Use of textiles in the field of medicine is one of the oldest applications of technical textiles,(meditech) starting with bandages and healthcare products this sector has now expanded into multi-billion-dollar industry with products ranging from active textile dressings for wound healing to production of implantable scaffolds for tissue regeneration and from artificial organs to mobile and off-site health monitoring systems on apparels.
These technical textiles that are used in the healthcare sector are called Meditech. Meditech is a general term which describes a textile structure which has been designed and produced for use in a variety of medical applications, including implantable applications.
These materials are used in contact with tissues, blood, cells, proteins & any other living substances, so that these materials may be ceramic, polymers, natural fibers, metal or composite. A medical textile product should have following properties so as to avoid any future complications, viz., it should be non-toxic, it should be non-carcinogenic, it should be non-allergic, it should possess the ability to be sterilized (radiation, dry heat, boiling), it should be chemically inert, it should be biocompatible, it should have following mechanical properties like strength, elasticity, durability.
Out of the total Indian textile industry, only 13% contributes to technical textiles, and out of this 13%, the share of Meditech, in technical textiles market is in the range of 6-8%. Among the wide range of medical products, hygiene products which include sanitary napkins take up around 35%, surgical dressings take 30%, sutures have 20%, whereas the rest 15% contributes to diapers and orthopaedic implants. India ranks at 34th place in terms of Meditech products exported.
The market share of medical textiles is on a sharp increase, owing to the increasing number of elderly people as well as due advances that have been taking place in this sector. With an increase in our knowledge of internal workings of our body and the relentless inquisitiveness of the researchers fuelled by huge amounts of grants by various institutes, organisations and governments have led to some ground-breaking advancements in medical textiles.
Advancements In Meditech
Tissue engineering approaches have been increasingly considered for the repair of non-union fractions, craniofacial reconstruction or large bone defect replacements. The design of complex biomaterials and successful engineering of 3-dimensional tissue constructs is of paramount importance to meet this clinical need. Conductive scaffolds, based on conjugated polymers, present interesting candidates to address the piezoelectric properties of bone tissue and to induce enhanced osteogenesis upon implantation.
However, conductive scaffolds have not been investigated in vitro in great measure. To this end, A highly porous, electrically conductive scaffold based on PEDOT: PSS, and provide evidence that this purely synthetic material is a promising candidate for bone tissue engineering.
Conjugated polymers, in particular, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), have been numerously reported as potential candidates for biomedical applications and it has been hypothesised that they would present an ideal substrate for the growth and electrical stimulationof various cell types, most prominently osteogenic cells.
Actual long-term in vitro studies and evaluations of PEDOT:PSS as osteoinductive scaffolds are far fewer than the amount of published studies on material characterisation in other fields. To the best of our knowledge known, this is the first report of the differentiation of osteogenic precursor cells into mature, mineralised osteoblasts on a porous PEDOT:PSS scaffold.
Conductive or conjugated polymers have found wide application in multiple fields, including photovoltaics, optoelectronics, biosensors, and regenerative medicine. Polypyrrole(PPy), polyaniline (PANi), or PEDOT, among other polythiophene derivatives, are of utility as electroactive substrates or scaffolds for tissue engineering applications. The intrinsic conductivity of these conjugated systems is, however, as low as 10-7 to 10-11 S·cm-1 and it is the process of doping that converts these materials into conductors.
Controlling the size, charge, and stability of the counter ions is of paramount importance to control and fine-tune the electrochemical properties of the material and this has a major effect on the in vitro or in vivo performance of such conductive scaffolds. In this context, the ionomer mixture of PEDOT:PSS is particularly interesting due to its stability, cytocompatibility and conductivity.
The electrical properties can be further improved by solvent treatment or the addition of secondary dopants, rendering this system highly versatile for research purposes. PEDOT:PSS dispersions are furthermore commercially available and present high processability. Recent studies by Shahini et al., and Wan et al., reported on an ice-templating method to process dispersions of PEDOT:PSS into porous, three-dimensional scaffolds, allowing for their use in tissue engineering.
Large-scale bone defects, such as non-healing fractures, bone tumour ablations, bullet wounds, craniofacial surgery and reconstruction, all occur at high prevalence and impose significant physical and psychological discomfort to patients. Countless research efforts target the regeneration of existing bone or replacement of lost bone by complex biomaterials and tissue engineering approaches and the implantation of ex vivo generated bone tissue.
In 1970, Fukada and Yasuda reported that bone has inherent piezoelectric properties, suggesting that electrical stimulation would enhance the fusion of non-union bone fractures or increase healing rates. Based on clinical trials, or in vitro evaluations, no consensus on the required field strength, wave-form, amplitude or duration could be reached, but there is growing evidence that external electrical stimulation has an effect on cell proliferation, migration, and mineralisation.
Conductive materials may even further support osteogenesis in vitro and bone regeneration in vivo upon biomaterial implantation. In this respect, PEDOT:PSS scaffolds provide an interesting cell culture substrate for osteogenic differentiation. In vitro evaluation with human mesenchymal stem cells or mouse, pre-adipocytes confirmed cell adhesion and viability on porous, freeze-dried PEDOT:PSS scaffolds. <
It could be demonstrated that the development of a highly porous, conductive scaffold based on PEDOT:PSS that supported the differentiation of pre-osteogenic precursor cells (MC3T3-E1) into mature osteoblasts. Generating scaffolds of high pore interconnectivity and pore diameters above 100 μm has been of major interest in many tissue engineering approaches and has been reported to be of importance for cell fate, infiltration and three-dimensional tissue formation.
The decrease in mechanical properties can be explained by a wetting process and resulting water absorbance (without observed swelling) and thus a plasticization of the polymer that leads to a decreased Tg and lowers elastic modulus. Bone, appearing in its many forms and executing distinct functions from the load bearing to organ protection, also has unique mechanical properties, ranging from 0.1 to 1 GPa for cancellous bone and around 10 GPa for cortical bone.
These properties could only be matched by artificial hydroxyapatite scaffolds or ceramics. Elastic moduli of several GPa reflect mechanical properties of bulk native bone. However, cells are sensitive to their microenvironmental elasticity and the commitment to an osteogenic state has been demonstrated on substrates in the range of several kPa, which this scaffold provides. PEDOT:PSS substrates, in the form of thin films, have primarily found interest in the fields of biosensors, photovoltaic and optoelectronics, where electrical properties, thermal stability, and crystallinity have been well characterised. Electrical conductivity and stability of three-dimensional scaffolds in physiological environments has been addressed in less detail.
Indeed, the material properties of three-dimensional PEDOT:PSS scaffolds in the dry state, without the addition of electrolytes, or after prolonged incubation in cell culture media, have not been characterised in previous studies, to the best of our knowledge. The conductivity of PEDOT:PSS films or substrates has furthermore been reported to highly process dependent, in particular varying depending on added solvents, annealing temperature or material morphology
Highly porous, conductive scaffolds were produced by freeze-drying a PEDOT:PSS dispersion. Scaffolds present high pore interconnectivity and a median pore diameter of 50 µm, allowing for cell infiltration and matrix deposition within the void space. It was demonstrated that PEDOT:PSS is suitable as a scaffold for bone tissue engineering, indicated by the differentiation of osteogenic precursor cells (MC3T3-E1) into osteocalcin positively stained osteoblasts that express significantly enhanced levels of ALPL, RUNX2 and COL1A1 and deposit mineralised ECM.
Wearable Health Care SoCs (System-on-chip)
Smart textiles can be defined as textiles that are able to sense and respond to changes in their environment. Wearable health care consists of health monitoring devices which are embedded in a textile substrate.
Since wearable systems have specific substrates (textiles), I/O devices, and network environments, dedicated, custom chips must be designed with their target applications in mind. For example, textiles are good for heat protection—keeping the human body warm—and therefore are not good for heat dissipation, which most computer systems need. And textiles are good insulators, easily inducing rather high static charges that can damage CMOS ICs. Most component packages are optimized for joining to printed circuit boards.
Instead, wearable components must be optimized to interface with textile circuitry, and this new environment brings new challenges for the IC designer. Wearable health care systems are usually composed of a power management unit, a sensor analogue front end (AFE), a digital signal processor, a communication block, and an actuator.
All of these blocks should be optimized for the textile environment. The first example discussed here is a self-configured, wearable body sensor network (BSN) system with high-efficiency, wirelessly powered sensors that can continuously monitor a patient’s electrocardiogram (ECG). This system has eliminated the large form factors and the battery power limitations of previous wearable, chronic disease– monitoring systems.
The adhesive bandage–type sensor patch is composed of the sensor chip, a planar fashionable circuit board (P-FCB) inductor, and a pair of dry P-FCB electrodes. The sensor chip harvests its power from the surrounding health monitoring band using an adaptive threshold rectifier (ATR). With an ATR, the VTH drop of the diode-connected transistor is minimized to improve the rectification efficiency, and this ATR improves rectification efficiency by up to 54.9% at the high-frequency band.
The health-monitoring chest band with the integrated P-FCB inductor array is worn over the chest, and the network controller automatically locates the sensor position, configures the sensor type, wirelessly provides power to the configured sensors, and transacts data with only the selected sensors while dissipating 5.2 mW using a single 1.8-V supply. The second system is a low-power, highly sensitive, wearable SoC for cardiac patients that performs thoracic impedance variance (TIV) and ECG monitoring, implemented as a poultice like plaster sensor.
The 15 cm by 15 cm patch fabricated using P-FCB consists of four layers. Layer 1 is a 25-electrode array for reconfigurable TIV and ECG sensing; layer 2 is a fabric inductor for system start-up; layer 3 is a thin, flexible battery; and layer 4 is a fabric circuit board onto which the SoC is directly wire-bonded. A user puts the patch on the chest to monitor the TIV and ECG signals, and he or she can start and stop the system by using an inductively coupled power switch that includes an ID verification function.
BCC is used to upload recorded data to a central base station when on-chip storage is full and download system commands when a new configuration is required. With the help of a high quality, balanced sinusoidal current source and low-noise, reconfigurable readout electronics, 0.1-Ω TIV detection are possible with a sensitivity of 3.17 V/Ω and an SNR of 40 dB. A cm-range, 13.56-MHz fabric inductor coupling is used to start and stop the SoC remotely.
Moreover, a 5% duty-cycled BCC is exploited for 0.2 nJ/b, 1-Mb/s energy-efficient external data communication. The pro+posed SoC dissipates a peak power of 3.9 mW when operating in body channel receiver mode and consumes 2.4 mW when operating in TIV and ECG detection mode. The next example is a wearable mental health measurement system incorporating the nonlinear analysis of physiological rhythm, including heart-rate variability (HRV) and electroencephalography (EEG) signals, for high accuracy.
This system is implemented in a 31-g headband that measures scalp signals and performs nonlinear chaotic analysis to measure stress levels. In this system, an independent component analysis (ICA) accelerator is adapted to extract the original EEG source from measured scalp signals. The four-channel, 10-b signals acquired by the sensor front end are mixed with other signals inside the brain and body.
The ICA enhances HRV signal extraction, removes noise, and achieves noise free EEG signals. As a result of ICA, each signal is divided into four independent components according to their non-Gaussian characteristics. Compared with the extracted HRV from the ECG signal, the HRV extracted from the independent component has only a 1.84% root mean square difference (PRD) while the HRV from scalp signals has a PRD that is four times greater. A lightweight BAN using three layers, coin-sized fabric patches have been developed for sleep-monitoring systems. It consists of a networkcontroller (NC) patch, 14 ExG sensor node (SN) patches, and a wearable band of conductive-yarn with five sublines (P, D, C, G, and R representing power, data, clock, ground, and reference).
The NC patch and the SN patch have three P-FCB layers, and total thicknesses are fewer than 5 mm and 2 mm, respectively (layer 1 is an electrode; layer 2 is a power plane, and layer 3 consists of electronics). A continuous data transmission (CDT) protocol is proposed for low power and real-time scalability by in-order data transmission using the wearable band with several sensors. Based on this protocol, a linked list–based network manager (LLM), an adaptive dual-mode controller (ADMC) in the network controller IC, and a low-swing data transmitter (D-TX) with its own back-end circuits are introduced.
The LLM and ADMC can adaptively change the network configuration according to the dynamic network variances in real time, and the D-TX can become a low-energy data transmitter (0.33 pJ/b) with a data rate of 20 Mb/s for the wearable band interface. These two low-power ICs, which are implemented in a 0.18-μm CMOS process and operate with a 1.5-V supply, consume 75 nW and 25 nW, respectively. Last, a compact electro acupuncture (EA) system has been proposed for multimodal feedback EA treatment as one type of wearable health care application.
The proposed system is composed of a needle, a compact EA patch, and an interconnecting conductive thread. The compact EA patch is 3 cm in diameter and is fabricated with P-FCB; it consists of three layers. An electrode layer includes surface electrodes for the closed-current loop, differential electrodes for multimodal sensing, and a BCC electrode for external communication.
A power layer provides reliable power to the system. Finally, a circuit layer is made up of a P-FCB on which the adaptive stimulator IC is directly wire-bonded and to which a coin battery is attached. The adaptive stimulator IC can form a closed current loop for even a single needle and measure the electromyography (EMG) signal and skin temperature to analyze the stimulation status as well as supply programmable stimulation current (from 40 nA to 1 mA) in five different modes.
The large time constant (LTC) sample and hold (S/H) current-matching technique achieves high-precision charge balancing (1 10 nA) for the patient’s safety. The measured data can be wirelessly transmitted to the external EA analyzer through the BCC transceiver for low power consumption.
The external EA analyzer can show the patient’s status, such as muscle fatigue and changes in the skin temperature, and based on these analyses the practitioner can adaptively change the stimulation parameters to achieve optimal treatment value. This stimulator chip consumes 6.8 mW at 1.2 V and supports 32 different current levels.
In recent years, conventional textiles and electronic components have been integrated to produce wearable diagnostics and therapeutic systems for monitoring vital signs and body-related parameters in medical and protective textile applications. Furthermore, the integration of sensors and actuators into textile materials with the development of high-efficiency conducting polymer actuator fibers and conducting polymer fibers with chemical sensing is about to be realized. All these electronic textile systems require appropriate electroconductive textile structures as a corner stone.
The future success of the technologies and products described and discussed in this chapter depends to a large extend on the availability of electroconductive textile structures as raw materials and, of course, on their price. The price can be justified by excellent properties to withstand harsh conditions in their later application in everyday life.
Besides the basic materials needed to produce smart textiles, also the processes continuously should be improved. For instance, thin layer technologies are crucial for the convergence and rejuvenation of electronics and textiles. Coating and printing processes are crucial for the increasing scaling down and embedding of electronic components into medical textiles. According to the research agenda of the European Technology Platform for Embedded Computing Systems (ARTEMSIS), 90% of computing devices are in embedded systems today. By 2020 this will amount to 40 billion devices worldwide.
However, this ‘embedded everywhere’ evolution will only be successful if the devices are unobtrusive and reliable for the user. For instance, sensors integrated into clothing should not be sensitive to motion artefacts or deformation.
Last, but not least, standards are needed for documentation of the performance and safety of these new products by setting up new test procedures. A step in this direction was done by the European Committee for Standardization to create a working group around smart textiles. Hopefully, more initiatives in this vein will be started in the near future to enhance the smart medical textile market.
For most of the developed countries such as China and the US, technical textiles contribute ~20% of the overall textile market, whereas in India technical textile accounts for ~12% of the overall textile market. The technical textile market is expected to rise to the similar levels driven by huge potential demand driven by rising health care sector and policy support by the government.
Furthermore, over FY13-16, the Meditech exports are expected to grow at a CAGR of 12% to reach INR8.7 billion in FY16. Out of the overall Meditech exports, surgical disposable exports are expected to grow at CAGR of 10% over FY13-16 to reach INR45.9 crores in FY16; surgical dressing will grow at 5% to reach INR383 crores inFY16.
The global Meditech industry is expected to reach the US $20.23 billion by 2022 from US$14.94 billion in 2014 The growth is primarily attributable to the rise in elderly population, ongoing technological advancements and increase in health consciousness.
Non-implantable products account for about 30% of the global medical textile industry on account of increasing incidence of injuries, rising prevalence of diabetes and obesity.The global sutures market was valued at US$2.80 billion in 2014 and is expected to reach US$3.59 billion by 2020, growing at a CAGR of 4.2% between 2014 and 2020. On the other hand, global hygiene product market will grow to US$78.9 billion, over 551 billion units, by 2018.
Hence, on the basis of all the research data it can be concluded that;
Scaffold might prove to be useful in near future in regenerating highly damaged bones and tissues if the experimentation with PEDOT:PSS is successful.
With an improvement in designs of SOCs along with the miniaturizing of sensors and actuators, viability and comfort of this system are on the rise. Thus, increasing the implementation of smart textile.