Ultrathin polyimide film and preparation method thereof

Abstract

The invention provides an ultrathin polyimide film and a preparation method thereof, and the preparation method comprises the following steps: adding a solvent into a polyamide acid solution, and fully mixing to form a mixed solution; degassing the mixed solution; spin-coating the mixed solution on the surface of a silicon wafer or a glass sheet to form a thin film; and putting the silicon wafer or the glass sheet spin-coated with the thin film into a vacuum furnace, exhausting air in the vacuum furnace, vacuumizing, heating the thin film, and enabling the polyamide acid to generate cyclization reaction to form the ultrathin polyimide film. The thickness of the ultrathin polyimide film prepared by the invention is 200nm-1000nm, the preparation method has the advantage of simplicity and stability, and the prepared nanoscale ultrathin polyimide film is suitable for all miniaturized implantable flexible devices prepared by MEMS processes.

Description

technical field [0001] The invention relates to the field of biomedical sensors, in particular to an ultra-thin polyimide film and a preparation method thereof. Background technique [0002] For biomedical implantable sensors, it is necessary to meet the following three characteristics as much as possible: (1) The materials selected for implantable devices basically do not undergo any chemical reactions in the implanted body except for their normal functions, otherwise they will Cause damage to the implanted body or the sensor itself (2) Miniaturize as much as possible, the smaller the implantable device, the smaller the acute or chronic damage caused by its implantation into the living body, for the implanted human or animal Said to have less impact. (3) The modulus of the material selected for the implantable sensor should be as low as possible. When the sensor is implanted in the organism, it will move slightly with the biological tissue in the body. Materials with too l...

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Problems solved by technology

(3) The modulus of the material selected for the implantable sensor should be as low as possible. When the sensor is implanted in the organism, it will move slightly with the biological tissue in the body. Materials with too large a modulus will cause relative movement between the sensor and the tissue. , so that the long-term friction of the sensor in the organism leads to an inflammatory response

Among them, hydrogel and silicone rubber have been widely used in some bionic tissues and materials today, but these two materials are not compatible with MEMS and integrated circuit technology, so it is difficult to realize the preparation of some implantable miniaturized smart sensors

PDMS is widely used in the biomedical field due to its good biocompatibility and transparency. The most common patterning method is soft lithography, but this patterning process still has its processing limitations and is difficult to achieve. Dimensions in the micron range

The SU8 material can be patterned with a high aspect ratio through photolithography, but it has been reported in the literature that this material is likely to cause biological rejection after long-term implantation

Parylene can be vacuum vapor deposited to form a thin film with a thickness of micron level. It has excellent dielectric properties and meets the US Pharmacopoeia Class VI standard for biomedical materials. However, the parylene film is not resistant to high temperatures, and it is difficult to integrate with today's integrated circuit technology and Compatible with silicon-based processes

Polyimide (polyimide) has been widely used in integrated circuits and MEMS processes. It has good dielectric properties, and its thermal decomposition temperature is as high as 400 ° C. Polyimide (polyimide) has been proven to have good biocompatibility It is widely used in tableware and medical appliances. Usually, the thickness of these films is at the micron level. Because the thinner the film is, the smaller the bending stiffness is, and the easier it is to fit the curved surface under the premise of ensuring the mechanical strength. And to adapt to the dislocation of biological tissues, the polyimide film prepared by traditional methods (such as directly adding 50%-70% polyamic acid N-methylpyrrolidone or N,N-dimethylacetamide or N, Solutions such as N-dimethylformamide are spin-coated on the surface of silicon wafers to form a film with a thickness of micron scale, and it is impossible to prepare a polyimide film with a thickness of nanometer scale, which is not suitable for the preparation of some micro sensors and ultra-flexible film sensors.

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