In order to make blood sample tests an artificial skin similar to that of the baby's heel is modeled and realized. The most
superficial bloodstream and the two main layers of the skin -epidermis and dermis- have to be recreated. Studies and
capillaroscopies of the baby's heel give characteristics of these layers and the bloodstream. The skin is viscohyperelastic,
but the choice of materials that will be used is based on the Young's modulus. The epidermis layer is based
on a stronger less adhesive silicon rubber Elastosil. The dermis layer is composed of a mixture based on a very soft
sticky silicon rubber Silgel and Sylgard. The mixture of Silgel with 5% Sylgard has an elastic modulus of 48 kPa which
is similar to that of the dermis. The artificial skin is an assembly of several layers including a layer of Sylgard that is
structured by a mold representing the capillary network and adapted to manufacturing processes in a clean room. Each
layer is deposited by spin coating and is combined with the other through adhesion. Mechanical tests such as tension are
performed to verify the mechanical properties of the artificial skin.
Transdermal drug delivery is a novel alternative painless way to inject medicine and therapic agents through skin. Our study investigates an array of out-of-plane microneedles to pierce the permeability barrier without reaching the nerves in the deeper layers. To the best of our knowledge, the skin behavior during the insertion of a microneedle array through its different layers has not up to now been fully dealt with. In this paper, we assume skin to be similar to a stratified material, and approximate it as composed of three layers: the stratum corneum is described by a linear isotropic material model while a hyperelastic material model (Ogden) is used for the two deeper layers. The choice of the model is all the more important since we work at a microscopic scale. We prove that differences exist between the insertion of one microneedle and the insertion of an array of microneedles in terms of the skin deformation and value of the insertion force due to the interaction among microneedles. We simulate the insertion of a micro needles array using a finite element method and the results show a relation between the microneedle diameter, the array density and the microneedle length. Our arrays of microneedles are fabricated by deep reacting ion etching (DRIE) and coated by titanium out of biocompatibility concerns. In this paper, the dimensions of the microneedles are: 500 microns in length, 30-60 microns in inner channel diameter and 100-150 microns in outer diameter in order to be in agreement with our analytically analysis. Some experimental validations are given.
A novel approach to realize arrays of out of plane micro needles is given. The exterior shape of the micro needles is realized by dry etching using a RIE. The exterior shape is realized in silicon by dry etching using a SF<sub>6</sub> and Argon plasma that achieve the progressive etching of the mask composed by silicon nitride and photoresist. The needles realized present an outer diameter of 900 nm for a height of about 7 microns. The needle is then realized by wet oxidation using a thin film of silicon nitride to perform a LOCOS at the end of the needle. The last step consists in selectively etch the Si<sub>3</sub>N<sub>4</sub> and the silicon inside the needle by xenon difluoride.
This paper deals with a work in progress concerning the development of a station for micromanipulation tasks in the air (at present not in a liquid environment). A microgripper is developed, based on piezoelectric unimorphs and bimorphs. This microgripper allows to manipulate micro-objects from several microns to several hundreds of microns in diameter. In the future the microgripper will be controlled in position and force. The first results in position control of our piezoelectric unimorph actuators show an accuracy better than 10 nm at the tip of the actuator. A low cost XY-table is also developed using SMA wires to create relative motions between the microgripper and the manipulated object. For the manipulation of smaller objects, from several hundreds of nanometers to some micrometers, a work is also in progress to develop a micromanipulation station based on an AFM microscope head connected to a simple force-feedback haptic. Moreover, based on some studied microactuators for micromanipulation, an insect-like microrobot with legs is under development. The design of legs is realized using the microactuators previously described. We are now in order to test these legs and consider the whole mechanical structure of the microrobot.