A New Localization System for Indoor Service Robots in Low Luminance and Slippery Indoor Environment Using Afocal Optical Flow Sensor Based Sensor Fusion.

In this paper, a new localization system utilizing afocal optical flow sensor (AOFS) based sensor fusion for indoor service robots in low luminance and slippery environment is proposed, where conventional localization systems do not perform well. To accurately estimate the moving distance of a robot in a slippery environment, the robot was equipped with an AOFS along with two conventional wheel encoders. To estimate the orientation of the robot, we adopted a forward-viewing mono-camera and a gyroscope. In a very low luminance environment, it is hard to conduct conventional feature extraction and matching for localization. Instead, the interior space structure from an image and robot orientation was assessed. To enhance the appearance of image boundary, rolling guidance filter was applied after the histogram equalization. The proposed system was developed to be operable on a low-cost processor and implemented on a consumer robot. Experiments were conducted in low illumination condition of 0.1 lx and carpeted environment. The robot moved for 20 times in a 1.5 × 2.0 m square trajectory. When only wheel encoders and a gyroscope were used for robot localization, the maximum position error was 10.3 m and the maximum orientation error was 15.4°. Using the proposed system, the maximum position error and orientation error were found as 0.8 m and within 1.0°, respectively.

A Disposable and Multi-Chamber Film-Based PCR Chip for Detection of Foodborne Pathogen.

Since the increment of the threat to public health caused by foodborne pathogens, researches have been widely studied on developing the miniaturized detection system for the on-site pathogen detection. In the study, we focused on the development of portable, robust, and disposable film-based polymerase chain reaction (PCR) chip containing a multiplex chamber for simultaneous gene amplification. In order to simply fabricate and operate a film-based PCR chip, different kinds of PCR chambers were designed and fabricated using polyethylene terephthalate (PET) and polyvinyl chloride (PVC) adhesive film, in comparison with commercial PCR, which employs a stereotyped system at a bench-top scale. No reagent leakage was confirmed during the PCR thermal cycling using the film PCR chip, which indicates that the film PCR chip is structurally stable for rapid heat cycling for DNA amplification. Owing to use of the thin film to fabricate the PCR chip, we are able to realize fast thermal transfer from the heat block that leads to short PCR amplification time. Moreover, using the film PCR chip, we could even amplify the target pathogen with 10 CFU mL-1. The artificially infected milk with various concentration of Bacillus cereus was successfully amplified on a single film PCR chip. On the basis of the reliable results, the developed film PCR chip could be a useful tool as a POCT device to detect foodborne pathogens via genetic analysis.

Nanopillar films with polyoxometalate-doped polyaniline for electrochemical detection of hydrogen peroxide.

Design and fabrication of electrodes is key in the development of electrochemical sensors with superior electrochemical performances. Herein, an enzymeless electrochemical sensor is developed for detection of hydrogen peroxide based on the use of highly ordered polyoxometalate (POM)-doped polyaniline (PANI) nanopillar films. The electrodeposition technique enables the entrapment of POMs into PANI during electropolymerization to produce thin coatings of POM-PANI. Electrochemical investigations of the POM-PANI/nanopillar electrode showed well-defined multiple pairs of redox peaks and rapid electron transfer. The nanopillar structure facilitated the diffusion of the electrolyte and thus, enhanced the redox reaction. In particular, the POM-PANI/nanopillar electrode was incorporated into a flow injection biosensor and it demonstrates its electrocatalytic activity to detect hydrogen peroxide with high sensitivity, rapid response time, and low detection limit.

A Monocular Vision Sensor-Based Obstacle Detection Algorithm for Autonomous Robots.

This paper presents a monocular vision sensor-based obstacle detection algorithm for autonomous robots. Each individual image pixel at the bottom region of interest is labeled as belonging either to an obstacle or the floor. While conventional methods depend on point tracking for geometric cues for obstacle detection, the proposed algorithm uses the inverse perspective mapping (IPM) method. This method is much more advantageous when the camera is not high off the floor, which makes point tracking near the floor difficult. Markov random field-based obstacle segmentation is then performed using the IPM results and a floor appearance model. Next, the shortest distance between the robot and the obstacle is calculated. The algorithm is tested by applying it to 70 datasets, 20 of which include nonobstacle images where considerable changes in floor appearance occur. The obstacle segmentation accuracies and the distance estimation error are quantitatively analyzed. For obstacle datasets, the segmentation precision and the average distance estimation error of the proposed method are 81.4% and 1.6 cm, respectively, whereas those for a conventional method are 57.5% and 9.9 cm, respectively. For nonobstacle datasets, the proposed method gives 0.0% false positive rates, while the conventional method gives 17.6%.

A Highly Sensitive and Reliable Strain Sensor Using a Hierarchical 3D and Ordered Network of Carbon Nanotubes.

A 3D network of single-walled carbon nanotubes embedded in poly-(dimethylsiloxane) is presented as a promising route to the fabrication of a flexible film with ordered and interconnected single-walled carbon nanotubes. This is possible using a simple transfer method of as-grown hierarchical single-walled carbon nanotubes on a Si pillar substrate. This film is used as a highly sensitive strain gauge sensor. This type of network embedded in a polymer film should be applicable to many fields involving mechanically stable and reliable strain sensors.

Afocal optical flow sensor for reducing vertical height sensitivity in indoor robot localization and navigation.

This paper introduces a novel afocal optical flow sensor (OFS) system for odometry estimation in indoor robotic navigation. The OFS used in computer optical mouse has been adopted for mobile robots because it is not affected by wheel slippage. Vertical height variance is thought to be a dominant factor in systematic error when estimating moving distances in mobile robots driving on uneven surfaces. We propose an approach to mitigate this error by using an afocal (infinite effective focal length) system. We conducted experiments in a linear guide on carpet and three other materials with varying sensor heights from 30 to 50 mm and a moving distance of 80 cm. The same experiments were repeated 10 times. For the proposed afocal OFS module, a 1 mm change in sensor height induces a 0.1% systematic error; for comparison, the error for a conventional fixed-focal-length OFS module is 14.7%. Finally, the proposed afocal OFS module was installed on a mobile robot and tested 10 times on a carpet for distances of 1 m. The average distance estimation error and standard deviation are 0.02% and 17.6%, respectively, whereas those for a conventional OFS module are 4.09% and 25.7%, respectively.

A universal spring-probe system for reliable probing of electrochemical lab-on-a-chip devices.

For achieve sensitivity in lab-on-a-chip electrochemical detection, more reliable probing methods are required, especially for repeated measurements. Spring-probes are a promising candidate method which can replace needle-like probes and alligator clips that usually produce scratches on the surface of gold electrodes due to the strong physical contacts needed for electrochemical measurements. The superior reliability of amperometric measurements by a spring-probe system was compared with results by conventional probing methods. We demonstrated that a universal spring-probe system would be potentially suitable to achieve high performance in lab-on-a-chip devices using electrochemical detection.

Developing centrifugal force real-time digital PCR for detecting extremely low DNA concentration.

Digital PCR (dPCR) is a technique for absolute quantification of nucleic acid molecules. To develop a dPCR technique that enables more accurate nucleic acid detection and quantification, we established a novel dPCR apparatus known as centrifugal force real-time dPCR (crdPCR). This system is efficient than other systems with only 2.14% liquid loss by dispensing samples using centrifugal force. Moreover, we applied a technique for analyzing the real-time graph of the each micro-wells and distinguishing true/false positives using artificial intelligence to mitigate the rain, a persistent issue with dPCR. The limits of detection and quantification were 1.38 and 4.19 copies/µL, respectively, showing a two-fold higher sensitivity than that of other comparable devices. With the integration of this new technology, crdPCR will significantly contribute to research on next-generation PCR targeting absolute micro-analysis.

Development of a plastic-based microfluidic immunosensor chip for detection of H1N1 influenza.

Lab-on-a-chip can provide convenient and accurate diagnosis tools. In this paper, a plastic-based microfluidic immunosensor chip for the diagnosis of swine flu (H1N1) was developed by immobilizing hemagglutinin antigen on a gold surface using a genetically engineered polypeptide. A fluorescent dye-labeled antibody (Ab) was used for quantifying the concentration of Ab in the immunosensor chip using a fluorescent technique. For increasing the detection efficiency and reducing the errors, three chambers and three microchannels were designed in one microfluidic chip. This protocol could be applied to the diagnosis of other infectious diseases in a microfluidic device.

Modification of silicon substrate using low-energy proton beam for selective growth of CNTs.

A 3 keV low-energy proton beam was used to irradiate a silicon substrate for selective modification. The water contact angle measurement, chemical etching test with HF and the auger electron spectroscopy were used to investigate the chemical properties and the material composition of the proton beam-irradiated silicon substrate. The proton beam-irradiated silicon substrate was covered with a silicon oxide layer of about 60-70 angstroms due to the incorporation of oxygen molecules after exposure to ambient air. The silicon oxide layer produced by the proton beam was highly resistant to HF treatment which typically used to remove the silicon oxide on a substrate, and the surface of it was more hydrophilic than the native silicon oxide removed silicon surface with Si-H surface group. For the selective growth of carbon nanotubes (CNTs), the silicon oxide pattern was easily fabricated via proton beam irradiation when the silicon substrate was covered with a shadow mask. The Fe-Mo bimetallic catalysts for the growth of CNTs were adsorbed onto the silicon oxide layer, which is more hydrophilic than the silicon surface. The CNTs were grown on the patterned substrate using a chemical vapor deposition method, and it was confirmed by scanning electron microscopy.

All-in-One DNA Extraction Tube for Facilitated Real-Time Detection of Infectious Pathogens.

An "all-in-one tube" platform is developed, where the genetic analysis involving DNA extraction, amplification, and detection can be performed in a single tube. The all-in-one tube consists of a polymerase chain reaction (PCR) tube in which the inner surface is conformally modified with a tertiary-amine-containing polymer to generate a strong electrostatic interaction with DNA. The all-in-one tube provides high DNA capture efficiency exceeding 80% from Escherichia coli O157: H7 pathogen at a wide range of DNA amount from 0.003 to 3 ng. Indeed, the use of the surface-functionalized PCR tube enables direct amplification and detection of the surface-captured DNA without the modification of standard real-time PCR instrument. Besides, this platform has sensitivity, selectivity, and reliability enough for accurate detection at the minimal infective dose of both gram-positive and negative pathogens. The all-in-one tube enables the direct molecular diagnosis, substantially reducing the labor-intensive pathogen detection steps while providing high compatibility with the currently established real-time PCR instruments, and illustrates its on-site applicability with convenience expandable to various genetic analyses including food safety testing, forensic analysis, and clinical diagnosis.

3D Hierarchical Polyaniline-Metal Hybrid Nanopillars: Morphological Control and Its Antibacterial Application.

Effective and reliable antibacterial surfaces are in high demand in modern society. Although recent works have shown excellent antibacterial performance by combining unique hierarchical nanotopological structures with functional polymer coating, determining the antibacterial performance arising from morphological changes is necessary. In this work, three-dimensional (3D) hierarchical polyaniline-gold (PANI/Au) hybrid nanopillars were successfully fabricated via chemical polymerization (i.e., dilute method). The morphology and structures of the PANI/Au nanopillars were controlled by the reaction time (10 min to 60 h) and the molar concentrations of the monomer (0.01, 0.1, and 1 M aniline), oxidant (0.002, 0.0067, 0.01, and 0.02 M ammonium persulfate), and acid (0.01, 0.1, 1, and 2 M perchloric acid). These complex combinations allow controlling the hierarchical micro- to nanostructure of PANI on a nanopillar array (NPA). Furthermore, the surface of the 3D PANI/Au hierarchical nanostructure can be chemically treated while maintaining the structure using initiated chemical vapor deposition. Moreover, the excellent antibacterial performance of the 3D PANI/Au hierarchical nanostructure (HNS) exceeds 99% after functional polymer coating. The excellent antibacterial performance of the obtained 3D PANI/Au HNS is mainly because of the complex topological and physicochemical surface modification. Thus, these 3D PANI/Au hierarchical nanostructures are promising high-performance antibacterial materials.

Flexible and highly ordered nanopillar electrochemical sensor for sensitive insulin evaluation.

In line with growing interest in obesity management, there has been an increase in the amount of research focused on highly sensitive analysis systems for a small number of biomarers. In this paper, we introduce the highly ordered nanopillar electrode, featuring a high aspect ratio surface area that enables enhanced electron transfer. For fabrication of the flexible electrode, gold was evaporated by electronic beam lithography on polyurethane (PU), which has high flexibility. The fabricated nanopillar is 500 nm in diameter and 1500 nm in height. Based on the highly ordered nanostructure electrode, insulin was selected as a biomarker to monitor the insulin resistance associated with obesity. To effectively analyze the insulin, the self-assembled monolayer chemical was used to introduce the enzyme catalysis-based electrochemical immunoassay, leading to the analysis of the insulin concentration range from 0.1 to 1.0 ng/mL in the real sample. The square wave voltammetry principle was used to measure HRP-based electrochemical signal both electrochemically and quantitatively. Based on the nanostructural properties of significant electrochemical behavior, we successfully analyzed insulin in the plasma sample with high sensitivity (LOD of 0.1 ng/mL) and with high reproducibility (<10%). The obtained sensitivity of nanopillar electrode is approximately 10 times (1020%) greater than that of commercial electrode. The results demonstrated that the nanopillar electrode is suitable for precise and sensitive analysis of low-level biomolecules in medical and commercial fields.

Extremely Fast Self-Healable Bio-Based Supramolecular Polymer for Wearable Real-Time Sweat-Monitoring Sensor.

Sensors with autonomous self-healing properties offer enhanced durability, reliability, and stability. Although numerous self-healing polymers have been attempted, achieving sensors with fast and reversible recovery under ambient conditions with high mechanical toughness remains challenging. Here, a highly sensitive wearable sensor made of a robust bio-based supramolecular polymer that is capable of self-healing via hydrogen bonding is presented. The integration of carbon fiber thread into a self-healing polymer matrix provides a new toolset that can easily be knitted into textile items to fabricate wearable sensors that show impressive self-healing efficiency (>97.0%) after 30 s at room temperature for K+/Na+ sensing. The wearable sweat-sensor system-coupled with a wireless electronic circuit board capable of transferring data to a smart phone-successfully monitors electrolyte ions in human perspiration noninvasively in real time, even in the healed state during indoor exercise. Our smart sensors represent an important advance toward futuristic personalized healthcare applications.

Portable vibration-assisted filtration device for on-site isolation of blood cells or pathogenic bacteria from whole human blood.

Isolation of specific cells from whole blood is important to monitor disease prognosis and diagnosis. In this study, a vibration-assisted filtration (VF) device has been developed for isolation and recovery of specific cells such as leukocytes and pathogenic bacteria from human whole blood. The VF device is composed of three layers which was fabricated using injection molding with cyclic olefin copolymer (COC) pellets consisting of: a top layer with coin-type vibration motor (Ф = 10mm), a middle plate with a 1µm or 3µm-pore filter membrane to separate of Staphylococcus aureus (S. aureus) cells or leukocytes (i.e. white blood cells) respectively, and a bottom chamber with conical-shaped microstructure. One milliliter of human whole blood was injected into a sample loading chamber using a 3µm-pore filter equipped in the VF device and the coin-type vibration motor applied external vibration force by generating a rotational fluid which enhances the filtration velocity due to the prevention of the cell clogging on the filter membrane. The effluent blood such as erythrocytes, platelet, and plasma was collected at the bottom chamber while the leukocytes were sieved by the filter membrane. The vibration-assisted leukocyte separation was able to finish within 200s while leukocyte separation took 1200s without vibration. Moreover, we successfully separated S. aureus from human whole blood using a 1µm-pore filter equipped VF device and it was further confirmed by genetic analysis. The proposed VF device provides an advanced cell separation platform in terms of simplicity, fast separation, and portability in the fields of point-of-care diagnostics.

A film-based integrated chip for gene amplification and electrochemical detection of pathogens causing foodborne illnesses.

Given the increased interest in public hygiene due to outbreaks of food poisoning, increased emphasis has been placed on developing novel monitoring systems for point-of-care testing (POCT) to evaluate pathogens causing foodborne illnesses. Here, we demonstrate a pathogen evaluation system utilizing simple film-based microfluidics, featuring simultaneous gene amplification, solution mixing, and electrochemical detection. To minimize and integrate the various functionalities into a single chip, patterned polyimide and polyester films were mainly used on a polycarbonate housing chip, allowing simple fabrication and alignment, in contrast to conventional polymerase chain reaction, which requires a complex biosensing system at a bench-top scale. The individual integrated sensing chip could be manually fabricated in 10 min. Using the developed film-based integrated biosensing chip, the genes from the pathogens causing foodborne illnesses were simultaneously amplified based on multiple designed microfluidic chambers and Hoechst 33258, which intercalates into double-stranded DNA, to generate the electrochemical signal. The target pathogen gene was accurately analyzed by square wave voltammetry (SWV) within the 25 s, while the gel electrophoresis required about 30 min. Based on the developed integrated biosensing chip, the 1.0 × 101 and 1.0 × 102 colony-forming unit (CFU) of Staphylococcus aureus and Escherichia coli were sensitively detected with high reproducibility in the 25 s. On the basis of the significant features of the film-based molecular analysis platform, we expect that the developed sensor could be applied to the screening of various pathogens as a POCT device.

High performance electrochemical glucose sensor based on three-dimensional MoS2/graphene aerogel.

Two-dimensional (2D) nanosheets have been extensively explored as electrode materials for the development of high-performance electrochemical biosensors due to their unique structural characteristics. Nevertheless, 2D nanosheets suffer from sheet aggregation issues limiting the electrical conductivity of layered metal sulfides or hydroxides. Here, we report high-performance glucose biosensors based on a three-dimensional (3D) aerogel composed of interconnected 2D MoS2 and graphene sheet. 3D MoS2/graphene aerogel (MGA) provides a large surface area for the effective immobilization of enzymes, and continuous framework of electrically conductive graphene sheets. Flow-injection amperometric evaluation of the glucose biosensor using a 3D MGA electrode exhibits a rapid response (∼4s), a linear detection range from 2 to 20mM, a sensitivity of 3.36µA/mM, and a low limit of detection of 0.29mM. Moreover, the interference response from oxidizable species, such as ascorbic acid, uric acid and dopamine is negligible at an operating potential of -0.45V.

Fabrication of newspaper-based potentiometric platforms for flexible and disposable ion sensors.

Paper-based materials have attracted a great deal of attention in sensor applications because they are readily available, biodegradable, inexpensive, and mechanically flexible. Although paper-based sensors have been developed, but important obstacles remian, which include the retention of chemical and mechanical stabilities when paper is wetted. Herein, we develop a simple and scalable process for fabrication of newspaper-based platforms by coating of parylene C and patterning of metal layers. As-prepared parylene C-coated newspaper (PC-paper) provides low-cost, disposable, and mechanically and chemically stable electrochemical platforms for the development of potentiometric ion sensors for the detection of electrolyte cations, such as, H+ and K+. The pH and K+ sensors produced show near ideal Nernstian sensitivity, good repeatability, good ion selectivity, and low potential drift. These disposable, flexible ion sensors based on PC-paper platforms could provide new opportunities for the development of point-of-care testing sensors, for diagnostics, healthcare, and environment testing.

Attomolar detection of extracellular microRNAs released from living prostate cancer cells by a plasmonic nanowire interstice sensor.

Prostate cancer (PC) is the second leading cause of cancer death for men worldwide. The serum prostate-specific antigen level test has been widely used to screen for PC. This method, however, exhibits a high false-positive rate, leading to over-diagnosis and over-treatment of PC patients. Extracellular microRNAs (miRNAs) recently provided valuable information including the site and the status of the cancers and thus emerged as new biomarkers for several cancers. Among them, miR141 and miR375 are the most pronounced biomarkers for the diagnosis of high-risk PC. Herein, we report an attomolar detection of miR141 and miR375 released from living PC cells by using a plasmonic nanowire interstice (PNI) sensor. This sensor showed a very low detection limit of 100 aM as well as a wide dynamic range from 100 aM to 100 pM for all target miRNAs. In addition, the PNI sensor could discriminate perfectly the diverse single-base mismatches in the miRNAs. More importantly, the PNI sensor successfully detected the extracellular miR141 and miR375 released from living PC cell lines (LNCaP and PC-3), proving the diagnostic ability of the sensor for PC. We anticipate that the present PNI sensor can hold great promise for the precise diagnosis and prognosis of various cancer patients as well as PC patients.