Bifunctional Sensor Research Articles

Graphene/MXene/Cellulose cellulosic paper-based flexible bifunctional sensors utilizing molecular bridge strategy with tunable piezoresistive effect for Temperature-Pressure sensing

Wearable technology is changing the way we interact with the digital world. Wearable systems can enable a smarter lifestyle when connected to other smart devices. This work reports a bifunctional sensor prepared from cellulosic paper as substrate for response to both temperature and pressure. The introduction of CMC-Na improves the dispersion of the binary hybrid conductive fillers in the deionized water. Meanwhile, relying on the intermolecular forces of both hydrogen bonding and cation-π interaction, the interfacial interactions of the binary hybrid conductive fillers are strengthened, which is anticipated to create a stable and homogenous conductive layer. And the concept of “effective conductive fillers distribution density” is introduced to explain and analyze the pressure sensing mechanism. The reported sensor has a pressure sensitivity of −1.6189 %/kPa, a sensing range of 370 kPa, and a response recovery time of 37.5 ms/37.5 ms. In addition to its response to mechanical force, the sensor has a detecting range of 23–58 °C, a response recovery time of 325 ms/1000 ms, and a temperature coefficient of resistance (TCR) of −1.77 %/°C. The potential applications of this sensor demonstrate the excellent gesture tracking characteristics, multi-point tactile sensing capability, and dual stimulus–response of the sensor.

Ultrabroadband Absorbers and Bi-Functional Sensors for Water-Based Metamaterials

Ultrabroadband Absorbers and Bi-Functional Sensors for Water-Based Metamaterials

Spider silk-inspired supramolecular polydimethylsiloxane network with prominent mechanical robustness for bifunctional flexible electronics

Self-healing and recyclable polymer elastomers are being developed to provide new prospects in building sustainable societies. Nevertheless, the synthesis of such materials still poses a significant difficulty because of the conflicting requirements between the self-healing ability and mechanical robustness for the dynamicity of crosslinks. Herein, a self-healing and recyclable supramolecular polydimethylsiloxane with outstanding tensile stress and ultrahigh mechanical toughness is constructed by synergistically incorporating dynamic disulfide bonds and multiple hydrogen bonds into a siloxane chain. The adipic dihydrazide (AD) bearing two hydrazide groups is appropriate introduced to provide multiple hydrogen bonding sites between polymer chains and improve the mechanical robustness of the crosslinked structure. The aromatic disulfide bonds contribute to shorter healing time due to the elevated dynamicity of the crosslinked network. The resulting elastomers exhibit high tensile strength (6.44 ± 0.24 MPa), distinguished toughness (37.00 ± 0.85 MJ m−3), superior elastic restorability, outstanding self-healing capability (∼86 %) and multiple recyclability. Furthermore, a bifunctional sensor based on this elastomer is constructed to monitor human motions and pressure changes, demonstrating the potential application in flexible stretchable electronics.

A benzimidazole-appended double-armed salamo type fluorescence and colorimetric bifunctional sensor for identification of MnO4− and its applications in actual water samples

The symmetrically double-armed salamo type fluorescent sensor BMS, incorporating benzimidazole units, was designed and synthesized. Showcasing remarkable specificity and responsiveness to MnO4- within a DMSO:H2O (V/V = 9:1, pH = 7.2) Tris-HCl buffer medium, it enabled dual-channel detection of MnO4- through fluorescent and colorimetric changes. Critical experimental parameters, including detection and quantification thresholds (LOD and LOQ) along with binding affinity constants (Ka), were calculated using the Origin software. A rational interaction mechanism between BMS and MnO4- was deduced, based on fluorescence titration, Electrospray Ionization Mass Spectrometry (ESI-MS), Ultraviolet–Visible Spectroscopy (UV–Vis), Infrared Spectroscopy (IR), Stern-Volmer plots, and Density Functional Theory (DFT) computations. Additionally, the sensor BMS was applied to monitor MnO4- in real water samples. Advancing its practical utility, BMS was fabricated into test strips for the selective detecting of MnO4-.

High-temperature flexible electric Piezo/pyroelectric bifunctional sensor with excellent output performance based on thermal-cyclized electrospun PAN/Zn(Ac)2 nanofiber mat

High-temperature sensors are critical in petrochemical, aerospace, and automotive industries. However, the inorganic piezoelectric materials for high-temperature sensors are usually rigid and only can work in low temperatures due to their low Curie temperature (< 200 °C), which restricts these sensors for high-temperature application. Herein, we report a high-temperature piezoelectric sensor based on PAN/Zn(Ac)2 composite nanofiber mat created via electrospinning and thermal-oxidative stabilization process, which can continuously work over 500 °C. Moreover, the heat-treatment PAN is first found to be pyroelectric. The effects of the different heat-treatment temperatures on the mechanical and electrical performance of PAN/Zn(Ac)2 composite nanofiber mats are studied systematically. The maximum voltage output of the PAN/Zn(Ac)2 composite film sensor is 14.13 V at room temperature, and the voltage output of the composite film (450 ℃ heat-treated) sensor is about 14.86 V at high temperature. Besides, it has durability for over 10000 cycles (room temperature), and it has durability for over 5000 cycles and stability after 60 days (400 ℃). The PAN/Zn(Ac)2 composite nanofiber film also showed a linear voltage response to the thermal gradient, but the pyroelectric output of the PAN/Zn(Ac)2 composite nanofiber film is independent of the heat treatment temperature. The PAN/Zn(Ac)2 composite film sensor can charge a capacitor and can instantly drive small electronic devices when the capacitor discharges, and the PAN/Zn(Ac)2 composite film sensor can be applied to fire safety. Overall, good flexibility, high-temperature resistance, and bifunctional sensing ability make PAN/Zn(Ac)2-type sensors expected to be widely used in the high-temperature field of fire safety, the automotive industry, and other harsh environment.

A carbon nanotube metamaterial sensor showing slow light properties based on double plasmon-induced transparency.

In this study, we proposed a bifunctional sensor of high sensitivity and slow light based on carbon nanotubes (CNTs). An array of left semicircular ring (LSR), right semicircular ring (RSR), and circular ring (CR) resonators are utilized to form the proposed metamaterial. The proposed structure can achieve double plasmon-induced transparency (PIT) effects under the excitation of a TM-polarization wave. The double PIT originated from the destructive interference between two bright modes and a dark mode. A coupled harmonic oscillator model is used to describe the destructive interference between the two bright modes and a dark mode, and the simulation results agree well with the calculated results. Moreover, we investigate the influence of the coupling distance, period, and flare angle on the PIT spectra. The relationship between the resonant frequencies, full width at half maximum (FWHM), amplitudes, quality factors (Q), and the coupling distance is also studied. Finally, a high sensitivity of 1.02 THz RIU-1 is obtained, and the transmission performance can be maintained at a good level when the incident angle is less than 40°. Thus, the sensor can cope with situations where electromagnetic waves are not perpendicular to the structure's surface. The maximum figure of merit (FOM) can reach about 8.26 RIU-1; to verify the slow light property of the device, the slow light performance of the proposed structure is investigated, and a maximum time delay (TD) of 22.26 ps is obtained. The proposed CNT-based metamaterial can be used in electromagnetically induced transparency applications, such as sensors, optical memory devices, and flexible terahertz functional devices.

L-Alanine Supported Autogenous Eruption Combustion Synthesis of Ni/NiO@RuO2 Heterostructure for Electrochemical Glucose and pH Sensor

Safety and quality control are important for long-term storage and preservation of food. Glucose and food pH are the two most common markers for evaluating food quality. Herein, we constructed a Ni/NiO@RuO2 heterostructure-based two-way sensor via a novel eruption combustion pattern (ECP) using non-conventional amino acid as a propellant. This approach has the unique points of interests of in situ doping of oxides and the formation of heterojunctions, providing well-developed pores and high surface areas to enhance the material performance. The Ni/NiO@RuO2 heterostructures have been tested as a bi-functional catalyst for glucose and pH sensing. The sensor exhibits a fast response time of <0.1 ± 0.02 s, a sensitivity of 641.95 ± 0.5 μA mM−1 cm−2 towards glucose with a 0.4 ± 0.08 μM detection limit and a linear response of 0.1 to 5 mM. As a pH sensor, it exhibits an acceptable sensitivity of −41.6 mV pH−1 with a response time of <50 s over a pH range of 2–12. Moreover, this bi-functional sensor based on Ni/NiO@RuO2 performs well when applied to a selection of beverage samples. This study provides a new scalable and low-cost approach to fabricating hetero-oxide nanostructures with controllable heterojunctions for various sensor applications.

Flexible PANI/Lotus Stemmed Fiber Sensor for Bifunctional Sensing of Physical and Chemical Stimuli

AbstractIn recent times, high‐performance flexible sensors that can be fabricated environmentally friendly and low‐costly have received considerable attention owing to their potential applications in wearable health monitoring. The combination of biocompatibility, degradability, and recyclability between the substrate and sensor layer remains a challenge. Here, a highly sensitive multifunctional sensor is developed using a polyaniline (PANI)‐coated lotus stem fabric (PANI/LSF) for body physical and chemical stimuli in a simple way. The lotus stem fabric has excellent breathability, skin compatibility, and lightweight as a flexible substrate. Its high sensitivity at low pressure is experimentally verified, which can reach 0.3 kPa−1 in the 0–1.5 kPa range. In addition, the sensor has low detection limitation and good linearity of response to water molecules and short response and recovery times for water in N2 or normal atmosphere at the range of 3.7–70.5% relative humidity (RH) and 19.6–66.8% RH, respectively. This can be successfully used in the recognition of various breathing behaviors. Therefore, the study has developed a breathable and skin‐friendly bifunctional sensor based on PANI and natural fabrics, which has great potential for application in human health care.

Photoluminescent Copper Nanoclusters in “Turn-Off/Turn-On” Sensing of Picric Acid/Hydrogen Peroxide

In this paper, we illustrate the synthesis, characterization, and application of a Bovine Serum Albumin-stabilized copper nanocluster (BSA@CuNCs)-based photoluminescence (PL) bifunctional sensor for the selective and rapid sensing of picric acid (PA) and hydrogen peroxide (H2O2). Blue-emitting copper nanoclusters were synthesized using one-pot synthesis at room temperature. The PL intensity of BSA@CuNCs was shown to be quenched (“Turn-off”) with an increase in the concentration of PA and intensified (“Turn-on”) with the addition of H2O2. The quenching of PL intensity of BSA@CuNCs was shown to be extremely selective and rapid towards PA. A linear decrease in the PL emission intensity of BSA@CuNCs was observed with a PA concentration in the range of 0–15 μM. An extremely low detection limit of 60 nM (3σ/k) was calculated. The as-prepared BSA@CuNCs also exhibited superior selectivity for PA detection in aqueous medium. The developed sensor was also utilized for the sensing of PA in natural water samples. The probe was found to be extremely sensitive towards the detection of H2O2. An increase in the PL intensity of BSA@CuNCs was seen with the addition of H2O2, with a detection limit of 0.11 μM.

A Light/Pressure Bifunctional Electronic Skin Based on a Bilayer Structure of PEDOT:PSS-Coated Cellulose Paper/CsPbBr3 QDs Film.

With the continuous development of electronic skin (e-skin), multifunctional e-skin is approaching, and in some cases even surpassing, the capabilities of real human skin, which has garnered increasing attention. Especially, if e-skin processes eye's function, it will endow e-skins more powerful advantages, such as the vision reparation, enhanced security, improved adaptability and enhanced interactivity. Here, we first study the photodetector based on CsPbBr3 quantum dots film and the pressure sensor based on PEDOT: PSS-coated cellulose paper, respectively. On the base of these two kinds of sensors, a light/pressure bifunctional sensor was successfully fabricated. Finally, flexible bifunctional sensors were obtained by using a flexible interdigital electrode. They can simultaneously detect light and pressure stimulation. As e-skin, a high photosensitivity with a switching ratio of 168 under 405 nm light at a power of 40 mW/cm2 was obtained and they can also monitor human motions in the meantime. Our work showed that the strategy to introduce perovskite photodetectors into e-skins is feasible and may open a new way for the development of flexible multi-functional e-skin.

Mechanically robust and recyclable siloxane elastomers enabled by adjustable dynamic polymer networks for electronic skin

Siloxane elastomers as substrate materials have recently attracted much interest in the applications of flexible electronics. Nevertheless, excellent mechanical properties, self-healing properties and recyclability can rarely be satisfied with single material simultaneously. In this study, multistrength hydrogen bonds and dynamic disulfide bonds were introduced into the siloxane to achieve high stretchability, good mechanical strength, comparative self-healing capacity and excellent recyclability. By adjusting the ratio of the two types of hydrogen bonding networks, the prepared elastomers exhibit tunable mechanical properties, stretchability, toughness and a coordinated self-healing efficiency of 25–80%. Benefiting from the aromatic disulfide, the siloxane elastomer exhibits significant improvement in tensile strength of ∼4.67 MPa, tensile strain of ∼1086% and toughness of ∼27.36 MJ m−3 with 75% healing efficiency. Furthermore, a self-healing flexible bifunctional sensor was constructed by encapsulating liquid metal alloy between the elastomers layers to detect the pressure and multiple human motions.

Selective and quantitative recovery of sulfadiazine from seawater by Sb doped LTA zeolite electrochemical sensor

The sensitive Sb probe has been anchored in the LTA (Linde Type A) zeolite to form a bifunctional sensor for the electrochemical detection and recycling of sulfadiazine (SDZ) in seawater. Under Amperometric i-t Curve (A i-t C) method, SDZ is quantitatively adsorbed on the Sb LTA zeolite electrode from seawater by adjusting the reduction time and potential. Under differential pulse voltammetry (DPV) method, a characteristic peak is observed at ca. 0.80 V whose intensity can indicate the SDZ concentration on the novel modified electrode. Also, SDZ can be selectively released to phosphate-buffered saline (PBS) in the potential range of 0.80–0.95 V. The electrochemical mechanism of the reversible recovery reaction is carefully studied by the cyclic voltammetry (CV) method and confirmed by the X-ray Photoelectron Spectroscopy (XPS) analysis results related to the interaction between the electrode material and SDZ before and after electrochemical process. Sb doped on LTA zeolite presented a cubic phase from SEM images, and there are some SDZ particles accumulated and adsorbed on the surface of the crystal from TEM images. Theoretical calculation results reveal that SDZ is stable in the electrochemical adsorption and desorption process due to the interaction between the SDZ molecules and the 8-ring opening windows of LTA zeolite framework. The transfer efficiency of SDZ could reach 9.62 μg / 100 s or 0.430 g / 1 g based on the mass of Sb probe. The multifunctional sensor suggests a novel strategy for the electrochemically controlled detection and recovery toward antibiotic sulfadiazine.

Four octamolybdate compounds with properties of organic dye adsorption and photocatalytic reduction of Cr(VI).

Hydrothermal synthesis was used to create four different POM-based compounds, namely {[Co(Hptpm)2(β-Mo8O26)0.5(ξ-Mo8O26)0.5]}·H2O (1), [Co(Hptpm)2(δ-Mo8O26)]·H2O (2), [Co(Hptpm)2(β-Mo8O26)] (3) and [Zn(Hptpm)2(β-Mo8O26)] (4) (ptpm = 4-[3-(3-pyridine-2-yl-[1,2,4]triazol-4-yl)-propyl]-morpholine). 1-4 containing different octamolybdate isomers were characterized. Compounds 1-4 showed good electrochemical performance and can be utilized as bifunctional sensors for NO2-, H2O2, Cr(VI) and Fe(III). Taking compound 1 as an example, the detection limits are 0.081 μM for NO2-, 0.072 μM for H2O2, 0.054 μM for Cr(VI) and 0.063 μM for Fe(III), respectively. Compounds 1-4 have good capacitance. Moreover, compounds 1-4 also show good adsorption properties for organic cationic dyes. The cationic dyes include methylene blue (MB), crystal violet (CV) and neutral red (NR). In addition, 1-4 have excellent characteristics that can reduce Cr(VI) to Cr(III) by photocatalytic technology. Within 30 min, the reduction rates were 95.85% for 1, 93.99% for 2, 90.29% for 3 and 88.18% for 4.

Water-stable nickel-based coordination polymer for selective and sensitive enhancing and quenching fluorescence sensing of ascorbic acid and acetylacetone

The novel Ni-based coordination polymer [Ni(H2edda) (bpe)] (CP 1) was successfully synthesized by employing 5,5′ (ethane-1,2-diylbis(oxy)) diisophthalic acid (H4edda) and 1,2-bis (4-pyridyl) ethylene (bpe) under hydrothermal conditions. Structural analysis indicates that CP 1 presents a 2-fold-interpenetrated two-dimensional (2 D) framework with a uninodal sql topology. Further investigation reveals that the newly obtained CP can be stable in water or even exposed in a certain acid/base aqueous solution (pH = 3–11) for a long period of time. Remarkably, CP 1 can further serve as a bifunctional sensor for ascorbic acid (AA) and acetylacetone (acac) in aqueous media according to fluorescence enhancing and quenching effects, respectively. Notably, both sensing processes are labeled with exceptional anti-interference property, high sensitivity and selectivity, wide linear range (0–50 μM for AA and 0.2–1.8 mM for acac) and low detection limit (1.37 nM for AA and 1.58 μM for acac). Theoretical simulations and experimental findings point out that in the process of AA detection by CP 1, the significant fluorescence enhancement could be caused by the photo-induced electron transfer (PET) process, while the inner filter effect (IFE) mechanism combined with PET should be responsible for the fluorescence quenching of CP 1 by acac.

Tetraphenylethene-Based Fluorescent Chemosensor with Mechanochromic and Aggregation-Induced Emission (AIE) Properties for the Selective and Sensitive Detection of Hg2+ and Ag+ Ions in Aqueous Media: Application to Environmental Analysis.

It is critical to design a novel and simple bifunctional sensor for the selective and sensitive detection of ions in an aqueous media in environmental samples. As a result, in this study, tetraphenylethene hydrazinecarbothioamide (TPE-PVA), known as probe 1, was successfully synthesized and characterized as having impressive photophysical phenomena such as aggregation-induced emission (AIE) and mechanochromic properties by applying mechanical force to the solid of probe 1. The emission of the solid of probe 1 changed from turquoise blue to lemon yellow after grinding, from lemon yellow to parakeet green after annealing at 160 °C, and to arctic blue after fuming with DCM. Such characteristics could lead to a variety of applications in several fields. The probe was implemented and demonstrated remarkable selectivity and sensitivity toward mercury(II) and silver(I) ions by substantially switching off emission over other cations. Following an extensive photophysical analysis, it was discovered that detection limits (LOD) as low as 0.18344 and 0.2384 μg mL–1 for Hg2+ and Ag+, respectively, are possible with a quantum yield (Φ) of 2.26. Probe 1 was also explored as a Hg2+ and Ag+ paper strip-based sensor and kit for practical use. The binding mechanisms of probe 1 (TPE-PVA) with Hg2+ and Ag+ were confirmed by 1H NMR titration. These results could lead to the development of reliable onsite Hg2+ and Ag+ fluorescent probes in the future.

Printable, flexible, breathable and sweatproof bifunctional sensors based on an all-nanofiber platform for fully decoupled pressure–temperature sensing application

Flexible bifunctional sensors that mimic the function of human skin are essential as they provide critical interacting information with human and environment for intelligentization. However, the problem of the interference between sensing signals from different stimuli and the deficiency of comfortability for a long-time skin-attaching wearing still exist. Herein, we present an ultrathin and flexible bifunctional sensor based on two measurable parameters of pressure-induced supercapacitance and temperature-induced resistance with neglectable crosstalk between the two. The sensor consists of a planar iontronic supercapacitor underneath a serpentine resistor with assembly of total seven layers integrated on an electrospun thermoplastic polyurethane (TPU)-based nanofiber platform. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-based sensing electrodes are patterned by a direct ink writing method with addition of graphene nanoflakes and Co3O4 nanoparticles to enhance the sensing performance. A high pressure sensitivity (147.19 kPa−1, 0–7 kPa; 4.41 kPa−1, 25–85 kPa) and a high temperature sensitivity (0.040 °C−1, 25–50 °C; 0.002 °C−1, 50–100 °C) are simultaneously achieved. The sensor also has the advantages of humidity inertness, waterproof ability and air permeability, which is breathable to obtain a wearing comfortability. Decoupled pressure–temperature sensing applications of detecting various subtle pressures by objects of different temperatures are demonstrated in a wireless and real-time mode. The proposed bifunctional sensor shows great potential in wearable healthcare monitoring.

Bifunctional Sensors Based on Phosphomolybdates for Detection of Inorganic Hexavalent Chromium and Organic Tetracycline.

Exploring effective sensors for detecting possible hazards in a water system are greatly significant. This work proposed a strategy for stable and effective bifunctional sensors via incorporating hourglass-type phosphomolybdates into metal-organic fragments to construct a high-dimensional framework. Two hourglass-type phosphomolybdate-based electrochemical sensors toward heavy metal ion Cr(VI) and tetracycline (TC) detection were designed with the formula [CoII2(H2O)4NaI2][CoII(Hbpe)][NaI(bpe)1.5]{CoII[PV4MoV6O31H6]2}·9H2O (1) and [CoII(H2O)4NaI3][CoII(Hbpe)][CoII(bpe)]{CoII[PV4MoV6O31H6]2}·9H2O (2) [bpe = 1,2-di(4-pyridyl)ethylene]. Structural analysis showed that hybrids 1 and 2 possess three-dimensional POM-supported network features with favorable stability and exhibit reversible redox properties. Experiments found that this kind of hybrids as efficient sensors have excellent electrochemical performance toward Cr(VI) detection with high sensitivities of 0.111 μA·μM-1 for 1 and 0.141 μA·μM-1 for 2, fast response time of 1 s, and low detection limits of 30 nM for 1 and 27 nM for 2, which far meet the standard of WHO for drinking water. Moreover, hybrids 1-2 also exhibit fast responses to TC detection with sensitivities of 0.0073 and 0.022 μA·mM-1 and detection limits of 0.426 and 0.084 mM. This work offers a novel strategy for the purposeful design of efficient POM-based electrochemical sensors for accurate determination of contaminants in a practical water system.

Electroactive and photoactive porphyrin-based covalent-organic framework for the construction of a bifunctional self-powered sensing platform toward real time analysis of nitride oxide from cancer cells

Sensitive and selective determination of nitrogen oxide (NO) from living cells is significant for early diagnosis of cancer. Herein, a novel bifunctional electrochemical (EC) and photoelectrochemical (PEC) sensing strategy for the in situ and sensitive analysis of NO released from cancer cells was constructed based on porphyrin-based covalent-organic framework (p-COF). Here, p-COF was synthesized using 4,4′,4′',4′''-(21H,23H-porphine-5,10,15,20-tetrayl) tetrakis-benzaldehyde (p-Por-CHO) and 2,2′-bipyridine-5,5′-diamine (bpy) as building blocks via the condensation polymerization method (denoted as p-bpy-COF). The p-bpy-COF nanospheres were assembled with multilayer nanosheets and possessed highly conjugated structure and abundant oxygen vacancy, affording remarkable visible-light adsorption, high electrochemical activity, and outstanding photoactivity property. The p-bpy-COF-based EC and self-powered PEC sensor showed low detection limits of 17.3 nM and 21.8 nM within 0.36–44.3 μM and 5–660 μM, respectively, outperforming to most of reported NO sensors. Moreover, the fabricated bifunctional sensor demonstrated high selectivity, excellent stability, good reproducibility, and accepted applicability for detecting NO from living cancer cells. This work can provide a new bifunctional sensing strategy for analysis of NO and broaden the application range of COF in biosensing fields.

Highly selective detection of Fe3+ and nitro explosives by a bifunctional sensor based on Cd(II) complex

A cadmium fluorescence framework [Cd(sip)(dpa)(H2O)] n (1) (NaH2sip = sodium 5-sulfoisophthalate; dpa = 4,4’-dipyridylamine) has been successfully synthesized and characterized. Single crystal X-ray diffraction analysis reveals that complex 1 exhibits an infinite 1D double chain, the H-bonds extend the 1D chains into a 3D supermolecular framework. Fluorescent studies reveal that 1 can be used as a highly sensitive luminescent sensor for detecting Fe3+ ion in H2O and 4-nitrophenol (4-NP) in DMF within a few seconds through fluorescence quenching. The sensing mechanism for Fe3+ can be explained in terms of synergistic competitive absorption and coordination interactions between Fe3+ and the framework, while the mechanism for detecting 4-NP is mainly attributed to the competitive absorption between the excitation/emission of 1 and analytes.

Silver nanosheets doped polyvinyl alcohol hydrogel piezoresistive bifunctional sensor with a wide range and high resolution for human motion detection

Silver nanosheets doped polyvinyl alcohol hydrogel piezoresistive bifunctional sensor with a wide range and high resolution for human motion detection