Weihua Pei

Weihua Pei
Institute of semiconductors, CAS · State Key Laboratory of Integrated Optoelectronics

Doctor of Engineering

About

147
Publications
13,617
Reads
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1,150
Citations
Citations since 2017
66 Research Items
884 Citations
2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250
Introduction

Publications

Publications (147)
Article
Objective.Existing steady-state visual evoked potential (SSVEP)-based brain-computer interfaces (BCIs) struggle to balance user experience and system performance. This study proposed an individualized space and phase modulation method to code imperceptible flickers at 60 Hz towards a user-friendly SSVEP-based BCI with high performance.Approach.The...
Article
Full-text available
Implantable intracortical microelectrodes can record a neuron’s rapidly changing action potentials (spikes). In vivo neural activity recording methods often have either high temporal or spatial resolution, but not both. There is an increasing need to record more neurons over a longer duration in vivo. However, there remain many challenges to overco...
Preprint
Full-text available
Flexible electrodes have demonstrated good biocompatibility compared to rigid electrodes in relieving encapsulation and long-term recording. The structural and functional properties of the brain in non-human primates are closer to those of humans than in rodents. However, the application of flexible electrodes on non-human primates has been rarely...
Preprint
Flexible neural microelectrodes demonstrate higher compliance and better biocompatibility than rigid electrodes. They have multiple microfilaments can be freely distributed across different brain regions. However, high-density fan-out of high-throughput flexible microelectrodes remains a challenge since monolithic integration between electrodes and...
Article
Poly(3,4-ethylenedioxythiophene) (PEDOT) is an organic material with good electrochemical activity and electrical conductivity, and it is usually electrochemically deposited on the neural probes to improve their interface properties. However, the workload for electrode modification using an electropolymerization method becomes greater with the incr...
Conference Paper
Full-text available
The absence of somatotopic sensory feedback limits the function of conventional prosthetic hands. In this study, we integrated a non-invasive sensory feedback system into a commercial Bebionic hand with new customized surface stimulation electrodes. Multiple modalities of tactile and hand aperture sensory information were conveyed to the amputee vi...
Article
Full-text available
Flexible multichannel electrode arrays (fMEAs) with multiple filaments can be flexibly implanted in various patterns. It is necessary to develop a method for implanting the fMEA in different locations and at various depths based on the recording demands. This study proposed a strategy for reducing the microelectrode volume with integrated packaging...
Article
Terahertz (THz) metamaterials for rapid label-free sensing show application potential for the detection of cancer biomarkers. A novel flexible THz metamaterial biosensor based on a low refraction index parylene-C substrate is proposed. The biomarkers are modified on non-metal areas by a three-step modification method that simplifies the modificatio...
Article
Full-text available
Metamaterial biosensors have been extensively used to identify cell types and detect concentrations of tumor biomarkers. However, the methods for in situ and non-destruction measurement of cell migration, which plays a key role in tumor progression and metastasis, are highly desirable. Therefore, a flexible terahertz metamaterial biosensor based on...
Article
Background In recent years, numerous studies on the brain-computer interface (BCI) have been published. However, the number of targets in most of the existing studies was not enough for many practical applications. New method: To achieve highly efficient communications, this study proposed a 120-target BCI system based on code-modulated visual evok...
Article
Full-text available
Electroencephalogram (EEG) electrodes are critical devices for brain-computer interface and neurofeedback. A pre-gelled (PreG) electrode was developed in this paper for EEG signal acquisition with a short installation time and good comfort. A hydrogel probe was placed in advance on the Ag/AgCl electrode before wearing the EEG headband instead of a...
Article
Full-text available
There are approximately 50 million people with epilepsy worldwide, even about 25% of whom cannot be effectively controlled by drugs or surgical treatment. A wireless closed-loop system for epilepsy detection and suppression is proposed in this study. The system is composed of an implantable optrode, wireless recording, wireless energy supply, and a...
Article
Full-text available
Brain-computer interface (BCI) based on steady-state visual evoked potential (SSVEP) has been widely studied due to the high information transfer rate (ITR), little user training, and wide subject applicability. However, there are also disadvantages such as visual discomfort and “BCI illiteracy.” To address these problems, this study proposes to us...
Article
Objective: Asynchronous brain-computer interfaces (BCIs) are more practical and natural compared to synchronous BCIs. A brain switch is a standard asynchronous BCI, which can automatically detect the specified change of the brain and discriminate between the control state and the idle state. The current brain switches still face challenges on rela...
Article
Full-text available
Monolithic integrated μLED optrode has promising applications in optogenetics due to their ability to achieve more optical channels in a smaller footprint. The current used to drive the μLED will cause electromagnetic interference (EMI) noise to the recording electrodes at a very close distance. Utilizing a grounded metal shielding layer between th...
Article
Full-text available
Objective.Low-frequency steady-state visual evoked potential (SSVEP)-based brain-computer interface (BCI) systems with high performance are prone to cause visual discomfort and fatigue. High-frequency SSVEP-based BCI systems can alleviate the discomfort, but always obtain lower performance. This study optimized the spatial properties of a proposed...
Article
Full-text available
The miniscope system is one of the calcium (Ca ²⁺ ) imaging tools with small size and lightweight and can realize the deep-brain Ca ²⁺ imaging not confined to the cerebral cortex. Combining Ca ²⁺ imaging and electrophysiology recording has been an efficient method for extracting high temporal-spatial resolution signals in the brain. In this study,...
Article
Full-text available
Elevated intraocular pressure (IOP) is the leading cause of glaucoma. As glaucoma is an irreversible neurological eye disease, it is urgent to realize timely and accurate IOP detection for diagnostic and therapeutic purposes. Here, a contact lens sensor for continuous IOP monitoring using self‐assembly graphene (SAG), is developed. The combination...
Article
Calcium (Ca²⁺) fluorescence is widely used to monitor the activity of neurons in vivo. We propose a method of detection the Ca²⁺ fluorescence intensity by integrating a μLED linear array and an optical fiber. Due to the different positions of each μLED, the range of excitation of each μLED cannot overlap that of another by controlling the luminous...
Article
Artificial synapses based on biological synapses represent a new idea in the field of artificial intelligence with future applications. Current two-terminal RRAM devices have developed tremendously due to the adjustable synaptic plasticity of artificial synapses. However, these devices still have some problems, such as current leakage and poor dura...
Article
Full-text available
Surface plasmon resonance sensors based on grating coupling exhibiting two resonant wavelengths are less observed because usually thick metal films are used. In this paper, we propose gold gratings on a gold film with two narrow reflection dips. One is sensitive to the refractive index (RI) of the cover media with a sensitivity of 720 nm/RIU. Howev...
Article
Electroencephalogram (EEG)-based biometrics have attracted increasing attention in recent years. A few studies have used visual evoked potentials (VEPs) in EEG biometrics due to their high signal-to-noise ratio (SNR) and good stability. However, a systematic comparison of different types of VEPs is still lacking. Therefore, this study proposes a sy...
Article
Full-text available
Nanoimprint technology is powerful for fabricating nanostructures in a large area. However, expensive equipment, high cost, and complex process conditions hinder the application of nano-imprinting technology. Therefore, double-layer self-priming nanoimprint technology was proposed to fabricate ordered metal nanostructures uniformly on 4-inch soft a...
Article
Full-text available
Intraocular pressure (IOP) is an essential indicator of the diagnosis and treatment of glaucoma. IOP has an apparent physiological rhythm, and it often reaches its peak value at night. To avoid missing the peak value at night and sample the entire rhythm cycle, the continuous monitoring of IOP is urgently needed. A wearable contact lens IOP sensor...
Article
Full-text available
Brain-computer interfaces (BCIs) based on rapid serial visual presentation (RSVP) have been widely used to categorize target and non-target images. However, it is still a challenge to detect single-trial event related potentials (ERPs) from electroencephalography (EEG) signals. Besides, the variability of EEG signal over time may cause difficulties...
Article
As the second leading cause of blindness in the world, glaucoma is mainly caused by persistent high intraocular pressure (IOP) that compresses the optic nerve and causes permanent damage. Noninvasive continuous monitoring of IOP is an essential method for the diagnosis and treatment of glaucoma. In this paper, we propose a new strain gauge material...
Conference Paper
The mapping of visual space onto human striate cortex allows the location of stimuli to affect the scalp distributions of electroencephalogram (EEG). To clarify the relationship between the characteristics of elicited high-frequency steady-state visual evoked potentials (SSVEPs) and the polar angle of stimulus, this study divided the annulus into e...
Conference Paper
In order to explore the effect of low frequency stimulation on pupil size and electroencephalogram (EEG), we presented subjects with 1-6Hz black-and-white-alternating flickering stimulus, and compared the differences of signal-to-noise ratio (SNR) and classification performance between pupil size and visual evoked potentials (VEPs). The results sho...
Article
New neuromorphic architectures and memory technologies with low power consumption, scalability and high-speed are in the spotlight due to the von Neumann bottleneck and limitations of Moore's law. The memristor, a two-terminal synaptic device, shows powerful capabilities in neuromorphic computing and information storage applications. Active materia...
Article
Full-text available
Optogenetics transforms specific types of neurons through genetic engineering to achieve the cell membrane expression of photosensitive channel protein. When a specific wavelength of light irradiates the photosensitive channel protein, the cell is either excited or inhibited. Optogenetics provides a precise and fast method to control the activity o...
Article
A wireless powered small volume light source composed of light emitting diode (LED) array is developed for implantation. According to the volt-ampere characteristics of LED and the load characteristics of coil coupling power supply, the light power and work distance of implant LED-array are optimized by changing the number and series-parallel conne...
Article
Tungsten-based memristors possess many advantages as candidates for memristive devices, including gradual changes in resistance states and memorization and learning functions. However, most previous reports mainly focus on studying synaptic learning rules instead of analysing the internal mechanism that results in the exterior learning rules. Herei...
Article
Full-text available
The wearable electroencephalogram (EEG) dry electrode acquisition system has shown great application prospects in mental state monitoring, the brain–computer interface (BCI), and other fields due to advantages such as being small in volume, light weight, and a ready-to-use facility. This study demonstrates a novel EEG cap with concise structure, ea...
Conference Paper
To realize asynchronous control of a brain-computer interface (BCI) system, a fast brain switch with low false positive rate (FPR) is required. This paper proposed a brain switch based on code-modulated visual-evoked potential (c-VEP), in which seven 8-bit pseudorandom codes were used to modulate the electroencephalogram (EEG) signal. This study op...
Conference Paper
A four-class brain-computer interface (BCI) system based on steady-state visual evoked potentials (SSVEPs) was developed by presenting phase-coded 60Hz stimulations on a 240Hz LCD monitor. The task-related component analysis (TRCA) algorithm was used to detect SSVEPs with individual training data. In the BCI experiment with 10 subjects, the system...
Article
Biosensors based on Rayleigh anomaly (RA) in metal gratings exhibit impressive bulk refractive index (RI) sensitivity and narrow linewidth. However, the electric field enhancement extends far away from surface of the gratings, which limits the application on biosensor where the RI changes are restricted at the sensor interface. To overcome this sho...
Article
The electroencephalography (EEG) method has recently attracted increasing attention in the study of brain activity-based biometric systems because of its simplicity, portability, noninvasiveness, and relatively low cost. However, due to the low signal-to-noise ratio of EEG, most existing EEG-based biometric systems require long duration of signals...
Article
Semiconductor technologies make major contributions to scientific and technological improvements, enabling high‐performance and low‐cost devices, chips, and systems. Photolithography technologies are at the heart of semiconductor technologies and are indispensable in fabricating microstructures and nanostructures. It is obvious that a new emerging...
Article
Graphene has been considered a promising material for high‐performance photodetectors due to its broad light‐absorption bandwidth and fast photoresponse time. However, weak light absorption (2.3%) in monolayer graphene results in the relatively low photoresponsivity of graphene photodetectors (GPDs). Moreover, the operation stability of GPDs has be...
Article
Full-text available
Cell migration and invasion are important factors during tumor progression and metastasis. Wound-healing assay and the Boyden chamber assay are efficient tools to investigate tumor development because both of them could be applied to measure cell migration rate. Therefore, a simple and integrated polydimethylsiloxane (PDMS) device was developed for...
Article
Full-text available
A high-speed steady-state visual evoked potentials (SSVEP)-based brain-computer interface (BCI) system using dry EEG electrodes was demonstrated in this study. The dry electrode was fabricated in our laboratory. It was designed as claw-like structure with a diameter of 14 mm, featuring 8 small fingers of 6 mm length and 2 mm diameter. The structure...
Article
The brain-computer interface (BCI) technology provides a potential tool for communication and control in immersive virtual reality (VR) environments. However, implementing a BCI with current VR platforms remains a challenge due to difficulties in system design and electroencephalogram (EEG) analysis. This study aims to explore the feasibility of a...
Article
Full-text available
Objective: We propose a flexible, dry and antibacterial electrode with low and stable skin electrode contact impedance for bio-potential signal monitoring. Methods: We fabricated bacterial cellulose/polyaniline/AgNO3 nanocomposite membrane (BC/PANI/AgNO3) and used it for bio-potential signal monitoring. Bacterial cellulose (BC) provides three-dimen...
Article
Full-text available
A new hybrid brain-computer interface (BCI), which is based on sequential controls by eye tracking and steady-state visual evoked potentials (SSVEPs), has been proposed for high-speed spelling in virtual reality (VR) with a 40-target virtual keyboard. During target selection, gaze point was first detected by an eye-tracking accessory. A 4-target bl...
Article
An implantable optrode composed of fiber and multi-channel flexible thin-film electrode is developed. The flexible recording electrode is made from polyimide and is wrapped around the optical fiber. The front end of the fiber is tapered by wet etching. With the tapered shape, the light can leak from the sidewall of the fiber, and the tapered tip ma...
Conference Paper
In a 256-channel electrode cap for electroencephalogram (EEG) acquisition, the inter-space between adjacent electrodes is around 20mm. Theoretical and experimental evidence predict that improving the density of electrode can get more information from the added electrodes. 10mm or less center distance, corresponding to 1000 electrodes on a full head...
Conference Paper
Mental fatigue induced by long time mental work can cause deterioration in task performance and increase the risk of accidents. Recently, electroencephalogram (EEG)-based monitoring of mental fatigue has received increasing attention in the field of brain-computer interfaces (BCI). This study aims to employ EEG signals to measure the mental fatigue...
Article
Full-text available
The microstructure mold fabrication for PDMS microfluidic chip remains complex and time-consuming process requiring special equipment and protocols: photolithography and etching. Thus, a rapid and cost-effective method is highly needed. Comparing with the traditional microfluidic chip fabricating process based on the micro-electromechanical system...
Conference Paper
Full-text available
Gaze interaction provides an efficient way for users to communicate and control in virtual reality (VR) presented by head-mounted displays. In gaze-based text-entry systems, eye tracking and brain-computer interface (BCI) are the two most commonly used approaches. This paper presents a hybrid BCI system for text entry in VR by combining steady-stat...
Article
Object Electroencephalogram (EEG) electrodes play an important role in the applications of wearable brain-computer interfaces (BCI). Although traditional wet gel-based electrodes can obtain low contact impedance and high signal-to-noise ratio (SNR), cumbersome procedures including skin preparation, gelling, and hair cleaning make them inconvenient...
Article
Full-text available
Tumour cell migration has an important impact on tumour metastasis. Magnetic manipulation is an ascendant method for guiding and patterning cells. Here, a unique miniaturized microfluidic chip integrating cell isolation and migration assay was designed to isolate and investigate cell migration. The chip was fabricated and composed of a magnet adapt...
Conference Paper
This paper proposed a novel electronic skin, which can detect 3-D force, and estimate accurate touch position at the same time. The proposed multimodal electronic skin is designed to capacitive sensing mechanism. Through the densely covered driving electrode, the detection area is divided into a number of staggered subareas. When the contact point...
Conference Paper
High-speed steady-state visual evoked potential (SSVEP)-based brain-computer interface (BCI) has been demonstrated in several recent studies. This study aimed to investigate some issues regarding feasibility of learning to control an SSVEP-based BCI speller in naïve subjects. An experiment with new BCI users was designed to answer the following que...
Article
Parylene-C (PC) is one of the most frequently used materials for flexible implantable electrode. Its interface with metal or other PC layer is critical in PC–metal-PC “sandwich” implantable neural electrodes in relation to their long-term reliability. In this study, we aim to develop a method to improve metal-PC and PC-PC adhesion in PC-based neura...
Article
Objective: This study aims to develop a flexible and cost effective dry electrode with low and stable contact impedance. With these benefits, the electrode can be practically used in ubiquitous bio-potential monitoring with similar signal to noise ratio as commercial wet electrode. Methods: A self-wetting electrode is developed by the aid of moistu...
Cover Page
In article number 1605223, Fengyu Li, Yanlin Song, and co-workers demonstrate a swarm-intelligence-inspired spontaneous process to assemble nanoparticles into an optimal interconnect between certain nodes on various substrates. The optimal interconnect leads to a 65.9% decrease in electromagnetic interference, a 17.1% decrease in delay, and a 24.5%...
Chapter
A neural interface is a kind of device or system which is used to connect neural system with external equipment, through recording electroneurographic (EEG) signals, a neural interface monitors or stimulates and regulates neural activities. To reduce as much as possible the interference of the device in neural system, neural interfaces are usually...
Article
Full-text available
A spontaneous process is demonstrated to assemble nanoparticles into optimal interconnect, as natural systems spontaneously figuring out the shortest path. The optimal interconnect leads to a 65.9% decrease in electromagnetic interference, a 17.1% decrease in delay, and a 24.5% decrease in energy-delay. It will be of great significance for intercon...
Conference Paper
In this paper, an adaptive impedance tracking front end for inductively powered body sensor node is presented. By implementing a novel impedance matching network with digitally tunable capacitor array in an inductively powered energy hsarvester chip, the system can adaptively maintain impedance match with the coil under influences from nearby human...
Article
Goal This study demonstrates that single channel electrooculography (EOG) recorded by ultrathin and flexible electrodes can be practically used to control computer or machine, with the aid of proper recognition algorithms and efficient controlling methods. Methods First, micro-fabrication process and transfer technology were used to develop a patc...
Article
Electro-deposition, electrical activation, thermal oxidation, and reactive ion sputtering are the four primary methods to fabricate iridium oxide film. Among these methods, reactive ion sputtering is a commonly used method in standard micro-fabrication processes. In different sputtering conditions, the component, texture, and electrochemistry chara...
Conference Paper
A novel kind of optrode fabricated on a sapphire substrate is proposed for optogenetic applications in neuroscience. Eight thin-film neural electrodes and a GaN-LED are monolithically integrated on the surface of a sapphire shank. The LED is used for optogenetic stimulation and the multiple electrodes are used for simultaneous recording of neural a...
Conference Paper
An eight-class SSVEP-based BCI system was designed and demonstrated in this study. To minimize the complexity of the traditional equipment and operation, only one work electrode was used. The work electrode was fabricated in our laboratory and designed as a claw-like structure with a diameter of 15 mm, featuring 8 small fingers of 4mm length and 2...
Article
Objective: A skin-potential variation (SPV) insensitive dry electrode is developed to remove the interference of SPV. Methods: Based on conventional microneedles array (MNA) - based electrode, a layer of Parylene membrane is coated at the root of microneedles to insulate the electrode from the corneum layer. Only tips of the needles are exposed...
Article
This paper presents a high-precision intelligent flexible robot grasping front-end with an integrated capacitive tactile sensor array and a conditioning chip. The capacitive tactile sensor is the primary part of the front-end, it determines the overall performance. The micro-needle array sandwich structure in the tactile sensor increases the repeat...
Article
Poly(3,4-ethylenedioxythiophene) (PEDOT) is a kind of conductive polymer. PEDOT doped with polystyrolsulfon acid (PSS) is often used as an interface material of microelectrode to improve the electrochemical characteristic. Due to unsymmetrical oxidation and reduction, the properties of PEDOT:PSS need to be improved furtherly. We use Sodium Dodecyl...