Blaise Gassend's research while affiliated with Massachusetts Institute of Technology and other places

AEGIS is a single-chip secure processor that can be used to protect the integrity and confidentiality of an application program from both physical and software attacks. We briefly describe the history behind this architecture and its key features, discuss main observations and lessons from the project, and list limitations of AEGIS and how recent research addresses them.

A group of devices are fabricated based on a common design, each device having a corresponding plurality of measurable characteristics that is unique in the group to that device, each device having a measurement module for measuring the measurable characteristics. Authentication of one of the group of devices is enabled by selective measurement of one or more of the plurality of measurable characteristics of the device.

We report the fabrication and experimental characterization of a carbon nanotube (CNT)-based MEMS/NEMS electron impact gas ionizer with an integrated extractor gate for portable mass spectrometry. The ionizer achieves low-voltage ionization using sparse forests of plasma-enhanced chemical-vapor-deposited CNTs as field emitters and a proximal extractor grid with apertures aligned to the CNT forests to facilitate electron transmission. The extractor gate is integrated to the ionizer using a high-voltage MEMS packaging technology based on Si springs defined by deep reactive ion etching. The ionizer also includes a high-aspect-ratio silicon structure (??foam) that facilitates sparse CNT growth and also enables uniform current emission. The devices were tested as field emitters in high vacuum (10[superscript -8] torr) and as electron impact ionizers using argon at pressures of up to 21 mtorr. The experimental data show that the MEMS extractor gate transmits up to 66% of the emitted current and that the ionizers are able to produce up to 0.139 mA of ion current with up to 19% ionization efficiency while consuming 0.39 W.

This paper reports the design and fabrication of high-aspect-ratio needlelike silicon structures that can have complex geometry. The structures are hundreds of micrometers tall with submicrometer-sharp protrusions, and they are fabricated using a series of passivated and unpassivated deep reactive-ion etching (DRIE) steps. A simple model is presented to predict the geometry of the structure based on the etch mask and the etch sequence. Model predictions are in good qualitative agreement with fabrication results, making it a useful design tool. The model is compared with literature reports on tapered DRIE.

This paper reports the design and fabrication of high-aspect-ratio needlelike silicon structures that can have complex geometry. The structures are hundreds of micrometers tall with submicrometer-sharp protrusions, and they are fabricated using a series of passivated and unpassivated deep reactive-ion etching (DRIE) steps. A simple model is presented to predict the geometry of the structure based on the etch mask and the etch sequence. Model predictions are in good qualitative agreement with fabrication results, making it a useful design tool. The model is compared with literature reports on tapered DRIE.

We report the fabrication and experimental characterization of a carbon nanotube (CNT)-based MEMS/NEMS electron impact gas ionizer with an integrated extractor gate for portable mass spectrometry. The ionizer achieves low-voltage ionization using sparse forests of plasma-enhanced chemical-vapor-deposited CNTs as field emitters and a proximal extractor grid with apertures aligned to the CNT forests to facilitate electron transmission. The extractor gate is integrated to the ionizer using a high-voltage MEMS packaging technology based on Si springs defined by deep reactive ion etching. The ionizer also includes a high-aspect-ratio silicon structure (??foam) that facilitates sparse CNT growth and also enables uniform current emission. The devices were tested as field emitters in high vacuum (10^-8 torr) and as electron impact ionizers using argon at pressures of up to 21 mtorr. The experimental data show that the MEMS extractor gate transmits up to 66% of the emitted current and that the ionizers are able to produce up to 0.139 mA of ion current with up to 19% ionization efficiency while consuming 0.39 W.

We report the fabrication and experimental characterization of a novel low-cost carbon nanotube (CNT)-based electron impact ionizer (EII) with integrated gate for portable mass spectrometry applications. The device achieves low-voltage ionization using sparse forests of plasma-enhanced chemical vapor deposited (PECVD) CNTs field emitter tips, and a proximal gate with open apertures to facilitate electron transmission. The gate is integrated using a deep reactive ion etched (DRIE) spring-based high-voltage MEMS packaging technology. The device also includes a high aspect-ratio silicon structure (mufoam) that facilitates sparse CNT growth and limits the electron current per emitter. The devices were tested as field emitters in high vacuum (10^-8 Torr). Electron emission starts at a gate voltage of 110 V, and reaches a current of 9 uA at 250 V (2.25 mW) with more than 55% of the electrons transmitted through the gate apertures. The devices were also tested as electron impact ionizers using argon. The experimental data demonstrates that the CNT-EIIs can operate at mtorr-level pressures while delivering 60 nA of ion current at 250 V with about 1% ionization efficiency.

This paper reports the design, fabrication, and experimental characterization of a fully microfabricated planar array of externally fed electrospray emitters that produces heavy molecular ions from the ionic liquids EMI-BF₄ and EMI-Im. The microelectromechanical systems (MEMS) electrospray array is composed of the following two microfabricated parts: 1) an emitter die with as many as 502 emitters in 1.13 cm² and 2) an extractor component that provides assembly alignment, electrical insulation, and a common bias voltage to the emitter array. The devices were created using Pyrex and silicon substrates, as well as microfabrication techniques such as deep reactive ion etching, low-temperature fusion bonding, and anodic bonding. The emitters are coated with black silicon, which acts as a wicking material for transporting the liquid to the emitter tips. The extractor electrode uses a 3-D MEMS packaging technology that allows hand assembly of the two components with micrometer-level precision. Experimental characterization of the MEMS electrospray array includes current-voltage characteristics, time-of-flight mass spectrometry, beam divergence, and imprints on a collector. The data show that with both ionic liquids and in both polarities, the electrospray array works in the pure ionic regime, emitting ions with as little as 500 V of bias voltage. The data suggest that the MEMS electrospray array ion source could be used in applications such as coating, printing, etching, and nanosatellite propulsion.

This paper reports the design and experimental validation of an in-plane assembly method for centimeter-scale bulk-microfabricated components. The method uses mesoscaled deep-reactive-ion-etching (DRIE)-patterned cantilevers that deflect and lock into small v-shaped notches as a result of the hand-exerted rotation between the two components of the assembly. The assembly method is intended for MEMS arrays that necessitate a 3-D electrode structure because of their requirement for low leakage currents and high voltages. The advantages of the assembly method include the ability to decouple the process flow of the components, higher overall device yield, modularity, reassembly capability, and tolerance to differential thermal expansion. Both tapered and untapered cantilevers were studied. Modeling of the cantilever set shows that the springs provide low stiffness while the assembly process is in progress and high stiffness once the assembly is completed, which results in a robust assembly. In addition, analysis of the linearly tapered cantilever predicts that the optimal linearly tapered beam has a cantilever tip height equal to 37% of the cantilever base height, which results in more than a threefold increase in the clamping force for a given cantilever length and deflection, compared to the untapered case. The linear taper profile achieves 80% of the optimal nonlinear taper profile, which would be impractical to fabricate. Analysis of the experimental data reveals a biaxial assembly precision of 6.2-mum rms and a standard deviation of 0.6 mum for assembly repeatability. Electrical insulation was investigated using both thin-film coatings and insulating substrates. Leakage currents less than 1 nA at 2 kV were demonstrated. Finally, this paper provides selected experimental data of a gated MEMS electrospray array as an example of the application of the assembly method.

The Carpenter's Rule Theorem states that any chain linkage in the plane can be folded continuously between any two configurations while preserving the bar lengths and without the bars crossing. However, this theorem applies only to strictly simple configurations, where bars intersect only at their common endpoints. We generalize the theorem to self-touching configurations, where bars can touch but not properly cross. At the heart of our proof is a new definition of self-touching configurations of planar linkages, based on an annotated configuration space and limits of nontouching configurations. We show that this definition is equivalent to the previously proposed definition of self-touching configurations, which is based on a combinatorial description of overlapping features. Using our new definition, we prove the generalized Carpenter's Rule Theorem using a topological argument. We believe that our topological methodology provides a powerful tool for manipulating many kinds of self-touching objects, such as 3D hinged assemblies of polygons and rigid origami. In particular, we show how to apply our methodology to extend to self-touching configurations universal reconfigurability results for open chains with slender polygonal adornments, and single-vertex rigid origami with convex cones. Comment: 20 pages, 7 figures