Flexible capacitive pressure sensor based on interdigital electrodes with porous microneedle arrays for physiological signal monitoring

Flexible pressure sensors have many potential applications in the monitoring of physiological signals because of their good biocompatibil-ity and wearability.However,their relatively low sensitivity,linearity,and stability have hindered their large-scale commercial application.Herein,aflexible capacitive pressure sensor based on an interdigital electrode structure with two porous microneedle arrays(MNAs)is pro-posed.The porous substrate that constitutes the MNA is a mixed product of polydimethylsiloxane and NaHCO3.Due to its porous and interdigital structure,the maximum sensitivity(0.07 kPa-1)of a porous MNA-based pressure sensor was found to be seven times higher than that of an imporous MNA pressure sensor,and it was much greater than that of aflat pressure sensor without a porous MNA structure.Finite-element analysis showed that the interdigital MNA structure can greatly increase the strain and improve the sensitivity of the sen-sor.In addition,the porous MNA-based pressure sensor was found to have good stability over 1500 loading cycles as a result of its bilayer parylene-enhanced conductive electrode structure.Most importantly,it was found that the sensor could accurately monitor the motion of afinger,wrist joint,arm,face,abdomen,eye,and Adam’s apple.Furthermore,preliminary semantic recognition was achieved by monitoring the movement of the Adam’s apple.Finally,multiple pressure sensors were integrated into a 33 array to detect a spatial pressure distribu-×tion.Compared to the sensors reported in previous works,the interdigital electrode structure presented in this work improves sensitivity and stability by modifying the electrode layer rather than the dielectric layer.

Secure Bipartite Tracking Control for Linear Leader-Following Multiagent Systems Under Denial-of-Service Attacks

Dear editor,This letter puts forward a secure feedback control scheme to bipartite tracking consensus for a set of generic linear autonomous agents subject to aperiodic and unknown denial-of-service(Do S)attacks.

Variance-Constrained Filtering Fusion for Nonlinear Cyber-Physical Systems With the Denial-of-Service Attacks and Stochastic Communication Protocol

In this paper,a new filtering fusion problem is studied for nonlinear cyber-physical systems under errorvariance constraints and denial-of-service attacks.To prevent data collision and reduce communication cost,the stochastic communication protocol is adopted in the sensor-to-filter channels to regulate the transmission order of sensors.Each sensor is allowed to enter the network according to the transmission priority decided by a set of independent and identicallydistributed random variables.From the defenders’view,the occurrence of the denial-of-service attack is governed by the randomly Bernoulli-distributed sequence.At the local filtering stage,a set of variance-constrained local filters are designed where the upper bounds(on the filtering error covariances)are first acquired and later minimized by appropriately designing filter parameters.At the fusion stage,all local estimates and error covariances are combined to develop a variance-constrained fusion estimator under the federated fusion rule.Furthermore,the performance of the fusion estimator is examined by studying the boundedness of the fused error covariance.A simulation example is finally presented to demonstrate the effectiveness of the proposed fusion estimator.

A Trust Assessment-Based Distributed Localization Algorithm for Sensor Networks Under Deception Attacks

Dear Editor,This letter is concerned with the distributed localization issue for wireless sensor networks subject to deception attacks.It is assumed that malicious nodes randomly launch attacks to tamper the ranging information between sensors.In order to accommodate the effects of deception attacks,a trust assessment-based distributed localization algorithm is proposed.Combined with data fusion of barycentric coordinates,our algorithm can achieve accurate localization.Finally,numerical simulations are given to validate the effectiveness of the proposed localization algorithm.

Stretchable organic electrochemical transistors via threedimensional porous elastic semiconducting films for artificial synaptic applications

Neuromorphic computing targets realizing biomimetic or intelligence systems capable of processing abundant tasks in parallel analogously to our brain,and organic electrochemical transistors(OECTs)that rely on the mixed ionic-electronic synergistic couple possess significant similarity to biological systems for implementing synaptic functions.However,the lack of reliable stretchability for synaptic OECTs,where mechanical deformation occurs,leads to consequent degradation of electrical performance.Herein,we demonstrate stretchable synaptic OECTs by adopting a three-dimensional poly(3-hexylthiophene)(P3HT)/styrene-ethylene-butylene-styrene(SEBS)blend porous elastic film for neuromorphic computing.Such architecture shows the full capability to emulate biological synaptic behaviors.Adjusting the accumulated layer numbers of porous film enables tunable OECT output and hysteresis,resulting in transition in plasticity.Especially,with a trilayer porous film,large-scale conductance and hysteresis are endorsed for efficient mimicking of memory-dependent synapse behavior.Benefitted from the interconnected three-dimensional porous structures,corresponding stretchable synaptic OECTs exhibit excellent mechanical robustness when stretched at a 30%strain,and maintain reliable electrical characteristics after 500 stretching cycles.Furthermore,near-ideal weight updates with near-zero nonlinearities,symmetricity in long-term potentiation(LTP)and depression,and applications for image simulation are validated.This work paves a universal design strategy toward highperformance stretchable neuromorphic computing architecture and could be extended to other flexible/stretchable electronics.

An optimization method for large van der Waals system

An optimization method for the geometry of large van der Waals system was suggested by discussing parallel dimer of benzene. The key of this method is to place some basis functions at interaction region of van der Waals molecules. It is possible to optimize large supramolecular system by using this method because it can greatly decrease the number of basis sets. This method was used to optimize the geometry of dimer of pyrene and the result is satisfactory.