Fully Integrated Biochip Platforms for Advanced Healthcare

Recent advances in microelectronics and biosensors are enabling developments of innovative biochips for advanced healthcare by providing fully integrated platforms for continuous monitoring of a large set of human disease biomarkers. Continuous monitoring of several human metabolites can be addressed by using fully integrated and minimally invasive devices located in the sub-cutis, typically in the peritoneal region. This extends the techniques of continuous monitoring of glucose currently being pursued with diabetic patients. However, several issues have to be considered in order to succeed in developing fully integrated and minimally invasive implantable devices. These innovative devices require a high-degree of integration, minimal invasive surgery, long-term biocompatibility, security and privacy in data transmission, high reliability, high reproducibility, high specificity, low detection limit and high sensitivity. Recent advances in the field have already proposed possible solutions for several of these issues. The aim of the present paper is to present a broad spectrum of recent results and to propose future directions of development in order to obtain fully implantable systems for the continuous monitoring of the human metabolism in advanced healthcare applications

Review on carbon-derived, solid-state, micro and nano sensors for electrochemical sensing applications

The aim of this review is to summarize the most relevant contributions in the development of electrochemical sensors based on carbon materials in the recent years. There have been increasing numbers of reports on the first application of carbon derived materials for the preparation of an electrochemical sensor. These include carbon nanotubes, diamond like carbon films and diamond film-based sensors demonstrating that the particular structure of these carbon material and their unique properties make them a very attractive material for the design of electrochemical biosensors and gas sensors. Carbon nanotubes (CNT) have become one of the most extensively studied nanostructures because of their unique properties. CNT can enhance the electrochemical reactivity of important biomolecules and can promote the electron-transfer reactions of proteins (including those where the redox center is embedded deep within the glycoprotein shell). In addition to enhanced electrochemical reactivity, CNT-modified electrodes have been shown useful to be coated with biomolecules (e.g., nucleic acids) and to alleviate surface fouling effects (such as those involved in the NADH oxidation process). The remarkable sensitivity of CNT conductivity with the surface adsorbates permits the use of CNT as highly sensitive nanoscale sensors. These properties make CNT extremely attractive for a wide range of electrochemical sensors ranging from amperometric enzyme electrodes to DNA hybridization biosensors. Recently, a CNT sensor based fast diagnosis method using non-treated blood assay has been developed for specific detection of hepatitis B virus (HBV) (human liver diseases, such as chronic hepatitis, cirrhosis, and hepatocellular carcinoma caused by hepatitis B virus). The linear detection limits for HBV plasma is in the range 0.5–3.0 μL−1 and for anti- HBVs 0.035–0.242 mg/mL in a 0.1 M NH4H2PO4 electrolyte solution. These detection limits enables early detection of HBV infection in suspected serum samples. Therefore, non-treated blood serum can be directly applied for real-time sensitive detection in medical diagnosis as well as in direct in vivo monitoring. Synthetic diamond has been recognized as an extremely attractive material for both (bio-) chemical sensing and as an interface to biological systems. Synthetic diamond have outstanding electrochemical properties, superior chemical inertness and biocompatibility. Recent advances in the synthesis of highly conducting nanocrystalline-diamond thin films and nano wires have lead to an entirely new class of electrochemical biosensors and bio-inorganic interfaces. In addition, it also combines with development of new chemical approaches to covalently attach biomolecules on the diamond surface also contributed to the advancement of diamond-based biosensors. The feasibility of a capacitive field-effect EDIS (electrolyte-diamond-insulatorsemiconductor) platform for multi-parameter sensing is demonstrated with an O-terminated nanocrystalline-diamond (NCD) film as transducer material for the detection of pH and penicillin concentration. This has also been extended for the label-free electrical monitoring of adsorption and binding of charged macromolecules. One more recent study demonstrated a novel bio-sensing platform, which is introduced by combination of a) geometrically controlled DNA bonding using vertically aligned diamond nano-wires and b) the superior electrochemical sensing properties of diamond as transducer material. Diamond nanowires can be a new approach towards next generation electrochemical gene sensor platforms. This review highlights the advantages of these carbon materials to promote different electron transfer reactions specially those related to biomolecules. Different strategies have been applied for constructing carbon material-based electrochemical sensors, their analytical performance and future prospects are discussed

Coupling carbon nanotube mechanics to a superconducting circuit

The quantum behaviour of mechanical resonators is a new and emerging field driven by recent experiments reaching the quantum ground state. The high frequency, small mass, and large quality-factor of carbon nanotube resonators make them attractive for quantum nanomechanical applications. A common element in experiments achieving the resonator ground state is a second quantum system, such as coherent photons or superconducting device, coupled to the resonators motion. For nanotubes, however, this is a challenge due to their small size. Here, we couple a carbon nanoelectromechanical (NEMS) device to a superconducting circuit. Suspended carbon nanotubes act as both superconducting junctions and moving elements in a Superconducting Quantum Interference Device (SQUID). We observe a strong modulation of the flux through the SQUID from displacements of the nanotube. Incorporating this SQUID into superconducting resonators and qubits should enable the detection and manipulation of nanotube mechanical quantum states at the single-phonon level

Facile fabrication of stretchable Ag nanowire/polyurethane electrodes using high intensity pulsed light

Silver nanowires (AgNWs) have emerged as a promising nanomaterial for next generation stretchable electronics. However, until now, the fabrication of AgNW-based components has been hampered by complex and time-consuming steps. Here, we introduce a facile, fast, and one-step methodology for the fabrication of highly conductive and stretchable AgNW/polyurethane (PU) composite electrodes based on a high-intensity pulsed light (HIPL) technique. HIPL simultaneously improved wire-wire junction conductivity and wire-substrate adhesion at room temperature and in air within 50 mu s, omitting the complex transfer-curing-implanting process. Owing to the localized deformation of PU at interfaces with AgNWs, embedding of the nanowires was rapidly carried out without substantial substrate damage. The resulting electrode retained a low sheet resistance (high electrical conductivity) of <10 Omega/sq even under 100% strain, or after 1,000 continuous stretching-relaxation cycles, with a peak strain of 60%. The fabricated electrode has found immediate application as a sensor for motion detection. Furthermore, based on our electrode, a light emitting diode (LED) driven by integrated stretchable AgNW conductors has been fabricated. In conclusion, our present fabrication approach is fast, simple, scalable, and cost-efficient, making it a good candidate for a future roll-to-roll process

Fabrication of single walled carbon nanotube (SW-CNT) cantilevers for chemical sensing

With the discovery of carbon nanotubes (CNTs), many applications have been implemented based on their unique electronic, mechanical, chemical and optoelectronic properties. One area of applications is in gas sensors for detecting, oxygen, flammable and toxic gases. In our work, the focus is on the fabrication of carbon nanotube (CNT) cantilever sensors for integration with CMOS readout chip which offer increased sensitivity. The higher surface-to-bulk ratio enhances the property and performance of the gas sensor by nanocantilevers. In this work, we present the detection method based on the change in capacitance of the single walled carbon nanotube (SWCNT) cantilever. Carbon nanotubes are capable of interacting with the gaseous species either directly or indirectly by using a polymer analyte coated on its surface. The capacitance variation technique of measuring cantilever deflection was used to measure the bending rate. The capacitance between the cantilever and the fixed electrode varies as a function of the magnitude of the bending of the cantilever which is in turn proportional to the concentration of the gas species in the surrounding environment. To measure the variation in the capacitance value, the CNT cantilever beam is considered as one of the electrodes of the capacitor and the metal film as the other. The air between the plates acts as the dielectric material. Simulations including both ANSYS for nanocantilevers and SPICE for CMOS readout chip and experimental results are presented in this research. Integration and packaging issues are also discussed in our research

정전기수력학 인쇄를 활용한 단일벽 탄소나노튜브 기반 트랜지스터 및 응용

학위논문 (박사) -- 서울대학교 대학원 : 공과대학 전기·컴퓨터공학부, 2020. 8. 홍용택.As the demand and research for electronic devices on flexible and stretchable substrates gradually continues comparable to the conventional rigid silicon-based electronic devices, interest in new semiconducting materials capable of low-temperature processes and large-area processes is increasing. Single-walled carbon nanotube (SWCNT) is one of the representative materials satisfying the new interests thanks to its excellent electrical and mechanical properties. SWCNT can be advantageous for non-vacuum, low-temperature, and large-area processes in response to various solution processes such as dipping, inkjet printing, and gravure printing. For high-performance devices with low power consumption based on next-generation electronics, the demand for ultra-fine patterning technology based on the solution process is also increasing. In this thesis, SWCNT-based all electrohydrodynamic-jet (E-jet) printing system was established, a SWCNT-based thin-film transistor (SWCNT-TFT) with a channel length of 5 microns was implemented through the system. In addition, by developing and grafting technology to control the threshold voltage of SWCNT-TFTs based on the solution process, we have demonstrated highly integrated and high-resolution SWCNT-based applications including logic gate, pixel circuits for image detector and display. In addition to the micrometer scale fine pattern technology by the E-jet printing system, a new solution process-based vertical stacking technology is also introduced to further improve the transistor density, enabling high-resolution, highly integrated electronic applications in a continuous environment without any vacuum or high temperature process. The technology introduced in this thesis for high performance, high resolution, and high integration of SWCNT-based devices makes it possible to fabricate a 250 pixel per inch active matrix backplane utilizing only the solution process.유연 기판 및 신축성 기판상의 전자 소자에 대한 수요 및 연구가 종래의 단단한 실리콘 기반의 전자 기술만큼이나 많은 관심을 받고 있어, 이를 위한 저온 공정 및 대면적 공정이 가능한 새로운 반도체 물질 연구에 대한 관심이 증가하고 있다. 단일벽 탄소나노튜브는 뛰어난 전기적 및 기계적 특성 뿐만 아니라 비 진공, 저온, 그리고 대면적 공정이 가능한 담금 공정, 잉크젯 프린팅, 그리고 그라비아 인쇄법과 같은 용액공정에 대응하기에 이러한 요구를 충분히 충족시킨다. 마찬가지로 용액 공정 기반 소자의 고성능 및 저전력화를 위한 용액 공정기반의 초 미세 패터닝 기술에 대한 필요성도 증가하고 있다. 본 학위 논문에서는 단일벽 탄소나노튜브 기반의 전 정전기수력학 인쇄 시스템을 구축하여 5마이크론의 채널 길이를 갖는 단일벽 탄소나노튜브 기반 박막트랜지스터를 구현하였다. 또한 용액 공정기반의 단일벽 탄소나노튜브 기반 박막트랜지스터의 문턱 전압을 조절하는 기술을 개발하고 이를 접목시켜 논리소자와 영상센서 및 디스플레이를 위한 픽셀 회로를 포함한 단일벽 탄소나노튜브 기반의 고해상도, 고집적화된 응용소자를 개발하였다. 정전기수력학 인쇄 시스템을 통한 마이크론 수준의 미세 패터닝 기술 뿐만 아니라 집적도를 더욱 향상시키기 위한 용액 공정기반의 새로운 수직 적층형 기술을 도입하여 고해상도 및 고집적화된 단일벽 탄소나노튜브 기반의 전자 소자를 어떠한 진공 공정이나 고온공정 없이 연속된 환경에서 구현하였다. 본 학위논문에서 제시한 단일벽 탄소나노튜브 기반 소자의 고성능, 고해상도, 고집적화를 위한 기술은 250 ppi급의 능동형 매트릭스 백플레인의 제작을 순수 용액공정만으로 실현 가능하게 한다.1 Introduction 1 1.1 Single-Walled Carbon Nanotubes 1 1.2 Band structure of SWCNTs 8 1.2.1 Energy bandgap of SWCNTs 8 1.2.2 Density of states for SWCNTs 11 1.2.3 Detection for classifying species of SWCNTs 13 1.3 Sorting out semiconducting SWCNTs 16 1.3.1 Pre-deposition of the nanotubes and sorting later 16 1.3.2 First sorting out SWCNTs and deposition later 18 1.4 Operation of SWCNT-TFTs 21 1.4.1 SWCNT-TFTs as Schottky-barrier FETs 22 1.4.2 Random network of SWCNTs 26 1.5 Reported SWCNT-TFTs and applications 28 1.6 Technical points for microelectronics based on SWCNT-TFTs 32 1.7 Organization 34 2 Tunable threshold voltage in single-walled carbon nanotube thin-film transistors 35 2.1 Introduction 35 2.2 Experimental details 37 2.2.1 Fabrication process for solution-processed SWCNT-TFTs 37 2.2.2 Post-treatments for tunable threshold voltage in solution-processed SWCNT-TFTs and measurement of their electrical properties 38 2.3 Results and discussion 39 2.3.1 Post-chemical encapsulation for tunable threshold voltage 39 2.3.2 Contact resistance analysis by the Y-function method in SWCNT-TFTs employing chemical encapsulation 41 2.3.3 Shift of energy band in SWCNT-TFTs 42 2.3.4 Cycling tests for post-treatments 45 2.3.5 SWCNTs-based p-type only inverter 46 2.4 Conclusion 49 3 All electrohydrodynamic-jet printing system for single-walled carbon nanotube thin-film transistors 50 3.1 Introduction 50 3.2 Experimental details 55 3.2.1 Ink manufacturing for E-jet printed metal, dielectric, and active layers 55 3.2.2 Optimized E-jet printing conditions and fabrication process for all E-jet printed SWCNT-TFTs 57 3.3 Results and discussion 60 3.3.1 Constituting of all E-jet printing system 60 3.3.2 Optimized E-jet printed metal electrode 63 3.3.3 Optimized E-jet printed polymer dielectric 67 3.3.4 E-jet printing of S/D electrodes with short channel length 74 3.3.5 Formation of SWCNT networks in E-jet printing system 76 3.3.6 Overall process for all E-jet printing and electrical characteristics of all E-jet printed SWCNT-TFTs 78 3.4 Conclusion 83 4 All electrohydrodynamic-jet printing system based circuit design for high-resolution and highly integrated applications 85 4.1 Introduction 85 4.2 Experimental details 89 4.2.1 In-situ fabrication of via-hole and diode-connected SWCNTs-TFTs in all E-jet printing system 89 4.2.2 Fabrication process of all E-jet printed inverter with vertically stacked SWCNT-TFTs 90 4.2.3 Fabrication process of all E-jet printed active pixel sensor for image sensor with vertical stacking structure 92 4.2.4 Fabrication process of all E-jet printed pixel circuit for active matrix polymer light-emitting diode with vertical stacking structure 95 4.3 Results and discussion 98 4.3.1 In-situ via-hole formation technology based on all E-jet printing system 98 4.3.2 Additional E-jet printing of PVP layer on the SWCNT-TFTs 99 4.3.3 Electrical characteristics for all E-jet printed diode-connected SWCNT-TFTs 101 4.3.4 Electrical characteristics for all E-jet printed inverter with vertically stacked SWCNT-TFTs 103 4.3.5 Structure design for active pixel sensor based on vertically stacked E-jet printed SWCNT-TFTs 107 4.3.6 All E-jet printed pixel circuit for active matrix polymer light-emitting diode with vertical stacking structure 110 4.4 Conclusion 118 5 Conclusion 119 Appendix 121 A.1 Post-treatment with DI-water on SWCNT-TFT 121 A.2 Variation of characteristics of SWCNT-TFTs by post-treatment time with NH4OH 123 A.3 Surface energy variation by a ratio between cross-liking agent and PVP 124 A.4 Analysis for surface roughness parameters 125 A.5 Electrical characteristics of E-jet printed SWCNT-TFTs according to channel structure 128 Bibliography 130 Abstract in Korean 149Docto

Polypyrrole (PPy) Coated Patterned Vertical Carbon Nanotube (pvCNT) Dry ECG Electrode Integrated with a Novel Wireless Resistive Analog Passive (WRAP) ECG Sensor

Polypyrrole (PPy) Coated Patterned Vertical Carbon Nanotube (pvCNT) Dry ECG Electrode Integrated with a Novel Wireless Resistive Analog Passive (WRAP) ECG Senso