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- Wearable red–green–blue quantum dot light-emitting diode array using high-resolution intaglio transfer printing
- Abstract: Deformable full-colour light-emitting diodes with ultrafine pixels are essential for wearable electronics, which requires the conformal integration on curvilinear surface as well as retina-like high-definition displays. However, there are remaining challenges in terms of polychromatic configuration, electroluminescence efficiency and/or multidirectional deformability. Here we present ultra-thin, wearable colloidal quantum dot light-emitting diode arrays utilizing the intaglio transfer printing technique, which allows the alignment of red–green–blue pixels with high resolutions up to 2,460 pixels per inch. This technique is readily scalable and adaptable for low-voltage-driven pixelated white quantum dot lightemitting diodes and electronic tattoos, showing the best electroluminescence performance (14,000 cdm2 at 7V) among the wearable light-emitting diodes reported up to date. The device performance is stable on flat, curved and convoluted surfaces under mechanical deformations such as bending, crumpling and wrinkling. These deformable device arrays highlight new possibilities for integrating high-definition full-colour displays in wearable electronics.
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- Stretchable silicon nanoribbon electronics for skin prosthesis
- Abstract: Sensory receptors in human skin transmit a wealth of tactile and thermal signals from external environments to the brain. Despite advances in our understanding of mechano- and thermosensation, replication of these unique sensory characteristics in artificial skin and prosthetics remains challenging. Recent efforts to develop smart prosthetics, which exploit rigid and/or semi-flexible pressure, strain and temperature sensors, provide promising routes for sensor-laden bionic systems, but with limited stretchability, detection range and spatiotemporal resolution. Here we demonstrate smart prosthetic skin instrumented with ultrathin, single crystalline silicon nanoribbon strain, pressure and temperature sensor arrays as well as associated humidity sensors, electroresistive heaters and stretchable multi-electrode arrays for nerve stimulation. This collection of stretchable sensors and actuators facilitate highly localized mechanical and thermal skin-like perception in response to external stimuli, thus providing unique opportunities for emerging classes of prostheses and peripheral nervous system interface technologies.
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- Multifunctional wearable devices for diagnosis and therapy of movement disorders
- Abstract: Wearable systems that monitor muscle activity, store data and deliver feedback therapy are the next frontier in personalized medicine and healthcare. However, technical challenges, such as the fabrication of high-performance, energy efficient sensors and memory modules that are in intimate mechanical contact with soft tissues, in conjunction with controlled delivery of therapeutic agents, limit the wide-scale adoption of such systems. Here, we describe materials, mechanics and designs for multifunctional, wearable-on-the-skin systems that address these challenges via monolithic integration of nanomembranes fabricated with a top-down approach, nanoparticles assembled by bottom-up methods, and stretchable electronics on a tissue-like polymeric substrate. Representative examples of such systems include physiological sensors, non-volatile memory and drug-release actuators. Quantitative analyses of the electronics, mechanics, heattransfer and drug-diffusion characteristics validate the operation of individual components, thereby enabling system-level multifunctionalities.
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- Electronic sensor and actuator webs for large-area complex geometry cardiac mapping and therapy
- Abstract: Curved surfaces, complex geometries, and time-dynamic deformations
of the heart create challenges in establishing intimate, nonconstraining
interfaces between cardiac structures and medical devices or surgical tools,
particularly over large areas.We constructed large area designs for diagnostic
and therapeutic stretchable sensor and actuator webs that conformally wrap the
epicardium, establishing robust contact without sutures, mechanical fixtures,
tapes, or surgical adhesives. These multifunctional web devices exploit open,
mesh layouts and mount on thin, bio-resorbable sheets of silk to facilitate
handling in a way that yields, after dissolution, exceptionally low mechanical
moduli and thicknesses. In vivo studies in rabbit and pig animal models
demonstrate the effectiveness of these device webs for measuring and spatially
mapping temperature, electrophysiological signals, strain, and physical contact
in sheet and balloon-based systems that also have the potential to deliver
energy to perform localized tissue ablation.
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- A Physically Transient Form of Silicon Electronics
- Abstract: A remarkable feature of modern silicon electronics is its ability
to remain physically invariant, almost indefinitely for practical purposes.
Although this characteristic is a hallmark of applications of integrated
circuits that exist today, there might be opportunities for systems that offer
the opposite behavior, such as implantable devices that function for medically
useful time frames but then completely disappear via resorption by the body. We
report a set of materials, manufacturing schemes, device components, and
theoretical design tools for a silicon-based complementary metal oxide
semiconductor (CMOS) technology that has this type of transient behavior,
together with integrated sensors, actuators, power supply systems, and wireless
control strategies. An implantable transient device that acts as a programmable
nonantibiotic bacteriocide provides a system-level example.
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- Flexible, foldable, actively multiplexed, high-density electrode array for mapping brain activity in vivo
- Abstract: Arrays of electrodes for recording and stimulating the brain
are used throughout clinical medicine and basic neuroscience research, yet are
unable to sample large areas of the brain while maintaining high spatial
resolution because of the need to individually wire each passive sensor at the
electrode-tissue interface. To overcome this constraint, we developed new
devices that integrate ultrathin and flexible silicon nanomembrane transistors
into the electrode array, enabling new dense arrays of thousands of amplified
and multiplexed sensors that are connected using fewer wires. We used this
system to record spatial properties of cat brain activity in
vivo, including sleep spindles, single-trial visual evoked responses and
electrographic seizures. We found that seizures may manifest as recurrent
spiral waves that propagate in the neocortex. The developments reported here
herald a new generation of diagnostic and therapeutic brain-machine interface
devices.
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- Epidermal Electronics
- Abstract: We report classes of electronic systems that achieve thicknesses,
effective elastic moduli, bending stiffnesses, and areal mass densities matched
to the epidermis. Unlike traditional wafer-based technologies, laminating such
devices onto the skin leads to conformal contact and adequate adhesion based on
van der Waals interactions alone, in a manner that is mechanically invisible to
the user. We describe systems incorporating electrophysiological, temperature,
and strain sensors, as well as transistors, light-emitting diodes,
photodetectors, radio frequency inductors, capacitors, oscillators, and
rectifying diodes. Solar cells and wireless coils provide options for power
supply. We used this type of technology to measure electrical activity produced
by the heart, brain, and skeletal muscles and show that the resulting data
contain sufficient information for an unusual type of computer game controller.
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- Materials for multifunctional balloon catheters with capabilities in cardiac electrophysiological mapping and ablation therapy
- Abstract: Developing advanced surgical tools for minimally invasive procedures represents an activity of central importance to improving human health. A key challenge is in establishing biocompatible interfaces between the classes of semiconductor device and sensor technologies that might be most useful in this context and the soft, curvilinear surfaces of the body. This paper describes a solution based on materials that integrate directly with the thin elastic membranes of otherwise conventional balloon catheters, to provide diverse, multimodal functionality suitable for clinical use. As examples, we present sensors for measuring temperature, flow, tactile, optical and electrophysiological data, together with radiofrequency electrodes for controlled, local ablation of tissue. Use of such ‘instrumented’ balloon catheters in live animal models illustrates their operation, as well as their specific utility in cardiac ablation therapy. The same concepts can be applied to other substrates of interest, such as surgical gloves.
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- Waterproof AlInGaP Optoelectronics on Flexible Tubing, Sutures, Gloves and Other Unusual Substrates, With Application Examples in Biomedicine and Robotics
- Abstract: Inorganic light emitting diodes (LEDs) and photodetectors (PDs)
represent important, established technologies for applications in solid state
lighting, digital imaging and many others. Eliminating mechanical and
geometrical design constraints imposed by the supporting semiconductor wafers
can enable alternative modes of use in areas such as biomedicine and
robotics. This paper describes systems that consist of arrays of
interconnected, ultrathin inorganic LEDs and PDs configured in mechanically
optimized layouts on unusual substrates, ranging from elastic membranes and bands,
to sheets of aluminum foil and paper, to balloons, thin ribbons and fine
threads. Light emitting sutures, implantable sheets and illuminated
plasmonic crystals that are compatible with complete immersion in biofluids and
solutions of relevance to clinical medicine illustrate the suitability of these
technologies for use in biomedicine. Waterproof optical proximity sensor
tapes capable of conformal integration on curved surfaces of gloves and thin,
refractive index monitors wrapped on tubing suitable for use in intravenous
delivery systems demonstrate possibilities in robotics and clinical
medicine. These and related systems may create important, unconventional
opportunities for optoelectronic devices.
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- Dissolvable Films of Silk Fibroin for Ultrathin, Conformal Bio-Integrated Electronics
- Abstract: Electronics that are capable of intimate, non-invasive integration
with the soft, curvilinear surfaces of biological tissues offer important
opportunities for diagnosing and treating disease and for improving
brain-machine interfaces. This paper describes a material strategy for a
type of bio-interfaced system that relies on ultrathin electronics supported by
bioresorbable substrates of silk fibroin. Mounting such devices on tissue
and then allowing the silk to dissolve and resorb initiates a spontaneous,
conformal wrapping process driven by capillary forces at the biotic / abiotic
interface. Specialized mesh designs and ultrathin forms for the electronics
ensure minimal stresses on the tissue and highly conformal coverage, even for
complex curvilinear surfaces, as confirmed by experimental and theoretical
studies. In vivo, neural mapping experiments on feline animal models
illustrate one mode of use for this class of technology. These concepts
provide new capabilities for implantable or surgical devices.
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- A Conformal, Bio-interfaced Class of Silicon Electronics for Mapping Cardiac Electrophysiology
- Abstract: In all current implantable medical devices such as pacemakers,
deep brain stimulators and epilepsy treatment devices, each electrode is
independently connected to separate control systems. The ability of these
devices to sample and stimulate tissues is hindered by this configuration and
by the rigid, planar nature of the electronics and the electrode-tissue
interfaces. Here, we report the development of a class of mechanically
flexible silicon electronics for multiplexed measurement of signals in an
intimate, conformal integrated mode on the dynamic, three-dimensional surfaces
of soft tissues in the human body. We demonstrate this technology in sensor
systems composed of 2016 silicon nanomembrane transistors configured to record
electrical activity directly from the curved, wet surface of a beating pig
heart in vivo. The devices sample with simultaneous sub-millimeter and
sub-millisecond resolution through 288 amplified and multiplexed channels. We
use this system to map the spread of spontaneous and paced ventricular
depolarization in real time, at high resolution, on the epicardial surface in a
porcine animal model. This demonstration is one example of many possible uses of
this technology in minimally invasive medical devices.
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- Materials and noncoplanar mesh designs for integrated circuits with linear elastic responses to extreme mechanical deformations
- Abstract: Electronic systems that offer elastic mechanical responses to high
strain deformations are of growing interest, due to their ability to enable new
biomedical devices and other applications whose requirements are impossible to
satisfy with conventional wafer-based technologies or even with those that
offer simple bendability. This paper introduces materials and mechanical
design strategies for classes of electronic circuits that offer extremely high
stretchability, enabling them to accommodate even demanding configurations such
as corkscrew twists with tight pitch (e.g. 90 degrees in ~1 cm) and linear
stretching to ‘rubber-band’ levels of strain (e.g. up to
~140%). The use of single crystalline silicon nanomaterials for the
semiconductor provides performance in stretchable complementary
metal-oxide-semiconductor (CMOS) integrated circuits approaching that of
conventional devices with comparable feature sizes formed on silicon
wafers. Comprehensive theoretical studies of the mechanics reveal the way
in which the structural designs enable these extreme mechanical properties
without fracturing the intrinsically brittle active materials or even inducing
significant changes in their electrical properties. The results, as
demonstrated through electrical measurements of arrays of transistors, CMOS
inverters, ring oscillators and differential amplifiers, suggest a valuable
route to high performance stretchable electronics.
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- Stretchable and Foldable Silicon Integrated Circuits
- Abstract: We have developed a simple approach to high performance,
stretchable and foldable integrated circuits. The systems integrate
inorganic electronic materials, including aligned arrays of nanoribbons of
single crystalline silicon, with ultrathin plastic and elastomeric
substrates. The designs combine multilayer neutral mechanical plane
layouts and ‘wavy’ structural configurations in silicon complementary logic gates, ring
oscillators and differential amplifiers. We performed three dimensional
analytical and computational modeling of the mechanics and the electronic
behaviors of these integrated circuits. Collectively, the results
represent routes to devices, such as personal health monitors and other
biomedical devices, that require extreme mechanical deformations during
installation/use and electronic properties approaching those of conventional
systems built on brittle semiconductor wafers.
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