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The various bioacoustics signals obtained with auscultation contain complex clinical information used as traditional biomarkers, however it is not widely used in clinical for long-term studies due to spatiotemporal limitations. Here, we developed a wearable stethoscope for skin-attachable, continuous and real-time auscultation using a lung sound monitoring patch (LSMP). The LSMP can monitor respiratory function through mobile app and classify normal and adventitious breathing by comparing the unique acoustic characteristics they produced. Heart and breathing sounds from humans can be distinguished from complex sound consisting of a mixture of the bioacoustic signal and external noise. The performance was further demonstrated with pediatric asthma and elderly chronic obstructive pulmonary disease (COPD) patients. We implemented a counting algorithm to identify wheezing events in real-time regardless of the respiratory cycle. As a result, the AI-based adventitious breathing event counter distinguished over 80% of events, especially wheezing events, in long-term clinical application.

Soft grippers that incorporate functional materials are important in the development of mechanically compliant and multifunctional interfaces for both sensing and stimulating soft objects and organisms. In particular, the capability for firm and delicate grasping of soft cells and organs without mechanical damage is essential to identify the condition of and monitor meaningful biosignals from objects. Here, we report a millimeter-scale soft gripper based on a shape memory polymer that enables manipulating a heavy object (payload-to-weight ratio up to 6400) and grasping organisms at the micro/milliscale. The silver nanowires and crack-based strain sensor embedded in this soft gripper enable simultaneous measurement of the temperature and pressure on grasped objects and offer temperature and mechanical stimuli for the grasped object. We validate our miniaturized soft gripper by demonstrating that it can grasp a snail egg while simultaneously applying a moderate temperature stimulation to induce hatching process and monitor the heart rate of a newborn snail. The results present the potential for widespread utility of soft grippers in the area of biomedical engineering, especially in the development of conditional or closed-loop interfacing with microscale biotissues and organisms.

As the safety of a human body is the main priority while interacting with robots, the field of tactile sensors has expanded for acquiring tactile information and ensuring safe human–robot interaction (HRI). Existing lightweight and thin tactile sensors exhibit high performance in detecting their surroundings. However, unexpected collisions caused by malfunctions or sudden external collisions can still cause injuries to rigid robots with thin tactile sensors. In this study, we present a sensitive balloon sensor for contact sensing and alleviating physical collisions over a large area of rigid robots. The balloon sensor is a pressure sensor composed of an inflatable body of low-density polyethylene (LDPE), and a highly sensitive and flexible strain sensor laminated onto it. The mechanical crack-based strain sensor with high sensitivity enables the detection of extremely small changes in the strain of the balloon. Adjusting the geometric parameters of the balloon allows for a large and easily customizable sensing area. The weight of the balloon sensor was approximately 2 g. The sensor is employed with a servo motor and detects a finger or a sheet of rolled paper gently touching it, without being damaged.

Animals such as the armadillo and pangolin have natural armor as a mechanical form of protection from predators. Among the several types of armor that exist in nature, structures composed of thin elastomeric substrates with overlapping hard scales can shield underlying soft tissues from physical impacts and localized stresses while maintaining a level of mechanical compliance necessary for natural motions. Here, we design and fabricate a class of artificial armor that derives inspiration from these natural systems. The optimization process involves systematic tests of several design candidates to assess their mechanical stability against different types of mechanical stresses. The resulting platforms provide highly effective protection layers for wearable electronic devices and soft robotic systems with little constraint on their functionality, as demonstrated with representative devices.

Inspired by the rolling mechanism of the proboscis of a butterfly, rollable electronics that can be rolled and unrolled to a great extent on demand are developed. Generally, electronic devices that are attached to various surfaces to acquire biosignals require mechanical flexibility and sufficient adhesive force. The rollable platform provides sufficient force that grips onto the entire target surface without destroying the target organ. To prove the versatility of our device not only in gripping and detecting biosignals from micro objects but also in performing a variety of functions, thin-film electronics including a heater, strain sensor and temperature sensor are constructed on the rollable platform, and it is confirmed that all the electronics operate normally in the rolled and unrolled states without breakdown. Then, micro bio-objects are gripped by using the rollable platform, and their tiny motions are successfully detected with the sensor on the platform. Furthermore, the detection of the pulse wave signals of swine under diverse experimental conditions is successfully conducted by rolling up the rollable system around the blood vessel of the swine, the result of which proves the feasibility of a rollable platform as a biomedical device. Rollable electronic devices inspired by butterflies have been fabricated by researchers in South Korea for biomedical applications. Bioelectronic devices can be attached to the body, either outside on the skin or inside on internal organs. They can then monitor and even help regulate the operation of the organ. Ensuring that bioelectronic components stay attached is tricky, particularly for tubular organs with a small radius of curvature, such as blood vessels. Gunhee Lee from the Seoul National University and co-workers constructed a thin-film electronic circuit that they could tightly roll and unroll on demand, in the same way a butterfly unfurls its proboscis, to grip the target organ with sufficient force. The viability of their device, which included a heater, strain and temperature sensor, was demonstrated by monitoring the femoral artery of a pig. Inspired by the rolling mechanism of the proboscis of a butterfly, a rollable electronics which can be rolled and unrolled on demand is developed. The rollable platform provides sufficient force which grips onto the entire target surface without destroying the target. Micro bio-objects are gripped by using the rollable platform and their tiny motions are successfully detected with the sensor on the platform. Furthermore, detecting pulse wave signals of the swine is successfully conducted by rolling up the rollable system around the blood vessel of swine, which result proves the feasibility of rollable platform as a biomedical device.

Among many flexible mechanosensors, a crack-based sensor inspired by a spider&rsquo, s slit organ has received considerable attention due to its great sensitivity compared to previous strain sensors. The sensor&rsquo, s limitation, however, lies on its vulnerability to stress concentration and the metal layers&rsquo, delamination. To address this issue of vulnerability, we used fluorinated ethylene propylene (FEP) as an encapsulation layer on both sides of the sensor. The excellent waterproof and chemical resistance capability of FEP may effectively protect the sensor from damage in water and chemicals while improving the durability against friction.

Measuring the foot plantar pressure has the potential to be an important tool in many areas such as enhancing sports performance, diagnosing diseases, and rehabilitation. In general, the plantar pressure sensor should have robustness, durability, and high repeatability, as it should measure the pressure due to body weight. Here, we present a novel insole foot plantar pressure sensor using a highly sensitive crack-based strain sensor. The sensor is made of elastomer, stainless steel, a crack-based sensor, and a 3D-printed frame. Insoles are made of elastomer with Shore A 40, which is used as part of the sensor, to distribute the load to the sensor. The 3D-printed frame and stainless steel prevent breakage of the crack-based sensor and enable elastic behavior. The sensor response is highly repeatable and shows excellent durability even after 20,000 cycles. We show that the insole pressure sensor can be used as a real-time monitoring system using the pressure visualization program.

In mechanical sensory systems, encapsulation is one of the crucial issues to take care of when it comes to protection of the systems from external damage. Recently, a new type of a mechanical strain sensor inspired by spider’s slit organ has been reported, which has incredibly high sensitivity, flexibility, wearability, and multifunctional sensing abilities. In spite of many of these advantages, the sensor is still vulnerable in harsh environments of liquids and/or high temperature, because it has heat-vulnerable polyethylene terephthalate (PET) substrate without any encapsulation layer. Here, we present a mechanical crack-based strain sensor with heat, water and saline solution resistance by alternating the substrate from polyester film to polyimide film and encapsulating the sensor with polyimide. We have demonstrated the ability of the encapsulated crack-based sensor against heat, water, saline solution damage through experiments. Our sensor exhibited reproducibility and durability with high sensitivity to strain (gauge factor above 10,000 at strain of two percent). These results show a new potential of the crack-based sensory system to be used as a wearable voice/motion/pulse sensing device and a high-temperature strain sensor.