This dissertation is about the development of a photothermal-based non-ablative dermal remodeling device using MEMS and nano technology. The device comprises of a MEMS fabricated microneedle array patch with gold nanorods on the needle tips. Caused by the unique surface Plasmon resonance (SPR) effect of noble metal colloids, gold nanorods embedded in the microneedles can generate heat to denature the collagen fibrils in dermis. This target-selective method expects to overcome some drawbacks of radiofrequency-based non-ablation method.

We utilized this lithography technique for generating microneedle array. The shape of the microneedles can be adjusted by changing the patterns defined on the mask as well as the distance between the mask and photo resist. The SU8 microneedle structures were utilized to make the PDMS(polydimethyl siloxnea) mold. The mold was then used to replicate the PLA(polylactic acid) microneedle patches through hot embossing.

Gold nanorods were synthesized using the seed-mediation approach. Different aspect ratio (length/width) of nanorods can be achieved by changing the seed aging time and the amount of AgNO3.It is found that near infrared (NIR) irritation of gold nanorods led to a rise of temperature immediately. The temperature increases is proportional to the concentration of gold nanorods, the exposure period and the laser intensity.

With a temperatures greater than 43℃, the protein (collagen) denatured is known to occur. To protect epidermis from the thermal damage, gold nanorods were coated only partially onto the tip surface of microneedles with the exception of the first 100μm above the bottom. Effective heating by laser excitation can only be occurred within the gold nanorods-coated portion of needles, and therefore denature the collagen fibrils in dermis. On the other hand, gold nanorods-free surface above the bottom of needles will leave the epidermis from the heat.

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