• Journal of Electrochemical Science and Technology
• /
• v.12 no.2
• /
• pp.225-229
• /
• 2021

Commercially available continuous glucose sensors require the operation stability for more than two weeks. Typically, the sensor comprises a sensing layer and an over-coating layer for the stable operation inside the body. In the sensing layer, enzymes and mediators are cross-linked together for the effective sensing of the glucose. The over-coating layer limits the flux of glucose and works as a biocompatible layer to the body fluids. Here, we report the simple preparation of the flux-limiting layer by the condensation of polyethyleneimine (PEI), tri-epoxide linker, and trimethylolpropane triglycidyl ether (PTGE). The sensor is constructed by a layer-by-layer drop-coating of the sensing layer containing glucose dehydrogenase and the PEI-derived blocking layer. It is stable for more than 14 days, which is enough for the sensor in the continuous monitor glucose monitoring (CGM) system.

• Journal of Sensor Science and Technology
• /
• v.21 no.4
• /
• pp.311-317
• /
• 2012

Disposable amperometric screen-printed biosensor strips have been fabricated by a sol-gel encapsulation for the analysis of glucose. The glucose oxidase(GOx) is entrapped in the gel matrix through sol-gel transition of tetraethoxysliane(TEOS). The biosensor is fabricated by GOx containing thin film of TEOS gel on the surface of screen-printed carbon electrode(SPCE). The GOx-containing thin film of TEOS gel offers a one-step modification process on the surface of SPCE. The optimum conditions for glucose determination have been characterized with respect to the applied potential, enzyme loading ratio, and pH. The linear range and detection limit of glucose detection were from 2.0 mM to 16.0 mM and 0.25 mM, respectively.

• Journal of Communications and Networks
• /
• v.13 no.2
• /
• pp.125-131
• /
• 2011

Rapid strides are being made to bring to reality the technology of wearable sensors for monitoring patients' physiological data.We study the problem of automatically detecting anomalies in themeasured blood glucose levels. The normal daily measurements of the patient are used to train a hidden Markov model (HMM). The structure of the HMM-its states and output symbols-are selected to accurately model the typical transitions in blood glucose levels throughout a 24-hour period. The learning of the HMM is done using historic data of normal measurements. The HMM can then be used to detect anomalies in blood glucose levels being measured, if the inferred likelihood of the observed data is low in the world described by the HMM. Our simulation results show that our technique is accurate in detecting anomalies in glucose levels and is robust (i.e., no false positives) in the presence of reasonable changes in the patient's daily routine.

• Journal of Sensor Science and Technology
• /
• v.22 no.5
• /
• pp.357-363
• /
• 2013

An ultraviolet pulsed laser ablation of polyimide film coated with platinum has been used to enhance the sensitivity for the application as an electrochemical biosensor. Densely packed cones are formed on polyimide surface after UV irradiation which results in increase of surface area. In order to apply the sensitivity improvement of laser ablated polyimide film electrodes, the glucose oxidase modified biosensor was fabricated by using an encapsulation in the gel matrix through sol-gel transition of tetraethoxysliane on the surface of laser ablated polyimide film. The optimum conditions for glucose determination have been characterized with respect to the applied potential and pH. The linear range and detection limit of glucose detection were from 2.0 mM to 18.0 mM and 0.18 mM, respectively. The sensitivity of glucose biosensors fabricated with laser ablated polyimide film is about three times higher than that of plain polyimide film due to increase in surface area by laser ablation.

• IEMEK Journal of Embedded Systems and Applications
• /
• v.15 no.4
• /
• pp.167-175
• /
• 2020

A blood-glucose meter is one of the in vitro diagnostic devices to measure and control the glucose concentration of diabetics. In order to measure the glucose level in the blood, the common method is to measure the amount of electrons, that is, the output current generated by glucose oxidation after a blood sample is inserted into the test strip containing an enzyme. The hematocrit is an obstacle in measuring accurate blood glucose concentration. This paper deals with the design and implementation of a blood-glucose meter to correct the hematocrit interference. We propose a sequential method which measures impedance using the alternating current and then measures glucose in the blood using the direct current. In addition, this paper introduces how to use commercial glucose strips based on the proposed system. Finally, we conducted the performance evaluation of the proposed system by comparing the measured current and impedance with those of the references. As a result, the standard deviation of the current measurement is approximately 0.6nA and the impedance measurement error for measuring the hematocrit is approximately within 1%. The proposed system will improve the accuracy of the conventional blood-glucose meter by reducing the hematocrit interference.

• Journal of Sensor Science and Technology
• /
• v.14 no.5
• /
• pp.291-296
• /
• 2005

In this paper, the PDMS based micromixer having 3-dimension triangular structure has been developed for the reaction of samples in the micro volume. The mixing efficiency was measured according to the change of Reynolds number (Re: 0.08, 0.8, 8, 16) and channel height (100, 200, $300{\mu}m$). Total length of mixing region is 7.4 mm and the measured mixing efficiencies at the outlet were over 85 %. Within the mixing length 2.4 mm, the mixing efficiencies were more than 70 % at any Reynolds numbers, and this indicates the strong mixing has occurred inside the mixing channel due the triangular structures. By employing these 2 mixers, we have fabricated the microreactor to detect the glucose-catalysts reaction. The microreactor showed good reactivity of glucose and enzymes with the small amount of sample solution.

• Journal of the Korean Electrochemical Society
• /
• v.17 no.3
• /
• pp.164-171
• /
• 2014

A highly sensitive and selective non-enzymatic glucose sensor has gained great attention because of simple signal transformation, low-cost, easily handling, and confirming the blood glucose as the representative technology. Until now, glucose sensor has been developed by the immobilization of glucose oxidase (GOx) on the surface of electrodes. However although GOx is quite stable compared with other enzymes, the enzyme-based biosensors are still impacted by various environment factors such as temperature, pH value, humidity, and toxic chemicals. Non-enzymatic sensor for direct detecting glucose is an attractive alternative device to overcome the above drawbacks of enzymatic sensor. Many efforts have been tried for the development of non-enzymatic sensors using various transition metals (Pt, Au, Cu, Ni, etc.), metal alloys (Pt-Pb, Pt-Au, Ni-Pd, etc.), metal oxides, carbon nanotubes and graphene. In this paper, we show that Ni-based nano-particles (NiNPs) exhibit remarkably catalyzing capability for glucose originating from the redox couple of $Ni(OH)_2/NiOOH$ on the surface of ITO electrode in alkaline medium. But, these non-enzymatic sensors are nonselective toward oxidizable species such as ascorbic acid the physiological fluid. So, the anionic polymer was coated on NiNPs electrode preventing the interferences. The oxidation of glucose was highly catalyzed by NiNPs. The catalytically anodic currents were linearly increased in proportion to the glucose concentration over the 0~6.15 mM range at 650 mV versus Ag/AgCl.

• Korean Journal of Materials Research
• /
• v.19 no.1
• /
• pp.44-49
• /
• 2009

Conjugated nanocrystals using CdSe/ZnS core/shell nanocrystal quantum dots modified by organic linkers and glucose oxidase (GOx) were prepared for use as biosensors. The trioctylphophine oxide (TOPO)-capped QDs were first modified to give them water-solubility by terminal carboxyl groups that were bonded to the amino groups of GOx through an EDC/NHS coupling reaction. As the glucose concentration increased, the photoluminescence intensity was enhanced linearly due to the electron transfer during the enzymatic reaction. The UV-visible spectra of the as-prepared QDs are identical to that of QDs-MAA. This shows that these QDs do not become agglomerated during ligand exchanges. A photoluminescence (PL) spectroscopic study showed that the PL intensity of the QDs-GOx bioconjugates was increased in the presence of glucose. These glucose sensors showed linearity up to approximately 15 mM and became gradually saturated above 15 mM because the excess glucose did not affect the enzymatic oxidation reaction past that amount. These biosensors show highly sensitive variation in terms of their photoluminescence depending on the glucose concentration.

• Journal of Biomedical Engineering Research
• /
• v.30 no.3
• /
• pp.185-190
• /
• 2009

Biomedical mobile devices for ubiquitous healthcare consist of biomedical sensors and communication terminal. They have two types of configuration. One is the sensor-network type device using wired or wireless communication with intelligent sensors to acquire biomedical data. The other is the sensor embedded type device, where the data can be acquired directly by itself. There are many examples of sensor network type, such as, fall detection sensor, blood glucose sensor, and ECG sensors networked with commercial PDA phone and commercial phone terminal for ubiquitous healthcare. On the other hand, sensor embedded type mounts blood glucose sensor, accelerometer, and etc. on commercial phone. However, to enable true ubiquitous healthcare, motion sensing is essential, because users go around anywhere and their signals should be measured and monitored, when they are affected by the motion. Therefore, in this paper, two biomedical mobile devices with motion monitoring function were addressed. One is sensor-network type with motion monitoring function, which uses Zigbee communication to measure the ECG, PPG and acceleration. The other is sensor-embedded type with motion monitoring function, which also can measure the data and uses the built-in cellular phone network modem for remote connection. These devices are expected to be useful for ubiquitous healthcare in coming aged society in Korea.

• Proceedings of the KIEE Conference
• /
• 2006.07c
• /
• pp.1627-1628
• /
• 2006

In this paper, mesoporous only platinum electrode and micro pore platinum electrode with mesoporous Pt are fabricated and characterized on a silicon substrate to check their usability as enzymeless sensing electrodes for developing non-disposable glucose sensors integrated with silicon CMOS read out circuitry. Since most of electrochemical glucose sensors are disposable due to the use of the enzymes that are living creatures, these are limited to use in the in-vivo and continuous monitoring system applications. The proposed mesoporous Pt electrode with approximately 2.5nm in pore diameter and 150nm in height was fabricated by using a nonionic surfactant $C_{16}EO_8$ and an electroplating technique. The micro pore Pt electrode with mesoporous Pt means the mesoporous Pt electrode fabricated on top of micro pore arrayed Pt electrode with approximately $10{\mu}m$ in pore diameter and $80{\mu}m$ in height. The measured current responses at 10mM glucose solution of plane Pt, micro pore Pt, micro pore with mesoporus Pt, and mesoporous Pt electrodes are approximately $9.9nA/mm^2$, $92.4nA/mm^2$, $3320nA/mm^2$ and $44620nA/mm^2$, respectively. These data indicate that the mesoporous Pt electrode is much more sensitive than the other Pt electrodes. Thus, it is promising for non-disposable glucose sensor and electrochemical sensor applications.