With the increasing demand for Internet of Things (IoT) with integrated wireless sensor networks (WSNs), sustainable power supply and management have become important issues to be addressed. Thermal ...energy in forms of waste heat or metabolic heat is a promising source for reliably supplying power to electronic devices; for instance, thermoelectric power generators are widely being researched as they are able to convert thermal energy into electricity. This paper specifically looks over the application of thermoelectricity as a sustainable power source for IoT including WSNs. Also, we discuss a few thermoelectric systems capable of operating electronic skin (e-skin) sensors despite their low output power from body heat. For a more accurate analysis on body heat harvesting, models of the human thermoregulatory system have been investigated. In addition, some clever designs of heat sinks that can be integrated with thermoelectric systems have also been introduced. For their power management, the integration with a DC-DC converter is addressed to boost its low output voltage to a more usable level.
There is an increasing demand for power sources of wearable sensors and personal refrigeration. Flexible thermoelectric device (FTED) can be ideal candidate for such purpose. This paper reports on a ...compact, high-power and flexible thermoelectric device based on a bulk thermoelectric (TE) material. For thermoelectric device based on bulk TE materials to be flexible, (i) flexible electrodes and (ii) holders to secure TE materials are required. In FTED, we have used liquid-metal encapsulated in polydimethylsiloxane (PDMS) as electrodes on one side above the bending neutral axis and flexible printed circuit boards (FPCB) as electrodes below the bending neutral axis. Hence, the stretchability of the liquid metal electrode and flatness of the FPCB are fully utilized to reduce thermal contact resistance. Additionally, we used PDMS and flexible wires as holders to eliminate filler materials that annihilate thermal bypass, i.e., heat transfer not going through TE materials. For refrigeration using portable batteries as power sources, the refrigerated skin temperature was lowered by 5.4 K which is adequate for humans to perceive coldness, according to theoretical analysis. For human body-heat harvesting, the open-circuit voltage and output power density were 7.38 mV and 8.32 μW/cm2 or 123.74 μW, respectively. This implies that the FTED can be used both as a portable refrigerator and a wearable body-heat harvester.
•We demonstrate the flexible thermoelectric device using liquid metal electrode.•We use the bulk inorganic thermoelectric materials for high performance.•In the case of human body cooling, the skin temperature drops by 5.4 K.•The output power density from body-heat harvesting is 8.32 μW/cm2.
This paper reports on the high power output of a watch strap-shaped body heat harvester and presents the detailed analysis of its performance. The device is made up of bulk thermoelectric materials ...and contains an integrated heat sink. When the device is worn on the wrist, it generates an output power of 6.97 μW/cm2 while the subject is walking. Theoretical analysis based on the human thermoregulatory model explains the high power output. Owing to the design of the body heat harvester, which can be adapted to conform to curved surfaces such as the skin and a screwed-down heat sink, an unprecedently low thermal contact resistance was achieved. Furthermore, the finned heat sink and high fill factor augmented the output power level. This research demonstrates the possibility of extracting body heat for operating wearable and/or implantable sensors made of bulk thermoelectric materials.
•Watch-strap-shaped flexible thermoelectric device is proposed.•Low thermal contact resistance is achieved by structural design and electrodes.•Fin-shaped heat sink enhances thermoelectric performance.•High output power density, 6.97 μW/cm2, is generated from the body-heat harvesting.
Biochar was generally used to reduce the macronutrient releases and to mitigate N2O gas emissions in cropland. This experiment evaluated the trend of major plant nutrient releases using the modified ...Hyperbola model and the greenhouse gas emissions by incorporating different poultry manure compost biochar with organic resources. The treatments consisted of the control as the organic fertilizer materials, the incorporated poultry manure compost biochar with organic fertilizer materials (PMCBF), and the incorporated plasma-activated poultry manure compost biochar with organic fertilizer materials (PAMBF) under redox conditions. The results showed that the cumulated highest concentrations of NH4–N and NO3–N were 2168.6 mg L−1 and 21.7 mg L−1 in the control, respectively. Compared with the control, the predicted reduction rates of NH4–N release from the PMCBF and PAMBF were 26.2% and 15.4%, respectively. In the control, the cumulated highest concentrations of PO4–P and K in leachate were 681.04 mg L−1 and 120.5 mg L−1, respectively. The predicted reduction rates of PO4–P and K were 55.1% and 15.5%, respectively, under the PAMBF compared to the control. The modified Hyperbola model with cumulated NH4–N, PO4–P, and K-releases under the treatments was a good fit (p < 0.0001). For greenhouse gas (GHG) emissions, the lowest cumulative N2O was 59.59 mg m−2 in the soil incorporated with PMCBF, and its reduction rate was 23.5% compared with the control. The findings of this study will contribute to more profound insights into the potential application of PAMBF and PMCBF as bio-fertilizers adapted to mitigate NH4–N, PO4–P, and K releases and N2O emissions, offering scientific evidence for organic farming strategies.
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•Plasma technology is adapted for the activated biochar.•The predicted PO4–P reduction rate was 55.1% in the PAMBF.•Mitigation rate of N2O emission in the PMCBF was 23.5%.
A 17.6-bit, 800-sample-per-second (SPS) read-out integrated circuit (IC) has been implemented for a bridge sensor. The read-out IC has a capacitively coupled instrumentation amplifier (CCIA) with a ...sensor offset voltage compensation circuit, an amplifier offset voltage compensation circuit, and an input impedance boosting loop (IBL). Followed by the CCIA, a programmable-gain third-order discrete-time incremental delta-sigma (<inline-formula> <tex-math notation="LaTeX">\Delta \Sigma) </tex-math></inline-formula> analog-to-digital converter (ADC) with an output data rate (ODR) of 12.8 kHz shortens the sensing time to reduce the static power consumption of the resistive bridge sensor and the read-out IC. To boost the input impedance of the CCIA, the system-level input and output choppers operate at a frequency of 12.8 kHz. The <inline-formula> <tex-math notation="LaTeX">\Delta \Sigma </tex-math></inline-formula> modulator converts the modulated signal to digital with a sampling clock of 4 MHz. The system-level chopping reduces the residual offset and the low-frequency noise with an on-chip cascade of integrators (CoIs) filter. Implemented in a 0.13-<inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> CMOS process, the read-out circuit achieves an input impedance of 22 <inline-formula> <tex-math notation="LaTeX">\text{M}\Omega </tex-math></inline-formula> at a data rate of 800 SPS, a sensor offset compensation range of ±350 mV, a maximum effective resolution of 17.6 bits, and an input-referred noise of <inline-formula> <tex-math notation="LaTeX">1.72 \mu \text{V}_{\text {RMS}} </tex-math></inline-formula> at a gain of 128. It draws an average current of <inline-formula> <tex-math notation="LaTeX">106.3 \mu \text{A} </tex-math></inline-formula> from a 3-V supply and <inline-formula> <tex-math notation="LaTeX">1.3 \mu \text{A} </tex-math></inline-formula> from a 1.5-V supply.
3D replication using PDMS mold for microcoil Lee, Dongkeon; Mekaru, Harutaka; Hiroshima, Hiroshi ...
Microelectronic engineering,
04/2009, Letnik:
86, Številka:
4
Journal Article, Conference Proceeding
Recenzirano
In this study, a novel fabrication method for fabricating complicated three-dimensional (3D) microcoil structures involving pre- and post-process was developed. As the pre-process, a 3D replication ...method using polydimethylsiloxane (PDMS) mold was developed for simple and low-cost fabrication of microstructures. The 3D PDMS mold was easily fabricated by using PDMS as the mold material. A master pattern with a microcoil structure was accurately transferred to a mold cavity shape. Within the cavity of the 3D PDMS mold, an ultraviolet (UV) curable resin structure was precisely replicated along the surface of a cylindrical Al wire deposited with Au–Ti. This replicated UV resin replica was utilized as the base component for the fabrication of a microcoil structure by electroplating. Finally, a microcoil structure with an outer diameter of 537.9
μm, line width of 12.3
μm, and coil thickness of 8.2
μm was fabricated by a post-process including electroplating.
Biochar was generally used to reduce the macronutrient releases and to mitigate N
O gas emissions in cropland. This experiment evaluated the trend of major plant nutrient releases using the modified ...Hyperbola model and the greenhouse gas emissions by incorporating different poultry manure compost biochar with organic resources. The treatments consisted of the control as the organic fertilizer materials, the incorporated poultry manure compost biochar with organic fertilizer materials (PMCBF), and the incorporated plasma-activated poultry manure compost biochar with organic fertilizer materials (PAMBF) under redox conditions. The results showed that the cumulated highest concentrations of NH
-N and NO
-N were 2,168.6 mg L
and 21.7 mg L
in the control, respectively. Compared with the control, the predicted reduction rates of NH
-N release from the PMCBF and PAMBF were 26.2% and 15.4%, respectively. In the control, the cumulated highest concentrations of PO
-P and K in leachate were 681.04 mg L
and 120.5 mg L
, respectively. The predicted reduction rates of PO
-P and K were 55.1% and 15.5%, respectively, under the PAMBF compared to the control. The modified Hyperbola model with cumulated NH
-N, PO
-P, and K-releases under the treatments was a good fit (p<0.0001). For greenhouse gas (GHG) emissions, the lowest cumulative N
O was 59.59 mg m
in the soil incorporated with PMCBF, and its reduction rate was 23.5% compared with the control. The findings of this study will contribute to more profound insights into the potential application of PAMBF and PMCBF as bio-fertilizers adapted to mitigate NH
-N, PO
-P, and K releases and N
O emissions, offering scientific evidence for organic farming strategies.
A 7.5 Gb/s/pin 8-Gb LPDDR5 SDRAM is implemented in a 1× nm DRAM process. Various techniques are applied to achieve higher bandwidth and lower power than LPDDR4X. To increase data rate, a WCK clocking ...scheme that is less vulnerable to power noise is adopted and a non-target ODT mode is proposed to reduce reflection noise in a two-rank system. A couple of techniques are proposed for saving power. To reduce self-refresh power, this chip supports deep sleep mode (DSM). In DSM, the leakage current of internal voltages decreases by disabling internal voltage generators that are not related with a self-refresh operation. Dynamic voltage frequency scaling (DVFS) is adopted to reduce read and write operation power and when writing all zeros data, an internal data copy function can be used for reducing write operation power. Last, a ZQ calibration scheme that shares one ZQ resistor (RZQ) and automatically executes ZQ calibration is presented. The proposed LPDDR5 DRAM operates up to 7.5 Gb/s on an automatic test equipment (ATE) and 6.4 Gb/s on a prototype system. Read and write power decrease by 21% and 33% compared to LPDDR4X at 4.266 Gb/s, and self-refresh power is reduced by 25% in DSM.
An 8.5-Gb/s/pin (Gb/s) 12-Gb LPDDR5 SDRAM is implemented in a second-generation 10-nm DRAM process with a hybrid-bank architecture that provides a power-optimized bank solution depending on the bank ...modes (4B/4BG, 16B-merged bank, 8B-split bank). Based on the specified bank modes, vertical and horizontal skew-cancel schemes for high density and an RBUS-based DBI ac to minimize data transition are newly proposed. Thus, the switching power of RBUS DBI ac is saved by 8.9% compared to that of DBI ac "OFF." To improve the rank interleaving efficiency with a current increase, partially enabled WCK (PE-WCK) mode is proposed, which minimizes the number of enabled circuits for maintaining the WCK2CK synchronization. Therefore, the current can be saved by 62% without a timing constraint compared to the WCK always-ON mode. To achieve high-speed operation beyond 6.4 Gb/s, speed-boosting techniques, namely, the two-step duty corrector, active resonant load (ARL), and one-tap decision feedback equalizer (DFE) with offset calibration, are newly adopted. In the coarse step in the two-step duty corrector, the value of the duty error decreases to below 5% by suppressing the dc signal. In the fine step, the remaining duty error is further reduced within 2.5 ps by the duty cycle monitor (DCM) and duty cycle adjustor (DCA). Moreover, the skew increase beyond 6.4 Gb/s due to the bandwidth limit by the heavy loading of four-phase WCK signals is alleviated by the ARL, where the four-phase skew is within 5 ps irrespective of process, voltage, and temperature (PVT) variations. The direct feedback DFE enables fast feedback (< 118 ps) for tap coefficient control, and offset calibration reduces the three-sigma offset of the four dynamic latches in DQ within 5 mV.
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