Dae-Hyun Baek

Widely Tunable Variable Capacitor With Switching and Latching Mechanisms

A widely tunable variable capacitor using mechanical switching and a reversible latching mechanism was developed. This variable capacitor can increase the total capacitance by utilizing three discrete switches to sequentially connect four sets of fixed capacitors arranged in parallel. Continuous fine tuning is achieved by closing gaps with these interdigitated capacitors, and connected states are maintained through the use of a mechanical latching mechanism. By combining switching and gap-closing modes, a maximum tuning ratio of 9.42 was obtained.

Reversible and continuous latching using a carbon internanotube interface.

Mechanical multistability is greatly beneficial in microelectromechanical systems because it offers multiple stable positioning of movable microstructures without a continuous energy supply. Although mechanical latching components based on multistability have been widely used in microsystems, their latching positions are inherently discrete and the number of stable positions is quite limited because of the lithographical minimum feature size limit of microstructures. We report a novel use of aligned carbon nanotube (CNT) arrays as latching elements in a movable micromechanical device. This CNT-array-based latching mechanism allows stable latching at multiple latching positions, together with reversible and bidirectional latching capabilities. The latching element with integrated CNTs on the sidewalls of microstructures can be adopted for diverse microelectromechanical systems that need precise positioning of movable structures without the necessity of continuous power consumption.

Miniaturized VOC Detectors for Monitoring Indoor Air Quality

With the increased use of chemicals for laundry and cleaning, artificial adhesives, paints, and space heaters indoors, the concentration of volatile organic compounds (VOCs) increases, thus threatening human health. It is known that VOCs are the possible causes of atopic disease and asthma. Some of the VOC species such as formaldehyde and benzene are carcinogenic. The first step to avoid damage from VOCs is to determine their concentration in air. In typical approaches to detect VOCs, an adsorbent to capture the gas molecules of the VOCs is placed in the area of interest and taken to a laboratory, and subsequently, the VOCs are thermally desorbed and directed to large-sized detectors; the entire process is time-consuming and costly. With the increased public awareness of the hazards of VOCs, research on the cost-effective detection of VOCs using small personal devices has become more active. In this chapter, fundamental technologies to detect VOCs are introduced, and current research works are discussed on low-cost sensing of VOCs using miniaturized devices to evaluate indoor air quality.

Variable capacitor with switching mechanism for wide tuning range

We developed a variable capacitor with mechanical switching mechanism and reversible mechanical latching component to enhance tuning ratio. The switching mechanism could connect four sets of capacitors arranged in parallel sequentially by controlling the displacement of a microactuator for abrupt and coarse tuning of total capacitance. Continuous and fine tuning was also achieved by gap-closing mode of interdigitated capacitors. The resultant maximum tuning ratio was 5.71 by combining coarse and fine tuning.

Continuously latchable shuttle using carbon nanotubes on sidewall surfaces

We demonstrated a novel usage of self-adjusted, vertically aligned carbon nanotube (CNT) arrays integrated on the sidewalls of microstructures as latching components. The CNT array-based latching mechanism showed stable latching at multiple latching positions, together with reversible and bidirectional latching capabilities. The latchable shuttle using CNT latch could be adopted for diverse microelectromechanical systems (MEMS) that need precise positioning of movable structures without the necessity of continuous power consumptions to hold the displaced position.