Three-dimensional bioprinting of gelatin methacryloyl (GelMA)

The three-dimensional (3D)bioprinting technology has progressed tremendously over the past decade.By controlling the size, shape,and architecture of the bioprinted constructs,3D bioprinting allows for the fabrication of tissue/organ-like constructs with strong structural-functional similarity with their in vivo counterparts at high fidelity.The bioink,a blend of biomaterials and living cells possessing both high biocompatibility and printability,is a critical component of bioprinting.In particular, gelatin methacryloyl (GelMA)has shown its potential as a viable bioink material due to its suitable biocompatibility and readily tunable physicochemical properties.Current GelMA-based bioinks and relevant bioprinting strategies for GelMA bioprinting are briefly reviewed.

Transient thermo-mechanical analysis for bimorph soft robot based on thermally responsive liquid crystal elastomers

Thermally responsive liquid crystal elastomers (LCEs) hold great promise in applications of soft robots and actuators because of the induced size and shape change with temperature. Experiments have successfully demonstrated that the LCE based bimorphs can be effective soft robots once integrated with soft sensors and thermal actuators. Here, we present an analytical transient thermo-mechanical model for a bimorph structure based soft robot, which consists of a strip of LCE and a thermal inert polymer actuated by an ultra-thin stretchable open-mesh shaped heater to mimic the unique locomotion behaviors of an inchworm. The coupled mechanical and thermal analysis based on the thermo-mechanical theory is carried out to underpin the transient bending behavior, and a systematic understanding is therefore achieved. The key analytical results reveal that the thickness and the modulus ratio of the LCE and the inert polymer layer dominate the transient bending deformation. The analytical results will not only render fundamental understanding of the actuation of bimorph structures, but also facilitate the rational design of soft robotics.

A flexible,multifunctional,optoelectronic anticounterfeiting device from high-performance organic light-emitting paper

As a primary anticounterfeiting technology,most paper anticounterfeiting devices take advantage of photoresponsive behaviors of certain security materials or structures,thus featuring low-security threshold,which has been a critical global issue.To incorporate optoelectronic devices into existing anticounterfeiting technology suggests a feasible avenue to address this challenge.Here we report a high-performance organic light-emitting paper-based flexible anticounterfeiting(FAC)device with multiple stimuli-responsiveness,including light,electricity,and their combination.Without sacrificing the preexisted security information on the paper,we fabricate FAC device in a facile,low-cost yet high-fidelity fashion by integrating patterned electro-responsive and photo-responsive organic emitters onto paper substrates.By introducing optical microcavities,the FAC device shows considerable color shift upon different viewing angle and applied voltage,which is easily discernible by naked eyes.Notably,the FAC device is bendable,unclonable,and durable(a half-lifetime over 4000 hours at 100 cd m^(−2)).

Flexible organic solar cells for biomedical devices

Organic solar cells(OSCs),particularly made based on solution processing methods,have made significant progress over the past decades through the concurrent evolution of organic photovoltaic materials and device engineering.Recently,high power conversion efficiencies around 18%and over 16%have been demonstrated in both rigid and flexible OSCs,respectively.While most of the OSC research has centered on efficiency and cost,their emerging and potential usages in many critical applications,particularly in biomedical fields have been rising.In this mini-review,we will briefly discuss the high-performance organic photovoltaic materials and the representative flexible OSCs to give a scope on the recent rapid development of OSCs.Besides,we will review some progress on the applications of OSCs in biomedical devices and integrated systems.The potential challenges associated with integrating OSCs for biomedical devices will be put forward.

Fully rubbery synaptic transistors made out of all-organic materials for elastic neurological electronic skin

Neurologic function implemented soft organic electronic skin holds promise for wide range of applications,such as skin prosthetics,neurorobot,bioelectronics,human-robotic interaction(HRI),etc.Here,we report the development of a fully rubbery synaptic transistor which consists of all-organic materials,which shows unique synaptic characteristics existing in biological synapses.These synaptic characteristics retained even under mechanical stretch by 30%.We further developed a neurological electronic skin in a fully rubbery format based on two mechanoreceptors(for synaptic potentiation or depression)of pressure-sensitive rubber and an all-organic synaptic transistor.By converting tactile signals into Morse Code,potentiation and depression of excitatory postsynaptic current(EPSC)signals allow the neurological electronic skin on a human forearm to communicate with a robotic hand.The collective studies on the materials,devices,and their characteristics revealed the fundamental aspects and applicability of the all-organic synaptic transistor and the neurological electronic skin.

Curvy surface conformal ultra-thin transfer printed Sioptoelectronic penetrating microprobe arrays

Penetrating neural probe arrays are powerful bio-integrated devices for studying basic neuroscience and applied neurophysiology,underlying neurological disorders,and understanding and regulating animal and human behavior.This paper presents a penetrating microprobe array constructed in thin and flexible fashion,which can be seamlessly integrated with the soft curvy substances.The function of the microprobes is enabled by transfer printed ultra-thin Si optoelectronics.As a proof-of-concept device,microprobe array with Si photodetector arrays are demonstrated and their capability of mapping the photo intensity in space are illustrated.The design strategies of utilizing thin polyimide based microprobes and supporting substrate,and employing the heterogeneously integrated thin optoelectronics are keys to accomplish such a device.The experimental and theoretical investigations illustrate the materials,manufacturing,mechanical and optoelectronic aspects of the device.While this paper primarily focuses on the device platform development,the associated materials,manufacturing technologies,and device design strategy are applicable to more complex and multi-functionalities in penetrating probe array-based neural interfaces and can also find potential utilities in a wide range of bio-integrated systems.

Soft and transient magnesium plasmonics for environmental and biomedical sensing

Due to its controlled reaction with water and biofluids, Mg as a dissolvable conductor has enabled the development of many transient electronic devices. In addition, Mg is a novel plasmonic material with high extinction efficiency but its transient optical properties have not been explored thoroughly. In this study for the first time, we exploit the transient and tunable plasmonic properties of Mg in environmental and biomedical sensor applications. We used soft nanoimprint lithography to fabricate flexible and large-area Mg plasmonic structures that can be applied on the human skin. Their resonance （or color） can be tuned in the visible range by gradual Mg dissolution in a water fluid or vapor-rich environment; these structures can be easily implemented as passive optical sensors without the need for complex electronic circuits or a power supply. We demonstrate the applications of our optical sensors in the accurate monitoring of environmental humidity and physiological detection of sweat loss on the human skin during exercise. Our devices could be used as decomposable/resorbable optical sensors and can help minimize long-term health effects and environmental risks associated with consumer device waste, which will lead to many new possibilities in transient photonic device applications.