This paper presents the first implementation of 100-nm-wide nanofluidics in a 65-nm CMOS chip using a one-step wet-etch to remove the copper routing from the back-end-of-line (BEOL) while maintaining transistor integrity through continuous monitoring of the IDS-VGS characteristics. Vertical fluidics are also successfully demonstrated by etching through 360 nm × 360 nm-sized vias. A non-destructive laser microscopy technique for imaging fluidic channels at a dimension below the visible-light wavelength is developed.
We present the integration of CMOS-embedded subtractive microfluidics with single-photon avalanche diode (SPAD) fluorescence lifetime sensors, enabling independent channel addressability for parallel readout. Microfluidic channels are realized by selectively wet-etching the back-end-of-line (BEOL) metal routing above the SPAD sensors, reducing the analyte-to-active-region spacing to 7 μm while allowing for precision alignment. Simultaneous readout from two SPADs underneath two separate fluidic channels is demonstrated, establishing a pathway toward a scalable, multiplexed lab-on-CMOS biosensing platform.
This research presents a digital microfluidic (DMF) array chip for real-time quantitative polymerase chain reaction (qPCR) assay. Combining cleanroom-based chip fabrication process with a facile, cleanroom-free rework method, the DMF chip exhibits high droplet-manipulating performance, flexible structural design, and low implementation cost. Meanwhile, consistent real-time PCR results can be acquired from repeatedly used DMF substrates, demonstrating the applicability of the rework strategy on PCR assay, and potential of widespread application of DMF technology on miniaturized and automated nucleic acid detection.
This work presents nanoporous silicon materials including n- and p-types formed by metal-assisted chemical etching (MACE) for thermoelectric generator (TEG) applications. The figure of merit (ZT) values for nanoporous silicon are 4.2 times better for n-type and 12.4 times greater for p-type than those of bulk silicon materials. Micro-TEGs fabricated from these materials achieved a peak power density and a normalized power output of 1.12 mu W/cm(2) and 0.078 mu W/cm(2)degrees C-2, respectively. Our achievements show a high possibility of nanoporous silicon as a leading candidate for future generation thermal energy harvesting, providing a sustainable and scalable substitute to conventional materials.
This paper presents a multi-element self-focusing piezoelectric micromachined ultrasound transducer (ms-fPMUT) for multi-frequency ultrasound stimulation across bio-tissues. This transducer is composed of six piezoelectric concentric rings with different thicknesses, and the design model of concentric rings is based on Fresnel diffraction theory. To achieve high performance piezoelectric functional layer elements, the mechanical polishing and transferring processes were proposed. Experimental results show that the fabricated ms-fPMUT can generate different focused sound fields at three frequencies of 5.5 MHz, 6 MHz and 8 MHz. This device can generate multi-frequency stimulation across the pork skin tissue, which is expected to enable noninvasive, precise and multi-position ultrasound therapy.
This work describes a novel fabrication procedure for single-unit paper/PDMS microfluidic platforms with controllable bonding strength reaching up to 970 kPa, enabling highly efficient applications in two-phase oil/water separation and gradient generation. All tested cases showed excellent performance: (1) A continuous two-phase flow of oil/water droplets was completely separated with 100% purity and an over 80% recovery rate; (2) By varying flow rates and changing paper patterns, different gradient profiles could be generated with full control of concentration levels and transition types.
We introduce a novel mesh-shaped electrochemical (EC) filter that enhances the reliability of electrochemical sensors, which are either based on catalytic reaction or redox cycling, by electrochemically removing interfering species in situ while minimally affecting the detection of target analytes. The geometries of micrometer-sized mesh-shaped filter electrodes, fabricated using wafer-scale MEMS processes, were optimized for efficient filtering through simulation and experiments. The EC filter-integrated electrochemical sensors successfully demonstrated the detection of glucose and dopamine with high reliability, even in the presence of interfering species at varying concentrations.
This paper reports an experimental study and decoupled analysis of support transducer topology-based thin-film piezoelectric on substrate (TPoS) architecture to examine the energy confinement characteristics at resonance. We recorded a high-Quality factor (Q) of 60,688 at 65 MHz at 300K for the coupled resonator topology with Aluminum Nitride (AlN) as piezoelectric material. This coupled resonator scheme exhibits a similar to 60 times Q enhancement compared to the standalone resonator since a higher percentage of energy is stored in the higher order mode high-Q resonant tank. The coupled resonator topology exhibits a Q of 83,548 in the damping characteristics study done at cryogenic temperature.
In this manuscript, we proposed a multifunctional hydrogel characterized by stable power generation, multimodal self-powered sensing, high durability, and resilience across various environments, along with scalability and biocompatibility for widespread application in outdoor smart farming It can continuously generate direct current (DC) output with a power density of 1.9 W m(-3), maintaining such output for 56,25 days of continuous operation in normal outdoor environments with an energy density of 1.36 x 10(7)J m(-3). At the same time, it can recover in extreme scorching and arid outdoor environments for 13 cycles in 36,67 days. Furthermore, it can also serve as a long-term self-powered sensor to evaluate plants' health status, giving important information to agriculture decision-makers. Self-sustainable battery-less outdoor monitoring systems can be built solely with this hydrogel, which simultaneously possesses scalable and low-cost production for large-scale applications. This work provides new potential for the future of smart agriculture and sustainable green earth.
In this study, we present a novel technique for expanding the bandwidth of surface acoustic wave (SAW) delay lines by leveraging the multi-mode behavior of thin-film acoustic waveguides. Through numerical analysis, we show that a wide and sharp "multi-mode passband" can be achieved by merging the responses of adjacent acoustic modes in an acoustic delay line (ADL) via a carefully optimized thickness-to-wavelength ratio of the waveguide. To validate this concept, we designed the ADL on a silicon-based thin-film lithium niobate-on-insulator platform (LN/SiO2/Si) equipped with single-phase unidirectional transducers (SPUDTs). Three waveguide surface topographies are experimentally analyzed to optimize the passband. With a wavelength (lambda) of 1 mu m, the proposed multi-mode passband ADL achieves a minimum insertion loss (IL) of 8.58 dB, a wide 3-dB fractional bandwidth (FBW) of 9.55%, and a large group delay (GD) of 35 ns at 4.3 GHz. The competitive performance of the proposed design, compared to state-of-the-art ADLs, underscores the significant potential of the multi-mode design concept for wideband radio frequency (RF) signal processing.
Piezoelectric micromachined ultrasonic transducers (pMUTs) could enable unique applications in medical imaging, healthcare, human-machine interfaces, and point-of-care testing. This work presents the first time pMUTs are implemented for biological age assessment via growth plate detections. Traditionally, the biological age can be examined by sophisticated equipment in a lab such as by DNA methylation and telomere attrition [1]. We propose a novel method with three key advancements: (1) a wearable ultrasound device for biological age detection by a compact pMUTs chip; (2) a beamforming scheme with a viewing window of 60 degrees and resolution of 0.14 degrees; and (3) growth plate measurement on the ulna and radius within the wrist with a thicknesses of 2 mm. As such, this work opens the potential to detect diseases such as endocrine disorders by a wearable pMUTs device.
This study extends the approach in [1] by applying the Halbach array concept to arrange and integrate 5 sensing units (including 1 center unit and 4 corner units), each unit consisting of planar and vertical inductive coils (Fig. 1a), on a CMOS chip to implement a three-axis inductive tactile sensor (Fig. 1b). The coil design with the arrangement of Halbach array could converge the magnetic flux between units up to the top surface of the device to enhance the performance of the inductive tactile sensor. By leveraging the multiple metal layers of the TSMC 0.18 mu m 1P6M standard CMOS process platform in this study, the vertical and the planar coils are fabricated and integrated to realize the proposed design. Measurements reveal that the sensitivity of the force sensor with proposed three-dimensional coils has been improved by 2-fold for normal load and 2.4-fold for shear load.
This paper presents a novel low-cost capacitive nanogap microsensor for detection of hydrogen gas with a sub-50 ppm minimum detectable signal (MDS) and sub-second response time. The sensor operation relies on the closing of a nanogap present between two Pd cantilever beams structures of linear and U geometries when the beams are exposed to very low levels of H-2. The sensor achieves a high sensitivity using amplified chemically actuated nanogap closing caused by the dissimilar expansion of the two cantilever structures of different lengths, one much longer than the other. The larger the length difference, the higher is the amplification. The sensor display a low temperature dependence (similar to 7 ppb/C degrees). The chemically actuated design significantly advances hydrogen-sensing technology by combining high sensitivity with low cost; thus, this sensor is suitable for large-scale environmental monitoring applications.
We present a novel modification for an ultra-flexible neural probe capable of simultaneous electrophysiological recording and dopamine detection within cerebral tissue. Following electrode modification, the electrochemical stability of the electrode coating was enhanced, and its specific surface area was increased, thereby significantly improving its sensitivity to dopamine. Building upon this foundation, the ultra-flexible design minimizes damage to brain tissue, enabling stable simultaneous detection of electrophysiological and electrochemical signals for over six weeks. The high-density electrode array design facilitates concurrent monitoring of activities across multiple brain regions. This novel approach provides new methodologies for neuroscience research and the treatment of brain disorders.
MEMS micromirrors are fragile and require careful handling to work in harsh environments and survive accidental falls or external impacts, which is especially critical for micromirror arrays, where multiple units must work jointly. This paper presents a robust 4 x 4 electrothermal micromirror array, constructed with bimorph beams made of Al and photosensitive polyimide (PSPI). The low Young's modulus of PSPI combined with the high ductility of Al enables this micromirror array to withstand impacts exceeding 1600 g. Additionally, this micromirror array demonstrates exceptional tip-tilt-piston scanning capabilities, positioning it as a promising candidate for applications in optical phased array modulation and optical cross-connect.
This paper reports a novel MEMS-bascd pressure sensor array. inspired by traditional Chinese medicine, for detecting and identifying pulse signals. A multidimensional pulse acquisition array was developed by emulating traditional Chinese pulse diagnosis techniques to capture pulse signals at the cun, guan, and chi positions along the radial artely. A database was created with pulse signals recorded under normal breathing and breathholding conditions. These features were used to train a support vector machine (SVM) classification model. The experimental results show that the model achieved high accuracy (99.33%) and sensitivity (98%) in detecting sleep apnea. Overall. this system could offer innovative technical support and promising applications for modernizing traditional Chinese diagnostic methods and developing smart healthcare devices.
This paper presents a new class of miniaturized, uncooled, and ultra-fast infrared (IR) sensors based on 30%-doped Aluminum Scandium Nitride (AlScN) nanoplate resonant thermal detectors (NPRTDs) that will leverage high electromechanical coupling, plasmonic enhancement, and optomechanical readout to potentially improve the state-of-the-art IR sensing capabilities. The combination of small footprint, high selectivity, high responsivity, low noise, and fast detection speed at the pixel level aims to enable innovative thermal imagers through multi-pixel integration. These preliminary results demonstrate that a Noise Equivalent Power (NEP) of around 1 pW/Hz(1/2) and a thermal time constant (tau) of around 470 mu s are achievable. This work represents the first experimental demonstration of plasmonic absorbers that utilize AlScN as dielectric layer, which enables a further improvement in both the thermal resistance and the Temperature Coefficient of Frequency (TCF).
This work systematically designs and optimizes the pMUT device aiming for extending the distance of mobile ranging application. This is achieved by maximizing the achievable output pressure and receiver sensitivity, while minimizing the propagation loss as well as enhancing the received signal strength through better matching of transmit and receive mode resonant frequencies via DC tuning. The pMUT device, fabricated via a 200 mm Sc0.3Al0.7N MEMS platform, achieves an ultra-high peak output pressure of 80 Pa at 10 cm and a time-of-flight range of up to 20 m at around 50 kHz.
This work presents a facile method for identifying the crystal orientations of carbon nanotubes (CNTs) using the directional alignment between epitaxially grown AuCN nanowires and the underlying CNT. We analyzed and determined the chiral indices of multiple CNTs in a local area by measuring the nanowire’s angles. In our experimental study, we confirmed that these nanowires can indicate the crystal orientations of single-wall carbon nanotubes (SWCNTs) with acceptable accuracy and can be easily removed via a simple wet-etching process.
This study extends the concepts in previous works to present an inductive-force/capacitive-proximity tactile sensor consisting of four-layer stacked interdigitated spiral-coils chip with vertically integrated stainless steel/Cr steel bumps using flip-chip bonding technology. The chip is implemented using the TSMC 0.18 mu m 1P6M standard CMOS process. Key features of this work include: (1) Flip-chip bonding for vertical integration of interdigitated spiral-coils chip with stainless steel and Cr steel bumps; (2) Stainless steel bump for magnetic flux concentration to enhance the inductive force sensing; (3) Stainless steel bump for lowering parasitic capacitance to improve the capacitive proximity sensing. The integrated stainless steel with 2-turn coils enhances force sensing signal to 300.5 nH/N under a 1 N loading (about 47% improvement) and demonstrates the feasibility of stabilizing the capacitive proximity sensing signal.
