This paper reports a deep-UV LED package based on silicon MEMS process technology. The package (Si-PKG) consists of a cavity formed by silicon crystalline anisotropic etching, through-silicon vias (TSV) filled with electroplated Cu, bonding metals made of electroplated Ni/AuSn and a quartz lid for hermetic sealing. A deep-UV LED chip is directly mounted in the Si-PKG by AuSn eutectic bonding. It has advantages in terms of heat dissipation, light utilization efficiency, productivity and cost over conventional AlN ceramic packages. We confirmed a light output of 30 mW and effective reflection on Si (111) cavity slopes in the Si-PKG. Further improvement of the optical output is expected.
This paper discusses an integrated hybrid MEMS hydrogen sensor that detects hydrogen in the range from 5 ppm to 100 vol%. The sensor is a single chip comprising both capacitive and thermal conductivity hydrogen sensors that can be fabricated simultaneously using the same process flow. The capacitive sensor detected hydrogen at concentrations as low as 5 ppm without a heater. The thermal conductivity sensor measured high hydrogen concentrations and had a low power consumption of several tens of milliwatts. The integrated hybrid MEMS hydrogen sensor showed a high gas selectivity.
Silicon migration seal (SMS) wafer-level packaging is proposed for high vacuum encapsulation of MEMS. The sealing of vent holes is possible based on silicon surface migration effect at 1100°C in 100% hydrogen ambient without deposition, if the size of the vent holes is properly designed. The feasibility of SMS packaging was experimentally demonstrated using 4 inch wafers. Hermetic sealing was confirmed after 168 hours from the packaging process by diaphragm displacement in the cap wafer.
This paper reports an actuation method of MEMS chiral metamaterial that transforms a two-dimensional MEMS spiral with diameter 150 µm to a three-dimensional spiral by individually pulling the center of spirals. The spiral dimension was designed to work in THz electromagnetic frequency. MEMS spirals were manufactured by bonding the central part of spirals and a Si wafer with Parylene bonding, and were deformed by lifting the Si wafer. It was confirmed that spirals were stably pulled by amplitude of 60 µm at the maximum by relatively separating the spiral and the Si wafer.
We developed a fiber-optic biochemical gas sensor (bio-sniffer) which can measure acetone and isopropanol (IPA) for lipid metabolism evaluation and diabetes screening. We applied to intermittent measurement of the both components in exhaled air. The bio-sniffer utilized a reduction reaction of acetone (pH7.5) and an oxidation reaction of IPA (pH8.5) by secondary alcohol dehydrogenase (S-ADH). The nicotinamide adenine dinucleotide (NADH) consumed (produced) in these reactions was excited by UV light (λ = 340 nm), and the autofluorescence from NADH (λ = 490 nm) was detected by a photomultiplier tube (PMT). Using this principle, we measured acetone and IPA gases intermittently by switching pH and the coenzyme (NADH / NAD+). The dynamic ranges of the sensor were 10-3000 ppb for acetone and 2-1000 ppb for IPA, which encompassed the breath concentration of healthy people (acetone: 200-900 ppb, IPA: 10-30 ppb). Finally, the bio-sniffer was applied to healthy person’s breath and showed the similar responses to the standard gases. These results indicate the usefulness of the bio-sniffer in breath measurement.
A high-sensitive biochemical gas sensor (bio-sniffer) with skin gas cell and gas concentrator for monitoring of ethanol gas concentration emanated from human skin was constructed and demonstrated. This biosensor measured the concentration of ethanol according to the fluorescence intensity change of nicotinamide adenine dinucleotide (NADH), which was produced by an enzymatic reaction of alcohol dehydrogenase. By introducing a gas concentrator using liquid nitrogen, we constructed a highly sensitive system for skin gas measurements. In order to measure skin gas using the bio-sniffer, we designed a measurement system for detecting concentrated gases by connecting the sensor with a gas concentrator and introducing concentrated skin gas to the sensing surface. The monitoring of low concentration of skin ethanol gas was realized after drinking based on alcohol metabolism.
We have developed a new fabrication method of stretchable interconnects using a micro-corrugation machine and a pre-stretched silicone rubber substrate. The fabricated interconnects exhibited >200% stretchability, and their electric resistance was lower than 1 Ω/cm even under the stretch condition. Finally, the stretchable LED circuit with our micro wavy Cu interconnects was demonstrated.