Smart Patch Research Articles

Electrochemical Dissolution of a Microneedle System for Controlled Drug Release in Smart Devices

The majority of conventional controlled release technologies tend to be based around encapsulant systems in which a polymeric binder or gel typically responds to changes in the local environment in which the delivery device has been placed. The contents are often released when the particle, capsule, film or droplet is exposed to the appropriate physico-chemical trigger (typically a change in pH) with the time-release-dose delivery characteristics controlled through manipulation of the encapsulant formulation. In this communication, the adaptation of this core strategy for use in the next generation of transdermal microdevices or smart patch is explored. The core rationale of this work relates to the development of microneedle patches through which a drug could be transported across the skin barrier upon activation by an appropriate electrochemical trigger. The microneedle in this case serves as the entry point through the strateum corneum whilst acting as a physical barrier to the transport of the drug from a reservoir within the patch. Upon activation, the microneedle dissolves thereby allowing the release of the therapeutic agent as indicated in Figure 1A,B. The methodology proposed herein focuses on the ability to control the dissolution of the conductive composite microneedle through an application of a specified potential trigger. Central to this approach is the design and fabrication of a novel nanostructured conductive film based on a composite of carbon nanoparticles and cellulose acetate phthalate (CAP). This is created through the solvent cast method onto a silicone microneedle template shown in Figure 1C. Under normal conditions, the conductive coating remains intact but, upon imposing a reducing potential on the carbon composite layer, the local pH is increased which results in the solubilisation of the pH sensitive CAP binder components. The latter is the structural glue that holds the microneedle together and thus the subsequent swelling effectively leads to the dissolution of the microneedle architecture and the release of the drug. The presentation covers three aspects: the design and characterisation of the carbon composite microneedles, the ability to electrochemically manipulate the structural integrity of the needles and the ability to effect the controlled release of model drugs such as codeine, methotrexate and fentanyl. Figure 1

Smart ECG Monitoring Patch with Built-in R-Peak Detection for Long-Term HRV Analysis.

Since heart rate variability (HRV) analysis is widely used to evaluate the physiological status of the human body, devices specifically designed for such applications are needed. To this end, we developed a smart electrocardiography (ECG) patch. The smart patch measures ECG using three electrodes integrated into the patch, filters the measured signals to minimize noise, performs analog-to-digital conversion, and detects R-peaks. The measured raw ECG data and the interval between the detected R-peaks can be recorded to enable long-term HRV analysis. Experiments were performed to evaluate the performance of the built-in R-wave detection, robustness of the device under motion, and applicability to the evaluation of mental stress. The R-peak detection results obtained with the device exhibited a sensitivity of 99.29%, a positive predictive value of 100.00%, and an error of 0.71%. The device also exhibited less motional noise than conventional ECG recording, being stable up to a walking speed of 5km/h. When applied to mental stress analysis, the device evaluated the variation in HRV parameters in the same way as a normal ECG, with very little difference. This device can help users better understand their state of health and provide physicians with more reliable data for objective diagnosis.

Analysis of the accuracy of fiber-optic strain transducers installed by using composite smart patches

The aim of this work is to investigate the accuracy of fiber-optic strain transducer related to the incomplete load transmission that can occur on composite smart patches used as base support for the installation of such transducer, commonly used for structural monitoring of concrete elements. In detail, since the dimensions of the transducer are generally very small compared to those of the structural element being monitored, attention is given not to the global reinforcement effect, which occurs when the transducer alters the entire strain field of the transversal section of the monitored element, but rather to the so-called local reinforcement effect, which is due to an incomplete load transmission from the analyzed structure to the transducer and results in a localized variation of the strain field, without affecting the global structural response of the monitored element. Theoretical studies carried out in this work have permitted the evaluation of a correction coefficient ( C), which allows the user the correction of the measured strain or the proper transducer calibration, according to the elastic characteristics of the materials and the geometry of the structure-transducer system. The accuracy of the proposed theoretical model has been verified by finite element method analysis, varying the main factors that influence the local load transmission. Successive experimental tests have corroborated the accuracy of the formula proposed for the correction of the measured strain. In summary, the results of this study showed that the use of thick patches made by high-modulus composite materials (carbon fiber–reinforced polymer etc.), or the use of short patches, can lead to coarse error on the strain measurement; on the contrary, for thin patches made by low-modulus composite materials (fiberglass etc.) and having sufficient base length, the error is less than ±1%.

Thermal Patches: Ultrastretchable and Flexible Copper Interconnect‐Based Smart Patch for Adaptive Thermotherapy (Adv. Healthcare Mater. 5/2015)

Thermal Patches: Ultrastretchable and Flexible Copper Interconnect‐Based Smart Patch for Adaptive Thermotherapy (Adv. Healthcare Mater. 5/2015)

High-resolution unpixelated smart patches with antiparallel thickness gradients of nanoparticles.

A new concept for high-resolution sensing of touch/load and location in which the number of pixels can be significantly diminished is presented. The technology is based on a flexible substrate with two parallel gold-nanoparticle strips with antiparallel sensitivity gradients for an unpixelated skin strip. The approach exhibits high location and load resolutions.

Performance of skew or rectangular smart patches for active damping of nonlinear vibrations of skew doubly curved laminated composite shells

This paper deals with the investigation of the performance of the skew or the rectangular patches of the active constrained layer damping (ACLD) treatment for active damping of geometrically nonlinear vibrations of skew doubly curved laminated composite shells. Developing a three-dimensional nonlinear electro-mechanical finite element model, the performance of the patches is examined for different configurations of their placements on the top surface of the skew substrate shells. The investigation reveals that the patches of the ACLD treatment significantly improves the active damping characteristics of the skew doubly curved laminated composite shells over the passive damping for suppressing their geometrically nonlinear vibrations. It is suggested that even though the substrate shells are skew, a rectangular patch of the ACLD treatment located at the centre of the top surface of the substrate shells should be used for achieving optimum damping of geometrically nonlinear vibrations of skew doubly curved laminated composite shells irrespective of the skew angles and boundary conditions. The effects of variations of the piezoelectric fiber orientation angle in the constraining layer of the ACLD patches and the skew angle of the substrate shells on the control authority of the ACLD patches have been extensively investigated.

Ultrastretchable and flexible copper interconnect-based smart patch for adaptive thermotherapy.

Unprecedented 800% stretchable, non-polymeric, widely used, low-cost, naturally rigid, metallic thin-film copper (Cu)-based flexible and non-invasive, spatially tunable, mobile thermal patch with wireless controllability, adaptability (tunes the amount of heat based on the temperature of the swollen portion), reusability, and affordability due to low-cost complementary metal oxide semiconductor (CMOS) compatible integration.

A stretchable and flexible system for skin-mounted measurement of motion tracking and physiological signals.

In this paper, we present a stretchable wearable system capable of i) measuring multiple physiological parameters and ii) transmitting data via radio frequency to a smart phone. The electrical architecture consists of ultra thin sensors (<; 20 μm thick) and a conformal network of associated active and passive electronics in a mesh-like geometry that can mechanically couple with the curvilinear surfaces of the human body. Spring-like metal interconnects between individual chips on board the device allow the system to accommodate strains approaching ~30% A representative example of a smart patch that measures movement and electromyography (EMG) signals highlights the utility of this new class of medical skin-mounted system in monitoring a broad range of neuromuscular and cardiovascular diseases.

Effects of Fabrication Method, Shape, Strain and Temperature on Conductive Properties of Smart Stress-Memory Patch

Fatigue is an important factor of failure of structures such as bridges, buildings, etc. To prevent the failure, a sensing method of fatigue damage is desired. In previous studies, it was demonstrated that smart stress-memory patch is a suitable and effective method for fatigue monitoring, because it is possible to evaluate a number of fatigue cycles and stress amplitude of structure wirelessly. However, there are still some problems on the conductive property. For instance, using the conventional shape of conductive film, it was found out that the crack length could not be estimated accurately because sometimes the resistance of the conductive film was unstable and did not increase monotonically as the crack length increased. Moreover, effects of environment factors such as temperature and strain have not been figured out. The objective of this research is to clarify the effects of fabrication method, shape of conductive film and environment factors on conductive property of smart stress-memory patch and to improve the sensitivity on the crack length measurement. The sensitivity of the smart patch was evaluated by changing the fabrication procedure and the shape of conductive film under strain-controlled fatigue testing. It was shown that the effects of strain could be ignored under atmosphere environment and the effect of temperature could be ignored until around 65°C. [doi:10.2320/matertrans.MAW201404]

Microneedle Electrodes Toward an Amperometric Glucose‐Sensing Smart Patch

Here, efforts toward the development of a microneedle-based glucose sensor or "smart patch" for intradermal glucose sensing are described. Metallic microneedle array electrodes, conducting polymers, and glucose oxidase form the sensor platform. This work represents the first steps toward the development of painless, transdermal-sensing devices for continuous glucose monitoring.

Effect of a cell-based bioactive smart patch after myocardial infarction in swine

Effect of a cell-based bioactive smart patch after myocardial infarction in swine

Fatigue crack behavior of thin copper sheet and its application for smart stress-memory patch

A new sensor called “smart stress-memory patch” which can measure the stress amplitude and the number of fatigue cycles and the maximum stress related to a structure subjected to fatigue loading for efficient structural health monitoring has been proposed. However, there are two problems in the real applications of smart patch. Firstly, when the sensor is adhered to the structure, the sensing property of smart patch may change because the restrained condition of the sensor would be intricately changed. Secondly, high-precision crack measurement of smart patch by optical microscope is too cumbersome in the real field. In this study, thin electrodeposited (ED) Cu specimen was prepared and attached to steel bar as a sensor of smart patch. The fatigue test was performed to examine the fatigue crack growth of the sensor attached to the structure. Furthermore, wireless devices using low power wireless modules have been developed for efficient crack measurements, and wireless devices results give close agreement with the results by microscope.

Evaluation of Fatigue Properties of Steel Bar by Smart Stress-memory Patch

A fatigue sensor called “smart stress-memory patch” has been presented to evaluate the fatigue damage of infrastructures as bridges and ship. In this study, the smart stress-memory patch was applied to the steel bar to estimate the stress amplitude and the cyclic number. Firstly, the fatigue test of the steel bar with attached sensor was carried out and the fatigue crack growth behavior of the sensor was investigated. Secondly, the stress distribution of the sensor was calculated by using the finite element method to evaluate a complex strain transfer from the steel bar. Finally, the possibility of measurement for the stress amplitude and the cyclic number by using smart patch was evaluated. The fatigue crack growth rate of the attached sensor was decreasing with the crack growth. Especially when the stress amplitude was large, the crack growth rate decreased dramatically with the crack growth. The analysis of stress distribution shows that the size of plastic zone around crack tip decreases with the crack length and the load subjected to the sensor is similar to that of the uniform displacement testing. In addition, the modified stress intensity factor based on the uniform displacement testing is proposed to correct the shape effect of the attached sensor on crack growth behavior. Appling the modified stress intensity factor to the principle of smart patch, it was demonstrated that the stress amplitude and the cyclic number of the steel bar could be estimated from the crack lengths of two sensors.

Mechanical Behavior of Notched Plate Repaired with Polymer Composite and Smart Patches - Experimental Study

This article deals with the experimental study of mechanical behavior of an edge-notched steel plate repaired by polymer composite and smart patches. The polymer composite patches are made of Kevlar/epoxy and glass/epoxy or a combination of both. The plate is single edge-notched with a constant length and the repair is done on both sides of the notched plate. Four types of patches are considered according to their lay-ups. Tensile, bending, and impact tests are conducted on the specimens according to ASTM standards. The results obtained are compared with the results for un-notched and un-repaired notched specimens. Patching has a significant effect on the mechanical properties of the notched plate. The best patches in each loading case are reinforced with nickel—titanium shape memory wires and the repaired specimens with these smart patches are again tested in tension, bending, and impact loadings. Smart patches had a more significant effect on the above behavior as compared to composite patches.

Experimental characterization of composite and smart patching repaired edge cracked plate in charpy impact

AbstractIn this study, edge‐cracked steel plates repaired on two‐sides with composite as well as smart composite patches were investigated experimentally for their response to Charpy impact test. Woven glass and Kevlar fibres were used for composite patches. Each patch was made by two layers. The crack length was kept constant for all the specimens. The types of patches were selected according to different combination of glass and/or Kevlar fibres for maximum energy absorption. Kevlar fibre composite patches showed better energy absorption. This configuration was then reinforced by shape memory alloy (SMA) wires. For fabrication of smart patches, nickel‐titanium (Ni‐Ti) wires were embedded in the Kevlar fibre composites. The SMA wires in the patches were used in 3 different temperatures or pre‐stress states. The patch of Kevlar fibre reinforced by Ni‐Ti wires treated by combination of pre‐load and temperature states showed better results than all other smart patches in Charpy impact test.

AE BEHAVIOR OF SMART STRESS MEMORY PATCH AFTER VARIABLE AMPLITUDE LOADING

Recently, the structural health monitoring becomes increasingly great important to assure the ease and safety of our life, and it is required significantly to develop non-destructive evaluation for structures such as bridges and tunnels. Some sacrificed specimens have been developed to evaluate the fatigue damage of structures such as fatigue cycles and residual lifetime, but it can be applied only when the stress history is known beforehand. These fatigue sensors need no cable and can be used at low cost in contrast to strain gage. In previous study, a smart stress memory patch was developed as a new fatigue sensor. The patch can measure simultaneously the maximum stress, stress amplitude and the number of fatigue cycles by crack length measurement and Kaiser effect of Acoustic Emission (AE). The crack growth behavior under constant amplitude (CA) loading has been investigated, and AE behavior also has been evaluated only after CA loading. However, AE characteristics after variable amplitude (VA) loading in service are extremely important. Moreover, it is very important to control AE behavior of the smart patch in order to evaluate the applied stress using Kaiser effect. In this study, fatigue test with single overload was investigated to evaluate its influence. Moreover, effect of crack length and heat treatment on AE behavior was also investigated. Finally, AE behavior of the patch was evaluated after fatigue CA loading with overload or VA loading with log-normal distribution and overload.

DBR PSi/PMMA composite materials for smart patch application

New nanostructured composite materials based on porous silicon (PSi) have been developed as a smart patch type for drug delivery applications. Distributed Bragg reflector (DBR) PSi films and caffeine-impregnated polymethyl methacrylate (PMMA) are used to produce flexible and stable composite materials in which the porous silicon matrix is covered with polymer. DBR PSi films and the composite films display a reflection at 520 and 555nm in the optical reflectivity spectrum, respectively. These composite materials are stable in aqueous buffer solutions without any degradation for 3 days. The release of caffeine and the shift of reflection peak were simultaneously measured by the use of UV–vis and reflectance spectrometer. The intensity of reflection peak from the composite film is exponentially decreased with a caffeine release. The blue shift of reflection peak results in the decrease of refractive index of composite materials during the caffeine release. The concentration of released caffeine exhibits an exponential relationship with a release time.

Fatigue Crack Growth Monitoring by Optical Fiber Sensors in Smart Composite Patch Repairs

The fiber optic smart structures allow engineers to add nerve systems to their designs, giving structures capabilities that would be very difficult to achieve by other means, including continuous assessment of damage processes. In this study, we evaluated the potentiality of the application of the optical fiber sensors to the monitoring of the fatigue crack growth behavior of composite patch repaired structures. The composite patch with embedded optical fiber sensors can be considered as a smart patch which has both repairing and monitoring functions. We used recently developed Transmission-type Extrinsic Fabry-Perot Interferometric (TEFPI) optical fiber sensors for the monitoring of fatigue crack growth behavior of cracked thick aluminum plate repaired with bonded composite patch. The sensing principle and the senor construction of the optical fiber sensor are presented. The experimental results show that it is possible to monitor the fatigue crack growth behavior of structures repaired with composite patch using the optical fiber sensor

Development of Smart Stress Memory Sensor Using AE Kaiser Effect

Reliability of structures is an important task to ensure the ease and safety of our life, and further development of non-destructive evaluation for structures such as bridges and tunnels is required. Some fatigue sensors that consist of sacrificed specimen have been developed to evaluate the fatigue damage of structures such as fatigue cyclic number and residual lifetime. However, these fatigue sensors can be used only when the applied stress amplitude is known. We tried to develop a new smart stress memory patch that measured both maximum stress and number of fatigue cycles simultaneously using Kaiser effect of Acoustic Emission (AE) and crack length. In this study, the characteristics of the smart patch was evaluated. Pure copper was used for this sensor because its good corrosion resistance, stable crack propagation and detectability of AE near yield point. Fatigue test was performed under the constant stress amplitude to evaluate the crack propagation behavior using the relationship between stress intensity factor and crack propagation rate. The obtained curve between crack length and number of fatigue cycles by these crack propagation behavior was in good agreement with experimental results. AE measurement after some fatigue tests was performed and AE was detected at the applied fatigue stress. These results demonstrated that number of fatigue cycles and the maximum stress could be measured by this fatigue sensor.

Evaluation of Rugged 'Smart Patch' Fibre-Optic Strain Sensors

Fibre-optic sensors have advantages over existing electrical sensors in many strain and stress monitoring applications. However, bare optical fibres are fragile and packaging techniques must be developed before these sensors can be used more widely. One such method is the Smart Patch, in which the fibre Bragg grating is encapsulated between plies of glass-reinforced epoxy where rugged cables are anchored. This forms a flat flexible patch in which the fibre is protected from mechanical and environmental damage. However, it is important that the mechanical strength of the patch is not achieved at the expense of good strain transfer characteristics. To confirm this, fibre Bragg gratings with acrylate and polyimide coatings were embedded in a glass-epoxy patch that was bonded to an aluminium tensile specimen. An electrical strain gauge was also bonded to the specimen to provide a strain reference. Tests were carried out at different loading rates and at temperatures from -30°C to +80°C. There was good agreement between the fibre-optic sensors and the electrical strain gauge demonstrating that the patch performed in a practically identical manner to the conventional gauges. A second experiment on a representative part of ship structure demonstrated the versatility of the patch.