Research

  1. A CMOS wireless biomolecular sensing system-on-chip based on polysilicon nanowire technology (Link)
  2. As developments of modern societies, an on-field and personalized diagnosis has become important for disease preventions and proper treatments. To address this need, in this work, a polysilicon nanowire (poly-Si NW) based biosensor system-on-chip (bio-SSoC) is designed and fabricated by a 0.35μm 2-Poly-4-Metal(2P4M) complementary metal-oxide-semiconductor (CMOS) process provided by a commercialized semiconductor foundry. Because of advantages of CMOS system-on-chip (SoC) technologies, the poly-Si NW biosensor is integrated with a chopper differential-difference amplifier (DDA) based analog-front-end (AFE), a successive approximation analog-to-digital converter (SAR ADC), and a microcontroller to have better sensing capabilities than a traditional Si NW discrete measuring system. In addition, an on-off key (OOK) wireless transceiver is also integrated to form a wireless bio-SSoC technology. This is a pioneer work to harness momentum of CMOS integrated technology into emerging bio-diagnosis technologies. This integrated technology is experimentally examined to have a label-free and low-concentration biomolecular detection for both Hepatitis B Virus DNA (10fM) and cardiac troponin I protein (3.2 pM). Based on this work, the implemented wireless bio-SSoC has demonstrated a good biomolecular sensing characteristic and a potential for the low-cost and mobile applications. As a consequence, this developed technology can be one of promising candidates for on-field and personalized applications in biomedical diagnosis.
  3. A device design of an integrated CMOS poly-silicon biosensor-on-chip to enhance performance of biomolecular analytes in serum samples (Link)
  4. In this work, we develop an integrated 0.35μm complementary metal-oxide-semiconductor (CMOS) process biosensor system-on-chip (SoC) for elevating biomolecualr analytes detection perfomace in serum samples as an on-site point-of-care (POC) device. For clinical diagnosis on the basis of biomolecule-analysis, the detection performances of most POC biosensor devices seriously suffer from other non-analyte background protein interferences in patient serum samples. To conquer this obstacle, this work presents a fully integrated bottom-gate poly-silcion nanowire (polySi NW) biosensor SoC to enhance the detection performance of cardiac-specific troponin-I (cTnI) concentration levels in serum samples. By applying proper electrical potential at the bottom gate under polySi NW biosensor, the biosensor SoC response of the cTnI biomarker can be improved by at least 16 fold in 50% phantom serum samples with detection range. This enhancement can be attributed to the electrostatic interactions between target biomolecules and the applied bottom gate voltage. This is the first time a fully integrated polySi NW CMOS biosensor has shown feasibilities in clinical-diagnosis related biomarker detections in serum samples. Therefore, this developed technology paves the way toward on-field applications of CMOS compatible SiNW biosensing technologies and can be employed for future on-site serum biomolecular-analysis applications.
  5. An Enhancement of High-k/Oxide Stacked Dielectric Structure for Silicon-based Multi-nanowire Biosensor in Cardiac Troponin I Detection (Link)
  6. In this study, we demonstrate a series of multi-channel silicon nanowire (Si-NW) biosensors coated with different high-k dielectric materials for sensing property improvements. To enhance the compatibility to 3-Aminopropyltriethoxysilane (APTES) without any harsh surface treatment, a stacked structure of high-k dielectrics with ultrathin SiO2 is developed. Fluorescent experiments are employed to verify the enhancement. To experimentally examine the improvement of implemented devices, in addition, an acute myocradial infarction biomarker, cardiac troponin I (cTnI), with different concentrations is used. Based on the experimental results of ultrathin SiO2 sensing membrane structures stacked with 14 nm Al2O3 and 10 nm HfO2, compared with only high-k dielectric devices, the sensing property can be enhanced by 3.8 and 1.4 times, respectively. For the detection of lowest concentration, i.e. 320 fM, the signal enhancement is 20%. Based on this work, the proposed SiO2/high-k structure for Si-NW biosensor can be experimentally demonstrates a good potential for future applications in cTnI detections.
  1. A particle separation device based ontravelling-wave electroosmosis with a circular electrode array (Link)
  2. Particle separation is a crucial step in sample preparation processes. Especially, preparation for small-volume samples is important for clinical diagnosis and biochemical analysis. Due to the advantages of microfluidic techniques, microfluidic devices become potential candidates for particle separation. However the existing microfluidic devices require external pumping sources and extensive geometric patterns to attain high separation efficiency which is disadvantageous to handle with the paucity of sample. This paper presents a particle separation microfluidic device based on travelling-wave electroosmosis (TWEO) with circular electrode array to achieve self-pumping function and compact area for particle separation. The computational fluidic dynamic software is utilized to simulate two electrokinetic mechanisms: circular TWEO and dielectrophoresis (DEP). The circular TWEO shear flow generates a velocity gradient in radial direction which causes a shear stress-induced force to drag the particles into the center region. Moreover, the non linear gaps between electrodes cause the non-uniform electric field inducing the negative DEP forces pushing polystyrene beads towards to the peripheral region, and the magnitudes of negative DEP force are dependent on the levitation height determined by sizes of polystyrene beads. To prove the concept of particle separation mechanism, we utilized the various sized particles to demonstrate the motion behaviors in the developed device. The 15μm polystyrene beads are dragged into the center region due to the shear stress-induced force, and the 1μm polystyrene beads move towards to the outside region because of large negative DEP force. Furthermore, the two types of beads are employed simultaneously in the sample to further confirm the separation efficiency which demonstrates the purity of15μm and 1μm beads achieve 94.4% and 80.0% respectively. Consequently, the innovative device developed in this paper provides a promising solution for dealing with particle separation for sample volume of 50nL. Additionally, the circular TWEO device also promotes the feasibility of potable Lab-on-chip biosensor using in the point-of-care testing.
  1. Enhancement of Carrier Mobility in All-Inkjet-Printed Organic Thin-film Transistors Using a Blend of Poly(3-hexylthiophene) and Carbon Nanoparticles (Link)
  2. To enhance the carrier mobility of all-inkjet-printed organic thin film transistors, we fabricated devices that incorporated poly(3-hexylthiophene) (P3HT) and carbon nanoparticles (CNPs). The fabricated devices had an on/off ratio of 104, which is one order less than that of pristine organic thin-film transistors (OTFTs). The maximum carrier mobility as high as 0.053 cm2/V-s was achieved for a CNP/P3HT weight–weight ratio of 7/100. This degree of mobility is 10 times greater than average mobility of pristine P3HT-OTFTs. X-ray diffraction and scanning electron microscopy images reveal that the carrier mobility was enhanced by reducing the injection barrier and enhancing the carrier injection. This work demonstrates the feasibility of all-inkjet-printed OTFT technology.
  3. The Effect of Adjustable Threshold-Voltage in All-Inkjet-Printing Organic Thin Film Transistor by Double-Layer Dielectric Structures(Link)
  4. An all-inkjet-printed organic thin-film transistor (OTFT) with double-layer dielectric structure is proposed and implemented. Utilizing the double-layer structure with different dielectric materials, i.e., polyvinylphenol (PVP) with poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)), the threshold voltage of OTFT can be adjustable according to the compositions of printed materials. In other words, an enhancement-mode OTFT can be converted to a depletion-mode transistor by selectively printing additional copolymer dielectric onto original dielectric to form a high-k/low-k double layer structure. The printed OTFT has carrier mobility of 5.0 × 10-3 cm2/V-s. It also exhibits obviously threshold-voltage shift ranging from -13 V to 10 V. This work demonstrates an additional design parameter for organic electronics by inkjet printing technology.
  1. A Fully Integrated Humidity Sensor System-on-Chip by Micro-Stamping Technology (Link)
  2. A fully integrated humidity sensor chip was designed, implemented, and tested. Utilizing the micro-stamping technology, the pseudo-3D sensor system-on-chip (SSoC) architecture can be implemented by stacking sensing materials directly on the top of CMOS-fabricated chip. The fabricated sensor system-on-chip (2.28mm × 2.48mm) integrated a humidity sensor, an interface circuit, a digital controller, and an On-Off Keying (OOK) wireless transceiver. With low power consumption, i.e. 750mW without RF operation, the sensitivity of developed sensor chip was experimentally identified in the relative humidity (RH) ranging from 32% to 60%. The response time of the chip was also experimentally verified within 5 seconds from RH 36% to RH 64%. As a consequence, the implemented humidity SSoC paves the way toward the ultra-small sensor system for applications.
  3. A Printable Humidity Sensing Material Based on Conductive Polymer and Nanoparticles Composites (Link)
  4. To monitor humidity, the polymer-based humidity sensing material has become an emerging candidate because of its low-cost and low-power characteristics. To implement polymer sensing materials, however, the fabrication capability and stability are major concerns. In this work, an inkjet printable humidity sensing material, poly(3,4-ethylenedioxythiophene) : poly(styrene sulfonate) (PEDOT:PSS), is developed to improve the fabrication capability. Besides, different kinds of nanoparticles, SiO2 and aluminum zinc oxide (AZO), are also employed to enhance the stability and sensitivity to humidity sensing. Based on experimental results, the sensitivity can be improved by 100%; the stability can also be noticeably enhanced. To understand the sensing mechanism, X-ray diffraction (XRD), Fourier transforms infrared diffraction (FTIR), and photoluminescence spectrometer (PL) measurements are performed. Based on these material investigations, the sensing enhancement is due to physical adsorption of the blending nanoparticles. This work proposes a high sensitivity and low cost humidity sensing material for different applications.
  5. A Low-Power Integrated Humidity CMOS Sensor by Printing-on-Chip Technology (Link)
  6. A low-power, wide-dynamic-range integrated humidity sensing chip is implemented using a printable polymer sensing material with an on-chip pulse-width-modulation interface circuit. By using the inkjet printing technique, poly(3,4-ethylene-dioxythiophene)/polystyrene sulfonate that has humidity sensing features can be printed onto the top metal layer of a 0.35 μm CMOS IC. The developed printing-on-chip humidity sensor achieves a heterogeneous three dimensional sensor system-on-chip architecture. The humidity sensing of the implemented printing-on-chip sensor system is experimentally tested. The sensor shows a sensitivity of 0.98% to humidity in the atmosphere. The maximum dynamic range of the readout circuit is 9.8 MΩ, which can be further tuned by the frequency of input signal to fit the requirement of the resistance of printed sensor. The power consumption keeps only 154 μW. This printing-on-chip sensor provides a practical solution to fulfill an ultra-small integrated sensor for the applications in miniaturized sensing systems