Jui-Chang Kuo

A Passive Inertial Switch Using MWCNT–Hydrogel Composite With Wireless Interrogation Capability

This paper presents the development of a passive inertial switch using multiwall carbon nanotube (MWCNT)-hydrogel composite integrated with an inductor/capacitor (L -C) resonator. The device consists of a polydimethylsiloxane (PDMS) microfluidic chip containing MWCNT-hydrogel composite and water droplet and a glass substrate with a capacitor plate and an inductor coil. When the acceleration exceeds the designed threshold level, the water passes through the channel to the hydrogel cavity. The hydrogel swells and changes the capacitance of the integrated L-C resonator, which, in turn, changes the resonant frequency that can be remotely detected. Each sensor unit does not require onboard power and circuitry for operation, so the proposed device is disposable and is suitable for low-cost applications. All PDMS structures were fabricated using soft lithography. The L-C resonator was fabricated using a lift-off process to pattern metal layers on a glass substrate. The response time of the device is considerably reduced by introducing MWCNTs into the hydrogel composites. The dimensions of the device are 15 mm × 10 mm × 1.5 × mm. The characterization of the proposed device was also demonstrated. The threshold g-values, which differ for various applications, were strongly affected by the channel widths. The phase-dip measurement shows that the resonant frequencies shift from 164 to approximately 148 MHz when the device is activated by acceleration.

A hydrogel-based implantable wireless CMOS glucose sensor SoC

An implantable wireless glucose monitoring SoC with hydrogel-based glucose sensor is proposed in CMOS 0.35 um technology. Owing to the reusable nature of the hydrogel glucose sensor and the wireless readout ability of the circuitry, this SoC is suitable for long-term and continuous monitoring. In-Vitro test shows a resolution of 40 mMole in glucose detection. The total power consumption of the SoC is 285 nW in standby mode and 11.9 mW in data transmission mode.

Polymer-dispersed liquid crystal doped with carbon nanotubes for dimethyl methylphosphonate vapor-sensing application

This paper proposes a sensitive gas sensor composed of polymer-dispersed liquid crystal (PDLC) for dimethyl methylphosphonate (DMMP) detection. The sensing element comprises a PDLC sensing film doped with carbon nanotubes (CNT-PDLC) and a planar interdigital electrode pair. The concentration of DMMP exposed to the CNT-PDLC material is detectable by measuring the change in conductivity of the material. Compared to conventional LC-based sensors, the proposed PDLC device is robust against mechanical shocks, and can fully operate with a simple read-out circuit. The sensor response is linear for gas concentrations from 5 to 250 ppm, and the response time is approximately 125 s.

21.6 A smart CMOS assay SoC for rapid blood screening test of risk prediction

Rapid blood test is essential to disease control, risk assessment and point-of-care testing. Conventional enzyme-linked immunosorbent assay (ELISA) requires several hours or even days to get meaningful results. However, to some fierce contagious diseases, such as Ebola and SARS, the contagion can spread so fast that an instant and massive screening test is needed. A CMOS assay system-on-chip (SoC) offering a fast and cheap disease screening tool can be very helpful in the place where the medical resources are limited and the test is too costly to afford. Unlike the previously proposed CMOS biomolecular detection based on direct detection [1], a sandwiched assay detection protocol is adopted in this work, which possesses high sensitivity, high specificity and is free from pre-purified antigen process. As shown in Figure 1, a human blood sample containing the target biomolecules is applied on the proposed SoC. The test procedure includes blood filtration, biomolecular conjugation, electrolytic pumping, magnetic flushing and detection, automatically controlled by a micro-controller unit (MCU). The biomolecular signal is converted to the electrical signal by a CMOS-based Hall sensor array, as shown in the SEM image of Fig. 21.6.1, where the surface is coated with biomolecular probe. With the integration of the four LEDs and a battery, the detection steps can be indicated, providing an easy self-test point-of-care application.

A Smart CMOS Assay SoC for Rapid Blood Screening Test of Risk Prediction

A micro-controller unit (MCU) assisted immunoassay lab-on-a-chip is realized in 0.35 μm CMOS technology. The MCU automatically controls the detection procedure including blood filtration through a nonporous aluminum oxide membrane, bimolecular conjugation with antibodies attached to magnetic beads, electrolytic pumping, magnetic flushing and threshold detection based on Hall sensor array readout analysis. To verify the function of this chip, in-vitro Tumor necrosis factor- α (TNF- α) and N-terminal pro-brain natriuretic peptide (NT-proBNP) tests are performed by this 9 mm 2-sized single chip. The cost, efficiency and portability are considerably improved compared to the prior art.

A flexible tactile and shear sensing array fabricated by novel buckypaper patterning technique

In this work, we present a flexible tactile and shear sensing array utilizing patterned buckypaper as the sensing elements. A novel fabrication process for patterning buckypaper with high aspect ratio was proposed. The fabricated sensing device possesses the advantages such as anisotropic sensing capability, flexibility, simple fabrication, and low cost. The measured resistance vs. applied shear force on a single sensing element shows that the element exhibits different sensitivities along different directions. This anisotropic sensing capability can be employed for better shear sensing. The sensing elements also give good sensitivity and repeatability.

A capacitive immunosensor using on-chip electrolytic pumping and magnetic washing techniques for point-of-care applications

This work presents a capacitive immunosensor using on-chip electrolytic pumping and magnetic washing techniques. The proposed device possesses the advantages such as simple operation, low power consumption, and portability. The proposed device was fabricated using typical micromachining process, and is suitable for mass-production. We also demonstrated the detection of N-Terminal pro-brain-Type natriuretic peptide (NT-proBNP) using the fabricated device integrated with a CMOS capacitance sensing chip. The proposed device potentially can be used as a portable system for point-of-care applications.

A passive hydrogel-based inertial switch integrated with micromachined L-C resonator

This work presents the development of an inertial switch employing stimuli-sensitive hydrogel integrated with a passive inductor/capacitor (LC) resonator. The device consists of a glass substrate with capacitor plates and an inductor coil, and a PDMS microfluidic chip with micro-channels and micro-cavities containing hydrogel and water droplet. When the acceleration exceeds the designed threshold-level, the water passes through the channel to the hydrogel cavity. The hydrogel swells and changes the capacitance of the integrated LC resonator, which in turn changes the resonant frequency that can be remotely detected. All the PDMS structures were fabricated by using soft lithography. The L-C resonator was fabricated by lift-off process for patterning metal layers on a glass substrate. The size of the device is 15mm×10mm×1mm. The functionalities of proposed device were demonstrated. The measurement shows that the resonant frequencies shift from 72MHz to about 57MHz as the device is activated by acceleration.