Post-fabrication Assembly Research Articles

Micro Metal Additive Manufactured Low-Loss Slotted Rectangular Waveguides Operating at 220-500 GHz

This paper reports the design, fabrication and measurement techniques for a set of low-loss slotted waveguides. The waveguides are fabricated based on a micro metal additive manufacturing technology. They were fabricated layer by layer in one piece without the need of post-fabrication assembly. As examples, straight waveguides in WR-3.4 (220-330°GHz) and WR-2.2 (330-500°GHz) bands were fabricated and tested. Measurement results show the insertion loss per unit length is 0.0615-0.122°dB/mm and 0.116-0.281°dB/mm, respectively.

Plasma Activated Bonding for an Enhanced Alignment Electrostatic Lens

Abstract This article presents the design and fabrication of an electrostatic lens unit for the focusing of an electrospray beam. In our design, the post fabrication assembly is eliminated when silicon electrodes and glass spacers are permanently bonded using plasma activated wafer bonding. Minimizing fabrication errors and electrodes misalignment are essential in order to minimize geometrical aberration sources such as astigmatism. Our fabrication process allows etching each electrode in a separate step and eliminates aperture size mismatch. The glass standoffs in the lens unit provide a breakdown voltage of up to 22kV for focusing in vacuum.

High-density optrodes for multi-scale electrophysiology and optogenetic stimulation.

We demonstrate the design and implementation of hybrid optical-electrical probes (`optrodes') for high resolution electrophysiology and optogenetic stimulation of neurons in multiple brain areas. Our 64-channel implantable optrodes are minimally invasive (50 μm × 20 μm) and span 1~2 mm. To minimize tethering forces on the brain tissue a monolithic high-density flexible cable (6 μm thin) connects the probe to a lightweight headstage (1.3 gr, 256 channel configuration) designed for awake, freely-behaving small animals. A polymer-based multi-channel photonic light delivery system is integrated on shank in a separate layer, providing local optogenetic stimulation of the neural population adjacent to the probe. The entire manufacturing process, including the nanofabrication of the optrodes, post-fabrication assembly, and surgical implantation procedures are designed to be scalable, high-yield, and high-throughput.

Microfabricated Flexible Electrodes for Multiaxis Sensing in the Large Plasma Device at UCLA

As conventional sensors are scaled down in size for proper usage in high-density laboratory plasmas, they become harder to construct reliably by hand. Devices fabricated utilizing microelectromechanical systems (MEMS) techniques are superior to hand-made devices in terms of size scale, process control, and precision. Microprobes give experimentalists the ability to take direct measurements under controlled conditions. This paper discusses flexible MEMS multiaxis probes that have been developed for use in the Large Plasma Device, a cathode-discharge plasma, at UCLA. The probes are custom built and tailored to fit the unique specifications of individual experiments. Postfabrication assembly also allows for simultaneous sensing in multiple axis. MEMS electric-field probes have been successfully used to detect electron solitary structures in a high-density plasma that are predicted in theory but never seen before except in low-density space plasmas.

Integration of Electroactive Polymers in MEMS Ultrasonic Sensors

The U.S. Army AMRDEC, Stanley Associates, and the Georgia Institute of Technology are developing spectrally sensitive acoustic emission sensors for the detection of various phenomena of interest in Army missiles and assets. Multiple systems would benefit from monitoring the acoustic spectrum and identifying signatures of interest. These would include monitoring sounds external to Unattended Ground Sensors, looking for specific sounds associated with machine failure in a condition-based maintenance scenario, and identifying items that are impacting each other. Potential device designs employ electroactive polymers to convert acoustic waves into electrical impulses. Many electroactive polymers are, however, not compatible with standard MEMS processing, particularly at elevated temperatures. Piezoelectric films, such as PVDF, require stretching and poling processes to orient the crystal structure. Electret films also require poling to create a permanent polarization, plus discharge occurs at relatively low-temperatures. These types of films are difficult to integrate directly into MEMS devices because of these incompatible processes. The films are therefore added using post-fabrication bonding and assembly processes, thus reducing design flexibility and increasing cost. This paper will present techniques being developed to integrate electroactive polymers directly in MEMS sensors as opposed to performing post-fabrication assembly of electroactive films into sensor structures.

Mass-producible monolithic silicon probes for scanning probe microscopes

In this paper, we describe the design, fabrication, and testing of monolithically micromachined silicon probes for scanning probe microscope (SPM) applications. An SPM probe consists of three parts: an atomically sharp tip, a supporting flexural beam, and a handle. Unique design and fabrication processes allow probes with uniform geometry to be developed efficiently. The process is robust, as no time-critical steps are involved. Tips are formed by anisotropic etching followed by oxidation sharpening. Monolithic process enhances reliability of the probe by eliminating post-fabrication assembly steps such as wafer bonding. We have demonstrated SPM probes with excellent mechanical characteristics, including high resonant frequency and zero intrinsic bending.