Research On Low Mechanical Mismatch Stress Sensing Device For Cardiac Drug Screening

Weakening the mechanical mismatch between myocardial tissue and the stress sensor and encapsulation layer(substrate)is a key requirement for the development of advanced cardiac drug screening devices.However,the currently developed stress sensors and encapsulation layers(substrates)are difficult to replicate a variety of mechanical characteristics of myocardial tissue,such as Young’s modulus,surface adhesion,and microstructure,as well as the mechanical deformation of cardiomyocytes that are difficult to be fully mapped by sensing signals.To realize the complete mapping of the sensing signal to the mechanical deformation of cardiomyocytes,an Ag/CNT-PDMS crack sensor was designed based on the bridging mechanism of brittle-ductile bilayers.The sensor has a wide working range of 0.01 ～ 44%and a high signal-to-noise ratio of 73.3 under the strain condition of 0.01 %.When the strain is within 5%,it has a sensitivity gauge factor of 1202.6 and stability of more than2 million strain cycles.Excellent electrical performance enables complete mapping of cardiomyocytes contraction signals.To match the and Young’s modulus of the stress sensor with the myocardial tissue.In this work,the Ag/CNT-PDMS crack sensor and PDMS encapsulation layer(substrate)similar to Young’s modulus(～40 k Pa)of myocardial tissue were fabricated by adjusting the ratio of prepolymer and curing agent.This compatible Young’s modulus facilitates cardiomyocytes to produce contraction and relaxation similar to those in vivo.In addition,to enhance the adhesion of cardiomyocytes to the PDMS encapsulation layer(substrate),we performed oxygen ion etching on the PDMS encapsulation layer and added fibronectin with appropriate concentration to expand the cardiomyocytes area.To create a biomimetic cardiac tissue structure,we designed soft micro-grooves on the surface of the PDMS encapsulation layer(substrate),realizing the anisotropic growth of cardiomyocytes in vitro.Finally,a cardiac drug screening sensor with low mechanical mismatch was obtained by integrating the above highly sensitive and highly stable crack sensor with a microgroove structure PDMS encapsulation layer using micro-nano processing technology.In this work,combined with the designed data acquisition device,the contractile force signals of myocardial cells were measured for 14 days,and the process of myocardial tissue growth and aging was observed.This work also quantitatively revealed the effects of different concentrations of isoproterenol and verapamil on the contractility of cardiomyocytes.Drug evaluation experiments have demonstrated the potential of low mechanical mismatch sensing devices for cardiac drug screening in detecting the dynamic changes of myocardial contractility and exploring drug safety.