HYDROGEL BASED DERMAL PATCH WITH INTEGRATED FLEXIBLE ELECTRONICS FOR ON DEMAND DRUG DELIVERY S. Bagherifard 1,2 , A. Tamayol 1 , M. Comotto 1 , P. Mostafalu 3 , M. Akbari 1 , N. Annabi 1 , M. Ghaderi 1 , S. Sonkusale 3 , M. Guagliano 2 , M.R. Dokmeci 1 , A. Khademhosseini 1* 1 Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139, USA 2 Department of Mechanical Engineering, Politecnico di Milano, Milan 20156, Italy 3 Department of Electrical and Computer Engineering, Tufts University, Medford, MA, USA ABSTRACT It is now widely accepted that the incorporation of growth factors can improve the healing process of chronic wounds. In this paper we combined thermo-responsive drug microcarriers and flexible electronics to create a wound dressing capable of on demand drug delivery. Monodisperse thermo-responsive micoparticles containing active molecules were fabricated using a microfluidic system and were embedded inside a hydrogel. A miniaturized closed-loop electrical system with a flexible heater and temperature sensor was used to heat up the hydrogel and maintain its temperature during the release. KEYWORDS: Wound patch, Drug delivery, Thermo sensitivity, Microfluidics INTRODUCTION In some cases such as burn and diabetes, the self healing capability of skin is impaired and further in- tervention such as growth factor delivery is required [1]. Currently, there is no commercially available dermal patch that can be used for on demand release of drugs and growth factors. Here, we engineered a hydrogel-based dermal patch with integrated flexible heater and temperature sensor [2]. The hydrogel contained monodisperse thermo-responsive drug microcarriers, fabricated using microfluidic emulsion. The temperature sensor and heater are connected to microcontroller in a miniaturized closed-loop system that can monitor and stabilize the temperature. Integration of the electronic systems was achieved in a compact packaging for compatibility with the flexible, wearable platform (schematic shown in Fig. 1(a)). EXPERIMENTAL In the microfluidic flow-focusing device, the inner phase was an aqueous solution of N- isopropylacrylamide (NIPAM) (10% w/v), N,N-methylene-bis-acrylamide (0.3% w/v) and photoinitiator (0.5% w/v); the oil phase was 20% v/v Span80 in mineral oil. The particles were polymerized with UV light exposure (5 min, 850 mW, distance 8 cm). The shrinking of the particles was characterized using Zeiss Axio observer D1 microscope equipped with a heating unit. The variations of UV-vis absorption of the crosslinked PNIPAM with temperature was acquired on a BioTek spectrophotometer. Freeze dried microparticles were incubated in a fluorescein isothiocyanate-dextran (FITC–dextran, Mw 70kDa) solution (1 mg/ml). For the release studies, fluorescence intensity of FITC–dextran in the supernatant PBS solution was measured at certain time points. Loaded microparticles were dispersed in a solution of sodium alginate (alginate-Na) in distilled water (2% w/v). the alginate patch was cross linked using a solidified aqueous solution of calcium chloride (CaCl 2 , 2% w/v) and agarose (Type VII-A, 2% w/v). The patch was mounted on a microfabricated heater with resistance of ~100 Ω on a polymide film. A microcontroller (Arduino) was used to power the heater and the feedback from a temperature sensor was used to stabilize the hydrogel temperature. The flexible heater and read-out electronics were integrated on a 3D-printed flexible bandage using TangoPlus (FLX930). RESULTS AND DISCUSSION Figure 1 (b) shows the shrinking snapshots of the PNIPAM microparticles. The shrinking ratio (the variation of particles’ diameter from 25 °C to 40 °C / the initial diameter) was around 40% and independent from the initial size in the studied range (Figure 1(c)). The dynamic response of PNIPAM to 978-0-9798064-7-6/μTAS 2014/$20©14CBMS-0001 2532 18th International Conference on Miniaturized Systems for Chemistry and Life Sciences October 26-30, 2014, San Antonio, Texas, USA