Signal Self-compensated Principles And Near-zero-strain Transfer Printing Method Of Large-area Epidermal Electronics

Epidermal electronics is the key technology of the next-generation wearable devices,widely used in the fields of clinical diagnosis,human-machine interaction,etc.Currently,most of the epidermal electronics are small-area(several square centimeters),which cannot effectively locate the source of the diseases and accurately "decode" human intentions.It is urgent to break through the bottleneck of the signal interference,the large-area manufacture and the structural damage of large-area epidermal electronics.The dissertation offers a comprehensive solution to large-area epidermal electronics through the combination of the signal self-compensated principles,the patterning processes,and the near-zero-strain Cartan transfer printing method.The large-area but ultra-thin epidermal electronics with multifunctional sensing and multi-array sensing are designed and successfully applied to health monitoring and human-machine interaction.The main research effort and the contributions of the dissertation are introduced as the follows:Firstly,the distributed-parameter equivalent circuit model across the skin-electrode interface is constructed to quantitatively estimate the interference effect of the exposed epidermal interconnects.Two signal self-compensated principles,one relying on compensation impedance and another relying on double channels,have been proposed.According to the signal self-compensated principles,five design rules are supposed to be followed once designing the large-area epidermal electrodes.The strategy that ECG is collected by the epidermal working electrodes as the target signal while s EMG is collected by EEIs and the epidermal compensation branches as noise,is developed to quantitatively verify the effectiveness of the signal self-compensated principles and the Pearson correlation coefficient of both principles are over 0.93.Secondly,we develop the manufacture methods for large-area but ultra-thin epidermal electronics without substrate,which meets the requirements of heat/sweat dissipation and imperceptible wearability of large-area epidermal electronics.Specially,we analyze waterassisted peeling,the key step in the processes,by the mechanical models to reveal the regulation of the maximum normal peeling force and to peel off the large-area but ultra-thin electronics non-destructively.Thirdly,the mathematical concept of Cartan development is firstly introduced into transfer printing on the curvilinear surfaces.It is proved that Cartan transfer printing has the excellent performances,including preservation of length and geodesic curvature,and large-area transfer printing.General differential geometric relations are constructed to connect between planar devices and devices after transfer printed on complex curvilinear surfaces,offering the solid theoretical support for the deterministic design of curved electronics.Furthermore,we discuss the non-contact,just-contact,and over-contact phenomena of head/end occurred in the general closed transfer-printed devices,and build the criterion to determine the head/end contact state of circular devices,effectively guiding the trajectory selection of Cartan transfer printing of the closed circuits.Fourthly,it is proved that Cartan transfer printing enables the transfer-printed beam-shaped device at the minimum energy state on the small-curvature and small-torsion surfaces,and enable the transfer-printed beam-shaped/ribbon-shaped/complex devices at the state of nearzero strain.The variation law of the maximum/minimum strain state within one section of the transfer-printed beam-shaped devices standing at a point on surfaces is studied to guide the design of planar devices following the geometrical features of curved surfaces.Besides,the geometry-approximated analytical strain field model is established to describe the ribbonshaped planar devices after transfer printed on small-curvature and small-torsion surfaces.Fifthly,the applications of large-area ?m-thick substrate-free epidermal electronics in healthcare monitoring and human-computer interaction are investigated from the two levels of multi-functional sensing units and multi-units of arrays.By integrating multi-functional biosensors within one epidermal electronics,it successfully captures the mutual regulation relation of various physiological parameters in the process of perspiration.We also design the 126mm×166 mm epidermal electrodes with excellent performances of heat/sweat dissipation,imperception and high fidelity.Applications of these electrodes include multichannel ECG,accurate ASL recognition,and prostheses control,as well as mapping of neck activities.