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 …