Technologies that can closely monitor surgical recovery and wound healing for timely, proactive treatments represent an essential keystone to developing next-generation personalized medicine that can further reduce patient pain, prevent morbidity and death, and improve individual wellbeing. Microsurgical tissue transfer entails surgical elevation of a portion of tissue (or flap) based upon its defined vascular supply in the form of a single artery and vein. While this reconstructive strategy is well-accepted, failures do occur and almost always result from early microvascular thrombosis. This flap-threatening event occurs in 6-14% of cases, and if untreated flap necrosis and reconstructive failure are inevitable. The most common flap monitoring strategies is serial physical examination and external doppler examination. However, these strartegies are limited by its inherently subjective nature and the requirement for skilled bedside personnel to check the flap frequently. And the intermittent assessment is subject to delay in the diagnosis of malperfusion, since clear signs of malperfusion may take several hours to become obvious. Recent developments in wearable electronic sensors with built-in systems on chip enable opportunities for real-time monitoring of physiological conditions of targeted tissues. However, wearable biosensors that feature skin-interface pose a challenge: to sense physiological parameters such as oxygenation of tissue microenvironments at depth. In the case of flap monitoring, existing devices such as ViOptix are only able to monitor flaps which bear a cutaneous skin. This deficiency means that muscle flaps must be monitored with indirect sensing technology through neighboring skin, which is predisposed to delay recognition of muscle malperfusion. This absence of direct, real-time monitoring technology for muscle-only flaps gives rise to the fundamental and overarching unmet clinical need: to advance technological platforms for deep-tissue monitoring. We propose a soft wearable intelligent patch (SWIP) that incorporates microneedle waveguides to enable deep-tissue sensing of oxygenation without implantation procedures for continuous monitoring of recovery after microsurgical tissue transfer. We aim for the proposed device to enable physiological measurements from 4 different locations of skin to yield both local (tissue oxygenation, pulsation intensity, and blood flow rate) and global (pulsation rate and respiration rate) physiological information continuously and simultaneously. The sensing interface will rely on biocompatible, optical waveguides in the form of microneedles to enable light-matter interaction at deep tissue (~ 2 cm below the skin surface). The device will be equipped with a control module that provides a series of signal pre-processing and a Bluetooth Low Energy (BLE) interface to advertise the data for further processing by a cloud-based computing device. We envision that the proposed SWIP will advance diagnostic technology for reconstructive surgery and beyond, and offer real-time monitoring to facilitate precise customization and personalization in surgical recovery and rehabilitation.

The proposed research is relevant to medical technology because the design and development of the proposed SWIP are expected to establish biomedical sensing instrumentation that monitors post- surgery recovery to ensure well-being, prevent adverse events, and maximize surgical outcomes. Thus, this proposal is relevant to the part of NIH vision that pertains to fostering fundamental creative discoveries, innovative research strategies, and their applications as a basis for ultimately protecting and improving health.