N. F. de Rooij

Low temperature indium-based sealing of microfabricated alkali cells for chip scale atomic clocks

In this paper, the development of a low temperature bonding process focused on indium-based technology for microfabricated alkali cells is presented. The intended application is the use of these cells in chip scale atomic clocks. The existing technology is mainly based on anodic bonding. For some applications, such as where wall coating is used instead of buffer gas, anodic bonding cannot be applied because of the relatively high temperature of the process.

Microfabricated chip-scale rubidium plasma light source for miniature atomic clocks

We present the microfabrication and characterization of a low-power, chip-scale Rb plasma light source, designed for optical pumping in miniature atomic clocks. A dielectric barrier discharge (DBD) configuration is used to ignite a Rb plasma in a micro-fabricated Rb vapor cell on which external indium electrodes were deposited. The device is electrically driven at frequencies between 1 and 36 MHz, and emits 140 μW of stable optical power while coupling less than 6 mW of electrical power to the discharge cell. Optical powers of up to 15 and 9 μW are emitted on the Rb D2 and D1 lines, respectively. Continuous operation of the light source for several weeks has been demonstrated, showing its capacity to maintain stable optical excitation of Rb atoms in chip-scale double-resonance atomic clocks.

Ignition and Combustion Behavior in Solid Propellant Microsystems Using Joule-Effect Igniters

A study of solid propellant ignition and combustion of potassium dinitrobenzofuroxanate in Joule-heating pyrotechnical microelectromechanical systems igniters is carried out using a high-speed framing camera. The effect of igniter geometry, propellant formulation (binder content), fuel mass, and input power level on ignition delay time variability is investigated. Analytical heat transfer models of the ignition process were constructed based on the geometry of the igniters and successfully fitted to experimental ignition delay times. Complete combustion of the propellant drops was observed for fuel masses greater than 100 μg. Flame speeds on the order of tens of centimeters per second were obtained. Two different ignition regimes were observed: a thermal ignition and a direct ignition regime.

P1.8.6 All-additive Inkjet Printed Humidity and Temperature Sensors Fabricated and Encapsulated at Foil Level

We present the simultaneous fabrication at foil level of ambient relative humidity (R.H.) and temperature sensors printed on flexible substrate. These sensors are based on capacitors and resistors and their combination allows the compensation of the R.H. signals variations at different temperatures. The whole fabrication of the system is carried out at foil level and involves the utilization of additive methods, namely inkjet printing and electrodeposition, as well as the final encapsulation of the sensors for protection. The sensors have been characterized and their performances analyzed. The sensitivity of the humidity sensor ranged from 1 fF / 1% R.H. in differential mode operation to 3.5 fF / 1% R.H. in single mode actuation. The thermal coefficient of temperature (TCR) of the thermoresistor was 4.3 x 10 °C. This work demonstrates the potential of inkjet printing in the fabrication at foil level of flexible, light-weight and cost-efficient large arrays of gas sensors.

Integration of a Fabrication Process for an Aluminum Single-Electron Transistor and a Scanning Force Probe for Tuning-Fork-Based Probe Microscopy

In this paper, we report on the integration technique and fabrication of a scanning probe interrogating the location of charges and their tracks inside quantum devices. Our unique approach is to pattern the charged sensor into a high topography micromechanical structure. A single-electron transistor (SET) is directly integrated onto the microfabricated cantilever that extends out from the body of a scanning force microscope (SFM) probe of standard dimensions. In a novel tactic and by reversing their traditional roles, a tuning fork (TF) completes the probe to provide the self-actuating and self-sensing qualities necessary for an oscillatory force sensor. We show sharp edges on the Coulomb diamonds, indication that the SET fabrication step yields devices of high quality. We demonstrate topographical scans with this probe. All stages of the fabrication process are executed on batches of probes which is an essential step away from the time-consuming and individual preparation of other implementations. It opens the door to a more reproducible and large volume production.

Piezoresistive membrane-type surface stress sensor arranged in arrays for cancer diagnosis through breath analysis

We present the fabrication, characterization and successful medical application of a membrane-type surface stress sensor (MSS), arranged in arrays for molecular detection in gaseous phase. Made out of SOI substrate, a round membrane with a diameter of 500 μm and a thickness of 2.5 μm is suspended by four sensing beams with integrated p-type piezoresistors, composing a full Wheatstone bridge. The membrane is coated with a thin polymer layer, which reacts with volatile molecules and produces a deflection of the membrane. The membranes were functionalized with various polymers and characterized as humidity sensors with a sensitivity of 87 mV/%RH and a time constant (Tau63%) of 1.3 s. Finally, through breath analysis and the use of principal component analysis (PCA), we were able, in a double blind trial, to distinguish cancer patients and healthy persons.