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Hot extrusion is a promising method for producing high-performance thermoelectric bismuth telluride alloys because of its ability to create textured microstructures. However, hot extrusion is less favourable for scaling-up because of temperature and strain gradients along the radial direction, and only -textured thermoelectric legs can be obtained because of the fibre-like texture. We suggest a way to overcome these disadvantages by implementing an additional spark plasma sintering process on a stack of extrudates. Using this combined process, we demonstrate the fabrication of 12 × 15 × 13 mm3 p-type (Bi0.2Sb0.8)2Te3 samples from extrudates that had originally been 3 mm in diameter. The evolution of sheet-like texture revealed by SEM, XRD, and EBSD allows us to obtain both - and -textured thermoelectric legs from a single specimen that are desirable for low- and high-temperature applications, respectively. Our results demonstrate the combined method as an industry-friendly process for fabricating high-performance thermoelectric materials.

The electrical resistance of a thermoelectric module is an important parameter as well as the thermoelectric figure-of-merit for the application of both waste energy harvesters and solid-state cooling devices. High resistance causes energy dissipation through Joule heating, leading to the degradation of the device's generating or cooling performance. Therefore, it is highly desirable to reduce the electric resistivity of the thermoelectric materials. Here, we report a hot extrusion technique to fabricate p-type bismuth antimony tellurides that has low electrical resistivity. Extrusion is a promising tool to fabricate a fiber-like texture of the microstructure, where the 001 normal vector of grains is pointing perpendicular to the extrusion direction. Such a textured microstructure can enhance the mobility of electrical carriers along the extrusion direction due to the anisotropic nature of electrical transport in bismuth telluride-based alloys. Beyond bismuth telluride-based thermoelectric materials, we believe that our result will offer a simple tool to manipulate physical properties of any two-dimensional, layered materials by controlling microstructure.

We propose an analog delay line (ADL) that adopts a current-splitting method (CSM) to reduce power consumption. The proposed ADL employs a pipelined sample-and-hold architecture and includes a buffer in the analog memory cell to prevent a charge sharing problem. The CSM reduces power consumption without distorting the sampled data by dividing the current source of the buffer into a holding current source and a buffering current source, which are, respectively, located inside and outside of the analog memory cell. The simulated power consumption of the proposed ADL without and with the CSM is 1080 and $90~{\mu }\text{W}$ , respectively, indicating that the CSM reduces power consumption by 91.7%. The proposed ADL was fabricated using a 0.18- ${\mu }\text{m}$ CMOS process with a 1.8-V supply voltage and occupies an active area of $120 \times 140~{ \mu }\text{m}^{ 2}$ . The sampling capacitor in the analog memory cell was implemented with MOS capacitors instead of metal-insulator-metal capacitors, resulting in an area per unit delay of the proposed ADL of only $600~{ \mu }\text{m}^{ 2}$ , which is much smaller than that in prior works. The measurement results show that the delay of the proposed ADL is accurately controlled from 25 to 475 ns with a unit delay step of 25 ns at a sampling frequency of 40 MHz.

Precise control of carrier density is essential to synthesize high-performance thermoelectric materials. Doping by impurities is often frustrated in n-type Bi2Te3 alloys by incomplete activation, bipolar doping, the formation of secondary phases, and prevailing intrinsic point defects such as vacancies. This weakens the reproducibility of synthesis processes and reduces the long-term reliability of material's performance, hence aging. Here, we explore an impurity-free doping technique to synthesize n-type bismuth tellurium selenides, combining a cold deformation and a hot extrusion. The cold deformation enables controlling the electron density in the range of ∼1019/cm3 via the formation of intrinsic point defects, and the hot extrusion allows texturing the microstructure to enhance the electrical conductivity, hence a large power factor of >5 × 10−3 W-m−1-K−2. We confirm that our process is very reproducible, and the properties of the samples are stable without aging even after thermal stresses. Using this method, we can decouple the relationship between bandgap, carrier density, and composition to improve the high-temperature thermoelectric property. Moreover, we demonstrate the fabrication of high-performance thermoelectric materials from low-graded, raw materials by modifying the degree of the mechanical deformation to reach an optimum carrier density. Our work provides a promising approach to synthesizing n-type thermoelectric materials in the reproducible and adaptable way.

This paper proposes an analog front-end (AFE) IC using a multiple-frequency driving method (MFDM). The proposed AFE IC achieves a high signal-to-noise ratio (SNR) by using an external noise spectrum and locating the frequencies of the excitation signals in low-noise regions. In addition, it employs the MFDM to increase the frame rate by simultaneously sending excitation signals having multiple frequencies to the touch screen panel (TSP). The proposed AFE IC extracts the coordinates of the finger as well as the coordinates, pressure, and tilt angle of the active stylus with the force gauge and gyro sensor. The proposed AFE IC and active stylus were fabricated in a 0.13- $\mu \text{m}$ standard CMOS process. The measurement results show that the proposed AFE IC achieves a frame rate of 3.9 kHz, and SNRs of 61.0 and 50.1 dB when a finger and active stylus are used, respectively. In addition, the pressure and tilt angle of the active stylus are expressed with 6-bit resolution. A capacitive touch system with the proposed AFE IC is demonstrated with a 65-in $104\times 64$ TSP using ten fingers and the active stylus with the pressure and tilt angle.

We employed a hot rolling process to modulate the n-type Bi2Te2.82Se0.18 microstructure. The as-quenched Bi2Te2.82Se0.18 ingot was hot-rolled immediately after heating at 773 K for 1 h. The reduction ratio in the hot rolling process was controlled by changing the rolling gap in a range from 2 mm to 5 mm. With the increase in reduction ratio, the (00 l) planes of Bi2Te2.82Se0.18, which have a higher carrier mobility, were more aligned parallel to the rolling direction and grain refinement was accelerated. Such changes in structural properties led to a drastic enhancement in carrier mobility and increased electron concentration. Consequently, the electrical conductivity of Bi2Te2.82Se0.18 was enhanced by the hot rolling process.

This paper presents a low-noise amplifier (LNA) using attenuation-adaptive noise control (AANC) for ultrasound imaging systems. The proposed AANC reduces unnecessary power consumption of the LNA, which arises from useless noise floor, by controlling the noise floor of the LNA with respect to the attenuation of the ultrasound. In addition, a current feedback amplifier with a source-degenerated input stage reduces variations of the bandwidth and the closed loop gain, which are caused by the AANC. The proposed LNA was fabricated using a 0.18-[Formula: see text] CMOS process. The input-referred voltage noise density of the fabricated LNA is 1.01 [Formula: see text] at the frequency of 5 MHz. The second harmonic distortion is -53.5 dB when the input signal frequency is 5 MHz and the output voltage swing is 2 [Formula: see text]. The power consumption of the LNA using the AANC is 16.2 mW at the supply voltage of 1.8 V, which is reduced to 64% of that without using the AANC. The noise efficiency factor (NEF) of the proposed LNA is 3.69, to our knowledge, which is the lowest NEF compared with previous LNAs for ultrasound imaging.

This paper proposes a capacitive touch sensing system (CTSS) using an adaptive chopper stabilization (ACS) method to achieve high noise immunity. The proposed ACS method quickly detects and adaptively filters out external noises, thereby achieving high noise immunity in the proposed CTSS. To verify the proposed ACS method, a readout integrated circuit (ROIC) was fabricated using a 0.35- $\mu \text{m}$ CMOS process technology with 18 V high-voltage devices and was measured using a 46-in capacitive touch sensor (CTS). When no external noises are induced into the CTS, the measured signal-to-noise ratio (SNR) of the ROIC is 45.8 dB at a reporting rate of 120 Hz. When external noises are induced into the CTS, the measured SNR of the ROIC using the ACS method is 44.5 dB, which is improved by 22.0 dB compared with the SNR achieved without using the ACS method. Therefore, the proposed ACS method effectively eliminates external noises induced into the CTS of the CTSS.

Volatile N-Nitrosamines (NAs), including N-nitrosodimethylamine (NDMA), an emerging contaminant in drinking water, have been reported to induce cancer in animal studies. This study aims to investigate the regional and seasonal distributions of the concentrations of NDMA, one of the most commonly found NAs with high carcinogenicity, in municipal tap water in Korea. NDMA in water samples was quantitatively determined using high-performance liquid chromatography-fluorescence detection (HPLC-FLD) as a 5-dimethylamino-1-naphthalenesulfonyl (dansyl) derivative after optimization to dry the SPE adsorbent and remove dimethylamine prior to derivatization. Tap water samples were collected from 41 sites in Korea, each of which was visited once in summer and once in winter. The average (&plusmn, standard deviation) NDMA concentration among all the sites was 46.6 (&plusmn, 22.7) ng/L, ranging from &lt, 0.13 to 80.7 ng/L. Significant NDMA differences in the regions, excluding the Jeju region, were not found, whereas the average NDMA concentration was statistically higher in winter than in summer. A multiple regression analysis for the entire data set indicated a negative relationship between NDMA concentration and water temperature. High levels of NDMA in Korea may pose excessive cancer risks from the consumption of such drinking water.

Flexible thermoelectric modules (TEMs) are often built with a polymer filler as structural support. However, the filler may serve as a thermal bypass, leading to reduced temperature difference across a TEM and degradation of the output. Herein, we present flexible TEMs made of porous PDMS fillers and Bi2Te3-based thermoelectric legs. The heat conduction through the filler is suppressed by leveraging the low thermal conductivity of porous PDMS (0.08 W/m∙K), leading to an increase in the temperature difference across the TEMs. The porous PDMS TEM exhibits 23% enhanced power density and a figure of merit (ZT) of 0.75 around the room temperature. Lastly, the efficacy of the porous PDMS TEM is demonstrated by testing the TEMs with body heat. Our approach would offer a promising insight into the flexible TEM designs.

The thermoelectric figure-of-merit (zT) is a general standard used to evaluate the performance of thermoelectric materials. However, the performance of thermoelectric devices is largely affected by other properties such as electrical conductivity, thermal conductivity, and the power factor, depending on applications and boundary conditions. Therefore, it is beneficial to have a comprehensive map where the full range of thermoelectric properties are presented to design a high performance thermoelectric module optimized for any customized applications. In this study, we explore the thermoelectric properties of the n-type (1-x)Bi2Te3-xBi2Se3 alloys from x = 0.04 to x = 0.20 with various SbI3 doping levels. We used a hot extrusion technique to obtain a textured microstructure of our specimens to take advantage of their strong anisotropic nature. The SbI3 donor dopant enabled the precise control of electron density in the range of ∼1019 cm−3. Using this process, we constructed a thermoelectric property map as a function of the composition of the bismuth tellurium selenides and doping levels, to provide guidance on designing high performance thermoelectric modules for various applications.

Microbial forensics, exploiting bacteria, archaea, and eukaryotes, has been considered as one of the primary fields to trace the postmortem interval from the decaying cadavers. On the other hand, there remain several challenges of laboratory-based analysis for prediction of postmortem interval, including long-time measurement, complicated measuring procedure, and bacterial growth while carrying samples from the scene. Herein, we introduce the Smart Forensic Kit, which consists of a highly sensitive colorimetric gas sensor, a quality control algorithm, and a smartphone-based analysis method, to quantify the bacterial-derived ammonia gas in real-time. As a result, the estimation system of the postmortem interval has a superior selectivity to the ammonia gas with a detection limit of 38.7 ppb, response linearity to the target bacteria (Escherichia coli, Pseudomonas aeruginosa, and Pseudomonas putida), and short measuring time (10 min) with the maximum predicted postmortem interval from the mouse carcass (168 h). Furthermore, thanks to measuring the postmortem interval within 10 min, the negligible increase rate of bacterial concentration was observed. Consequently, the results reflected a high correlation between the ammonia gas emitted from bacteria and the postmortem interval so that we believe the Smart Forensic Kit will be applied for tracing down the decomposition of the cadavers in the near future.

As the demand for interactive displays continues to increase, capacitive touch systems (CTSs) with stylus-based drawing have become indispensable [1–4]. Passive styli are widely used because of their low-cost implementation, but have low SNR and limited drawing expressions [1]. Active styli have gained interest to solve these problems [4]. The pressure of an active stylus can be expressed using a pressure-to-capacitance transducer [3,4], but the tilt angle has not been reported yet. In addition, analog front-end (AFE) ICs with high frame rates are in demand in response to the fast movements of finger and active styli. Conventional AFE ICs adopt a parallel driving method (PDM) to achieve high SNR, but suffer from low frame rates because the number of rows and columns of the driving matrix increases with the number of TX electrodes [3]. In this paper, an AFE IC with high frame rate using a multiple-frequency driving method (MFDM) is proposed for response to fast movements of fingers and active styli, while expressing both the pressure and tilt angle of the active stylus.

A readout integrated circuit (ROIC) using two-step fastest signal identification (FSI) is proposed to reduce the number of input channels of a data acquisition (DAQ) block with a high-channel reduction ratio. The two-step FSI enables the proposed ROIC to filter out useless input signals that arise from scattering and electrical noise without using complex and bulky circuits. In addition, an asynchronous fastest signal identifier and a self-trimmed comparator are proposed to identify the fastest signal without using a high-frequency clock and to reduce misidentification, respectively. The channel reduction ratio of the proposed ROIC is 16: 1 and can be extended to 16 x N: 1 using N ROICs. To verify the performance of the two-step FSI, the proposed ROIC was implemented into a gamma photon detector module using a Geiger-mode avalanche photodiode with a lutetium-yttrium oxyorthosilicate array. The measured minimum detectable time is 1 ns. The difference of the measured energy and timing resolution between with and without the two-step FSI are 0.8% and 0.2 ns, respectively, which are negligibly small. These measurement results show that the proposed ROIC using the two-step FSI reduces the number of input channels of the DAQ block without sacrificing the performance of the positron emission tomography (PET) systems.