David Conchouso

New Movable Plate for Efficient Millimeter Wave Vertical on-Chip Antenna

A new movable plate concept is presented in this paper to realize mm-wave vertical on-chip antennas through MEMS based post-processing steps in a CMOS compatible process. By virtue of its vertical position, the antenna is isolated from the lossy Si substrate and hence performs with a better efficiency as compared to the horizontal position. In addition, the movable plate concept enables polarization diversity by providing both horizontal and vertical polarizations on the same chip. Through a first iteration fractal bowtie antenna design, dual band (60 and 77 GHz) operation is demonstrated in both horizontal and vertical positions without any change in dimensions or use of switches for two different mediums (Si and air). To support the movable plate concept, the transmission line and antenna are designed on a flexible polyamide, where the former has been optimized to operate in the bent position. The design is highly suitable for compact, low cost and efficient SoC solutions.

A versatile multi-user polyimide surface micromachinning process for MEMS applications

This paper reports a versatile multi-user micro-fabrication process for MEMS devices, the “Polyimide MEMS Multi-User Process” (PiMMPs). The reported process uses polyimide as the structural material and three separate metallization layers that can be interconnected depending on the desired application. This process enables for the first time the development of out-of-plane compliant mechanisms that can be designed using six different physical principles for actuation and sensing on a wafer from a single fabrication run. These principles are electrostatic motion, thermal bimorph actuation, capacitive sensing, magnetic sensing, thermocouple-based sensing and radio frequency transmission and reception.

Characterization of solid UV cross-linked PEGDA for biological applications

This paper reports on solid UV cross-linked Poly(ethylene)-glycol-diacrylate (PEGDA) as a material for microfluidic devices for biological applications. We have evaluated biocompatibility of PEGDA through two separate means: 1) by examining cell viability and attachment on cross-linked PEGDA surfaces for cell culture applications, and 2) by determining if cross-linked PEGDA inhibits the polymerase chain reaction (PCR) processes for on-chip PCR. Through these studies a correlation has been found between degree of curing and cell viability, attachment, as well as on PCR outcome.

CO2?laser-induced bump formation and growth on polystyrene for multi-depth soft lithography molds

This paper reports the process of creating bumps on the surface of polystyrene (PS) induced by a CO2?laser at low powers. The paper also outlines the procedure for growing bumps induced by multiple laser scans on the aforementioned bumps. These bumps result from the net volume gain of the laser heat-affected zone on the PS rather than from a deposition process, and the expansion of the heat-affected zone on PS was verified by measuring the hardness change using nanoindentation. The bumps have a much smoother surface than microchannels fabricated with laser cutting; depending on the laser power, they have heights ranging from hundreds of nanometers to 42??m. The laser scanning speed and scan times along with this technique offer a fast and low-cost alternative for fabricating molds for multi-depth PDMS microfluidic devices.

Development of untethered SU-8 polymer scratch drive microrobots

This paper presents the design, simulation, fabrication and testing of novel, untethered SU-8 polymer microrobots based on scratch drive actuators (SDAs). The design consists of two 100×120×10µm linked SDAs, individually operated close to their resonant frequencies. The resonant frequency and deflection behavior of an individual SDA can be controlled by its shape, thickness, and stiffening design features. As a result, paired SDAs can be actuated individually or simultaneously by a multifrequency driving signal, allowing for two-dimensional displacement. The fabrication process uses SU-8 as structural material and PMGI as sacrificial material. The SU-8 provides a flexible material for the SDAs plates as well as the bushing. Finally, a Cr/Au layer is blanket deposited to provide electrical conductivity.

A pulsed mode electrolytic drug delivery device

This paper reports the design of a proof-of-concept drug delivery device that is actuated using the bubbles formed during electrolysis. The device uses a platinum (Pt) coated nickel (Ni) metal foam and a solid drug in reservoir (SDR) approach to improve the devices performance. This electrochemically-driven pump has many features that are unlike conventional drug delivery devices: it is capable of pumping periodically and being refilled automatically; it features drug release control; and it enables targeted delivery. Pt-coated metal foam is used as a catalytic reforming element, which reduces the period of each delivery cycle. Two methods were used for fabricating the Pt-coated metal: sputtering and electroplating. Of these two methods, the sputtered Pt-coated metal foam has a higher pumping rate; it also has a comparable recombination rate when compared to the electroplated Pt-coated metal foam. The only drawback of this catalytic reformer is that it consumes nickel scaffold. Considering long-term applications, the electroplated Pt metal foam was selected for drug delivery, where a controlled drug release rate of 2.2 μg ± 0.3 μg per actuation pulse was achieved using 4 mW of power.

Crude oil water-cut sensing with disposable laser ablated and inkjet printed RF microfluidics

This paper presents the first microwave microfluidic crude oil/water cut sensor. Anhydrous crude oil is been tested and the device provides a measurable frequency shift of 500MHz at 50% (vol.) water content and a 50MHz shift for a 5% (vol.) water concentration. The sensor is realized with a low-cost direct write fabrication method. This involves laser ablation, inkjet printing, laser heating, along with low temperature thermal compression bonding of Poly (methylmethacrylate) (PMMA) sheets. By using localized laser sintering a conductivity of 2.5e6 S/m is achieved for silver nanoparticle ink without the need to heat the entire substrate above its glass transition temperature of (105 °C). The dielectric properties of PMMA are characterized to 1 GHz and a simulation model is offered for analyzing the dielectric properties of crude oil. This work demonstrates that a small form factor and low cost device is capable of precise water-cut measurements.

Simulation of SU-8 Frequency-Driven Scratch Drive Actuators

This paper presents the simulation of Scratch Drive Actuators (SDAs) for micro-robotic applications. SDAs use electrostatic forces to generate motion on top of an interdigitated electrode array. The purpose of this investigation is to evaluate several design geometries and micro-actuator configurations using ConventorWare®s finite element analysis module. The study performed investigates the SDAs modal and electrostatic behavior and the effects of linking two or more SDAs together in a micro- robot device. In addition, the interdigitated electrode array performance, used for power delivery, was studied by changing the thickness of its dielectric layer. We present our observations based on these studies, which will aid in the understanding and development of future SDA designs.

Out-of-plane platforms with bi-directional thermal bimorph actuation for transducer applications

This paper reports on the Buckled Cantilever Platform (BCP) that allows the manipulation of the out of plane structures through the adjustment of the pitch angle using thermal bimorph micro-actuators. Due to the micro-fabrication process used, the bimorph actuators can be designed to move in both: Counter Clockwise (CCW) and Clockwise (CW) directions with a resolution of up to 110 μm/V, with smallest step in the range of nanometers. Thermal and electrical characterization of the thermal bimorph actuators showed low influence in the platforms temperature and low power consumption (<; 35μW) mainly due to the natural isolation of the structure. Tip displacements larger than 500μm were achieved. The precise angle adjustment achieved through these mechanisms makes them optimal for a range of different MEMS applications, like optical benches and low frequency sweeping sensors and antennas.

Towards a digital sound reconstruction MEMS device: Characterization of a single PZT based piezoelectric actuator

In this paper we report the fabrication and characterization of a single piezoelectric actuator for digital sound reconstruction. This work is the first step towards the implementation of a true digital micro-loudspeaker by means of an array of acoustic actuators. These actuators consist of a flexible membrane fabricated using polyimide, which is actuated using a Lead-Zirconate-Titanate (PZT) piezoelectric ceramic layer working in the d31 actuation mode. The dimensions of the membrane are of 1mm diameter and 4μm in thickness, which is capable of being symmetrically actuated in both upward and downward directions, due to the back etch step releasing the membrane. Our electrical characterization shows an improvement in the polarization of the piezoelectric material after its final etch patterning step, and our mechanical characterization shows the natural modes of resonance of the stacked membrane.