Young Chang Jo

Low power capacitive humidity sensor readout IC with on-chip temperature sensor and full digital output for USN applications

In this paper, a low power CMOS integrated capacitance-to-frequency converter with on-chip temperature sensor and fully digital output designed for humidity sensor interface is newly proposed, which is manufactured by using a standard 0.35um 2P/3M CMOS process. This ROIC(Readout IC) consists of on-chip PTAT temperature sensing circuit, low power temperature-to-frequency converter, low power C-F converter, digital compensation circuit, OTP memory, control logic and serial I/O circuits. Capacitance interfacing capability of the circuit is ultra-wide, up to 350pF, which is higher than previously reported works1. At a clock speed of 1MHz, the average power dissipation is as low as about 150uW with one humidity measurement per one second, which is lower than ever reported works2,3. And the minimum detectable capacitance is as low as about 4.5fF.

A low-power silicon-on-insulator photodetector with a nanometer-scale wire for highly integrated circuit

A highly sensitive photodetector, which is fabricated on a silicon-on-insulator metal oxide semiconductor field-effect transistor (SOI MOSFET) with a nanometer-scale wire, is proposed and optical responses are studied. Experimental results show that our device has a responsivity of 36 A/W, which is significantly higher than that of the conventional SOI MOSFET, and a significantly lower dark current. Interestingly, the photodetector with wire also shows pseudo kinks in a fully depleted type. We consider that these phenomena are affected by the wire, and the physical mechanism of the operation of our photodetector is explained by a strong lateral bipolar action. The linearity with optical power and spectral response in the visual spectral range are presented. Our device can be easily downscaled below 0.1 µm without the loss of sensitivity and the increase in dark current.

Novel wearable-type biometric devices based on skin tissue optics with multispectral LED–photodiode matrix

In this study, we examined the possibility of using a multispectral skin photomatrix (MSP) module as a novel biometric device. The MSP device measures optical patterns of the wrist skin tissue. Optical patterns consist of 2 × 8 photocurrent intensities of photodiode arrays, which are generated by optical transmission and diffuse reflection of photons from LED light sources with variable wavelengths into the wrist skin tissue. Optical patterns detected by the MSP device provide information on both the surface and subsurface characteristics of the human skin tissue. We found that in the 21 subjects we studied, they showed their unique characteristics, as determined using several wavelengths of light. The experimental results show that the best personal identification accuracy can be acquired using a combination of infrared light and yellow light. This novel biometric device, the MSP module, exhibited an excellent false acceptance rate (FAR) of 0.3% and a false rejection rate (FRR) of 0.0%, which are better than those of commercialized biometric devices such as a fingerprint biometric system. From these experimental results, we found that people exhibit unique optical patterns of their inner-wrist skin tissue and this uniqueness could be used for developing novel high-accuracy personal identification devices.

The Fine Scratches of the Spectacle Frames and the Allergic Contact Dermatitis

Background Spectacle contact allergy is not infrequent. The fine scratches on the spectacle frames which may play a role in the sensitization to the potential allergenic components have not been studied. Objective We sought the relationship between the scratches on the spectacle frames and the allergic contact dermatitis (ACD) in the Republic of Korea. Methods A total of 42 Korean patients with ACD at the spectacle contact sites were enrolled. Their spectacle frames were examined with the dimethylglyoxime (DMG) test and analyzed by the scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Patch tests (thin-layer rapid use epicutaneous test [TRUE tests]) were performed to identify the skin allergens. Results The DMG-positive spectacle frames were identified in 78.5% of the frames. The SEM results showed that there were more scratches on the skin-contacting parts of the spectacle frames than the non-skin-contacting parts of the same frames. In the EDS findings, the mean nickel content (weight, %) of the spectacle frames was 15.7±5.5, and the mean chromium content was 20.3±3.4 at the skin-contacting parts. In the TRUE tests, nickel sulphate was the most common allergen (31 cases, 73.8%), and potassium dichromate was the second (9 cases, 21.4%). Three patients presented simultaneous positive reactions with nickel sulphate and potassium dichromate. Conclusion Minor visible and non-visible fine scratches on the spectacle frames may present the provocation factors of the ACD. Nickel sulphate was the most common allergen suspected of provoking the spectacle frame-induced ACD, followed by potassium dichromate.

An optical system to measure the thickness of the subcutaneous adipose tissue layer

To measure the thickness of the subcutaneous adipose tissue layer, a novel non-invasive optical measurement system (λ=1300 nm) is introduced. Animal and human subjects are used for the experiments. The results of human subjects are compared with the data of ultrasound device measurements, and a high correlation (r=0.94 for n=11) is observed. There are two modes in the corresponding signals measured by the optical system, which can be explained by two-layered and three-layered tissue models. If the target tissue is thinner than the critical thickness, detected data using diffuse reflectance method follow the three-layered tissue model, so the data increase as the thickness increases. On the other hand, if the target tissue is thicker than the critical thickness, the data follow the two-layered tissue model, so they decrease as the thickness increases.

The microneedle roller is an effective device for enhancing transdermal drug delivery.

from generalized pustular psoriasis. J Cutan Pathol 2010; in press. 8 Andersen KE, Hjorth N, Menné T. The baboon syndrome: systemically-induced allergic contact dermatitis. Contact Dermatitis 1984; 10: 97–100. 9 Kamann S, Bauer C, Fackler I, Przybilla B. Anaphylaxis caused by omeprazole. Hautarzt 2006; 57: 1016–1020. 10 Casacci M, Lebas D, Decamps F. Toxic epidermal necrolysis due to omeprazole. Eur J Dermatol 2006; 16: 699–700.

Design and Optical Characterization of Passive Pixel with Sensitivity-Improved InGaAs/InP Phototransistors Considering Light-Dependent Shunt Resistance for Near Infrared Imaging Applications

In this study, a InGaAs/InP passive unit pixel with an optical-sensitivity-improved heterojunction phototransistor (HPT) for array imaging applications has been designed and characterized for low-light signal detection considering light-dependent shunt resistance. Using the proposed devices, a 1×256 highly sensitive linear array chip with suitable shunt resistance has been fabricated and characterized. The designed passive unit pixel consists of one photodetector and one select transistor with a collector–base terminal tied configuration for a wide dynamic range. We also present epitaxial structures and an equivalent model to optimize optical gain and shunt resistance characteristics. The device operation mechanism and experimental results are discussed. The experimental results show that our device has an optical sensitivity of 118 A/W, which is significantly higher than that of a conventional PIN photodetector with the same light-absorbing area. This high sensitivity originates from the optical gain-enhanced device structure. A typical optical gain is approximately 236, which means HPTs are 236-fold more sensitive than PIN photodetectors. The proposed HPT also has tens of kΩ shunt resistance with high optical sensitivity under low illumination, which is sufficient for effective signal conversion through a transimpedance amplifier circuit.

A low power SOI MOSFET photodetector with a nanometer scale wire for highly integrated circuit

In this paper, the optical and electric characteristics of SOI MOSFET photodetector device with a nanometer scale wire are investigated.

A Wearable Wrist Band-Type System for Multimodal Biometrics Integrated with Multispectral Skin Photomatrix and Electrocardiogram Sensors

Multimodal biometrics are promising for providing a strong security level for personal authentication, yet the implementation of a multimodal biometric system for practical usage need to meet such criteria that multimodal biometric signals should be easy to acquire but not easily compromised. We developed a wearable wrist band integrated with multispectral skin photomatrix (MSP) and electrocardiogram (ECG) sensors to improve the issues of collectability, performance and circumvention of multimodal biometric authentication. The band was designed to ensure collectability by sensing both MSP and ECG easily and to achieve high authentication performance with low computation, efficient memory usage, and relatively fast response. Acquisition of MSP and ECG using contact-based sensors could also prevent remote access to personal data. Personal authentication with multimodal biometrics using the integrated wearable wrist band was evaluated in 150 subjects and resulted in 0.2% equal error rate (EER) and 100% detection probability at 1% FAR (false acceptance rate) (PD.1), which is comparable to other state-of-the-art multimodal biometrics. An additional investigation with a separate MSP sensor, which enhanced contact with the skin, along with ECG reached 0.1% EER and 100% PD.1, showing a great potential of our in-house wearable band for practical applications. The results of this study demonstrate that our newly developed wearable wrist band may provide a reliable and easy-to-use multimodal biometric solution for personal authentication.

Electroencephalographic feature evaluation for improving personal authentication performance

Abstract Electroencephalography (EEG), a method of continuously recording the electrical activity of the brain, provides signals that are among the most promising types of information usable in vital biometrics. However, reliable biometrics based on EEG are still under development since it remains unclear how to extract EEG features that can be used to identify individuals the most effectively. In this study, new EEG features for use in biometrics were proposed and their effectiveness for personal authentication was demonstrated using an open-access EEG database containing 109 personal EEG datasets. From the EEG signals, we extracted 10 single-channel features (seven spectral and three nonlinear) by performing spectral and nonlinear analyses and 10 multichannel features by conducting network analysis based on phase synchronization. A distance-based classifier was built based on the extracted features to distinguish the self from the others. The performance of the proposed personal authentication scheme was assessed in terms of the equal error rate (EER) and false rejection rate (FRR) when the false acceptance rate (FAR) was fixed at 1%. The EER was 0.73% with the eyes open (REO) and 1.80% with the eyes closed (REC), and the FRR with a 1% FAR was 1.10% (REO) and 2.20% (REC). These results are superior to those of previous studies in which the same database was used. In addition, the nonlinear and network features appeared more important than the spectral features for authentication. This method of utilizing EEG features for personal authentication is expected to facilitate the advancement of EEG-based biometric systems.