Wearable sensors enable the continuous monitoring of various physiological conditions of individuals without constraints on time and place. Primary vital signs of human body such as; heart rate (HR), Oxygen saturation (SpO2) and respiration rate, can be extracted from the PPG signal. In comparison to conventional inorganic based sensors, the use of organic semiconductor-based devices opens the possibility of devising inexpensive, lightweight, flexible sensors. Reflection-mode PPG sensors overcome the limitations posed by transmission-mode PPG sensor as it can be positioned anywhere on the body. The state of art has not exploited the reflection-mode of PPG sensors extensively, as opposed to transmission-mode. In this work, we have fabricated reflection mode PPG sensor, which comprises of a red (631 nm) organic light emitting diode (OLED) (EQE = 8%) and organic photodetector (OPD) (EQE =47 %) on the same substrate. With motivation to improve the existing PPG sensing technologies, OLED and OPD performances were optimized on a single substrate. Further, we have estimated the best pattern and optimal distance between OLED and OPD in order to maximize signalnoise ratio and lower the power consumption of the device. An analog circuit is designed to read out PPG signals. For realtime pulse monitoring, the signals were sent via a Bluetooth interface to the computer. In summary, a low cost, organic based sensor is developed to detect the heart rate with wireless enabled data monitoring. Our device displayed promising results with 1.5 % error in the heart rate measurement compared to the commercial reference.
Theoretical equations for current-voltage characteristics in mono-layer unipolar devices and multilayer bipolar device
(that is, OLED) are investigated on the basis of the model consisting of diffusion theory of internal carrier emission
through Schottky barrier at cathode and anode electrodes and electronic field dependence of carrier mobility, so called
Pool-Frenkel mobility. Space charge effects are also included in this model, which is not presented as a simple Mott-
Gurney law. The current-voltage characteristics of OLED are presented using a behavioral language for analog systems
(Verilog-A), and the accuracy of this model was verified by comparing with the device simulation results.
We report the observation of sample behaviors using the confocal laser scanning microscopy (CLSM) in on-chip microcapillary. Sample loading by pinched valve injection is observed in a new cross injector shape, which has the structure added conventional cross injector to circle shape. In sample loading, because this structure causes a different electric field compared with that in conventional cross injector, high efficient sample plug injection was performed. It is important to investigate further the detailed sample profiles using the CLSM in sample loading for development of the on-chip microcapillary. We attempt the simulation of sample loading in the cross injector using the semiconductor device simulator MEDICI in order to investigate it in further detail. The sample movements in the channel turn along the Z-direction are observed using the CLSM. In order to miniaturize the microfluidic channel, it is necessarily needed to fold the channel, but then it is inevitable that sample dispersion occurs in the turn. We present sample flow profiles along the Z-direction in the turn using the CLSM and the influence on the electrophoretic separation. Also, we improve that fabrication of duct channel for exhaustion the vaporized xylene to outside the chip and the adhesion process
A very important aspect in the next stage of genomic research will be the study of genetic diversity originating from an individual, for example, a single nucleotide polymorphism (SNP),. For this, the base-pair sequence needs to be determined quickly and easily; along with effectively gathering the proteins that are produced from the cell and depend on each genetic design. To meet these demands, the use of a miniaturized experimental apparatus formed on a chip is suitable as it gives a very small and well-controlled space to undertake precise analyses. This type of chip device needs to be disposable, inexpensive and of uniform quality, therefore many chips should be fabricated at the same time from a low cost chip material such as plastic. A mass production fabrication process for such plastic chips was determined as follows. A thick coating type photoresist was spin-coated onto a 4-inch size Si wafer to 20 μm thickness and patterned by UV-lithography. Thick Au structures were embedded into the resist mold by microelectropolating. After removal of the resist, Au fine structures remained and were used as a metal mold for plastic casting. Plastic, polymethylmethacrylate (PMMA), beads were dissolved in acetone and the polymer solution was cast into the metal mold under vacuum heating environment producing many identical plastic chips at a thickness of 1 mm. The size of the chemical reaction channel, one of the device’s components, was 50 μm in width and 20 μm in depth.