Development of a Biomimetic Semicircular Canal with MEMS Sensors to Restore Balance
Approximately one-third of adults aged 50 and above experience ongoing issues with their balance, posture, and gaze stability. These problems stem from damage to the inner ear's sensory cells responsible for these functions. The consequences of this balance impairment include dizziness, withdrawal from social activities, and an acceleration of overall functional decline.
Despite advancements in biomedical sensing technology, current artificial vestibular systems have limitations in practical scenarios and at low frequencies. That's why we've introduced an innovative biomechanical device designed to closely replicate the human vestibular system. We've developed a microelectromechanical systems (MEMS) flow sensor that mimics the function of vestibular hair cell sensors. This sensor is integrated into a three-dimensional (3D) printed semicircular canal and tested across a range of angular accelerations, spanning from 0.5Hz to 1.5Hz.
This miniaturized device, when embedded into a 3D printed model, can detect mechanical movements, and effectively restore the sense of balance in individuals with vestibular dysfunction. Our experimental and simulation studies of the semicircular canal, as presented here, lay the foundation for the development of a sensory system for balance. This could potentially lead to the creation of an affordable and commercially viable medical device with significant health benefits and economic potential.
Development of an Ultra‑Sensitive and Flexible Piezoresistive Flow Sensor Using Vertical Graphene Nanosheets
This paper proposes the creation of a flexible, lightweight, and extremely sensitive piezoresistive flow sensor utilizing vertical graphene nanosheets (VGNs) with a maze-like structure. The sensor underwent comprehensive testing for monitoring steady-state and oscillatory water flows, revealing impressive results, including a high sensitivity of 103.91 mV (mm/s)−1 and an exceptionally low velocity detection threshold of 1.127 mm s−1 during steady-state flow monitoring.
One noteworthy application demonstrated in this study involves the potential of the VGNs/PDMS flow sensor to emulate the functionality of vestibular hair cell sensors found in the semicircular canals (SCCs) of the human inner ear. To validate this concept, magnetic resonance imaging was employed to measure the dimensions of the SCCs, leading to the development of a 3D printed lateral semicircular canal (LSCC). The flow sensor was then integrated into this artificial LSCC and subjected to various physiological movements.
The results obtained from these tests revealed that the flow sensor is capable of discerning subtle alterations in the physical geometry, frequency, and amplitude of rotational axis movements. The success of this study opens the door for the expansion of this technology, not only in the field of vestibular organ prosthesis but also in other diverse applications such as monitoring blood and urine flow, intravenous therapy (IV), detecting water leaks, and enhancing unmanned underwater robots through the appropriate device packaging.
Other applications of VGNs/PDMS flow sensors to monitor respiratory patterns
The monitoring of human respiratory patterns holds significant importance as it provides critical information for various medical conditions such as sleep apnea syndrome, chronic obstructive pulmonary disease, and asthma, among others. In this study, we have developed an airflow sensor made from a polymeric nanocomposite consisting of vertically grown graphene nanosheets (VGNs) and polydimethylsiloxane (PDMS). We have explored the applications of this sensor in monitoring human respiration.
The performance of the VGNs/PDMS nanocomposite sensor was assessed by subjecting it to a range of airflow rates spanning from 20 to 130 liters per minute. The results demonstrated a linear response with high sensitivity and a rapid response time, typically below 1 second. To validate the experimental findings, we employed finite-element simulation models using the COMSOL Multiphysics package. These simulations delved into the piezoresistive properties of the VGNs/PDMS thin film and examined fluid-solid interaction in detail. Laser Doppler vibrometry measurements of sensor tip displacement closely aligned with simulated deflection results, confirming the dynamic responsiveness of the sensor.
Upon comparing our proposed sensor with other airflow sensors reported in the literature, it becomes evident that the VGNs/PDMS airflow sensor boasts several excellent features, including its compact size, wide detection range, and high sensitivity. Furthermore, we have demonstrated the potential application of the VGNs/PDMS airflow sensor in monitoring the respiration patterns of individuals engaged in physical activities such as walking, jogging, and running.
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Biomimetic Ultra flexible Piezoresistive Flow Sensor Based on Graphene Nanosheets and PVA Hydrogel
Flow sensors are crucial for monitoring various flow parameters like rate, velocity, direction, and rotation frequency. In this study, we draw inspiration from the biological hair cells found in the human vestibular system to create an innovative flow sensor. Our sensor is constructed using polyvinyl alcohol (PVA) hydrogel nanocomposites featuring a labyrinthine network of vertically oriented graphene nanosheets (VGNs).
When submerged in water, the VGNs/PVA hydrogel absorbs a significant amount of water, endowing the sensor with exceptional sensitivity to minute underwater stimuli. The sensor exhibits remarkable characteristics, including high sensitivity at 5.755 mV (mm s−1)−1 and an incredibly low velocity detection threshold of 0.022 mm s−1. Additionally, it performs exceptionally well in detecting low-frequency oscillatory flows down to 0.1 Hz, rendering it suitable for various biomedical applications.
One of the promising applications of this sensor involves its ability to closely mimic the physiological behavior of vestibular hair cells under different conditions. To elucidate the experimental findings, we have developed a comprehensive finite element simulation to model the piezoresistive effect of the VGNs/PVA thin film structure.
This pioneering work represents the first endeavor to create flow sensors based on hydrogel-graphene nanosheets, resulting in a sensor that closely resembles natural vestibular hair cells. This miniaturized hair cell sensor marks a significant step towards harnessing hydrogels to develop the next generation of ultra-sensitive flow sensors tailored for biomedical applications.
Flow sensors are crucial for monitoring various flow parameters like rate, velocity, direction, and rotation frequency. In this study, we draw inspiration from the biological hair cells found in the human vestibular system to create an innovative flow sensor. Our sensor is constructed using polyvinyl alcohol (PVA) hydrogel nanocomposites featuring a labyrinthine network of vertically oriented graphene nanosheets (VGNs).
When submerged in water, the VGNs/PVA hydrogel absorbs a significant amount of water, endowing the sensor with exceptional sensitivity to minute underwater stimuli. The sensor exhibits remarkable characteristics, including high sensitivity at 5.755 mV (mm s−1)−1 and an incredibly low velocity detection threshold of 0.022 mm s−1. Additionally, it performs exceptionally well in detecting low-frequency oscillatory flows down to 0.1 Hz, rendering it suitable for various biomedical applications.
One of the promising applications of this sensor involves its ability to closely mimic the physiological behavior of vestibular hair cells under different conditions. To elucidate the experimental findings, we have developed a comprehensive finite element simulation to model the piezoresistive effect of the VGNs/PVA thin film structure.
This pioneering work represents the first endeavor to create flow sensors based on hydrogel-graphene nanosheets, resulting in a sensor that closely resembles natural vestibular hair cells. This miniaturized hair cell sensor marks a significant step towards harnessing hydrogels to develop the next generation of ultra-sensitive flow sensors tailored for biomedical applications.
Development of Ultrasensitive Biomimetic Auditory Hair Cells Based on Piezoresistive Hydrogel Nanocomposites
As our population continues to age, the prevalence of hearing disorders is expected to increase significantly in the coming decades. Consequently, the development of a new generation of artificial auditory systems has emerged as an exciting and vital area of research in the field of biomedicine.
In this study, we introduce the design of a biocompatible piezoresistive-based artificial hair cell sensor. This sensor is composed of a highly flexible and conductive nanocomposite featuring polyvinyl alcohol (PVA) and vertically aligned graphene nanosheets (VGNs). Our bilayer hydrogel sensor exhibits outstanding performance in emulating the characteristics of biological hair cells, effectively responding to acoustic stimuli within the audible frequency range of 60 Hz to 20 kHz.
The sensor's output remains stable within the mid-frequency range (∼4−9 kHz) and exhibits its highest sensitivity at high frequencies (∼13−20 kHz). This behavior bears a resemblance to the mammalian auditory system, which possesses remarkable sensitivity and precise tuning at high frequencies thanks to an "active process." This study validates the PVA/VGN sensor's potential to fulfill a similar functional role as cochlear hair cells, which also operate across a wide frequency spectrum in a fluid medium.
Further investigations of the sensor reveal that increasing sound amplitude results in heightened sensor responses, while submerging it in water reduces sensor outputs due to sound attenuation in the liquid environment. Additionally, we conducted finite element analysis to predict the acoustic pressure distribution of sound waves, with our numerical findings aligning perfectly with experimental data.
This proof-of-concept research serves as a foundation for the future development of sensitive and flexible biomimetic sensors, closely mirroring the biological cochlea, and holds promise for advancements in the field of artificial auditory systems.
As our population continues to age, the prevalence of hearing disorders is expected to increase significantly in the coming decades. Consequently, the development of a new generation of artificial auditory systems has emerged as an exciting and vital area of research in the field of biomedicine.
In this study, we introduce the design of a biocompatible piezoresistive-based artificial hair cell sensor. This sensor is composed of a highly flexible and conductive nanocomposite featuring polyvinyl alcohol (PVA) and vertically aligned graphene nanosheets (VGNs). Our bilayer hydrogel sensor exhibits outstanding performance in emulating the characteristics of biological hair cells, effectively responding to acoustic stimuli within the audible frequency range of 60 Hz to 20 kHz.
The sensor's output remains stable within the mid-frequency range (∼4−9 kHz) and exhibits its highest sensitivity at high frequencies (∼13−20 kHz). This behavior bears a resemblance to the mammalian auditory system, which possesses remarkable sensitivity and precise tuning at high frequencies thanks to an "active process." This study validates the PVA/VGN sensor's potential to fulfill a similar functional role as cochlear hair cells, which also operate across a wide frequency spectrum in a fluid medium.
Further investigations of the sensor reveal that increasing sound amplitude results in heightened sensor responses, while submerging it in water reduces sensor outputs due to sound attenuation in the liquid environment. Additionally, we conducted finite element analysis to predict the acoustic pressure distribution of sound waves, with our numerical findings aligning perfectly with experimental data.
This proof-of-concept research serves as a foundation for the future development of sensitive and flexible biomimetic sensors, closely mirroring the biological cochlea, and holds promise for advancements in the field of artificial auditory systems.
Using Miniaturized Strain Sensors to Provide a Sense of Touch in a Humanoid Robotic Arm
Recent advancements in sensing technology have ushered in a new era of lighter and more compact control systems, particularly in the realm of prosthetics and biomedical applications. In this study, we present a sensory system inspired by biology, designed for a master-slave force-sensing robotic hand. This innovative system enables precise control and imparts a natural sense of touch to humanoid robotic hands by utilizing force information obtained from a smart glove equipped with force sensing resistors.
The slave robotic hand is created through three-dimensional (3D) printing technology, and it is driven by servo motors that control its various components. The master robotic hand, on the other hand, is represented by a glove adorned with miniaturized flexible sensors. This glove serves as the master controller, providing both movement and force signals that the slave robotic hand replicates. The force signals from the sensors play a crucial role in regulating the motion of the slave hand's fingers, enabling it to handle delicate objects with precision and without the risk of causing damage.
Our research demonstrates the practicality and versatility of this approach in enhancing robotic manipulation. With careful sensor selection and tuning, we have achieved the capability to track applied force from the master hand with remarkable accuracy, reaching within 0.1 Newtons. The success of this methodology sets the stage for the development of innovative control systems that employ cost-effective, bio-inspired strain and force sensors, with potential applications in prosthetics and related fields.
Biocompatible and Highly Stretchable PVA/AgNWs Hydrogel Strain Sensors for Human Motion Detection
Hydrogel-based strain sensors have garnered significant attention for various applications, including skin-like electronics for human motion detection, soft robotics, and human-machine interfaces. However, the challenge has persisted in creating hydrogel strain sensors with the desired mechanical and piezoresistive properties. In this study, we introduce a biocompatible hydrogel sensor composed of a polyvinyl alcohol (PVA) nanocomposite. This sensor exhibits remarkable attributes, including high stretchability, reaching up to 500% strain, substantial mechanical strength of 900 kPa, and electrical conductivity of 1.85 S m-1, which is comparable to that of human skin.
These hydrogel sensors demonstrate exceptional linearity across their entire detection range and exhibit remarkable durability under cyclic loading, characterized by low hysteresis of just 7%. These outstanding properties are attributed to a novel bilayer structural design. The sensor consists of a thin, conductive hybrid layer composed of PVA and silver nanowires (AgNWs), which is deposited on a pure, robust PVA substrate. The substrate is created using a highly concentrated PVA solution, while the top layer employs a diluted PVA solution to facilitate the dispersion of a high content of AgNWs, thereby achieving remarkable electrical conductivity.
In addition to its rapid response time of 0.32 seconds, biocompatibility, and exceptional mechanical properties, this novel sensor holds immense potential for use as a wearable sensor in epidermal sensing applications. For example, it can be employed to detect human joint and muscle movements with precision and reliability.
Hydrogel-based strain sensors have garnered significant attention for various applications, including skin-like electronics for human motion detection, soft robotics, and human-machine interfaces. However, the challenge has persisted in creating hydrogel strain sensors with the desired mechanical and piezoresistive properties. In this study, we introduce a biocompatible hydrogel sensor composed of a polyvinyl alcohol (PVA) nanocomposite. This sensor exhibits remarkable attributes, including high stretchability, reaching up to 500% strain, substantial mechanical strength of 900 kPa, and electrical conductivity of 1.85 S m-1, which is comparable to that of human skin.
These hydrogel sensors demonstrate exceptional linearity across their entire detection range and exhibit remarkable durability under cyclic loading, characterized by low hysteresis of just 7%. These outstanding properties are attributed to a novel bilayer structural design. The sensor consists of a thin, conductive hybrid layer composed of PVA and silver nanowires (AgNWs), which is deposited on a pure, robust PVA substrate. The substrate is created using a highly concentrated PVA solution, while the top layer employs a diluted PVA solution to facilitate the dispersion of a high content of AgNWs, thereby achieving remarkable electrical conductivity.
In addition to its rapid response time of 0.32 seconds, biocompatibility, and exceptional mechanical properties, this novel sensor holds immense potential for use as a wearable sensor in epidermal sensing applications. For example, it can be employed to detect human joint and muscle movements with precision and reliability.
Carbon nanofiber-reinforced Pt thin film-based airflow sensor for respiratory monitoring
Detecting abnormal respiratory patterns is crucial for identifying emergency signs and diagnosing diseases or dysfunctions. In this paper, we propose the design and creation of an innovative airflow sensor constructed from platinum (Pt) thin films reinforced with carbon nanofibers (CNFs). These conductive Pt thin films are supported by polydimethylsiloxane (PDMS), providing the sensors with exceptional flexibility and ultra-high sensitivity. The CNFs serve as bridges that deflect microcracks forming in the Pt thin film when subjected to external stress, thereby enhancing piezoresistive properties.
The Pi-shaped airflow sensor was subjected to various airflow rates to evaluate its performance, including sensitivity, response time, and recovery time. The results demonstrate that the sensor exhibits high sensitivity (27.6 mV (m/s)-1), a low response time (greater than 0.6 s), and a low-velocity threshold of 15 L min-1 or 0.83 m/s. To gain insights into its functionality, we developed a finite-element model using the COMSOL Multiphysics package, allowing us to study fluid-solid interactions and piezoresistive effects in the Pt-CNFs/PDMS nanocomposite. We also quantified sensor tip displacement through direct measurements using single-point laser Doppler vibrometry, comparing the results to numerical simulations. The calibration plot and numerical findings are in excellent agreement.
When compared to previous studies, our airflow sensor demonstrates superior sensing performance in terms of sensor length, sensitivity, and velocity threshold under various experimental conditions. As a proof of concept, we tested the airflow sensor's capability to monitor human respiratory patterns in two extreme conditions: sitting and running. This research holds promise for applications in healthcare and monitoring systems where precise and responsive airflow sensing is essential.
Detecting abnormal respiratory patterns is crucial for identifying emergency signs and diagnosing diseases or dysfunctions. In this paper, we propose the design and creation of an innovative airflow sensor constructed from platinum (Pt) thin films reinforced with carbon nanofibers (CNFs). These conductive Pt thin films are supported by polydimethylsiloxane (PDMS), providing the sensors with exceptional flexibility and ultra-high sensitivity. The CNFs serve as bridges that deflect microcracks forming in the Pt thin film when subjected to external stress, thereby enhancing piezoresistive properties.
The Pi-shaped airflow sensor was subjected to various airflow rates to evaluate its performance, including sensitivity, response time, and recovery time. The results demonstrate that the sensor exhibits high sensitivity (27.6 mV (m/s)-1), a low response time (greater than 0.6 s), and a low-velocity threshold of 15 L min-1 or 0.83 m/s. To gain insights into its functionality, we developed a finite-element model using the COMSOL Multiphysics package, allowing us to study fluid-solid interactions and piezoresistive effects in the Pt-CNFs/PDMS nanocomposite. We also quantified sensor tip displacement through direct measurements using single-point laser Doppler vibrometry, comparing the results to numerical simulations. The calibration plot and numerical findings are in excellent agreement.
When compared to previous studies, our airflow sensor demonstrates superior sensing performance in terms of sensor length, sensitivity, and velocity threshold under various experimental conditions. As a proof of concept, we tested the airflow sensor's capability to monitor human respiratory patterns in two extreme conditions: sitting and running. This research holds promise for applications in healthcare and monitoring systems where precise and responsive airflow sensing is essential.
Highly stretchable strain sensors based on gold thin film reinforced with carbon nanofibers
Flexible piezoresistive sensors are commonly created by applying a conductive layer, which can consist of materials like platinum, gold, graphene thin films, or conductive nanoparticles, onto a stretchable substrate. However, because these conductive materials tend to be brittle, this approach often results in sensors with limited stretchability. In this context, we present an innovative technique that significantly enhances the stretchability of piezoresistive strain sensors based on gold (Au) thin films. We achieve this by combining them with carbon nanofibers (CNFs).
Sensors relying solely on Au thin films experience electrical failure at a very low strain level, approximately 4.5%. In contrast, sensors using hybridized Au-CNFs thin films exhibit a substantially increased failure strain of approximately 225%. The introduction of one-dimensional CNFs serves to widen the range of workable strain by bridging and redirecting the microcracks that develop in the Au thin film during stretching. This effectively prevents the formation of long, channel-like straight cracks, which can lead to electrical failure at low strains.
These high-performance sensors hold significant promise for applications as wearable sensors for motion detection, such as monitoring joint bending. Furthermore, the sensors have demonstrated their potential in detecting airflow levels similar to human respiratory patterns.
Flexible piezoresistive sensors are commonly created by applying a conductive layer, which can consist of materials like platinum, gold, graphene thin films, or conductive nanoparticles, onto a stretchable substrate. However, because these conductive materials tend to be brittle, this approach often results in sensors with limited stretchability. In this context, we present an innovative technique that significantly enhances the stretchability of piezoresistive strain sensors based on gold (Au) thin films. We achieve this by combining them with carbon nanofibers (CNFs).
Sensors relying solely on Au thin films experience electrical failure at a very low strain level, approximately 4.5%. In contrast, sensors using hybridized Au-CNFs thin films exhibit a substantially increased failure strain of approximately 225%. The introduction of one-dimensional CNFs serves to widen the range of workable strain by bridging and redirecting the microcracks that develop in the Au thin film during stretching. This effectively prevents the formation of long, channel-like straight cracks, which can lead to electrical failure at low strains.
These high-performance sensors hold significant promise for applications as wearable sensors for motion detection, such as monitoring joint bending. Furthermore, the sensors have demonstrated their potential in detecting airflow levels similar to human respiratory patterns.
Multilayered Electrospun/Electrosprayed Polyvinylidene Fluoride+Zinc Oxide Nanofiber Mats with Enhanced Piezoelectricity
Electrospun nanofibers made from polyvinylidene fluoride (PVDF) are widely used in the creation of flexible piezoelectric sensors and nanogenerators, thanks to their impressive mechanical properties. However, a persistent challenge has been their relatively low piezoelectricity. In this study, we present a novel and effective approach to boost the piezoelectricity of PVDF nanofiber mats by introducing zinc oxide (ZnO) nanoparticles through electro-spraying between layers of PVDF nanofibers.
In contrast to the conventional method of dispersing ZnO nanoparticles within the PVDF solution before electrospinning the nanofiber mats, this technique yields multilayered PVDF+ZnO nanofiber mats with a significantly enhanced piezoelectric response. For instance, when electro-spraying 100% of the ZnO quantity relative to PVDF between PVDF nanofibers, we achieve an output that is 6.2 times higher. Furthermore, this innovative method allows for a higher loading of ZnO without encountering processing challenges, resulting in a maximum peak voltage of approximately 3 V when the ZnO content is increased up to 150%. Additionally, we find that samples with equal amounts of material but varying numbers of layers exhibit no significant differences in performance.
This study underscores the effectiveness of the proposed multilayer design as an alternative strategy for enhancing the piezoelectric properties of PVDF nanofibers, with the potential for scalable mass production.
Electrospun nanofibers made from polyvinylidene fluoride (PVDF) are widely used in the creation of flexible piezoelectric sensors and nanogenerators, thanks to their impressive mechanical properties. However, a persistent challenge has been their relatively low piezoelectricity. In this study, we present a novel and effective approach to boost the piezoelectricity of PVDF nanofiber mats by introducing zinc oxide (ZnO) nanoparticles through electro-spraying between layers of PVDF nanofibers.
In contrast to the conventional method of dispersing ZnO nanoparticles within the PVDF solution before electrospinning the nanofiber mats, this technique yields multilayered PVDF+ZnO nanofiber mats with a significantly enhanced piezoelectric response. For instance, when electro-spraying 100% of the ZnO quantity relative to PVDF between PVDF nanofibers, we achieve an output that is 6.2 times higher. Furthermore, this innovative method allows for a higher loading of ZnO without encountering processing challenges, resulting in a maximum peak voltage of approximately 3 V when the ZnO content is increased up to 150%. Additionally, we find that samples with equal amounts of material but varying numbers of layers exhibit no significant differences in performance.
This study underscores the effectiveness of the proposed multilayer design as an alternative strategy for enhancing the piezoelectric properties of PVDF nanofibers, with the potential for scalable mass production.
Enhanced Piezoelectricity of PVDF-TrFE Nanofibers by Intercalating with Electro-sprayed BaTiO3
Over recent decades, there has been a growing interest in flexible piezoelectric devices, driven by their diverse applications in wearable sensors and energy harvesting. Among the various piezoelectric polymers, Poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) has garnered significant attention due to its exceptional flexibility, high thermal stability, and biocompatibility. However, its relatively modest piezoelectric properties have limited its widespread use. In this study, we introduce a novel method to enhance the piezoelectricity of PVDF-TrFE nanofibers by incorporating barium titanate (BTO) nanoparticles.
Rather than directly dispersing BTO nanoparticles within the PVDF-TrFE nanofibers, we electrospray them between the layers of nanofibers, creating a sandwich-like structure. Our findings reveal that the sample with BTO nanoparticles sandwiched between PVDF-TrFE nanofibers exhibits significantly greater piezoelectric output when compared to the sample with BTO uniformly distributed within the nanofibers, with a remarkable enhancement of approximately 457%. Simulation results suggest that this enhanced piezoelectricity is attributed to the larger strain induced in the BTO nanoparticles within the sandwich structure. Furthermore, the electrospraying process may facilitate better poling of BTO due to the higher field strength, which is also believed to contribute to the enhanced piezoelectricity.
We also demonstrate the potential of these piezoelectric nanofiber mats as sensors for measuring biting force and as a sensor array for pressure mapping.
Over recent decades, there has been a growing interest in flexible piezoelectric devices, driven by their diverse applications in wearable sensors and energy harvesting. Among the various piezoelectric polymers, Poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) has garnered significant attention due to its exceptional flexibility, high thermal stability, and biocompatibility. However, its relatively modest piezoelectric properties have limited its widespread use. In this study, we introduce a novel method to enhance the piezoelectricity of PVDF-TrFE nanofibers by incorporating barium titanate (BTO) nanoparticles.
Rather than directly dispersing BTO nanoparticles within the PVDF-TrFE nanofibers, we electrospray them between the layers of nanofibers, creating a sandwich-like structure. Our findings reveal that the sample with BTO nanoparticles sandwiched between PVDF-TrFE nanofibers exhibits significantly greater piezoelectric output when compared to the sample with BTO uniformly distributed within the nanofibers, with a remarkable enhancement of approximately 457%. Simulation results suggest that this enhanced piezoelectricity is attributed to the larger strain induced in the BTO nanoparticles within the sandwich structure. Furthermore, the electrospraying process may facilitate better poling of BTO due to the higher field strength, which is also believed to contribute to the enhanced piezoelectricity.
We also demonstrate the potential of these piezoelectric nanofiber mats as sensors for measuring biting force and as a sensor array for pressure mapping.
A miniaturized piezoresistive flow sensor for real‐time monitoring of intravenous infusion
Drug overdose (DO) is considered one of the current issues of intravenous (IV) infusion particularly resulting in serious injuries and deaths. Malfunction of infusion pumps is reported as the main cause of the drug overdose. Live monitoring and flow rate calculation by health professionals have been practicing to avoid DO. However, human errors and miscalculations are inevitable. A secondary measurement tool is required to avoid the risk of OD when infusion pump malfunctions cannot be detected immediately. Here, inspired by nature, we developed a real‐time monitoring device through which an administrator can review, evaluate, and modify the IV infusion process. Our flow sensor possesses an erected polymer hair cell on a multi‐layered silicon base forming from a patterned gold strained gauge layer on a piezoresistive liquid crystal polymer (LCP) membrane. Gold strain gauges on an LCP membrane have been used instead of a piezoresistive silicon membrane as the sensing element. The combination of gold strain gauges and LCP membrane provides better sensitivity than a piezoresistive silicon membrane of the same dimensions and thickness. We also miniaturized our biocompatible sensor such that it can be possible to install it inside the IV tube in contact with the liquid providing an in‐suite online flow monitoring. The proposed LCP membrane sensor is compared with two commercially available IV sensors to validate its flow sensing ability. The experimental results demonstrate that the proposed sensor provides a low threshold detection limit of 5 mL/hr, which betters the performance of other commercial sensors at low flow rates.
Biomimetic artificial lateral-lines
Blind cavefish that survives in deep waters, is bestowed with the finest set of flow sensors called neuromasts that enable the fish to detect minute water flow disturbances down to 1μm/s. Although blind, the fish accomplishes stupendous tasks like hydrodynamic vision and super-maneuverability. The artificial micro-electromechanical systems (MEMS) sensors we developed, embrace the structural design and the sensing principles of the ingenious neuromasts sensors and attain ultrahigh sensitivity and accuracy. This work proposes the design, fabrication and experimental characterization of micro-sensors inspired by the superficial and canal neuromast sensors in the fish. The MEMS flow sensors developed could bring in a sea change in the abilities of current underwater vehicles and provide an irreplaceable alternative to the existing sensors. This proposal presents two types of sensors– LCP membrane hair cell sensor for sensing steady-state laminar (dc) flow and Pb(Zr0.52Ti0.48)O3 piezoelectric membrane hair cell sensor for sensing oscillatory (ac) flow. Through division of labor, these sensors form a system capable of performing a complete flow analysis. The word hair cell refers to the vertically standing pillar in the sensor that extends into the flow and responds to the flow variations. It is called hair cell since it works analogous to the biological hair cells in the neuromast sensors in fish. LCP membranes are often good for achieving high sensitivities due to their low elastic modulus. On the other hand, PZT membrane MEMS sensors have been established to function excellently at higher frequencies and do not need any external power supply during operation. Therefore, in order to perform a complete sensing of flow velocities and disturbances (ac flows) underwater, we designed two sensors, one for each purpose. We have successfully completed the design, batch-fabrication, in-lab and in-field characterization and accelerated reliability analysis of these bio-mimetic sensors.
Blind cavefish that survives in deep waters, is bestowed with the finest set of flow sensors called neuromasts that enable the fish to detect minute water flow disturbances down to 1μm/s. Although blind, the fish accomplishes stupendous tasks like hydrodynamic vision and super-maneuverability. The artificial micro-electromechanical systems (MEMS) sensors we developed, embrace the structural design and the sensing principles of the ingenious neuromasts sensors and attain ultrahigh sensitivity and accuracy. This work proposes the design, fabrication and experimental characterization of micro-sensors inspired by the superficial and canal neuromast sensors in the fish. The MEMS flow sensors developed could bring in a sea change in the abilities of current underwater vehicles and provide an irreplaceable alternative to the existing sensors. This proposal presents two types of sensors– LCP membrane hair cell sensor for sensing steady-state laminar (dc) flow and Pb(Zr0.52Ti0.48)O3 piezoelectric membrane hair cell sensor for sensing oscillatory (ac) flow. Through division of labor, these sensors form a system capable of performing a complete flow analysis. The word hair cell refers to the vertically standing pillar in the sensor that extends into the flow and responds to the flow variations. It is called hair cell since it works analogous to the biological hair cells in the neuromast sensors in fish. LCP membranes are often good for achieving high sensitivities due to their low elastic modulus. On the other hand, PZT membrane MEMS sensors have been established to function excellently at higher frequencies and do not need any external power supply during operation. Therefore, in order to perform a complete sensing of flow velocities and disturbances (ac flows) underwater, we designed two sensors, one for each purpose. We have successfully completed the design, batch-fabrication, in-lab and in-field characterization and accelerated reliability analysis of these bio-mimetic sensors.
Acoustically enhanced smart watch for water safety tracking and recovery
Worldwide drowning is the third leading cause of unintentional injury death with around 360,000 annual drownings. 91% of the deaths occur in low-to-middle income countries, with young children at much higher risk. There were 249 cases of death due to drowning in the Australian waterways in the one-year period from 1 July 2017 to 30 June 2018 alone. Close to 60% of the deaths occurred during recreational activities such as swimming, fishing, boating and other water-based activities. This alarming situation significantly affects society and families.
Funded by “Smile Like Drake Foundation” (SLDF) and in collaboration with Road and Maritime Services (NSW) and Australian Federal Police (AFP). This project aims to stop such tragic incidents by proposing an automated tracking system which will provide automatic and manual activation of distress signaling and allow location both above and underwater. This device will provide a great improvement in search and rescue capability and timeliness.
Worldwide drowning is the third leading cause of unintentional injury death with around 360,000 annual drownings. 91% of the deaths occur in low-to-middle income countries, with young children at much higher risk. There were 249 cases of death due to drowning in the Australian waterways in the one-year period from 1 July 2017 to 30 June 2018 alone. Close to 60% of the deaths occurred during recreational activities such as swimming, fishing, boating and other water-based activities. This alarming situation significantly affects society and families.
Funded by “Smile Like Drake Foundation” (SLDF) and in collaboration with Road and Maritime Services (NSW) and Australian Federal Police (AFP). This project aims to stop such tragic incidents by proposing an automated tracking system which will provide automatic and manual activation of distress signaling and allow location both above and underwater. This device will provide a great improvement in search and rescue capability and timeliness.
Sensitive and Flexible Polymeric Strain Sensor for Accurate Human Motion Monitoring
Flexible electronic devices offer the capability to integrate and adapt with human body. These devices are mountable on surfaces with various shapes, which allow us to attach them to clothes or directly onto the body. This paper suggests a facile fabrication strategy via electrospinning to develop a stretchable, and sensitive poly (vinylidene fluoride) nanofibrous strain sensor for human motion monitoring. A complete characterization on the single PVDF nano fiber has been performed. The charge generated by PVDF electrospun strain sensor changes was employed as a parameter to control the finger motion of the robotic arm. As a proof of concept, we developed a smart glove with five sensors integrated into it to detect the fingers motion and transfer it to a robotic hand. Our results shows that the proposed strain sensors are able to detect tiny motion of fingers and successfully run the robotic hand.
Flexible electronic devices offer the capability to integrate and adapt with human body. These devices are mountable on surfaces with various shapes, which allow us to attach them to clothes or directly onto the body. This paper suggests a facile fabrication strategy via electrospinning to develop a stretchable, and sensitive poly (vinylidene fluoride) nanofibrous strain sensor for human motion monitoring. A complete characterization on the single PVDF nano fiber has been performed. The charge generated by PVDF electrospun strain sensor changes was employed as a parameter to control the finger motion of the robotic arm. As a proof of concept, we developed a smart glove with five sensors integrated into it to detect the fingers motion and transfer it to a robotic hand. Our results shows that the proposed strain sensors are able to detect tiny motion of fingers and successfully run the robotic hand.
Sensing for Control of URVs
Underwater robotic vehicles (URVs) need to employ a number of sensors that interact with the environment in order to measure various physical quantities (measurands) and to transfer the acquired information to the central processing system that processes the information and uses it to make decisions. URVs are space-constrained with low internal volume, energy-limited, and need to maintain neutral buoyancy. Given this stringent situation, the sensors developed must be small-sized with low footprint, light in weight, robust, low-powered, surface-mountable while maintaining the streamlined body of the robot.
We developed two types of Microelectromechanical systems (MEMS) sensors that benefit the situational awareness and control of a robotic stingray by measuring various key control parameters responsible for the stingray locomotion. The first one is piezoresistive Liquid crystal polymer (LCP) flow sensor which are deployed to determine the steady velocity of propagation of the stingray. The second one is piezoelectric (PZT) micro diaphragm pressure sensors which are developed to measure the low-frequency oscillatory pressure stimuli generated by the stingray fins. Performances of the proposed PZT micro diaphragm sensors at very low frequencies (2 Hz and 1 Hz) are evaluated by performing digital holographic microscopy. The piezoelectric sensors demonstrate an excellent performance in tracking the trajectory of the fins of the stingray. These sensors also give information on the direction of propagation of the stingray and provide essential feedback on the fin flapping frequencies and amplitudes.
Underwater robotic vehicles (URVs) need to employ a number of sensors that interact with the environment in order to measure various physical quantities (measurands) and to transfer the acquired information to the central processing system that processes the information and uses it to make decisions. URVs are space-constrained with low internal volume, energy-limited, and need to maintain neutral buoyancy. Given this stringent situation, the sensors developed must be small-sized with low footprint, light in weight, robust, low-powered, surface-mountable while maintaining the streamlined body of the robot.
We developed two types of Microelectromechanical systems (MEMS) sensors that benefit the situational awareness and control of a robotic stingray by measuring various key control parameters responsible for the stingray locomotion. The first one is piezoresistive Liquid crystal polymer (LCP) flow sensor which are deployed to determine the steady velocity of propagation of the stingray. The second one is piezoelectric (PZT) micro diaphragm pressure sensors which are developed to measure the low-frequency oscillatory pressure stimuli generated by the stingray fins. Performances of the proposed PZT micro diaphragm sensors at very low frequencies (2 Hz and 1 Hz) are evaluated by performing digital holographic microscopy. The piezoelectric sensors demonstrate an excellent performance in tracking the trajectory of the fins of the stingray. These sensors also give information on the direction of propagation of the stingray and provide essential feedback on the fin flapping frequencies and amplitudes.
Development of a Biomimetic semicircular canal with MEMS sensors to restore balance
A third of adults over the age of 50 suffer from chronic impairment of balance, posture, and/or gaze stability due to partial or complete impairment of the sensory cells in the inner ear responsible for these functions. The consequences of impaired balance organ can be dizziness, social withdrawal, and acceleration of the further functional decline. Despite the significant progress in biomedical sensing technologies, current artificial vestibular systems fail to function in practical situations and in very low frequencies. We aim to develop a novel biomechanical device that closely mimics the human vestibular system.
A third of adults over the age of 50 suffer from chronic impairment of balance, posture, and/or gaze stability due to partial or complete impairment of the sensory cells in the inner ear responsible for these functions. The consequences of impaired balance organ can be dizziness, social withdrawal, and acceleration of the further functional decline. Despite the significant progress in biomedical sensing technologies, current artificial vestibular systems fail to function in practical situations and in very low frequencies. We aim to develop a novel biomechanical device that closely mimics the human vestibular system.
Biomimetic Soft-Polymer Ciliary Bundles to mimic inner ear haircells
Many animals' sensory systems involve mechano-transduction, the conversion of a mechanical stimulus to an electrical signal. Mechanosensitive cells and tissues employ a diverse set of exceptionally sensitive sensors to detect various signals including pressure, touch, sound, acceleration and fluid flow. Nature’s evolutionary path led to sensors of high functionality and robustness, in terms of material properties, anatomical architecture and energy expenditure. In the vertebrate inner ear, ultrafast and sub-Brownian threshold detection of sound, linear acceleration and angular velocity is accomplished by mechanosensitive cells that exhibit microsecond response times and nanometer-scale deflection sensitivities. These cells are called hair cells from the appearance of their sensing structures—micrometer-scale bundles of actin-based stereocilia, called hair bundles that protrude from their apical surfaces. Hair cells are also found in the fish lateral line system where they sense the velocity and direction of water flow.
we aim to develop a new class of miniaturized, biocompatible, self-powered and flexible microelectromechanical system (MEMS) flow sensors that achieve high voltage sensitivity and low velocity detection thresholds by mimicking the anatomy and function of hair cells.
Many animals' sensory systems involve mechano-transduction, the conversion of a mechanical stimulus to an electrical signal. Mechanosensitive cells and tissues employ a diverse set of exceptionally sensitive sensors to detect various signals including pressure, touch, sound, acceleration and fluid flow. Nature’s evolutionary path led to sensors of high functionality and robustness, in terms of material properties, anatomical architecture and energy expenditure. In the vertebrate inner ear, ultrafast and sub-Brownian threshold detection of sound, linear acceleration and angular velocity is accomplished by mechanosensitive cells that exhibit microsecond response times and nanometer-scale deflection sensitivities. These cells are called hair cells from the appearance of their sensing structures—micrometer-scale bundles of actin-based stereocilia, called hair bundles that protrude from their apical surfaces. Hair cells are also found in the fish lateral line system where they sense the velocity and direction of water flow.
we aim to develop a new class of miniaturized, biocompatible, self-powered and flexible microelectromechanical system (MEMS) flow sensors that achieve high voltage sensitivity and low velocity detection thresholds by mimicking the anatomy and function of hair cells.
