Infusion Micro-Pump Development Using MEMS Technology

International audienceDiabetes is a chronic condition that occurs when the pancreas does not produce enough insulin or when the body cannot effectively use the insulin it produces. People having type 1 diabetes require insulin (10% of all diabetics). People with type 2 diabetes can be treated with oral medication, but may also require insulin; 10% of all type 2 diabetics require insulin. Among the actual different methods to administer insulin (syringes, pens and conventional infusion pumps) a possibility to increase infuser performances is offered by the utilization of silicon based MEMS pumps (Micro- Electro Mechanical Systems). The main two pump families are classified as mechanical and non-mechanical pumps. The former contains check-valve, peristaltic, rectification without valves and rotary ones (“Displacement Pumps”) or Ultrasonic and Centrifugal (“Dynamic Pumps”); the latter consists in Pressure, Concentration, Electrical Potential gradients and Magnetic Potential micro-pumps. The micro-pump described here is an electro-mechanical device actuated with a piezoelectric-element and based on MEMS technology, able to minimize size and costs, offering a high precision pharmacological dispense. Three slices are bonded to reach the final results: top and bottom caps and an intermediate SOI. In case of anodic bonding, top and bottom caps are constituted of micromachined borophosphosilicate wafers, whereas in case of metallic bonding three silicon slices are used. The paper deals with the fabrication evolution of the device according to the different items that had to be faced during development: design, fluidic, mechanical and electrical simulations and characterization, safety requirements and final testing. Built-in reliability is ensured by two inner sensors able to detect any occlusion or malfunctioning and informing so the patient. The result is a compact, core pump chip that can deliver from 0.02 Units of insulin up to 3.6 Units per minute with accuracy better than 5%

Mechanics of Reversible Unzipping

We study the mechanics of a reversible decohesion (unzipping) of an elastic layer subjected to quasi-static end-point loading. At the micro level the system is simulated by an elastic chain of particles interacting with a rigid foundation through breakable springs. Such system can be viewed as prototypical for the description of a wide range of phenomena from peeling of polymeric tapes, to rolling of cells, working of gecko's fibrillar structures and denaturation of DNA. We construct a rigorous continuum limit of the discrete model which captures both stable and metastable configurations and present a detailed parametric study of the interplay between elastic and cohesive interactions. We show that the model reproduces the experimentally observed abrupt transition from an incremental evolution of the adhesion front to a sudden complete decohesion of a macroscopic segment of the adhesion layer. As the microscopic parameters vary the macroscopic response changes from quasi-ductile to quasi-brittle, with corresponding decrease in the size of the adhesion hysteresis. At the micro-scale this corresponds to a transition from a `localized' to a `diffuse' structure of the decohesion front (domain wall). We obtain an explicit expression for the critical debonding threshold in the limit when the internal length scales are much smaller than the size of the system. The achieved parametric control of the microscopic mechanism can be used in the design of new biological inspired adhesion devices and machines

First-line therapy with gemcitabine and paclitaxel in locally, recurrent or metastatic breast cancer: A phase II study

BACKGROUND: This phase II study evaluated the efficacy and safety of gemcitabine (G) plus paclitaxel (T) as first-line therapy in recurrent or metastatic breast cancer. METHODS: Patients with locally, recurrent or metastatic breast cancer and no prior chemotherapy for metastatic disease received G 1200 mg/m(2 )on days 1 and 8, and T 175 mg/m(2 )on day 1 (before G) every 21 days for a maximum of 10 cycles. RESULTS: Forty patients, 39 metastatic breast cancer and 1 locally-advanced disease, were enrolled. Their median age was 61.5 years, and 85% had a World Health Organization performance status (PS) of 0 or 1. Poor prognostic factors at baseline included visceral involvement (87.5%) and ≥2 metastatic sites (70%). Also, 27 (67.5%) patients had prior adjuvant chemotherapy, 25 of which had prior anthracyclines. A total of 220 cycles (median 6; range, 1–10) were administered. Of the 40 enrolled patients, 2 had complete response and 12 partial response, for an overall response rate of 35.0% for intent-to-treat population. Among 35 patients evaluable for efficacy the response rate was 40%. Additional 14 patients had stable disease, and 7 had progressive disease. The median duration of response was 12 months; median time to progression, 7.2 months; median survival, 25.7 months. Common grade 3/4 toxicities were neutropenia in 17 (42.5%) patients each, grade 3 leukopenia in 19 (47.5%), and grade 3 alopecia in 30 (75.0%) patients; 1 (2.5%) patient had grade 4 thrombocytopenia. CONCLUSION: GT exhibited encouraging activity and tolerable toxicity as first-line therapy in metastatic breast cancer. Phase III trials for further evaluation are ongoing