All-silicon monolithic optoelectronic platform for multi-analyte biochemical sensing

Light emitting devices (LEDs) made with III-nitrides compound on c-plane sapphire substrate using metal organic chemical vapor deposition (MOCVD) have so many threading dislocation defects due to the lattice mismatch. [1, 2] Threading dislocations were caused some problems such as poor luminescence and leakage current. In order to reduce the problems from threading dislocation defects, v-shaped pit initiated from threading dislocations used to construct in III-nitrides compound of LEDs. [3] V-shaped pits were made using different growth rate of etch lattice plane at specific growth temperature. (called mid-temp GaN in Figure 1) Furthermore v-shaped pits grown this method were served as insulator due to a lack of magnesium doping density in pGaN layer. Therefore leakage current through the threading dislocation defects can be prevented by characteristic of v-shaped pits. However some v-shaped pits still have a problem of leakage current. In this paper, dimension and electrical properties of v-shaped pits were separated for identify the causes of leakage current. Figure 1 shows a diagram of v-shaped pit originated from threading dislocation which has an open hexagonal inverted pyramid. The ‘g’ samples show lower current at reverse bias voltage than that of ‘ng’ samples which shown in Figure 2. It means the ‘ng’ samples are acting like leakage source at reverse voltage. Although the ‘g’ samples go to saturation around 5 reverse voltage, the ‘ng’ samples cannot be saturated even at 15 reverse voltage. (Figure 3) It means the ‘ng’ samples have higher carrier concentrations than ‘g’ samples. SEM images are shown in Figure 4(a)-4(d). The mean diameter and depth of the ‘g’ samples are 330.4nm and 306.7nm, respectively. (Figure 4(a), 4(c)) On the other hand, the mean diameter and depth of ‘ng’ samples are 417.7nm and 387.1nm, respectively. (Figure 4(b), 4(d)) As can be seen, the pits of ‘g’ samples are smaller than that of ‘ng’ samples. It means etch samples had a different starting point to making the v-shaped pits. The ‘g’ samples were started to make the v-shaped pits during the mid-temperature GaN growth. However the v-shaped pits of the ‘ng’ sample were made as soon as began of the mid-temperature GaN growth. Some of threading dislocation defects were subjected to tensile stress due to heat budget during high-temperature GaN growth, after that v-shaped pits began to form immediately due to the lower growth temperature. As a result, leakage current was expected to occur the v-shaped pits enlarged by the tunneling effect. In order to solve this problem, evaluation was conducted the step by step decreasing the growth temperature during high-temperature GaN growth. Eventually, a advanced result was obtained to control the dimension of v-shaped pits.

The proven capability of optical biosensors for highly-sensitive biochemical determinations has not been proven so far adequate to render them into commercial, portable devices. Their advancement has mainly stumbled upon two challenges: the inherent inability of most sensors to integrate the optical source onto the same chip, and the need to specifically design the optical transducer per application. In this work, a radical approach for label-free multiplexed sensing is presented. It incorporates two significant novelties: (1) an all-silicon array of monolithically integrated optical transducers, all having their own excitation source but sharing a common detector, and (2) the Frequency-resolved Mach-Zehnder Interferometry (FR-MZI) principle of operation. Monolithically integrated FR-MZI devices showed a limit of detection of Δn=4×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> . The proposed device can be used interchangeably for a plethora of bio/chemical determinations becoming thus an unsurpassable versatile analytical tool.

Optical affinity biosensors are devices that incorporate a biomolecular recognition element (e.g. antibody) which specifically recognizes a particular analyte and an optical transduction system which allows quantification of the interaction between the analyte and the biomolecular recognition element. In the last decade we have witnessed development of numerous optical transduction methods, including both label-based methods such as fluorescence spectroscopy and label-free methods such as optical interferometry, spectroscopy of guided modes of optical waveguides, and surface plasmon resonance. Label-free optical biosensors present unique technology that enables direct observation of molecular interaction in real-time and offer benefits of rapid, sensitive and label-free detection of chemical and biological species with potential applications in numerous important areas including proteomics, medical diagnostics, environmental monitoring, food analysis, agriculture, and security.

Nanoparticle Bragg reflectors: A smart analytical tool for biosensing

Biosensors are effectively applied to detect specific samples in various areas, such as the ecosystem, biomedical, and food. Biosensing elements and transducers can categorize biosensors. The optical, mass, and thermal transducers used for optical-based biosensors. Sensitivity and accuracy for quantitative and qualitative measurements have been developed for the optical biosensor. This chapter presented fluorescence and SERS-based multifunctional, visual, and innovative biosensors for antibody immunoassay and biomarker applications. It has developed that optical-based systems involve enzymatic biosensors, immunosensors (sandwich immunosensor), biosensors for bacteria cells, proteins, and antibodies using Opto/electronic transduction of the biological process occurring at the sensing surface. The biological element can recognize a specific analyte’s presence, activity or concentration in solution. The detection can be a binding process and immobilization steps of antibodies on sensor surfaces and nonspecific protein binding, for instance, the binding method consists of an antibody, nucleic acid, receptor protein or cell receptor, and a synthetic receptor. Nanomaterials based biosensors can be a hope to offer novel techniques that may perhaps meet the current demand for early and rapid diagnosis of SARS-CoV-2 infections. However, optical biosensor offers alternate and additional methods for the testing and the potential as generated rapid results compared to test currently used for COVID-19 testing. This chapter focuses on the discussion of nanoparticles, some biological immobilization techniques, including physical and chemical immobilization. Optical-based transducers for biosensors using various optical determination applications such as SERS, voltammetric, colorimetric, and immunosensor platforms.

A thin linear array of silicon diodes has been developed to measure one-dimensional temperature profiles in tissue during treatment of cancer by localized hyperthermia. The array is composed of six discrete diodes on three flexible stainless steel wires, with a maximum cross-sectional dimension of 0.5 mm, so that it can be introduced into a tumor area via a small puncture wound. Temperature data are extracted using an external electronics system under microprocessor control; the present overall accuracy of the system is 0.2°C over the range of 37-45°C. The array has been tested in ultrasound, RF, and microwave heating fields. Computer simulation shows this array to be nonperturbing of the thermal field in tissue, so that it can provide accurate temperature data. Development of a batch-fabricated array of twenty diodes on five leads is under way. A monolithic silicon diode array is shown to produce large temperature perturbations because of its high thermal conductivity, while an alternative technology using silicon micromachining and adaptations of existing techniques for lead fabrication should produce an array of low thermal conductivity which can obtain accurate measurements. The present and future arrays should also be suitable for data collection in many in-vivo situations other than hyperthermia.

The growing demand for real-time, non-invasive, and cost-effective health monitoring has driven significant advancements in portable point-of-care testing (POCT) devices. Among these, optical biosensors have emerged as promising tools for the detection of critical biomarkers such as uric acid (UA) and blood glucose. Different optical transduction methods, like fluorescence, surface plasmon resonance (SPR), and colorimetric approaches, are talked about, with a focus on how sensitive, specific, and portable they are. Despite considerable advancements, several challenges persist, including sensor stability, miniaturization, interference effects, and the need for calibration-free operation. This review also explores issues related to cost-effectiveness, data integration, and wireless connectivity for remote monitoring. The review further examines regulatory considerations and commercialization aspects of optical biosensors, addressing the gap between research developments and clinical implementation. Future perspectives emphasize the integration of artificial intelligence (AI) and healthcare for improved diagnostics, alongside the development of wearable and implantable biosensors for continuous monitoring. Innovative optical biosensors have the potential to change the way people manage their health by quickly and accurately measuring uric acid and glucose levels. This is especially true as the need for decentralized healthcare solutions grows. By critically evaluating existing work and exploring the limitations and opportunities in the field, this review will help guide the development of more efficient, accessible, and reliable POCT devices that can improve patient outcomes and quality of life.

The aim of this work was the development and evaluation of a detector based on SiPMs and fast scintillation crystals feasible for combined PET and MR imaging. Properties of two different 4 × 4 arrays of SiPMs by Hamamatsu — breakdown voltage, pulse height, energy resolution, dark counts and optical crosstalk — were investigated in terms of temperature and voltage dependence. Each channel in such an array consists of either 400 or 1600 cells and has a surface area of 1 × 1 mm2. For the alignment and coupling of individual scintillation crystals (1 × 1 × 20 mm3) to these channels a special holder was designed. The breakdown voltages were at about 70 V for both models. Energy resolutions better than 23 % were observed. A temperature coefficient of the signal amplitude of (-2.7 ± 0.2) %/K and a voltage coefficient of (63 ± 2) %/V were determined for the model with 400 cells, whereas optical crosstalk was found to be an issue that needs further improvement. The dark count rate was below 1 MHz.

We have fabricated and tested freestanding low-temperature-grown GaAs photoconducting devices exhibiting subpicosecond photoresponse. The epitaxially grown thin-film microswitches were transferred on top of sapphire and Si/SiO2 substrates and integrated with Ti/Au coplanar strip transmission lines. Our devices exhibited above 200 V breakdown voltages and dark currents at 100 V below 3×10−7 A. The photoresponse of our microswitches was measured using electro-optic sampling technique with 100-fs-wide laser pulses at wavelengths of 810 nm and 405 nm as the excitation sources. For 810-nm excitation, we measured 0.55-ps-wide electrical transients with voltage amplitudes of up to 1.3 V. The ultraviolet excitation resulted in 1.35-ps-wide transients due to the hot carriers generation and intraband relaxation.

We propose a novel three-dimensional (3D) monolithic optoelectronic integration platform. Such platform integrates both electrical and photonic devices in a bulk silicon wafer, which eliminates the high-cost silicon-on-insulator (SOI) wafer and is more suitable for process requirements of electronic and photonic integrated circuits (ICs). For proof-of-concept, we demonstrate a three-dimensional photodetector and WDM receiver system. The Ge is grown on a 8-inch bulk silicon wafer while the optical waveguide is defined in a SiN layer which is deposited on top of it, with ~4 µm oxide sandwiched in between. The light is directed to the Ge photodetector from the SiN waveguide vertically by using grating coupler with a Aluminum mirror on top of it. The measured photodetector responsivity is ~0.2 A/W and the 3-dB bandwidth is ~2 GHz. Using such vertical-coupled photodetector, we demonstrated an 8-channel receiver by integrating a 1 × 8 arrayed waveguide grating (AWG). High-quality optical signal detection with up to 10 Gbit/s data rate is demonstrated, suggesting a 80 Gbit/s throughput. Such receiver can be applied to on-chip optical interconnect, DRAM interface, and telecommunication systems.

The hybridization of probe DNA with target DNA will lead to changes in the mass, electrical charge, or optical properties of the immobilized DNA layer, which can be detected by microgrativimetric, potentio-metric, amperometric or optical transducers. For this reason, we developed a new Localized Surface Plasmon Resonance (LSPR) based label-free optical biosensor in connection with a Porous Anodic Alumina (PAA) layer chip. For the fabrication of PAA layer chip, a double oxidation step method was developed, which used oxalic acid as oxidizing agent at an oxidation voltage of 40 V. In our sensor, the absorbance at surface of PAA layer chip resulted in an interferometric pattern that was related to the LSPR optical properties of bio-molecules. All absorbance spectra were taken from 400 to 850 nm on the UV-visible spectrophotometer at room temperature. The absorbance strength increased with the formation of double-helix with the probe target DNA hybridization. The reaction of mismatch DNA did not cause a significant increase in the absorbance, but only a slight bathochromic shift was observed. However, the binding of match DNA caused a significant bathochromic shift and increase in the absorbance indicating the complete hybridization. We expect that this detection method using LSPR based label-free optical biosensor can be used for analysis conveniently with high sensitivity, because there is no necessity of labeling such as the enzymes and the fluorescent dye.

Nanoengineered optical urea biosensor for estimating hemodialysis parameters in spent dialysate

In this work, an AlGaN/GaN power diode with edge-terminated Schottky/ohmic hybrid (ETH) anode is proposed. 2-D simulation is carried out to study the characteristics of the ETH-diode. The forward onset voltage V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> of the device can be modulated by thinning the barrier thickness beneath the Schottky gate region of the hybrid anode. With remaining AlGaN-barrier of 5 nm the V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> as low as 0.25 V is achieved in ETH-Diode. Comparing with the reference device the edge-termination (ET) integrated into the ETH-Diode enabling more than 5-order and 2-order leakage current reduction at -100 V and -300 V, respectively. Correspondingly, even using a more stringent criterion the breakdown voltage (BV) is improved from 400 V at I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">leakage</sub> =10 μA/mm to 510 V at I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">leakage</sub> =1 μA/mm in a device with anode-cathode spacing of 5 μm due to the employment of the edge-termination. By using a 2 μm field plate the BV of the ETH-Diode can be further improved to 800 V.

Fabrication of ZnO nanorod-based p–n heterojunction on SiC substrate

The accumulation of metal ions in organisms and the presence of heavy metals in water cause adverse effects on ecosystems and result in numerous human health issues such as cancer and neurogenerative diseases. Therefore, the development of novel platforms for metal-scavenging and rapid metal detection for in situ applications are of high importance. Here, this challenge is tackled by taking advantage of the metal chelation ability of a melanin-inspired material in combination with the near-infrared (NIR) fluorescence response of single-walled carbon nanotubes (SWCNTs) to surface binding. SWCNTs are functionalized by a melanin-like substance, obtained by enzymatic oxidative polymerization of a fluorenylmethyloxycarbonyl-tyrosine (FmocY) precursor. The resulting multicomponent system (SWCNT-FmocYOx) serves as a metal-ion scavenging platform that concurrently reports on metal binding with optical signal transduction. Upon binding of a library of mostly divalent transition metal-ions, the fluorescence emission of the functionalized SWCNTs is modulated, showing a concentration-dependent response with a limit of detection in the nanomolar range. Metal-binding and removal from water of up to 98% are further shown via inductively coupled plasma mass spectrometry. The SWCNT-FmocYOx hybrid system presents a novel platform with NIR optical signal for real-time feedback on metal-ion scavenging.