patients, who are dependant on multiple injections on a daily basis Over 10% of the population suffer from trypanophobia, i.e. an extreme fear of hypodermic syringes Many other disease conditions require the delivery of therapeutic agents to the skin Safe, painless and convenient drug delivery precision drug injection, clinical monitoring possible Diabetics

engineered to

mimic the painless bite of the

mosquito. The microneedle draws liquid by capillary force to inject it.

Traditionally

microneedles made of silicon or metals standardized processes of polymers has received considerable interest biocompatibility, desirable toughness characteristics, inexpensive, easy to mass produce

Use

the V-groove with the depth of 320 m on silicon wafer Coat the SU-8 (photoresist) on the silicon wafer with the depth of 450 m and use the scraper to put the SU-8 uniformly. Silicon wafer covered the SU-8 will be set in the oven to break away the bubbles and smooth the surface by heating and vacuum. SU-8 developer used to form the microneedles Build

Wafer cleaning: Mixing H2SO4 with H2O2 as the Piranha to clean the silicon wafer and heat it up at 150 C to remove the mist. Depositing the oxide and coating the photoresist: The depths of oxide and photoresist are 1 m and 4 m respectively. Photolithographic: Utilizing the first mask to develop the V-groove. Remove the oxide and photoresist: Using the BOE and Acetone to remove the oxide and photoresist separately. KOH wet-etching: The KOH solution is 30 wt% and the temperature is set at 60C. Coating the negative photoresist, SU-8: The thickness of SU-8 is 450 m. The 2nd photolithographic: This process develops the position of the bottom of microneedles. Departing the SU-8 from the silicon wafer: Put the silicon wafer in the MF-319 and the microneedles will move off the silicon wafer.

silicon wafer is good for wet-etching, we choose the KOH as the etching solution with protection layer of nitride and oxide. Rely on the diverse crystal orientation of silicon that has different etching rates With corner compensation, we can get four (111) planes with 54.7 between the etched facet and the horizontal surface {100}

Cleaning wafer to remove the hydrocarbon and the mist. Depositing the Oxide and Nitride with the depths are 1 and 0.2 m respectively. Coating the photoresist, AZ-4620. Photolithographic and develop the microneedles. Remove the unprotected Oxide and Nitride by Reactive Ion Etching, RIE. KOH wet-etching: The KOH solution is also 30 wt% at 80C.

Transdermal drug delivery Vaccine delivery Polymer needle moulding Electrotherapy Optical clearing of skin Blood/ISF analysis

Dissolving

micro needles

Continuous/sustained

drug delivery linked with a MEMS on chip micro pump reduction of hollow needles for blood extraction

Cost

Arrays

brightfield microscopy

microneedles have the potential to revolutionize biomedical/biotechnology applications by providing precise transdermal drug delivery and localized blood sampling. During the last 10 years A lot of new and bulk fabrication processes A lot of patents More and more functionalities Some industrial implementations MEMS-based