Triboelectric-piezoresistive Composite Tactile Sensor

To meet the demand in the future artificial intelligence applications,sensors,as a pivot support,are imperative to own the extra capability of perceiving the dynamic tactile stimuli,rather than remain in the static sensing.Tactile sensor,which measures information arising from physical interaction by converting mechanical stimuli into electrical signals,has played an essential role in the modern consumer electronics industry.Moreover,it is support of wearable electronics,artificial skins,health monitoring,motion-detecting,and human-machine interface applications.Furthermore,the rocketing development of artificial intelligence and robotics necessitates more capable sensors for accurate tactile information acquisition.However,the mono-functional sensors can hardly satisfy the demand for the precise acquisition of complex information.Hence,there is a need for a hybrid sensor for detecting multidimensional information from the same one mechanical stimulus.This strategy could describe this stimulus more precisely.Aimed at unifying the two independent signals into one comprehensive signal for identifying the complex mechanical stimuli during a contact-and separation process,we suggest recognizing tactile not only from the pressure perspective but also from the approaching process before impending contact.TENG has already obtained flourishing development,and it widens the optional strategy of hybrid sensors for achieving more information.It drives us to study on fusing the TENG and piezoresistive tactile sensor into a hybrid sensor to achieve more function.In this work,a piezoresistive pressure detecting cell and triboelectric active sensing cell are unified into a hybrid tactile sensor.The synergy of two sensing cells makes the hybrid sensor not only collects information about pressure but also reflects the approaching process,and this bi-channel electrical signal can be a criterion for distinguishing stimuli more precisely.Firstly,we integrate a porous PDMS based triboelectric active sensing unit and a porous C-TPU based piezoresistive detection unit.The material selection strategy finalizes from two aspects:stable performance for individual unit and the appropriate modulus matching.Through the study of conductive elastomer,we employed the porous C-TPU as the piezoresistive unit.On the other hand,we chose the porous PDMS as the friction layer of triboelectric sensing unit.Secondly,we characterize the hybrid sensor as a whole entity,and it exhibits resilience and robustness in mechanical properties,as well as synchronization of bi-channel signals in measurement.This hybrid tactile sensor detects both dynamic and static mechanical excitations simultaneously,with a sensitivity of 2.1 MPa^-1(in a range of below 70k Pa)and a sensing limitation of about 0.59k Pa.Plus,we study on the relationship between the speed and triboelectric voltage output and combine it with piezoresistive signals into the bi-channel signal as a criterion for identifying the stimuli.Because of the triboelectric sensing unit,the hybrid sensor not only achieves a broader detection range to an approaching or separating process but also indicates its speed,with linearity between contact or separation speed and triboelectric outputs,within a range from 1 to 100 mm s^-1.Thirdly,we built a bi-signal judgment to distinguish different actions in life scenarios.The result showed the piezoresistive and triboelectric part were both indispensable.In this way,the entire process of“approaching-contact-pushing-releasing-separating”in tactile stimuli can be precisely distinguished.Thus,the dynamic and static signals are combined as comprehensive judgment to distinguish the stimuli which are even only with nuances.As a demonstration,the hybrid sensor is fixed on a boxing glove-ped and employed to identify various types of punches.We used the low-cost fabrication to make the hybrid sensor exhibiting resilience and robustness in mechanical properties,as well as synchronization of bi-channel signals in measurement.Based on the reliable and steady pressure detection of the piezoresistive unit,we incorporate the triboelectric active sensing mechanism into the hybrid sensor.And it successfully extends the sensing range into the non-contact area(sensor's top surface to 0.7mm above it).Besides,voltage outputs present the linearity with contact-separation speed in specific area.Then the kinematical equation of approach motion can be deduced from the output voltage.With the capacity to know how much force is applied and how does it apply,our hybrid tactile sensor distinguishes the actions in life scene,like touch and push.Moreover,our hybrid sensors can even fully recognize nuanced industrial mechanical stimuli.Then,the hybrid sensor is utilized in a smart boxing target pad prototype,and successfully identify the different styles of punches.Through the introducing comprehensive sensing mechanism,the hybrid sensor appears a great potential in the intelligent sports facility and robotic touch.