Applications of Carbonized Parylene for Sensor Technology
Ted Harder, Yu-Chong Tai

Abstract. Currently I am working on a new material, carbonized parylene. This new material provides a cheap easy and flexible way to micromachine carbon on a silicon substrate. This form of carbon has great potential for a large number of sensors. Currently we are investigating it as a humidity sensor, NO (nitrous oxygen) sensor and its application to a bolometer (infrared light/heat sensor).

During the last six months we have investigated the pyrolysis process by which we carbonize parylene and several of the fundamental material properties. We have found that the material is highly porous which means the film has a high amount of surface area. We have also characterized the temperature coefficient of resistance which can be used in both the bolometer and in high temperature heaters.

Several fabrication related challenges have been characterized and the process has been modified to improve the overall potential of the fabrication process.

Due to the importance of carbon various types of chemical sensing and its inertness, the ability to micromachine a form of carbon has implications for a wide variety of novel sensors.

Athermal Holographic Filters
Hung-Te Hsieh, Demetri Psaltis, Yu-Chong Tai

Abstract. Holographic filters are used as optical sensors and in wavelength division multiplexing (WDM) filtering applications. Temperature dependence is a critical concern for telecommunications. We realize the design of an athermal holographic filter employing a thermally actuated MEMS mirror to compensate for the drift of Bragg wavelength due to changes of temperature. The center wavelength of our holographic filter is shown to remain constant from 21°C to 60°C. (full report)

Uncooled All-Parylene Bolometer
Matthieu Liger, Yu-Chong Tai

We present here a novel, low-cost uncooled parylene bolometer. The device is made of two layers of pyrolyzed parylene and a metal layer for interconnections. We demonstrate that high responsivity can be achieved by tailoring the electrical conductivity and the temperature coefficient of resistance (TCR) using different pyrolysis conditions for each parylene layer.
(full report)

Parylene Technology for Mechanically Robust Neuro-Cages
Ellis Meng, Yu-Chong Tai, Jon Erickson, and Jerome Pine

Abstract. We present a novel process to produce parylene cages for the in vitro study of cultured neural networks. For the first time, a neuro-cage fabrication technology is demonstrated that is scalable to high density cage arrays and able to withstand the chemical and mechanical rigors of supporting cellular cultures for long-term study.
(full report)

Nano-to-Micro Self-Assembly Using Shear Flow Devices
Chi-Yuan Shih, Siyang Zheng, Ellis Meng, Yu-Chong Tai (Yi Liu and J. Frazer Stoddart)

It will be extremely useful if there’s a way to precisely assemble nano-materials into micro- or even meso-scale devices. For example, our long-term goal is to use massively architected motor-molecules [1] to build muscle-like actuators, in which these molecules work in parallel to output large forces. Unfortunately, the lack of such an assembly method is still the major barrier in the whole bottom-up nanotechnology field. This work aims at attacking this problem and as an important first step, we report here the successful development of a much improved shear-flow-enhanced self-assembly method over the baseline spontaneous assembly method in test tubes [2]. More specifically, we have engineered special thiolated model molecules (bisdisulfide/C28H34O4S4) and demonstrated the nano-to-micro self-assembly using thiol-gold bonding chemistry. Our method has produced gold/molecule aggregates as big as 50_m that are completely made of 30nm gold nanoparticles and 3nm model molecules. Fig.1 shows the idea of our shear-flow assembly. The interface of two shear flows is where gold nanoparticles meet with the thiolated molecules, herein the aggregation happens. The important advantages of this approach are twofold. The first is to limit the assembly only at interface for controlled assembly. The second advantage is the unsaturated growth of aggregate because shear flows continue to supply fresh nano-materials to the interface, leading to large aggregates. To implement this design, we fabricate two types of shear flow devices (Fig.2). For water or ethanol solvent system, PDMS/glass devices are used for easy plumbing and observation. For non-polar solvents like acetone and dichloromethane, glass/silicon devices are used to avoid PDMS swelling. (full report)