A minimally invasive micro sampler for quantitative sampling with an ultrahigh-aspect-ratio microneedle and a PDMS actuator

This study describes a novel micro sampler consisting of an ultrahigh-aspect-ratio microneedle and a PDMS actuator. The microneedle was fabricated by a new method which introduced reshaped photoresist technology to form a flow channel inside. The microneedle includes two parts: shaft and pedestal. In this study, the shaft length is 1500 μm with a 45° taper angle on the tip and pedestal is 1000 μm. Besides, the shaft and pedestal are connected by an arc connection structure with a length of 600 μm. The microneedles have sufficient mechanical strength to insert into skin with a wide safety margin which was proved by mechanics tests. Moreover, a PDMS actuator with a chamber inside was designed and fabricated in this study. The chamber, acting as a reservoir in sampling process as well as providing power, was optimized by finite element analysis (FEA) to decrease dead volume and improve sampling precision. The micro sampler just needs finger press to activate the sampling process as well as used for quantitative micro injection to some extent. And a volume of 31.5 ± 0.8 μl blood was successfully sampled from the ear artery of a rabbit. This micro sampler is suitable for micro sampling for diagnose or therapy in biomedical field.