An off-the-shelf, moisture-responsive, acetate-backed adhesive tape is investigated as a commercially available smart material for fabricating low-cost, multifunctional, humidity-responsive millimeter-scale structures. Laser ablation is used for cutting and thinning-down the tape to enhance its response. Water-submerged cantilevers show a radius of curvature of 3 mm or lower (for laser-thinned cantilevers). Additionally, their humidity response is a function of the angle between the longitudinal axis of the cantilever and polymer orientation. The tapes could be further functionalized with magnetic particles and used to create four-finger grippers and self-forming swimmer.Multimedia Publications
Here, we present a wireless chemical sensor using ferroparticles-embedded hydrogel (ferrogel). Chemically triggered reversible swelling and de-swelling of ferrogel immobilized on top of a planar inductor results in a modulated inductance through two competing mechanisms; ferroparticle density and magnetic field passing through the volume-changing ferrogel. Overall, the effect of the magnetic flux passing through the ferrogel dominates, thus increasing the inductance as the ferrogel swells. The resulting inductance change can be remotely monitored through wireless tracking of the coil self-resonant frequency. A ph sensor based on poly (methacrylic acid-co-acrylamide) hydrogel was fabricated and tested. The test was carried out in a laser machine acrylic chamber with buffers of varying ph values flowing through while monitoring the resonant frequency with a network analyzer. The sensor shows sensitivity of 200 khz/ph between ph values of 6 to 5 and 105 khz/ph from 5 to 4 with approximately 30 minutes of response time.
We are currently developing a smart wound dressing platform for chronic wounds as part of an NSF-funded project led by Ali Khademhosseini of the Brigham and Women's Hospital, in collaboration with Mehmet Dokmeci of Brigham and Women's Hospital, Sameer Sonkusale of Tufts University, and Babak Ziaie of Purdue University. The platform will integrate electronics and an array of physical, chemical, and biological modules capable of sensing (physical and chemical) and active intervention (biological, chemical, and physical) in the wound microenvironment. This platform will bring together several treatment and monitoring modalities on a conformal flexible substrate to revolutionize the treatment of chronic wounds.ENG/EFRI FY 2012 Awards Announcement
In this paper we present an ultrasonically-powered implantable micro oxygen generator (IMOG) that is capable of in situ tumor oxygenation through water electrolysis. Such active mode of oxygen generation is not affected by increased interstitial pressure or abnormal blood vessels that typically limit the systemic delivery of oxygen to hypoxic regions of solid tumors. Wireless ultrasonic powering (2.15 MHz) was employed to increase the penetration depth and eliminate the directional sensitivity associated with magnetic methods. In addition, ultrasonic powering allowed for further reduction in the total size of the implant by eliminating the need for a large area inductor. IMOG has an overall dimension of 1.2x1.3x8 mm^3, small enough to be implanted using a hypodermic needle or a trocar. In vitro and ex vivo experiments showed the IMOG is capable of generating more than 150 mA which in turn can create 0.525 ml/min of oxygen through electrolytic dissociation. In vivo experiments in a well-known hypoxic pancreatic tumor model (1 cm^3 in size) also verified adequate in situ tumor oxygenation in less than 10 minutes.
In this paper, we present a wireless interstitial fluid pressure sensor incorporating a perforated chamber first introduced by Guyton. The Guyton chamber allows for an accurate measurement of IFP without the interference from various cellular components by permitting the interstitial fluid to penetrate the chamber after implantation. The sensor consists of a coil, an air chamber, a silicone membrane embedded with a nickel plate, and a Guyton chamber. The fabricated device is 6 mm in diameter and 1 mm in thickness. The measured sensitivity is 20 kHz/mmHg from -5 to 15 mmHg.