## 1 Introduction
The healthcare application integrated with implanted sensors for the acquisition of physiological data innovates the mechanism of traditional healthcare into WBAN [12]. WBAN is the branch of Wireless Sensor Network (WSN), which is used to integrate numerous implanted and wireless sensors to safeguard the remote health monitoring [13; 14]. Therefore the designing of WBAN can add more value to human life in terms of timely detection and treatment [14]. The underlying aims of WBAN are to acquire physiological data from the patient(s) for steady monitoring that conclusively needs an efficient routing approach [13]. The reliable, secure, and efficient implementation of routing protocol isa challenging task in WBAN due to its unique characteristics and limitations, such as energy reduction or overheating of implanted sensors nodes. The heat-rise and energy depletion influence the constancy of a network, hence the data is transmitted through various paths in WBAN. During the last decade, several studies have been carried out, and many system have been developed on WBAN. The various characteristics of WBAN have raised the number of issues in a different layer of WBAN. At physical layer problems of interoperability, temperature control, changing topology, interference, fault acceptance, security, etc. The issues related to the MAC layer are dynamic channel assignment, control packets overhead, protocol overhead, throughput, synchronization, delay control, etc. The problems related to the network layer are mobility, localization, traffic control, temperature and heat control, optimum routing, etc. [15]. The main contribution of the paper is as follows:  
* To design an optimized (minimum heat-rise and maximize energy conservation to enhance network lifetime) routing protocol for WBAN by considering primary metrics, i.e., node temperature, residual energy for next-hop selection. * To build a self-adaptive routing algorithm, capable of selecting alternative forwarder nodes in case of unavailability of a node due to heat and residual energy. * To develop a scalable system which fulfills the requirements of practical healthcare application, integrated with several IoT healthcare based on blockchain. * Lightweight: The developed system provide the cross-platform communication between the WBAN and blockchain network using RESTful API. * Transparency: The proposed blockchain-enabled WBAN system maintains the integrity of the patient's vital signs data, and also provides unauthorized access to the personal medical information. * Scalability: The proposed system fulfills the requirements of implant in-body or on-body several implanted sensors to diverse constrained networks to a single blockchain. * High Throughput: The design platform is based on permissioned blockchain network, where all the set of entities are authorized and authentic. Hence, consensus protocol such as crash fault tolerant (CFT), and byzantine fault-tolerant (BFT) can be used to elevate the throughput of the network. In this article, we propose a blockchain-enabled WBAN based self-adaptive thermal-energy aware routing protocol. Our proposed system is based on blockchain where miniature sensors are implanted in/on the patient body in such a way that these healthcare senors get the physiological data and share with the certified user of the system within the blockchain network. Furthermore, the design system also contributes with two main constraints, i.e., implanted devices in the patient body, which can damage adjacent body tissues as a continual transfer of physiological data and node replacement due to energy conservation. Therefore to establish optimal (minimum heat-rise and maximize energy conservation to enhance network lifetime) routing protocol for WBAN by considering primary metrics, i.e., node temperature, residual energy for next-hop selection. Furthermore, the self-adaptive routing algorithm is capable of selecting alternative forwarder nodes in case of the unavailability of a node due to heat and residual energy.