-based sensor systems. The range and resolution of the force sensor were determined as 84 μN and 5.6 nN, respectively. The accuracy of the force sensor was measured to be better than 1% over the devices full range.

A Pseudo-Rigid-Body Model for Large Deflections of Fixed-Clamped Carbon Nanotubes

Carbon nanotubes (CNTs) may be used to create nanoscale compliant mechanisms that possess large ranges of motion relative to their device size. Many macroscale compliant mechanisms contain compliant elements that are subjected to fixed-clamped boundary conditions, indicating that they may be of value in nanoscale design. The combination of boundary conditions and large strains yield deformations at the tube ends and strain stiffening along the length of the tube, which are not observed in macroscale analogs. The large-deflection behavior of a fixedclamped CNT is not well-predicted by macroscale large-deflection beam bending models or truss models. Herein, we show that a pseudo-rigid-body model may be adapted to capture the strain stiffening behavior and, thereby, predict a CNT’s fixed-clamped behavior with less than 3% error from molecular simulations. The resulting pseudo-rigid-body model may be used to set initial design parameters for CNT-based compliant mechanisms. This removes the need for iterative, time-intensive molecular simulations during initial design phases. DOI: 10.1115/1.4001726

Eliminating Underconstraint in Double Parallelogram Flexure Mechanisms

We present an improved flexure linkage design for removing underconstraint in a double parallelogram (DP) linear flexural mechanism. This new linkage alleviates many of the problems associated with current linkage design solutions such as static and dynamic performance losses and increased footprint. The improvements of the new linkage design will enable wider adoption of underconstraint eliminating (UE) linkages, especially in the design of linear flexural bearings. Comparisons are provided between the new linkage design and existing UE designs over a range of features including footprint, dynamics, and kinematics. A nested linkage design is shown through finite element analysis (FEA) and experimental measurement to work as predicted in selectively eliminating the underconstrained degrees-of-freedom (DOF) in DP linear flexure bearings. The improved bearing shows an 11 × gain in the resonance frequency and 134× gain in static stiffness of the underconstrained DOF, as designed. Analytical expressions are presented for designers to calculate the linear performance of the nested UE linkage (average error < 5%). The concept presented in this paper is extended to an analogous double-nested rotary flexure design.

One-step volumetric additive manufacturing of complex polymer structures

A new approach for ultrarapid 3D manufacturing creates complex aperiodic volumes in a single step. Two limitations of additive manufacturing methods that arise from layer-based fabrication are slow speed and geometric constraints (which include poor surface quality). Both limitations are overcome in the work reported here, introducing a new volumetric additive fabrication paradigm that produces photopolymer structures with complex nonperiodic three-dimensional geometries on a time scale of seconds. We implement this approach using holographic patterning of light fields, demonstrate the fabrication of a variety of structures, and study the properties of the light patterns and photosensitive resins required for this fabrication approach. The results indicate that low-absorbing resins containing ~0.1% photoinitiator, illuminated at modest powers (~10 to 100 mW), may be successfully used to build full structures in ~1 to 10 s.

Engineering Electrical Interfaces to Silicon via Indium Solder

This paper provides engineering models of a simple and robust approach for creating electrical connections to silicon using reduced temperature (<;200 °C substrate) soldering. This removes a significant hurdle to the fabrication of high performance, custom silicon piezoresistors. The approach focuses on reducing the resistance of diodes that are undergoing reverse bias behavior, commonly considered to be unacceptable for electrical connections. Reverse bias Schottky barrier analytical models based on quantum mechanical first principles are developed to explain how the behavior is affected by doping, soldering temperature, and geometry. This understanding is encapsulated within parametric models that enable rapid design and optimization of the electrical contacts to silicon. Using this model, one may design contacts for practical applications that do not require the conventional microfabrication processing or the high-temperature processing. Indium solder is found to be the best solder for this process, with ohmic contact resistances of ≈1 Ω-cm2 for (110) p-type wafers at 1017 cm-3 doping.

Erratum to “A High-Speed Large-Range Tip-Tilt-Piston Micromirror Array” [Feb 17 196-205]

In the above paper [1] , there was an error in the first footnote regarding author contribution. The corrected author contribution information is as follows: (Jonathan B. Hopkins and Robert M. Panas are co-first authors.)

Planar microparticle assembly and photopolymerized joining with holographic optical tweezers

Holographic optical tweezers are able to assemble and permanently join polystyrene microspheres into planar patterns using an acrylamide-based photopolymerization reaction. This approach holds potential as a new method for additive fabrication of multi-material microstructures.

Non-Cleanroom Fabrication of Carbon Nanotube-Based MEMS Force and Displacement Sensors

Traditional microelectromechanical MEMS fabrications such photolithography and deep reactive ion etching (DRIE) are expensive and time consuming. This limits the types and designs of MEMS devices that can be produced cost effectively since in order to overcome the high startup costs and times associated with traditional MEMS fabrication techniques tens of thousands of each type of MEMS device must be produced and sold. In this paper, we will present a method for placing carbon nanotube (CNT) based piezoresistive sensors onto metallic flexural elements that are created via micromachining. This method reduces the fabrication time from over 3 months to less than 3 days. In addition, the fabrication cost is reduced form over

Scaling electromechanical sensors down to the nanoscale

500 per device to less than