Simiao Niu

Humans rely increasingly on sensors to address grand challenges and to improve quality of life in the era of digitalization and big data. For ubiquitous sensing, flexible sensors are developed to overcome the limitations of conventional rigid counterparts. Despite rapid advancement in bench-side research over the last decade, the market adoption of flexible sensors remains limited. To ease and to expedite their deployment, here, we identify bottlenecks hindering the maturation of flexible sensors and propose promising solutions. We first analyze challenges in achieving satisfactory sensing performance for real-world applications and then summarize issues in compatible sensor-biology interfaces, followed by brief discussions on powering and connecting sensor networks. Issues en route to commercialization and for sustainable growth of the sector are also analyzed, highlighting environmental concerns and …

Triboelectric nanogenerators (TENGs) utilize the phenomena of contact electrification and electrostatic induction to harvest mechanical energy from the environment. A good match between the motion frequency and the circuit characteristic frequency is critical for the effective power generation of a TENG. However, most TENGs have a time-dependent inherent capacitance (TIC-TENG), which hinders an optimal design for efficient energy conversion. Here, we propose a novel structure of a TENG with a constant inherent capacitance (CIC-TENG) and a mathematical model is established to provide analytical expressions of key output parameters of the device, which gives numerical simulation results that are in good agreement with the experimentally obtained results. Figures of merit and an optimization strategy are also given as guidelines for the optimization of material selection, geometry design, etc. Furthermore …

Wireless passive sensors, being battery-free and simple, are suitable for disposable use across various applications, from tracking food and monitoring the environment to clinical diagnostics. However, their utilization is hampered by the complexity of existing readout techniques and the absence of memory functionality within the sensor. Here, we present a reader technique that can automatically lock to the sensor value wirelessly through inductive coupling, significantly reducing the reader complexity. By integrating a high-frequency audio link and wireless powering, we demonstrate a battery-free and flexible reader. We integrated this reader for wireless temperature logging, which logs temperature data based on the irreversible geometric change of low-melting-point metal during phase transitions, resulting in non-volatile resistance change. As a whole, these results establish the feasibility of a simplistic reader …

Artificial skin that simultaneously mimics sensory feedback and mechanical properties of natural skin holds substantial promise for next-generation robotic and medical devices. However, achieving such a biomimetic system that can seamlessly integrate with the human body remains a challenge. Through rational design and engineering of material properties, device structures, and system architectures, we realized a monolithic soft prosthetic electronic skin (e-skin). It is capable of multimodal perception, neuromorphic pulse-train signal generation, and closed-loop actuation. With a trilayer, high-permittivity elastomeric dielectric, we achieved a low subthreshold swing comparable to that of polycrystalline silicon transistors, a low operation voltage, low power consumption, and medium-scale circuit integration complexity for stretchable organic devices. Our e-skin mimics the biological sensorimotor loop, whereby a …

Neurotransmitters play essential roles in regulating neural circuit dynamics both in the central nervous system as well as at the peripheral, including the gastrointestinal tract, –. Their real-time monitoring will offer critical information for understanding neural function and diagnosing disease, –. However, bioelectronic tools to monitor the dynamics of neurotransmitters in vivo, especially in the enteric nervous systems, are underdeveloped. This is mainly owing to the limited availability of biosensing tools that are capable of examining soft, complex and actively moving organs. Here we introduce a tissue-mimicking, stretchable, neurochemical biological interface termed NeuroString, which is prepared by laser patterning of a metal-complexed polyimide into an interconnected graphene/nanoparticle network embedded in an elastomer. NeuroString sensors allow chronic in vivo real-time, multichannel and multiplexed …

Intrinsically stretchable bioelectronic devices based on soft and conducting organic materials have been regarded as the ideal interface for seamless and biocompatible integration with the human body. A remaining challenge is to combine high mechanical robustness with good electrical conduction, especially when patterned at small feature sizes. We develop a molecular engineering strategy based on a topological supramolecular network, which allows for the decoupling of competing effects from multiple molecular building blocks to meet complex requirements. We obtained simultaneously high conductivity and crack-onset strain in a physiological environment, with direct photopatternability down to the cellular scale. We further collected stable electromyography signals on soft and malleable octopus and performed localized neuromodulation down to single-nucleus precision for controlling organ-specific …

A flexible sensing system includes: a flexible tag device including a first antenna, first sensor and second sensors, first modulation transistor and second modulation transistors connected to both ends of the first antenna, first ring oscillator that drives the first modulation transistor together with the first sensor, and a second ring oscillator that drives the second modulation transistor together with the second sensor; and a reader device that is flexible and includes a second antenna that is inductively coupled with the first antenna, extracts an output signal of the tag device for each frequency bandwidth, and corrects an output signal change of the tag device according to a coupling change between the first antenna and the second antenna.

Wireless power transfer can significantly extend the application range and service life of implantable medical devices, such as pacemakers, neurostimulators, and vascular applicators. However, existing transmission schemes are faced with shortcomings such as weak power, discontinuity, or impact on human health. Here, we design a subcutaneously implantable flexible ultrasound energy harvesting system that integrates a triboelectric nanogenerator (TENG) transducer and a power management circuit into a single flexible printed circuit board. We maximize the TENG transducer performance by choosing an attached-electrode TENG with optimized structural parameters, which offers 66% higher output power and lower impedance than the existing work. Such a flexible system shows broad applications in various environments. It can successfully provide a stable direct current voltage of 1.8 V with >1 mW …

Next-generation light-emitting displays on skin should be soft, stretchable and bright, , , , , –. Previously reported stretchable light-emitting devices were mostly based on inorganic nanomaterials, such as light-emitting capacitors, quantum dots or perovskites, , , , –. They either require high operating voltage or have limited stretchability and brightness, resolution or robustness under strain. On the other hand, intrinsically stretchable polymer materials hold the promise of good strain tolerance,. However, realizing high brightness remains a grand challenge for intrinsically stretchable light-emitting diodes. Here we report a material design strategy and fabrication processes to achieve stretchable all-polymer-based light-emitting diodes with high brightness (about 7,450 candela per square metre), current efficiency (about 5.3 candela per ampere) and stretchability (about 100 per cent strain). We fabricate stretchable all …

‘Smart’ bandages based on multimodal wearable devices could enable real-time physiological monitoring and active intervention to promote healing of chronic wounds. However, there has been limited development in incorporation of both sensors and stimulators for the current smart bandage technologies. Additionally, while adhesive electrodes are essential for robust signal transduction, detachment of existing adhesive dressings can lead to secondary damage to delicate wound tissues without switchable adhesion. Here we overcome these issues by developing a flexible bioelectronic system consisting of wirelessly powered, closed-loop sensing and stimulation circuits with skin-interfacing hydrogel electrodes capable of on-demand adhesion and detachment. In mice, we demonstrate that our wound care system can continuously monitor skin impedance and temperature and deliver electrical stimulation in …

Objective: Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease that affects 63 in every 100,000 Americans. Its etiology remains unknown, although inflammatory pathways appear to be important. Given the dynamic environment of the lung, we examined the significance of mechanotransduction on both inflammatory and fibrotic signaling during IPF. Innovation: Mechanotransduction pathways have not been thoroughly examined in the context of lung disease, and pharmacologic approaches for IPF do not currently target these pathways. The interplay between mechanical strain and inflammation in pulmonary fibrosis remains incompletely understood. Approach: In this study, we used conditional KO mice to block mechanotransduction by knocking out Focal Adhesion Kinase (FAK) expression in fibroblasts, followed by induction of pulmonary fibrosis using bleomycin. We examined both normal …

Burn scars and scar contractures cause significant morbidity for patients. Recently, cell-based therapies have been proposed as an option for improving healing and reducing scarring after burn injury, through their known proangiogenic and immunomodulatory paracrine effects. Our laboratory has developed a pullulan-collagen hydrogel that, when seeded with mesenchymal stem cells (MSCs), improves cell viability and augments their proangiogenic capacity in vivo. Concurrently, recent research suggests that prospective isolation of cell subpopulations with desirable transcriptional profiles can be used to further improve cell-based therapies. In this study, we examined whether adipose-derived stem cell (ASC)-seeded hydrogels could improve wound healing following thermal injury using a murine contact burn model. Partial thickness contact burns were created on the dorsum of mice. On days 5 and 10 following …

Intrinsically stretchable electronics can form intimate interfaces with the human body, creating devices that could be used to monitor physiological signals without constraining movement. However, mechanical strain invariably leads to the degradation of the electronic properties of the devices. Here we show that strain-insensitive intrinsically stretchable transistor arrays can be created using an all-elastomer strain engineering approach, in which the patterned elastomer layers with tunable stiffnesses are incorporated into the transistor structure. By varying the cross-linking density of the elastomers, areas of increased local stiffness are introduced, reducing strain on the active regions of the devices. This approach can be readily incorporated into existing fabrication processes, and we use it to create arrays with a device density of 340 transistors cm–2 and a strain insensitivity of less than 5% performance variation …

Skin-like intrinsically stretchable soft electronic devices are essential to realize next-generation remote and preventative medicine for advanced personal healthcare, , –. The recent development of intrinsically stretchable conductors and semiconductors has enabled highly mechanically robust and skin-conformable electronic circuits or optoelectronic devices,, , , , –. However, their operating frequencies have been limited to less than 100 hertz, which is much lower than that required for many applications. Here we report intrinsically stretchable diodes—based on stretchable organic and nanomaterials—capable of operating at a frequency as high as 13.56 megahertz. This operating frequency is high enough for the wireless operation of soft sensors and electrochromic display pixels using radiofrequency identification in which the base-carrier frequency is 6.78 megahertz or 13.56 megahertz. This was achieved …

The present disclosure relates to nanogenerator technology, and discloses a method and a circuit for energy management in a Triboelectric Nanogenerator (TENG), as well as an apparatus including the circuit. The method includes: storing electrical energy outputted from the TENG temporarily in a temporary energy storage; and transferring the electrical energy stored temporarily in the temporary energy storage to an energy storage. With the above solution, the temporary energy storage can be charged and discharged periodically, so as to charge the energy storage. It is possible to achieve impedance match between the TENG and the energy storage and thus a significantly improved energy storage efficiency, such that an AC outputted from the TENG can be converted into a constant-voltage DC output efficiently.

One example is directed to a reader device having a first resonance circuit and being configured to interrogate one or more other remotely-located resonance circuits, each associated with a second resonance circuit which may be part of a passive sensor circuit. The first resonance circuit is operated to cause the inductively-coupled oscillating signal to be swept over a range of frequencies and therein cause a jump or sudden transition in a frequency of the oscillating signal while the first and second resonance circuits are in sufficient proximity for inductively-coupling via an oscillating signal via their respective resonance circuits. Sensing circuitry may be used to detect the jump or sudden transition in the frequency of the oscillating signal and, by way of or in response to an indication of timing and/or a set of inductively-related parameters, data is conveyed from the sensor to the reader device via the inductively …

Compliance sensation is a unique feature of the human skin that electronic devices could not mimic via compact and thin form-factor devices. Due to the complex nature of the sensing mechanism, up to now, only high-precision or bulky handheld devices have been used to measure compliance of materials. This also prevents the development of electronic skin that is fully capable of mimicking human skin. Here, we developed a thin sensor that consists of a strain sensor coupled to a pressure sensor and is capable of identifying compliance of touched materials. The sensor can be easily integrated into robotic systems due to its small form factor. Results showed that the sensor is capable of classifying compliance of materials with high sensitivity allowing materials with various compliance to be identified. We integrated the sensor to a robotic finger to demonstrate the capability of the sensor for robotics. Further, the …

An example embodiment provides a sensor system including a tag unit and a readout unit. The tag unit includes a first sensor having a stretchable antenna and a stretchable resistor. The tag unit may be configured to create a sensing signal corresponding to a degree of stretching of the stretchable resistor, transmit the sensing signal to the readout unit through the stretchable antenna, and operate in a first region corresponding to a first frequency. The readout unit may be inductively coupled to the tag unit and may be configured to receive and read out the sensing signal, and operate in a second region corresponding to a second frequency. The first frequency may range 30 MHz to 50 MHz, and the second frequency may be different from the first frequency.