Design and fabrication of meso-scale flexural testing apparatus for evaluating aligned CNT composite flexures

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references (p. 58).The objective of this research is to explore the possibility of using aligned Carbon Nanotube (CNT) based composites in flexures by measuring the kinematics of a composite flexure. The first phase of the research, described in this thesis, is to design, fabricate and assemble a testing apparatus optimized for evaluating aligned CNT based composites. Using existing literature on composites and present limitations on their growth, functional requirements are set down for the testing apparatus. Several designs are qualitatively evaluated, leading to a near optimal design form. This chosen design is modeled as a spring-mass system, and the exact geometry needed to satisfy the functional requirements is determined. The design of the full apparatus is expanded to contain the necessary probes and actuators. The testing apparatus is fabricated using CNC machining, and assembled in a controlled environment to reduce thermal and mechanical error during operation. The system is calibrated and its resolution is found to be 0.021 N over a range of 28.5 N applied force and 1.5 pm over a range of 816 pm applied displacement. Several non-linearities are noted and corrected mathematically.by Robert M. Panas.S.B

Design and fabrication of a multipurpose compliant nanopositioning architecture

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (p. 227-241).This research focused on generating the knowledge required to design and fabricate a high-speed application flexible, low average cost multipurpose compliant nanopositioner architecture with high performance integrated sensing. Customized nanopositioner designs can be created in ~~1 week, for 30x increase in sensing dynamic range over comparable state-of-the-art compliant nanopositioners. These improvements will remove one of the main hurdles to practical non-IC nanomanufacturing, which could enable advances in a range of fields including personalized medication, computing and data storage, and energy generation/storage through the manufacture of metamaterials. Advances were made in two avenues: flexibility and affordability. The fundamental advance in flexibility is the use of a new approach to modeling the nanopositioner and sensors as combined mechanical/electronic systems. This enabled the discovery of the operational regimes and design rules needed to maximize performance, making it possible to rapidly redesign nanopositioner architecture for varying functional requirements such as range, resolution and force. The fundamental advance to increase affordability is the invention of Non-Lithographically-Based Microfabrication (NLBM), a hybrid macro-/micro-fabrication process chain that can produce MEMS with integrated sensing in a flexible manner, at small volumes and with low per-device costs. This will allow for low-cost customizable nanopositioning architectures with integrated position sensing to be created for a range of micro-/nano- manufacturing and metrology applications. A Hexflex 6DOF nanopositioner with titanium flexures and integrated siliconpiezoresistive sensing was fabricated using NLBM. This device was designed with a metal mechanical structure in order to improve its robustness for general handling and operation. Single crystalline silicon piezoresistors were patterned from bulk silicon wafers and transferred to the mechanical structure via thin-film patterning and transfer. This work demonstrates that it is now feasible to design and create a customized positioner for each nanomanufacturing/metrology application. The Hexflex architecture can be significantly varied to adjust range, resolution, force scale, stiffness, and DOF all as needed. The NLBM process was shown to enable alignment of device components on the scale of 10's of microns. 150μm piezoresistor arm widths were demonstrated, with suggestions made for how to reach the expected lower bound of 25[mu]m. Flexures of 150[mu]m and 600[mu]m were demonstrated on 4 the mechanical structure, with a lower bound of ~~50[mu]m expected for the process. Electrical traces of 800[mu]m width were used to ensure low resistance, with a lower bound of ~~100[mu]m expected for the process. The integrated piezoresistive sensing was designed to have a gage factor of about 125, but was reduced to about 70 due to lower substrate temperatures during soldering, as predicted by design theory. The sensors were measured to have a full noise dynamic range of about 59dB over a 10kHz sensor bandwidth, limited by the Schottky barrier noise. Several simple methods are suggested for boosting the performance to ~~135dB over a 10kHz sensor bandwidth, about a <1Å resolution over the 200[mu]m range of the case study device. This sensor performance is generally in excess of presently available kHz-bandwidth analog-to-digital converters.by Robert M. Panas.Ph.D

Design, fabrication and mechanical optimization of a flexural high speed nanopositioning imaging stage

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Includes bibliographical references (p. 204-206).The intent of this research is to generate the knowledge required to design, fabricate and operate a device capable of high speed nano-scale vertical positioning of microscopy samples. The high speed focusing device (HSFD) created during this research utilizes a new combination of technologies for the purpose of imaging: Lorentz coil actuation, flexural bearings and strain gage sensing. The application of the technologies combined with precision design principles, as used in the HSFD, result in a demonstrated combination of performance and cost gains over a measured commercially available system. The HSFD is able to perform steps with 8 ms 95% settling time, 2% dynamic accuracy, and 0.005% static accuracy while operating with a resolution of 10.5 nm (l[sigma]) over a range of 500 [mu]m at a cost of about $1400. This performance is 3x faster stepping, 2x better dynamic accuracy, ~~100x better static accuracy, equivalent resolution and range to the top of the line commercial devices at less than half of the cost. The reduced cost is envisioned to enable greater distribution and use of nano-positioning imaging stages, while the increased performance is envisioned to enable faster, more benign (in the case of biological sciences) and more precise imaging. The increased use and data gathering ability of the new device are envisioned to enable fields of research such as biology and materials science to extend their bounds further into the micro/nano-scale as well as further along the time scale for both high speed and low speed processes.by Robert M. Panas.S.M

Additively manufacturable micro-mechanical logic gates.

Early examples of computers were almost exclusively based on mechanical devices. Although electronic computers became dominant in the past 60 years, recent advancements in three-dimensional micro-additive manufacturing technology provide new fabrication techniques for complex microstructures which have rekindled research interest in mechanical computations. Here we propose a new digital mechanical computation approach based on additively-manufacturable micro-mechanical logic gates. The proposed mechanical logic gates (i.e., NOT, AND, OR, NAND, and NOR gates) utilize multi-stable micro-flexures that buckle to perform Boolean computations based purely on mechanical forces and displacements with no electronic components. A key benefit of the proposed approach is that such systems can be additively fabricated as embedded parts of microarchitected metamaterials that are capable of interacting mechanically with their surrounding environment while processing and storing digital data internally without requiring electric power

One-step volumetric additive manufacturing of complex polymer structures.

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

Three new pancreatic cancer susceptibility signals identified on chromosomes 1q32.1, 5p15.33 and 8q24.21.

Genome-wide association studies (GWAS) have identified common pancreatic cancer susceptibility variants at 13 chromosomal loci in individuals of European descent. To identify new susceptibility variants, we performed imputation based on 1000 Genomes (1000G) Project data and association analysis using 5,107 case and 8,845 control subjects from 27 cohort and case-control studies that participated in the PanScan I-III GWAS. This analysis, in combination with a two-staged replication in an additional 6,076 case and 7,555 control subjects from the PANcreatic Disease ReseArch (PANDoRA) and Pancreatic Cancer Case-Control (PanC4) Consortia uncovered 3 new pancreatic cancer risk signals marked by single nucleotide polymorphisms (SNPs) rs2816938 at chromosome 1q32.1 (per allele odds ratio (OR) = 1.20, P = 4.88x10 -15), rs10094872 at 8q24.21 (OR = 1.15, P = 3.22x10 -9) and rs35226131 at 5p15.33 (OR = 0.71, P = 1.70x10 -8). These SNPs represent independent risk variants at previously identified pancreatic cancer risk loci on chr1q32.1 ( NR5A2), chr8q24.21 ( MYC) and chr5p15.33 ( CLPTM1L- TERT) as per analyses conditioned on previously reported susceptibility variants. We assessed expression of candidate genes at the three risk loci in histologically normal ( n = 10) and tumor ( n = 8) derived pancreatic tissue samples and observed a marked reduction of NR5A2 expression (chr1q32.1) in the tumors (fold change -7.6, P = 5.7x10 -8). This finding was validated in a second set of paired ( n = 20) histologically normal and tumor derived pancreatic tissue samples (average fold change for three NR5A2 isoforms -31.3 to -95.7, P = 7.5x10 -4-2.0x10 -3). Our study has identified new susceptibility variants independently conferring pancreatic cancer risk that merit functional follow-up to identify target genes and explain the underlying biology

Fabrication of Six Degrees-of-Freedom Hexflex Positioner With Integrated Strain Sensing Using Nonlithographically Based Microfabrication

© 2021 BMJ Publishing Group. All rights reserved. A process flow is described for the low cost, flexible fabrication of metal micro-electromechanical systems (MEMS) with high performance integrated sensing. The process is capable of producing new designs in ≈1 week at an average unit cost of 30× increase in sensing dynamic range over comparable state-of-the-art compliant nanopositioners. The nonlithographically based microfabrication (NLBM) process is uniquely suited to create high performance nanopositioning architectures which are customizable to the positioning requirements of a range of nanoscale applications. These can significantly reduce the cost of nanomanufacturing research and development, as well as accelerate the development of new processes and the testing of fabrication process chains without excess capital investment. A six degrees-of-freedom (6DOF) flexural nanopositioner with integrated sensing for all 6DOF was fabricated using the newly developed process chain. The fabrication process was measured to have ≈30 μm alignment. Sensor arm, flexure, and trace widths of 150 μm, 150 μm, and 800 μm, respectively, were demonstrated. Process capabilities suggest lower bounds of 25 μm, 50 μm, and 100 μm, respectively. Dynamic range sensing of 52 dB was demonstrated for the nanopositioner over a 10 kHz sensor bandwidth. Improvements are proposed to approach sensor performance of about 135 dB over a 10 kHz sensor bandwidth