A multichannel/multicolor visible light communication (VLC) system using entirely organic components, including organic light emitting diodes (OLEDs) and organic photodiodes (OPDs), is developed to ...demonstrate indoor lighting applications where the integration of OLEDs and OPDs has significant potential. To achieve this, tricolor (Red/Green/Blue(R/G/B))‐selective OPD arrays for the receiver and tricolor OLED arrays for the emitter are developed. For (R/G/B)‐selective OPDs, a Fabry–Pérot electrode to enhance color selectivity and a thick junction structure to effectively accommodate a wide range of driving voltages are introduced. For tricolor OLEDs, fluorescent‐emitting materials are used to enhance the operating frequency in addition to introducing a cavity structure to achieve narrow emission. Utilizing these spectrally refined tricolor OPDs/OLEDs, a VLC system is designed for indoor lighting applications, and a systematic analysis of their signal‐to‐interference ratio dependence on the distance or angle between the transmitter and receiver is performed. The study's findings indicate the importance of emission angle‐dependent wavelength shift of the OLED and the luminosity function, which varies with wavelength, in the R/G/B mixed‐white‐light‐based VLC systems. Finally, the feasibility of VLC using tricolor OPDs/OLEDs in the real‐life context of indoor white‐color lighting is demonstrated, showing that the transmitted data patterns well‐matched the received data patterns.
A visible light communication platform using (R/G/B)‐selective organic photodiode arrays as receivers and (R/G/B) organic light‐emitting diodes as emitters is developed and analyzed to study how the geometry effect of each organic receiver and emitter affects data transmission. Based on this, the first organic material‐based white‐light optical communication system is demonstrated.
This article presents a 1984-pixel retinal prosthesis (RP) chip with time-domain in-pixel image processing. The proposed time-domain image processing (TDIP) algorithm efficiently generates the ...edge-extracted stimulation and significantly reduces the stimulus power consumption. For the area-and power-efficient time-domain processing, a leakage current-based pulsewidth comparator (PWC) and its control scheme are also proposed. The proposed RP chip adopts the bipolar stimulation-based local return that minimizes image dispersion and a sequence control scheme that produces 1984 stimulation points with 1024 electrodes. The RP chip was implemented in a 180 nm CMOS process and achieved a power consumption of 1.26 nW/pixel, which is <inline-formula> <tex-math notation="LaTeX">\times</tex-math> </inline-formula>44.7 better than the previous state-of-the-art image processing RP chip.
When the intensity of the incident light increases, the photocurrents of organic photodiodes (OPDs) exhibit relatively early saturation, due to which OPDs cannot easily detect objects against strong ...backlights, such as sunlight. In this study, this problem is addressed by introducing a light‐intensity‐dependent transition of the operation mode, such that the operation mode of the OPD autonomously changes to overcome early photocurrent saturation as the incident light intensity passes the threshold intensity. The photoactive layer is doped with a strategically designed and synthesized molecular switch, 1,2‐bis‐(2‐methyl‐5‐(4‐cyanobiphenyl)‐3‐thienyl)tetrafluorobenzene (DAB). The proposed OPD exhibits a typical OPD performance with an external quantum efficiency (EQE) of <100% and a photomultiplication behavior with an EQE of >100% under low‐intensity and high‐intensity light illuminations, respectively, thereby resulting in an extension of the photoresponse linearity to a light intensity of 434 mW cm−2. This unique and reversible transition of the operation mode can be explained by the unbalanced quantum yield of photocyclization/photocycloreversion of the molecular switch. The details of the operation mechanism are discussed in conjunction with various photophysical analyses. Furthermore, they establish a prototype image sensor with an array of molecular‐switch‐embedded OPD pixels to demonstrate their extremely high sensitivity against strong light illumination.
A molecular‐switch‐embedded organic photodiode exhibits an autonomous transition of the operation mode between photovoltaic‐ and photomultiplication‐type photodiodes, resulting in the extension of the photoresponse linearity to 434 W cm−2. This mechanism is enabled by the light‐intensity‐adjusted cyclization–cycloreversion equilibrium of diarylethene‐based molecular switches. Consequently, prototype image sensors with reliable sensitivity against strong backlight are demonstrated.
This brief presents a current to digital convertor (CDC) with low power, wide dynamic range and fast conversion speed. Proposed coarse converter extends the maximum input current range, and achieves ...fast conversion speed with the input adaptive control scheme. Capacitive transimpedance amplifier (CTIA) based fine converter digitizes the residue current and achieves fine resolution. Proposed mixed-signal coarse-fine subrange normalization technique enables seamless processing of the final converter output. The proposed CDC implemented in 0.18 μm CMOS process converts input current up to 512 μA with 7.8125nA resolution and 400 μs conversion time. Power consumption is 79.4 μW.
This paper presents a 288-pixel retinal prosthesis (RP) chip implemented in a 0.18 μm CMOS process. The proposed light-to-stimulus duration converter (LSDC) and biphasic stimulator generate a wide ...range of retinal stimuli proportional to the incident light intensity at a low supply voltage of 1V. The implemented chip shows 25.5 dB dynamic stimulation range and the state-of-the art low power consumption of 4.49 nW/pixel. Ex-vivo experiments were performed with a mouse retina and patch-clamp recording. The electrical artifact recorded by the patch electrode demonstrates that the proposed chip can generate electrical stimuli that have different pulse durations depending on the light intensity. Correspondingly, the spike counts in a retinal ganglion cell (RGC) were successfully modulated by the brightness of the light stimuli.
This brief proposes a fully integrated output capacitor-less low-dropout regulator (LDO) using a voltage difference to time converter (VDTC). Proposed dynamic amplifier based VDTC allows low voltage ...operation and significantly reduces the quiescent current. The linear characteristics of VDTC result in output ripple-less operation and good regulation performance. Using direct output feedback through a small coupling capacitor, the gate voltage of the power transistor is instantly compensated to mitigate fluctuation of the output voltage when a sharp load transient occurs. Fabricated in 65 nm LP CMOS, the proposed LDO demonstrates a wide operation range with an input voltage range of 0.6-1.2 V and a load current of over 30 mA across all voltages without an output capacitor. With reduced output impedance due to direct output feedback, the measured undershoot is 158 mV, which is recovered in 9.6 μs, when the load current changes by 28 mA in 1 ns. The peak current efficiency is more than 99.99% and the figure of merit (FOM) is 0.202 fs. The active area of the control block is 0.002 mm 2 .
This article presents a pixelated monolithic CMOS photoplethysmography (PPG) sensor. The spiking neural network (SNN)-inspired architecture, which includes an unbiased photodiode (PD)-based ...light-to-digital converter (LDC), efficiently converts spatial features of PPG signals to multiple pixelated outputs. The sensor consists of 144 light-sensing neurons (LSNs) and simultaneously generates 1 b 12 row/12 column-wise pixelated outputs. The spatial features of the PPG signals are thoroughly studied with measurement results. Moreover, ambient light canceling with independent component analysis (ICA) is demonstrated as a key application of the proposed sensor. The sensor chip achieves 114 dB dynamic range while consuming 23.3 <inline-formula> <tex-math notation="LaTeX">\mu </tex-math> </inline-formula>W at 1-V supply voltage.
The goal of this study was to develop a Korean version of the Global Physical Activity Questionnaire (K-GPAQ) and to examine its reliability and validity. The English version of the GPAQ was ...translated to the Korean language (K-GPAQ) via forward–backward translation. Reliability of the K-GPAQ was evaluated using a one-week interval test–retest method with 115 individuals. Criterion-related validity of the K-GPAQ was examined with 199 participants using accelerometers. Cohen’s kappa and Spearman’s correlation coefficients were used to measure test–retest reliability and validity, respectively. A Bland–Altman analysis was used to assess agreement between physical activity (PA) levels measured via K-GPAQ and the accelerometer. Coefficients for the reliability of the K-GPAQ showed moderate agreement for recreational PA and slight agreement for work-related PA (Cohen’s kappa: 0.60–0.67 for recreational PA and 0.30–0.38 for work-related PA and Spearman’s rho: 0.27–0.47 for work-related PA and 0.53–0.70 for recreational PA). Criterion validity of the total amount of PA, as measured by the K-GPAQ and the accelerometer, showed a weak but significant correlation (r = 0.34, p < 0.01). The K-GPAQ is a reliable and valid questionnaire to measure PA although K-GPAQ overestimated PA levels.
Although steroids are suggested as the treatment of choice for infantile spasms, the mechanism of action is still unclear. Using a rat model of malformation of cortical development with refractory ...infantile spasms, we evaluated the efficacy of methylprednisolone on spasms susceptibility and behaviors. Additionally, we investigated the in vivo electrophysiological and neurochemical changes of the brain after methylprednisolone treatment. Infant rats with prenatal exposure of methylazoxymethanol at gestational day 15 were used. After a single dose of methylprednisolone or three different doses of methylprednisolone for 3 days, spasms were triggered by intraperitoneal injection of N‐methyl‐d‐aspartic acid. In rats with 3 days of methylprednisolone pretreatment and their controls, behavioral testing was performed at postnatal day 15. In vivo magnetic resonance imaging was conducted at postnatal day 15 after 3 days of methylprednisolone treatment. The rats with single methylprednisolone pretreatment showed significantly delayed onset of spasms and multiple doses of methylprednisolone significantly suppressed the development of spasms in a dose‐dependent manner. After multiple methylprednisolone pretreatment and a cluster of N‐methyl‐d‐aspartic acid‐induced spasms, the rats showed significantly increased freezing behaviors to conditioned stimuli. Glutamate‐weighted chemical exchange saturation transfer revealed significant elevation of glutamate concentration in the cortices of the rats with multiple methylprednisolone pretreatments. Methylprednisolone pretreatment could attenuate N‐methyl‐d‐aspartic acid‐induced spasms with in vivo neurochemical and electrophysiological changes, which indicates this steroid's action on the brain and in epilepsy.
Using a rat model of infantile spasms with malformation of cortical development, we could prove the dose‐dependent efficacy of methylprednisolone on spasms. Moreover, multiple doses of methylprednisolone lead to in vivo neurochemical changes with increased glutamate concentration in the cortex and electrophysiological changes in fast oscillations in the neocortex with reduced spasms susceptibility. These in vivo neurochemical and electrophysiological changes caused by methylprednisolone can be more therapeutic evidence of steroids in neurological disorders, including epilepsy.
This paper presents a simultaneous bidirectional asymmetrical serial interface architecture for sensor systems. The proposed current/voltage dual-mode signaling scheme provides system synchronous ...clock and continuous data transmission between sensor integrated circuit (IC) and system-on-a-chip (SoC) using a single wire, which minimizes pin requirements on packages. Two types of transceiver circuits were implemented in a 65 nm CMOS technology for the sensor IC and the SoC, and they were designed for transmission rates of 1 Mb/s and 250 Kb/s, core areas of 0.008 mm 2 and 0.142 mm 2 , and power consumptions of 7.1 μW and 145.8 μW, respectively. The transceiver circuit for the sensor IC was also applied to a monolithic PPG sensor implemented in 180 nm CMOS, and the acquisition and transmission of PPG sensor data with the transceiver for the SoC, implemented in 65 nm, was successfully achieved.
