Millimeter-Scale Piezoresistive Cantilevers for Accurate Force Measurements at the Nano-Newton Level

This paper reports a development of millimeter-scale cantilevers equipped with piezoresistive deflection sensing metrology as a force sensor at the micro- and nano-Newton level. The cantilevers was designed and fabricated to minimize the error during the force transfer or calibration, so that they have full-bridge type piezoresistors, a large length and width and reference marks to facilitate the positioning of probes or tips onto the piezoresistive cantilevers. Their 6 mm-long and 0.4 mm-wide dimensions can reduce the error due to incomplete contact (or loading) position. The reference marks on the cantilever can give you a range of stiffness and force sensitivity with a single piezoresistive cantilever. The stiffness can vary from 25 N m^?1 at the first mark to 0.04 N m^?1 at the last. The full-bridge piezoresistors give an electrical signal proportional to the applied force with superior temperature independency. The fabricated piezoresistive cantilevers were calibrated with the KRISS nano force calibrator (NFC). The results showed that the stiffness and the force sensitivity at the last mark was determined to be 0.0502 N m^?1 and 0.357 (mV/V) μN^?1, respectively. The performances were tested by calibrating stiffness of commercial cantilevers using the cantilever-on-cantilever method with a fabricated cantilever and comparing calibration results with stiffness obtained from calibration using the NFC. Two results match to each other within approximately 10 % discrepancy.     

Self‐repair behaviour of the neuronal cell membrane by conductive atomic force indentation

Conductive atomic force indentation (CAFI) was proposed to study the self‐repair behaviour of the neuronal cell membrane here. CAFI was used to detect the changes of membrane potentials by performing the mechanical indentation on neurons with a conductive atomic force microscope. In the experiment, a special insulation treatment was made on the conductive probe, which turned out to be a conductive nanoelectrode, to implement the CAFI function. The mechanical properties of the neuronal cell membrane surface were tested and the membrane potential changes of neurons cultured in vitro were detected. The self‐repair behaviour of the neuronal cell membrane after being punctured was investigated. The experiment results show that CAFI provides a new way for the study of self‐repair behaviours of neuronal cell membranes and mechanical and electrical properties of living cells.Inspec keywords: neurophysiology, bioelectric potentials, indentation, membranes, biomembranes, probes, cellular biophysics, atomic force microscopyOther keywords: CAFI, self‐repair behaviour, membrane potentials, neurons, conductive atomic force microscope, conductive probe, conductive nanoelectrode, neuronal cell membrane surface, membrane potential changes, conductive atomic force indentation     

Investigation of graphene‐on‐metal substrates for SPR‐based sensor using finite‐difference time domain

In this study, the authors investigated the effects of a single layer graphene as a coating layer on top of metal thin films such as silver, gold, aluminum and copper using finite‐difference time domain method. To enhance the resolution of surface plasmon resonance (SPR) sensor, it is necessary to increase the SPR reflectivity and decrease the full‐width‐half maximum (FWHM) of the SPR curve so that there is minimum uncertainty in the determination of the resonance dip. Numerical data was verified with analytical and experimental data where all the data were in good agreement with resonance angle differing in <10% due to noise present in components such as humidity and temperature. In further analysis, reflectivity and FWHM were compared among four types of metal with various thin film thicknesses where graphene was applied on top of the metal layers, and data was compared against pure conventional metal thin films. A 60 nm‐thick Au thin film results in higher performance with reflectivity of 92.4% and FWHM of 0.88° whereas single layer graphene‐on‐60 nm‐thick Au gave reflectivity of 91.7% and FWHM of 1.32°. However, a graphene‐on‐40 nm‐thick Ag also gave good performance with narrower FWHM of 0.88° and reflection spectra of 89.2%.Inspec keywords: graphene, surface plasmon resonance, finite difference time‐domain analysis, reflectivity, metallic thin films, silver, gold, aluminium, copper, chemical sensors, biological techniquesOther keywords: graphene‐on‐metal substrates, SPR‐based sensor, finite‐difference time domain, metal thin films, surface plasmon resonance sensor, SPR curve, resonance angles, reflectivity, C, Ag, Au, Al, Cu     

A Front-Side Released Single Crystalline Silicon Piezoresistive Microcantilever Sensor

This paper presents the design, fabrication, and characterization of a piezoresistive microcantilever sensor fabricated on silicon-on-insulator (SOI) wafers. The microcantilever consists of two silicon dioxide supporting layers and a single crystalline SOI layer in-between. The piezoresistors are implanted in the surface of the SOI layer to exploit its large piezoresistive coefficients. Laminated beam theory is employed to design the microcantilevers and the piezoresistors. A front-side releasing method is developed to suspend the microcantilevers by isotropically etching the substrate beneath the microcantilevers from the front-side of the wafers using ${rm SF}_{6}$ plasma. The features of SOI wafers and the front-side releasing enable high uniformity and high yield for the fabrication of piezoresistive microcantilever sensors. The sensors are validated using specific binding reaction of antigen and antibody of immunoglobulin G on the sensor surface, and the experimental results show that they are promising for portable and integrated sensing applications.      

Synthesis,stability, and in vitro oral cancer cell toxicity of human serum albumin stabilised gold nanoflowers

Gold nanoflowers (GNFs) prepared by reduction of HAuCl₄ by ascorbic acid were capped with human serum albumin (HSA) by either electrostatic or covalent attachment to prevent their self‐aggregation. Measurement of surface plasmon resonance absorbance changes under different stress conditions showed that GNFs stabilised by covalent attachment of HSA were more stable than those stabilised by electrostatic attachment. Cytotoxicity of the covalently conjugated GNF was also studied in cultured human oral cancer cell lines by measuring the metabolic activity via 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay.Inspec keywords: proteins, molecular biophysics, biomedical materials, reduction (chemical), gold, cellular biophysics, nanofabrication, biochemistry, surface plasmon resonance, cancer, nanomedicine, materials preparation, nanostructured materialsOther keywords: Au, human serum albumin stabilised gold nanoflowers, cytotoxicity, in vitro oral cancer cell toxicity, stress conditions, surface plasmon resonance absorbance, 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay, self‐aggregation, covalent attachment, electrostatic attachment, ascorbic acid, cultured human oral cancer cell lines     

Gold nanoparticles decorated reduced graphene oxide nanolabel for voltammetric immunosensing

This study describes the development and testing of a simple and novel enzyme‐free nanolabel for the detection and signal amplification in a sandwich immunoassay. Gold nanoparticles decorated reduced graphene oxide (rGOAu) was used as the nanolabel for the quantitative detection of human immunoglobulin G (HIgG). The rGOAu nanolabel was synthesised by one pot chemical reduction of graphene oxide and chloroauric acid using sodium borohydride. The pseudo‐peroxidase behaviour of rGOAu makes the nanolabel unique from other existing labels. The immunosensing platform was fabricated using self‐assembled monolayers of 11‐mercaptoundecanoic acid (11‐MUDA) on a gold disc electrode. The covalent immobilisation of antibody was achieved through the bonding of the carboxyl group of 11‐MUDA and the amino group of the antibody using chemical linkers [1‐ethyl‐3‐(3‐dimethylaminopropyl)carbodiimide] and N ‐hydroxysuccinimide. The fabricated immunosensor exhibited a linear range that included HIgG concentrations of 62.5–500 ng ml⁻¹. The sensor was also used for the testing of HIgG in the blood sample.Inspec keywords: proteins, nanomedicine, reduction (chemical), chemical sensors, nanofabrication, electrochemical sensors, voltammetry (chemical analysis), gold, oxidation, self‐assembly, monolayers, molecular biophysics, biochemistry, biosensors, nanoparticles, nanosensors, blood, grapheneOther keywords: gold nanoparticles, voltammetric immunosensing, enzyme‐free nanolabel, signal amplification, sandwich immunoassay, human immunoglobulin G, rGOAu nanolabel, chloroauric acid, sodium borohydride, 11‐mercaptoundecanoic acid, 11‐MUDA, gold disc electrode, chemical linkers, 1‐ethyl‐3‐(3‐dimethylaminopropyl)carbodiimide], HIgG concentrations, reduced graphene oxide nanolabel, quantitative HIgG detection, one pot chemical reduction, covalent antibody immobilisation, carboxyl group bonding, pseudo‐peroxidase behaviour, self‐assembled monolayers, N‐hydroxysuccinimide, immunosensor, blood sample, Au‐CO     

Effect of solution pH and adsorbent concentration on the sensing parameters of TGN‐based electrochemical sensor

The response of trilayer graphene nanoribbon (TGN)‐based ion‐sensitive field‐effect transistor (ISFET) to different pH solutions and adsorption effect on the sensing parameters are analytically studied in this research. The authors propose a TGN‐based sensor to electrochemically detect pH. To this end, absorption effect on the sensing area in the form of carrier concentration, carrier velocity, and conductance variations are investigated. Also, the caused electrical response on TGN as a detection element is analytically proposed, in which significant current decrease of the sensor is observed after exposure to high pH values. In order to verify the accuracy of the model, it is compared with recent reports on pH sensors. The TGN‐based pH sensor exposes higher current compared to that of carbon nanotube (CNT) counterpart for analogous ambient conditions. While, the comparative results demonstrate that the conductance of proposed model is lower than that of monolayer graphene‐counterpart for equivalent pH values. The results confirm that the conductance of the sensor is decreased and V_g‐min is obviously right‐shifted by increasing value of pH. The authors demonstrate that although there is not the experimental evidence reported in the part of literature for TGN sensor, but the model can assist in comprehending experiments involving nanoscale pH sensors.Inspec keywords: adsorption, graphene, ion sensitive field effect transistors, nanoribbons, electrochemical sensors, pH measurement, nanosensors, absorptionOther keywords: adsorbent concentration, TGN‐based electrochemical sensor, trilayer graphene nanoribbon‐based ion‐sensitive field‐effect transistor, adsorption effect, carbon nanotube counterpart, monolayer graphene‐counterpart, nanoscale pH sensors, pH solution effect, TGN‐based pH sensor, ISFET, CNT, C     

Highly selective sensor for the detection of Hg2+ ions using homocysteine functionalised quartz crystal microbalance with cross‐linked pyridinedicarboxylic acid

This study reports an insightful portable vector network analyser (VNA)‐based measurement technique for quick and selective detection of Hg²⁺ ions in nanomolar (nM) range using homocysteine (HCys)‐functionalised quartz‐crystal‐microbalance (QCM) with cross‐linked‐pyridinedicarboxylic acid (PDCA). The excessive exposure to mercury can cause damage to many human organs, such as the brain, lungs, stomach, and kidneys, etc. Hence, the authors have proposed a portable experimental platform capable of achieving the detection in 20–30 min with a limit of detection (LOD) 0.1 ppb (0.498 nM) and a better dynamic range (0.498 nM–6.74 mM), which perfectly describes its excellent performance over other reported techniques. The detection time for various laboratory‐based techniques is generally 12–24 h. The proposed method used the benefits of thin‐film, nanoparticles (NPs), and QCM‐based technology to overcome the limitation of NPs‐based technique and have LOD of 0.1 ppb (0.1 μg/l) for selective Hg²⁺ ions detection which is many times less than the World Health Organization limit of 6 μg/l. The main advantage of the proposed QCM‐based platform is its portability, excellent repeatability, millilitre sample volume requirement, and easy process flow, which makes it suitable as an early warning system for selective detection of mercury ions without any costly measuring instruments.Inspec keywords: quartz crystal microbalances, chemical sensors, microsensors, mercury (metal), nanosensors, nanoparticles, network analysers, chemical variables measurement, portable instruments, polymers, thin film sensorsOther keywords: mercury ion detection, homocysteine functionalised quartz crystal microbalance, cross‐linked pyridinedicarboxylic acid, mental retardation, Hunter–Russell syndrome, portable experimental platform, LOD, laboratory‐based techniques, NP‐based technique, QCM‐based microelectromechanical system technology, homocysteine‐functionalised quartz crystal microbalance, portable vector network analyser‐based measurement technique, World Health Organization, WHO, limit of detection, PDCA, HCys, nanoparticles, time 20.0 min to 30.0 min, time 12.0 hour to 24.0 hour, Hg     

Polymer nanocomposite nanomechanical cantilever sensors: material characterization, device development and application in explosive vapour detection

This paper reports an optimized and highly sensitive piezoresistive SU-8 nanocomposite microcantilever sensor and its application for detection of explosives in vapour phase. The optimization has been in improving its electrical, mechanical and transduction characteristics. We have achieved a better dispersion of carbon black (CB) in the SU-8/CB nanocomposite piezoresistor and arrived at an optimal range of 8-9 vol% CB concentration by performing a systematic mechanical and electrical characterization of polymer nanocomposites. Mechanical characterization of SU-8/CB nanocomposite thin films was performed using the nanoindentation technique with an appropriate substrate effect analysis. Piezoresistive microcantilevers having an optimum carbon black concentration were fabricated using a design aimed at surface stress measurements with reduced fabrication process complexity. The optimal range of 8-9 vol% CB concentration has resulted in an improved sensitivity, low device variability and low noise level. The resonant frequency and spring constant of the microcantilever were found to be 22 kHz and 0.4 N m(-1) respectively. The devices exhibited a surface stress sensitivity of 7.6 ppm (mN m(-1))(-1) and the noise characterization results support their suitability for biochemical sensing applications. This paper also reports the ability of the sensor in detecting TNT vapour concentration down to less than six parts per billion with a sensitivity of 1 mV/ppb.     

A micro force sensor based on a single ZnO belt coated with chromium film

A micro force sensor was fabricated using a single ZnO belt coated with ultra thin Cr film. As a result of the piezoresistive effect of the ultra thin (in nano-scale) Cr film, the bending of the belt led to the change in the resistance of ultra thin Cr film. Based on the mechanics of the materials, the relationship between the deformation and the force was calculated, and a linear relationship between the bending force and the resistance of Cr thin film was deduced at small bending regions. Dielectrophoresis, focused ion beam (FIB) and sputtering were used in the process of the micro force sensor. The experimental results show that the resistance of Cr film is sensitive to the bending force and demonstrate the potential for developing a new class of stable and sensitive nano-sized structures for force sensing.     

Design of High-Sensitivity Cantilever and Its Monolithic Integration With CMOS Circuits

Rectangular piezoresistive cantilevers with stress concentration holes opened were designed and fabricated in order to increase the response signals of piezoresistive cantilever first. Both the simulations and the measurements on the cantilever sensitivity show that this design can obviously result in an improvement on the displacement sensitivity of the piezoresistive cantilever. After a characterization study on the piezoresistive cantilever, a monolithic integration of the microcantilever array with a complementary metal-oxide-semiconductor (CMOS) readout circuitry based on the silicon-on-insulator (SOI) CMOS and the SOI micromachining technologies was designed. A cantilever array, a digital controlled multiplexer, and an instrumentation amplifier compose the integrated sensor system, and post-CMOS process was designed to fabricate the integrated system. The measurement results on the SOI CMOS circuitry of the integrated system prove a feasibility of the integration design     

Silver nanoparticles fabricated using medicinal plant extracts show enhanced antimicrobial and selective cytotoxic propensities

Nanoparticles fabricated using medicinal plant extract have great potential in the area of nanomedicine. High surface‐to‐volume ratio of nanoparticle enhances the local active biomolecules concentration, leading to many fold increase in the medicinal potentials. The silver nanoparticles (AgNPs) fabricated using indigenous medicinal plants of India, Azadirachta indica and Syzygium cumini, have shown a significant effect on the viability of prokaryotic and eukaryotic cells. Biofabrication of AgNP was confirmed using different spectroscopic and microscopic techniques. Extraction and purification of AgNP from non‐conjugated plant moieties are done using centrifugation and size exclusion chromatography. The cytotoxic propensity of AgNP formulations was screened against Gram‐positive (Bacillus subtilis), Gram‐negative (Escherichia coli) bacteria, cancerous (HT1080) and non‐cancerous (HEK293) cell lines. The nanoparticle formulations showed a relatively higher cytotoxic propensity against Gram‐positive bacteria and cancerous cell lines. In addition, the surface roughness and reactive oxygen species (ROS) measurements indicated that AgNP formulations mediate the cell activity predominantly by ROS‐mediated disruptive change in membrane morphology upon direct interaction with the membrane. Hence, the nanoparticle formulations show an enhanced selective cytotoxic propensity towards Gram‐positive bacteria and cancerous cell lines.Inspec keywords: nanofabrication, chromatography, nanoparticles, purification, toxicology, drugs, drug delivery systems, antibacterial activity, microorganisms, cancer, silver, surface roughness, nanomedicine, cellular biophysicsOther keywords: medicinal plant extracts, medicinal potentials, prokaryotic cells, eukaryotic cells, microscopic techniques, nonconjugated plant moieties, centrifugation, AgNP formulations, noncancerous cell lines, nanoparticle formulations, Gram‐positive bacteria, cancerous cell lines, surface roughness, cell activity, local active biomolecule concentration     

Observation of targeted gold nanoparticles in nasopharyngeal tumour nude mice model through dual‐energy computed tomography

This study was performed to specify the efficiency of imaging nanoparticle concentration as contrast media in dual‐energy computed tomography (DECT). Gold nanoparticles (AuNPs) and gold nanoparticles‐conjugated folic acid through cysteamine (FA‐Cya‐AuNPs) were both considered as contrast agents. Characterization of NPs was performed using Dynamic Light Scattering (DLS) and zeta potential. The hemocompatibility of NPs was confirmed by different blood parameters such as white blood cell, red cell distribution width, hemoglobin, lymphocytes counts and haemolysis assay. DECT algorithm was confirmed using calibration phantom at different concentrations of NPs and tube potentials (80 and 140 kVp). Then, DECT was used to quantify the concentration of both AuNPs and FA‐Cys‐AuNPs in human nasopharyngeal cancer cells. Mice were injected with non‐targeted AuNPs and targeted AuNps at a concentration of 3 × 10³ μg/ml. Then, they were scanned with different tube potentials. The concentration of nanoparticles in the various organs of nude mice was measured through DECT imaging and inductively coupled plasma mass spectrometry (ICP‐MS) analysis. The results of DECT images were compared with ICP‐MS analysis and indicated that they were approximately similar. In sum, FA‐Cys‐AuNPs can be a proper candidate for targeted contrast media in DECT molecular scanning of human nasopharyngeal tumours.     

Method development for optimised green synthesis of gold nanoparticles from Millettia pinnata and their activity in non‐small cell lung cancer cell lines

Green synthesis of gold nanoparticles (GNPs) has received substantial attention, because nanoparticles are produced in an eco‐friendly way using biomolecules present in plant extracts in a single step reaction. This research article highlights GNPs obtained using shade‐dried leaf extracts of Millettia pinnata (L.) with aqueous auric chloride (HAuCl₄) at ambient temperature. In the present study, GNPs with average particle size 37 nm in size were fabricated. Furthermore, the synthesis method to obtain stable and monodispersed GNPs was advanced by optimising enzyme concentration 100 μg/ml, pH 5.4, substrate concentration 0.45 mM and 12 h time of reaction. The confirmation of GNPs formation and characterisation was followed by UV‐vis‐absorption spectroscopy, dynamic light scattering (DLS), and zeta potential (ZP) for the analysis of shape, size, and stability, respectively. TEM images and powder XRD revealed the GNPs synthesis of spherical‐shaped nanoparticles in the face‐centred cubic arrangement. Cytotoxicity of GNPs was studied against A549 lung cancer cells with IC₅₀ 14.76 μg/ml and found lower as compared to doxorubicin IC₅₀ 11.23 μg/ml but significant enough to be used as a vehicle GNPs produced using green source can be used as significant therapeutic agents and drug delivery carriers.Inspec keywords: nanomedicine, molecular biophysics, cancer, electrokinetic effects, pH, transmission electron microscopy, toxicology, gold, cellular biophysics, X‐ray diffraction, lung, biomedical materials, nanofabrication, nanoparticles, particle size, enzymes, visible spectra, ultraviolet spectra, light scattering, biochemistryOther keywords: method development, optimised green synthesis, gold nanoparticles, millettia pinnata, nonsmall cell lung cancer cell lines, plant extracts, single step reaction, shade‐dried leaf extracts, aqueous auric chloride, synthesis method, stable GNPs, monodispersed GNPs, spherical‐shaped nanoparticles, A549 lung cancer cells, green source, particle size, enzyme concentration, substrate concentration, biomolecules, reaction time, UV‐visible‐absorption spectroscopy, dynamic light scattering, zeta potential, TEM images, powder XRD, face‐centred cubic arrangement, cytotoxicity, pH, therapeutic agents, drug delivery carriers, time 12.0 hour, Au     

Synthesis,radiolabelling, and biological assessment of folic acid‐conjugated G‐3 99m Tc‐dendrimer as the breast cancer molecular imaging agent

Hence, in this study, the authors aimed to develop a dendrimer‐based imaging agent comprised of poly(ethylene glycol) (PEG)‐citrate, technetium‐99 m (^99m Tc), and folic acid. The dendrimer‐G3 was synthesised and conjugated with folic acid, which confirmed by Fourier transform infrared, proton nuclear magnetic resonance, dynamic light scattering, and transition electron microscopy. 2,3‐bis‐(2‐methoxy‐4‐nitro‐5‐sulfophenyl)‐2H‐Tetrazolium‐5‐Carboxanilide cytotoxicity assay kit was used to measure the cellular toxicity of dendrimer. Imaging and biodistribution studies were conducted on the mice bearing tumour. The results showed that the fabricated dendrimer‐G3 has a size of 90 ± 3 nm, which was increased to 100 ± 4 nm following the conjugation with folic acid. The radiostablity investigation showed that the fabricated dendrimers were stable in the human serum at various times. Toxicity assessment confirmed no cellular toxicity against HEK‐293 cells at 0.25, 0.5, 1, 2, 4, and 8 mg/μl concentrations. The in vivo studies demonstrated that the synthesised dendrimers were able to provide a bright SPECT image applicable for tumour detection. In conclusion, the authors’ study documented the positive aspects of PEG‐citrate dendrimer conjugated with folic acid as the SPECT contrast agent for breast cancer detection.Inspec keywords: toxicology, single photon emission computed tomography, technetium, cancer, bone, polymers, biochemistry, tumours, electrospinning, biomedical materials, light scattering, cellular biophysics, Fourier transform infrared spectra, proton magnetic resonance, transmission electron microscopy, biological organsOther keywords: biodistribution, toxicity assessment, cellular toxicity, bright SPECT image, PEG‐citrate dendrimer, breast cancer molecular imaging agent, proton nuclear magnetic resonance, dendrimer‐based imaging agent, folic acid‐conjugated G‐^399m Tc‐dendrimer, dendrimer‐G3, poly(ethylene glycol)‐citrate, Fourier transform infrared spectra, dynamic light scattering, transition electron microscopy, 2,3‐bis‐(2‐methoxy‐4‐nitro‐5‐sulfophenyl)‐2H‐tetrazolium‐5‐carboxanilide cytotoxicity assay, human serum, tumour detection     

Overcoming the blood–brain barrier in neurodegenerative disorders and brain tumours

Drug delivery is one of the major challenges in the treatment of central nervous system disorders. The brain needs to be protected from harmful agents, which are done by the capillary network, the so‐called blood–brain barrier (BBB). This protective guard also prevents the delivery of therapeutic agents to the brain and limits the effectiveness of treatment. For this reason, various strategies have been explored by scientists for overcoming the BBB from disruption of the BBB to targeted delivery of nanoparticles (NPs) and cells and immunotherapy. In this review, different promising brain drug delivery strategies including disruption of tight junctions in the BBB, enhanced transcellular transport by peptide‐based delivery, local delivery strategies, NP delivery, and cell‐based delivery have been fully discussed.Inspec keywords: drugs, tumours, neurophysiology, blood, biochemistry, brain, drug delivery systems, nanoparticles, biomedical materials, molecular biophysics, cellular biophysics, nanomedicine, diseases, proteins, reviewsOther keywords: blood–brain barrier, neurodegenerative disorders, central nervous system disorders, BBB, therapeutic agents, targeted delivery, peptide‐based delivery, local delivery strategies, NP delivery, cell‐based delivery, brain drug delivery strategies, brain tumours, nanoparticles, immunotherapy, review     

Nano‐biosensor based on reduced graphene oxide and gold nanoparticles,for detection of phenylketonuria‐associated DNA mutation

Phenylketonuria (PKU)‐associated DNA mutation in newborn children can be harmful to his health and early detection is the best way to inhibit consequences. A novel electrochemical nano‐biosensor was developed for PKU detection, based on signal amplification using nanomaterials, e.g. gold nanoparticles (AuNPs) decorated on the reduced graphene oxide sheet on the screen‐printed carbon electrode. The fabrication steps were checked by field emission scanning electron microscope imaging as well as cyclic voltammetry analysis. The specific alkanethiol single‐stranded DNA probes were attached by self‐assembly methodology on the AuNPs surface and Oracet blue was used as an intercalating electrochemical label. The results showed the detection limit of 21.3 fM and the dynamic range of 80–1200 fM. Moreover, the selectivity results represented a great specificity of the nano‐biosensor for its specific target DNA oligo versus other non‐specific sequences. The real sample simulation was performed successfully with almost no difference than a synthetic buffer solution environment.Inspec keywords: biosensors, nanosensors, nanoparticles, graphene compounds, gold, nanomedicine, DNA, molecular biophysics, biomedical equipment, electrochemical sensors, electrochemical electrodes, field emission scanning electron microscopy, voltammetry (chemical analysis), self‐assembly, biochemistryOther keywords: reduced graphene oxide, gold nanoparticles, phenylketonuria‐associated DNA mutation, newborn children, electrochemical nanobiosensor, signal amplification, nanomaterials, reduced graphene oxide sheet, screen‐printed carbon electrode, field emission scanning electron microscopy imaging, cyclic voltammetry, alkanethiol single‐stranded DNA probes, self‐assembly methodology, Oracet blue, intercalating electrochemical label, Au‐CO     

Optimization of sputtered Cr/Au thin film for diaphragm-based MEMS applications

An optimization study on the sputtering of Cr/Au thin film for diaphragm-based MEMS applications is presented. The effects of the film thickness, process pressure and process power on the residual stress of the film are investigated. A low-stress silicon nitride diaphragm-based device characterization platform is fabricated to study the influence of the Cr/Au film stress on the diaphragm compliance. The fabricated devices are characterized by measuring the capacitance change under a bias voltage from 0 to 40 V. For the 8-µm and 10-µm air gap device characterization platforms, the largest capacitance changes of 5.1% and 4.3%, respectively, occur at a compressive film stress of − 200 MPa. A large capacitance change indicates a more sensitive diaphragm, which is desired in pressure sensor design.     

Core/shell nanoassembly of amphiphilic naproxen‐polyethylene glycol: synthesis,characterisation and evaluation as drug delivery system

Small molecule‐based amphiphiles self‐assemble into nanostructures (micelles) in aqueous medium which are currently being explored as novel drug delivery systems. Here, naproxen‐polyethylene glycol (N‐PEG), a small molecule‐derived amphiphile, has been synthesised, characterised and evaluated as hydrophobic drug carrier. ¹ H, ¹³ C Nuclear magnetic resonance (NMR), mass spectrometry (MS) and Fourier‐transform infrared spectroscopy (FTIR) confirmed the formation of N‐PEG and dynamic light scattering (DLS) revealed the formation of nano‐sized structures of ∼228 nm. Transmission electron microscope (TEM) analysis showed aggregation behaviour of the structures with average size of ∼230 nm. Biodegradability aspect of the micellar‐structured N‐PEG was demonstrated by lipase‐mediated degradation studies using DLS and TEM. High encapsulation efficiency followed by release in a sustained manner of a well‐known anticancer drug, doxorubicin, demonstrated the feasibility of the new drug delivery system. These results advocate the promising potential of N‐PEG micelles as efficient drug delivery system for specific delivery to cancerous cells in vitro and in vivo.Inspec keywords: cancer, biodegradable materials, cellular biophysics, encapsulation, biomedical materials, drugs, nanofabrication, drug delivery systems, nanomedicine, self‐assembly, nanoparticles, transmission electron microscopy, colloids, molecular biophysics, light scattering, hydrophobicity, biochemistry, enzymes, core‐shell nanostructures, nanocomposites, proton magnetic resonance, Fourier transform infrared spectra, mass spectroscopic chemical analysisOther keywords: hydrophobic drug carrier, nanosized structures, transmission electron microscope analysis, doxorubicin, N‐PEG micelles, core/shell nanoassembly, amphiphilic naproxen‐polyethylene glycol, drug delivery system, small molecule‐based amphiphiles self‐assemble, small molecule‐derived amphiphile, ¹ H NMR, ¹³ C NMR, MS, FTIR, dynamic light scattering, aggregation behaviour, biodegradability aspect, lipase‐mediated degradation studies, encapsulation efficiency, cancerous cells     

Design and fabrication of piezoresistive strain gauges based on nanocrystalline diamond layers

The paper reports on design, fabrication and characterization of piezoresistive sensors based on boron doped nanocrystalline diamond (NCD) layers. The shape and position of the piezoresistive element was optimized using finite element 3D modeling. Mechanical and piezoresistive simulations were performed. The piezoresistive sensing boron doped diamond thin films were realized on SiO₂/Si₃N₄/Si substrates by microwave plasma enhanced chemical vapor deposition (CVD) and the piezoresistive structures were formed by reactive ion etching. The extensive study of sensor parameters e.g. deformation sensitivity, edge and contact resistances, temperature dependences gauge factor, temperature coefficient of resistance and bridge output voltage was performed. The highest gauge factor at higher temperatures (GF = 7.2 at 250 °C) was observed for moderate doping level (boron to carbon ratio of 3000 ppm). One of the aims was the extraction of piezoresistive coefficients of fabricated diamond layers for utilization in a finite element piezoresistive solver.