In this paper, we present a simple and low-cost technique for fabricating highly stretchable (up to 100% strain) and sensitive (gauge factor of up to 20 000) strain sensors. Our technique is based on ...transfer and embedment of carbonized patterns created through selective laser pyrolization of thermoset polymers, such as polyimide, into elastomeric substrates (e.g., PDMS or Ecoflex). Embedded carbonized materials are composed of partially aligned graphene and carbon nanotube (CNT) particles and show a sharp directional anisotropy, which enables the fabrication of extremely robust, highly stretchable, and unidirectional strain sensors. Raman spectrum of pyrolized carbon regions reveal that under optimal laser settings, one can obtain highly porous carbon nano/microparticles with sheet resistances as low as 60 Ω/□. Using this technique, we fabricate an instrumented latex glove capable of measuring finger motion in real-time.
In this Research Article, we demonstrate a facile method for the fabrication of porous-carbon/silver nanocomposites using direct laser writing on polymeric substrates. Our technique uses a ...combination of CO2 laser-induced carbonization and selective silver deposition on a polyimide sheet to create flexible highly conductive traces. The localized laser irradiation selectively converts the polyimide to a highly porous and conductive carbonized film with superhydrophilic wettability. The resulting pattern allows for selective trapping of aqueous silver ionic ink solutions into the carbonized regions, which are converted to silver nanoparticle fillers upon an annealing step. Elemental and surface morphology analysis via XRD and SEM reveals a uniform coating of Ag nanoparticles on the porous carbon. The Ag/C composite lowers the sheet resistance of the original laser carbonized polyimide from 50 to 0.02 Ω/□. The resulting patterns are flexible and electromechanically robust with less than 0.6 Ω variation in resistance after >15000 bending flexion cycles at a radius of curvature of 5 mm. Furthermore, using this technique, we demonstrate the fabrication of a wireless resonant pressure sensor capable of detecting pressures ranging from 0 to 97 kPa with an average sensitivity of −26 kHz/kPa.
The development of stretchable sensors has recently attracted considerable attention. These sensors have been used in wearable and robotics applications, such as personalized health-monitoring, ...motion detection, and human–machine interfaces. Herein, we report on a highly stretchable electrochemical pH sensor for wearable point-of-care applications that consists of a pH-sensitive working electrode and a liquid-junction-free reference electrode, in which the stretchable conductive interconnections are fabricated by laser carbonizing and micromachining of a polyimide sheet bonded to an Ecoflex substrate. This method produces highly porous carbonized 2D serpentine traces that are subsequently permeated with polyaniline (PANI) as the conductive filler, binding material, and pH-sensitive membrane. The experimental and simulation results demonstrate that the stretchable serpentine PANI/C–PI interconnections with an optimal trace width of 0.3 mm can withstand elongations of up to 135% and are robust to more than 12 000 stretch-and-release cycles at 20% strain without noticeable change in the resistance. The pH sensor displays a linear sensitivity of −53 mV/pH (r 2 = 0.976) with stable performance in the physiological range of pH 4–10. The sensor shows excellent stability to applied longitudinal and transverse strains up to 100% in different pH buffer solutions with a minimal deviation of less than ±4 mV. The material biocompatibility is confirmed with NIH 3T3 fibroblast cells via PrestoBlue assays.
Photodynamic therapy (PDT) is a promising cancer treatment modality that can selectively target unresectable tumors through optical activation of cytotoxic agents, thus reducing many side effects ...associated with systemic administration of chemotherapeutic drugs. However, limited light penetration into most biological tissues have so far prevented its widespread adoption beyond dermatology and a few other oncological applications in which a fiber optic can be threaded to the desired locations via an endoscopic approach (e.g., bladder). In this paper, we introduce an ultrasonically powered implantable microlight source, μLight, which enables in-situ localized light delivery to deep-seated solid tumors. Ultrasonic powering allows for small receiver form factor (mm-scale) and power transfer deep into the tissue (several centimeters). The implants consist of piezoelectric transducers measuring 2 × 2 × 2 mm
and 2 × 4 × 2 mm
with surface-mounted miniature red and blue LEDs. When energized with 185 mW/cm
of transmitted acoustic power at 720 kHz, μLight can generate 0.048 to 6.5 mW/cm
of optical power (depending on size of the piezoelectric element and light wavelength spectrum). This allows powering multiple receivers to a distance of 10 cm at therapeutic light output levels (a delivery of 20-40 J/cm
light radiation dose in 1-2 hours). In vitro tests show that HeLa cells irradiated with μLights undergo a 70% decrease in average cell viability as compared to the control group. In vivo tests in mice implanted with 4T1-induced tumors (breast cancer) show light delivery capability at therapeutic dose levels. Overall, results indicate implanting multiple µLights and operating them for 1-2 hours can achieve cytotoxicity levels comparable to the clinically reported cases using external light sources.
In this paper, we demonstrate a nanofiber patterning technique using field-enhanced electrospinning. Polyethylene oxide (PEO) nanofibers were electrospun on an elastomeric substrate with gold-coated ...pyramidal protrusions with the majority of fibers being deposited at the tips. The deposited nanofiber spots ranged from 8 × 8 μm2 to 60 × 60 μm2 in size, uniformly covering an area of 5 × 10 mm2. Our experiments also indicate that nanofiber pattern selectivity is highly dependent on the separation/size ratio of the pyramidal protrusions with a ratio of <1, resulting in a superior selectivity.
In this paper, we review new and emerging energy sources for wireless implantable microdevices. After a brief historical background, we review the developments in power sources in the decades ...following the pioneering works of Zworykin and Mackay in the late 1950s. These include deployment of lithium batteries and inductive powering in the 1970s, which resulted in significant growth and commercialization of implantable medical devices, such as cardiac pacemakers and cochlear implants. Recent research in nanoscale materials for energy generation has created intriguing possibilities for next generation implantable power sources in the form of flexible and biodegradable batteries and supercapacitors. In addition, energy harvesting/remote powering from various environmental physical and chemical sources within the body utilizing nanoscale materials can also offer unique possibilities for autonomous implantable microscale and nanoscale devices.
Abstract
Chronic wounds affect over 6.5 million Americans and are notoriously difficult to treat. Suboptimal oxygenation of the wound bed is one of the most critical and treatable wound management ...factors, but existing oxygenation systems do not enable concurrent measurement and delivery of oxygen in a convenient wearable platform. Thus, we developed a low-cost alternative for continuous O
2
delivery and sensing comprising of an inexpensive, paper-based, biocompatible, flexible platform for locally generating and measuring oxygen in a wound region. The platform takes advantage of recent developments in the fabrication of flexible microsystems including the incorporation of paper as a substrate and the use of a scalable manufacturing technology, inkjet printing. Here, we demonstrate the functionality of the oxygenation patch, capable of increasing oxygen concentration in a gel substrate by 13% (5 ppm) in 1 h. The platform is able to sense oxygen in a range of 5–26 ppm. In vivo studies demonstrate the biocompatibility of the patch and its ability to double or triple the oxygen level in the wound bed to clinically relevant levels.
The purpose of this study is to numerically analyze a 3D model of an implant under fatigue loads. A bone and a V shape implant were modeled using SolidWorks2008 software. In order to obtain an exact ...model, the bone was assumed as a linear orthotropic material. Mechanical loads were applied in terms of fastening torque to the abutment and mastication force applied at the top of the crown. The abutment was tightened into the implant by applying a 35 N.cm torque causing tensile stress within the abutment screw as a preload that is harmful not only for the fatigue life of the abutment, but also for the stability of the implant-abutment interface. A 700 N force at an angle of 30 degrees to the vertical direction was applied to the crown. The mechanical analysis results showed that the abutment is the critical component of the implant system in terms of fatigue failure. This is due to the fact that the tensile preloads originated from the fastening torque. The results were presented in terms of fatigue life in the abutment. Fatigue life of the abutment and implant were calculated based on the Goodman, Soderberg, Smith–Watson–Topper (SWT), and Marrow theories. According to the results of the fatigue life prediction, abutment screws may fail after about 3 × 105 cycles. The predicted results by the Goodman theory are at a very good accordance with the clinical data.
In this work, we present a laser-based fabrication technique for direct patterning of micro-channels consisting of interconnected micro-cracks on soda-lime glass. Using a CO
2
laser to deposit energy ...at a linear rate of 18.75 to 93.75 mJ mm
−1
, we were able to manipulate the micro-crack formation, while enabling rapid manufacturing and scalable production of cracked-glass microfluidic patterns on glass. At the higher end of the energy deposition rate (93.75 mJ mm
−1
), the laser fabricated microfluidic channels (1 mm wide and 20 mm long) had extremely fast wicking speeds (24.2 mm s
−1
, ×10 faster than filter paper) as a result of significant capillary action and laser-induced surface hydrophilization. At the lower end (18.75 mJ mm
−1
), 3-4 μm wide micro-cracked crevices resulted in an increased mesh/sieve density, hence, more efficiently filtering particle-laden liquid samples. The reproducibility tests revealed an averaged wicking speed of 10.6 ± 1.5 mm s
−1
measured over 21 samples fabricated under similar conditions, similar to that of filter paper (∼85%). The micro-cracked channels exhibited a stable shelf life of at least 82 days with a wicking speed within 10-13 mm s
−1
.
In this work, we present a laser-based fabrication technique for direct patterning of micro-channels consisting of interconnected micro-cracks on soda-lime glass.
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