*Review* **CMOS Interfaces for Internet-of-Wearables Electrochemical Sensors: Trends and Challenges**

#### **Michele Dei 1,\*, Joan Aymerich 1, Massimo Piotto 2, Paolo Bruschi 2, Francisco Javier del Campo 1 and Francesc Serra-Graells 1,3**


Received: 31 December 2018; Accepted: 28 January 2019; Published: 31 January 2019

**Abstract:** Smart wearables, among immediate future IoT devices, are creating a huge and fast growing market that will encompass all of the next decade by merging the user with the Cloud in a easy and natural way. Biological fluids, such as sweat, tears, saliva and urine offer the possibility to access molecular-level dynamics of the body in a non-invasive way and in real time, disclosing a wide range of applications: from sports tracking to military enhancement, from healthcare to safety at work, from body hacking to augmented social interactions. The term *Internet of Wearables* (IoW) is coined here to describe IoT devices composed by flexible smart transducers conformed around the human body and able to communicate wirelessly. In addition the biochemical transducer, an IoW-ready sensor must include a paired electronic interface, which should implement specific stimulation/acquisition cycles while being extremely compact and drain power in the microwatts range. Development of an effective readout interface is a key element for the success of an IoW device and application. This review focuses on the latest efforts in the field of Complementary Metal–Oxide–Semiconductor (CMOS) interfaces for electrochemical sensors, and analyses them under the light of the challenges of the IoW: cost, portability, integrability and connectivity.

**Keywords:** integrated circuits design; smart wearables; Internet of Wearables; Internet of Things; CMOS Electrochemical Sensing; Flexible Technologies; Hybrid Integration Technologies
