In vivo silicon-based flexible radio frequency integrated circuits monolithically encapsulated with biocompatible liquid crystal polymers.

Biointegrated electronics have been investigated for various healthcare applications which can introduce biomedical systems into the human body. Silicon-based semiconductors perform significant roles of nerve stimulation, signal analysis, and wireless communication in implantable electronics. However, the current large-scale integration (LSI) chips have limitations in in vivo devices due to their rigid and bulky properties. This paper describes in vivo ultrathin silicon-based liquid crystal polymer (LCP) monolithically encapsulated flexible radio frequency integrated circuits (RFICs) for medical wireless communication. The mechanical stability of the LCP encapsulation is supported by finite element analysis simulation. In vivo electrical reliability and bioaffinity of the LCP monoencapsulated RFIC devices are confirmed in rats. In vitro accelerated soak tests are performed with Arrhenius method to estimate the lifetime of LCP monoencapsulated RFICs in a live body. The work could provide an approach to flexible LSI in biointegrated electronics such as an artificial retina and wireless body sensor networks.

Capacitive-loaded interstitial antennas for perfect matching and desirable SAR distributions.

New interstitial antennas are proposed. They basically consist of coaxial cable and two types of capacitive loads. One is tipped at the end of antennas, which helps almost perfect matching possible. The others are located in the middle and needed for better specific absorption rate (SAR) distribution. To distinguish them, one at the end is called the end-capacitive load (ECL) and the others in the middle the middle-capacitive loads (MCLs). Depending on the number of the MCLs, ZMIA (zero MCL interstitial antenna), OMIA (one MCL interstitial antenna) and two MCL interstitial antenna (TMIA) are named and a matching technique based on transmission line theory is suggested. To verify the technique, the three antennas immersed in muscle phantom are designed, fabricated, measured and compared. The measured reflection coefficients of ZMIA, OMIA, and TMIA are -28.4, -21.9, and -22.8 dB, respectively, one of which, -28.4 dB may be considered as the best among those reported. The compared results show that the measured ones are in good agreement with the calculated (predicted) ones. The three antennas are also measured for the SAR distributions. The measured results indicate that the TMIA has the best performance as expected and the region more than 43 degrees C is a rugby ball (major axis 6 cm and minor axis 2.9 cm) with only one TMIA, which confirms that they may be used for the treatment for big-sized and deep-seated tumor or cancer.

Light extraction enhancement from nano-imprinted photonic crystal GaN-based blue light-emitting diodes.

The nano-imprint lithography method was employed to incorporate wide-area (375 x 330 mum(2)) photonic-crystal (PC) patterns onto the top surface of GaN-based LEDs. When the 280-nm-thick p-GaN was partly etched to ~140 nm, the maximal extraction-efficiency was observed without deteriorating electrical properties. After epoxy encapsulation, the light output of the PC LED was enhanced by 25% in comparison to the standard LED without pattern, at a standard current of 20 mA. By three-dimensional finite-difference time-domain method, we found that the extraction efficiency of the LED tends to be saturated as the etch-depth in the GaN epitaxial-layer becomes larger than the wavelength of the guided modes.

An ASIC design for versatile receive front-end electronics of an ultrasonic medical imaging system--16 channel analog inputs and 4 dynamically focused beam outputs.

An ultra large-scale ASIC is designed for the receive front-end electronics of an ultrasonic medical imaging system. The chip receives 16 channel analog rf signals and outputs 4 sets of sample-point-wise dynamically focused partial beam data. Four complete beam data sets are obtained in parallel by simply cascading as many chips as needed in an array system. High resolution of the focusing delay is obtained by nonuniformly selecting each channel data from a quadruply-interpolated rf data stream. The proposed ASIC can be applied to most practical array transducers in the frequency range of 2 to 10 MHz. The digital part of the designed ASIC can be implemented on a chip area of 17.9 microm2 with 0.18 mm CMOS technology, leaving sufficient room for 16 ADCs of 8 bits, 50 MHz on the 5.7 mm x 5.7 mm chip with a 208 pin package.