Core-shell thermally expandable microcapsules were prepared via Pickering suspension polymerization. Acrylonitrile (AN) and methyl methacrylate (MMA) were used as the comonomers and the halloysite nanotubes (HNTs) were used as the Pickering emulsifier. The influence of the HNT concentration, AN/MMA ratio, and types of hydrocarbon was investigated. When the HNT concentration was 0.6 wt%, the microcapsules exhibited a core-shell morphology that contained approximately 35 wt% of the blowing agents with an average particle size of 232.0 μm. Increasing the MMA contents resulted in a larger particle size and lower thermal stability. Core-shell microcapsules could be synthesized using iso-hexane, iso-octane, and n-octane, but microcapsules could not be fabricated with n-pentane. At 1 and 3 bar, the contents of the encapsulated blowing agents were 10 %, whereas the contents of the encapsulated blowing agents were approximately 35 and 60 % at 1.5 and 2 bar, respectively.

In WBAN environment, it is important to achieve energy efficiency of nodes implanting into human body. At the same time, a master also plays an important role in collecting data from nodes and controlling the nodes. By maintaining a master properly, any kinds of situation can be handled. Therefore, low power MAC protocol between a master and a node is highly required appropriately. A MAC protocol proposed in this paper aims to satisfy with these requirements and improve energy consumption rate that tends to grow high as the number of nodes increases. For the efficient and objective evaluation of the proposed MAC protocol, IEEE 802.15.6 MAC is used to compare with it and we show that the advantage of the proposed MAC meet our expectation.

Abstract. Due to the recent development of medical and wireless communication technology, the application range of the WBSN is gradually increased. We measure various biometric data signals directly from the body surface and then to transmit them to the various monitoring devices according to the deifferent application environment. In this paper, we examine TDMA based MAC Protocol in a conventional CSMA/CA networks . The proposed MAC protocol applies the maximum delay restriction in addition to the priority based transmission in order to avoid the occurence of many invaild data due to the long packet delay. Simulation resuts show that proposed scheme provide the reduction of average delay of packet transmission over conventional Bio-MAC protocol. for several biometric signal transmission.

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