The same hardware base platform is used for both types of network nodes as shown in Figure 3. A similar approach was used by Ying et al. for an IEEE 802.15.4 selleck chemicals based BSN [17]. However, their approach uses mainly local data storage and local analysis this of data. Our master node has a Bluetooth module instead of a sensor. This facilitates Inhibitors,Modulators,Libraries communication with off-the-shelf equipments, e.g., PCs and smart phones. From there, data may be sent to a server for in-depth analysis and/or to a medical professional. In addition, the master node sends out regular time beacons to synchronize the local clocks of the slave Inhibitors,Modulators,Libraries nodes to the master clock, similar to [34]. This is accomplished by calculating the offset between the master clock and the local clock.
The local clock uses Inhibitors,Modulators,Libraries a 32-bit counter driven by a 32 kHz crystal for a stable time base with millisecond Inhibitors,Modulators,Libraries resolution. Data packets from slave nodes are received over the 433 MHz interface and relayed to the Bluetooth interface. Data are framed with a sequence number to detect Inhibitors,Modulators,Libraries missing data packets. An identifier in the data packet is used to identify the unique slave address and sensor type of each network node. On the software side, a ��round-robin software architecture�� is used for the program flow
The fabrication process of the TiO2 nanowire-based gas sensor is shown in Figure 1. Initially, a 0.3 ��m thermal oxide was grown from a (100) p-type Si wafer, as shown in Figure 1(a).
Next, interdigitated Cr/Au electrodes (Cr/Au thickness: 3/300 nm, width: 15 ��m, gap between electrode fingers: 10 ��m) were fabricated Inhibitors,Modulators,Libraries using the photolithography process on an oxidized Si substrate, as shown in Figure 1(b).
Thereafter, 3-nm-thick Inhibitors,Modulators,Libraries Cr and 47-nm-thick Au thin films were blank-deposited on the back of the silicon Cilengitide substrate to create an integrated thin film microheater, as shown in Figure 1(c). The deposition rates for Cr and Au are 0.01 and 0.08 nm?s?1 respectively. Following the fabrication of the backside Inhibitors,Modulators,Libraries heater, standard e-beam lithography was used to pattern the top surface of the chip coated with a 0.6-��m-thick E-Beam resist Zep 520A (ZEON CSC Corp., Xinbi City, Taiwan) with the initial spin rate of 500 rpm for 5 s, followed by a speed ramping from 500 rpm to 5,000 rpm in 5 s, and a final spin rate of 3,000 rpm for 90 s.
A 600 nm thick resist film was then formed.
The lithography conditions (100 pA in current, 7 ��sec/dot in dose time, and ZepN50 for developer) were optimized to produce nanowires with 100 nm and 300 nm in width and 1 ��m in period in a 1 mm2 area. Next, the p-type TiO2 was deposited Entinostat on the top of the chip with a sputter machine followed Tasocitinib by the lift-off technique to form the TiO2 nanowire array (thickness: 300 nm, width: 100 nm, period: 1 ��m), as shown in Figure 1(d). To enhance gas sensor sensitivity, the TiO2 nanowires were annealed at 450 ��C for 1 h with a rapid thermal annealing selleck kinase inhibitor machine prior to packaging.