Research On Flexible Microstress Sensor Based On CNT-PDMS Composite

Biological strain monitoring has special requirements such as flexibility,bioadherability,biocompatibility,and high sensitivity.Traditional metal strain sensors have low sensitivity and poor tensile properties(< 5%).Traditional semiconductor sensors have the advantage of high sensitivity but a small strain range,and their application in the field of biological strain monitoring is limited.The new type of carbon nanotube-polydimethylsiloxane(CNT-PDMS)composite flexible material has good bioadherability,biocompatibility,large strain mechanical tensile properties(40%),adjustable resistivity,and high sensitivity factor.It is suitable for biological strain sensing,and has been widely used in the fields of cell strain monitoring,body surface health detection,biological motion detection,etc.In this paper,the performance of CNT-PDMS composites with different CNT mass ratios(0-10wt%)are systematically explored,the guiding suggestions on the material ratio of CNT-PDMS flexible sensors in various application are put forward.With the increase of CNT mass ratio,it is found that the sensitivity of CNT-PDMS composite material decreases,the maximum tensile strength,stability and detection limit are significantly improved.If the CNT mass ratio is 2% to 4%,the sensor obtains the highest sensitivity,but the linearity is poor,the linear range is small,and the background noise is large.The 8wt% CNT-PDMS composite material has a high linear tensile sensitivity range(0%-40%)and high sensitivity(GF=1.2097),so it is most suitable for strain measurement.In this paper,the biocompatibility of CNT-PDMS composite materials was further explored by monitoring rat cardiomyocytes.Within 2 days after inoculation,there was no significant difference in cell morphology between rat cardiomyocytes cultured on CNTPDMS composite material and those cultured in petri dishe,all of them had adhered to the wall.According to the immunofluorescence staining experiment of ?-actin,there was no significant difference in the spreading area of the cells on the CNT-PDMS composite material and in the petri dish on the 3rd and 7th day of cell inoculation.The rat cardiomyocytes on the CNT-PDMS composite and in the petri dish began to beating synchronously 6 days after inoculation.The biocompatibility of the bio-flexible sensor based on the CNT-PDMS composite material designed in this paper meets the requirements of long-term(not less than 7 days)continuous cell culture.In this paper,we designed a flexible biosensor based on 8wt% CNT-PDMS composite material for the detection of contractile stress of cardiomyocytes.The sensitivity of the sensor is about 0.0257,the background resistance drift is less than 3?,and the lower limit of stress detection is 0.05 k Pa,which is much smaller than the lower limit value(1-5kpa)of myocardial cells detected by ordinary technology,and the detection performance is improved by about 20 times.